Note: Descriptions are shown in the official language in which they were submitted.
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FRONT END MOTOR-GENERATOR SYSTEM AND
HYBRID ELECTRIC VEHICLE OPERATING METHOD
BACKGROUND OF THE INVENTION
100011 The present invention relates to hybrid electric vehicles, and in
particular to a system
for selective coupling of a hybrid electric generating and storage system with
an internal
combustion engine. The present invention further relates to a method of
operating the system.
BACKGROUND OF THE INVENTION
100021 Hybrid electric vehicles having an internal combustion engine combined
with a motor-
generator and an electrical energy storage system have been the focus of
considerable attention
in the automotive field, particularly in the field of passenger vehicles.
Development of hybrid
electric vehicle systems has only recently begun to attract significant
interest in commercial and
off-road vehicles, e.g., trucks and busses in Vehicle Classes 2-8, in earth-
moving equipment and
railroad applications, and in stationary internal combustion engine-powered
installations.
[0003] Hybrid electric technologies offer numerous advantages, including
improvements in
fuel efficiency, reduction in internal combustion engine emissions and vehicle
noise to help meet
government regulatory requirements, improved vehicle performance and lower
fleet operating
costs. These advantages are obtained in significant part by hybrid electric
systems' ability to
recapture energy which would otherwise be wasted (such as mechanical energy
from braking that
would otherwise be dissipated as thermal energy to the environment) and return
of the captured
energy at another time when needed, such as powering vehicle components in
lieu of using the
internal combustion engine as the source of power or assisting in vehicle
propulsion.
[0004] Typically, hybrid electric vehicle motor-generators have been arranged
either
independently of the internal combustions engine (for example, using separate
electric motors to
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power and recover energy from front wheels while the engine provides
propulsion power to the
rear wheels), or have been coupled to the engine, for example being integrated
into the "rear" of
the engine (i.e., the end at which the engine's flywheel is located) or
between the engine and the
driveline to the wheels. This "behind the engine" position permits the motor-
generator
equipment to deliver torque directly to the vehicle's driveline and wheels,
and to be directly
driven by the driveline, for example, during regenerative braking events.
Examples of the latter
include flywheel-type motor-generators in which a conventional engine's
flywheel is modified to
serve as a motor-generator rotor and a concentrically-mounted stator is
located around the
flywheel, and separate electric motors arranged between the engine and the
drive wheels, such as
the so-called "two mode hybrid" transmission offered by General Motors in the
2009 GMC
Silverado light-duty pickup in which the transmission accommodated two
electric motors for
vehicle propulsion and electric energy generation.
100051 Another form of adding a motor-generator to an internal combustion
engine is the use
of so-called starter-generators. This approach directly couples an electric
motor to an engine to
serve both as an electric generator (a function traditionally performed by a
conventional belt-
driven alternator) and as an engine starter, thereby reducing the weight and
cost of duplicate
alternator and starter electric motors. Such starter-generator installations
are particularly useful
in so-called engine stop-start systems which turn off the engine during
periods when the vehicle
is stopped to save fuel and reduce idling emissions. Starter-generators have
been located behind
the engine (for example, an appropriately engineered flywheel motor-generator
may also be used
as a starter), as well as being mounted at the front end of an engine where
the starter-generator
can drive a belt directly coupled to the engine crankshaft. An example of the
latter system the
"belt alternator starter" system that was offered by General Motors as an
option in the 2007
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Saturn Vue sport-utility vehicle. These systems are very difficult to adapt to
large engines, such
as commercial vehicle diesel engines, because the electric motor must be
larger to deal with the
much higher torque demands of these heavy-duty engines, such as starting and
operating various
components ( for example, an engine cooling fan can demand upwards of 50 KW of
power, a
load that requires a large amount of torque to drive the fan belt). Further,
the belt drive in such
an enlarged system would need to have the capacity to transfer the large
levels of torque,
something that may not be possible, or at least practical, because thicker and
broader drive belts
and pulleys sufficient to handle the torque demands may be so much larger and
heavier than their
automotive counterparts that they are weight, size and/or cost prohibitive.
[0006] Another approach to electrification is to use multiple individual
electric motors to
individually drive energy-consuming engine and vehicle accessories such as air
conditioner
compressors, power steering pumps, air compressors, engine cooling fans and
coolant pumps, in
order to reduce fuel consumption by removing the accessory loads from the
engine. This
approach significantly increases vehicle weight, cost, and wiring harness and
control system line
lengths and complexity, potentially offsetting fuel economy or emissions
reduction gains
provided by removing engine accessory loads from the engine.
[0007] The prior art hybrid electric vehicle systems have a number of
disadvantages that have
hindered their adoption in applications such as commercial vehicles. These
include: engineering
difficulties associated with attempting to scale up hybrid electric drive
train components to
handle the very high torque output of large engines (typically high-torque
output diesel engines);
the interdependence of the engine and motor-generator operation as a result of
these components
being either integral to the rear of the engine or directly in the drive line
(i.e., both the engine and
the motor-generator must rotate together, even when rotation of one or the
other is not needed or
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even detrimental to overall vehicle operating efficiency); and the inability
to independently meet
"hotel" loads (e.g., overnight climate control and 120 volt power demands in a
commercial
vehicle tractor sleeper compartment) without either operating the vehicle's
engine or operation of
a separate vehicle-mounted auxiliary power unit ("APU"), such as a dedicated
self-contained
internal combustion engine package or a dedicated battery package containing
multiple-
conventional batteries and associated support equipment. These auxiliary power
units are very
costly (typically several thousand dollars), heavy and demand a considerable
amount of space on
an already space-constrained vehicle. They also have further disadvantages of,
in the case of a
fuel combusting APU, the potential hazards associated with open flames and
generating carbon
monoxide that could enter the sleeper compartment during driver rest periods,
and in the case of
a full electric APU, may not being able to return sufficient energy to supply
all of the vehicle's
accessory demands for extended periods with the vehicle engine shut down.
SUMMARY OF THE INVENTION
100081 Overview of Primary Front End Motor-Generator System Components.
100091 The present invention solves these and other problems by providing a
hybrid electric
vehicle system located at a front end of an engine, with a motor-generator
being arranged in a
manner that requires little or no extension of the length of the front of the
vehicle. As used in
this description, the "front end" of the engine is the end opposite the end
from which engine-
generated torque output is transferred to the primary torque consumers, such
as a vehicle's
transmission and drive axles or a stationary engine installation's load, such
as a pump drive.
Typically, the rear end of an engine is where the engine's flywheel is
located, and the front end is
where components such as engine-driven accessories are located (e.g., air
conditioning and
compressed air compressors, engine cooling fans, coolant pumps, power steering
pumps). While
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the discussions that follow focus primarily on commercial vehicle embodiments
in which the
engine crankshaft is aligned with the longitudinal axis of the vehicle, the
present invention is not
limited to front-engine, longitudinally-aligned engine applications, but also
may be used with
transverse-mounted engines (including transverse-mounted engines located at
the front or rear of
a vehicle) which may also have highly space-constrained environments in the
region adjacent to
the end of the engine opposite the flywheel end.
100101 Preferably, the front end motor-generator system of the present
invention has the
motor-generator located in the front region of the engine, laterally offset to
the side of the
rotation axis of the engine crankshaft. The motor-generator is preferably
supported on a torque
transfer segment (also referred to as a "drive unit"), for example a narrow-
depth single reduction
parallel shaft gearbox arranged with its input rotation axis co-axial with the
engine crankshaft.
The motor-generator preferably is positioned either behind the torque transfer
segment in a space
between the engine and an adjacent longitudinal vehicle chassis frame member,
or in front of the
torque transfer segment in a space below the vehicle's coolant radiator. The
present invention is
not limited to these locations for the motor-generator, but it instead may be
located anywhere in
the region near the front of the engine as long as the torque transfer segment
on which it is
mounted can align with the engine crankshaft rotation axis.
100111 Preferably the torque transfer segment also provides a suitable speed
ratio between its
input and outputs (e.g., a 2:1 ratio) to better adapt engine and motor-
generator speeds to one
another, i.e., providing a speed increase from the engine to the motor-
generator and speed
reduction from the motor-generator output. The torque transfer segment may be
a gearbox with
gears or another drive arrangement, such as a chain belt, on a motor-generator
side of a
disengageable coupling (discussed further, below) between the engine
crankshaft and the torque
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transfer segment that transfers torque between the motor-generator end and the
engine end of the
torque transfer segment. The torque transfer segment has an axially-narrow
profile to permit it to
be accommodated between the front of the engine crankshaft and any components
in front of the
engine, such as the engine's coolant radiator.
100121 An important feature of the present invention is that the motor-
generator exchanges
torque with the engine crankshaft via a switchable coupling (i.e.,
disengageable) between the
torque transfer segment and the front end of the crankshaft. The switchable
coupling includes an
engine-side portion coupled directly to the engine crankshaft, a drive portion
engageable with the
engine-side portion to transfer torque therebetween, and an engagement device,
preferably an
axially-actuated clutch between the drive portion and the engine-side portion.
The engine-side
portion of the coupling includes a crankshaft vibration damper (hereafter, a
"damper"), unlike a
conventional crankshaft damper that traditionally has been a separate element
fixed to the
crankshaft as a dedicated crankshaft vibration suppression device. This
arrangement enables
transfer of torque between the accessory drive, the motor-generator and the
engine in a flexible
manner, for example, having the accessory drive being driven by different
torque sources (e.g.,
the engine and/or the motor-generator), having the engine the being the source
of torque to drive
the motor-generator as an electric generator, and/or having the motor-
generator coupled to the
engine and operated as a motor to act as a supplemental vehicle propulsion
torque source.
100131 Particularly preferably, the switchable coupling is an integrated
clutch-pulley-damper
unit having the clutch between the engine side damper portion and the drive
portion. The drive
side portion includes a drive flange configured to be coupled to the engine-
end of the torque
transfer segment, the drive flange also including one or more drive pulley
sections on its outer
circumference. This preferred configuration also has all three of the pulley,
clutch and damper
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arranged concentrically, with at least two of these elements partially
overlapping one another
along their rotation axis. This arrangement results in a disengageable
coupling with a greatly
minimized axial depth to facilitate FEMG mounting in the space-constrained
environment in
front of an engine. The axial depth of the coupling may be further minimized
by reducing the
axial depth of the clutch, pulley and damper to a point at which the drive
pulley extends
concentrically around all or at least substantially all of the clutch and the
engine-side damper
portion of the coupling.
100141 Alternatively, one or more of the three clutch, pulley and damper
portions may be
arranged co-axially with, but not axially overlapping the other portions as
needed to suit the
particular front end arrangements of engines from different engine suppliers.
For example, in an
engine application in which a belt drive is not aligned with the damper (i.e.,
the damper does not
have belt-driving grooves about its outer circumference, such as in some
Cummins engine
arrangements), belt-driving surface of the pulley portion of the coupling need
not axially overlap
the damper. In other applications having belt drive surfaces on the outer
circumference of the
damper and a further belt drive surface on a pulley mounted in front of the
damper such as in
some Detroit Diesel engines, the coupling that would be used in place of the
original damper
and pulley may be arranged with both belt drive surfaces on a pulley that
extends axially over the
damper (i.e., the damper axially overlaps substantially all of both the damper
and the clutch), or
the belt drive surface on the outer circumference of the damper may be
maintained (for example,
to drive engine accessories that are never disconnected from the crankshaft,
such as an engine
coolant pump) while the other belt drive surface is located on the pulley
member that extends
axially over the clutch.
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100151 While in the description below reference is made to connecting the
damper portion of
the switchable coupling to the engine crankshaft, the switchable coupling
engine connection is
not limited to being connected to the crankshaft, but may be connected to any
rotatable shaft of
the engine accessible from the front of the engine that is capable of
transferring torque between
the engine and the motor-generator, such as a crankshaft-driven jackshaft or a
suitably
engineered camshaft having a front-accessible shaft end. Further, while in the
description below
reference is made to connecting a portion of the switchable coupling having
the damper to the
engine crankshaft, the switchable coupling's engine-side connection is not
limited to a portion
having a damper, but includes portions without a damper (such as a plate
member) capable of
being connected to a rotatable engine shaft while supporting an engine-side
part of the
disengageable coupling (such as holding an engine-side clutch plate of the
switchable coupling
opposite a pulley-side clutch plate).
100161 The FEMG motor-generator is preferably electrically coupled to an
electrical energy
storage unit (also referred to herein as an "energy store"). This energy store
preferably includes
both batteries suitable for high-capacity, long-term energy storage, such as
Lithium chemistry-
based batteries capable of storing and returning large amounts of energy at
moderate
charge/discharge rates, and super capacitors capable of receiving and
releasing electrical energy at
very high charge/discharge rates that may be beyond the ability of the Lithium
batteries to safely
handle. This combination provides an energy store which can work with the
motor-generator to
absorb and/or discharge electrical current for short periods at higher-than
normal levels (i.e., over
a wider range of motor-generator input or output loads than could be handled
by battery cells),
while also providing battery-based long-term energy storage and return at
lower charge and
discharge rates.
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100171 While the present disclosure is primarily directed to use of the FEMG
system in vehicle
applications (in particular, to commercial vehicle applications), the FEMG
system is also well-
suited for use with stationary engine installations (for example, standby
diesel generators), off-
road engine applications such as self-propelled construction equipment, and
other engine
applications in which the available space for providing hybrid electric
capability at the front of the
engine is limited.
100181 Overview of FEMG Drive of Engine Accessories
100191 Engine accessories traditionally have been belt-driven, being directly
driven by the
engine crankshaft via a drive belt pulley bolted to the crankshaft. In the
FEMG system the
engine accessories also are driven by a pulley, but the pulley is located on
the motor-generator
side of the clutch-pulley-damper (the "drive portion" identified above). The
pulley of the clutch-
pulley-damper unit is driven either by the engine when the coupling is
engaged, or by the motor-
generator when the coupling is disengaged. When the pulley-clutch-damper is
disengaged, all of
the engine accessories driven by the pulley are disconnected from the engine,
removing their
respective power demands from the engine. This isolation of the accessories
from the engine
reduces fuel consumption when the engine is running. In addition, because the
accessories may
be independently driven by the FEMG motor-generator via the torque transfer
segment while the
coupling is disengaged, the engine may be shut off or operated at idle with
few or no parasitic
loads while the vehicle is at a standstill to save fuel and reduce emissions.
100201 Further system efficiency gains may be obtained when the clutch-pulley-
damper is
disengaged, as the motor-generator's operating speed may be varied as desired
to operate one or
more of the engine accessories at a speed providing increased operating
efficiency, while other
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engine accessories are operated at sub-optimum efficiency speeds if doing so
decreases overall
energy consumption.
100211 Preferably, to increase system efficiency some or all of the engine
accessories may be
provided with individual drive clutches (either on/off or variable slip
engagement) to enable
selective engine accessory operation while other engine accessories are shut
down or operated at
reduced speed. The combination of the ability to operate the motor-generator
at variable speeds
and the ability to selectively engage, partially engage and disengage
individual accessory
clutches provides the opportunity to tailor accessory energy consumption to
only that needed for
the current operating conditions, further increasing overall system
efficiency.
100221 Alternatively, when one engine accessory has a high power input demand
that must be
met in the current vehicle operating state, the motor-generator may be driven
at a speed that
ensures the engine accessory with the highest demand can perform as needed,
while other
accessories are operated at lower-than-optimum efficiency, or are disconnected
from the motor-
generator drive by their respective clutches (if so equipped).
100231 Preferably an FEMG controller, discussed further below, executes an
algorithm which
evaluates factors such as engine accessory operating efficiency data and
current vehicle
operating state information (e.g., energy store state of charge ("SOC"),
engine torque output
demand, coolant temperature) to select a combination of vehicle operating
parameters (e.g.,
individual engine accessory clutch engagements, accessory operating speeds,
clutch-pulley-
damper pulley speed and engagement state, motor-generator speed and torque
output) to
determine a compromise configuration of coupling and clutch engagement states
and component
operating speeds that meets vehicle's operational needs while reducing fuel
and energy use. For
example, while providing superior overall system efficiency might be achieved
by operating the
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motor-generator at a speed and torque output that places as many engine
accessories as possible
at or near their peak operating efficiency states, a particular vehicle need
(such as the need to
operate the high-torque demand engine cooling fan to control engine coolant
temperature) may
result in the FEMG controlling the motor-generator speed and/or torque output
to ensure that the
particular demand is met, and then operating the other individual engine
accessories driven by
the clutch-pulley-damper in as efficient a manner as is possible under the
present vehicle
operating circumstances.
[0024] Similarly, if the current demand for vehicle propulsion torque from the
engine is high
(and the charge state of the energy store allows), the FEMG controller may
control the clutch-
pulley-damper to be switched to an engaged state and command the motor-
generator to supply
supplemental torque to the engine crankshaft to increase the total output of
propulsion torque,
even if this results in the engine accessories being driven at less than
optimum efficiency because
their speeds are tied to the crankshaft speed.
[0025] Overview of Motor-Generator Uses
[0026] When operating conditions allow, the clutch-pulley-damper may be
engaged such that
mechanical energy can be recovered by the motor-generator from the engine
crankshaft (i.e.,
recovering mechanical energy from the wheels that is transferred to the motor-
generator through
the drive line to the engine crankshaft). For example, the clutch may be
engaged during
deceleration events to allow the motor-generator to serve as a generator in a
regenerative braking
mode, a mode that also generates cost savings in reduced brake pad or brake
shoe wear and fuel
consumption savings by minimizing brake air use and the associated compressed
air consumption,
which in turn reduces air compressor use and energy consumption. The clutch
also may be
engaged when there is any other "negative torque" demand, such as when there
is a need to
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provide a retarding force to minimize undesired vehicle acceleration due to
gravity when the
vehicle is travelling down a hill.
100271 When the disengageable pulley-clutch-damper is engaged and operating
conditions
allow, the motor-generator may be operated as a torque-producing motor to
supply supplemental
torque to the engine crankshaft, thereby increasing the total torque output
supplied to the vehicle
driveline to improve vehicle acceleration.
100281 Another use of the motor-generator is as the primary engine starter,
eliminating the
need for a heavy, dedicated starter motor. In this mode of operation the
clutch-pulley-damper is
engaged to permit motor-generator torque to be transferred directly to the
engine crankshaft.
This use of the motor-generator is very well suited to the motor-generator's
operating
characteristics, as it is capable of producing very high torque output
starting at zero rpm, and do
so nearly instantaneously. The very quick reaction time of the motor-generator
and ability to do
so multiple times without overheating makes an FEMG system an excellent choice
for use as the
primary engine starting motor in a fuel-conserving engine "stop/start" system
in which the
engine is started and stopped multiple times a day. The short re-start
reaction time capability is
highly desired in stop/start system applications, where it is well known that
drivers express
dissatisfaction with any substantial delay in automatic engine re-starting in
response to the
driver's demand to begin moving again (typically, a demand generated by
releasing the vehicle's
brake pedal following a traffic signal turning green). For example, drivers
typically find a delay
of one second or more before the engine starts and the vehicle begins to move
to be at a
minimum annoying, if not outright unacceptable.
100291 Alternatively, the FEMG system's motor-generator may be operated as an
engine
starter in cooperation with a pneumatic starter motor that converts stored
compressed air pressure
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to a mechanical torque output (a pneumatic starter typically being lighter and
lower cost than a
conventional electric starter motor). The FEMG system weight and cost may be
improved with a
combined FEMG/pneumatic starting arrangement, as the supplemental torque
output of the
pneumatic starter may permit the FEMG motor-generator size to be reduced in
the case where
the highest anticipated torque demand on the FEMG motor-generator is
associated with engine
starting (in particular, cold engine starting). In such a case, the FEMG motor-
generator may be
sized to meet the torque demand of the next-lower demand (for example, the
highest expected
torque demand from the most demanding combination of engine accessories), with
the
pneumatic starter being available to provide the additional engine starting
torque needed above
that provided by the smaller FEMG motor-generator.
100301 The motor-generator also may be driven by the engine through the
engaged clutch-
pulley-damper clutch in a manner that eliminates the need to equip the engine
with a heavy,
dedicated alternator to supply operating voltage for a typical vehicle's 12
volt direct current
electrical circuits, such as vehicle lighting circuits, power supplies to
electronics modules and 12
V-powered driver-comfort features (heated seats, sleeper compartment
electrics, etc.). In an
FEMG system the needed 12 V power supply may be provided readily by a voltage
converter
that reduces the energy store's operating voltage (on the order of 300-400
volts) to the 12 volts
required by the vehicle electrical circuits. Thus, the motor-generator's
generation of electrical
energy to charge the energy store provides a source of 12 V electrical energy
that permits
elimination of a conventional engine-driven alternator. The storage of large
amounts of energy
in the energy store also creates the opportunity to remove additional weight
and cost from the
vehicle by reducing the number of 12 V batteries carried needed to meet the
vehicle's various
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needs. For example, a vehicle which conventionally may have four separate 12 V
batteries may
only need a single 12 V battery along with the energy store.
100311 Similarly, a voltage converter may be used to directly supply 120 volt
alternating
current power to the vehicle, for example to the sleeper compartment for
appliance or air
conditioner use or to an attached trailer to operate trailer devices such as
refrigeration units (the
latter preferably with a trailer connection to the vehicle's CAN system for
tractor-centric
monitoring and control of the trailer accessories). If the energy store is
designed to provide
sufficient storage capacity, the FEMG system also may eliminate the need to
equip a vehicle with
a costly and heavy internal combustion engine-powered auxiliary power unit to
support vehicle
operation when the engine is shut down for long periods. For example, an APU
would no longer
be needed to provide power to a sleeper compartment air conditioning unit
during overnight
driver rest periods.
100321 The FEMG also potentially may be used as an active damper to counter
rapid torque
reversal impulses ("torque ripples") sometimes encountered during various
load, speed and
environmental conditions. In this application the FEMG control module would
receive signals
from vehicle sensors indicating the presence of torque ripples and output
commands to the
motor-generator to generate counter-torque pulses timed to cancel the
driveline torque reversal
pulses. This FEMG motor-generator-based active damping would help protect the
driveline from
mechanical damage from the high stresses induced by the rapid change in torque
loads, as well
as improve driver comfort by removing the rapid accelerations/decelerations
transmitted through
the vehicle chassis to the driver's compartment.
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100331 Overview of FEMG Controller Programming and Operating Methods
100341 In a preferred embodiment, an FEMG controller, preferably in the form
of an
electronic control module, monitors multiple vehicle signals, including
signals available on the
vehicle's CAN and/or SAE J1939 bus network if the vehicle is so equipped. One
of the signals
may be a state of charge (SOC) indication from a battery monitoring system
that monitors,
among other parameters, a charge state of the energy store. The control module
may be
programmed, for example, to recognize three levels of charge state, minimum
charge level (for
example, a 20% state of charge), intermediate charge level (for example, a 40%
state of charge)
and maximum charge level (for example, an 80% state of charge). The control
module further
may be programmed to include the state of charge as a factor in determining
when to engage and
disengage the clutch of the clutch-pulley-damper, at what speed the motor-
generator should be
operated, the operating speeds of some or all of the engine accessories being
driven from the
pulley of the clutch-pulley-damper, and what combination of vehicle component
operation and
operating parameters will increase overall vehicle operating efficiency while
meeting the
vehicle's current operating needs and meeting requirements for safe vehicle
operation (e.g.,
maintaining at least a minimum required amount of air pressure in the
vehicle's pneumatic
system compressed air storage tanks by operating the air compressor, even if
doing so decreases
the overall energy efficiency of the vehicle).
100351 In one embodiment, when the state of charge of the energy store is
below the minimum
charge level, the clutch of the clutch-pulley-damper may be engaged and the
motor-generator
controlled by the control module to cause the motor-generator to produce
electrical energy for
storage. In this operating mode the motor-generator is powered by the engine
or by the wheels
via the driveline through the engine. Once the state of charge is above the
minimum charge
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level, the clutch-pulley-damper's clutch may remain engaged until the
intermediate charge level
is reached, and the motor-generator controlled to generate electrical energy
only during a
braking, deceleration or negative torque event. This mode permits non-engine-
provided
mechanical energy to be used by the motor-generator on an as-available basis
to continue to
charge the energy store, while minimizing the amount of energy the engine must
provide to the
motor-generator and thereby reducing fuel consumption.
100361 In another operating mode, once the intermediate charge level is
reached, the control
module may determine the clutch of the clutch-pulley-damper can be disengaged
and the motor-
generator used as a motor to generate torque to drive the engine accessories
without assistance
from the engine, i.e., the motor-generator becomes the sole source of drive
energy for the engine
accessories. In this mode, the motor-generator draws stored electrical energy
from the energy
store to generate torque for delivery, via the drive unit gearbox, to the
pulley of the clutch-pulley-
damper to drive engine accessories such as the engine cooling fan and the
pneumatic supply
system's air compressor. By disengaging the engine from the torque demands of
the engine
accessories, the engine may be operated with a lower parasitic torque load to
reduce the engine's
fuel consumption or to make more engine torque output available to propel the
vehicle.
Alternatively, when the motor-generator can be operated in the motor mode to
drive the engine
accessories, the engine may be shut down entirely, such as when in stop-and-go
traffic in a
vehicle equipped with a start/stop system.
100371 Between the intermediate charge level and the maximum charge level, the
front end
motor-generator control module continues to monitor the vehicle operating
state, and during a
braking, deceleration or negative torque event can take advantage of the
opportunity to further
charge the energy store without using engine fuel by engaging the clutch of
the clutch-pulley-
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damper and controlling the motor-generator to generate electrical energy.
While charging during
a braking, deceleration or negative torque event can occur at any time the
energy store is below
the maximum charge level; in this embodiment avoiding use of engine fuel for
charging above
the intermediate charge level reduces fuel consumption and improves overall
efficiency.
100381 At any point above the minimum charge level the motor-generator may be
operated as
a motor to generate torque to be delivered to the engine crankshaft to
supplement the engine's
torque output, thereby increasing the amount of torque available to propel the
vehicle. The
increased torque output to the driveline enables improved vehicle acceleration
and provides
additional benefits, such as improved fuel economy from fewer transmission
gearshifts and more
rapid acceleration to cruising speed (e.g., "skip-shifting," where the motor-
generator adds
sufficient engine torque to permit one or more gear ratios to be passed over
as the vehicle
accelerates, reducing vehicle time to speed and fuel consumption). Moreover,
in vehicles
equipped with pneumatic boost systems ("PBS", systems which inject compressed
air into the
engine intake to very quickly provide additional engine torque output), use of
the virtually
"instant on" torque assist from the motor-generator whenever possible in lieu
of using
compressed air injection from the PBS system to generate additional engine
torque output can
reduce compressed air use, in turn further reducing fuel consumption and
component wear (the
consumption and wear associated with additional air compressor operation to
replenish the
compressed air supply).
100391 Once the FEMG control module determines the maximum charge level has
been
reached and therefore no further input of electrical energy into the energy
store is desired, the
control module will prevent operation of the motor-generator as a generator in
order to protect
the energy store from damage due to over-charging. In this mode the motor-
generator may be
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used only as an electric motor to drive the engine accessories and/or to
provide supplemental
drive torque to the engine, or allowed to rotate in a non-power-producing idle
state if there is no
current engine accessory demand.
100401 The FEMG controller preferably communicates with several vehicle
controllers, such
as the vehicle's brake controller (which may be controlling different types of
brakes, such as
pneumatic or hydraulic brakes), the engine and/or transmission controllers and
the one or more
controllers managing the energy store. These communications permit coordinate
operation of the
vehicle systems. For example, in the case of a braking demand that is
sufficiently low to only
require use of an engine retarder, the brake controller and FEMG control
module may signal one
another to give the motor-generator priority over use of the retarder, such
that the motor-
generator provides regenerative braking if the energy charge state will allow
storage of additional
electrical energy (i.e., energy store charge state below the maximum allowed
charge state).
Conversely, if the operating conditions are not such that generation of
additional electrical
energy by the motor-generator is desired, the FEMG control module may signal
such to the brake
controller so that the brake controller activates the retarder to provide the
desired amount of
braking. The communications between the controllers preferably is on-going,
providing the
ability for rapid updating of status. For example, the brake controller would
be able to signal the
FEMG control module to reduce the amount of regenerative braking if the driver
lowers the
amount of braking demand during the braking event.
100411 Another example of possible inter-controller communications is
coordination of air
compressor operations with energy store management. For example, the air
compressor
controller may signal the FEMG control module to operate the motor-generator
with the clutch-
pulley-damper clutch disengaged (engine running or shut down) to drive the air
compressor at a
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desired speed to replenish compressed air storage resulting from a large air
consumption demand
(such as a tire inflation system trying to counter a large tire pressure leak,
a large air leak in
tractor or trailer air lines, use of a trailer's air-landing gear, high air
release during ABS system
brake pressure modulation or trailer stability system activation on low-
friction road surfaces,
operating a king pin air-operated lock/unlock device, or actuation of an air-
operated lift-axle).
100421 Additional Operational Improvements Provided By the FEMG System
100431 In addition to the already mentioned features, capabilities and
advantages, the present
invention's front end motor-generator approach has the important advantage of
not requiring
substantial modifications to the front of a vehicle, such as lengthening of
the nose of a
commercial vehicle tractor or increasing the size of an engine compartment of
a diesel-powered
municipal bus. This is directly the result of the FEMG system being readily
accommodated
between the front of the engine and the engine's coolant radiator by use of
the integrated clutch-
pulley damper unit and associated axially-narrow drive unit to laterally
transfer torque to/from the
motor-generator. As a result, the FEMG system is exceptionally well suited for
incorporation into
existing vehicle designs, both during the course of new vehicle assembly and
by retro-fitting
existing internal combustion engines to upgrade older vehicles (particularly
commercial vehicles)
and stationary engine installations with hybrid-electric technology.
100441 Another operational advantage provided by the FEMG system is its
ability for the
motor-generator to assist the engine to provide short duration "over-speed"
vehicle operation. In
such an application, the vehicle's controllers coordinate the addition of
supplemental torque from
the motor-generator with a temporary override of the vehicle's speed governor
to allow for brief
"bursts" of speed, for example to permit rapid completion of overtaking of a
similar speed
vehicle such as another large truck.. While use of such an operating mode
should be limited to
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brief, infrequent periods to minimize excessive loading of the engine and
driveline components,
the FEMG system could be programmed to provide a driver-actuated "over-speed"
mode, i.e., a
driver-switchable option (e.g., a "push-to-pass" button) to briefly increase
speed on an as-needed
basis. Preferably such a push-to-pass mode could be coordinated with a
vehicle's blind-spot
monitoring controller via the CAN network, enabling, for example, the over-
speed operation to
be automatically terminated once the blind-spot monitoring system indicates
the vehicle being
passed is no longer alongside. This coordination would include as part of the
termination of this
mode the FEMG control module terminating the motor-generator's supply of
supplemental
torque to the engine crankshaft.
100451 Motor-generator supplemental torque has further applications, such as
reducing driver
fatigue in a driver assistance system by automatically adding torque when
doing so would
minimize the need for the driver to manually shift the transmission,
particularly when climbing
hills (and when associated safety requirements are satisfied, such as there
being nothing in the
view of the vehicle's adaptive cruise-control camera and/or radar systems).
100461 Supplemental motor-generator torque may also be used in a trailer
weight-
determination system in which a known amount of additional torque is added and
a measurement
of the resulting vehicle acceleration during the supplemental torque
application is used in a
vehicle mass calculation.
100471 The addition of supplemental drive torque from the motor-generator
should be
constrained in cases where safety concerns are present. For example, the
commanding of
supplemental torque delivery should be inhibited when a low friction signal
indicative of the
trailer wheels encountering a low friction surface is received from the
trailer.
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100481 The application of the FEMG system is not limited to applications in
which the motor-
generator is the sole electric generator. Synergies may be realized by the
addition of an FEMG
front end installation to an engine and/or drivetrain that also includes a
motor-generator unit to
the rear of the crankshaft-side of the FEMG clutch, for example, at the rear
of the engine (such as
a flywheel motor-generator), in the downstream driveline (such as a motor-
generator
incorporated into a transmission) or at the front end of the crankshaft, i.e.,
on the constantly-
engaged side of the FEMG clutch-pulley-damper unit.
100491 The combination of an FEMG system and a "back end" hybrid electric
arrangement
presents opportunities for overall vehicle operational improvements. For
example, the presence
of both front and back-end systems may enable one or both of the motor-
generators to be
reduced in size and weight while still meeting vehicle demands, because
neither motor-generator
needs to be sized to handle all of the vehicle's electrical demands where
there is no longer a need
for all of the vehicle's electric generation and power supply demands to be
met by only one
motor-generator. Further, operational flexibility may be increased by the
presence of two motor-
generators if each is be able to meet at least essential vehicle demands in
the event of failure of
the other motor-generator, thereby permitting the vehicle to continue in
operation, perhaps at
reduced performance, until reaching a time or place where repairs may be
performed.
100501 The operation of an FEMG system and a back-end motor-generator may also
be
coordinated to split and/or share loads on an as-needed basis to optimize
vehicle operation. For
example, loads may be split between the motor-generators in a case where the
FEMG system
assumes engine accessory drive and energy storage charging demands while the
back-end motor-
generator helps propel the vehicle by providing supplemental torque output to
the vehicle
driveline to assist the engine. An example of a sharing synergy would be using
the back-end
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motor-generator to receive and store energy from regenerative braking from the
driveline while
keeping the FEMG decoupled from the crankshaft to improve engine accessory
efficiency (i.e.,
allowing capture of regenerative braking energy by the back-end motor-
generator even when the
FEMG system is decoupled from the crankshaft and thus not able to capture
otherwise wasted
braking energy). The flexibility of the combination of an FEMG system with
another partial
hybrid system is limitless, e.g., operating both motor-generators together
with the FEMG clutch
engaged to have both motor-generators provide supplemental drive torque or to
use both to
capture regenerative braking energy for storage, etc.
100511 The FEMG components and controllers also may be adapted for use in
applications
benefitting from the capability to disengage engine accessories from the
engine crankshaft, but
do not have a need for the electricity generation capacity a full FEMG system
installation would
provide. Such "motor-only" applications may include vehicles having operating
needs which do
not require the additional expense and complication of a high-voltage
electrical energy storage
and distribution system, but which may still benefit from efficiency
improvements using the
FEMG system's ability to decouple the engine crankshaft from the accessory
drive and use an
FEMG motor to drive the accessories. Such motor-only operation may be supplied
from a
smaller, simpler battery pack whose charge state could be maintained by the
vehicle engine's
alternator.
100521 For example, an engine in a container transporter used at a container
ship port
loading/unloading yard would not need the ability to supply power for long
periods when the
engine is shutdown, such as providing overnight power for an over-the-road
truck's sleeper
compartment. Yet the container transporter efficiency and/or torque output may
be improved
with an FEMG system's crankshaft decoupling components and its associated
control of
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accessory drive by the FEMG motor. For example, efficiency improvements may be
realized by
decoupling the crankshaft from the accessory drive in various operating
conditions, such as at
idle times to remove accessory loads from the engine; to permit operation of
the transporter
systems for short periods while the engine is shutdown, to enable fuel-saving
engine stop-start
operations; and to devote full engine torque output to the transporter drive
when needed by
removing the accessory drive torque demand from the engine). Similarly, a
motor-only FEMG
system may be coupled to the engine crankshaft when it is desired to have the
FEMG motor
supplement the engine's propulsion torque output. This latter feature may
enable further
improvements by allowing the engine to be smaller, lighter and less costly by
being sized to meet
an "average" torque demand, with the FEMG motor providing supplemental torque
as needed to
meet the vehicle's design total propulsion torque demand.
100531 In a further embodiment of the present invention, the accessories may
be consolidated
into an integrated accessory unit, and may be located away from the front end
of the engine, for
example as an integrated electrified accessory unit. In such a unit,
accessories conventionally
driven at the front of an engine may be grouped to be driven, preferably by a
single accessory
drive system such as a belt drive or a gear drive, by an electric motor.
Further preferably, the
integrated electrified accessory unit may be located out of the high
temperature region of an
engine compartment, for example in a box structure suspended from a chassis
member (aka
frame rail) of the vehicle. An example of such a location is the space
conventionally occupied by
one of a typical commercial vehicle's "saddle" fuel tanks. The integrated
electrified accessory
unit may also be mounted using isolating mounting components to minimize
vibration and shock
transfer from the vehicle to the components within the unit.
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100541 The integrated electrified accessory unit may include a number of
formerly engine-
driven accessories, such as an air conditioning compressor, a power steering
pump, and a
thermodynamic heater, along with individual clutch units between the accessory
drive and one or
more of the accessories that permit individual accessories to be decoupled
from the accessory drive
to improve efficiency and reduce component wear.
100551 The integrated electrified accessory unit may also house an electronic
control unit
which controls the operation of the accessories, the individual accessory
clutches, the electric
drive motor coupled to the accessory drive, and/or a power inverter which
receives power from
the vehicle and converts the power (for example, converting vehicle-supplied
DC power to AC
power) to meet the demands of the electric drive motor. The electronic control
unit preferably
communicates with the rest of the vehicle over a network such as a CAN to
obtain and output
information necessary to control the accessories to meet the vehicle's
accessory demands. A
battery also may be located within the integrated electrified accessory unit.
100561 The transfer of working fluids (liquid and gaseous) to/from the vehicle
and the
accessories within the integrated electrified accessory unit may be provided
via connections
through the side walls of the unit. Such an arrangement provides a user of the
integrated
electrified accessory unit with standardized interfaces and thus eliminates a
need for the user to
open the integrated electrified accessory unit during its installation on a
vehicle.
100571 Similarly, the cooling of the components inside the integrated
electrified accessory unit
(both accessories and electrical/electronic components) and the integrated
electrified accessory
unit itself may be provided by heat transfer by fluids to an external heat
exchanger, heat
conduction from the integrated electrified accessory unit, for example via
passive and/or active
heat exchangers mounted on the exterior unit walls (e.g., heat dissipation
fins and/or fluid heat
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exchangers mounted on a wall for conductive heat exchange from the unit),
an/or by air cooling
(arranged to prevent entry of undesired environmental elements, such as rain
water). In
applications in which the components inside the integrated electrified
accessory unit are liquid
cooled, preferably at least the electric motor and the inverter share a common
cooling fluid.
100581 Other objects, advantages and novel features of the present invention
will become
apparent from the following detailed description of the invention when
considered in conjunction
with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
100591 Figs. 1A and 1B are schematic illustrations of an overall view of the
arrangements of
an FEMG system in accordance with an embodiment of the present invention.
100601 Figs. 2A-2C are cross-section views of an embodiment of a clutch-pulley-
damper and
assembled FEMG components in accordance with the present invention.
100611 Figs. 3A-3C are views of the components of the Figs. 2A-2C clutch-
pulley-damper
unit.
100621 Fig. 4 is a cross-section view of another embodiment of a clutch-pulley-
damper unit in
accordance with the present invention.
100631 Fig. 5 is detailed cross-section view of a bearing arrangement at the
clutch-pulley-
damper unit end of an FEMG gearbox in accordance with an embodiment of the
present
invention.
100641 Figs. 6A-6C are oblique views of an FEMG drive unit in the form of a
gearbox in
accordance with an embodiment of the present invention.
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100651 Fig. 7 is a cross-section view of the FEMG gearbox of Figs. 6A-6C.
100661 Fig. 8 is exploded view of an FEMG clutch pneumatic actuator diaphragm
arrangements in accordance with an embodiment of the present invention.
100671 Fig. 9 is an oblique view of another embodiment of an FEMG gearbox in
accordance
with the present invention.
100681 Fig. 10 is a schematic illustration of an FEMG gearbox mounting
arrangement in
accordance with an embodiment of the present invention.
100691 Fig. 11 is a schematic illustration of an FEMG gearbox mounting
arrangement in
accordance with an embodiment of the present invention.
100701 Fig. 12 is a schematic illustration of relationships between an engine
and an FEMG
gearbox mounting bracket in accordance with an embodiment of the present
invention.
100711 Fig. 13 is a schematic illustration of relationships between an engine,
FEMG gearbox
and an FEMG gearbox mounting bracket in accordance with an embodiment of the
present
invention.
100721 Fig. 14 is an oblique view of an FEMG gearbox mounting bracket as in
Figs. 12-13.
100731 Fig. 15 is an oblique view of a motor-generator in accordance with an
embodiment of
the present invention.
100741 Fig. 16 is a graph of power and torque generated by an example motor-
generator in
accordance with an embodiment of the present invention.
100751 Fig. 17 is an oblique phantom view of a cooling arrangement of a motor-
generator in
accordance with an embodiment of the present invention.
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100761 Fig. 18 is a block diagram of FEMG system control and signal exchange
arrangements
in accordance with an embodiment of the present invention.
100771 Fig. 19 is a schematic illustration of AC and DC portions of the
electrical network of
an FEMG system in accordance with an embodiment of the present invention.
100781 Fig. 20 is a schematic illustration of an FEMG system-controlled power
transistor
arrangement for AC and DC conversion in accordance with an embodiment of the
present
invention.
100791 Fig. 21 is a schematic illustration of an FEMG system-controlled
forward DC voltage
converter arrangement in accordance with an embodiment of the present
invention.
100801 Fig. 22 is a schematic illustration of a high voltage bi-directional
DC/DC converter in
accordance with an embodiment of the present invention.
100811 Fig. 23 is a graphical illustration of voltage and current responses
across the bi-
directional DC/DC converter of Fig. 22.
100821 Fig. 24 is an oblique view of a power electronics arrangement
integrated into a motor-
generator in accordance with an embodiment of the present invention.
100831 Fig. 25 is a battery management system state of charge estimation
control loop in
accordance with an embodiment of the present invention.
100841 Fig. 26 is a flow chart of accessory operating speed selection in
accordance with an
embodiment of the present invention.
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100851 Fig. 27 is a flow chart of a control strategy for operation of a motor
generator and
engine accessories independently of an engine in accordance with an embodiment
of the present
invention.
100861 Fig. 28 is an oblique illustration of an embodiment of an integrated
electrified
accessory unit in accordance with the present invention.
100871 Figs. 29A, 29B are side views of the integrated electrified accessory
unit embodiment
shown in Fig. 28.
[0088] Fig. 30 is an elevation view of an integrated electrified accessory
unit embodiment
without a housing in accordance with the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
[0089] A Front End Motor-Generator System Embodiment.
[0090] Fig. lA is a schematic illustration showing components of an embodiment
of an FEMG
system in accordance with the present invention. Fig. 1B is a schematic
illustration of several of
the FEMG system components in the chassis of a commercial vehicle. In this
arrangement, the
engine accessories (including air compressor 1, air conditioning compressor 2
and engine cooling
fan 7 arranged to pull cooling air through engine coolant radiator 20) are
belt-driven from a pulley
5. The pulley 5 is located co-axially with a damper 6 coupled directly to the
crankshaft of the
internal combustion engine 8. The accessories may be directly driven by the
drive belt or
provided with their own on/off or variable-speed clutches (not illustrated)
which permit partial or
total disengagement of an individually clutch-equipped accessory from the belt
drive.
[0091] In addition to driving the accessory drive belt, the pulley 5 is
coupled a drive unit
having reduction gears 4 to transfer torque between a crankshaft end of the
drive unit and an
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opposite end which is coupled to a motor-generator 3 (the drive unit housing
is not illustrated in
this figure for clarity). A disengageable coupling in the form of a clutch 15
is arranged between
the crankshaft damper 6 and the pulley 5 (and hence the drive unit and the
motor-generator 3).
Although schematically illustrated as axially-separate components for clarity
in Fig. 1A, in this
embodiment the crankshaft 6, clutch 15 and pulley 5 axially overlap one
another at least
partially, thereby minimizing an axial depth of the combined pulley-clutch-
damper unit in front
of the engine. Actuation of the pulley-clutch-damper clutch 15 between its
engaged and
disengaged states is controlled by an electronic control unit (ECU) 13.
[0092] On the electrical side of the motor-generator 3, the motor-generator is
electrically
connected to a power invertor 14 which converts alternating current (AC)
generated by the
motor-generator output to direct current (DC) useable in an energy storage and
distribution
system. The power invertor 14 likewise in the reverse direction converts
direct current from the
energy storage and distribution system to alternating current input to power
the motor-generator
3 as a torque-producing electric motor. The inverter 14 is electrically
connected to an energy
storage unit 11 (hereafter, an "energy store"), which can both receive energy
for storage and
output energy on an on-demand basis.
[0093] In this embodiment, the energy store 11 contains Lithium-based storage
cells having a
nominal charged voltage of approximately 3.7 V per cell (operating range of
2.1 V to 4.1 V),
connected in series to provide a nominal energy store voltage of 400 volts
(operating voltage
range of approximately 300 V to 400 volts) with a storage capacity of between
approximately 12
and 17 kilowatt-hours of electrical energy. Alternatively, the cells may be
connected in series and
parallel as needed to suit the application. For example, 28 modules with four
series-connected
cells per module could be connected in series and in parallel to provide an
energy store with the
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same 17 kilowatt hours of stored energy as the first example above, but with a
nominal operating
voltage of 200 V volts and twice the current output of the first example.
100941 In addition to the relatively high-capacity, low charge-discharge rate
Lithium-based
storage cells, the energy store 11 in this embodiment includes a number of
relatively low-capacity,
high charge-discharge rate of super capacitors to provide the energy store the
ability over short
periods to receive and/or discharge very large electrical currents that could
not be handled by the
Lithium-based storage cells (such cells being typically limited to
charge/discharge rates of less
than 1 C to only a few C).
100951 FEMG System Hardware Assembly Embodiment.
100961 Figures 2A-2C show cross-section views of an embodiment of the clutch-
pulley-
damper unit 19 and of an assembled configuration of FEMG system hardware with
this clutch-
pulley-damper embodiment. In this embodiment the gearbox 16 containing
reduction gears 4
receives the motor-generator 3 at a motor-generator end of the gearbox. The
motor-generator 3 is
secured to the housing of gearbox 16 with fasteners such as bolts (not
illustrated). A rotor shaft
18 of the motor-generator 3 engages a corresponding central bore of the
adjacent co-axially-
located gear of the reduction gears 4 to permit transfer of torque between the
motor-generator 3
and the reduction gears 4.
100971 At the crankshaft end of the gearbox 16, the reduction gear 4 which is
co-axially-
aligned with the clutch-pulley-damper unit 19 is coupled for co-rotation to
pulley side of the
clutch-pulley-damper unit 19, in this embodiment by bolts (not shown) passing
through the co-
axial reduction gear 4. The engine-side portion of the coupling (the portion
having the
crankshaft damper 6) is configured to be coupled to the front end of the
engine crankshaft by
fasteners or other suitable connections that ensure co-rotation of the engine-
side portion 6 with
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the crankshaft. As described further below, the gearbox 16 is separately
mounted to a structure
that maintains the clutch-pulley-damper unit 19 co-axially aligned with the
front end of the
engine crankshaft.
100981 The cross-section view in Fig. 2B is a view from above the FEMG front
end hardware,
and the oblique cross-section view in Fig. 2C is a view at the crankshaft end
of the gearbox 16.
In this embodiment, the gearbox, motor-generator and clutch-pulley-damper unit
assembly is
arranged with the motor-generator 3 being located on the left side of the
engine crankshaft and
on the front side of the gearbox 16 (the side away from the front of the
engine), where the motor-
generator 3 may be located either in a space below or directly behind the
vehicle's engine
coolant radiator 20. Alternatively, in order to accommodate different vehicle
arrangements, the
gearbox 16 may be mounted with the motor-generator 3 to the rear of the
gearbox 16, preferably
in a space laterally to the left side of the engine crankshaft (for example,
adjacent to the oil pan at
the bottom of the engine). The gearbox 16 further may be provided with dual-
sided motor-
generator mounting features, such that a common gearbox design may be used
both in vehicle
applications with a front-mounted motor-generator and vehicle applications
with the motor-
generator mounted to the rear side of the gearbox.
100991 FEMG Clutch-Pulley-Damper Unit Embodiments.
1001001 Figs. 3A-3C are views of the components of the clutch-pulley-damper
unit 19 of Figs.
2A-2C. When assembled, the unit is unusually narrow in the axial direction due
to the
substantial axial overlapping of the pulley 5, engine-side portion 6
(hereafter, damper 6) and
clutch 15. In this embodiment the pulley 5 has two belt drive portions 21
configured to drive
accessory drive belts (not illustrated), for example, one portion arranged to
drive the engine
cooling fan 7 surrounding the clutch 15, and another portion arranged to drive
other engine
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accessories such as the air compressor 1. The drive belt portions 21 in this
example
concentrically surround the damper 6 and the clutch 15 (the belt drive portion
21 surrounding the
damper 6 is omitted in Figs. 2B and 2C for clarity).
1001011 Within the clutch-pulley-damper unit 19 the clutch 15 includes two
axially-engaging
dog clutch elements 25, 26. As shown in the Figs. 2A-2C cross-section views,
the central core
dog clutch element 25 is fixed for rotation with the damper 6, in this
embodiment by bolts
extending through axial bolt holes 28 from the FEMG gearbox side of the clutch-
pulley-damper
unit 19. The pulley 5 is rotationally supported on the central core element 25
by bearings 34.
1001021 An engine-side portion of the outer circumference of the central core
dog clutch
element 25 includes external splines 29 arranged to engage corresponding
internal splines 30 at
an inner circumference of the axially-movable dog clutch element 26. The
external splines 29
and internal splines 30 are in constant engagement, such that the movable dog
clutch element 26
rotates with the damper 6 while being movable axially along the damper
rotation axis.
1001031 The movable dog clutch element 26 is also provided with axially
forward-facing dogs
31 distributed circumferentially about the gearbox side of the element 26 (the
side facing away
from the engine). These dogs 31 are configured to engage spaces between
corresponding dogs
32 on an engine-facing side of the pulley 5, as shown in Fig. 3C. The movable
dog clutch
element 26 is biased in the clutch-pulley-damper unit in an engaged position
by a spring 33
located between the damper 6 and the movable dog clutch element 26, as shown
in Fig. 2A.
Figures 2B and 2C show the clutch disengaged position, in which the spring 33
is compressed as
the movable dog clutch element 26 is axially displaced toward the damper 6.
1001041 In this embodiment a clutch throw-out rod 27 is located concentrically
within the
central core dog clutch element 25. The engine-side end of the throw-out rod
27 is arranged to
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apply an axial clutch disengagement force that overcomes the bias of spring 33
to axially
displace the dog clutch element 26 toward the damper 6, thereby disengaging
its forward-facing
dogs 31 from the corresponding dogs 32 at the engine-facing side of the pulley
5. In this
embodiment, the gearbox end of the clutch throw-out rod 27 is provided with a
bushing 303 and
a bearing 304 which enables the bushing to remain stationary while the throw-
out rod 27 rotates.
1001051 The clutch throw-out rod 27 is axially displaced to disengage and
engage the dog
clutch 15 by a clutch actuator 22. In this embodiment the clutch actuator 22
is pneumatically-
actuated, with compressed air entering fitting 305 over clutch actuator
diaphragm 41 and thereby
urging the center portion of the diaphragm 41 into contact with the throw-out
rod bushing 303 to
axially displace the clutch throw-out rod 27 toward the engine to disengage
the clutch 15. When
compressed air pressure is removed from the clutch actuator the diaphragm 41
retracts away
from the engine, allowing the biasing spring 33 to axially displace the throw-
out rod 27 and the
dog clutch element 26 toward the pulley 5 to reengage the clutch dogs 31, 32
so that the pulley 5
co-rotates with the damper 6.
1001061 Fig. 4 shows an alternative embodiment of the clutch-pulley-damper
unit 19 in which
the clutch 15 is a so-called wet multi-plate clutch. The wet multi-plate
clutch includes friction
and driven plates 23 splined in an alternating manner to an inner
circumference of the pulley 5
and an outer circumference of a center portion of the damper 6. The clutch
plates 23 are axially
biased in compression by springs 24 between the damper 6 and the clutch
actuator 22 (in this
embodiment a pneumatically-actuated clutch actuation piston). The biasing of
the stack of
friction and driven plates together by the springs 24 engages the clutch 15
and causes pulley 5
and damper 6 to co-rotate with one another about the rotational axis of the
engine crankshaft.
When hydraulic pressure is applied to the clutch actuator 22 (on the FEMG
gearbox side of the
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actuator), the springs 24 are compressed, allowing the alternating clutch
friction and driven
plates 23 to axially separate and thereby place the clutch 15 in a disengaged
state, i.e., a state in
which pulley 5 and damper 6 rotate independently.
1001071 In this embodiment the hydraulic pressure is supplied by oil that is
also used to cool
and lubricate the gearbox reduction gears and their associated bearings, and
cool the wet-multi-
plate clutch's friction and driven plates. The application of the hydraulic
pressure is controlled
by a solenoid valve (not illustrated) in response to commands from the FEMG
electronic control
unit 13. The clutch 15 is sized to ensure the large amount of torque that can
pass between the
engine crankshaft and the motor-generator will be accommodated by the clutch
without slippage.
To this end, due to the axially-overlapping arrangement of the clutch-pulley-
damper unit 19, the
unit's cooling design should be configured to ensure adequate cooling of the
clutch plates during
all operations. While in this embodiment cooling is provided by the oil being
circulated in the
gearbox, other forced or passive cooling arrangements may be provided as long
as the expected
clutch temperature is maintained below the clutch's operating temperature
limit.
1001081 FEMG Gearbox Embodiment.
1001091 Fig. 5 is a cross-section detailed view of a bearing arrangement at
the crankshaft end of
an embodiment of the FEMG gearbox 16. Figs. 6A-6C and 7 show oblique views of
this
gearbox embodiment, in which a pair of gearbox clamshell-housing plates 35
enclose reduction
gears 4, including a pulley-end gear 36, an idler gear 37 and a motor-
generator-end gear 38.
1001101 In this application, the gears have a drive ratio of 2:1, although any
gear ratio which
fits within the available space of a particular engine application while
providing a desired ratio of
crankshaft speed-to-motor-generator speed may be provided. The gears 36-38 may
be spur
gears, helical gears or have other gear teeth (such as double-helix
herringbone gear teeth) as
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desired to suit the requirements of the particular FEMG system application.
Such requirements
include gear noise limitations needed to meet government noise emission or
driver comfort
limitations that might be met with helical gears, mechanical strength
limitations, such as tooth
stress limits, or axial thrust limits that might be meet with double-helix
herringbone gear teeth
which generate equal and opposite axial thrust components.
1001111 The gearbox housing rotatably supports each of reduction gears 36-38
with bearings 39.
The pulley-end gear 36 includes a plurality of through-holes 40 in a
circumferential ring inside its
gear teeth corresponding to holes on the front face of the pulley 5 of the
clutch-pulley-damper.
These holes receive fasteners configured to rotationally fix the pulley-end
reduction gear 36 to the
pulley 5 for co-rotation when driven by the crankshaft and/or by the motor-
generator.
1001121 The center of the pulley-end reduction gear 36 has a center aperture
through which a
pneumatically-powered dog-clutch actuating diaphragm 41 is located on a front
face of the
gearbox housing. The pneumatic diaphragm 41 axially extends and retracts a
piston (not
illustrated) arranged to engage the cup 27 on dog clutch element 26 to control
engagement and
disengagement of the clutch 15 of the clutch-pulley-damper unit 19. The
diaphragm 41 is shown
in Fig. 5 as covered by the pneumatic clutch actuator 22, while Figs. 7-8 show
a simpler, slim
diaphragm cover 42 with a compressed air connection on its face that is
suitable for use in
particularly space-constrained FEMG applications. Regardless of the diaphragm
cover design,
the diaphragm 41 is acted on by compressed air in the chamber above the front
face of the
diaphragm created when the clutch actuator 22 or the cover plate 42 are
installed over the
diaphragm aperture at the front face of the gearbox housing. The admission and
release of
compressed air may controlled by solenoid valves (not illustrated) in response
to commands from
the FEMG control module 13. While the clutch actuation mechanism in this
embodiment is a
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pneumatically-actuated diaphragm, the present invention is not limited to a
particular clutch
actuator. For example, an electro-mechanical actuator may be used, such as an
electrically-
powered solenoid configured to extend an actuator rod to disengage the clutch
components.
1001131 Figs. 5 and 8 provide further detail of the mounting of this
embodiment's pneumatic
diaphragm actuator. In this embodiment an engine-side of a diaphragm mounting
ring 45 is
configured both to support the front-side bearing 39 associated with pulley-
end reduction gear
36, and to receive on its front side the diaphragm 41. The bearing 39 may be
retained and axially
supported by any suitable device, such as a snap ring, or as shown in Fig. 5
by a nut 46. Once
the mounting ring is secured in the illustrated large aperture on the front
face of the gearbox
housing clamshell plate 35, the pulley-end reduction gear 36 and its bearing
39, as well as the
diaphragm 41, are axially fixed relative to the housing of gearbox 16.
1001141 At the motor-generator end of the gearbox 16, a shaft hole 43 aligned
with the rotation
axis of the motor-generator-end reduction gear 38 is provided in at least one
of the housing
clamshell plates 35, as shown in Figs. 6A-6C and 7. The shaft hole 43 is sized
to permit the
rotor shaft of the motor-generator 3 (not illustrated in this figure) to enter
the gearbox 16 and
engage motor-generator-end gear 38 for co-rotation.
1001151 The FEMG gearbox may be cooled and lubricated by oil. The oil may be
stored in a
self-contained oil sump, or alternatively in a remote location, such as an
external container or the
engine's oil reservoir if the engine and gearbox are sharing the same oil
source. The oil may be
circulated throughout the gearbox by the motion of the gears or by a pump that
distributes
pressurized oil, such as an electric pump or a mechanical pump driven by the
rotation of the
reduction gears, and in addition to lubricating and cooling the gears may cool
the clutch plates of
a wet-clutch. Further, the gearbox may be provided with an accumulator that
ensures a reserve
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volume of pressurized oil remains available to, for example, actuate the
clutch of the clutch-
pulley-damper unit when pump-generated pressure is not immediately available.
In such an
embodiment, a solenoid valve controlled by the FEMG control module could be
used to release
the pressurized oil to operate the actuator of the hydraulic clutch.
1001161 Figure 9 shows an example of a commercially-available gearbox showing
an
alternative motor-generator mounting arrangement in which a motor-generator
mounting flange
44 provides the ability to mount the motor-generator to the gearbox with
fasteners without the
need for fastener penetrations into the gearbox housing.
1001171 In the foregoing embodiments the end reduction gears 36, 38 are in
constant-mesh
engagement via idler gear 37. However, the present invention is not limited to
this type of single
reduction parallel shaft gearbox. Rather, other torque power transmission
arrangements are
possible, such as chain or belt drives, or drives with components such as
torque transfer shafts
aligned at an angle to the switchable coupling's rotation axis (for example, a
worm-gear drive
with a transfer shaft rotating on an axis perpendicular to the switchable
coupling's rotation axis),
as long as they can withstand the torque to be transferred without needing to
be so large that the
axial depth of the gearbox becomes unacceptably large. Such alternative
gearbox arrangements
may also be used in embodiments in which the motor-generator 3 is not aligned
parallel to the
rotation axis of the switchable coupling, but instead is positioned on the
gearbox 16 and aligned
as necessary to facilitate installation in regions of limited space (for
example, motor-generator
being attached at the end of the gearbox with its rotation axis aligned with a
gearbox torque
transfer shaft that is not parallel to the switchable coupling's rotation
axis).
1001181 Nor is the present invention limited to fixed reduction ratio constant-
mesh arrangements,
as other arrangements may be used, such as variable diameter pulleys (similar
to those used in
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some vehicle constant velocity transmissions) or internally-disengageable
gears, as long as the
axial depth of the gearbox does not preclude the location of the FEMG system
components in the
region in front of the engine.
1001191 In a preferred embodiment, the reduction ratio of the FEMG gearbox
reduction gears
36-38 is 2:1, a ratio selected to better match crankshaft rotation speeds to
an efficient operating
speed range of the motor-generator 3.
1001201 FEMG System Hardware Mounting Embodiments.
1001211 As noted above, the FEMG assembly is preferably positioned such that
the motor-
generator 3 is located in a region of the engine compartment that is offset
below and to a lateral
side of the vehicle chassis rails supporting the engine. Fig. 10 illustrates
such an arrangement,
viewed from the front of the vehicle toward the rear. This figure shows the
relationships in this
embodiment between the motor-generator 3 and engine 8's crankshaft 47 (located
axially behind
the gearbox 16), oil pan 48, longitudinal chassis rails 49 and transverse
engine mount 50.
1001221 In the above FEMG arrangements the crankshaft 47, clutch-pulley-damper
unit 19 and
engine-end reduction gear 36 are located on the same rotation axis. In order
to ensure this
relationship is maintained, the FEMG gearbox should be located in front of the
engine in a
manner that ensures there is no relative movement between the engine and the
gearbox, either
transverse to the rotation axis of the crankshaft or around the crankshaft
axis.
1001231 While it would be possible to mount the FEMG gearbox in a manner that
does not
directly connect the gearbox to the engine (for example, by suspending the
FEMG gearbox from
a bracket connected to the chassis rails holding the engine), it is preferable
to directly couple the
gearbox to either an adjacent vehicle frame member or to the engine block.
Examples of FEMG
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gearbox-to-engine mounting bracket and corresponding arrangement of mounting
holes in the
gearbox is shown in Figs. 10-14.
1001241 In Fig. 10, the FEMG gearbox 16 is secured against rotation or
transverse motion
relative to the engine 8 by fasteners 306 to directly to the engine 8. Fig. 11
shows an alternative
approach in which a torque arm 307 (aka tie-rod) is attached at one end to an
anchor point 308 of
the FEMG gearbox 16, and at the opposite end to the adjacent frame rail 49,
thereby providing
non-rotation support of the gearbox 16.
1001251 A further alternative FEMG mounting approach is shown in Fig. 12. In
this
embodiment a mounting bracket 51 is provided with bolt holes 52 arranged
around the bracket to
align with corresponding holes in the engine block 8 which receive fasteners
to provide an
engine-centric fixed support for the FEMG gearbox. In this example, the flat
bottom of the
mounting bracket 51 is arranged to be positioned on top of elastomeric engine
mounts, as are
often used in commercial vehicle engine installations. The engine-side portion
of the mounting
bracket 51 is a portion of a bracket that must extend under and/or around the
clutch-pulley
damper unit to reach an FEMG gearbox mounting bracket portion to which the
gearbox may be
coupled, while ensuring there is sufficient clearance available within the
bracket to allow the
clutch-pulley-damper unit to rotate therein.
1001261 Figures 13 and 14 schematically illustrate the location of an FEMG
gearbox 16 on a
such a bracket and the corresponding distribution of fastener holes around the
FEMG reduction
gear 36 and the FEMG-side of the mounting bracket 51. Figures 13 and 14 both
show
circumferential arrangement of the corresponding fastener holes 53 on the FEMG
gearbox 16
and on the FEMG gearbox-side of the FEMG mounting bracket 51. In Fig. 14, the
engine-side
portion and the FEMG gearbox-side portion of the mounting bracket 51 are
linked by arms 54
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extending parallel to the engine crankshaft axis in spaces clear of the
rotating clutch-pulley-
damper unit 19 (not illustrated in these figures for clarity). The
schematically-illustrated arms 54
are intended to convey the mounting bracket arrangement concept, with the
understanding that
the connection between the engine-side and FEMG gearbox-side of the mounting
bracket may be
any configuration which links the front and rear sides of the bracket in a
manner that secures the
FEMG gearbox against motion relative to the engine crankshaft. For example,
the arms 54 may
be rods welded or bolted to the front and/or rear sides of the bracket, or the
arms may be portions
of an integrally-cast part that extends around the clutch-pulley-damper unit
19. Preferably, the
mounting bracket 51 is designed such that its FEMG gearbox-side portion has a
fastener hole
pattern that facilitates rotation of the FEMG gearbox relative to the bracket
("clocking") as
needed to index the gearbox at various angles to adapt the FEMG components to
various engine
configurations, for example in retrofitting an FEMG system to a variety of
existing vehicle or
stationary engine applications.
[00127] FEMG System Motor-Generator and Electronic Controls Embodiments.
[00128] An example of a motor-generator which is suitable for attachment to
the motor-
generator end of an FEMG gearbox is shown in Fig. 15. In this embodiment an
FEMG gearbox-
side 55 of the motor-generator 3 includes a plurality of studs 56 configured
to engage
corresponding holes in a mounting flange on the gearbox, such as the mounting
flange 44 shown
on the exemplary gearbox 16 in Fig. 9. In order to transfer torque between the
rotor of the
motor-generator 3 and the motor-generator-end reduction gear 38, a rotor bore
57 receives a
shaft (not illustrated) extending into a corresponding bore in reduction gear
38. The shaft
between the reduction gear 38 and the rotor of the motor-generator 3 may be a
separate
component, or may be integrally formed with either the rotor or the reduction
gear. The shaft
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also may pressed into one or both of the rotor and the reduction gear, or may
be readily separable
by use of a displaceable connection, such as axial splines or a threaded
connection.
1001291 The motor-generator 3 in this embodiment also houses several of the
electronic
components of the FEMG system, discussed further below, as well as low-voltage
connections
58 and high voltage connection 59 which serve as the electrical interfaces
between the motor-
generator 3 and the control and energy storage components of the FEMG system.
1001301 Preferably the motor-generator 3 is sized to provide at least engine
start, hybrid
electrical power generation and engine accessory drive capabilities. In one
embodiment, a motor
generator having a size on the order of 220 mm in diameter and 180 mm in
longitudinal depth
would, as shown in the graph of Fig. 16, provide approximately 300 Nm of
torque at zero rpm
for engine starting, and up to approximately 100 Nm near 4000 rpm for
operating engine
accessories and/or providing supplemental torque to the engine crankshaft to
assist in propelling
the vehicle. With a 2:1 reduction ratio of the FEMG gearbox, this motor-
generator speed range
is well-matched to a typical commercial vehicle engine's speed range of zero
to approximately
2000 rpm.
1001311 The FEMG motor-generator design is constrained by thermal, mechanical
and
electrical considerations. For example, while temperature rise of the motor
generator during
starting is relatively limited by the relatively short duration of the
starting operation, when the
motor-generator alone is driving one or more demanding engine accessories such
as the engine
cooling fan, the required torque output from the motor can be in the range of
50 Nm to 100 Nm.
In the absence of adequate motor-generator cooling the temperature rise during
sustained high-
torque output conditions could be significant. For example, at current density
J in the motor-
generator windings of 15 A/mm2, an adiabatic temperature rise could be on the
order of 30 C.
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For this reason, it is preferred that the FEMG motor-generator be provided
with forced cooling
such as the example shown in Fig. 17 in which engine coolant or cooling oil
(such as oil from the
gearbox oil circuit) circulates through a cooling fluid passage 60 in the
motor-generator. It is
particularly preferable that a portion 61 of the cooling passage 60 is also
routed to provide
cooling to the FEMG system electronic components mounted on the motor-
generator 3.
1001321 The type of electric machine selected may also introduce limitations
or provide specific
advantages. For example, in an induction-type electric motor, the breakdown
torque may be
increased 10-20% using an inverter (with a corresponding increase in flux),
and the breakdown
torque is typically high, e.g., 2-3 times the machine's rating. On the other
hand, if a permanent
magnet-type machine is selected, excessive stator excitement current must be
avoided to
minimize the potential for demagnetization of the permanent magnets. While
physical
arrangement and operating temperature can influence the point at which
demagnetization is
problematic, typically current values greater than two times the rated current
must be experienced
before significant demagnification is noted.
1001331 With such factors in mind, a preferred embodiment of the motor-
generator 3 would
have the capability of operating at 150% of its nominal operating range. For
example, the motor-
generator may have a rated speed of 4000 rpm, with a 6000 rpm maximum speed
rating
(corresponding to a maximum engine speed of 3000 rpm) and a capacity on the
order of 60 KW
at 4000 rpm. Such a motor-generator, operating at a nominal voltage of 400 V,
would be
expected to provide a continuous torque output of approximately 100 Nm, an
engine cranking
torque of 150 Nm for a short duration such as 20 seconds, and a peak starting
torque at zero rpm
of 300 Nm.
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1001341 The FEMG motor-generator 3, as well as the other components of the
FEMG system,
in this embodiment are controlled by the central FEMG control module 13, an
electronic
controller ("ECU"). With respect to the motor-generator, the FEMG control
module: (i) controls
the operating mode of the motor-generator, including a torque output mode in
which the motor-
generator outputs torque to be transferred to the engine accessories and/or
the engine crankshaft
via the clutch-pulley-damper unit, a generating mode in which the motor-
generator generates
electrical energy for storage, an idle mode in which the motor-generator
generates neither torque
or electrical energy, and a shutdown mode in which the speed of the motor-
generator is set to
zero (a mode made possible when there is no engine accessory operating demand
and the clutch
of the clutch-pulley-damper unit is disengaged); and (ii) controls the
engagement stated of the
clutch-pulley-damper unit (via components such as solenoid valves and/or
relays as required by
the type of clutch actuator being employed).
1001351 The FEMG control module 13 controls the motor-generator 3 and the
clutch-pulley-
damper unit 19 based on a variety of sensor inputs and predetermined operating
criteria, as
discussed further below, such as the state of charge of the energy store 11,
the temperature level
of the high voltage battery pack within the energy store, and the present or
anticipated torque
demand on the motor-generator 3 (for example, the torque required to achieve
desired engine
accessory rotation speeds to obtain desired levels of engine accessory
operating efficiency). The
FEMG control module 13 also monitors motor-generator- and engine crankshaft-
related speed
signals to minimize the potential for damaging the clutch components by
ensuring the
crankshaft-side and pulley-side portions of the clutch are speed-matched
before signaling the
clutch actuator to engage the clutch.
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1001361 The FEMG control module 13 communicates using digital and/or analog
signals with
other vehicle electronic modules, both to obtain data used in its motor-
generator and clutch-
pulley-damper control algorithms, and to cooperate with other vehicle
controllers to determine
the optimum combination of overall system operations. In one embodiment, for
example, the
FEMG control module 13 is configured to receive from a brake controller a
signal to operate the
motor-generator in generating mode to provide regenerative braking in lieu of
applying the
vehicle's mechanical brakes in response to a relatively low braking demand
from the driver. The
FEMG control module 13 is programmed to, upon receipt of such a signal,
evaluate the current
vehicle operating state and provide the brake controller with a signal
indicating that regenerative
braking is being initiated, or alternatively that electrical energy generation
is not desirable and
the brake controller should command actuation of the vehicle's mechanical
brakes or retarder.
1001371 Figure 18 provides an example of the integration of electronic
controls in an FEMG
system. In this embodiment the FEMG control module 13 receives and outputs
signals,
communicating bi-directionally over the vehicle's CAN bus with sensors,
actuators and other
vehicle controllers. In this example the FEMG control module 13 communicates
with the battery
management system 12 which monitors the state of charge of the energy store 11
and other
related energy management parameters, with an engine control unit 63 which
monitors engine
sensors and controls operation of the internal combustion engine, and with the
FEMG system's
electrical energy management components, including the power inverter 14 which
handles
AC/DC conversion between the AC motor-generator 3 and the DC portion of the
electrical bus
between the vehicle's DC energy storage and electrical consumers (not
illustrated in this figure).
The FEMG control module 13 further communicates with the vehicle's DC-DC
converter 10
which manages the distribution of electrical energy at voltages suitable for
the consuming
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device, for example, conversion of 400 V power from the energy store 11 to 12
V required by the
vehicle's 12 V battery 9 and the vehicle's various 12 V equipment, such as
lighting, radio, power
seats, etc.
1001381 Figure 18 also illustrates the communication of data as inputs into
the FEMG system
control algorithms from sensors 64 associated with the motor-generator 3, the
clutch-pulley-
damper unit 19's clutch, the various engine accessories 1 and the 12 V battery
9 (for example, a
motor-generator clutch position sensor 101, a motor-generator speed sensor
102, engine accessory
clutch positions 103, air compressor state sensors 104, dynamic heat generator
state sensors 105,
an FEMG coolant temperature sensor 106, an FEMG coolant pressure sensor 107,
and a 12 V
battery voltage sensor 108).
1001391 Many of the signals the FEMG control module 13 receives and exchanges
are
transmitted over the vehicle's SAE J1939 standard-compliant communications and
diagnostic bus
65 to/from other vehicle equipment 66 (for example, brake controller 111,
retarder controller 112,
electronic air control (EAC) controller 113, transmission controller 114, and
dashboard controller
115). Examples of the types of sensor and operational signals and variables
exchanged, and their
respective sources, are provided in Table 1.
1001401 Table 1
Signals/Variables to monitor Source of the signal
High voltage battery: state of charge (SOC) Coming from the Battery
Management System
BMS
High voltage battery: temperature Coming from the BMS
Vehicle speed J1939 message: Wheel-Based Vehicle
Speed
Engine torque J1939 message: Driver's Demand Engine -
Percent
Torque
Engine speed J1939 message: Engine Speed
Brake application status J1939 message: Brake Application
Pressure High
Range. Each axle
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Cooling fan clutch J1939 message: Requested Percent Fan
Speed
A/C compressor clutch J1939 message: Cab A/C Refrigerant
Compressor
Outlet Pressure
Air compressor clutch J1939 message: Intelligent Air Governor
(TAG)
Neutral Gear J1939 message: Transmission Current
Gear
Transmission Clutch J1939 message: Transmission Clutch
Actuator
Door open J1939 message: Open Status of Door 1 /
Open
Status of Door 2
Temperature of the cabin J1939 message: Cab Interior Temperature
Air brake system pressure J1939 message: Brake Primary Pressure
FEMG coolant temperature Temperature sensor mounted inside the
gearbox.
Engine oil temperature J1939 message: Engine Oil Temperature 2
Engine coolant temperature J1939: Engine Coolant Temperature
Intake manifold temperature J1939 message: Engine Intake Manifold 1
Air
Temperature (High Resolution)
MG rotating speed Encoder mounted on the Gearbox or the
MG
1001411 Outputs from the FEMG control module 13 include commands to control
the generation
of electrical energy or torque output from the motor-generator 3, commands for
engaging and
disengaging of the clutch of the clutch-pulley-damper unit 19, commands for
engaging and
disengaging the clutches 120 of individual engine accessories 1 (discussed
further below), and
commands for operation of an FEMG coolant pump 121.
1001421 FEMG Control Module System Control of FEMG System Components.
1001431 In addition to controlling the motor-generator and its clutched
connection to the engine
crankshaft, in this embodiment the FEMG control module has the ability to
control the
engagement state of any or all of the individual clutches connecting engine
accessories to the
accessory drive belt driven by pulley 5, thereby permitting the FEMG control
module to
selectively connect and disconnect different engine accessories (such as the
air conditioner
compressor 2 or the vehicle's compressed air compressor 1) to the accessory
drive according to
the vehicle's operating state. For example, when operating conditions permit,
the FEMG control
module's algorithms may prioritize electrical energy generation and determine
that some of the
engine accessories need not operate. Alternatively, the FEMG control module is
programmed to
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operate an engine accessory in response to a priority situation which requires
operation of the
accessory, even if doing so would not result in high overall vehicle operating
efficiency. An
example of the latter would be receipt of a compressed air storage tank low
pressure signal,
necessitating engagement of the air compressor's clutch and operation of the
pulley 5 at a high
enough speed to ensure sufficient compressed air is stored to meet the
vehicle's safety needs (e.g.,
sufficient compressed air for pneumatic brake operation). Another example
would be
commanding the motor-generator and the engine cooling fan clutch to operate
the engine cooling
fan at a speed high enough to ensure adequate engine cooling to prevent engine
damage.
1001441 Preferably, the FEMG control module is provided with engine accessory
operating
performance data, for example in the form of stored look-up tables. With
engine accessory
operating efficiency information, the ability to variably control the
operating speed of the motor-
generator to virtually any desired speed when the clutch-pulley-damper unit
clutch is disengaged,
and knowledge of the vehicle's operating state received from sensors and the
vehicle's
communications network, the FEMG control module 13 is programmed to determine
and
command a preferred motor-generator speed and a combination of engine
accessory clutch
engagement states that results in a high level of overall vehicle system
efficiency for the given
operating conditions.
1001451 While overall system efficiency may be improved by the presence of a
large number of
individual engine accessory clutches (including on/off, multi-stage or
variable-slip clutches), even
in the absence of individual accessory clutches the FEMG control module 13 may
use engine
accessory performance information to determine a preferred motor-generator
operating speed that
causes the pulley 5 to rotate at a speed that satisfies the current system
priority, whether that
priority is enhancing system efficiency, ensuring the heaviest engine
accessory demand is met, or
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another priority such as starting to charge the energy store 11 at a
predetermined time sufficiently
before an anticipated event to ensure sufficient electrical energy is stored
before the vehicle is
stopped. For example, the FEMG control module in this embodiment is programmed
to
determine the current state of charge of the energy storage 11 and the amount
of time available
before an anticipated driver rest period, and initiate motor-generator
charging of the energy store
11 at a rate that will result in enough energy being present at engine-shut-
off to support vehicle
system operation (such as sleeper compartment air conditioning) over the
anticipated duration of
the reset period (e.g., an 8-hour overnight rest period).
1001461 A similar rationale applies regardless of the number individual engine
accessory
clutches present, i.e., the FEMG control module may be programmed to operate
the motor-
generator 3 and the clutch-pulley-damper unit clutch 15 in a manner that meets
the priorities
established in the algorithms, regardless of whether a few, many or no
individual engine
accessory clutches are present. Similarly, a variety of prioritization schemes
may be programmed
into the FEMG control module to suit the particular vehicle application. For
example, in a
preferred embodiment, an energy efficiency priority algorithm may go beyond a
simple analysis
of what configuration of pulley speed and individual engine accessory clutch
engagement
provides an optimum operating efficiency for the highest priority engine
accessory, but may also
determine whether the operation of a combination of engine accessories at a
compromise pulley
speed will result in a greater overall system efficiency while still meeting
the priority accessory's
demand, i.e., operating each of the individual engine accessories at speeds
that are offset from
their respective maximum efficiency operating points if there is a pulley
speed which maximizes
overall vehicle efficiency while still meeting the vehicle system demands.
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[00147] FEMG Electric Energy Generation, Storage and Voltage Conversion
Embodiments.
1001481 The relationship between the power electronics and current
distribution in the present
embodiment is shown in greater detail in Fig. 19. The three phases of the
alternating current
motor-generator 3 are connected to the AD/DC power inverter 14 via high
voltage connections.
Electrical energy generated by the motor-generator 3 is converted to high
voltage DC current to
be distributed on a DC bus network 67. Conversely, DC current may be supplied
to the bi-
directional power invertor 14 for conversion to AC current to drive the motor-
generator 3 as a
torque-generating electric motor.
1001491 A known embodiment of a bi-directional AC/DC power inverter such as
inverter 14 as
shown in Fig. 20. This arrangement includes a six IGBT power transistor
configuration, with
switching signals provided from a controller (such as from the FEMG control
module 13) to
control lines 68A-68F based on a vector control strategy. Preferably, the
control module for the
power inverter 14 is located no more than 15 cm away from the power inverter's
IGBT board. If
desired to minimize electrical noise on the DC bus 67, a filter 69 may be
inserted between the
power inverter and the rest of the DC bus.
1001501 Figure 19 also shows two primary DC bus connections, the high voltage
lines between
the power inverter 14 and the energy store 11. The bi-directional arrows in
this figure indicate
that DC current may pass from the power inverter 14 to the energy store 11 to
increase its state of
charge, or may flow from the energy store to the DC bus 67 for distribution to
the power invertor
14 to drive the motor-generator 3 or to other DC voltage consumers connected
to the DC bus. In
this embodiment, a DC/DC voltage converter 70 is provided between the DC bus
and the energy
store 11 to adapt the DC voltage on the DC bus generated by the motor-
generator 3 to the
preferred operating voltage of the energy store. Figure 19 also shows that the
DC bus 67 also
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may be connected to an appropriate voltage converter, such as AC-DC voltage
converter 309 that
converts electric energy from an off-vehicle power source 310, such as a
stationary charging
station, to the voltage on DC bus 67 to permit charging of the energy store
independent from the
motor-generator 3 when the vehicle is parked.
1001511 In addition to the bi-directional flow of DC current to and from the
energy store 11, the
DC bus 67 supplies high voltage DC current to vehicle electrical consumers,
such as vehicle
lights, radios and other typically 12 V-powered devices, as well as to 120 V
AC current devices
such as a driver sleeper compartment air conditioner and/or a refrigerator or
cooking surface. In
both cases an appropriate voltage converter is provided to convert the high
voltage on the DC
bus 67 to the appropriate DC or AC current at the appropriate voltage. In the
embodiment shown
in Fig. 19, a DC/DC converter 71 converts DC current at a nominal voltage on
the order of 400 V
to 12 V DC current to charge one or more conventional 12 V batteries 72. The
vehicle's usual 12
V loads 73 thus are provided with the required amount of 12 V power as needed,
without the
need to equip the engine with a separate engine-driven 12 V alternator,
further saving weight and
cost while increasing overall vehicle efficiency. Figure 21 illustrates a
known embodiment of a
forward DC/DC converter such as DC/DC converter 71, in which the FEMG control
module 13
controls the conversion of high DC voltage from the DC bus 67 to the 12 V
output 75 of the
convertor by providing FEMG control signals to a transistor drive circuit 74
to manage the flow
of current through the primary winding 76 of the DC/DC converter's transformer
77.
1001521 The bi-directional high voltage DC/DC converter 70 is a so-called
"buck plus boost"
type of voltage converter, such as the known electrical arrangement as shown
in Fig. 22. Figure
23 shows how, when the electronically controlled switch S in Fig. 22 is
actuated, an input
voltage \in, drives in a pulsed manner a corresponding current oscillation
across the inductor L
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and capacitance C, resulting in a continuous output voltage vo, oscillating
smoothly about a
baseline voltage <vo>.
1001531 The desire to keep short the distance between the power invertor 14
and the motor-
generator's three AC phase lines may be satisfied by integrating several
electronic components
into the housing of a motor-generator, as shown in Fig. 24. On the side of the
motor-generator
opposite the side which would face the gearbox 16, wires for the three AC
phases 78A-78C
emerge and are connected to a high voltage portion 79 of a circuit board 84
(in Fig. 24 the
portion of the circuit board 84 to the left of the dashed line). To the right
of the AC phase
connections the power inverter is integrated into the circuit board 84, with
the IGBT pack 80
being located under the IGBT driver circuits 81.
1001541 Also co-located on the circuit board 84 is a section 82 containing
electrical noise-
suppressing electromagnetic interference (EMI) filter and DC power capacitors,
as well as
embedded micro controllers 83 of the FEMG ECU. The dashed line represents an
electrical
isolation 85 of the high voltage portion 79 from the low-voltage portion 86
which communicates
with the rest of the FEMG system and vehicle components via electrical
connectors 58. The high
voltage and high current either generated by the motor-generator 3 or received
by the motor-
generator 3 from the energy store 11 passes from the high voltage portion 79
of the circuit board
84 to the high voltage connection 59 via circuit paths (not illustrated)
behind the outer surface of
the circuit board.
1001551 Among the advantages of this high degree of motor-generator and power
electronics
integration are simplified and lower cost installation, minimizing of
electrical losses over longer-
distance connections between the motor-generator and the power electronics,
and the ability to
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provide cooling to the power electronics from the motor-generator's already-
present forced
cooling without the need for additional dedicated electronics cooling
arrangements.
1001561 FEMG System Energy Store and Battery Management Controller Embodiment.
1001571 The storage cells used in the energy store 11 in this embodiment are
Lithium-chemistry
based, specifically Li-Ion batteries. Li-Ion has several advantages over
conventional battery
chemistries such as Lead-acid, including lighter weight, better tolerance of
"fast-charging"
charge rates, high power density, high energy storage and return efficiency,
and long cycling life.
1001581 The energy store 11 is sized to be able to receive and supply very
large current flow
from/to the motor-generator 3, as a crankshaft-driven motor-generator can
generate kilowatts of
electrical power, and an energy-store-powered motor-generator can require 300
peak amperes of
high voltage current to start a diesel engine, in addition to requiring enough
high voltage current
to generate upwards of 100 Nm of torque to drive engine accessories when the
clutch-pulley-
damper unit is disengaged from the engine crankshaft.
1001591 While the super capacitors are capable of handling the peak current
demands of the
FEMG system, the battery portion of the energy store 11 is sized to be able to
provide sustained
current discharge rates and total energy output to meet the most demanding
current demand.
Based on experience with commercial vehicle operation, the battery portion of
the energy store
11 in this embodiment is sized to ensure satisfactory operation at the
equivalent of 58 KW for ten
minutes each hour (a power demand corresponding to operation of the engine
cooling fan at its
maximum speed solely by the motor-generator at regular intervals, as well as
concurrent air
conditioning and air compressor use). Calculations have shown that a discharge
of 58 KW for 10
minutes per hour, assuming an operating efficiency of the power inverter 14 of
95%, would
require withdrawal of 10 KWh (kilowatt-hours) of energy from the energy store
11. With a
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system voltage of 400 V, this amount of discharge requires the energy store
batteries to have a
storage capacity of approximately 15 Ah (ampere-hours).
1001601 In addition to calculating the minimum battery capacity to meet the
expected greatest
vehicle demand, the design of the battery portion of the energy store 11 takes
into account
baseline operational needs. For example, there is an operational desire to not
completely
discharge the energy store batteries, both to avoid encountering a situation
in which the energy
store cannot meet an immediate vehicle need (such as not being able to start
the engine when the
motor-generator is operated as an engine starting device) and to avoid
potential battery cell
damage from discharge to levels well below the battery cell manufacturer's
minimum
recommended cell operating voltage (for a 3.8 V-4.2 V Lithium-based battery
cell, typically not
below 1.5-2 V/cell). The design of the present embodiment's energy store
therefore includes the
requirement that the greatest discharge demand not discharge the battery
portion of the energy
store below 50% capacity. This requirement results in energy store 11 having a
battery capacity
of 30 Ah.
1001611 With a design target of 30 Ah and using Li-Ion battery cells each
having an individual
nominal voltage of 3.8 V and a discharge capacity of 33 Ah at a 0.3 C
discharge rate (such a
battery cell having a weight of 0.8 Kg (kilograms) and rectangular dimensions
of 290 mm x 216
mm x 7.1 mm), it was determined that the desired energy store capacity (30 Ah
at 400 V) could
be provided by packaging 4 individual battery cells in series to produce a 33
Ah battery module
having a nominal voltage of 15.2 V, and then connecting 28 of these battery
modules in series to
provide a battery pack with a 33 Ah capacity at a nominal voltage of 15.2
V/module x 28
modules = 425 V (actual operating voltage typically at or below 400V). This
battery pack has a
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weight (without housing) of approximately 90 Kg and a volume of approximately
50 liters, a
weight and size readily accommodated alongside a chassis rail of a commercial
vehicle.
1001621 The energy store 11 is provided with a battery management system (BMS)
12. The
BMS control module monitors the state of charge of the battery pack and
temperatures, handles
battery maintenance tasks such as cell balancing (the monitoring and adjusting
of charge states of
individual cells or groups of cells), and communicates battery pack status
information to the
FEMG control module 13. The battery management system 12 may be co-located
with the
FEMG control module 13 or at another location remote from the battery pack in
energy store 11;
however, installation of the battery management system 12 with the energy
store 11 permits
modular energy storage system deployment and replacement.
1001631 Another design consideration with energy store 11 receiving and
discharging large
amounts of high voltage current is the need for cooling. In the present
embodiment, among the
FEMG components requiring cooling, the energy store 11, the motor-generator 3,
the power
inverter 14, the gearbox 16 and the clutch 15 of the clutch-pulley-damper unit
19, the battery
store 11 has the greatest need for cooling to avoid damage from over-
temperature conditions.
The preferred temperature operating range of Li-Ion batteries is -20 C to 55
C. These
temperatures compare to operating temperature limits on the order of 150 C
for the motor-
generator 3, 125 C for the power invertor 14, and 130 C for the gearbox 16
(as well as the
clutch 15 if the clutch is an oil-bath wet clutch). In this embodiment,
significant savings in
complexity and cost are realized by having all of the primary FEMG components
being cooled
by the oil that is circulated in the gearbox for lubrication and cooling. This
is possible if the
energy store 11 battery pack receives the cooling oil as the first component
downstream of the
air/oil radiator which dissipates heat from the oil, i.e., before the cooled
oil is recirculated and
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absorbs heat from other FEMG components in the oil cooling circuit. This
arrangement ensures
the battery pack receives the cooling oil flow at a temperature that allows
the battery pack to
remain below 55 C, prior to the oil encountering higher-temperatures in the
motor-generator,
power inverter and gearbox.
1001641 FEMG System Energy Store State of Charge Determination Algorithm
Embodiments.
1001651 The state of charge of the energy store battery may be determined in a
variety of ways.
Fig. 25 is an example of a known battery management system state of charge
estimation control
algorithm usable in the present invention. In a first step S101 the battery
management system 12
initializes at start-up ("key on"). Step S102 symbolizes the BMS's estimation
of the state of
charge of the battery cells by the so-called "Coulomb counting" method, here,
by sampling cell
and group voltages (V, T) and temperatures to establish an estimated baseline
charge level, and
from this an initial point tracking the amount of current introduced into the
battery pack and
withdrawn from the battery pack (I).
1001661 However, while this approach to tracking state of charge has the
advantage of
providing real-time, very accurate current flow monitoring with relatively
inexpensive
technologies, it does not provide a reliable indication of the amount of
charge lost from the
battery cells due to the battery cell self-discharging phenomena resulting
from undesired
chemical reactions. Because this phenomena is strongly temperature dependent
and may result
in substantial charge loss not detected in step S102, in this embodiment the
battery management
system also executes an additional state of charge estimation step S103, a so-
called "prior in the
loop" approach. In this state of charge estimation approach, the open circuit
voltage of the
battery cells is measured and this voltage is compared to stored
voltage/charge state values to
provide an estimate of the battery charge level which inherently accounts for
previous self-
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discharge losses. In addition, by comparison with previously stored
information a rate of self-
discharge may be estimated, and from this self-discharge rate a state of
health of the battery may
be estimated (i.e., a high self-discharge rate indicating that the health of
the battery cells is
degraded as compared to when new).
1001671 A disadvantage of the "prior in the loop approach is that it cannot be
easily used in real
time, as the energy store 11's battery pack is in use to receive and discharge
high voltage current
as needed to support ongoing vehicle operation. As a result, the open-voltage-
based state of
charge and state of health estimations in step S103 are only performed when
the energy store's
battery is in a state in which no current is being received by or discharged
from the battery pack.
If the step S103 estimations cannot be made, this battery management system
routine proceeds to
step S104, and the most recent step S103 estimates of battery state of charge
and state of health
are used in the subsequent calculations.
1001681 Based on the cell and group voltages, temperatures, current input and
outputs from step
5102 and the most recent step 5103 correction factors to account for self-
discharge effects, in
step 5104 the battery management system calculates appropriate charging and
discharging power
limits available for operation of the energy store 11 within the FEMG system,
and executes a cell
balancing algorithm to identify battery cells requiring charge equalization
and apply appropriate
selective cell charging and/or discharging to equalize the cell voltages
within the 4-cell modules
and between the 28 modules. Cell balancing is of particular importance when Li-
Ion battery
cells are in use, as such cells can age and self-discharge at different rates
from one another. As a
result, over time the individual battery cells can develop different abilities
to accept a charge, a
condition that can result in one or more of the cells in a module (or between
different modules)
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being overcharged and others undercharged. In either case, significantly over-
or under-charged
battery cells may be irreparably damaged.
1001691 In step S105 the battery management system 12 communicates battery
pack status
information to the FEMG control module 13, including information on the power
limits required
for the current charge state and temperature of the battery cells. In parallel
in step S106 battery
cell data is stored in memory for use in future cell monitoring iterations.
Upon completion of the
battery pack status determination and cell balancing routines, control returns
to the beginning of
the charge estimation control loop, with self-discharge rate data being made
available at the start
of the loop for use in the subsequent steps.
1001701 FEMG System Operating Modes and Control Algorithm Embodiments.
1001711 In this embodiment, the FEMG system operates in several modes,
including generator
mode, motor mode, idle mode, off mode and stop/start mode. The mode selected
for the current
operating conditions is based at least in part on the current state of charge
of the energy store 11,
where the FEMG control module 13 is programmed to recognize based on data
received from the
battery management system 12 a minimum charge level, in this embodiment 20% of
charge
capacity, an intermediate charge level of 40%, and a maximum charge level of
80% (a level
selected to ensure the energy store is protected against overcharging of
cells, particularly in the
event that individual cell self-discharge has created a cell imbalance
condition).
1001721 In the generator mode, the clutch 15 is engaged and the motor-
generator 3 is driven to
generate electrical energy for storage whenever the energy store state of
charge is below the
minimum charge level, and the clutch will stay engaged until the intermediate
charge state level
is reached. Once the intermediate charge state level is reached, the FEMG
control module 13
switches between the generator, motor, idle and off modes as needed. For
example, if the motor-
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generator 3 is being operated with the clutch 15 disengaged to drive the
engine accessories, the
FEMG control module commands a switch to generator mode and engage the clutch
15 to charge
the energy store 11 when braking, deceleration or negative torque events occur
(so long as the
energy store 11 state of charge remains below the maximum charge state level).
1001731 When in the motor mode with the clutch 15 disengaged, the FEMG control
module 13
modulates the amplitude and frequency of the current being delivered by the
inverter 14 to the
motor-generator 3 in order to provide infinitely-variable speed control. This
capability permits
the motor-generator 3 to be operated in a manner that drives the pulley 5, and
hence the engine
accessories driven by the pulley 5, at a speed and torque output level that
meets the demands of
the current operating conditions without waste of energy due to operating at
unnecessarily high
speed and torque output levels. The FEMG system's variable output control over
the motor-
generator 3 has the additional benefit of minimizing the amount of stored
electrical energy that
must be delivered from the energy store 11, reducing energy store charging
needs and extending
the length of time the energy store 11 can supply high voltage current before
reaching the
minimum state of charge.
1001741 If the level of charge in the energy store 11 is above the minimum
level, there are no
braking, deceleration, or negative torque conditions present, and the engine
accessories are not
demanding torque from the motor-generator 3, the FEMG control module 13
initiates the idle
mode, in which the clutch 15 of the clutch-pulley-damper 19 is disengaged and
the motor-
generator "turned off," i.e., not operated to either generate electrical
energy for storage or
generate torque for driving the engine accessories.
1001751 In any of the generator, motor or off modes, the FEMG control module
may command
the clutch 15 be engaged if the engine requires torque output assistance from
the motor-
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generator, and simultaneously command supply of electrical energy from the
energy store 11 to
the motor-generator to convert into supplemental torque to be transferred to
the engine
crankshaft.
1001761 The FEMG control module is additionally programmed to protect against
unintended
over-discharge of the energy store 11. For example, in this embodiment when
the torque and
speed demand of engine cooling fan 7 is above 90% of its design maximum
demand, the clutch
15 of the clutch-pulley-damper 19 is engaged to mechanically drive the engine
cooling fan 7
(and as consequence also the other engaged engine accessories) from the engine
crankshaft. This
permits the motor-generator 3 to be operated in the idle or generator modes in
order to avoid a
potentially damaging deep discharge of the energy store 11, as well as
avoiding a state of charge
condition in which the stored energy is not sufficient to support engine-off
loads (for example,
engine starting or sleeper compartment support during engine-off rest
periods).
1001771 An additional operating mode is a starting mode, used for initially
starting a cold
engine and start-stop functionality (i.e., shut-down of the engine after a
stop and re-start when
travel is resumed). In this embodiment the start-stop function is controlled
by the FEMG control
module 13. When appropriate conditions exist (e.g., energy store 11 charge
state above a
minimum threshold for engine starting, vehicle speed of zero for a sufficient
period, transmission
in neutral or transmission clutch disengaged, vehicle doors closed, etc.), the
FEMG control
module signals the engine control module to shut down the engine, thereby
minimizing fuel
consumption and undesired engine idling noise. When the vehicle is to resume
motion, as
indicated by a signal such as release of the brake pedal or operation of the
transmission clutch,
the FEMG control module 13 commands engagement of clutch 15 and supply of
energy from the
energy store 11 to operate the motor-generator 3 to produce a large amount of
torque for engine
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starting. The delivery of engine starting torque occurs from a motor-generator
initial rotational
speed of zero in the case whether there was no engine accessory operation
demand during the
engine-off period (in which case there would be no need for pulley-crankshaft
speed matching,
as both sides of the clutch would be at zero speed). Alternatively, if the
motor-generator 3 had
been driving pulley 5 to power engine accessories during the engine shut down
period, the
motor-generator 3 would be commanded to slow to below a rotational speed at
when clutch
damage would occur when the clutch 15 is engaged. In the case of a dog clutch,
this may be at
or near zero speed, whereas a wet multi-plate clutch could better tolerate
some relative motion
between the pulley-side and stationary crankshaft-side of the clutch.
1001781 The FEMG system further can store sufficient energy to permit
operation of a dynamic
heat generator to pre-heat a cold engine prior to a cold start, significantly
reducing the resistance
a cold engine would present to the motor-generator during a cold start. The
use of a dynamic
heat generator also creates the opportunity to decrease the size, weight and
cost of the motor-
generator by reducing the peak cold-starting torque demand that the motor-
generator much be
designed to provide over the vehicle's expected operating conditions.
1001791 The peak cold-starting torque demand that the motor-generator much be
designed to
provide over the vehicle's expected operating conditions also may be reduced
by other assistance
devices. For example, the size of the motor-generator may be reduced if engine
starting torque is
supplemented by a pneumatic starter motor powered by the vehicle's compressed
air storage.
The size of a pneumatic starter motor may be minimized to ensure that it can
be located with the
FEMG components at the front of the engine because the pneumatic starter motor
need not be
sized to be able to start the engine by itself. Such a cold-starting assist
would be lower cost and
lower weight than the option of retaining a conventional electric engine
starter motor to rotate
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the engine flywheel, and would have negligible effect on the system energy
efficiency
improvements obtainable by the FEMG system.
1001801 FEMG System Engine Accessory Operating Speed and Motor-Generator
Operating
Speed Determination Algorithms.
1001811 An embodiment of an FEMG system control strategy is explained with the
assistance
of the flow charts of Figs. 26 and 27, following a brief discussion of the
underlying bases of the
strategy.
1001821 As a general matter, higher fuel savings may be obtained by maximizing
the amount of
time engine accessories and other components are electrically driven, rather
than by the
traditionally-provided engine mechanical power. A control strategy which
improves electrical
energy deployment is an essential part of obtaining these improvements. An
approach of the
present invention is to maximize the number of components that can be driven
electrically while
minimizing the number of electric machines required to drive the accessories.
Thus, rather than
providing most or all of the vehicle's power-demanding components with their
own electric
motors, in the present invention a single electric motor (such as motor-
generator 3) provides both
mechanical torque output and electric energy generation. This single motor-
generator approach
is coupled with a control strategy that ensures the needs of the most
demanding or highest
priority engine accessory or other component is met, while at the same time
minimizing
inefficient operation of other accessories or components by adapting their
operation to the extent
practical to the conditions that have been set to meet the greatest demand. In
the control strategy
discussed below, individual engine accessories are provided with clutches
which, depending on
the accessory, permits them to be selectively turned off, driven at a speed
dictated by the
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accessory having the greatest demand or highest priority, or driven at a
reduced speed using a
variable-engagement clutch.
1001831 When the engine accessories are being driven by the engine crankshaft,
i.e., when the
clutch 15 is engaged, each engine accessory is mechanically driven under a
"baseline" or
"original" control strategy (OCS) corresponding to how these accessories would
be operated in a
convention engine application without an FEMG system. In such a strategy the
accessories
having individual clutches are operated according to their individual baseline
control schemes,
with their clutches being fully engaged, partially engaged or disengaged in
the same manner as in
a non-hybrid internal combustion engine application.
1001841 In contrast, when the clutch-pulley-damper unit clutch 15 is
disengaged and the engine
accessories begin to be powered by the motor-generator 3 using energy from the
energy store 11,
the FEMG control module variably controls the speed of the pulley 5, and hence
the engine
accessory drive belt in a manner that meets the current vehicle needs without
providing more
accessory drive torque than is required in the current operating conditions.
Under such a variable
speed control (VSC) strategy, the FEMG control module 13 uses stored data
regarding the
operating characteristics of the individual engine accessories to
simultaneously control the
various accessories in a manner that further minimizes the amount of
electrical energy required
to drive the motor-generator 3 in motor mode (the FEMG control module 13 may
directly control
the accessories, or issue signals to other modules such as the engine control
module to command
execution of the desired accessory operations). Moreover, despite the fact
that the most efficient
or desirable operating speed has been mapped for each accessory, because the
motor-generator 3
drives all of the engine accessories on the same belt at one belt speed, when
one accessory is
operated at its optimum the others may be operating at suboptimal operating
points. For this
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reason the FEMG control module 13 compares the preferred operating speeds of
each of the
accessories to their speeds when driven by the motor-generator 3 at a speed
sufficient to meet the
greatest accessory demand, and determines whether the accessories' individual
clutches can be
actuated to produce an individual accessory speed closer to the individual
accessory's preferred
operating speed. If possible, the FEMG control module will override the usual
accessory clutch
control strategy and activate the accessory clutches as needed to deliver
individual accessory
speeds that provide improved efficiency.
1001851 Selection of appropriate engine accessory speeds begins with
determination of a
desired ideal operating speed of each accessory for the current operating
conditions, using a
control logic such as that shown in Fig. 26.
1001861 Upon starting the accessory speed determination algorithm, in step
S201 the FEMG
control module 13 retrieves from its memory 201 data regarding the current
vehicle operating
conditions obtained from the vehicle's sensors and other controllers, the
majority of which is
provided to the FEMG control module 13 via CAN bus in accordance with the SAE
J1939
network protocol, and determines the current operating conditions. This
operation is a predicate
to determining in step S202 whether the current operating conditions require
operation of a
particular accessory, such as the engine cooling fan. If the accessory is to
be turned on, the
routine proceeds to step S203 to determine whether the accessory is coupled to
the accessory
drive via an individual accessory multi-speed clutch.
1001871 If at step S203 the FEMG control module 13 determines such an
accessory clutch is
present, the routine proceeds to step S204 for a determination of what would
be the desired
accessory operating speed for the determined operating condition. In the
course of performing
step S204, the FEMG control module 13 accesses information 202, for example in
the form of
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look-up tables, characteristic curves or mathematical functions, from which it
can ascertain an
accessory operating speed at which the accessory operates efficiently in the
current operating
conditions. At step S205, the FEMG control module 13 compares the determined
desired
accessory operating speed to the speed of the accessory when its clutch is
fully engaged, and
modulates the accessory clutch to set an appropriate corresponding clutch
operating state (e.g., a
degree of clutch slip in a variable slip clutch or a particular reduction
ratio in a clutch with
discrete multiple speeds such as a 3-speed clutch). After modulating the
accessory clutch as
appropriate for the conditions, the FEMG control module 13 in step S207 checks
to see whether
the FEMG system motor mode has ended (i.e., determining whether the motor-
generator 3 is to
continue driving the accessory drive via pulley 5). If the system is still
operating in the motor
mode, control returns to the beginning of the accessory speed determination
process to continue
to assess accessory speed needs in view of the on-going operating conditions.
If the motor mode
is determined in step S207 to have ended, the Fig. 26 routine ends.
1001881 If at step S203 the FEMG control module 13 determines a multi-speed
accessory
clutch is not present (i.e., the accessory speed cannot be modulated relative
to the engine speed),
the routine proceeds directly to step S206 to command the accessory's clutch
to fully couple the
accessory to the accessory drive. Control then shifts to step S207, where the
motor mode
evaluation described above is performed.
1001891 The Fig. 26 algorithm is a component of the overall engine accessory
control strategy
of the present embodiment shown in Fig. 27. At the start of the FEMG system
algorithm the
FEMG control module 13 in step S301 retrieves from its memory 201 data
received from the
battery management system 12 to determine the state of charge of the energy
store 11. Next, in
step S302 the FEMG control module 13 retrieves from memory 201 data regarding
the current
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vehicle operating conditions obtained from the vehicle's sensors and other
controllers to
determine the current operating condition in which the engine is operating (in
this embodiment
the evaluation in step S302 provides the information required in step S201 of
the Fig. 26
accessory speed determination algorithm, and thus need not be repeated in step
S322, below).
1001901 After determining the current operating conditions, the FEMG control
module 13
determines the mode in which the FEMG system should operate and commands
engagement or
disengagement of the clutch 15 of the clutch-pulley-damper unit 19 accordingly
(step S303). If
the clutch 15 is to be in an engaged state in which the pulley 5 is coupled to
the damper 6 (and
hence to the engine crankshaft), the determination of how the accessories are
to be operated with
the engine driving pulley 5 may be performed by the FEMG control module 13, or
another
accessory control module. In Fig. 27, the FEMG control module 13 at step S311
passes control
of the engine accessory clutches to the vehicle's engine control module (ECM),
which can
determine engine accessory speeds in a manner comparable to the original
control strategy
(OCS). After hand-off of accessory control in step S311, processing ends at
step S312.
1001911 If at step S303 it is determined that motor-generator 3 is to
electrically drive the
accessories (i.e., the "motor mode" in which the clutch 15 of the clutch-
pulley-damper unit 19 is
in a disengaged state in which the pulley 5 is decoupled from the damper 6 and
hence the
crankshaft), in this embodiment the motor-generator 3 is controlled using the
variable speed
control (VSC) strategy.
1001921 The VSC strategy is implemented here by first determining for each
accessory a
preferred accessory operating speed in step S322, taking into account
information on all of the
accessories' characteristics and variables evaluated in step S321.
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1001931 At step S323 the FEMG control module 13 determines whether at least
one accessory
that could be driven by the motor-generator 3 is in "on," i.e., in a state in
which it is to be driven
via pulley 5 by motor-generator 3. If there is no accessory operation demand
under the current
conditions, control is returned to step S303.
1001941 If it is determined in step S323 that there is at least one accessory
in an "on" state, the
FEMG control algorithm in step S324 determines whether more than one accessory
needs to be
driven by the motor-generator 3 (i.e., more than one accessory "on"). If there
is only a single
accessory with a torque demand the control process proceeds with a subroutine
that is focused
solely on the operation of that one "on" accessory. Thus, at step S325 the
motor-generator speed
needed to drive the single accessory at its preferred operating speed is
calculated, the accessory's
individual drive clutch is commanded to fully engage in step S326, and the
motor-generator 3 in
step S327 is commanded to operate at the speed determined in step S325.
Because the motor-
generator's speed is variably-controlled in this embodiment, the pulley speed
5 may be set at
precisely the level required to drive the highest-demand engine accessory.
Control is then
returned to the start of the control algorithm.
1001951 If at step S324 it is determined that more than one accessory needs to
be driven by the
motor-generator 3, in accordance with the VSC strategy at step S328 the FEMG
control module
13 determines for each accessory what motor-generator speed would be needed to
drive the
accessory at its individual preferred accessory operating speed. The
calculated speeds are then
compared in step S329 to identify the highest motor-generator speed demand
from the "on"
accessories. The FEMG control module 13 then commands the individual clutch of
the accessory
needing the highest motor-generator speed to fully engage in step S330, in
step S331 commands
the motor-generator 3 to operate that the needed highest motor-generator
speed. As a part of the
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VSC strategy, in step S332 the FEMG control module controls the operation of
individual
accessory clutches of the remaining "on" accessories equipped with individual
clutches to adapt
these accessories' operation to the needed highest motor-generator speed set
in step S329. For
example, because the set motor-generator speed (the speed needed to serve the
accessory needing
the highest motor-generator speed) is higher than the speed needed by a
remaining accessories to
operate at their preferred speeds, if an accessory is equipped with an
individual clutch that can be
partially engaged (e.g., "slipped"), that clutch may be commanded to allow
enough slip to let its
accessory's speed be closer to its preferred operating speed (as determined in
step S322).
Control is then returned to the start of the control algorithm.
1001961 The following provides an example of the execution of the foregoing
method for the
case of a vehicle with three accessories driven from the crankshaft pulley, an
engine cooling fan,
an air conditioning compressor and an air compressor.
1001971 In this example the engine cooling fan is equipped with a fan clutch
with multiple
speed capability, such as a three speed or variable speed clutch (e.g., a
viscous fan clutch). The
air conditioner and air compressors have individual "on/off' clutches with
only engaged and
disengaged states. The FEMG control module 13 controls the operating state of
each of the
accessory clutches. The final speed of each accessory is a function of the
belt pulley drive ratio,
the motor-generator speed and the nature of the accessory's clutch (i.e.,
"on/off," variable slip or
multiple reduction ratio steps).
1001981 In this simplified example, for a given set of vehicle operating
conditions, the preferred
operating point of each accessory and the corresponding motor-generator speed
to obtain the
preferred operating point are: engine cooling fan operating at 1050 rpm (a fan
speed which
requires a motor-generator speed of 1050 rpm/1.1 ratio between fan pulley and
pulley 5, times
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2:1 gearbox reduction ratio = 1909 rpm); air conditioning compressor operating
at 1100 rpm
(corresponding to a motor-generator speed of 1294 rpm); and air compressor
operating at 2000
rpm (corresponding to a motor-generator speed of 2667 rpm).
1001991 If the FEMG control module 13 determines operation of the air
compressor is the
highest priority in the given conditions (for example, when stored compressed
air amount is
approaching minimum safety levels for pneumatic brake operation), the FEMG
control module 13
will command the motor-generator 3 to run at the 2667 rpm required to support
the air
compressor's 2000 rpm speed requirement. However, this motor-generator speed
is substantially
higher than the speeds required by the engine cooling fan or the air
conditioning compressor (at
the 2667 rpm motor-generator speed, the engine cooling fan speed and air
conditioning
compressor speed would be 1467 rpm and 2267 rpm, respectively). The FEMG
control module
13, having access to the engine accessory operating curves and depending on
the nature of the
other accessories' clutches, could then adjust the clutches' engagements to
operate the other
accessories closer to their preferred operating speeds. For example, if the
fan was equipped with
a variable slip clutch, the FEMG control module could command an amount of fan
clutch slip to
provide the preferred engine cooling fan speed of 1100 rpm. Similarly, while
the air conditioning
compressor may only have an "on/off' clutch and thus would be driven at 1467
rpm when its
clutch is engaged (rather than the preferred speed of 1050 rpm), the FEMG
control module could
control operation of the "on/off' clutch of the air conditioning compressor to
reduce the duty
cycle of the air conditioning compressor to a point that the current air
conditioning demand could
be met by only periodically operating the air conditioner at 1467 rpm. This
approach provides the
FEMG control module the ability to meet the needs of the currently-most
demanding engine
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accessory while reducing waste of energy by driving other accessories at
higher speeds than
necessary or at an unnecessarily high duty cycle (e.g., 100%).
[00200] In a further example, the engine may be equipped with accessories that
cannot be
disconnected from a drive belt driven by the pulley 5. In such a case, the
FEMG control module
13 may determine upon consideration of the operating curves that the greatest
overall system
energy efficiency may be obtained by compromise. For example, assume the air
compressor is
currently presenting the greatest demand and it would be preferable to operate
the air compressor
at the 2000 rpm speed at which the compressor is most efficient. If the FEMG
control module
then determines that an engine coolant pump being driven at the 2667 rpm motor
generator speed
would be operating at an undesirably low efficiency (i.e., operating at a pump
speed that
significantly increases the pump's energy consumption) and the vehicle
conditions allow the air
compressor to be operated at a lower speed (for example, where the current
need is "topping off'
the compressed air storage tanks, rather than meeting an urgent, safety-
related compressed air
demand), the FEMG control module can command a lower motor-generator speed at
which the
engine coolant pump operates at a higher level of efficiency (e.g., 2400 rpm),
even though the air
compressor operates at a slight decreased efficiency at this speed, with the
result that the overall
combined engine coolant pump and air compressor operation increases overall
system efficiency
as compared to operating these accessories at a motor-generator speed of 2667
rpm.
[00201] Figure 28 shows an illustration of an embodiment of the internal
arrangements of an
integrated electrified accessory unit 401 configured to be mounted to the side
of a commercial
vehicle frame member (aka, a frame rail), with the top cover and two sides
removed for clarity.
A back wall 410 of the integrated electrified accessory unit 401 includes a
mounting flange 411
provided for mounting to a commercial vehicle chassis frame rail 420 (see
Figs. 29A, 29B). A
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corresponding flange 412 is provided on the laterally opposite side of the
back wall 410 (not
illustrated in Fig. 28 for clarity). In this embodiment, the mounting flanges
and the back wall
410 of the integrated electrified accessory unit 401 are aligned in a
generally planar manner,
corresponding to the generally planar outside surface of a typical commercial
vehicle frame rail,
and are attached by fasteners (not shown). Any suitable approach to mounting
the integrated
electrified accessory unit 401 to the vehicle may be used, such as welding,
riveting and/or use of
adhesives.
1002021 The flanges 411, 412 in this embodiment are formed with support member
415, which
extends along the laterally opposite side walls of the integrated electrified
accessory unit 401 and
under the unit to support the integrated electrified accessory unit 401 on the
frame rail 420. The
support member 415 is arranged to place the top surface of the integrated
electrified accessory
unit 401 at approximately the same height as the top of the frame rail 420,
while the lower
portion of the integrated electrified accessory unit 401 extends below the
frame rail 420,
providing room for mounting of exterior components, such as heat exchangers
(discussed further,
below). The integrated electrified accessory unit also may be mounted using
isolating mounting
components such as vibration isolators to minimize vibration transfer between
the vehicle and
the components in the integrated electrified accessory unit. For example, the
components of the
integrated electrified accessory unit may be mounted to a subframe 452 that in
turn is located in
the housing by isolators 419 (for example, elastomeric devices).
1002031 Within the integrated electrified accessory unit 401 an integrated
electrified accessory
drive suite 430 is provided, in this embodiment including the accessories of:
an air conditioning
compressor 431, a power steering pump 433, pneumatic (air) compressor 432,
water pump 451
and thermodynamic heater 434. The integrated electrified accessory drive suite
430 further
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includes an electric motor 435, an accessory drive 436 by which torque from
the electric motor
435 is transferred to each of the accessories 431-434 when the individual
accessories' pulley
clutches are engaged, an inverter 437 which receives in this case DC power
from the vehicle
from which it generates AC power, and an accessory drive electronic control
unit (ECU) 438 that
in this embodiment is configured to control the operation of the inverter 437
to control the speed
and torque output of the electric motor 435, to control the operation of the
individual accessory
pulley clutches, and to exchange data with the vehicle via a communications
link. In this
example, the ECU 438's connection with the vehicle is via a wired connection
to a standards-
compliant control area network bus, but the communication between the ECU 438
and the
vehicle may also be made via a wireless communication link. The accessory
drive 436 may be a
one or a combination of various drive types, including a belt drive, a chain
drive and/or a gear
drive.
1002041 The enclosure of the integrated electrified accessory unit 401
embodiment in Figs. 28
and 29A, 29B is a weather-resistant structure, with water-resistant
connections penetrating the
walls of the enclosure as shown in Figs. 29A and 29B. This arrangement
provides protection
from the harsh environment of a vehicle undercarriage.
1002051 Fig. 29A shows an end view of side wall 416 of the enclosure, through
which there are
provided penetrations for return flow of air conditioning refrigerant from the
vehicle cab
(penetrations 441), and for input of high voltage (HV) from the vehicle to the
inverter
(penetration 442).
1002061 Fig. 29B is an end view of the housing wall 417 (omitted for clarity
in Fig. 28) that is
laterally opposite wall 416. Also visible at the left side of Fig. 29B (and at
the right side of Fig.
29A) is a liquid-to-air heat exchanger 450 that is mounted to the lower
portion of housing back
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wall 410, where the heat exchanger 450 is at least partially protected from
impacts from objects
from outside of the vehicle. The heat exchanger 450, which receives and
returns coolant via fluid
connection penetrations 443, provides supply and return for cooling to the
electric motor 435 and
the inverter 437 which are connected on a common cooling loop. Other
penetrations through the
housing wall 417 include: a low voltage (LV) connection 444 which may be used
for supplying
power to the ECU 438 and/or wired communications between the ECU 438 and the
vehicle;
penetrations 445, 446 for conducting coolant between the vehicle's coolant
system and the
integrated electrified accessory unit 401's thermodynamic heater 434 (and
optionally, to the
electric motor 435 and/or the inverter 437 in embodiments in which the coolant
is also used to
cool these components, freeing the heat exchanger 450 to be used to provide
general enclosure
cooling, cooling to another integrated electrified accessory unit 401
component, or be omitted
entirely); penetrations 447 associated with the air compressor 432 outputting
compressed air to
the vehicle; and a penetration 441 for output of air conditioning refrigerant
to the vehicle. The
present invention is not limited to the inclusion of the foregoing accessories
in the integrated
electrified accessory unit, but may include any accessory suitable to be
driven by the accessory
drive, such as a coolant pump.
1002071 Preferably, the accessories in the integrated electrified accessory
unit are pre-
assembled in the housing with their respective inlet and outlet lines to the
housing wall
penetrations already made prior to delivery of the completed unit. Further
preferably, the
penetrations are configured to facilitate rapid connection of external lines
between the integrated
electrified accessory unit and a vehicle. Such couplings minimize installation
labor costs, and
minimize or eliminate any need for an installer to open the integrated
electrified accessory unit
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housing during installation or subsequent maintenance activities outside of
the integrated
electrified accessory unit.
1002081 The integrated electrified accessory unit 401 is not limited to the
structure and location
discussed in the context of the foregoing description of the embodiment in
Figs. 28 and 29A, 29B.
For example, as long as the necessary services provided by the integrated
electrified accessory
unit can reach their respective vehicle components (e.g., compressed air to
the vehicle compressed
air storage and pneumatic brake system, air conditioning refrigerant to the
vehicle cab,
thermodynamically-heated coolant to the coolant system and/or the vehicle
cab), the integrated
electrified accessory unit may be located at any suitable location on the
vehicle. Similarly, the
consolidated electric drive of the accessory drive system may be expanded or
contracted as
necessary to accommodate more or fewer accessories, and some component of the
electric drive
system such as the ECU and/or the inverter may be arranged outside of the
housing of the
integrated electrified accessory unit. Further, the integrated electrified
accessory unit may
dispense with a housing, as shown in the embodiment in Fig. 30, where the
environmental
protection provided by a housing is not needed.
1002091 The foregoing disclosure has been set forth merely to illustrate the
invention and is not
intended to be limiting. Because such modifications of the disclosed
embodiments incorporating
the spirit and substance of the invention may occur to persons skilled in the
art, the invention
should be construed to include everything within the scope of the appended
claims and
equivalents thereof.
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1002101 Listing of reference labels:
1 air compressor
2 air conditioning compressor
3 motor-generator
4 drive unit gears
pulley
6 damper
7 engine cooling fan
8 engine
9 vehicle batteries
DC/DC converter
11 energy store
12 battery management system
13 FEMG electronic control unit
14 AC/DC power inverter
clutch
16 gearbox
17 flange shaft
18 rotor shaft
19 clutch-pulley-damper unit
engine coolant radiator
21 belt drive portions
22 clutch actuator
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23 clutch plates
24 clutch spring
25, 26 dog clutch elements
27 clutch throw-out rod
28 bolt holes
29 external splines
30 internal splines
31,32 dogs
33 spring
34 bearings
35 gearbox housing clamshell
36 pulley-end reduction gear
37 middle reduction gear
38 motor-generator-end reduction gear
39 bearings
40 holes
41 diaphragm
42 cover
43 shaft hole
44 mounting flange
45 mounting ring
46 nut
47 crankshaft
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48 oil pan
49 chassis rail
50 engine mount
51 mounting bracket
52 holes
53 holes
54 bracket arms
55 motor-generator gearbox side
56 mounting studs
57 rotor shaft bore
58 low-voltage connection
59 high-voltage connection
60 coolant passage
61 electronics cooling passage portion
62 engine control unit
64 sensors
65 SAE J1939 bus
66 vehicle equipment
67 DC bus
68A-68F control lines
69 transistor control line
70 DC/DC voltage converter
71 DC/DC converter
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72 12 V battery
73 12 V loads
74 DC/DC converter transistor drive circuit
75 DC/DC converter output
76 transformer primary winding
77 transformer
78 AC phase connection
79 circuit board
80 IGBT pack
81 IGBT driver circuits
82 EMI filter and DC capacitors
83 FEMG control module micro controller
101 motor-generator clutch position sensor
102 motor-generator speed sensor
103 engine accessory clutch positions
104 air compressor state sensors
105 dynamic heat generator state sensors
106 FEMG coolant temperature sensor
107 FEMG coolant pressure sensor
108 12V battery voltage sensor
111 brake controller
112 retarder controller
113 EAC controller
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114 transmission controller
115 dashboard controller
120 individual engine accessory clutches
121 FEMG coolant pump
201 FEMG control module memory
202 FEMG control module operating parameter storage
303 clutch throw-out rod bushing
304 busing bearing
305 compressed air fitting
306 fastener
307 torque arm
308 anchor point
309 AC-DC converter
310 off-vehicle power
401 integrated electrified accessory unit
410 housing back wall
411, 412 mounting flange
415 support member
416, 417 housing side wall
419 isolator
420 vehicle frame rail
430 integrated electrified accessory drive suite
431 air conditioning compressor
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432 air compressor
433 power steering pump
434 thermodynamic heater
435 electric motor
436 accessory belt drive
437 inverter
438 electronic control unit
441 refrigerant penetrations
442 high voltage penetration
443 heat exchanger coolant inlet and outlet penetrations
444 low voltage penetration
445, 446 coolant inlet and outlet penetrations
447 compressed air outlet penetration
450 heat exchanger
451 water pump
452 subframe
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