Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND SYSTEM FOR STARTING AN
INTERNAL COMBUSTION ENGINE
CROSS-REFERENCE
[0001] The present application claims priority to United States
Provisional Patent
Application No. 62/458,882, filed February 14, 2017, the entirety of which is
incorporated
herein by reference. For purposes of the United States, the present
application is a
continuation-in-part of International Patent Application No.
PCT/IB2016/056824, filed
November 11, 2016, which claims priority from United States Provisional Patent
Application
No. 62/254,421, filed November 12, 2015, the entirety of which are
incorporated by
reference.
FIELD OF TECHNOLOGY
[0002] The present technology relates to a method and system for starting
an internal
combustion engine.
BACKGROUND
[0003] In order to start the internal combustion engine of small vehicles,
such as a
snowmobile, a recoil starter is sometimes provided. To start the engine, the
user pulls on a
rope of the recoil starter which causes the crankshaft of the engine to turn.
If the crankshaft
turns fast enough, the engine can be started. If not, the rope needs to be
pulled again until the
engine starts.
[0004] In order to facilitate the starting of the engine, some vehicles
have been provided
with an electric starting system. This system consists of an electric motor,
known as a starter,
which engages and turns a ring gear connected to the crankshaft via a BendixTM
mechanism,
when an ignition key is turned or a start button is pushed by the user. The
starter turns the
crankshaft fast enough to permit the starting of the engine, and once the
engine has started,
disengages the ring gear and is turned off. The vehicle has a battery to
supply electric current
to the starter in order to turn the crankshaft.
[0005] Although it is very convenient for the user, electric starting
systems of the type
described above have some drawbacks. The battery, the starter and their
associated
components add weight to the vehicle. As would be understood, additional
weight reduces
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the fuel efficiency of the vehicle and can affect handling of the vehicle. In
the case of
snowmobiles, this weight also makes it more difficult for the snowmobile to
ride on top of
snow. These electric starting systems also require additional assembly steps
when
manufacturing the vehicle and take up room inside the vehicle.
[0006] To recharge the battery and to provide the electric current
necessary to operate the
various components of the vehicle once the engine has started, an electrical
generator is
operatively connected to the crankshaft of the engine. As the crankshaft turns
the rotor of the
electrical generator, the generator generates electricity.
[0007] In recent years, some vehicles have been provided with motor-
generator units, also
called starter-generators, which replace the starter and the electrical
generator. The motor-
generator is operatively connected to the crankshaft in a manner similar to
the
aforementioned electrical generator. The motor-generator unit can be used as a
starter or as a
generator. By applying current to the motor-generator unit, the motor-
generator unit operates
as a starter and turns the crankshaft to enable starting of the engine. When
the motor-
generator is operated as a generator, the rotation of the crankshaft causes
the motor-generator
to generate electricity. As would be understood, the use of such systems
addresses some of
the deficiencies of starting systems using separate starters and electrical
generators.
[0008] In order to start the engine, the torque applied to the crankshaft
to make it turn has
to be sufficiently large to overcome the compression inside the engine's
cylinders resulting
from the pistons moving up in their respective cylinders as the crankshaft
rotates. In order to
provide this amount of torque, the motor-generator unit needs to be
sufficiently large to
properly operate as a starter.
[0009] Another problem relates to the duration of a starting sequence for
the internal
combustion engine, which should be as brief as possible.
[0010] A further problem concerns the control of the motor-generator. When
operating as
a starter, the motor-generator generally operates at low rotational speeds,
sufficient to allow
the onset of ignition in the internal combustion engine. This operation
requires the provision
of a certain voltage to the motor-generator by the electric starting system.
When operating as
a generator, the motor-generator provides electric power over a wide range of
rotational
speeds of the internal combustion engine, oftentimes far exceeding the
starting rotational
speed. Without specific voltage control solutions, the motor-generator
operating at high
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rotational speeds could generate voltages that far exceed the needs of the
various components
of the vehicle.
[0011] There is therefore a need for a method and system for starting an
internal
combustion engine that address at least some of the above inconveniences.
SUMMARY
[0012] It is an object of the present technology to ameliorate at least
some of the
inconveniences present in the prior art.
[0013] The present technology provides a system supporting an electrical
start procedure
for an internal combustion engine (ICE) and a method for electrical starting
the ICE that uses
an electric turning machine (ETM) connected to the crankshaft to start the
engine. The
method permits an electrical start of the engine using a power source that is
smaller and
lighter than conventional batteries. A sensor provides, to a controller a
reading of an absolute
angular position of a crankshaft of the ICE, or a reading of an absolute
angular position of a
component of the ICE that rotates in synchrony with the crankshaft. This
reading is available
when the ICE is stopped, at the onset of a start procedure, and when the ICE
is running.
Based on this reading, the controller knows the position of a piston of the
ICE. When the ICE
is stopped, the piston tends to be in a first predetermined position because
of a configuration
of exhaust ports in a cylinder where the piston is located. The controller
determines a first
level of torque that will bring the piston from the first predetermined
position to a second
predetermined position near a top dead center (TDC) position. At that time,
the controller
determines a second level of torque, greater than the second level of torque,
that will bring
the piston beyond the TDC position. Fuel injection in the cylinder and
ignition will take place
once the piston has passed the TDC position.
[0014] In a first aspect, the present technology provides a method for
starting an internal
combustion engine (ICE) having a crankshaft and an electric turning machine
(ETM)
operatively connected to the crankshaft. An absolute angular position of the
crankshaft is
determined, the absolute angular position of the crankshaft being related to
an angular
position of a rotor of the ETM. Electric power is delivered to the ETM at a
first level to rotate
the crankshaft. Electric power is delivered to the ETM at a second level
greater than the first
level when the rotor of the ETM reaches a predetermined angular position.
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[0015] In some implementations of the present technology, the method
further comprises
calculating the first level of electric power delivery so that the ETM
generates sufficient
torque to rotate the crankshaft until the rotor reaches the predetermined
angular position; and
calculating the second level of electric power delivery so that the ETM
generates sufficient
.. torque to rotate the crankshaft beyond the predetermined angular position
of the rotor.
[0016] In some implementations of the present technology, calculating the
first level of
electric power delivery comprises using a vector control of the delivery of
electric power at
the first level based on a predetermination of the sufficient torque to rotate
the crankshaft
until the rotor reaches the predetermined angular position; and calculating
the second level of
.. electric power delivery comprises using a vector control of the delivery of
electric power at
the second level based on a predetermination of the sufficient torque to
rotate the crankshaft
beyond the predetermined angular position of the rotor.
[0017] In some implementations of the present technology, the method
further comprises
energizing an absolute position sensor used to determine the absolute angular
position of the
.. crankshaft when the ICE is stopped.
[0018] In some implementations of the present technology, the method
further comprises
energizing the absolute position sensor when the crankshaft is rotating.
[0019] In some implementations of the present technology, the method
further comprises
gradually increasing the delivery of electric power to the ETM from an initial
level to the first
level before delivering electric power to the ETM at the second level.
[0020] In some implementations of the present technology, the absolute
angular position
of the crankshaft is further related to a position of a piston in a combustion
chamber of the
ICE in relation to a top dead center (TDC) position of the piston.
[0021] In some implementations of the present technology, delivering
electric power to
the ETM at the second level starts when the piston reaches a predetermined
position before
the TDC position; and the method further comprises injecting fuel in the
combustion chamber
of the ICE when the piston passes the TDC position a first time and igniting
the fuel in the
combustion chamber.
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[0022] In some implementations of the present technology, the method
further comprises
determining the first level of the electric power delivered to the ETM based
on an initial
angular position of the crankshaft.
[0023] In some implementations of the present technology, the initial
angular position of
5 the crankshaft is a position of the crankshaft when the ICE is stopped.
[0024] In some implementations of the present technology, the initial
angular position is
in a range between 80 and 100 degrees before the TDC position.
[0025] In some implementations of the present technology, delivering the
electric power
to the ETM before the piston reaches the predetermined position before the TDC
position
causes gases to be expelled from the combustion chamber.
[0026] In some implementations of the present technology, the
predetermined position
before the TDC position is determined according to a configuration of exhaust
ports of the
ICE.
[0027] In some implementations of the present technology, the
predetermined position
before the TDC position in a range between 0 and 50 degrees before the TDC
position.
[0028] In some implementations of the present technology, the method
further comprises
terminating the delivery of electric power to the ETM after starting the ICE.
[0029] In some implementations of the present technology, the delivery of
electric power
to the ETM is terminated when a rotational speed of the crankshaft reaches a
minimum
threshold.
[0030] In some implementations of the present technology, the fuel is
ignited before the
piston passes the TDC position a second time.
[0031] In some implementations of the present technology, the fuel is
injected in the
combustion chamber when the position of the piston passes a range between 3
degrees before
the TDC position and 7 degrees after the TDC position.
[0032] In some implementations of the present technology, the fuel is
ignited when the
position of the piston is in a range between 0 and 12 degrees after the TDC
position, ignition
of the fuel taking place after injection of the fuel.
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[0033] In some implementations of the present technology, ignition takes
place before the
piston reaches the top of an exhaust port in the combustion chamber of the ICE
[0034] In some implementations of the present technology, the first level
of electric power
delivery is calculated so that the ETM generates sufficient torque to rotate
the crankshaft until
the piston reaches the predetermined position before the TDC position; and the
second level
of electric power delivery is calculated so that the ETM generates sufficient
torque to cause
the piston to move beyond the TDC position.
[0035] In some implementations of the present technology, determining the
absolute
angular position of the crankshaft comprises sensing the absolute angular
position of the
crankshaft.
[0036] In some implementations of the present technology, the method
further comprises
sensing n absolute angular position of a component of the ICE that rotates in
synchrony with
the crankshaft, wherein the component of the ICE that rotates in synchrony
with the
crankshaft is selected from the rotor of the ETM, a fuel pump, an oil pump, a
water pump, a
camshaft, and a balance shaft; and calculating the absolute angular position
of the crankshaft
based on the sensed absolute angular position of the component of the ICE that
rotates in
synchrony with the crankshaft.
[0037] In a second aspect, the present technology provides a system for
starting an
internal combustion engine (ICE) having a crankshaft. The system comprises a
power source,
an electric turning machine (ETM) adapted for being mounted to the crankshaft,
an absolute
position sensor adapted for providing an indication of an absolute angular
position of the
crankshaft, the absolute angular position of the crankshaft being related to
an angular position
of a rotor of the ETM, and an engine control unit (ECU) operatively connected
to the
absolute position sensor. The ECU is adapted for determining the absolute
angular position of
the crankshaft based on the indication provided by the absolute position
sensor. The ECU is
further adapted for controlling a delivery of electric power from the power
source to the ETM
at a first level to rotate the crankshaft and at a second level greater than
the first level when
the rotor of the ETM reaches a predetermined angular position.
[0038] In some implementations of the present technology, the ECU is
further adapted for:
calculating the first level of electric power delivery so that the ETM
generates sufficient
torque to rotate the crankshaft until the rotor reaches the predetermined
angular position; and
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calculating the second level of electric power delivery so that the ETM
generates sufficient
torque to rotate the crankshaft beyond the predetermined angular position of
the rotor.
[0039] In some implementations of the present technology, the ECU
implements a vector
control of the delivery of electric power at the first level based on a
predetermination of the
sufficient torque to rotate the crankshaft until the rotor reaches the
predetermined angular
position; and the ECU implements a vector control of the delivery of electric
power at the
second level based on a predetermination of the sufficient torque to rotate
the crankshaft
beyond the predetermined angular position of the rotor.
[0040] In some implementations of the present technology, the absolute
angular position
of the crankshaft is further related to a position of a piston in a combustion
chamber of the
ICE in relation to a top dead center (TDC) position of the piston.
[0041] In some implementations of the present technology, the delivery of
electric power
from the power source to the ETM at the second level starts when the piston
reaches a
predetermined position before the TDC position; and the ECU is further adapted
for
controlling an injection of fuel in the combustion chamber of the ICE when the
piston passes
the TDC position a first time, and for controlling ignition of the fuel in the
combustion
chamber.
[0042] In some implementations of the present technology, the ETM is
adapted for being
coaxially mounted to the crankshaft.
[0043] In some implementations of the present technology, the absolute
position sensor is
adapted for sensing the absolute angular position of the crankshaft.
[0044] In some implementations of the present technology, the absolute
position sensor is
adapted for sensing an angular position of a component of the ICE that rotates
in synchrony
with the crankshaft, wherein the component of the ICE that rotates in
synchrony with the
crankshaft is selected from the rotor of the ETM, a fuel pump, an oil pump, a
water pump, a
camshaft, and a balance shaft; and the ECU is adapted for calculating the
absolute angular
position of the crankshaft based on the sensed absolute angular position of
the component of
the ICE that rotates in synchrony with the crankshaft and based on a
mechanical relationship
between the crankshaft of the component of the ICE that rotates in synchrony
with the
crankshaft.
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[0045] In some implementations of the present technology, the absolute
position sensor is
permanently connected to the power source.
[0046] In some implementations of the present technology, the absolute
position sensor is
energized by the power source at the onset of a start procedure for the ICE.
[0047] In a third aspect, the present technology provides an internal
combustion engine
(ICE) comprising a crankshaft, a first cylinder, a cylinder head connected to
the first cylinder,
a piston operatively connected to the crankshaft and disposed in the first
cylinder. The first
cylinder, the cylinder head and a crown of the first piston define a first
variable volume
combustion chamber therebetween. The ICE further comprises a system for
starting the ICE.
The system comprises a power source, an electric turning machine (ETM) adapted
for being
mounted to the crankshaft, an absolute position sensor adapted for providing
an indication of
an absolute angular position of the crankshaft, the absolute angular position
of the crankshaft
being related to an angular position of a rotor of the ETM, and an engine
control unit (ECU)
operatively connected to the absolute position sensor. The ECU is adapted for
determining
the absolute angular position of the crankshaft based on the indication
provided by the
absolute position sensor. The ECU is further adapted for controlling a
delivery of electric
power from the power source to the ETM at a first level to rotate the
crankshaft and at a
second level greater than the first level when the rotor of the ETM reaches a
predetermined
angular position. The absolute angular position of the crankshaft is related
to a position of the
first piston in the first combustion chamber.
[0048] In some implementations of the present technology, the ICE further
comprises: a
direct fuel injector operatively connected to the ECU; and an ignition system
operatively
connected to the ECU; wherein the ECU is adapted for causing the direct fuel
injector to
inject the fuel in the first combustion chamber and for causing the ignition
system to ignite
the fuel.
[0049] In some implementations of the present technology, the ICE further
comprises: a
second cylinder; and a second piston operatively connected to the crankshaft
and disposed in
the second cylinder, the second cylinder, the cylinder head and a crown of the
second piston
defining a second variable volume combustion chamber therebetween; wherein
when the first
piston compresses gases in the first combustion chamber, the second piston
expands the
volume of the second combustion chamber.
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[0050] In a fourth aspect, the present technology provides a method for
starting an internal
combustion engine (ICE) having a crankshaft and an electric turning machine
(ETM)
operatively connected to the crankshaft. An absolute position sensor adapted
for providing an
indication of an angular position of a rotor of the ETM is energized. A
current is applied to
.. the ETM to generate a torque sufficient to rotate the crankshaft.
[0051] In some implementations of the present technology, the absolute
position sensor
provides the indication of the angular position of the rotor of the ETM in
signals sent to a
controller; and the controller calculates on an ongoing basis the actual
angular position of the
rotor of the ETM based on the signals from the absolute position sensor.
[0052] In some implementations of the present technology, applying a
current to the ETM
further comprises: initially applying a first current to the ETM; and
subsequently applying to
the ETM a second current greater than the first current when the angular
position of the rotor
of the ETM passes beyond a predetermined angular position.
[0053] In some implementations of the present technology, the method
further comprises
receiving at a controller a start command for the ICE.
[0054] In some implementations of the present technology, the method
further comprises:
determining an initial angular position of the rotor of the ETM; and
determining a first
amount of torque to be supplied by the ETM to the crankshaft based in part on
the initial
angular position of the rotor of the ETM.
[0055] In some implementations of the present technology, the method
further comprises:
determining a second angular position of the rotor of the ETM, the second
angular position
indicating that the rotor of the ETM has passed a first predetermined angular
position; and
determining a second amount of torque to be supplied by the ETM to the
crankshaft based in
part on the second angular position of the rotor of the ETM, the second amount
of torque
being greater than the first amount of torque.
[0056] In some implementations of the present technology, the method
further comprises:
determining a third angular position of the rotor of the ETM, the third
angular position
indicating that the rotor of the ETM has passed a second predetermined angular
position, the
second predetermined angular position being a top dead center (TDC) position
of a piston
within a combustion chamber; and injecting fuel in the combustion chamber of
the ICE.
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[0057] In some implementations of the present technology, the method
further comprises:
determining a fourth angular position of the rotor of the ETM, the fourth
angular position
indicating that the rotor of the ETM has passed a third predetermined angular
position, the
third predetermined angular position being after the second predetermined
angular position;
5 and igniting the fuel in the combustion chamber of the ICE.
[0058] In some implementations of the present technology, the fourth
angular position is
less than 110 degrees of rotation of the crankshaft beyond the initial angular
position.
[0059] In some implementations of the present technology, the fourth
angular position is
selected so that ignition takes place before opening of an exhaust port in the
combustion
10 chamber of the ICE.
[0060] In a fifth aspect, the present technology provides an internal
combustion engine
(ICE) comprising a crankshaft, a cylinder head defining in part a variable
combustion
chamber of the ICE, a direct fuel injector mounted on the cylinder head, a
power source, an
electric turning machine (ETM) adapted for rotating the crankshaft, an
absolute position
sensor adapted for providing an indication of an angular position of a rotor
of the ETM and
an engine control unit (ECU) operatively connected to the absolute position
sensor. The ECU
is adapted for vector controlling a delivery of electric power from the power
source to the
ETM based on the angular position of the rotor of the ETM and for causing the
direct fuel
injector to inject fuel directly in the combustion chamber at a time selected
based on the
angular position reached by the rotor of the ETM.
[0061] In some implementations of the present technology, the ECU causes
the delivery of
electric power from the power source to the ETM to generate a first level of
torque until the
rotor of the ETM reaches a first predetermined position and then to generate a
second level of
torque greater than the first level of torque as the rotor of the ETM rotates
beyond the first
predetermined position.
[0062] In some implementations of the present technology, the ECU causes
the direct fuel
injector to inject fuel directly in the combustion chamber after the ETM has
reached the first
determined position.
[0063] In some implementations of the present technology, the absolute
angular position
of the rotor of the ETM is related to a position of a piston in the combustion
chamber,
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injection of the fuel taking place when the piston passes at a top dead center
position within
the combustion chamber.
[0064] In some implementations of the present technology, the ECU causes
an ignition of
the fuel after injection of the fuel.
[0065] In a sixth aspect, the present technology provides a method for
controlling delivery
of electric power between a power source and an electric turning machine
(ETM). A start
signal is applied to a start-up power electronic switch to cause turning on of
the start-up
power electronic switch and to allow delivery of electric power from the power
source to the
ETM via the start-up power electronic switch. A recharge signal is applied to
a run-time
power electronic switch to cause turning on of the run-time power electronic
switch and to
allow delivery of electric power from the ETM to the power source via the run-
time power
electronic switch.
[0066] In some implementations of the present technology, the method
further comprises
ceasing application of the start signal to the start-up power electronic
switch when applying
the recharge signal to the run-time power electronic switch.
[0067] In some implementations of the present technology, turning on of
the start-up
power electronic switch further comprises repeatedly turning on and off the
start-up power
electronic switch to limit the delivery of electric power from the power
source to the ETM.
[0068] In some implementations of the present technology, the start
signal is repeatedly
.. applied and released to cause repeatedly turning on and off the start-up
power electronic
switch.
[0069] In some implementations of the present technology, the start
signal is varied
according to a pulse width modulation mode.
[0070] In some implementations of the present technology, the method
further comprises
providing a current limiting circuit connected in series with the run-time
power electronic
switch to limit delivery of electric power from the ETM to the power source.
[0071] In some implementations of the present technology, the method
further comprises,
before applying the start signal to the start-up power electronic switch,
applying and then
releasing an initiation signal to the run-time power electronic switch
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[0072] In some implementations of the present technology, the start
signal is applied to
the start-up power electronic switch via a first driver and the recharge
signal is applied to the
run-time power electronic switch via a second driver.
[0073] In a seventh aspect, the present technology provides a circuit
comprising a
discharging circuit and a charging circuit. The discharging circuit comprises
a start-up power
electronic switch adapted for allowing delivery of electric power from a power
source to an
electric turning machine (ETM) via the start-up power electronic switch when
the start-up
power electronic switch is turned on. The charging circuit comprises a run-
time power
electronic switch adapted for allowing delivery of electric power from the ETM
to the power
source via the run-time power electronic switch when the run-time power
electronic switch is
turned on.
[0074] In some implementations of the present technology, the discharging
circuit further
comprises a first driver adapted for receiving a start signal and to forward
the start signal to
the start-up power electronic switch; and the charging circuit further
comprises a second
driver adapted for receiving a recharge signal and to forward the recharge
signal to the run-
time power electronic switch.
[0075] In some implementations of the present technology, the circuit
further comprises a
control unit adapted for applying the start signal to the first driver and for
applying the
recharge signal to the second driver.
[0076] In some implementations of the present technology, the control unit
is further
adapted for ceasing application of the start signal to the start-up power
electronic switch
when applying the recharge signal to the run-time power electronic switch.
[0077] In some implementations of the present technology, the control
unit is further
adapted for repeatedly applying and releasing the start signal to the first
driver to limit the
delivery of electric power from the power source to the ETM.
[0078] In some implementations of the present technology, the control
unit is further
adapted for varying the start signal according to a pulse width modulation
mode.
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[0079] In some implementations of the present technology, the charging
circuit further
comprises a current limiting circuit connected in series with the run-time
power electronic
switch and adapted for limiting delivery of electric power from the ETM to the
power source.
[0080] In some implementations of the present technology, the control
unit is further
adapted for applying and then releasing an initiation signal to the run-time
power electronic
switch before applying the start signal to the start-up power electronic
switch.
[0081] Additional and/or alternative features, aspects and advantages of
implementations
of the present technology will become apparent from the following description,
the
accompanying drawings and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0082] For a better understanding of the present technology, as well as
other aspects and
further features thereof, reference is made to the following description which
is to be used in
conjunction with the accompanying drawings, where:
[0083] Figure 1 is a right side perspective view of a snowmobile;
[0084] Figure 2 is a perspective view taken from a front, left side of an
internal
combustion engine of the snowmobile of Figure 1;
[0085] Figure 3A is a rear elevation view of the engine of Figure 2;
[0086] Figure 3B is a rear elevation view of another internal combustion
engine that may
be installed in the snowmobile of Figure 1;
[0087] Figure 4A is a cross-sectional view of the engine of Figure 2 taken
through line 4-4
of Figure 3, showing a piston at its top dead center position;
[0088] Figure 4B is a cross-sectional view of the engine of Figure 3B,
showing a piston in
its bottom dead center position;
[0089] Figure 4C is another view of the engine of Figure 3B, showing the
location of a
water pump;
[0090] Figure 5 is a cross-sectional view of the engine of Figure 2 taken
through line 5-5
of Figure 4A with a drive pulley of a CVT mounted on a crankshaft of the
engine;
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[0091] Figure 6 is a schematic diagram of components of a control system
of the engine of
Figure 2;
[0092] Figure 7 is a block diagram of a dual-strategy control system for
delivery of
electric power between the capacitance and the electric turning machine (ETM)
of Figure 6;
[0093] Figure 8 is a block diagram of an energy management circuit for the
capacitance of
Figure 6;
[0094] Figure 9 is a logic diagram of a method for starting the engine of
Figure 2
according to an implementation;
[0095] Figure 10 is a timing diagram showing an example of variations of
an engine
resistive torque as a function of time along with corresponding engine
rotational speed
variations;
[0096] Figure 11 is a logic diagram of a method for starting the engine
of Figure 2
according to another implementation;
[0097] Figure 12 is a circuit diagram showing connections between the
inverter, the
capacitance and the motor-generator of Figure 6;
[0098] Figure 13 is a block diagram of a typical implementation of a
vector control drive;
[0099] Figure 14 is a block diagram of an electric system according to an
implementation
of the present technology;
[00100] Figure 15 is a timing diagram showing an example of a sequence for
changing the
control strategy for the delivery of electric power between the capacitance
and the electric
turning machine (ETM) along with corresponding engine rotational speed
variations;
[00101] Figure 16 is another timing diagram showing an example of an impact of
the
control strategies on a current exchanged between the capacitance and the ETM
and on a
system voltage;
[00102] Figure 17 is yet another timing diagram showing an example of a
variation of
torque applied to the ETM during the first control strategy;
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[00103] Figure 18 is a sequence diagram showing operations of a method for
starting an
internal combustion engine; and
[00104] Figure 19 is a sequence diagram showing operations of a method for
controlling
delivery of electric power between a power source and the ETM.
5 DETAILED DESCRIPTION
[00105] The method and system for starting an internal combustion engine (ICE)
and the
method and system for an assisted start of the ICE will be described with
respect to a
snowmobile 10. However, it is contemplated that the method and system could be
used in
other vehicles, such as, but not limited to, on-road vehicles, off-road
vehicles, a motorcycle, a
10 scooter, a three-wheel road vehicle, a boat powered by an outboard
engine or an inboard
engine, and an all-terrain vehicle (ATV). It is also contemplated that the
method and system
could be used in devices other than vehicles that have an internal combustion
engine such as
a generator. The method and system will also be described with respect to a
two-stroke,
inline, two-cylinder internal combustion engine (ICE) 24. However, it is
contemplated that
15 the method and system could be used with an internal combustion engine
having one or more
cylinders and, in the case of multi-cylinder engines, having an inline or
other configuration,
such as a V-type engine as well as 4-stroke engines.
Vehicle
[00106] Turning now to Figure 1, a snowmobile 10 includes a forward end 12 and
a
rearward end 14 that are defined consistently with a forward travel direction
of the
snowmobile 10. The snowmobile 10 includes a frame 16 that has a tunnel 18, an
engine
cradle portion 20 and a front suspension assembly portion 22. The tunnel 18
consists of one
or more pieces of sheet metal arranged to form an inverted U-shape that is
connected at the
front to the engine cradle portion 20 and extends rearward therefrom along the
longitudinal
axis 23. An ICE 24 (schematically illustrated in Figure 1) is carried by the
engine cradle
portion 20 of the frame 16. The ICE 24 is described in greater detail below.
Two skis 26 are
positioned at the forward end 12 of the snowmobile 10 and are attached to the
front
suspension assembly portion 22 of the frame 16 through a front suspension
assembly 28. The
front suspension assembly 28 includes shock absorber assemblies 29, ski legs
30, and
supporting arms 32. Ball joints and steering rods (not shown) operatively
connect the skis 26
to a steering column 34. A steering device in the form of handlebar 36 is
attached to the
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upper end of the steering column 34 to allow a driver to rotate the ski legs
30 and thus the
skis 26, in order to steer the snowmobile 10.
[00107] An endless drive track 38 is disposed generally under the tunnel 18
and is
operatively connected to the ICE 24 through a CVT 40 (schematically
illustrated by broken
lines in Figure 1) which will be described in greater detail below. The
endless drive track 38
is driven to run about a rear suspension assembly 42 for propulsion of the
snowmobile 10.
The rear suspension assembly 42 includes a pair of slide rails 44 in sliding
contact with the
endless drive track 38. The rear suspension assembly 42 also includes a
plurality of shock
absorbers 46 which may further include coil springs (not shown) surrounding
one or more of
the shock absorbers 46. Suspension arms 48 and 50 are provided to attach the
slide rails 44 to
the frame 16. A plurality of idler wheels 52 are also provided in the rear
suspension assembly
42. Other types and geometries of rear suspension assemblies are also
contemplated.
[00108] At the forward end 12 of the snowmobile 10, fairings 54 enclose the
ICE 24 and
the CVT 40, thereby providing an external shell that protects the ICE 24 and
the CVT 40.
The fairings 54 include a hood and one or more side panels that can be opened
to allow
access to the ICE 24 and the CVT 40 when this is required, for example, for
inspection or
maintenance of the ICE 24 and/or the CVT 40. A windshield 56 is connected to
the fairings
54 near the forward end 12 of the snowmobile 10. Alternatively the windshield
56 could be
connected directly to the handlebar 36. The windshield 56 acts as a wind
screen to lessen the
force of the air on the driver while the snowmobile 10 is moving forward.
[00109] A straddle-type seat 58 is positioned over the tunnel 18. Two
footrests 60 are
positioned on opposite sides of the snowmobile 10 below the seat 58 to
accommodate the
driver's feet.
Internal combustion engine
[00110] Turning now to Figures 2 to 5, the ICE 24 and the CVT 40 will be
described. One
version of the ICE 24 is shown on Figures 2, 3A, 4A and 5 and another version
of the ICE 24
is shown on Figures 3B, 4B and 4C. Both versions of the ICE 24 are equivalent
and
interchangeable in the context of the present disclosure. The ICE 24 operates
on the two-
stroke principle. The ICE 24 has a crankshaft 100 that rotates about a
horizontally disposed
axis that extends generally transversely to the longitudinal axis 23 of the
snowmobile 10. The
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crankshaft drives the CVT 40 for transmitting torque to the endless drive
track 38 for
propulsion of the snowmobile 10.
[00111] The CVT 40 includes a drive pulley 62 coupled to the crankshaft 100 to
rotate with
the crankshaft 100 and a driven pulley (not shown) coupled to one end of a
transversely
mounted jackshaft (not shown) that is supported on the frame 16 through
bearings. The
opposite end of the transversely mounted jackshaft is connected to the input
member of a
reduction drive (not shown) and the output member of the reduction drive is
connected to a
drive axle (not shown) carrying sprocket wheels (not shown) that form a
driving connection
with the drive track 38.
[00112] The drive pulley 62 of the CVT 40 includes a pair of opposed
frustoconical belt
drive sheaves 64 and 66 between which a drive belt (not shown) is located. The
drive belt is
made of rubber, but it is contemplated that it could be made of metal linkages
or of a
polymer. The drive pulley 62 will be described in greater detail below. The
driven pulley
includes a pair of frustoconical belt drive sheaves between which the drive
belt is located.
The drive belt is looped around both the drive pulley 62 and the driven
pulley. The torque
being transmitted to the driven pulley provides the necessary clamping force
on the drive belt
through its torque sensitive mechanical device in order to efficiently
transfer torque to the
other powertrain components.
[00113] As discussed above, the drive pulley 62 includes a pair of opposed
frustoconical
belt drive sheaves 64 and 66 as can be seen in Figure 5. Both sheaves 64 and
66 rotate
together with the crankshaft 100. The sheave 64 is fixed in an axial direction
relative to the
crankshaft 100, and is therefore referred to as the fixed sheave 64. The fixed
sheave 64 is also
rotationally fixed relative to the crankshaft 100. The sheave 66 can move
toward or away
from the fixed sheave 64 in the axial direction of the crankshaft 100 in order
to change the
drive ratio of the CVT 40, and is therefore referred to as the movable sheave
66. As can be
seen in Figure 5, the fixed sheave 64 is disposed between the movable sheave
66 and the ICE
24.
[00114] The fixed sheave 64 is mounted on a fixed sheave shaft 68. The fixed
sheave 64 is
press-fitted on the fixed sheave shaft 68 such that the fixed sheave 64
rotates with the fixed
sheave shaft 68. It is contemplated that the fixed sheave 64 could be
connected to the fixed
sheave shaft 68 in other known manners to make the fixed sheave 64
rotationally and axially
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fixed relative to the fixed sheave shaft 68. As can be seen in Figure 5, the
fixed sheave shaft
68 is hollow and has a tapered hollow portion. The tapered hollow portion
receives the end of
the crankshaft 100 therein to transmit torque from the ICE 24 to the drive
pulley 62. A
fastener 70 is inserted in the outer end (i.e. the left side with respect to
Figure 5) of the drive
pulley 62, inside the fixed sheave shaft 68, and screwed into the end of the
crankshaft 100 to
prevent axial displacement of the fixed sheave shaft 68 relative to the
crankshaft 100. It is
contemplated that the fixed sheave shaft 68 could be connected to the
crankshaft 100 in other
known manners to make the fixed sheave shaft 68 rotationally and axially fixed
relative to the
crankshaft 100. It is also contemplated that the crankshaft 100 could be the
fixed sheave shaft
68.
[00115] A cap 72 is taper-fitted in the outer end of the fixed sheave shaft
68. The fastener
70 is also inserted through the cap 72 to connect the cap 72 to the fixed
sheave shaft 68. It is
contemplated that the cap 72 could be connected to the fixed sheave shaft 68
by other means.
The radially outer portion of the cap 72 forms a ring 74. An annular rubber
damper 76 is
connected to the ring 74. Another ring 78 is connected to the rubber damper 76
such that the
rubber damper 76 is disposed between the rings 74, 78. In the present
implementation, the
rubber damper 76 is vulcanized to the rings 74, 78, but it is contemplated
that they could be
connected to each other by other means such as by using an adhesive for
example. It is also
contemplated that the damper 76 could be made of a material other than rubber.
[00116] A spider 80 is disposed around the fixed sheave shaft 68 and axially
between the
ring 78 and the movable sheave 66. The spider 80 is axially fixed relative to
the fixed sheave
64. Apertures (not shown) are formed in the ring 74, the damper 76, and the
ring 78.
Fasteners (not shown) are inserted through the apertures in the ring 74, the
damper 76, the
ring 78 and the spider 80 to fasten the ring 78 to the spider 80. As a result,
torque is
transferred between the fixed sheave shaft 68 and the spider 80 via the cap
72, the rubber
damper 76 and the ring 78. The damper 76 dampens the torque variations from
the fixed
sheave shaft 68 resulting from the combustion events in the ICE 24. The spider
80 therefore
rotates with the fixed sheave shaft 68.
[00117] A movable sheave shaft 82 is disposed around the fixed sheave shaft
68. The
movable sheave 66 is press-fitted on the movable sheave shaft 82 such that the
movable
sheave 66 rotates and moves axially with the movable sheave shaft 82. It is
contemplated that
the movable sheave 66 could be connected to the movable sheave shaft 82 in
other known
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manners to make the movable sheave 66 rotationally and axially fixed relative
to the shaft 82.
It is also contemplated that the movable sheave 66 and the movable sheave
shaft 82 could be
integrally formed.
[00118] To transmit torque from the spider 80 to the movable sheave 104, a
torque transfer
assembly consisting of three roller assemblies 84 connected to the movable
sheave 66 is
provided. The roller assemblies 84 engage the spider 80 so as to permit low
friction axial
displacement of the movable sheave 66 relative to the spider 80 and to
eliminate, or at least
minimize, rotation of the movable sheave 66 relative to the spider 80. As
described above,
torque is transferred from the fixed sheave 64 to the spider 80 via the damper
76. The spider
80 engages the roller assemblies 84 which transfer the torque to the movable
sheave 66 with
no, or very little, backlash. As such, the spider 80 is considered to be
rotationally fixed
relative to the movable sheave 66. It is contemplated that in some
implementations, the
torque transfer assembly could have more or less than three roller assemblies
84.
[00119] As can be seen in Figure 5, a biasing member in the form of a coil
spring 86 is
disposed inside a cavity 88 defined radially between the movable sheave shaft
82 and the
spider 80. As the movable sheave 66 and the movable sheave shaft 82 move
axially toward
the fixed sheave 64, the spring 86 gets compressed. The spring 86 biases the
movable sheave
66 and the movable sheave shaft 82 away from the fixed sheave 64 toward their
position
shown in Figure 5. It is contemplated that, in some implementations, the
movable sheave 66
could be biased away from the fixed sheave 64 by mechanisms other than the
spring 86.
[00120] The spider 80 has three arms 90 disposed at 120 degrees from each
other. Three
rollers 92 are rotatably connected to the three arms 90 of the spider 80.
Three centrifugal
actuators 94 are pivotally connected to three brackets (not shown) formed by
the movable
sheave 66. Each roller 92 is aligned with a corresponding one of the
centrifugal actuators 94.
Since the spider 80 and the movable sheave 66 are rotationally fixed relative
to each other,
the rollers 92 remain aligned with their corresponding centrifugal actuators
94 when the
shafts 68, 82 rotate. The centrifugal actuators 94 are disposed at 120 degrees
from each other.
The centrifugal actuators 94 and the roller assemblies 84 are arranged in an
alternating
arrangement and are disposed at 60 degrees from each other. It is contemplated
that the
rollers 92 could be pivotally connected to the brackets of the movable sheave
66 and that the
centrifugal actuators 94 could be connected to the arms 90 of the spider 80.
It is also
contemplated that there could be more or less than three centrifugal actuators
94, in which
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case there would be a corresponding number of arms 90, rollers 92 and brackets
of the
movable sheave. It is also contemplated that the rollers 92 could be omitted
and replaced with
surfaces against which the centrifugal actuators 94 can slide as they pivot.
[00121] In the present implementation, each centrifugal actuator 94 includes
an arm 96 that
5 pivots about an axle 98 connected to its respective bracket of the
movable sheave 66. The
position of the arms 96 relative to their axles 98 can be adjusted. It is
contemplated that the
position of the arms 96 relative to their axles 98 could not be adjustable.
Additional detail
regarding centrifugal actuators of the type of the centrifugal actuator 94 can
be found in
International Patent Publication No. W02013/032463 A2, published March 7,
2013, the
10 entirety of which is incorporated herein by reference.
[00122] The above description of the drive pulley 62 corresponds to one
contemplated
implementation of a drive pulley that can be used with the ICE 24. Additional
detail
regarding drive pulleys of the type of the drive pulley 62 can be found in
International Patent
Publication No. WO 2015/151032 Al, published on October 8, 2015, the entirety
of which is
15 incorporated herein by reference. It is contemplated that other types of
drive pulleys could be
used.
[00123] The ICE 24 has a crankcase 102 housing a portion of the crankshaft
100. As can be
seen in Figures 2, 3 and 5, the crankshaft 100 protrudes from the crankcase
102. It is
contemplated that the crankshaft 100 could drive an output shaft connected
directly to the end
20 of the crankshaft 100 or offset from the crankshaft 100 and driven by
driving means such as
gears in order to drive the drive pulley 62. It is also contemplated that the
crankshaft 100
could drive, using gears for example, a counterbalance shaft housed in part in
the crankcase
102 and that the drive pulley 62 could be connected to the counterbalance
shaft, in which
case, the crankshaft 100 does not have to protrude from the crankcase 102 for
this purpose. A
cylinder block 104 is disposed on top of and connected to the crankcase 102.
The cylinder
block 104 as shown defines two cylinders 106A, 106B (Figure 5). A cylinder
head 108 is
disposed on top of and is connected to the cylinder block 104.
[00124] As best seen in Figure 5, the crankshaft 100 is supported in the
crankcase 102 by
bearings 110. The crankshaft 100 has two crank pins 112A, 112B. In the
illustrated
implementation where the two cylinders 106A, 106B are disposed in line, the
crank pins
112A, 112B are provided at 180 degrees from each other. It is contemplated
that the crank
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pins 112A, 112B could be provided at other angles from each other to account
for other
cylinder arrangements, such as in a V-type engine. A connecting rod 114A is
connected to
the crank pin 112A at one end and to a piston 116A via a piston pin 118A at
the other end. As
can be seen, the piston 116A has at least one ring 117A below its crown and is
disposed in
the cylinder 106A. Similarly, a connecting rod 114B is connected to the crank
pin 112B at
one end and to a piston 116B via a piston pin 118B at the other end. As can be
seen, the
piston 116B has at least one ring 117B below its crown and is disposed in the
cylinder 106B.
Rotation of the crankshaft 100 causes the pistons 116A, 116B to reciprocate
inside their
respective cylinders 106A, 106B. The cylinder head 108, the cylinder 106A and
the crown of
the piston 116A define a variable volume combustion chamber 120A therebetween.
Similarly, the cylinder head 108, the cylinder 106B and the crown of the
piston 116B define a
variable volume combustion chamber 120B therebetween. It is contemplated that
the cylinder
block 104 could define more than two cylinders 106, in which case the ICE 24
would be
provided with a corresponding number of pistons 116 and connecting rods 114.
[00125] Air is supplied to the crankcase 102 via a pair of air intake ports
122 (only one of
which is shown in Figure 4A) formed in the back of the cylinder block 104. A
pair of throttle
bodies 124 is connected to the pair of air intake ports 122. Each throttle
body 124 has a
throttle plate 126 that can be rotated to control the air flow to the ICE 24.
Motors (not shown)
are used to change the position of the throttle plates 126, but it is
contemplated that throttle
cables connected to a throttle lever could be used. It is also contemplated
that a single motor
could be used to change the position of both throttle plates 126. A pair of
reed valves 128
(Figure 4A) are provided in each intake port 122. The reed valves 128 allow
air to enter the
crankcase 102, but prevent air from flowing out of the crankcase 102 via the
air intake ports
122.
[00126] As the pistons 116A, 116B reciprocate, air from the crankcase 102
flows into the
combustion chambers 120A, 120B via scavenge ports 130. Fuel is injected in the
combustion
chambers 120A, 120B by direct fuel injectors 132a, 132b respectively. The
direct fuel
injectors 132a, 132b are mounted to the cylinder head 108. The direct fuel
injectors 132a,
132b are connected by fuel lines and/or rails (not shown) to one or more fuel
pumps (not
shown) that pump fuel from a fuel tank 133 (Figure 1) of the snowmobile 10. In
the
illustrated implementation, the direct fuel injectors 132a, 132b are E-TECTm
fuel injectors,
however other types of direct fuel injectors are contemplated. The fuel-air
mixture in the
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combustion chamber 120A, 120B is ignited by spark plugs 134a, 134b
respectively (not
shown in Figures 2 to 5, but schematically illustrated in Figure 6). The spark
plugs 134a,
134b are mounted to the cylinder head 108.
[00127] To evacuate the exhaust gases resulting from the combustion of the
fuel-air
mixture in the combustion chambers 120A, 120B, each cylinder 116A, 116B
defines one
main exhaust port 136A, 136B respectively and two auxiliary exhaust ports
138A, 138B
respectively. It is contemplated that each cylinder 116A, 116B could have only
one, two or
more than three exhaust ports. It is also contemplated that a decompression
system (not
shown) may be added to the ICE 24 to allow decompressing the combustion
chambers 120A,
120B when the ICE 24 is stopped. The exhaust ports 136A, 136B (Figures 4A,
4B), 138A,
138B are connected to an exhaust manifold 140. The exhaust manifold is
connected to the
front of the cylinder block 104. Exhaust valves 142A, 142B mounted to the
cylinder block
104, control a degree of opening of the exhaust ports 136A, 136B, 138A, 138B.
In the present
implementation, the exhaust valves 142A, 142B are R.A.V.E.TM exhaust valves,
but other
types of valves are contemplated. It is also contemplated that the exhaust
valves 142A, 142B
could be omitted.
[00128] On Figure 4A, the piston 116B is shown at its top dead center (TDC)
position.
Figure 4B provides a cross-sectional view of the engine of Figure 3B with the
piston 116B at
its bottom dead center (BDC) position, allowing a better view of the main
exhaust port 136B
respectively and of the auxiliary exhaust port 138B.
[00129] An electric turning machine (ETM) is connected to the end of the
crankshaft 100
opposite the end of the crankshaft 100 that is connected to the drive pulley
62. In the present
implementation, the ETM is a motor-generator 144 (Figure 5), and more
specifically a three-
phase alternating current motor-generator 144, such as for example a permanent
magnet
synchronous motor (PMSM) with interior permanent magnet (IPM) or with surface
mounted
permanent magnet (SMPM), or a switched reluctance motor (SRM). It is
contemplated that
the motor-generator may include a number of pole pairs, generating electric
power cycling at
a rate that is a multiple of the rotational speed of the crankshaft 100. It is
further
contemplated that other types of motor-generators could be used, including for
example
multi-phase motor-generators or poly-phase motor-generators. It is also
contemplated that the
motor-generator 144 could be connected to another shaft operatively connected
to the
crankshaft 100, by gears or belts for example. The motor-generator 144, as its
name suggests,
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can act as a motor or as a generator and can be switched between either
functions. Under
certain conditions as described hereinbelow, the motor-generator 144 is
operated in motor
operating mode, being powered either by a small battery (not shown) or by a
capacitance 145
shown on Figure 3B.
[00130] A battery that is smaller and lighter than one conventionally used for
cold starting
of the ICE 24 may be used for an electric start procedure and/or for an
assisted start
procedure that will be described hereinbelow. Alternatively, the electric
start procedure
and/or the assisted start procedure may rely on the use of a capacitance 145.
Non-limiting
examples of capacitances include a high-capacity capacitor, an ultracapacitor
(U-CAP), an
electric double layer capacitor and a supercapacitor Either the small battery
or the
capacitance 145 supplies electric power to the motor-generator 144 for turning
the crankshaft
100. The capacitance 145 can accumulate relatively large amounts of energy. In
at least one
implementation, the capacitance 145 comprises a plurality of capacitors
assembled in series,
each capacitor of the series possibly including several capacitors mounted in
parallel so that
the capacitance 145 can withstand voltages generally within an operating
voltage range of the
direct fuel injectors 132A, 132B. In the context of the present disclosure,
references are made
to the capacitance 145 as a single unit. Without limitation and for brevity,
implementations in
which the electric start procedure or the assisted start procedure, or both,
are implemented
using the capacitance 145 along with the motor-generator 144 will be described
hereinbelow.
[00131] When operating as a generator, the motor-generator 144 is turned by
the crankshaft
100 and generates electricity that is supplied to the capacitance 145 and to
other electrical
components of the ICE 24 and the snowmobile 10. Electric power is exchanged
between the
capacitance 145 and the motor-generator 144 through an electrical converter.
In
implementations in which the motor-generator 144 is a three-phase motor, the
electrical
converter is a three-phase inverter 146. Use of multi-phase or poly-phase
invertors in
cooperation with a multi-phase or a poly-phase motor-generator is also
contemplated. Control
strategies of the motor-generator 144 applicable to its motoring and
generating functions and
the impact of these strategies on the capacitance 145 and on the inverter 146
are described
hereinbelow.
[00132] As can be seen in Figure 5, the motor-generator 144 has a stator 148
and a rotor
150. The stator 148 is disposed around the crankshaft 100 outside of the
crankcase 102 and is
fastened to the crankcase 102. The rotor 150 is connected by a keyway to the
end of the
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crankshaft 100 and partially houses the stator 148. A housing 152 is disposed
over the motor-
generator 144 and is connected to the crankcase 102. A cover 154 is connected
to the end of
the housing 152.
[00133] Three starting procedures of the snowmobile 10 may be available to the
user. A
first procedure comprises a manual start procedure that relies on the use of a
recoil starter
156. A second starting procedure comprises an electric start procedure. A
third starting
procedure comprises an assisted start procedure. One or both of the electric
and assisted start
procedures may be present in any implementation of the snowmobile 10. The
second and
third starting procedures will be describer further below. As can be seen in
Figure 5, the
recoil starter 156 is disposed inside the space defined by the housing 152 and
the cover 154,
between the cover 154 and the motor-generator 144. The recoil starter 156 has
a rope 158
wound around a reel 160. A ratcheting mechanism 162 selectively connects the
reel 160 to
the rotor 150. To start the ICE 24 using the recoil starter 156 in the manual
start procedure, a
user pulls on a handle 163 (Figure 3A) connected to the end of the rope 158.
This turns the
reel 160 in a direction that causes the ratcheting mechanism 162 to lock,
thereby turning the
rotor 150 and the crankshaft 100. The rotation of the crankshaft 100 causes
the pistons 116A,
116B to reciprocate which permits fuel injection and ignition to occur,
thereby starting the
ICE 24. When the ICE 24 starts, the rotation of the crankshaft 100 relative to
the reel 160
disengages the ratcheting mechanism 162, and as such the crankshaft 100 does
not turn the
reel 160. When the user releases the handle, a spring (not shown) turns the
reel 160 thereby
winding the rope 158 around the reel 160.
[00134] In the present implementation, the drive pulley 62 and the motor-
generator 144 are
both mounted to the crankshaft 100. It is contemplated that the drive pulley
62 and the motor-
generator 144 could both be mounted to a shaft other than the crankshaft 100,
such as a
counterbalance shaft for example. In the present implementation, the drive
pulley 62, the
motor-generator 144 and the recoil starter 56 are all coaxial with and rotate
about the axis of
rotation of the crankshaft 100. It is contemplated that the drive pulley 62,
the motor-generator
144 and the recoil starter 56 could all be coaxial with and rotate about the
axis of rotation of a
shaft other than the crankshaft 100, such as a counterbalance shaft for
example. It is also
contemplated that at least one of the drive pulley 62, the motor-generator 144
and the recoil
starter 56 could rotate about a different axis. In the present implementation,
the drive pulley
62 is disposed on one side of the ICE 24 and the motor-generator 144 and the
recoil starter 56
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are both disposed on the other side of the ICE 24. It is contemplated the
motor generator
and/or the recoil starter 56 could be disposed on the same side of the ICE 24
as the drive
pulley 62.
Control system for the internal combustion engine
5 [00135] Available starting procedures of the snowmobile 10 comprise an
electric start
procedure, an assisted start procedure and a manual start procedure. Figure 6
is a schematic
diagram of components of a control system of the engine of Figure 2. The
control of the
components used to start the ICE 24 in the electric start procedure and in the
assisted start
procedure is done by an engine control unit (ECU) 164 mounted to the ICE 24,
as shown on
10 Figures 3B and 4B. The assisted start procedure will be explained below.
The ECU 164 is
also used to control the operation of the ICE 24 after it has started. The ECU
164 is energized
by the capacitance 145, in a manner that will be described hereinbelow. The
ECU 164 is
illustrated as a single physical module (later shown in Figure 14) comprising
a single
processor (also in Figure 14), for example a single microcontroller. Other
configurations are
15 within the scope of the present disclosure. For instance, it is
contemplated that features of the
ECU 164 may be implemented using a plurality of co-processors, for example two
or more
microcontrollers. It is also contemplated that the various tasks of the ECU
164 could be split
between two or more microprocessors integrated in a single electronic module
or two or more
microprocessors distributed among various electronic modules. As a non-
limitative example,
20 the single electronic module may comprise a first processor adapted for
controlling a delivery
of electric power from the motor-generator 144 to the capacitance 145 and to
control the
delivery of electric power from the capacitance 145 to the motor-generator
144, and a second
processor adapted for controlling a fuel injection function and an ignition
function of the ICE.
To initiate an electric start procedure or an assisted start procedure of the
ICE 24, the ECU
25 164 receives inputs from the components disposed to the left of the ECU
164 in Figure 6,
some of which are optional and not present in all implementations, as will be
described
below. Using these inputs, the ECU 164 obtains information from control maps
166 as to
how the components disposed to the right of the ECU 164 in Figure 6 should be
controlled in
order to start the ICE 24. The control maps 166 are stored in an electronic
data storage
device, such as an electrically-erasable programmable read-only memory
(EEPROM) or a
flash drive. It is contemplated that instead of or in addition to the control
maps 166, the ECU
164 could use control algorithms to control the components disposed to the
right of the ECU
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164 in Figure 6. In the present implementation, the ECU 164 is connected with
the various
components illustrated in Figure 6 via wired connections; however it is
contemplated that it
could be connected to one or more of these components wirelessly.
[00136] A user actionable electric start switch 168, provided on the
snowmobile 10, for
example a push button mounted on or near the handlebar 36, sends a signal to
the ECU 164
that the user desires the ICE 24 to start when it is actuated. The electric
start switch 168 can
also be a switch actuated by a key, a sensor, or any other type of device
through which the
user can provide an input to the ECU 164 that the ICE 24 is to be started. In
at least one
implementation, the electric start switch 168 may be a sensor operably
connected to the rope
158 of the recoil starter 156 and to the ECU 164. Some traction, for example a
simple tugging
on the rope 158 by an operator, may be detected by this sensor, resulting in
the initiation of
the electric start procedure of the ICE 24, provided that all conditions for
the electric start
procedure are present.
[00137] A crankshaft position sensor (CPS) 171 and an absolute crankshaft
position sensor
(ACPS) 170 are disposed in the vicinity of the crankshaft 100 in order to
sense an absolute
position of the crankshaft 100. Readings of the CPS 170 are used by the ECU
164 to
determine a rotational speed of the crankshaft 170. From a manual start or
from an assisted
start, the CPS 170 becomes energized by an initial rotation of the crankshaft
100. Like the
ECU 164, the ACPS 170 is energized by the capacitance 145. In one
implementation, the
ACPS 170 is electrically connected to the capacitance 145 so that the ACPS 170
is constantly
energized, as long as there is a minimum level of charge in the capacitance
145. In another
implementation, the ACPS 170 becomes energized by the capacitance 145, via the
ECU 164,
in the course of a starting procedure, as will be described hereinbelow. In
the present
implementation, the CPS 171 is an inductive position sensor while the ACPS 170
is a sin/cos
Hall Effect encoder. Figure 5 shows an example of a location of a Hall Effect
ACPS 170 that
is placed at an extremity of the crankshaft 100 and rotates with the
crankshaft 100. The ACPS
170 may alternatively comprise an optical sensor. Figure 5 also shows a
location of the CPS
171, placed in a manner where it can track the movement of the rotor 150 of
the motor-
generator 144, the rotor 150 turning in synchrony with and at the same rate as
the crankshaft
100. The ACPS 170 senses the absolute position of the crankshaft 100 on a
continuous basis,
as long as the ACPS 170 is energized from an electric source (shown in later
Figures). The
ACPS 170 sends a signal representative of the absolute position of the
crankshaft 100 to the
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ECU 164. The absolute position of the crankshaft 100 provided by the ACPS 170
enables the
ECU 164 to determine the current position of the pistons 116A, 116B whether
the crankshaft
100 is rotating, or stopped in any position. In particular, the ECU 164 uses
the provided
absolute position information to determine the current position of the pistons
116A, 116B in
relation to their respective top dead center (TDC) positions. The current
position of a piston
in relation to its TDC position may be expressed in terms of degrees of
rotation before TDC
(BTDC) or after TDC (ATDC). Based on variations of the absolute position of
the crankshaft
100 received from the ACPS 170, the ECU 164 is also able to determine
rotational speed of
the crankshaft 100.
[00138] It is contemplated that an absolute position sensor (not shown) could
alternatively
sense the absolute position of a component of the ICE 24, other than the
crankshaft 100, that
turns in synchrony with the crankshaft 100, for example a water pump. Figure
4C is another
view of the engine of Figure 2, showing the location of a water pump,
generally at 173. In an
implementation, the water pump 173 turns at the same rate as the crankshaft
100. A magnet
175 is mounted to the water pump 173. A Hall effect sensor 177 is in a fixed
position and
tracks rotational movements of the magnet 175 when rotation of the crankshaft
100 causes
the rotation of the water pump 173. Other components of the ICE 24 on which
the absolute
position sensor may be mounted include, for example and without limitation,
the rotor 150 of
the motor-generator 144, a fuel pump, an oil pump, a camshaft (if the ICE is a
4-stroke
engine), a balance shaft (these component s are not shown), and the like. In
such a case,
based on a known mechanical configuration of the ICE 24, the ECU 164 can
deduce the
absolute position of the crankshaft 100 from the absolute position of this
component.
[00139] The ECU 164 controls the operation and timing of the direct fuel
injectors 132a,
132b and of the spark plugs 134a, 134b. To this end, when starting the ICE 24,
the ECU 164
uses the absolute position of the crankshaft 100, obtained from the ACPS 170,
to cause the
direct fuel injectors 132a, 132b to inject calculated amounts of fuel in their
respective
combustion chambers 120A, 120B a short time after the respective pistons 116A,
116B have
reached their TDC positions. The ECU 164 then causes the respective spark
plugs 134a, 134b
to ignite the fuel shortly thereafter. As an example and without limitation,
injection in the
combustion chamber 120A may take place when the crankshaft 100 has rotated
until the
piston 116A reaches a position in a range of about 3 degrees before TDC to 7
degrees after
TDC. Ignition by use of the spark plug 134 in the combustion chamber 1220A
follows, for
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example in a range of about 0 to 12 degrees beyond TDC (0 to 12 degrees ATDC)
for the
piston 116A. Injection and ignition timings vary according to operating
conditions of the ICE
24.
[00140] The assisted start procedure may be initiated, provided that
conditions are met as
described hereinbelow, when a rotation of the crankshaft 100 is initiated by
the user pulling
on the rope 158 of the recoil starter 156. The CPS 171 wakes up the ECU 164
upon initial
rotation of the crankshaft 100. The ECU 164 in turn causes the capacitance 145
to energize
the ACPS 170, allowing the ACPS 170 to inform the ECU 164 of the absolute
angular
position of the crankshaft 100.
[00141] A voltage sensor 167, for example a voltmeter, provides a measurement
of a
voltage of the capacitance 145 to the ECU 164. As explained in more details
hereinbelow, the
ECU 164 uses this voltage measurement to determine whether an energy reserve
of the
capacitance 145 is sufficient to start the ICE 24 using the electric start
procedure or to
provide assist using the assisted start procedure.
[00142] Optionally, other sensors can be used to determine whether or not the
engine can
be started using the electric start procedure or the assisted start procedure
as expressed
hereinbelow. These optional sensors include for example an engine temperature
sensor 172,
an air temperature sensor 174, an atmospheric air pressure sensor 176, an
exhaust
temperature sensor 178, a timer 180 and an ECU temperature sensor 182.
[00143] The engine temperature sensor 172 is mounted to the ICE 24 to sense
the
temperature of one or more of the crankcase 102, the cylinder block 104, the
cylinder head
108 and engine coolant temperature. The engine temperature sensor 172 sends a
signal
representative of the sensed temperature to the ECU 164.
[00144] The air temperature sensor 174 is mounted to the snowmobile 10, in the
air intake
system for example, to sense the temperature of the air to be supplied to the
ICE 24. The air
temperature sensor 174 sends a signal representative of the air temperature to
the ECU 164.
[00145] The atmospheric air pressure sensor 176 is mounted to the snowmobile
10, in the
air intake system for example, to sense the atmospheric air pressure. The
atmospheric air
pressure sensor 176 sends a signal representative of the atmospheric air
pressure to the ECU
164.
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[00146] The exhaust temperature sensor 178 is mounted to the exhaust manifold
140 or
another portion of an exhaust system of the snowmobile 10 to sense the
temperature of the
exhaust gases. The exhaust temperature sensor 178 sends a signal
representative of the
temperature of the exhaust gases to the ECU 164.
[00147] The timer 180 is connected to the ECU 164 to provide information to
the ECU 164
regarding the amount of time elapsed since the ICE 24 has stopped. The timer
180 can be an
actual timer which starts when the ICE 24 stops. Alternatively, the function
of the timer 180
can be obtained from a calendar and clock function of the ECU 164 or another
electronic
component. In such an implementation, the ECU 164 logs the time and date when
the ICE 24
is stopped and looks up this data to determine how much time has elapsed since
the ICE 24
has stopped when the ECU 164 receives a signal from the electric start switch
168 that the
user desires the ICE 24 to be started.
[00148] The ECU temperature sensor 182 is mounted to a physical module (not
shown) that
includes one or more processors (not shown) configured to execute the
functions of the ECU
164. The ECU temperature sensor 182 sends a signal representative of the
temperature of that
module to the ECU 164.
[00149] It is contemplated that one or more of the sensors 172, 174, 176, 178,
182 and the
timer 180 could be omitted. It is also contemplated that one or more of the
sensors 172, 174,
176, 178, 180, 182 and the timer 180 could be used only under certain
conditions. For
example, the exhaust temperature and pressure sensors 178, 180 may only be
used if the ICE
24 has been recently stopped, in which case some exhaust gases would still be
present in the
exhaust system, or following the first combustion of a fuel-air mixture in one
of the
combustion chambers 120A, 120B.
[00150] The ECU 164 uses the inputs received from at least some of the
electric start
switch 168, the sensors 167, 170, 171, 172, 174, 176, 178, 182 and the timer
180 to retrieve
one or more corresponding control maps 166 and to control the motor-generator
144, the
direct fuel injectors 132a, 132b, and the spark plugs 134a, 134b using these
inputs and/or the
control maps 166 to start the ICE 24, as the case may be. The inputs and
control maps 166 are
also used to control the operation of the ICE 24 once it has started. Though
not shown on
Figure 6 in order to simplify the illustration, the various components of the
control system of
Figure 6 are energized by the capacitance 145.
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[00151] The ECU 164 is also connected to a display 186 provided on the
snowmobile 10
near the handlebar 36 to provide information to the user of the snowmobile 10,
such as
engine speed, vehicle speed, oil temperature, and fuel level, for example.
[00152] Turning now to Figure 7, details of an electronic system for the
electric and
5 assisted start procedures for the ICE 24 will now be described. Figure 7
is a block diagram of
a dual-strategy control system for delivery of electric power between the
capacitance and the
ETM of Figure 6. Some components introduced in the foregoing description of
Figure 6 are
reproduced in Figure 7 in order to provide more details on their operation.
[00153] Electric power is delivered between the capacitance 145 and the motor-
generator
10 144 through the inverter 146. The ECU 164 includes, or is otherwise
operatively connected
to, a strategy switch 184 that is operative to change the control strategy for
the delivery of
electric power between the capacitance 145 and the motor-generator 144 between
at least two
(2) distinct control strategies. The ECU 164 controls the inverter 146 through
the strategy
switch 184.
15 [00154] To start the ICE 24 using the electric start procedure, the user
of the snowmobile
10 enters an input on the electric start switch 168, for example by depressing
a push button.
The ECU 164 is informed of this command. In response, the ECU 164 may control
a delivery
of electric power from the capacitance 145 to the motor-generator 144 based on
a pre-
determined amount of torque, or torque request, sufficient to cause rotation
of the crankshaft
20 .. 100 for starting the ICE 24. In a variant, the ECU 164 may determine the
torque request. The
determination of the torque request is made considering that ICE 24 is
expected to have a
highly irregular resistive torque; alternatively, instead of determining the
torque request, the
ECU 164 may determine a speed request applicable to the crankshaft 100 to
control an
amount of power that that the motor-generator 144 should apply to the
crankshaft 100 for
25 starting the ICE 24. A voltage of the capacitance 145 is sensed by the
voltage sensor 167 and
provided to the ECU 164. If this voltage is below an electric start voltage
threshold VmmE,
which is a minimum voltage of the capacitance 145 for the electric start
procedure, the ECU
164 determines that the capacitance 145 does not hold sufficient energy to
provide the torque
request, or the speed request, sufficient to start the ICE 24 using the
electric start procedure.
30 Consequently, the ECU 164 does not allow starting the ICE 24 using the
electric start
procedure and causes the display 186 to show a "manual start" indication or an
"assisted
start" indication, in implementations where this option is available.
Generally speaking, the
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electric start voltage threshold VmmE is based on a determination of a
sufficient charge of the
capacitance 145 allowing a successful electric start procedure in most
operating conditions. If
this minimum voltage threshold for the electric start procedure is met, the
ECU 164 causes
delivery of electric power from the capacitance 145 to the motor-generator
144, via the
inverter 146, in a first control strategy, initiating a rotation of the
crankshaft 100. The ECU
164 also causes the direct fuel injectors 132a and 132b to inject fuel
directly in the
combustion chambers 120A, 120B and causes the spark plugs 134a and 134b to
ignite the
fuel in the combustion chambers 120A, 120B. As mentioned hereinabove, the ICE
24 may
comprise one or more cylinders and the mention of two (2) combustion chambers
120A and
120B is for explanation purposes only. If these operations are successful, the
rotation of the
crankshaft 100 reaches a minimum revolution threshold corresponding to a
successful start of
the ICE 24. Thereafter, when a speed of the crankshaft 100 is equal to or
above the minimum
revolution threshold, the ECU 164 controls the delivery of electric power from
the motor-
generator 144 to the capacitance 145, still via the inverter 146, to cause
charging of the
capacitance 145. The delivery of electric power from the motor-generator 144
to the
capacitance 145 generally occurs in a second control strategy distinct from
the first control
strategy. A variant in which the delivery of electric power from the motor-
generator 144 to
the capacitance 145 occurs in the first control strategy at low revolution
speeds of the
crankshaft 100, or under low throttle demands, and in the second control
strategy at high
revolution speeds of the crankshaft 100 is also contemplated.
[00155] A current sensor 188 may be used to optimize the capacitance 145
current
consumption and optimize its energy usage. The current sensor 188 provides to
the ECU 164
an indication of the energy from the capacitance 145 being consumed during the
electric start
procedure. In an implementation, the current sensor 188 comprises a
combination of phase
current sensors (not explicitly shown) provided on two (2) phases of the motor-
generator 144.
Encoding of measurements from these two (2) phase current sensors provide a
good
estimation of a current flowing between the capacitance 145 and the motor-
generator 144. As
shown on Figure 13, current measurements may be obtained on all three (3)
phases of the
motor-generator 144. The capacitance 145 energy usage can alternatively be
optimized
without current sensors, for example, an open loop approach having a
predetermined torque
request pattern being applied by the ECU 164 to drive all cranking sequences
can be used. It
is also possible to optimize the energy usage of the capacitance 145 based on
a speed request
with well-tuned regulators or based on a predetermined pattern of multistep
speed requests.
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[00156] Electric start of the ICE 24 may fail although initial conditions for
the electric start
procedure were initially present. This may occur for instance if, while
electric power is being
delivered from the capacitance 145 to the motor-generator 144, the voltage
sensor 167 detects
that the voltage of the capacitance 145 falls below a residual voltage
threshold Vm,,,R, lower
than the electric start voltage threshold VmmE, before the rotational speed of
the crankshaft
100 reaches the minimum revolution threshold corresponding to the successful
start of the
ICE 24. Under such conditions, the ECU 164 ceases the delivery of power from
the
capacitance 145 to the motor-generator 144 and causes the display 186 to
provide a manual
start indication or an assisted start indication, in implementations where
this option is
available. Generally speaking, the residual voltage threshold VAthriR
corresponds to a
minimum charge of the capacitance 145 that is expected to suffice in allowing
the injection
and ignition of fuel injection in the combustion chambers 120A, 120B while
continuing the
rotation of the crankshaft 100.
[00157] To start the ICE 24 using the assisted start procedure, the user of
the snowmobile
10 pulls on the rope 158 of the recoil starter 156, initiating a rotation of
the crankshaft 100.
The CPS 171 wakes up the ECU 164 upon initial rotation of the crankshaft 100
and the
ACPS 170 then informs the ECU 164 of the absolute angular position of the
crankshaft 100.
In response, the ECU 164 may control a delivery of electric power from the
capacitance 145
to the motor-generator 144 to assist the rotation of the crankshaft 100 for
starting the ICE 24.
Optionally, a voltage of the capacitance 145 is sensed by the voltage sensor
167 and provided
to the ECU 164. In this case, if this voltage is below an assisted start
voltage threshold VmmA,
which is a minimum voltage of the capacitance 145 for the assisted start
procedure, the ECU
164 determines that the capacitance 145 does not hold sufficient energy to
assist starting the
ICE 24 and the ECU 164 does not allow starting the ICE 24 using the assisted
start
procedure, instead causing the display 186 to show a "manual start"
indication. Generally
speaking, the assisted start voltage threshold VminA is based on a
determination of a sufficient
charge of the capacitance 145 allowing a successful assisted start procedure
in predetermined
operating conditions. In implementations where both electric and assisted
start procedures are
present, the assisted start voltage threshold VminA is lower than the
electrical start voltage
threshold VmmE. If this minimum voltage threshold for the assisted start
procedure is met, the
ECU 164 causes delivery of electric power from the capacitance 145 to the
motor-generator
144, via the inverter 146, in the first control strategy, assisting the
rotation of the crankshaft
100. The ECU 164 also causes the direct fuel injectors 132a and 132b to inject
fuel directly in
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the combustion chambers 120A, 120B and causes the spark plugs 134a and 134b to
ignite the
fuel in the combustion chambers 120A, 120B. As mentioned hereinabove, the ICE
24 may
comprise one or more cylinders and the mention of two (2) combustion chambers
120A and
120B is for explanation purposes only. If these operations are successful, the
rotation of the
crankshaft 100 reaches a minimum revolution threshold corresponding to a
successful start of
the ICE 24. Thereafter, operation of the ICE 24 is as expressed in the
foregoing description to
the electrical start procedure.
[00158] Figure 8 is a block diagram of an energy management circuit for the
capacitance
145 of Figure 6. A circuit 200 shows how, in an implementation, the CPS 171,
the ECU 164
and the capacitance 145 are electrically connected. In the case of the
electric start procedure,
the connection between the capacitance 145 and the ECU 164 is effected using
the electric
start switch 168, which is shown as a pushbutton. In the case of the assisted
start procedure
and in the case of the manual start procedure, the connection is effected by a
signal from the
CPS 171, which is present at the onset of the rotation of the crankshaft 100.
The capacitance
.. 145 is illustrated as a sum of smaller capacitors 202 connected in series.
As mentioned
earlier, each of these smaller capacitors 202 may actually consist of a
plurality of capacitors
connected in parallel. Each of the smaller capacitors 202 can withstand a
relatively low
voltage applied thereon. The capacitance 145 formed by the sum of the smaller
capacitors
202 in series can withstand the nominal voltage of the circuit 200, which is
also the nominal
voltage of the electrical systems of the snowmobile 10, with the addition of a
safety margin
for occasional overvoltage
[00159] The circuit 200 provides an output voltage between a lead 208 and a
ground
reference 210 when the circuit 200 is active. When the circuit 200 is
inactive, the capacitance
145 is disconnected from the ground reference 210 by power electronic
switches, for example
metal-oxide semiconductor field effect transistors (MOSEFT) Q1 and Q2 which
are, at the
time, turned off and therefore open circuit. Substituting a bipolar
transistor, for example an
insulated gate bipolar transistor (IGBT), for the MOSFETs Q1 and Q2 is also
contemplated.
The available voltage of the capacitance 145 is defined between terminals 208
and 210 that
are electrically connected to the voltage sensor 167 shown on earlier Figures.
[00160] A capacitor Cl shown on Figures 3B and 4B and schematically
illustrated on
Figure 8 is present between the lead 208 and the ground reference 210. The
role of the
capacitor Cl is to filter voltage variations from the capacitance 145 for the
benefit of the
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various electrical components of the snowmobile 10, including for example the
direct fuel
injectors 132a and 132b, headlights, and the like. The capacitor Cl may be
omitted in some
implementations. The voltage between the lead 208 and the ground reference
210, which is a
system voltage for the snowmobile 10, is essentially the same as the nominal
voltage of the
capacitance 145, although operating voltages between different system states
may not be
constant at all times.
[00161] When the ICE 24 has been stopped for a long time, more than a few
hours for
example, the voltage on the capacitance 145 falls below the electric start
voltage threshold
VmmE and below the assisted start voltage threshold VminA, and the circuit 200
is not
energized. Resorting to the manual start procedure is therefore required for
starting the ICE
24. When the ICE 24 has been stopped for a relatively short time, a duration
of which
depends in large part on the energy storage capacity of the capacitance 145,
the voltage on
the capacitance 145 may be equal to or above the electric start voltage
threshold VmmE, in
which case the electric start procedure is available. If the voltage of the
capacitance 145 is
lower than the electric start voltage threshold VmmE while at least equal to
or greater than the
assisted start voltage threshold VminA, the assisted start procedure may be
available. The
assisted start procedure is described in more details hereinbelow.
[00162] When the voltage of the capacitance 145 is at least equal or greater
than the electric
start voltage threshold VmmE, depressing the electric start switch 168
(pushbutton) by the user
invokes the electric start procedure. This user action is sensed by a start
command detector
212 of the ECU 164. When the user initiates a manual start procedure or an
assisted start
procedure, the CPS 171 is energizes and sends an initiating signal to the
start command
detector 212.
[00163] The start command detector 212 wakes up the ECU 164. At the same time,
electrical power starts being provided from the capacitance 145 to the ECU
164. Depending
on specific implementations, the start command detector 212 may accept a
simple brief
electrical contact provided by the electric start switch 168 to initiate the
electric start
procedure. The start command detector 212 may alternatively require the
electric start switch
168 to be depressed for a few seconds. After sensing the electric start
command or the
initiating signal, the start command detector 212 sends a signal to a wake up
circuit 214 of the
ECU 164. The wake up circuit 214 controls the following operations.
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[00164] Initially, the wake up circuit 214 applies an initiation signal 220 to
a driver 216 of
the transistor Ql, which is a run-time power electronic switch. The driver 216
further applies
the initiation signal to the transistor Ql, causing the transistor Q1 to turn
on, allowing the
capacitance 145 to start charging the capacitor Cl via a current limiting
circuit 224. As soon
5 as a voltage starts being established in the capacitor Cl, the wake up
circuit 214 terminates
the initiation signal 220 and applies a start signal 221 to a driver 217 of
the transistor Q2,
which is a start-up power electronic switch, effectively placing the
capacitance 145 in parallel
with the capacitor Cl to further charge the capacitor Cl. In an
implementation, the wake up
circuit 214 controls the driver 217 to repeatedly turn on and off the
transistor Q2 at a high
10 frequency in order to prevent excessive current flowing from the
capacitance 145 to the
capacitor Cl. For example, the wake up circuit 216 of the ECU 164 may vary the
start signal
221 according to a pulse width modulation (PWM) mode. Electrical conduction
through the
transistor Q2 may be controlled in a small duty cycle at first, the duty cycle
increasing as a
voltage difference between the capacitor Cl and the capacitance 145 decreases.
Regardless,
15 the capacitor Cl rapidly charges to reach the voltage of the capacitance
145. The capacitance
145 voltage may reduce slightly as a result from this voltage equalization,
but this effect is
limited by the fact that the capacitor Cl is much smaller than the capacitance
145. After the
capacitor Cl has been charged, an electric connection is made between the lead
208 and the
various sensors 167, 170, 171, 172, 174, 176 and 182, the timer 180, and other
components of
20 the snowmobile 10 that may be energized at the same time or later,
according to the needs of
the application.
[00165] In an implementation where the capacitor Cl is not present, the wake
up circuit
214 may not apply the initiation signal 220 to the driver 216. In that case,
in response to the
signal from the start command detector 212, the wake up circuit 214 simply
applies the start
25 signal 221 to the driver 217 of the transistor Q2 so that the
capacitance 145 voltage becomes
available at the lead 208.
[00166] In an implementation where the ACPS 170 is not permanently connected
to the
capacitance 145, it becomes energized at the onset of a start procedure,
through the lead 208
following this voltage equalization, so to enable the reading of the current
(i.e. initial)
30 absolute angular position of the crankshaft. This reading is provided by
the ACPS 170 to the
ECU 164. The electric start then continues with the ECU 164 controlling the
delivery of
power from the capacitance 145 to the motor-generator 144 via the lead 208,
which is
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connected to the inverter 146 in one of the manners described in relation to
the following
Figures. The ECU 164 may control the transistor Q2 in the PWM mode to limit a
level of
electric power delivery from the capacitance 145 to the motor-generator 144.
[00167] Once the electric start procedure has been successfully executed, as
the ICE 24 is
running at idle, the motor-generator 144 may initially have a limited power
generating
capacity. Accessories of the snowmobile 10, including for example the direct
fuel injectors
132a and 132b and headlights, require a certain amount of power. It is more
critical to the
operation of the vehicle to power these accessories than recharging the
capacitance 145. To
avoid an excessive drop of the voltage of the capacitor Cl, at the lead 208,
while the ICE 24
is idling or running, the ECU 164 may optionally control the driver 217 to
turn off the
transistor Q2 until the crankshaft 100 rotates at more than a predetermined
revolution
threshold.
[00168] Once the ICE 24 has acquired a sufficient speed, the voltage at the
lead 208 being
now sufficient, the ECU 164 stops the start signal 221 to the driver 217,
causing the turning
off (opening) of the transistor Q2. The ECU 164 also sends a recharge signal
222 to the driver
216 of the transistor Ql. The driver 216 further applies the recharge signal
to the transistor
Ql, causing turning on (closing) of the transistor Ql. The transistor Q1 is
connected in series
with the current limiting circuit 224. The transistor Q1 effectively places
the capacitance 145
in contact with the capacitor Cl, the current limiting circuit 224 regulating
the charging rate
of capacitance 145 while respecting the electrical power availability at any
speed of the ICE
24. In an implementation, the current limiting circuit 224 comprises a
resistor or an inductor
(not shown).
[00169] In an alternate implementation, the circuit 200 includes a single
driver 217 and a
single transistor Q2 and does not include a current limiting circuit. The wake
up circuit 214
intermittently applies the start signal 221 to the driver 217 of the
transistor Q2, for example
according to a PWM mode, so that the voltage gradually increases at the lead
208 until it
becomes substantially equal to the voltage of the capacitance 145. In the same
implementation, the recharge signal 222 is also applied to the driver 216 of
the transistor Q2.
Instead of using the current limiting circuit 224 to regulate the charging
rate of the
capacitance 145, the recharge signal 222 may also be applied to the driver 217
according to a
PWM mode. As will be expressed hereinbelow, a control strategy of the delivery
of electric
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power from the motor-generator 144 to the capacitance 145 may alternatively be
used to
regulate the charging rate of the capacitance 145.
[00170] The ECU 164 may optionally integrate an automatic shutdown circuit
that may
terminate all electrical functions of the snowmobile 10 in case of system
failure.
[00171] Table I provides a sequence of events including a manual start
procedure of the
ICE 24, followed by an electric start procedure command received after a
waiting time that
does not exceed the capabilities of the electric start system. In Table I,
mentions of "PWM"
refer to "pulse width modulation", a technique that may optionally be used in
the first and
second control strategies to control delivery of electric power between the
capacitance 145
and the motor-generator 144, as expressed hereinbelow.
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T Event ECU 164 Cl voltage Capacitance 01 and 02 Motor-
Y state 145 voltage states generator
P _144
E
Initial OFF 0 volt 0 volt Q1 off; Stopped
conditions Q2 off
Pulling Wake-Up Rising 0 volt Q1 off; Rising
M the rope Q2 off speed
A (1st time)
N Pulling Firing Rising to 0 volt Q1 off; Rising
to
U the rope nominal Q2 off idle
speed
A (211d time) voltage
L Releasing Ignition / Nominal Rising, but less Q1
100% on; Idle speed
the rope PWM voltage than nominal Q2 off or engine
voltage running
Stop Turning Falling Nominal Q1 off; Falling
- OFF voltage Q2 off speed
Waiting OFF Close to 0 Less than Q1 off; Stopped
time volt nominal Q2 off
voltage, but
equal to or
above VmmE
Electric Wake-Up Close to 0 Less than Q1 off; Stopped
start volt nominal Q2 off
command voltage, but
equal to or
above VmmE
--- Ignition / Equalizing to Reducing Q1
on for a Stopped
E PWM the slightly short period,
L capacitance then off;
E voltage Q2 initially
C off, then
T cycling on
R and off
I --- Cranking Equal to the Reducing, but Q1 off;
Rising
C capacitance still equal to or Q2 100% on speed
voltage above VmRIR
--- Firing Rising Rising Q1 off; Rising
to
Q2 100% on idle speed
Ready to Ignition / Nominal Nominal Q1 100% on; Idle speed
apply PWM voltage voltage Q2 off or engine
throttle running
Table I
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[00172] In Table I, the expression "idle speed or engine running" means that
the ICE 24 is
started and running on its own, no torque being applied thereon by the motor-
generator 144
or by use of the recoil starter 156.
[00173] In at least one implementation, both minimum voltage thresholds VmmE
and VminR
may be defined within an operating voltage range of the direct fuel injectors
132a and 132b
so that, if the voltage of the capacitance 145 is not sufficient for the
direct fuel injectors 132a
and 132b to inject fuel in the cylinders 106A, 106B, the electric start
procedure is not
attempted, or terminated if unsuccessful.
Electric start procedure
[00174] Figure 9 is a logic diagram of a method for starting the engine of
Figure 2
according to an implementation. A sequence shown in Figure 9 comprises a
plurality of
operations, some of which may be executed in variable order, some of the
operations possibly
being executed concurrently, and some of the operations being optional. The
method begins
at operation 300 when the ICE 24 of the snowmobile 10 is stopped. A voltage of
the
capacitance 145 is measured by the voltage sensor 167 at operation 302. In the
same
operation 302, the display 186 may provide an "automatic start" indication if
the voltage
meets or exceeds the electric start voltage threshold VmmE and if other
conditions described
hereinbelow for the electric start procedure are met. The user actuates the
electric start switch
168, this being detected by the start command detector 212 at operation 304.
At operation
322, in response to the detection of the electric start request, the ECU 164
controls the drivers
216 and 217 of the transistors Q1 and Q2 to allow the capacitance 145 to
charge the capacitor
Cl until their voltages are equalized. The ECU 164 and the various sensors,
including in
particular the ACPS 170, are energized by the capacitance 145 as a result of
this voltage
equalization. A comparison is then made by the ECU 164, at operation 306,
between the
voltage of the capacitance 145 and the electric start voltage threshold VmmE
to determine
whether it is possible to initiate the electric start procedure for the ICE
24. If it is determined
that the voltage of the capacitance 145 is below the electric start voltage
threshold VmmE, the
electric start procedure is prevented. Otherwise, verification is made at
operation 308 that the
engine temperature measured by the engine temperature sensor 172 meets or
exceeds an
engine temperature threshold Th0. The electric start procedure is prevented in
this threshold
for the engine temperature is not met. Otherwise, verification is made at
operation 310 that
the ECU temperature sensor 182 provides a reading of the temperature of the
ECU 164 that
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meets or exceeds an ECU temperature threshold Thl. The electric start
procedure is
prevented if this threshold for the ECU temperature is not met. Additional
operations related
to use of measurements obtained from other sensors introduced in the foregoing
description
of Figure 6 may take place. These measurements may be provided to the ECU 164
by the air
5 temperature sensor 174, the atmospheric temperature sensor 176, or the
timer 180. Additional
tests based on those measurements may be executed by the ECU 164 to determine
whether or
not the electric start procedure is likely to succeed or to determine a torque
value sufficient to
cause the rotation of the crankshaft 100. For example, the electric start
procedure may be
made conditional, in the ECU 164, on the timer 180 informing the ECU 164 that
a period of
10 .. time since the ICE 24 has been stopped is below a predetermined time
value when the user
actuates the electric start switch 168 at operation 304. On the basis of the
period of time since
the ICE 24 has been stopped, it is possible to estimate whether the voltage of
the capacitance
145 will have fallen below the electric start voltage threshold VmmE knowing a
maximum
charge voltage of the capacitance 145 from a previous running sequence of the
ICE 24, and
15 based on a typical energy leakage of the capacitance 145.
[00175] Whether the electric start procedure is prevented because the voltage
of the
capacitance 145 is insufficient (operation 306), because the engine
temperature is too low
(operation 308), because the ECU temperature is too low (operation 310), or
for any other
reason, the method proceeds to operation 312. At operation 312, the ECU 164
causes the
20 display 186 to display "Manual Start" or some other message indicating
to the user of the
snowmobile 10 that the snowmobile 10 will need to be started manually using
the recoil
starter 156 (i.e. by pulling on the handle 163). In implementations where the
assisted start
procedure is available, the display 186 may instead display "Assisted Start"
or some other
equivalent message, provided that current conditions allow using this
procedure. Displaying
25 the manual start indication or the assisted start indication at
operation 312 may follow any
decision taken by the ECU 164 to not proceed with the electric start
procedure. It is
contemplated that instead of providing a message on the display 186, that the
ECU 164 could
cause a sound to be heard or provide some other type of feedback to the user
of the
snowmobile 10, indicating that the snowmobile 10 will need to be started
manually using the
30 recoil starter 156. A manual start procedure or an assisted start
procedure may be initiated
when the user pulls on the rope 158 of the recoil starter 156. If conditions
for the assisted
start procedure are met, this procedure may be initiated as described
hereinbelow. Otherwise,
when the conditions for the assisted start procedure are not met, the manual
start procedure
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may be initiated at operation 314 when, in response to sensing the operation
of the recoil
starter 156 by the user of the snowmobile 10, the ECU 164 initiates an engine
control
procedure associated with the use of the recoil starter 156 in order to start
the ICE 24 using
the recoil starter 156. Then at operation 316, the ECU 164 determines if the
ICE 24 has been
successfully started using the recoil starter 156. If not, then operation 314
is repeated. It is
also contemplated that if at operation 316 it is determined that the ICE 24
has not been
successfully started, that the method could return to operation 312 to display
the message
again. If at operation 316 it is determined that the ICE 24 has been
successfully started, then
the method proceeds to operations 318 and 320, these last two (2) operations
being operated
concurrently. At operation 318, the ECU 164 operates the ICE 24 according to
the control
strategy or strategies to be used once the ICE 24 has started. At operation
320, the ECU 164
controls the inverter 146 to cause power to be delivered from the motor-
generator 144 to the
capacitance 145, charging the capacitance 145 using the second control
strategy at a voltage
that remains fairly constant for a wide range of rotational speeds of the
crankshaft 100. This
may be achieved by the ECU 164 shunting one or more of the Phases A, B and C
of the
motor-generator 144 if, in the second control strategy, the motor-generator
144 generates a
voltage that exceeds a maximum voltage threshold. The ECU 164 may linearly
regulate the
voltage generated by the motor-generator 144 by using a series regulation mode
or a shunt
mode. The maximum voltage threshold may for example be equal or slightly
superior to the
nominal voltage of the circuit 200.
[00176] If at operations 306, 308 and 310 the ECU 164 determines that the
capacitance
voltage is equal to or above the electric start voltage threshold VmmE and
that the temperature
conditions and any other condition are also met, the method continues at
operation 324 where
the ECU 164 obtains a value of the absolute angular position of the crankshaft
100 from the
ACPS 170. This operation 324 may continue on an ongoing fashion during the
complete
electric start procedure so that the following operations may be optimized
according to the
varying angular position of the crankshaft 100. It is contemplated that
operations 322 and 324
may be omitted or substituted with other actions. For example, the electric
start procedure
may be rendered independent from the angular position of the crankshaft 100 by
providing a
capacitance 145, the battery, or other power source having sufficient energy
storage
capability to rotate the crankshaft 100 with no concern for its actual angular
position.
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[00177] The electric start procedure proceeds with operation 326 and continues
through
operations 328, 330 and, if required, operation 332. These operations are
initiated in the
sequence as shown on Figure 9, but are then executed concurrently until the
electric start
procedure is found successful or until it needs to be terminated.
.. [00178] At operation 326, the ECU 164 determines the torque value
sufficient to cause the
rotation of the crankshaft 100 and initiates delivery of power from the
capacitance 145 to the
motor-generator 144, through the inverter 146, via the first control strategy
which adapts the
delivery of power in view of the determined torque value. This transfer of
power causes a
rotation of the crankshaft 100. Optionally, the ECU 164 may determine the
torque value in
sub-steps, in which a first sub-step comprises delivering electric power from
the capacitance
145 to the three-phase motor-generator 144 according to a first torque value
to cause slow
turning of the crankshaft at a first rotational speed until the piston is
brought beyond its top
dead center (TDC), based on information provided by the ACPS 170 and based on
the
contents of the control maps 166, a second sub-step comprising delivering
electric power
from the capacitance 145 to the three-phase motor-generator 144 according to a
second
torque value, greater than the first torque value to cause turning of the
crankshaft at a second
rotational speed, the second rotational speed being greater than the first
rotational speed.
[00179] While operation 326 is ongoing, particularly while the second sub-step
is ongoing
if operation 326 comprises two sub-steps, the method proceeds to operation 328
in which the
ECU 164 causes the direct fuel injectors 132a, 132b to inject fuel directly in
the combustion
chambers 120a, 120b and causes the spark plugs 134a, 134b to ignite the fuel
in the
combustion chambers 120a, 120b, thereby accelerating the rotation of the
crankshaft 100.
The absolute angular position of the crankshaft 100 may be used by the ECU 164
to properly
time the fuel injection and the ignition. The ACPS 170 being an absolute
position sensor, it
can determine the position of the crankshaft 100 while it is stationary, prior
to starting of the
ICE 140. This technique provides precise fuel injection and ignition timing at
a very low
rotational speed of the ICE 24, such as when the ICE 24 is starting. This
technique decreases
the chances of a failed start procedure due to an insufficient combustion
within the
combustion chambers 102A, 120B, this insufficient combustion resulting from
imprecise fuel
injection quantities or ignition timing calculated from an imprecise
crankshaft position. This
technique further promotes faster synchronization between all components of
the ICE 24 that
rely on the position of the crankshaft 100 when compared to the use of
position sensors that
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require the crankshaft 100 to be rotating to determine its position. Use of
mechanical
actuators (not shown) operably connected to the crankshaft 100 to control
injection and
ignition timings is also contemplated. It is further contemplated that a
quantity of fuel to be
injected and the ignition timing as applied by the ECU 164 at operation 328
may be evaluated
using any known method, optionally depending on one or more of an engine
temperature, an
air temperature, an atmospheric pressure, and an exhaust temperature, these
values being
provided to the ECU 164 by the various sensors shown on Figure 6.
[00180] While operations 326 and 328 are ongoing, the method proceeds to
operation 330,
in which the ECU 164 compares a rotational speed of the crankshaft 100 to a
minimum
revolution threshold to determine if the ICE 24 has been successfully started
using the
electric start procedure. If the rotational speed of the crankshaft 100 is
equal to or above the
minimum revolution threshold, the ICE 24 has been successfully started, the
electric start
procedure ends and the method proceeds to operations 318 and 320, which are
described
hereinabove.
[00181] If, at operation 330, the ECU 164 determines that the ICE 24 has not
yet been
started, the rotational speed of the crankshaft 100 being below the minimum
revolution
threshold, the method continues at operation 332 where the ECU 164 monitors
again the
voltage of the capacitance 145. It is expected that this voltage will be
reduced somewhat as
energy previously stored in the capacitance 145 has been spent during
operations 326 and
.. 328. However, if a remaining voltage of the capacitance 145 is equal to or
above the residual
voltage threshold Vm,,,R, the electric start procedure returns to operations
326 and 328, which
are still ongoing, and then at operation 330. If however the ECU 164
determines at operation
332 that the capacitance voltage has fallen below the residual voltage
threshold VmmR, the
method proceeds to operation 334 where the ECU 164 ceases the delivery of
power from the
.. capacitance 145 to the motor-generator 144 and terminates operations 326
and 328. The
method then moves from operation 334 to operation 312, which is described
hereinabove, in
which the ECU 164 causes the display 186 to display a manual start indication,
or an assisted
start indication in implementations where this option is available, operation
312 being
followed by operations 314, 316, 318 and 320 in the case of a manual start.
[00182] Figure 10 is a timing diagram showing an example of variations of an
engine
resistive torque as a function of time along with corresponding engine
rotational speed
variations. A graph 400 shows a variation of the resistive torque of the ICE
24, in Newton-
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Meters (Nm) as a function of time, in seconds. The graph 400 was obtained from
a
SimulinkTM model. As shown on the graph 400, the rotational speed in the
starting phase is
about 100 revolutions per minute (RPM). The resistive torque may vary in
relation to the
rotational speed of the crankshaft 100. A graph 402 shows a corresponding
variation of a
rotational speed of the crankshaft 100 over the same time scale. In the
simulation, the two-
cylinder ICE 24 is firing when a piston first reaches near TDC. After less
than 0.1 seconds,
the resistive torque becomes negative because the piston has passed beyond its
TDC.
Compression present in the combustion chamber pushes on the piston and
accelerates the
rotation of the crankshaft 100. At about 0.12 seconds, the ECU 164 controls
the torque
applied to the crankshaft 100 by the motor-generator 144, accelerating the
rotation of the
crankshaft 100. The rotational speed of the crankshaft 100 reaches a plateau
at about 0.17
seconds because the piston is now compressing gases that may remain present in
the
combustion chamber. The rotational speed decreases as the piston arrives near
its TDC. TDC
is reached at about 0.32 seconds. Successful ignition takes place, whereafter
the rotational
speed of the crankshaft 100 increases rapidly while the resistive torque on
the motor-
generator 144 becomes essentially negative, following a toothed saw wave shape
as the
piston cycles up and down in its cylinder.
Assisted start procedure
[00183] Figure 11 is a logic diagram of a method for starting the engine of
Figure 2
according to another implementation. A sequence shown in Figure 11 comprises a
plurality of
operations, some of which may be executed in variable order, some of the
operations possibly
being executed concurrently, and some of the operations being optional. The
method begins
at operation 600 when the ICE 24 of the snowmobile 10 is stopped. A voltage of
the
capacitance 145 is measured by the voltage sensor 167 at operation 602. In the
same
operation 602, the display 186 may provide an "assisted start" indication if
the voltage meets
or exceeds the assisted start voltage threshold VmmA and if other conditions
described
hereinbelow for the assisted start procedure are met. At operation 604, the
user initiates a
rotation of the crankshaft 100 by pulling on the rope 158 of the recoil
starter 156, this
operation being detected by the CPS 171 that in turn sends the initiating
signal to the start
command detector 212 to wake up the ECU 164. In one variant, the ACPS 170
becomes
energized at the onset of the start procedure by the ECU 170 which has itself
been awaken by
the CPS 171. In another variant, the ACPS 170 is permanently connected to the
capacitance
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145 so that it is able to detect the absolute angular position of the
crankshaft 100 whenever
the capacitance 145 holds at least a minimum charge. Detecting the initial
rotation of the
crankshaft 100 may be conditional to the ACPS 170 detecting that a revolution
speed of the
crankshaft 100 meets or exceeds a minimal revolution threshold. At operation
606, the ECU
5 164 controls the drivers 216 and 217 of the transistors Q1 and Q2 to
allow the capacitance
145 to charge the capacitor Cl until their voltages are equalized. The ECU 164
and the
various sensors, including in particular the ACPS 170, are energized by the
capacitance 145
as a result of this voltage equalization. A comparison is made by the ECU 164
at operation
608 between the voltage of the capacitance 145 and the assisted start voltage
threshold VminA
10 to determine whether it is possible to initiate the assisted start
procedure for the ICE 24. If it
is determined that the voltage of the capacitance 145 is below the assisted
start voltage
threshold VminA, the assisted start procedure is prevented. Otherwise,
verification is made at
operation 610 that the engine temperature measured by the engine temperature
sensor 172
meets or exceeds an engine temperature threshold Th0. The assisted start
procedure is
15 prevented in this threshold for the engine temperature is not met.
Otherwise, verification is
made at operation 612 that the ECU temperature sensor 182 provides a reading
of the
temperature of the ECU 164 that meets or exceeds an ECU temperature threshold
Thl. The
assisted start procedure is prevented if this threshold for the ECU
temperature is not met.
Additional operations related to the use of measurements obtained from other
sensors
20 introduced in the foregoing description of Figure 6 may take place.
These measurements may
be provided to the ECU 164 by the air temperature sensor 174, the atmospheric
temperature
sensor 176, or the timer 180. Additional tests based on those measurements may
be executed
by the ECU 164 to determine whether or not the assisted start procedure is
likely to succeed.
For example, the assisted start procedure may be made conditional, in the ECU
164, on the
25 timer 180 informing the ECU 164 that a period of time since the ICE 24
has been stopped is
below a predetermined time value when the user pulls on the rope 158 of the
recoil starter
156 at operation 604, On the basis of the period of time since the ICE 24 has
been stopped, it
is possible to estimate whether the voltage of the capacitance 145 will have
fallen below the
assisted start voltage threshold VminA knowing a maximum charge voltage of the
capacitance
30 145 from a previous running sequence of the ICE 24, and based on a
typical energy leakage
of the capacitance 145.
[00184] Displaying the manual start indication at operation 614 may follow any
decision
taken by the ECU 164 to not proceed with the assisted start procedure. Whether
the assisted
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start procedure is prevented because the voltage of the capacitance 145 is
insufficient
(operation 608), because the engine temperature is too low (operation 610),
because the ECU
temperature is too low (operation 612) or for any other reason, the method
proceeds to
operation 614. At operation 614, the display 186 may display "Manual Start".
Following
operation 614, the user may continue pulling on the rope 158 of the recoil
starter 156 at
operation 616. Operation 616 may continue until it is detected at operation
618 that the ICE
24 is properly started. Control of ICE 24 and delivery of electric power from
the motor-
generator 145 to the capacitance 144 follow at 620 and 622, which are the same
or equivalent
as operations 318 and 320 of Figure 9 including, in an implementation,
controlling the ICE
24 using the above described control strategies.
[00185] If at operations 608, 610 and 612, the ECU 164 determines that the
capacitance
voltage is equal to or above the assisted start voltage threshold VminA and
that the temperature
conditions and any further condition are also met, the method continues at
operation 624
where the ACPS 170 senses a current, absolute angular position of the
crankshaft 100.
[00186] The assisted start procedure proceeds with operation 626 and continues
through
operations 628, 630 and, if required, operation 632. These operations are
initiated in the
sequence as shown on Figure 11, but are then executed concurrently until the
assisted start
procedure is found successful or until it needs to be terminated.
[00187] At operation 626, the ECU 164 initiates delivery of power from the
capacitance
145 to the motor-generator 144, through the inverter 146. This transfer of
power accelerates
the rotation of the crankshaft 100 and reduces the amount of effort that needs
to be exerted by
the user pulling on the rope 158 of the recoil starter 156. The ECU 164 may
optionally
determine a torque value in the same manner as described in the foregoing
description of
operation 326 (Figure 9).
[00188] While operation 626 is ongoing, the method proceeds to operation 628
in which
the ECU 164 causes the direct fuel injectors 132a, 132b to inject fuel
directly in the
combustion chambers 120a, 120b and causes the spark plugs 134a, 134b to ignite
the fuel in
the combustion chambers 120a, 120b, thereby accelerating further the rotation
of the
crankshaft 100. The angular position of the crankshaft 100 is used by the ECU
164 to
properly time the fuel injection and the ignition. It is contemplated that a
quantity of fuel to
be injected and the ignition timing as applied by the ECU 164 at operation 628
may depend
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on one or more of an engine temperature, an air temperature, an atmospheric
pressure, and an
exhaust temperature, these values being provided to the ECU 164 by the various
sensors
shown on Figure 6.
[00189] While 626 and 628 are ongoing, the method proceeds to operation 630,
in which
the ECU 164 compares a rotational speed of the crankshaft 100 to a minimum
revolution
threshold to determine if the ICE 24 has been successfully started using the
assisted start
procedure. If the rotational speed of the crankshaft 100 is equal to or above
the minimum
revolution threshold, the ICE 24 has been successfully started, the assisted
start procedure
ends and the method proceeds to 620 and 622, which are described hereinabove.
[00190] If, at operation 630, the ECU 164 determines that the ICE 24 has not
yet been
started, the rotational speed of the crankshaft 100 being below the minimum
revolution
threshold, the method continues at operation 632 where the ECU 164 monitors
again the
voltage of the capacitance 145. It is expected that this voltage will be
reduced somewhat as
energy previously stored in the capacitance 145 has been spent during 626 and
628. However,
if a remaining voltage of the capacitance 145 is equal to or above a residual
voltage
threshold, the assisted start procedure returns to operations 626 and 628,
which are still
ongoing, and then at operation 630. In one variant, the residual voltage
threshold applicable
to the assisted start procedure may be the same value VmiriR as in the case of
the electric start
procedure. In another variant, a different residual voltage threshold may be
used given that
the amount of power delivered to the motor-generator 144 by the capacitance
145
complements the effort of the user pulling on the rope 158 of the recoil
starter 156. If
however the ECU 164 determines at operation 632 that the capacitance voltage
has fallen
below the residual voltage threshold Vm,,,R, the method proceeds to operation
634 where the
ECU 164 ceases the delivery of power from the capacitance 145 to the motor-
generator 144
and terminates operations 626 and 628. The method then moves from operation
634 to
operation 614, which is described hereinabove, in which the ECU 164 causes the
display 186
to display a manual start indication, operation 614 being followed by
operations 616, 618,
620 and 622.
[00191] In an implementation, the snowmobile 10 may be configured to support
any one of
the manual, electric and assisted start procedures. In such implementation,
operation 312
(Figure 9) may provide a manual start or an assisted start indication,
depending on the voltage
of the capacitance 145. If the voltage of the capacitance is below the
electric start voltage
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threshold VmmE while meeting or exceeding the assisted start voltage threshold
VmmA,
operation 312 of Figure 9 may provide the assisted start indication and may be
followed by
operation 604 of Figure 11 if the user pulls on the rope 158 of the recoil
starter 156. Also in
this implementation, after having started the ICE 24 using the assisted start
procedure, the
ICE 24 may be stopped and the display 186 may provide an indication of the
available start
procedure depending on current conditions reported to the ECU 164 by the
various sensors.
Implementations of the control strategies
[00192] As expressed hereinabove, the ECU 164 controls the inverter 146
through the
strategy switch 184. To this end, the ECU 164 generates control pulses that
are applied to the
strategy switch 184. These control pulses are generated differently in the two
(2) control
strategies. In at least one implementation, the effect of these control pulses
depends on the
internal structure of the inverter 144. Figure 12 is a circuit diagram showing
connections of
the inverter 146, the capacitance 145 and the motor-generator 144 of Figure 6.
As shown on
Figure 12, the inverter 146 has three phases, each phase being electrically
connected to a
corresponding phase of the three-phase motor-generator 144. In more details,
the inverter 146
is formed of three (3) switching legs, each switching leg including a pair of
MOSFETs Ti,
T2, T3, T4, T5 and T6 matched with corresponding freewheel diodes D2, D1, D3,
D2, D6
and D5. For instance, a first leg forming a first phase includes a top
transistor Ti matched
with a freewheel diode D2 and a bottom transistor T2 matched with a freewheel
diode Dl. A
second leg forming a second phase includes transistors T3 and T4 matched with
diodes D4
and D3 respectively while a third leg forming a third phase includes
transistors T5 and T6
matched with diodes D6 and D5 respectively. As substitutes to MOSFETs, bipolar
transistors, for example IGBTs, or any other power electronic switches are
also contemplated.
Each transistor Ti-T6 has a corresponding gate Gl-G6 through which a signal,
or control
pulse, can be applied under the control of the ECU 164 via the strategy switch
184, either
directly or through a gate driver (not shown), to turn-on (short-circuit) or
turn-off (open
circuit) the corresponding transistors Ti-T6. The freewheel diodes Di-D6 are
used to
attenuate transient overvoltage that occurs upon switching on and off of the
transistors Ti -T6.
[00193] For example, when the motor-generator 144 is in motor operating mode,
being
used as a starter for the ICE 24, a first control pulse is applied at the gate
G1 to short-circuit
the transistor Ti. Current flows from a positive tab of the capacitance 145
through the
transistor Ti and reaches a phase of the motor-generator 144 defined between
an input A and
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a neutral connection between the phases of the motor-generator 144,
hereinafter "Phase A".
Thereafter, the first control pulse is removed from the gate G1 so the
transistor Ti becomes
an open-circuit. At the same time, a second control pulse is applied on the
gate G2, causing
the transistor T2 to turn-on. Current now flows in the opposite direction in
Phase A of the
motor-generator 144, returning to a negative tab of the capacitance 145 via
the transistor T2.
As a result of this sequence of turning on and off the transistors Ti and T2,
an alternating
current flows in the Phase A of the motor-generator 144.
[00194] The current flowing into Phase A of the motor-generator 144 needs to
exit through
one or both of the other phases of the motor-generator 144. "Phase B" is
defined between an
input B and the neutral connection. "Phase C" is defined between an input C
and the neutral
connection. The current flows from Phase A through Phase B, or Phase C, or
both Phases B
and C, depending on whether one or both of transistors T4 or T6 is turned on
by control
pulses applied on their respective gates G4 or G6 when the transistor Ti is
also turned on.
The current exiting the motor-generator 144 via one or both of Phases B and/or
C returns to a
negative tab of the capacitance 145 through one or both of the transistors T4
and/or T6. The
freewheel diodes D 1-D6 assist in supporting phase inductance currents during
freewheel
periods.
[00195] To operate the motor-generator 144 as a conventional three-phase
motor, current
would flow concurrently in all three (3) Phases A, B and C, a timing control
of the various
transistors Ti-T6 being separated by 120 degrees. Other operating modes of the
motor-
generator 144 in which current does not concurrently flow in all three (3)
Phases A, B and C
are however contemplated.
[00196] Examples of parameters that may be considered by programming of the
ECU 164
to control the delivery of electric power in both control strategies include,
without limitation,
current and voltage of each phase voltages and currents in each of the Phases
A, B and C of
the motor-generator 144, the angular position and rotational speed of the
crankshaft 100. The
ECU 164 uses these values to determine an electromagnetic torque of the motor-
generator
144, this torque having positive value when the motor-generator 144 is used
during the
electric start procedure or the assisted start procedure and a negative value
when used in
generator operating mode.
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[00197] The first control strategy uses a technique called vector control.
Suitable examples
of vector control techniques include field-oriented control (FOC), direct-
torque control
(DTC), direct self-control (DSC), space vector modulation (SVM), and the like.
Use of any
one of suitable vector control techniques is contemplated and within the scope
of the present
5 disclosure. The first control strategy is used mainly to control the
delivery of electric power
from the capacitance 145 to the motor-generator 144 to cause or assist a
rotation of the
crankshaft 100 in the electric start procedure or in the assisted start
procedure of the ICE 24.
In one implementation, ECU 164 determines a torque request sufficient to cause
the rotation
of the crankshaft 100. In another implementation, the ECU 164 determines a
speed request
10 applicable to the crankshaft 100, sufficient to cause ignition and start
of the ICE 24. This
determination of the speed request or torque request may be made by the ECU
164 applying a
predetermined speed or torque request value or pattern based on the contents
of the control
maps 166. The ECU 164 may increment the torque request if a first torque
application causes
no rotation of the crankshaft 100. The ECU 164 may increment the speed request
if a rotation
15 of the crankshaft 100 is not sufficient to allow ignition and start of
the ICE 24. Alternatively,
the ECU 164 may calculate the speed or torque request based on a combination
of
parameters, including in a non-limitative example a mathematical
representation of internal
components of the ICE 24 and on the absolute angular position of the
crankshaft 100. The
ECU 164 controls the delivery of electric power from the capacitance 145 to
the motor-
20 generator 144, based on the determined speed request or torque request,
through the
generation of control pulses applied to selected ones of the transistors T1-
T6. Using vector
control, the ECU 164 calculates a number, timing, and width of the various
control pulses so
that the amount of electric power flowing from the capacitance 145 through the
inverter 146
and to the motor-generator 144 fulfills the determined speed or torque
request. This manner
25 of controlling the transistors T1-T6 by applying timed pulses to their
gates G1-G6, each pulse
having a calculated width, is known as pulse width modulation (PWM).
[00198] Figure 13 is a block diagram of a typical implementation of a vector
control drive.
A vector control drive 500 of Figure 13 may be implemented at least in part in
the ECU 164.
An input to the vector control drive includes a set point 504 for a required
speed (the speed
30 request) that is determined as sufficient for starting the ICE 24. This
set point 504 is applied
to a slow speed control loop 506. Other inputs to the vector control drive 500
include current
measurements 508a, 508b and 508e for the three phases of the motor-generator
144 and a
voltage measurement 510 obtained from the inverter 146 and/or from the motor-
generator
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144. These current and voltage measurements are applied to an analog to
digital converter
(ADC) 512. Crankshaft angular position measurements (encoder signals uA, us)
514 that are
obtained from the ACPS 170 are applied to a quadrature timer 516. Because the
motor-
generator 144 is mounted coaxially to the crankshaft 100, the encoder signals
uA, us 514 also
represent the actual angular position of the rotor 150 of the motor-generator
144. The vector
control drive 500 uses this information to calculate a torque request, as
explained in the
following paragraphs. The quadrature timer 516 calculates an actual position
of the
crankshaft 100. The ADC 512 calculates a digitized voltage value 518 and
digitized current
values 520a, 520b and 520, for the three phases of the motor-generator 144.
These digitized
values and an actual position 522 of the crankshaft 100 calculated by the
quadrature timer
516 are provided to a fast current control loop 524. The actual position 522
of the crankshaft
100 is converted to an actual (measured) speed 526 by a speed calculator 528
of the slow
speed control loop 506. A difference 528 between the measured speed 526 and
the required
speed set point 504 is applied to a first proportional-integral (PI)
controller 530 that in turn
yields a current-image 532 of a torque request that is applied as a set point
(Isq_req) to the
fast current control loop 524.
[00199] As expressed hereinabove, in some variants, it may be desired to
operate the
motor-generator 144 so that it delivers electric power to the capacitance 145
in the first
control strategy, at least at low revolution speeds of the crankshaft 100. To
this end, an
optional field weakening module 534 having an internal map attenuates values
of its output
based on the measured speed 526 of the crankshaft 100 to provide a current-
image 536 of a
magnetic field of the motor-generator 144 as an additional set point (Isd_req)
applied to the
fast current control loop 524.
[00200] In the fast current control loop 524, a Clark Transform 538 converts
the three-
phase current measurements 520 a, 520b and 520, into a two-phase model 540. A
Park
Transform 542 fed with sine and cosine values 523 of the actual position 522
of the
crankshaft 100, calculated by a sin/cos converter 525, converts further this
model 540 to
provide a stationary current-image 544 of the actual torque on the motor-
generator 144 (Isq)
and a stationary current-image 546 of the actual magnetic field of the motor-
generator (Isd).
Outputs 544 and 546 of this model are respectively compared to the Isq_req set
point 532 and
to the Isd_req set point 536 (if used), and their differences are respectively
applied to second
and third PI controllers 548, 550. An Inverse Park Transform 552 is applied to
stationary
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voltage requests Uq 554 and Ud 556 produced by the second and third PI
controllers 548,
550, the Inverse Park Transform 552 using the sine and cosine values 523 of
the actual
position 522 of the crankshaft 100 to produce outputs 558, 560 of the Inverse
Park Transform
552 that are applied to a space vector modulation-pulse width modulation (SV-
PWM)
.. transform 562. In turn, the SV-PWM transform 562 provides three-phase
control 564 to a
PWM module 566 that generates pulses 502 that the ECU 164 provides for
application to the
gates G1-G6 of the inverter 146.
[00201] The ECU 164 may control a delivery of electric power from the
capacitance 145 to
the motor-generator 144 based on a pre-determined amount of torque, or torque
request,
sufficient to cause rotation of the crankshaft 100 for starting the ICE 24.
However,
considering that the amount of torque required to rotate the crankshaft 100
before ignition of
the cylinder (or cylinders) varies based on the angular position of the
crankshaft 100 in
relation to the top dead center (TDC) position of each piston, calculation of
a variable torque
request is also contemplated. The absolute angular position of the crankshaft
100 is provided
by the ACPS 170. In a variant introduced in the foregoing description of
operation 326
(Figure 9), the ECU 164 calculates or otherwise determines the torque request
based on the
absolute angular position of the crankshaft 100 provided by the ACPS 170,
values of the
torque request being updated at various points of the rotation of the
crankshaft 100. As a
result, the torque request can be optimized so that it is sufficient to rotate
the crankshaft 100
as it reaches various angular positions while using as little as possible of
the energy stored in
the capacitance 145. In a particular variant, the ECU 164 controls the amount
of torque
applied on the motor-generator 144 so that it turns at a very low speed until
a given piston
116A, 116B passes its TDC for a first time. During this brief period of time,
gas is slowly
expelled from the combustion chamber 120A, 120B in which this given piston
116A, 116B is
.. located. Very little energy is drawn from the capacitance 145 in this
operation. Once the
piston 116A, 116B has moved beyond its TDC, the crankshaft 100 has acquired at
least some
momentum. The ECU 164 then raises the torque request applied to the motor-
generator 144
so that the crankshaft 100 rotates at a speed sufficient to allow injection of
fuel in the
combustion chamber 120A, 120B as the piston 116A, 116B moves towards its TDC,
ignition
taking place in the combustion chamber 120A, 120B as soon as the piston moves
beyond its
TDC. This increase of the torque request may be linear until a predetermined
torque set-point
is reached, so that the rotational speed of the crankshaft 100 increases
smoothly.
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[00202] Following starting of the ICE 24, irrespective of whether the ICE 24
was started
using the manual start procedure, the assisted start procedure or the electric
start procedure,
the crankshaft 100 drives the motor-generator 144 at a variable rotational
speed, most of the
time significantly exceeding a rotational speed used in the course of any of
the start
procedures. Once the ICE 24 is started, operation of the motor-generator 144
switches to
generator operating mode. In an implementation, the ECU 164 may determine a
revolution
speed of the crankshaft 100 based on successive readings provided by the CPS
171 or the
ACPS 170 and cause the motor-generator 144 to start delivering electric power
to the
capacitance 145 when the revolution speed of the crankshaft meets or exceeds a
minimal
revolution threshold. At this point or soon thereafter, the ECU 164 starts
controlling the
strategy switch 184 and the inverter 146 using the second control strategy.
Optionally, the
first control strategy may be used in generator operating mode until the
voltage measurement
provided by the voltage sensor 167 meets or exceeds a voltage generation
threshold. The
voltage generation threshold can be set slightly lower than a nominal voltage
of the
capacitance 145, for example.
[00203] The second control strategy uses a "shunt" technique. The output of
the motor-
generator 144, now generating, is used to charge the capacitance 145, to
supply electrical
power to the direct fuel injectors 132a, 132b, to spark the spark plugs 134a,
134b, and,
generally, to supply electrical power to electrical accessories of the
snowmobile 10. To this
end, the ECU 164 alters a position of the strategy switch 184 so that
electrical power now
flows from the motor-generator 144 to the capacitance 145, still through the
inverter 146. The
ECU 164 monitors the voltage of the capacitance 145 through measurements
obtained from
the voltage sensor 167. Based on these voltage measurements, the ECU 164
generates control
pulses that are applied, via the strategy switch 184, to the gates G1-G6 of
the transistors T1-
T6 in the inverter 146. PWM is still applied by the ECU 164 to the gates G1-
G6, but this time
according to the second control strategy.
[00204] If an output voltage of the motor-generator 144 is above its nominal
value, or
above its nominal value plus a predetermined tolerance factor, the inverter
146 is controlled
by the ECU 164 to reduce the voltage at which electrical power is delivered
from the motor-
.. generator 144 to the capacitance 145. To this end, in one operating mode
called dissipative
voltage regulation mode, the ECU 164 may generate control pulses applied to
various gates
G2, G4 and G6 to effectively bypass, or "shunt", one or more of the phases of
the motor-
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generator 144, at the same time applying no control pulse to the gates G1 , G3
and G5 in order
to cause the transistors Ti, T3 and T5 to remain non-conductive (open
circuit). For example,
applying pulses to the gates G2 and G6 causes the transistors T2 and T6 to
turn on and
become conductive. As a result, a closed loop is formed between Phases A and C
of the
motor-generator 144 along with the transistors T2 and T6. Under this
condition, no electrical
power is delivered from two (2) of the phases of the motor-generator 144 to
the capacitance
145. A duration (width) and timing of the pulses applied to the gates G2 and
G6 impacts a
duration of time when Phases A and C are shunted, in turn impacting the
charging voltage
applied at the capacitance 145. PWM can be applied to any pair of the bottom
transistors T2,
T4 and T6, so that they can be shorted at a desired time to shunt a pair of
phases of the motor-
generator 144. The ECU 164 may actually modify, over time, a determination of
which pair
of transistors is made part of a shunt in order to avoid their overheating due
to conduction
losses in the inverter 146. To this end, voltage regulation in shunt mode
involves successively
activating the transistors T2, T4 and T6. As a result, the delivery of
electric power from the
motor-generator 144 to the capacitance 145 can be made at a desired voltage
over a broad
range of the rotational speed of the crankshaft 100. A series voltage
regulation mode is also
contemplated, in which the freewheel diodes D1, D3 and D5 may optionally be
replaced by
additional transistors (not shown) mounted in reverse-parallel with the
transistors Ti, T3 and
T5, these additional transistors being turned on and off as required to allow
current from the
motor-generator 144 to recharge the capacitance 145 while not exceeding the
nominal voltage
value.
[00205] In a particular implementation, voltage regulation in shunt mode may
benefit from
the measurements provided by the CPS 171 or the ACPS 170. In this
implementation, the
CPS 171 or the ACPS 170 allows the ECU 164 to determine a mechanical position
of the
.. crankshaft 100. The ECU 164 calculates an equivalent electrical angle by
multiplying the
mechanical position of the crankshaft 100 by a known number of pole pairs of
the motor-
generator 144. If the output voltage of the motor-generator 144 is above a
predetermined
value, starting from a voltage rise of any one of the phases A, B or C, all
three (3) phases are
consecutively shunted once, in synchrony with the operation of the motor-
generator 144. This
shunting sequence may be repeated when the output voltage of the motor-
generator 144 rises
again above the predetermined value.
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[00206] If the voltage of the capacitance 145 is at or below its nominal
value, the inverter
146 is controlled by the ECU 164 to deliver electrical power available from
the motor-
generator 144 to the capacitance 145 without shunting any of the Phases A, B
or C. Under
this condition, which may for example occur for a brief duration after the
start of the ICE 24,
5 the control of the power delivery could be construed as a neutral control
mode distinct from
the first and second control strategies. In the neutral control mode, the
inverter146 acts as a
three-phase full-wave diode bridge rectifier, providing no voltage or current
regulation.
[00207] Figure 14 is a block diagram of an electric system according to an
implementation
of the present technology. A circuit 700 includes variants of elements
introduced in the
10 foregoing description of the various drawings, these elements being
grouped into subsystems.
The motor-generator 144 is one such subsystem. Another subsystem is in the
form of a
control module 702 that, in an implementation, comprises a single physical
module including
a processor 703 programmed to execute the functions of the ECU 164, the
inverter 146, the
ECU temperature sensor 182 and further includes a DC-DC converter 704. As
shown, the
15 ECU 164 includes connections for the electric start switch 168, for the
measurements
provided by the various sensors 167, 170, 171, 172, 174, 176 and 182, and
connections to the
gates G1-G6 of the inverter 146. In the illustrated example, the voltage
sensor 167 is
implemented as a DC voltage sensor 167 pc that measures a voltage of the
capacitance 145
and as an AC voltage sensor 167 Ac that measures a voltage on one phase of the
motor-
20 generator 144, these two components of the voltage sensor 167 being
integrated within the
ECU 164. Use of external voltage sensors operatively connected to the ECU 164
is also
contemplated. A third subsystem 706 includes the capacitance 145, as well as a
charging
circuit 705 and a discharging circuit 707 that respectively use the drivers
216 and 217 and the
transistors Q1 and Q2 of Figure 8 to control charging and discharging of the
capacitance 145.
25 .. [00208] The circuit 700 operates at a nominal system voltage, which is
typically the voltage
of the capacitance 145 when fully charged. A fourth subsystem 708 includes
components of
the snowmobile 10 that operate at the system voltage. These components may
include the
direct fuel injectors 132a, 132b, an electric oil pump 710, ignition coils 712
for the spark
plugs 134a, 134b, and a fuel pump 714. A fifth subsystem 716 includes
accessories of the
30 .. snowmobile 10 that operate at an accessory voltage. These accessories
may include a multi-
port fuel injector (MPFI) 718, lighting 720, an instrument cluster 722
including the display
186, heated grips 724 mounted on the handlebar 36 and an exhaust valve 726.
The DC-DC
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convertor 704 converts the system voltage to the accessory voltage and thus
provides electric
power to the accessories.
[00209] In an implementation, the circuit 700 normally operates at a system
voltage of 55
volts and some accessories of the snowmobile normally operate at an accessory
voltage of 12
.. volts. The various sensors 167, 170, 171, 172, 174, 176 and 182 may operate
at the system
voltage or at the accessory voltage, or at any other voltage if an additional
voltage converter
(not shown) is included in the circuit 700. In this implementation, the DC-DC
converter 704
is a 55V-12V converter. These values for the system voltage and for the
accessory voltage are
nominal for this implementation and may vary according to the actual operating
conditions of
the snowmobile 10.
[00210] Figure 15 is a timing diagram showing an example of a sequence for
changing the
control strategy for the delivery of electric power between the capacitance
145 and the motor-
generator 144 along with corresponding engine rotational speed variations. A
graph 410
shows a variation of electrical power delivery control strategies applied by
the ECU 164, as a
function of time, in seconds. In this graph 410, "Strategy 1" indicates the
application of the
first control strategy, specifically using a vector control, "Strategy 2"
indicates the application
of the second control strategy, which uses shunting of phases of the motor-
generator 144 to
control the voltage applied to charge the capacitance 145, and "Neutral"
indicates the
application of the neutral control mode. In the neutral control mode, the
voltage generated by
the motor-generator 144 may simply be converted to direct current and applied
to charge the
capacitance 145, provided that a peak back electromotive force voltage of the
motor-
generator 144 is higher than the nominal voltage of the circuit 200, a
condition that is usually
met when the ICE 24 reaches a sufficient revolution speed. A graph 412 shows a
corresponding variation of a rotational speed of the crankshaft 100 over a
same time scale. In
a first half-second of operation following the user command for the electric
start procedure
for the ICE 24, no power is delivered between the capacitance 145 and the
motor-generator
144. This period is used to equalize the voltages of the capacitance 145 and
of the capacitor
Cl. The actual duration of this period may vary considerably as a function of
the value of the
capacitor Cl. A period ranging from 0.5 to about 1.1 seconds corresponds
essentially to the
period covered between 0 and 0.4 seconds on the graphs 400 and 402. The ECU
164 uses the
first control strategy (Strategy 1) to control delivery of electric power from
the capacitance
145 to the motor-generator 144 until the ICE 24 is actually started. Then,
between 1.1 and 1.3
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seconds, as the ICE 24 accelerates, electric power is delivered from the motor-
generator 144
to the capacitance 145 in the neutral control mode. When the crankshaft 100
reaches a
sufficient rotational speed, at about 1.3 seconds, the motor-generator 144
starts generating
power at a voltage that tends to exceed the nominal voltage of the capacitance
145. This is
when the ECU 164 starts using the second control strategy (Strategy 2) to
control delivery of
electrical power from the motor-generator 144 to the capacitance 145 and to
various electric
loads (not shown) of the vehicle. A variant in which the neutral control mode
is not
implemented is also contemplated, in which the ECU 164 starts using the second
control
strategy as soon as the ICE 24 is successfully started.
[00211] Figure 16 is another timing diagram showing an example of an impact of
the
control strategies on a current exchanged between the capacitance and the ETM
and on a
system voltage. A graph 420 shows a voltage of one of the Phases A, B or C of
the motor-
generator 144 as a function of time, in seconds, and as a function of the
control strategies. In
the first control strategy, the ECU 164 controls the application of voltage
pulses to the motor-
generator 144 in pulse width modulation (PWM) mode, at a very rapid rate
typically
expressed in kilohertz. Then, as ignition of the ICE 24 beings, in the neutral
control mode, the
motor-generator 144 starts generating voltage on its own, this voltage
increasing until the
mode changes to the second control strategy, the voltage cycling at a rate
that follows the
rotation of the crankshaft 100. It may be observed that because of the
configuration of the
inverter 146, the voltage on each phase of the motor-generator alternates
between zero (0)
volt and the nominal system voltage without cycling through negative values. A
graph 422
shows a variation of a current flowing between the capacitance 145 and the
motor-generator
144 as the ECU 164 changes from the first control strategy to the neutral
control mode to the
second control strategy. Initially, in the first control strategy, a three-
phase current flows from
the capacitance 145 toward the motor-generator 144, through the inverter 146.
For most of
the neutral control strategy, all transistors Ti -T6 of the inverter are open
and no current flows
between the capacitance 145 and the motor-generator 144. Significant current
is generated by
each phase of the motor-generator 144 after the start of the ICE 24. The ECU
164 applies
shunting of the phases of the motor-generator 144 for preventing excess
voltage at its output,
as illustrated by the strong variations of the current in the right-hand part
of graph 422. The
graph 424 shows an actual voltage measured on the capacitance 145 as the ECU
164 changes
from the first control strategy to the neutral control mode to the second
control strategy. The
voltage of the capacitance 145 initially decreases while electric power is
delivered to the
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motor-generator 145. Following ignition of the ICE 24, the ECU 164 places the
system in
neutral control mode. A discharge of the freewheel diodes D1-D6 causes a
modest increase of
the voltage of the capacitance 145. Opening of the transistor Q2 at the
beginning of the
operation in the second control strategy temporary isolates the capacitance
145 from the
motor-generator so that electric power produced by the motor-generator is
mainly available
for other needs of the system, such as injection, ignition, control, and the
like. Closing of the
transistor Q1 allows charging of the capacitance 145, with a voltage that
oscillates near the
nominal system voltage according to the shunting of the motor-generator 144.
[00212] The timing values, rotational speed values, and torque values
illustrated in the
various graphs 400, 402, 410, 412, 420, 422 and 424 are provided for
illustration and do not
limit the present disclosure. Actual values may depend greatly on the
construction of the ICE
24, of the motor-generator 144, of the capacitance 145 and on the operation
strategy of the
ECU 164.
Particular application of the first control strategy
[00213] An implementation of the first control strategy, applicable in both
the electric start
procedure and the assisted start procedure, will now be described. As
expressed hereinabove,
the present snowmobile 10 (or other vehicle constructed according to the
teachings of the
present disclosure) includes the ICE 24 equipped with the motor-generator 144
operatively
connected to the crankshaft 100, the capacitance 145, the ECU 164, one direct
fuel injector
132A, 132B in each cylinder 106A, 106B, and the ACPS 170 or an equivalent
sensor that
enables the ECU 164 to be constantly aware of the absolute angular position of
the crankshaft
100, as long as the ACPS 170 and the ECU 164 are energized.
[00214] In an implementation where the ICE 24 is not equipped with a
decompression
system, the capacitance 144 and the motor-generator 145 may not be able to
generate
sufficient torque to rapidly expel gases remaining in the combustion chambers
120A, 102B
after the ICE 24 has stopped. For that reason, an implementation initially
applies a low level
of torque to the crankshaft 100 in order to cause the pistons 116A, 116B to
slowly force
remaining gases out of the combustion chambers 120A, 120B. When a sufficient
portion of
the gases have been expelled, a higher level of torque is applied to the
crankshaft 100 to bring
one of the pistons 116A, 116B at its TDC position and beyond, in order to
start the ICE 24. In
another implementation where the ICE 24 is equipped with a decompression
system (not
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shown), or in a further implementation where the capacitance 145 and the motor-
generator
144 have sufficient torque generating capabilities, the higher level of torque
can optionally be
applied to the crankshaft throughout the procedure.
[00215] In an implementation without a decompression system, when the ICE 24
is
stopped, the pistons 116A, 116B rapidly slow down and tend to terminate their
motion
substantially at a natural point where pressure in the combustion chambers
120A, 120B is
fairly low. In a two-cylinder engine, one of the pistons 116A or 116B usually
stops at about
100 to 80 degrees before TDC because of the configuration of the main and
auxiliary exhaust
ports 136A, 136B, 138A, 138B. When the ICE 24 starts again, that piston 116A
or 116B
initially rotates by moving up, toward its TDC position. In an implementation
as shown for
example on Figures 4A and 4B, the upward movement of the piston (piston 116B
on Figures
4A and 4B) tends to push gases remaining in the combustion chamber 120B to
exit through
the main exhaust port 136B and through the auxiliary exhaust port 138B, some
of the
remaining gases also passing around the at least one ring 117B of the piston
116B, until the
piston 116B arrives at about 50 to 0 degrees before TDC. Because the exhaust
ports 136B,
138B are initially open, until about 60 degrees before TDC, this movement of
the piston
116B requires very little energy. At the same time, the opposite piston 116A
is moving away
from its TDC position and is not compressing, therefore that movement of the
opposite piston
116A is also made with very little energy.
[00216] After the exhaust ports 136B, 138B have closed, the piston 116B starts
compressing any remaining gases in the combustion chamber 120A, a modest
portion of the
remaining gases being expelled around the at least one ring 117A of the piston
116B. More
effort is needed to continue rotating the crankshaft 100 and more torque is
applied starting
when the piston 117B is at about 50 to 0 degrees before TDC.
[00217] Immediately after having passed its TDC position, the piston 116B is
in a proper
position for combustion. Owing to the absolute angular position of the
crankshaft 100
provided by the ACPS 170, the moment when the piston 116B is at its TDC
position is
known with sufficient accuracy for the ECU 164 to control injection of an
amount of fuel,
which may in part be calculated in view of readings from one or more of the
various sensors
167, 170, 171, 172, 174, 176 and 182, in the combustion chamber 120B by the
direct fuel
injector 132B when the piston 116B is in a range between about 3 degrees
before TDC until 7
degrees after TDC and to control ignition of the fuel by the spark plug 134B
thereafter,
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before the piston 116B passes again at its TDC position, for example at about
0 to 12 degrees
after TDC.
[00218] Figure 17 is yet another timing diagram showing an example of a
variation of
torque applied to the ETM during the first control strategy. A graph 430 shows
a variation of
5 a torque delivered to the motor-generator 144 as a function of time, in
seconds. The graph
430 is not to scale. Operation of the ICE 24 in the period shown on the graph
430 is in the
first control strategy as delivery of electric power is from the capacitance
145 to the motor-
generator 144.
[00219] Control of the level of torque applied to the motor-generator 144 may
be effected
10 .. by controlling a current applied through the inverter 146 to the motor-
generator 144. To this
end, the vector control technique described hereinabove, including any one of
its variant, may
use the absolute angular position of the crankshaft 100 to deduce an absolute
angular position
of the rotor 150 of the motor-generator 144, which in turn is used as a basis
to control the
current and, consequently, the level of torque applied by the motor-generator
144 on the
15 crankshaft 100. Referring again to Figure 13, the absolute angular
position of the crankshaft
100 is provided encoded as signals uA, us 514 are applied to a quadrature
timer 516 of the
vector control drive 500.
[00220] In an implementation of the electric start procedure, the ICE 24 is
stopped at an
initial time to (0 sec.) and operations 300, 302, 304, 322, 306, 308 and 310
depicted on Figure
20 9 (some of which are optional) have just been completed. In an
implementation of the
assisted start procedure, the user has initiated a rotation of the crankshaft
100. Operations
600, 602, 604, 606, 608, 610, 612 depicted on Figure 11 (some of which are
optional) have
just been completed at the initial time to. In either cases, the ACPS 170 is
energized and ready
to sense the absolute angular position of the crankshaft 100 (or,
alternatively, an absolute
25 position sensor is sensing the angular position of a component of the
ICE 24 that turns in
synchrony with the crankshaft 100, for example the sensor 177 sending the
angular position
of the water pump 173), either at operation 324, in the case of the electric
start procedure, or
at operation 624 in the case of the assisted start procedure. From this point,
the sequence
shown on graph 430 applies to either procedure. As expressed hereinabove, in a
two-cylinder
30 engine, one of the pistons 116A, 116B usually stops at a predetermined
position, about 100 to
80 degrees before TDC, when stopping the ICE 24 and this condition is present
at the initial
time to.
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[00221] In response to a user command to start the ICE 24, the command being
in the form
of an actuation of the electric start switch 168 or in the form of a pull on
the rope 158 of the
recoil starter 156, the ECU 164 controls the start of electric power delivery
to the motor-
generator 144 in order to rotate the crankshaft 100. The vector control drive
500 controls a
level of torque applied on the rotor 150 of the motor-generator 144. The
torque is first
delivered at a modest level E from the initial time to, where the piston 116B
is at about 100 to
80 degrees before TDC. The torque increases toward a level a until time t1
when the piston is
at about 50 to 0 degrees before TDC. At that time, the piston 116b effectively
blocks the
exhaust ports 136B and 138B and any gas remaining in the combustion chamber
120B will
either be compressed, or expelled at a reduced rate around the at least one
ring 117B. From
this time t1, the vector control drive 500 controls delivery of torque at a
higher level p.
Shortly thereafter, at time t2, the piston is in a range of about 3 degrees
before TDC to 7
degrees after TDC. The ECU 164 causes the direct fuel injector 132B to inject
a calculated
amount of fuel into the combustion chamber 120B. Then, at time t3, the piston
116B being at
about 0 to 12 degrees after TDC, the ECU 164 causes the spark plug 134B to
ignite the fuel
in the combustion chamber 120B. This combustion effectively starts the ICE 24
at time t4 in
many circumstances.
[00222] Of course, starting of the ICE 24 may require continued application of
torque on
the crankshaft 100 by the motor-generator 144, as well as injection and
ignition of fuel in the
combustion chambers 120A, 120B, in a few cycles of operations 326, 328, 330
and 332 of
Figure 9, or in a few cycles of operations 626, 628, 630 and 632 of Figure 11.
The ICE 24 is
deemed started at time t5 when the crankshaft reaches a predetermined
revolution threshold,
for example 600 RPM. The ICE 24 is now in the neutral control mode.
[00223] The torque level a from the initial time to until the time t1 may be
constant. In the
example of Figure 17, the electric power is first delivered from the
capacitance 145 to the
motor-generator 144 at a gradually increasing rate, providing a torque
increasing from a low
level E (which may be zero or slightly above zero) until the level of torque
a, in a range of
one to ten newton-meters (1 to 10 Nm), is reached at time t1. When the piston
116B is at
about 50 to 0 degrees before TDC at time t1, the torque is applied at the
higher level p
sufficient to propel the piston 116B beyond its TDC position, for example in a
range of 10 to
15 Nm. In an implementation, the level of electric power that provides this
torque value p
corresponds to a maximum power delivery capability of the capacitance 145. In
the same or
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another implementation, the level of electric power that provides this torque
value p
corresponds to a maximum power torque value that the motor-generator 144 can
withstand.
The torque values described herein and timing values shown on Figure 17 are
provided as
examples and do not limit the present disclosure. In an implementation where
the ICE 24 is
equipped with a decompression system, the torque may be applied at the higher
level p
starting from the initial time to until the ICE 24 is properly started.
[00224] Figure 18 is a sequence diagram showing operations of a method for
starting an
internal combustion engine. A sequence shown in Figure 18 comprises a
plurality of
operations, some of which may be executed in variable order, some of the
operations possibly
.. being executed concurrently, and some of the operations being optional. The
sequence of
Figure 18 is implemented in the ICE 24 which has the motor-generator 144
operatively
connected to the crankshaft 100. The sequence corresponds, in one
implementation, to
operations 324, 326, 328 and 330 of Figure 9 and, in the same or another
implementation, to
operations 624, 626, 628 and 630 of Figure 11. In order to ease the
illustration and without
.. loss of generality, the sequence is described in a case where the piston
116B is at a
predetermined position of about 100 to 80 degrees before TDC, at a time where
one of the
electric start or assisted start procedure is initiated by the user. The
crankshaft 100 is at the
time not rotating (electric start procedure) or just barely starting to rotate
(assisted start
procedure). Initial injection and ignition will take place in the combustion
chamber 120B
corresponding to the piston 116B. At that time, the opposite piston 116A is at
about 80 to 100
degrees after TDC and will initially move away from TDC, not compressing any
gas in the
combustion chamber 120A.
[00225] The sequence starts at operation 800 when an absolute position sensor,
for example
the ACPS 170, is energized so to be able determine the absolute angular
position of the
crankshaft 100 when the ICE 24 is stopped or starting to rotate. The ACPS 170
will continue
being energized when the crankshaft 100 is rotating. An absolute angular
position of the
crankshaft 100 is determined at operation 802, the absolute angular position
of the crankshaft
100 being related to a TDC position of the piston 116B in the combustion
chamber 120B of
the ICE 24. As expressed hereinabove, the ACPS 170 may be substituted by
another absolute
angular position sensor (not shown) that senses an absolute angular position
of a component
of the ICE 24 that rotates in synchrony with the crankshaft 100. In any case,
the ECU 164
calculates the absolute angular position of the crankshaft 100 based on a
reading provided by
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the ACPS 170 or based on the sensed absolute angular position of the component
of the ICE
that rotates in synchrony with the crankshaft 100. At operation 804, when the
ICE 24 is not
equipped with a decompression system, electric power starts being delivered
from the
capacitance 145 to the motor-generator 144 at a first level to rotate the
crankshaft 100.
Optionally, the operation 804 may include a sub-operation 806 in which the
delivery of
electric power to the motor-generator 145 gradually increases from an initial
level E to the
first level, as illustrated on Figure 17 between times to and t1. The first
level, and in particular
the initial level E and a slope of the power delivery between times to and t1
may be determined
based on the initial angular position of the crankshaft 100. The first level
of electric power
delivery is calculated so that the motor-generator 145 generates sufficient
torque to rotate the
crankshaft 100 until the piston 116B reaches a predetermined position before
the TDC
position, for example between 50 to 0 degrees before TDC. At operation 808,
electric power
is then delivered from the capacitance 145 to the motor-generator 144 at a
second level
greater than the first level when the piston reaches 116B the predetermined
position before
the TDC position. The second level of electric power delivery is calculated so
that the motor-
generator 145 generates sufficient torque to cause the piston to move beyond
the TDC
position. In more details, the vector control drive 500 deduces an angular
position of the rotor
150 of the motor-generator 145 from the angular position of the crankshaft
100. The angular
position of the rotor 150 is used in the vector control drive 500 to
calculate, at first, the torque
value sufficient to bring the piston 116B to the predetermined position before
the TDC
position and then to calculate the torque value sufficient to cause the piston
to move beyond
the TDC position. The first and second levels of electric power delivery are
calculated based
on these torque values.
[00226] In an implementation of the ICE 24 equipped with a decompression
system,
electric power may be delivered by the capacitance 145 to the motor-generator
144 already at
the second level in the course of operation 804. In that case, operations 804
and 808 may be
considered as essentially merged into a same operation.
[00227] In any case, fuel is injected at operation 810 in the combustion
chamber 120B of
the ICE 24 after the piston 116B has passed beyond the TDC position a first
time. In an
implementation, injection takes place in a range of about 3 degrees before TDC
to 7 degrees
after TDC. Given that fuel has been directly injected in the combustion
chamber 120B, the
fuel is immediately available in the combustion chamber 120B. Consequently,
the fuel is
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ignited without delay at operation 812. A timing of the ignition operation 812
may vary but
will take place before the piston 116B passes the TDC position a second time.
In one
implementation, ignition takes place before a downward motion of the piston
116B causes an
opening of the exhaust ports 136B, 138B, as the crown of the piston 116B
reaches the top of
a first one of the exhaust ports 136B, 138B. In another implementation,
ignition takes place
about 2 degrees of rotation after injection, in a range of 0 to 12 degrees
after TDC.
[00228] Frequently, the ICE 24 will start after performing the injection and
ignition
operations 810 and 812 a single time. This will be determined at operation 330
of Figure 9, in
the case of an electric start, or at operation 630 of Figure 11, in the case
of an assisted start,
by detecting that a rotational speed of the crankshaft 100 calculated by the
ECU 164 based on
readings form the CPS 171 has reached a minimum threshold. The delivery of
electric power
to the motor-generator 144 is stopped at operation 814 after starting the ICE
24. In cases
where the ICE 24 is not started after operation 812, the sequences of Figures
9 or 11, as
applicable, may continue.
[00229] Figure 19 is a sequence diagram showing operations of a method for
controlling
delivery of electric power between a power source and the ETM. A sequence
shown in Figure
19 comprises a plurality of operations, some of which may be executed in
variable order,
some of the operations possibly being executed concurrently, and some of the
operations
being optional. The sequence of Figure 19 is implemented in the ICE 24 which
has the
motor-generator 144 electrically connected to the capacitance 145, as shown
for instance on
Figure 8. The sequence may start at operation 902 when a start signal 221 is
applied to
transistor Q2, which is a start-up power electronic switch, to cause turning
on of transistor
Q2, allowing delivery of electric power from the capacitance 145 to the motor-
generator 144
via the transistor Q2. As shown on Figure 8, the start signal 221 may be
applied to the driver
217 that, in turn, applies the start signal to the transistor Q2. Application
of the start signal
221 may be terminated at operation 904, turning off the transistor Q2 before
the next
operation. Then at operation 906, a recharge signal 222 is applied to the
transistor Q1 , which
is a run-time power electronic switch, to cause turning on of the transistor
Q1 , allowing
delivery of electric power from the motor-generator 144 to the capacitance 145
via the
transistor Q1 and, optionally, via the current limiting circuit 224. The
recharge signal 222
may be applied to the driver 216 that, in turn, applies the recharge signal to
the transistor Ql.
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[00230] In an implementation, the transistor Q2 is repeatedly turned on and
off at operation
902 for instance by repeatedly applying and releasing the start signal 221 to
the driver 217, in
order to limit the delivery of electric power from the capacitance 145 to the
motor-generator
144. In a variant, this repeated application and release of the start signal
221 is performed
5 under the control of the ECU 164 according to a PWM mode.
[00231] In an implementation in which the capacitor Cl and the current
limiting circuit 224
are provided, operation 900 may precede operation 902. In operation 900, an
initiation signal
220 is briefly applied and then released to turn on the transistor Q1 so that
the capacitance
145 starts charging the capacitor Cl while the current limiting circuit 224
protects the
10 transistor Q1 from excessive current flowing therethrough. As soon as a
voltage starts being
established in the capacitor Cl, operation 900 ends, causing the transistor Q1
to turn off, and
the sequence continues with operation 900 as expressed hereinabove.
[00232] The methods, systems and internal combustion engines implemented in
accordance
with some non-limiting implementations of the present technology can be
represented as
15 follows, presented in numbered clauses.
[00233] Modifications and improvements to the above-described implementations
of the
present technology may become apparent to those skilled in the art. For
example, it is
contemplated that the ICE 24 could be provided with a decompression system.
The
decompression system can release pressure in the combustion chambers 120A,
120B, thereby
20 reducing compression forces that need to be overcome by the motor-generator
144 at
operations 326 and 626 described above. Therefore, by providing a
decompression system, it
is contemplated that the motor-generator 144 could be even smaller and
lighter, a size and a
weight of the capacitance 145 being reduced accordingly. Also, when a
decompression
system is provided, the sequence of Figure 18 may be modified by delivering
electric power
25 to the motor-generator already at the higher, second level starting at
operation 804. The
foregoing description is intended to be exemplary rather than limiting. The
scope of the
present technology is therefore intended to be limited solely by the scope of
the appended
claims.
Clauses
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[Clause 1] A method for starting an internal combustion engine (ICE) having a
crankshaft
and an electric turning machine (ETM) operatively connected to the crankshaft,
the method
comprising:
determining an absolute angular position of the crankshaft, the absolute
angular
position of the crankshaft being related to an angular position of a rotor of
the ETM;
delivering electric power to the ETM at a first level to rotate the
crankshaft; and
delivering electric power to the ETM at a second level greater than the first
level
when the rotor of the ETM reaches a predetermined angular position.
[Clause 2] The method of clause 1, further comprising:
calculating the first level of electric power delivery so that the ETM
generates
sufficient torque to rotate the crankshaft until the rotor reaches the
predetermined angular
position; and
calculating the second level of electric power delivery so that the ETM
generates
sufficient torque to rotate the crankshaft beyond the predetermined angular
position of the
rotor.
[Clause 3] The method of clause 2, wherein:
calculating the first level of electric power delivery comprises using a
vector control
of the delivery of electric power at the first level based on a
predetermination of the sufficient
torque to rotate the crankshaft until the rotor reaches the predetermined
angular position; and
calculating the second level of electric power delivery comprises using a
vector
control of the delivery of electric power at the second level based on a
predetermination of
the sufficient torque to rotate the crankshaft beyond the predetermined
angular position of the
rotor.
[Clause 4] The method of any one of clauses 1 to 3, further comprising
energizing an
absolute position sensor used to determine the absolute angular position of
the crankshaft
when the ICE is stopped.
[Clause 5] The method of clause 4, further comprising energizing the absolute
position sensor
when the crankshaft is rotating.
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[Clause 6] The method of any one of clauses 1 to 5, further comprising
gradually increasing
the delivery of electric power to the ETM from an initial level to the first
level before
delivering electric power to the ETM at the second level.
[Clause 7] The method of any one of clauses 1 to 6, wherein the absolute
angular position of
the crankshaft is further related to a position of a piston in a combustion
chamber of the ICE
in relation to a top dead center (TDC) position of the piston.
[Clause 8] The method of clause 7, wherein:
delivering electric power to the ETM at the second level starts when the
piston
reaches a predetermined position before the TDC position; and
the method further comprises injecting fuel in the combustion chamber of the
ICE
when the piston passes the TDC position a first time and igniting the fuel in
the combustion
chamber.
[Clause 9] The method of clause 8, further comprising determining the first
level of the
electric power delivered to the ETM based on an initial angular position of
the crankshaft.
[Clause 10] The method of clause 9, wherein the initial angular position of
the crankshaft is a
position of the crankshaft when the ICE is stopped.
[Clause 11] The method of any one of clauses 9 or 10, wherein the initial
angular position is
in a range between 80 and 100 degrees before the TDC position.
[Clause 12] The method of any one of clauses 8 to 11, wherein delivering the
electric power
to the ETM before the piston reaches the predetermined position before the TDC
position
causes gases to be expelled from the combustion chamber.
[Clause 13] The method of clause 12, wherein the predetermined position before
the TDC
position is determined according to a configuration of exhaust ports of the
ICE.
[Clause 14] The method of any one of clauses 8 to 13, wherein the
predetermined position
before the TDC position in a range between 0 and 50 degrees before the TDC
position.
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[Clause 15] The method of any one of clauses 8 to 14, further comprising
terminating the
delivery of electric power to the ETM after starting the ICE.
[Clause 16] The method of clause 15, wherein the delivery of electric power to
the ETM is
terminated when a rotational speed of the crankshaft reaches a minimum
threshold.
[Clause 17] The method of any one of clauses 8 to 16, wherein the fuel is
ignited before the
piston passes the TDC position a second time.
[Clause 18] The method of any one of clauses 8 to 17, wherein the fuel is
injected in the
combustion chamber when the position of the piston passes a range between 3
degrees before
the TDC position and 7 degrees after the TDC position.
[Clause 19] The method of any one of clauses 8 to 18, wherein the fuel is
ignited when the
position of the piston is in a range between 0 and 12 degrees after the TDC
position, ignition
of the fuel taking place after injection of the fuel.
[Clause 20] The method of any one of clauses 8 to 19, wherein ignition takes
place before the
piston reaches the top of an exhaust port in the combustion chamber of the ICE
[Clause 21] The method of any one of clauses 8 to 20, wherein:
the first level of electric power delivery is calculated so that the ETM
generates
sufficient torque to rotate the crankshaft until the piston reaches the
predetermined position
before the TDC position; and
the second level of electric power delivery is calculated so that the ETM
generates
sufficient torque to cause the piston to move beyond the TDC position.
[Clause 22] The method of any one of clauses 1 to 21, wherein determining the
absolute
angular position of the crankshaft comprises sensing the absolute angular
position of the
crankshaft.
[Clause 23] The method of any one of clauses 1 to 21, further comprising:
sensing an absolute angular position of a component of the ICE that rotates in
synchrony with the crankshaft, wherein the component of the ICE that rotates
in synchrony
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with the crankshaft is selected from the rotor of the ETM, a fuel pump, an oil
pump, a water
pump, a camshaft, and a balance shaft; and
calculating the absolute angular position of the crankshaft based on the
sensed
absolute angular position of the component of the ICE that rotates in
synchrony with the
crankshaft.
[Clause 24] A system for starting an internal combustion engine (ICE) having a
crankshaft,
the system comprising:
a power source;
an electric turning machine (ETM) adapted for being mounted to the crankshaft;
an absolute position sensor adapted for providing an indication of an absolute
angular
position of the crankshaft, the absolute angular position of the crankshaft
being related to an
angular position of a rotor of the ETM; and
an engine control unit (ECU) operatively connected to the absolute position
sensor,
the ECU being adapted for determining the absolute angular position of the
crankshaft based
on the indication provided by the absolute position sensor, the ECU being
further adapted for
controlling:
a delivery of electric power from the power source to the ETM at a first level
to rotate the crankshaft;
a delivery of electric power from the power source to the ETM at a second
level greater than the first level when the rotor of the ETM reaches a
predetermined angular position.
[Clause 25] The system of clause 24, wherein the ECU is further adapted for:
calculating the first level of electric power delivery so that the ETM
generates
sufficient torque to rotate the crankshaft until the rotor reaches the
predetermined angular
position; and
calculating the second level of electric power delivery so that the ETM
generates
sufficient torque to rotate the crankshaft beyond the predetermined angular
position of the
rotor.
[Clause 26] The system of clause 25, wherein:
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the ECU implements a vector control of the delivery of electric power at the
first level
based on a predetermination of the sufficient torque to rotate the crankshaft
until the rotor
reaches the predetermined angular position; and
the ECU implements a vector control of the delivery of electric power at the
second
5 level based on a predetermination of the sufficient torque to rotate the
crankshaft beyond the
predetermined angular position of the rotor.
[Clause 27] The system of any one of clauses 24 to 26, wherein the absolute
angular position
of the crankshaft is further related to a position of a piston in a combustion
chamber of the
10 ICE in relation to a top dead center (TDC) position of the piston.
[Clause 28] The system of clause 27, wherein:
the delivery of electric power from the power source to the ETM at the second
level
starts when the piston reaches a predetermined position before the TDC
position; and
15 the ECU
is further adapted for controlling an injection of fuel in the combustion
chamber of the ICE when the piston passes the TDC position a first time, and
for controlling
ignition of the fuel in the combustion chamber.
[Clause 29] The system of any one of clauses 24 to 28, wherein the ETM is
adapted for being
20 coaxially mounted to the crankshaft.
[Clause 30] The system of any one of clauses 24 to 29, wherein the absolute
position sensor
is adapted for sensing the absolute angular position of the crankshaft.
25 [Clause 31] The system of any one of clauses 24 to 29, wherein:
the absolute position sensor is adapted for sensing an angular position of a
component
of the ICE that rotates in synchrony with the crankshaft, wherein the
component of the ICE
that rotates in synchrony with the crankshaft is selected from the rotor of
the ETM, a fuel
pump, an oil pump, a water pump, a camshaft, and a balance shaft; and
30 the ECU
is adapted for calculating the absolute angular position of the crankshaft
based
on the sensed absolute angular position of the component of the ICE that
rotates in synchrony
with the crankshaft and based on a mechanical relationship between the
crankshaft of the
component of the ICE that rotates in synchrony with the crankshaft.
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[Clause 32] The system of any one of clauses 24 to 31, wherein the absolute
position sensor
is permanently connected to the power source.
[Clause 33] The system of any one of clauses 24 to 31, wherein the absolute
position sensor
is energized by the power source at the onset of a start procedure for the
ICE.
[Clause 34] An internal combustion engine (ICE) comprising:
a crankshaft;
a first cylinder;
a cylinder head connected to the first cylinder;
a piston operatively connected to the crankshaft and disposed in the first
cylinder, the
first cylinder, the cylinder head and a crown of the first piston defining a
first variable
volume combustion chamber therebetween; and
the system of any one of clauses 24 to 33, wherein the absolute angular
position of the
crankshaft is related to a position of the first piston in the first
combustion chamber.
[Clause 35] The ICE of clause 34, further comprising:
a direct fuel injector operatively connected to the ECU; and
an ignition system operatively connected to the ECU;
wherein the ECU is adapted for causing the direct fuel injector to inject the
fuel in the
first combustion chamber and for causing the ignition system to ignite the
fuel.
[Clause 36] The ICE of any one of clauses 34 or 35, further comprising:
a second cylinder; and
a second piston operatively connected to the crankshaft and disposed in the
second
cylinder, the second cylinder, the cylinder head and a crown of the second
piston defining a
second variable volume combustion chamber therebetween;
wherein when the first piston compresses gases in the first combustion
chamber, the
second piston expands the volume of the second combustion chamber.
[Clause 37] A method for starting an internal combustion engine (ICE) having a
crankshaft
and an electric turning machine (ETM) operatively connected to the crankshaft,
the method
comprising:
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energizing an absolute position sensor adapted for providing an indication of
an
angular position of a rotor of the ETM; and
applying a current to the ETM to generate a sufficient torque to rotate the
crankshaft.
[Clause 38] The method of clause 37, wherein:
the absolute position sensor provides the indication of the angular position
of the rotor
of the ETM in signals sent to a controller; and
the controller calculates on an ongoing basis the actual angular position of
the rotor of
the ETM based on the signals from the absolute position sensor.
[Clause 39] The method of any one of clauses 37 or 38, wherein applying a
current to the
ETM further comprises:
initially applying a first current to the ETM; and
subsequently applying to the ETM a second current greater than the first
current when
the angular position of the rotor of the ETM passes beyond a predetermined
angular position.
[Clause 40] The method of any one of clauses 37 to 39, further comprising
receiving at a
controller a start command for the ICE.
[Clause 41] The method of any one of clauses 37 to 40, further comprising:
determining an initial angular position of the rotor of the ETM; and
determining a first amount of torque to be supplied by the ETM to the
crankshaft
based in part on the initial angular position of the rotor of the ETM.
[Clause 42] The method of clause 41, further comprising:
determining a second angular position of the rotor of the ETM, the second
angular
position indicating that the rotor of the ETM has passed a first predetermined
angular
position; and
determining a second amount of torque to be supplied by the ETM to the
crankshaft
based in part on the second angular position of the rotor of the ETM, the
second amount of
torque being greater than the first amount of torque.
[Clause 43] The method of clause 42, further comprising:
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determining a third angular position of the rotor of the ETM, the third
angular position
indicating that the rotor of the ETM has passed a second predetermined angular
position, the
second predetermined angular position being a top dead center (TDC) position
of a piston
within a combustion chamber; and
injecting fuel in the combustion chamber of the ICE.
[Clause 44] The method of clause 43, further comprising:
determining a fourth angular position of the rotor of the ETM, the fourth
angular
position indicating that the rotor of the ETM has passed a third predetermined
angular
position, the third predetermined angular position being after the second
predetermined
angular position; and
igniting the fuel in the combustion chamber of the ICE.
[Clause 45] The method of clause 44, wherein the fourth angular position is
less than 110
degrees of rotation of the crankshaft beyond the initial angular position.
[Clause 46] The method of clause 44, wherein the fourth angular position is
selected so that
ignition takes place before opening of an exhaust port in the combustion
chamber of the ICE.
[Clause 47] An internal combustion engine (ICE), comprising:
a crankshaft;
a cylinder head defining in part a variable combustion chamber of the ICE;
a direct fuel injector mounted on the cylinder head;
a power source;
an electric turning machine (ETM) adapted for rotating the crankshaft;
an absolute position sensor adapted for providing an indication of an angular
position
of a rotor of the ETM; and
an engine control unit (ECU) operatively connected to the absolute position
sensor,
the ECU being adapted for:
vector controlling a delivery of electric power from the power source to the
ETM based on the angular position of the rotor of the ETM; and
causing the direct fuel injector to inject fuel directly in the combustion
chamber at a time selected based on the angular position reached by the rotor
of
the ETM.
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[Clause 48] The ICE of clause 47, wherein the ECU causes the delivery of
electric power
from the power source to the ETM to generate a first level of torque until the
rotor of the
ETM reaches a first predetermined position and then to generate a second level
of torque
greater than the first level of torque as the rotor of the ETM rotates beyond
the first
predetermined position.
[Clause 49] The ICE of clause 48, wherein the ECU causes the direct fuel
injector to inject
fuel directly in the combustion chamber after the ETM has reached the first
determined
position.
[Clause 50] The ICE of clause 49, wherein the absolute angular position of the
rotor of the
ETM is related to a position of a piston in the combustion chamber, injection
of the fuel
taking place when the piston passes at a top dead center position within the
combustion
chamber.
[Clause 51] The ICE of clause 50, wherein the ECU causes an ignition of the
fuel after
injection of the fuel.
[Clause 52] A method for controlling delivery of electric power between a
power source and
an electric turning machine (ETM), the method comprising:
applying a start signal to a start-up power electronic switch to cause turning
on of the
start-up power electronic switch and to allow delivery of electric power from
the power
source to the ETM via the start-up power electronic switch; and
applying a recharge signal to a run-time power electronic switch to cause
turning on
of the run-time power electronic switch and to allow delivery of electric
power from the ETM
to the power source via the run-time power electronic switch.
[Clause 53] The method of clause 52, further comprising ceasing application of
the start
signal to the start-up power electronic switch when applying the recharge
signal to the run-
time power electronic switch.
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[Clause 54] The method of any one of clauses 52 or 53, wherein turning on of
the start-up
power electronic switch further comprises repeatedly turning on and off the
start-up power
electronic switch to limit the delivery of electric power from the power
source to the ETM.
5 [Clause 55] The method of clause 54, wherein the start signal is
repeatedly applied and
released to cause repeatedly turning on and off the start-up power electronic
switch.
[Clause 56] The method of clause 55, wherein the start signal is varied
according to a pulse
width modulation mode.
[Clause 57] The method of any one of clauses 52 to 56, further comprising
providing a
current limiting circuit connected in series with the run-time power
electronic switch to limit
delivery of electric power from the ETM to the power source.
[Clause 58] The method of clause 57, further comprising, before applying the
start signal to
the start-up power electronic switch, applying and then releasing an
initiation signal to the
run-time power electronic switch.
[Clause 59] The method of any one of clauses 52 to 58, wherein the start
signal is applied to
the start-up power electronic switch via a first driver and wherein the
recharge signal is
applied to the run-time power electronic switch via a second driver.
[Clause 60] A circuit comprising:
a discharging circuit comprising a start-up power electronic switch adapted
for
allowing delivery of electric power from a power source to an electric turning
machine
(ETM) via the start-up power electronic switch when the start-up power
electronic switch is
turned on; and
a charging circuit comprising a run-time power electronic switch adapted for
allowing
delivery of electric power from the ETM to the power source via the run-time
power
electronic switch when the run-time power electronic switch is turned on.
[Clause 61] The circuit of clause 60, wherein:
the discharging circuit further comprises a first driver adapted for receiving
a start
signal and to forward the start signal to the start-up power electronic
switch; and
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the charging circuit further comprises a second driver adapted for receiving a
recharge
signal and to forward the recharge signal to the run-time power electronic
switch.
[Clause 62] The circuit of clause 61, further comprising a control unit
adapted for applying
the start signal to the first driver and for applying the recharge signal to
the second driver.
[Clause 63] The circuit of clause 62, wherein the control unit is further
adapted for ceasing
application of the start signal to the start-up power electronic switch when
applying the
recharge signal to the run-time power electronic switch.
[Clause 64] The circuit of any one of clauses 62 or 63, wherein the control
unit is further
adapted for repeatedly applying and releasing the start signal to the first
driver to limit the
delivery of electric power from the power source to the ETM.
[Clause 65] The circuit of clause 64, wherein the control unit is further
adapted for varying
the start signal according to a pulse width modulation mode.
[Clause 66] The circuit of any one of clauses 60 to 65, wherein the charging
circuit further
comprises a current limiting circuit connected in series with the run-time
power electronic
switch and adapted for limiting delivery of electric power from the ETM to the
power source.
[Clause 67] The circuit of clause 66, wherein the control unit is further
adapted for applying
and then releasing an initiation signal to the run-time power electronic
switch before applying
the start signal to the start-up power electronic switch.
