Note: Descriptions are shown in the official language in which they were submitted.
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ELECTRONIC OIL PUMP
CROSS-REFERENCE
[0001] The present application is a divisional of Canadian Patent
Application
No. 2,762,251, filed September 30, 2009, which is a national phase entry of
International Patent Application No. PCT/US2009/059007, filed September 30,
2009.
FIELD OF THE INVENTION
[0002] The present invention relates to a method of controlling an
engine to
which lubricant is supplied by an oil pump.
BACKGROUND
[0003] Snowmobiles conventionally have a lubrication system that uses an
oil
pump that is mechanically driven by an engine of the snowmobile. This type of
oil
pump is generally referred to as a mechanical oil pump.
[0004] When the engine operates on a four-stroke principle, the
lubricant is
stored in an oil tank that is usually connected or integrated to the engine,
such as an
oil pan. The mechanical oil pump pumps the lubricant from the oil tank to make
it
circulate through the engine. After circulating through the engine, the
lubricant is
returned to the oil tank.
[0005] When the engine operates on a two-stroke principle, the
lubricant is
stored in an oil tank that is usually spaced apart from the engine. The
mechanical oil
pump pumps the lubricant from the oil tank to the crankcase of the engine.
From the
crankcase, the lubricant flows to the cylinders where it is combusted with a
mixture of
fuel and air. Since the lubricant is combusted by the engine, the oil tank
occasionally
needs to be refilled with lubricant for the engine to operate properly.
[0006] By having the mechanical oil pump driven by the engine, the
amount
of lubricant being pumped is directly proportional to the speed of the engine.
Therefore, the faster the engine turns, the more lubricant is being pumped by
the
mechanical oil pump, and the relationship between engine speed and the amount
of
lubricant being pumped is a linear one. However, the actual lubricant
requirements of
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an engine, especially in the case of an engine operating on a two-stroke
principle, are
not linearly proportional to the engine speed.
[0007] Some mechanical oil pumps driven by the engine are also linked
to the
throttle lever that is operated by the driver of the vehicle, such that the
position of the
throttle lever adjusts the output of the mechanical oil pump. Although this
provides
for an improved supply of lubricant to the engine, it does not account for
other factors
which affect the actual lubricant requirements of the engine such as ambient
air
temperature and altitude.
[0008] For a two-stroke engine, the actual lubricant requirement
depends, at
least in part, on the power output of the engine, not only engine speed. The
higher the
power output, the more lubricant is required. There are instances during the
operation
of the two-stroke engine where the engine speed is high, but where the power
output
of the engine is low. In such instances, the mechanical oil pump driven by the
engine
provides a lot of lubricant even though the actual requirements are low. One
such
instance is when the track of the snowmobile is slipping on a patch of ice. In
this
instance the engine speed is high due to the slippage, but the actual power
output is
low. There are other instances where the actual lubricant requirements are
lower than
what would be provided by a mechanical oil pump driven by the engine. For
example, at start-up, all of the lubricant that was present in the engine when
it was
stopped has accumulated at the bottom of the crankcase. The accumulated
lubricant
would be sufficient to lubricate the engine for the first few minutes of
operation,
however the mechanical oil pump, due to its connection to the engine, adds
lubricant
regardless. Therefore, in the case of an engine operating on the two-stoke
principle,
using a mechanical oil pump results in more lubricant being consumed by the
engine
than is actually required. This also results in a level of exhaust emissions
that is
higher than a level of exhaust emissions that would result from supplying the
engine
with its actual lubricant requirements since more lubricant gets combusted
than is
necessary.
[0009] The actual lubricant requirements of an engine for a snowmobile
are
also a function of one or more of the altitude at which the snowmobile is
operating,
the engine temperature, and the position of the throttle lever, to name a few.
Since
snowmobiles are often operated in mountainous regions and that temperatures
can
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vary greatly during the winter, the actual lubricant requirements of the
engine can be
significantly affected by these factors and therefore need to be taken into
account.
Conventional snowmobile lubrication systems using mechanical oil pumps, due to
the
linear relationship between the engine speed and the amount of lubricant being
pumped, cannot take these into account.
[0010] In the prior art, mechanisms were provided on some snowmobiles
which would modify the amount of lubricant provided by the oil pump per engine
rotation. These mechanisms provided two (normal/high, or normal/low) or three
(normal/high/low) oil pump settings. Although these settings provided some
adjustment in the amount of lubricant being provided to the engine by the oil
pump,
since the pump is still mechanically connected to the engine, the relationship
is still a
linear one, and thus does not address all of the inconveniences described
above. The
settings simply provide consistently more or less lubricant, as the case may
be, than at
the normal settings.
[0011] Therefore, there is a need for an oil pump that can provide an
engine,
such as the engine of a snowmobile, with an amount of lubricant that is at or
near the
actual lubricant requirements of the engine.
[0012] There is also a need for an oil pump that can supply lubricant
to an
engine, such as the engine of a snowmobile, non-linearly with respect to the
engine
speed and other factors.
[0013] Finally, since snowmobiles are used during the winter, the low
ambient
temperature causes the lubricant to be very viscous when the engine is first
started and
becomes less viscous as the engine warms up (thereby warming the lubricant),
thus
affecting the efficiency with which the lubricant can be pumped. Therefore,
when the
lubricant has a high viscosity, the oil pump may be unable to supply the
amount of
lubricant necessary for the proper operation of the engine under certain
conditions.
Also, different lubricants, at the same temperature, have different
viscosities.
Therefore, similar issues may be associated with lubricants having a normally
high
viscosity.
[0014] Therefore, there is also a need for an oil pump that can take into
account varying lubricant viscosities and a method of use thereof.
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SUMMARY
[0015] It is an object of the present invention to ameliorate at least
some of the
inconveniences present in the prior art.
[0016] In one aspect, the invention provides a method of controlling
an engine
having an electronic oil pump supplying lubricant thereto. The electronic oil
pump
includes an actuator operatively connected to at least one piston. The method
comprises; causing the actuator to move the at least one piston toward a full
stroke
position; sending a signal to an electronic control unit (ECU) when the at
least one
piston reaches the full stroke position; determining a time taken to reach the
full
stroke position based on the signal; estimating a time for returning the at
least one
piston to a fully retracted position based on the time taken to reach the full
stroke
position; determining a cycle time of the pump based the time taken to reach
the full
stroke position and the estimated time for returning the at least one piston
to the fully
retracted position; returning the at least one piston to the fully retracted
position; and
limiting a maximum allowable engine speed based at least in part on the cycle
time.
[0017] In a further aspect, the actuator includes an electromagnetic
coil.
Causing the actuator to move the at least one piston toward a full stroke
position
includes applying a current to the electromagnetic coil. Returning the at
least one
piston to the fully retracted position includes stopping to apply the current
to the
electromagnetic coil.
[0018] In an additional aspect, the method further comprises applying
the
current to the electromagnetic coil for longer than is necessary to move the
at least
one piston toward the full stroke position.
[0019] In a further aspect, the method further comprises operating the
engine
in a fault mode if the signal is not received by the ECU within a
predetermined
amount of time.
[0020] In another aspect, a method of controlling an engine having an
electronic oil pump supplying lubricant thereto is provided. The electronic
oil pump
includes at least one lubricant inlet, at least one lubricant outlet, at least
one piston,
and an actuator operatively connected to the at least one piston. The piston
is
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movable between a fully retracted position and a full stroke position to pump
lubricant from the at least one inlet to the at least one outlet. The actuator
includes an
electromagnetic coil. The
method comprises: applying a current to the
electromagnetic coil to move the at least one piston from the fully retracted
position
toward the full stroke position; sending a signal to an electronic control
unit (ECU)
when the at least one piston reaches the full stroke position; determining a
time taken
to reach the full stroke position from the fully retracted position based on
the signal;
determining a power-on time based on the determined time taken to reach the
full
stroke position from the fully retracted position; and returning the at least
one piston
to the fully retracted position by stopping to apply the current to the
electromagnetic
coil once the power-on time has elapsed.
[0021] In a
further aspect, the method further comprises: estimating a time for
returning the at least one piston to the fully retracted position from the
full stroke
position based on the time taken to reach the full stroke position from the
fully
retracted position; determining an estimated cycle time of the pump based the
time
taken to reach the full stroke position from the fully retracted position and
the
estimated time for returning the at least one piston to the fully retracted
position from
the full stroke position; and limiting a maximum allowable engine speed based
at least
in part on the estimated cycle time.
[0022] In an additional aspect, the method further comprises: calculating a
calculated cycle time of the pump based on at least one current operating
condition of
the engine; and reducing the maximum allowable engine speed when the estimated
cycle time is greater than the calculated cycle time.
[0023] In a
further aspect, the method further comprises further reducing the
maximum allowable engine speed until one of: the estimated cycle time is less
than or
equal to the calculated cycle time; and a time since stopping to apply the
current to the
electromagnetic coil is greater than the time for returning the at least one
piston to the
fully retracted position from the full stroke position.
[0024] In an
additional aspect, the method further comprises: sensing a speed
of the engine; and determining a cycle time of the pump based at least on the
sensed
engine speed.
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[0025] In a further aspect, the power-on time is based on the cycle
time.
[0026] In an additional aspect, the power-on time is longer than the
time taken
to reach the full stroke position from the fully retracted position.
[0027] In a further aspect, the power-on time is the time taken to
reach the full
stroke position from the fully retracted position.
[0028] In another aspect, a method of controlling an engine having an
electronic oil pump supplying lubricant thereto is provided. The electronic
oil pump
includes at least one lubricant inlet, at least one lubricant outlet, at least
one piston,
and an actuator operatively connected to the at least one piston. The piston
is
movable between a fully retracted position and a full stroke position to pump
lubricant from the at least one inlet to the at least one outlet. The actuator
includes an
electromagnetic coil. The method comprises: applying a current to the
electromagnetic coil to move the at least one piston from the fully retracted
position
toward the full stroke position; sending a signal to an electronic control
unit (ECU)
when the at least one piston reaches the full stroke position; determining a
time taken
to reach the full stroke position from the fully retracted position based on
the signal;
continuing to apply the current to the electromagnetic coil when the time
taken to
reach the full stroke position from the fully retracted position is above a
predetermined time; and stopping to apply the current to the electromagnetic
coil
when the time taken to reach the full stroke position from the fully retracted
position
is less than the predetermined time.
[0029] In an additional aspect, the method further comprises limiting
engine
performance when the time taken to reach the full stroke position from the
fully
retracted position is above the predetermined time.
[0030] In a further aspect, the method further comprises determining an
estimated cycle time of the pump based the time taken to reach the full stroke
position
from the fully retracted position.
[0031] In an additional aspect, the method further comprises
calculating a
calculated cycle time of the pump based on at least one current operating
condition of
the engine.
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[0032] In a
further aspect, the method further comprises determining a power-
on time based on the estimated and calculated cycle times.
[0033] In an
additional aspect, the power-on time is a difference between the
calculated cycle time and the estimated cycle time.
[0034] In a further aspect, the power-on time is greater than the time
taken to
reach the full stroke position from the fully retracted position.
[0035] In an
additional aspect, the method further comprises returning the at
least one piston to the fully retracted position by stopping to apply the
current to the
electromagnetic coil once the power-on time has elapsed.
[0036] In yet another aspect, a method of controlling an engine having an
electronic oil pump supplying lubricant thereto is provided. The electronic
oil pump
includes at least one lubricant inlet, at least one lubricant outlet, at least
one piston,
and an actuator operatively connected to the at least one piston. The piston
is
movable between a fully retracted position and a full stroke position to pump
lubricant from the at least one inlet to the at least one outlet. The actuator
includes an
electromagnetic coil. The
method comprises: applying a current to the
electromagnetic coil to move the at least one piston from the fully retracted
position
toward the full stroke position; determining if the at least one piston has
reached the
full stroke position within a predetermined time; continuing to apply the
current to the
electromagnetic coil after the at least one piston has reached the full stroke
position if
the at least one piston has reached the full stroke position after the
predetermined
time; and stopping to apply the current to the electromagnetic coil once the
at least
one piston has reached the full stroke position if the at least one piston has
reached the
full stroke position before the predetermined time.
[0037] In a further aspect, the method further comprises limiting engine
performance if the at least one piston has reached the full stroke position
after the
predetermined time.
[0038] In an
additional aspect, the method of further comprises determining a
power-on time based on a time taken for the at least one piston to reach the
full stroke
position.
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[0039] In a further aspect, the method further comprises, if the at
least one
piston has reached the full stroke position after the predetermined time,
stopping to
apply the current to the electromagnetic coil once the power-on time has
elapsed.
[0040] Embodiments of the present invention each have at least one of
the
above-mentioned objects and/or aspects, but do not necessarily have all of
them. It
should be understood that some aspects of the present invention that have
resulted
from attempting to attain the above-mentioned objects may not satisfy these
objects
and/or may satisfy other objects not specifically recited herein.
[0041] Additional and/or alternative features, aspects, and advantages
of
embodiments of the present invention will become apparent from the following
description, the accompanying drawings, and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0042] For a better understanding of the present invention, as well as
other
aspects and further features thereof, reference is made to the following
description
which is to be used in conjunction with the accompanying drawings, where:
[0043] Figure 1 is a right side elevation view of a snowmobile in
accordance
with the invention;
[0044] Figure 2 is a perspective view from a front, right side, of an
oil tank
and electronic oil pump assembly to be used in the snowmobile of Fig. 1;
[0045] Figure 3 is a perspective view from a rear, left side, of the oil
tank and
electronic oil pump assembly of Fig. 2;
[0046] Figure 4 is a perspective view from a front, right side, of
internal
components of the snowmobile of Fig. 1, with some of the components removed
for
clarity;
[0047] Figure 5 is a perspective view from a rear, right side, of internal
components of the snowmobile of Fig. 1, with some of the components removed
for
clarity;
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[0048] Figure 6A is an exploded view of a first embodiment of the
electronic
oil pump used in the assembly of Fig. 2;
[0049] Figure 6B is an exploded view of a second embodiment of the
electronic oil pump used in the assembly of Fig. 2;
[0050] Figure 7 is a perspective view from a rear, left side, of an
alternative
embodiment of the electronic oil pumps of Fig. 6A and 6B;
[0051] Figure 8 is a perspective view from a front, right side, of the
electronic
oil pump of Fig. 7;
[0052] Figure 9 is a schematic illustration of some of the various
sensors and
components present in the snowmobile of Fig. 1; and
[0053] Figure 10 is a logic diagram illustrating a control of the
electronic oil
pump.
DETAILED DESCRIPTION
[0054] The present invention will be described in combination with a
snowmobile. However it is contemplated that at least some aspects of the
present
invention could be used in other applications.
[0055] Fig. 1 illustrates a snowmobile 10 including a forward end 12
and a
rearward end 14 which are defined consistently with a travel direction of the
snowmobile 10. The snowmobile 10 includes a frame 16 which includes a tunnel
18
and an engine compartment 20. A front suspension 22 is connected to the frame.
The
tunnel 18 generally consists of one or more pieces of sheet metal bent to form
an
inverted U-shape. The tunnel 18 extends rearwardly along the longitudinal
centerline
61 of the snowmobile 10 and is connected at the front to the engine
compartment 20.
An engine 24, which is schematically illustrated in Fig. 1, is carried by the
engine
compartment 20 of the frame 16. A steering assembly (not indicated) is
provided, in
which two skis 26 are positioned at the forward end 12 of the snowmobile 10
and are
attached to the front suspension 22 through a pair of front suspension
assemblies 28.
Each front suspension assembly 28 includes a ski leg 30, a pair of A-arms 32
and a
shock absorber 29 for operatively connecting the respective skis 26 to a
steering
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column 34. Other types of front suspension assemblies 28 are contemplated,
such as a
swing-arm or a telescopic suspension. A steering device such as a handlebar
36,
positioned forward of a rider, is attached to the upper end of the steering
column 34 to
allow the rider to rotate the ski legs 30 and thus the skis 26, in order to
steer the
snowmobile 10.
[0056] An endless drive track 65 is positioned at the rear end 14 of
the
snowmobile 10. The endless drive track 65 is disposed generally under the
tunnel 18,
and is operatively connected to the engine 24. The endless drive track 65 is
driven to
run about a rear suspension assembly 42 for propelling the snowmobile 10. The
rear
suspension assembly 42 includes a pair of slide rails 44 in sliding contact
with the
endless drive track 65. The rear suspension assembly 42 also includes one or
more
shock absorbers 46 which may further include a coil spring (not shown)
surrounding
the individual shock absorbers 46. Suspension arms 48 and 50 are provided to
attach
the slide rails 44 to the frame 16. One or more idler wheels 52 are also
provided in
the rear suspension assembly 42.
[0057] At the front end 12 of the snowmobile 10, fairings 54 enclose
the
engine 24, thereby providing an external shell that not only protects the
engine 24, but
can also be decorated to make the snowmobile 10 more aesthetically pleasing.
Typically, the fairings 54 include a hood (not indicated) and one or more side
panels
which can be opened to allow access to the engine 24 when this is required,
for
example, for inspection or maintenance of the engine 24. In the particular
snowmobile 10 shown in Fig. 1, the side panels can be opened along a vertical
axis to
swing away from the snowmobile 10. A windshield 56 is connected to the
fairings 54
near the front end 12 of the snowmobile 10. Alternatively the windshield 56
can be
connected directly to the handlebar 36. The windshield 56 acts as a wind
screen to
lessen the force of the air on the rider while the snowmobile 10 is moving.
[0058] A straddle-type seat 58 is positioned atop the frame 16. A rear
portion
of the seat 58 may include a storage compartment or can be used to accommodate
a
passenger seat (not indicated). Two footrests 60 are positioned on opposite
sides of
the snowmobile 10 below the seat 58 to accommodate the driver's feet.
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[0059] Turning now to Figs. 2 and 3, the lubrication system of the
snowmobile 10 includes an oil tank 70 and an electronic oil pump 72A. The oil
tank
70 is disposed in the engine compartment 20 (see Fig. 4) and is shaped so as
to fit
between the various other components located in the engine compartment 20. The
oil
tank 70 is preferably fixed to the frame 18 and is preferably positioned
slightly behind
the engine 24. Since the oil tank 70 is not directly connected to the engine
24, the oil
tank 70 is partially isolated from the vibration generated by the engine 24.
The oil
tank 70 is preferably made of plastic. As seen in Fig. 3, a portion 74 of the
oil tank 70
is translucent to permit visible inspection as to the level of lubricant in
the oil tank 70.
Level markers 76 provide a visual indication as to the relative level of
lubricant in the
tank 70. A cap 78 is provided to open or close an oil filling opening (not
shown) on
the oil tank 70. A hose 80 extends from an upper portion of the oil tank 70 to
a
component of the engine 24, such as a water pump (not shown), to provide
lubricant
thereto. When the oil tank 70 is filled up above the level of the upper end of
the hose
80, the hose 80 is filled with lubricant. The lubricant present in the hose 80
is then
gradually fed by gravity to the component to which the hose 80 is connected.
The
volume of lubricant in the hose 80 is preferably sufficient to provide
lubricant to the
component until the oil tank 70 is once again filled up above the level of the
upper
end of the hose 80.
[0060] As can also be seen in Figs. 2 and 3 the electronic oil pump 72A is
disposed externally of the oil tank 70. An inlet 82 of the electronic oil pump
72A is
connected directly to a bottom of the oil tank 70 on a side of the oil tank 70
opposite
the side of the oil filling opening. The inlet 82 is preferably connected to
the lowest
point of the oil tank 70. The electronic oil pump 72A has four outlets 84, 86.
The
two outlets 84 are connected to hoses 88. As seen in Fig. 4, the hoses 88 are
connected to the two exhaust valves 90 of the engine 24 (one exhaust valve 90
per
cylinder 92.) to supply lubricant thereto. One possible construction of the
exhaust
valves 90 is described in United States patent 6,244,227, issued June 12,
2001. It
should be understood that other constructions of the exhaust valves 90 are
contemplated which would not deviate from the present invention. The two
outlets 86
are connected to hoses 94. As seen in Fig. 4, the hoses 94 are connected to
the
crankcase 96 of the engine 24. Each hose 94 fluidly communicates with a crank
chamber (not shown) inside the crankcase 96 (one crank chamber per cylinder
92) to
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supply lubricant to the crankshaft bearings (not shown) and the other
components
located therein. It should be understood that should the engine 24 have more
or less
cylinders 92, that the electronic oil pump 72A would have a number of outlets
84 and
86 that correspond to the number of cylinders. For example, should the engine
24
have three cylinders 92, then the electronic oil pump 72A would have three
outlets 84
and three outlets 86. It is also contemplated that two electronic oil pumps
72A could
be used should the number of outlets become too great for a single electronic
oil
pump 72A. It is also contemplated that the electronic oil pump 72A could
provide
lubricant only to the cylinders 92 (via the crankcase 96) and that the exhaust
valves 90
would be lubricated in some other way. In this case, an electronic oil pump
72C
having only two outlets 86 (for an engine 24 having two cylinders 92) as shown
in
Figs. 7 and 8 would be used. It is also contemplated that the electronic oil
pump 72A
could provide lubricant to other components and parts of the engine 24.
[0061] Turning now to Figs. 4 and 5, a cooling system, an exhaust
system, and
a positioning of the electronic oil pump 72A relative to these systems will be
described. The cooling system has a coolant tank (not shown) that supplies
coolant to
the remainder of the system via pipe 98. Coolant can also flow back to the
coolant
tank via the pipe 98 when the coolant expands in the cooling system as the
temperature of the coolant increase. Similarly, gas bubbles in the coolant
system can
flow to the coolant tank via pipe 98. Coolant in the system flows in coolant
hose 100
to T-connector 102, and from T-connector 102 to coolant hose 104. From coolant
hose 104, coolant enters coolant passages (not shown) inside the engine 24
thereby
absorbing heat from the engine 24. The coolant then exits the engine 24 via
coolant
hose 106. From coolant hose 106, the coolant enters a thermostat 108. When the
temperature of the coolant is below a predetermined temperature, the
thermostat
directs the coolant back to coolant hose 100, and from there the coolant is re-
circulated through the engine 24 as described above. When the temperature of
the
coolant is above the predetermined temperature, the thermostat 108 prevents
the
coolant from entering coolant hose 100 and redirects the coolant to coolant
hose 110.
It is contemplated that the thermostat 108 could redirect only a portion of
the coolant
to coolant hose 110 and let a remainder of the coolant flow to coolant hose
100. From
coolant hose 110, the coolant flows to a first heat exchanger 112 to be
cooled. The
first heat exchanger 112 forms the upper central part of the tunnel 18. From
the first
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heat exchanger 112, the coolant flows to coolant hose 114. From coolant hose
114,
the coolant flows to a second heat exchanger 116 (the majority of which is
hidden by
engine 24 in Fig. 4) located in the rear portion of the engine compartment 20
to be
further cooled. It is contemplated that the first and second heat exchangers
112, 116
cooled be located elsewhere on the snowmobile 10 and that only one of the
first and
second heat exchangers 112, 116 could be used. From the second heat exchanger
116, coolant flows to coolant hose 118. From coolant hose 118, coolant flows
to T-
connector 102, to coolant hose 104, to the engine 24 to coolant hose 106 and
back to
thermostat 108 as described previously. The thermostat 108 causes the coolant
to
flow through the first and second heat exchangers 112, 116 until the
temperature of
the coolant is once again below the predetermined temperature.
[0062] The exhaust system receives exhaust gases from the exhaust
ports 120
(Fig. 4) of the engine 24. The exhaust valves 90 regulate the flow of the
exhaust
gases through the exhaust ports 120. An exhaust manifold (not shown) is
connected
to the exhaust ports 120. The exhaust gases flow from the exhaust ports,
through the
exhaust manifold to a muffler 122 (Fig. 5). From the muffler 122 the exhaust
gases
flow through an exhaust pipe (not shown) to the atmosphere.
[0063] As can be seen in Figs. 4 and 5, the electronic oil pump 72A is
disposed in proximity to heat generating components of the snowmobile 10.
These
heat generating components include coolant hoses 110 and 114, heat exchanger
116,
muffler 122, and engine 24. The coolant hoses 110 and 114, and heat exchanger
116
generate heat due to the hot coolant flowing through them. The muffler 122
generates
heat due to the hot exhaust gases flowing through it. The engine 24 generates
heat
due to the combustion events taking place inside the cylinders 92. The
electronic oil
pump 72A is located proximate enough to these heat generating components that
the
heat generated by them, when the snowmobile 10 is in operation, heats up the
lubricant contained in the electronic oil pump 72A. Therefore, by being
heated, the
lubricant maintains a viscosity level that allows it to be easily pumped by
the
electronic oil pump 72A. It is contemplated that locating the electronic oil
pump 72A
in proximity to at least one of these heat generating components could be
sufficient to
maintain the viscosity level of the lubricant in the electronic oil pump 72A.
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[0064] Turning now to Fig. 6A, details of the electronic oil pump 72A
will be
described. The electronic oil pump 72A is what is known as a reciprocating
solenoid
pump. The electronic oil pump 72A has a body 124 having the inlet 82 and the
outlets 84, 86 integrally formed, over-molded, or press fit therewith. The
body 124 is
preferably made of plastic or other electrically insulating material. It is
contemplated
that the body could be made of an electrically conductive material covered
with an
electrically insulating material. Alternatively, the body could be made of an
electrically conductive material and be provided with a sleeve therein made of
electrically insulating material. As can be seen, the outlets 86 are larger
than the
outlets 84. This is because more lubricant needs to be supplied to the
cylinders 92 by
the outlets 86 than needs to be supplied to the exhaust valves 90 by the
outlets 84.
Two 0-rings 126 are provided around the outlet 82 to prevent lubricant present
in the
oil tank 70 to seal the connection between the outlet 82 and the oil tank 70.
A filter
128 is disposed in the outlet 82 to prevent debris from entering the
electronic oil
pump 72A. A stopper 130 is inserted in the body 124 centrally of the outlets
84, 86.
A first electrical lead 131 electrically connects the stopper 130 to the ECU
160. It
should be understood that the first electrical lead 131 may not connect the
stopper 130
directly to the ECU 160. An 0-ring 132 disposed around the stopper 130 seals
the
connection between the stopper 130 and the body 124. Check valves 134 are
disposed in the passage of the outlets 84 to prevent lubricant from entering
the body
124 via the outlets 84. Similarly, check valves 136 are disposed in the
passage of the
outlets 86 to prevent lubricant from entering the body 124 via the outlets 86.
The
check valves 134, 136 are sized according to the size of their corresponding
outlets
84, 86. A piston carrier 138 has four pistons 140, 142 thereon. As can be seen
the
pistons 142 are larger than the pistons 140. The pistons 142 are used to pump
lubricant through the larger outlets 86, and the pistons 140 are used to pump
lubricant
through the smaller outlets 84. A spring 144 is disposed between the piston
carrier
138 and the stopper 130. A cap 145, made of plastic or other electrically
insulating
material, is disposed at the end of the spring 144, between the spring 144 and
the
stopper 130. The piston carrier 138 is connected to a plunger 149 of an
armature 150.
The plunger 149 extends through a pole 146. An 0-ring 148 is provided around
the
pole 146 to prevent lubricant present in the body 124 from leaking into the
section of
the electronic oil pump 72A that is opposite the side of the pole 146 where
the piston
carrier 138 is connected (i.e. to the left of the pole 146 in Fig. 6A). The
armature 150
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is made of magnetizable material such as iron. The armature 150 is slidably
disposed
inside a sleeve 152. The sleeve 152 is disposed in the center of a coil bobbin
154 and
is press-fitted over the pole 146. The coil bobbin 154 has a coil 156 wound
around it.
The ends of the coil 156 are connected to connector 158 which is used to
connect the
electronic oil pump 72A to the electronic control unit (ECU) 160 (see Fig. 4).
The
coil bobbin 154 is disposed inside a solenoid housing 162. The solenoid
housing 162
is made of electrically conductive material. A washer 164 is disposed between
the
coil bobbin 154 and the end of the solenoid housing 162. A spring 166 is
disposed
between the armature 150 and the sleeve 152. Three threaded fasteners 168 are
used
to fastened the solenoid housing 162 to the body 124. When the solenoid
housing 162
is fastened to the body 124, all of the components shown therebetween in Fig.
6A,
except connector 158, are housed inside the volume created by the solenoid
housing
162 and the body 124. A second electrical lead 169 electrically connects one
of the
fasteners 168 to the ECU 160. It should be understood that the second
electrical lead
169 may not connect the one of the fasteners 168 directly to the ECU 160.
[0065] The electronic oil pump 72A operates as follows. Lubricant
enters the
body 124 via inlet 82. Current is applied to the coil 156 via the ECU 160, as
will be
described in greater detail below. The current applied to the coil 156
generates a
magnetic field. The armature 150 slides towards the body 124 (to the right in
Fig.
6A) under the effect of the magnetic field. The piston carrier 138 and the
pistons 140,
142 move together with the armature 150. This movement of the armature also
causes spring 144 to be compressed between the piston carrier 138 and the cap
145
and stopper 130. The movement of the pistons 140, 142 towards the body 124
compresses the lubricant contained in the body 124 and causes the lubricant to
be
expelled from the electronic oil pump 72A through the outlets 84, 86, via the
check
valves 134, 136. When the portion of the piston carrier 138 which houses the
spring
144 makes contact with the stopper 130, an electrical path is created between
the
leads 131 and 169, thus closing the circuit formed by the leads 131 and 169,
the pump
72A and the ECU 160. This signals the ECU 160 that the pump 72A has reached
its
full stroke position. Thus, the ECU 160 can determine the time it takes to
reach the
full stroke position by calculating the time elapsed between the time when
current is
applied to the coil 156 to the time when the electrical path between the leads
131 and
169 is closed. When the piston carrier 138 reaches this position, the
lubricant has
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been expelled from the electronic oil pump 72A. The ECU 160 then stops
applying
current to the coil 156 which then no longer creates a magnetic field. Since
the
armature no longer applies a force to compress the spring 144, the spring 144
expands, thereby returning the pistons 140, 142, the piston carrier 138, and
the
armature 150 to their initial positions (towards the left in Fig. 6A) and
opening the
electrical path between the leads 131 and 169. The cap 145 provides electrical
insulation between the stopper 130 and the spring 144, thereby preventing
electrical
connection between the leads 131 and 169 when the pump 72A is not in its full
stroke
position. The spring 166 prevents the armature 150 from hitting the end of the
sleeve
152, which would generate noise and potentially damage the armature 150, and
counteracts the force of the spring 144 to place the armature 150 in the
correct initial
position. By returning to their initial positions, the pistons 140, 142 create
a suction
inside the body 124. The suction 124, along with gravity, causes more
lubricant to
flow inside the body 124 via the inlet 82. The check valves 134, 136 prevent
the
lubricant that was expelled from the electronic oil pump 72A from re-entering
the
body via outlets 84, 86. Once the armature 150 returns to its initial
position, the ECU
160 applies current to the coil 156 and the cycle is repeated.
[0066] It is contemplated that other types of electronic oil pumps
could be
used. For example, the armature 150 of the reciprocating electronic oil pump
72A
described above could be replaced with a permanent magnet. In this embodiment,
applying current in a first direction to the coil 156 causes movement of the
permanent
magnet, and therefore of the pistons 140, 142, in a first direction, and
applying current
in a second direction to the coil 156 causes movement of the permanent magnet
in a
second direction opposite the first one. Therefore, by being able to control
the
movement of the permanent magnet in both direction, this type of pump provides
additional control over the reciprocating motion of the pump when compared to
the
solenoid pump 72A described above.
[0067] Fig. 6B illustrates an alternative embodiment of the pump 72A,
pump
72B. The pump 72B has all of the elements of the pump 72A with the addition of
a
cap 151 and a third lead 139. The third lead 139 electrically connects the
piston
carrier 138 to the ECU 160. It should be understood that the third electrical
lead 139
may not connect the piston carrier 138 directly to the ECU 160. The cap 151,
which
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is made of plastic or other electrically insulating material, is disposed at
the end of the
plunger 149, between the plunger 149 and the piston carrier 138. When the
piston
carrier 138 makes contact with the pole 146, an electrical path is created
between the
leads 139 and 169, thus closing the circuit formed by the leads 139 and 169,
the pump
72A and the ECU 160. This signals the ECU 160 that the pump 72B has reached
its
fully retracted position. The cap 151 provides electrical insulation between
the piston
carrier 138 and the plunger 149, thereby preventing electrical connection
between the
leads 139 and 169 when the pump 72B is not in its fully retracted position.
Thus, the
ECU 160 can determine the time it takes to reach a full stroke by calculating
the time
elapsed between the time when the electrical path between the leads 139 and
169 is
opened to the time when the electrical path between the leads 131 and 169 is
closed.
Similarly, the ECU 160 can determine the time it takes to reach the fully
retracted
position by calculating the time elapsed between the time when the electrical
path
between the leads 131 and 169 is opened to the time when the electrical path
between
the leads 139 and 169 is closed.
[0068] As described above, the ECU 160 is electrically connected to
the
connector 158 of the electronic oil pump 72A to supply current to the coil 156
and the
ECU 160 also receives a feedback from the oil pump 72A via leads 131 and 169.
The
ECU 160 is connected to a power source 161 (Fig. 9) and, based on inputs from
one
or more of the various sensors described below with respect to Fig. 9,
regulates when
current from the power source 161 needs to be applied to the electronic oil
pump 72A
such that the proper amount of lubricant is supplied to the cylinders 92 of
the engine
94. As seen in Fig. 9, an engine speed sensor (RPM sensor) 170 is connected to
the
engine 24 and is electrically connected to the ECU 160 to provide a signal
indicative
of engine speed to the ECU 160. The engine 24 has a toothed wheel (not shown)
disposed on and rotating with a shaft of the engine 24, such as the crankshaft
(not
shown) or output shaft (not shown). The engine speed sensor 170 is located in
proximity to the toothed wheel (see Fig. 4 for example) and sends a signal to
the ECU
160 each time a tooth passes in front it. The ECU 160 then determines the
engine
rotation speed by calculating the time elapsed between each signal. An air
temperature sensor (ATS) 172 is disposed in an air intake system of the engine
24,
preferably in an air box (not shown), and is electrically connected to the ECU
160 to
provide a signal indicative of the ambient air temperature to the ECU 160. A
throttle
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position sensor (TPS) 174 is disposed adjacent a throttle body or carburetor
(not
shown), as the case may be, of the engine 24 and is electrically connected to
the ECU
160 to provide a signal indicative of the position of the throttle plate
inside the throttle
body or carburetor to the ECU 160. An air pressure sensor (APS) 176 is
disposed in
an air intake system of the engine 24, preferably in an air box (not shown),
and is
electrically connected to the ECU 160 to provide a signal indicative of the
ambient air
pressure to the ECU 160. A coolant temperature sensor (CTS) 178 is disposed in
the
cooling system of the engine 24, preferably in one of coolant hoses 100, 104,
or 106,
and is electrically connected to the ECU 160 to provide a signal indicative of
the
temperature of the coolant to the ECU 160. It is contemplated that the CTS 178
could
be integrated to the thermostat 108. A counter 180 is electrically connected
to the
ECU 160. The counter 180 can be in the form of a timer and provide a signal
indicative of time to the ECU 160. The counter 180 could also count the number
of
times the electronic oil pump 72A has been actuated. The counter 180 could
also be
linked to the engine 24 to provide a signal indicative of the number of
rotations of a
shaft of the engine 24 to the ECU 160. It is contemplated that the RPM sensor
170
could integrate the function of the counter 180 to provide a signal indicative
of the
number of rotations of a shaft of the engine 24 to the ECU 160 in addition to
the
signal indicative of engine speed. It is also contemplated that there could be
two (or
more) counters 180, one acting as a timer, and the other counting the number
of
rotations of the engine 24 or the number of times the electronic oil pump 72A
has
been actuated.
[0069] The electronic oil pump 72A has an inherent time delay that is
determined by an elapsed time from the time an electric current is received by
the
electronic oil pump 72A from the ECU 160 to the time that lubricant is
actually
initially expelled from the electronic oil pump 72A. Due to manufacturing
tolerances,
this time delay varies from one electronic oil pump 72A to the other.
Therefore, the
electronic oil pump 72A has a specific time delay 182 associated therewith.
The time
delay 182 is stored on a computer readable storage medium, such as a bar code
or a
RFID tag, associated with the electronic oil pump 72A. The time delay 182 is
provided to the ECU 160 and is taken into account when regulating the
application of
current to the electronic oil pump 72A such that the actual operation of the
electronic
oil pump 72A corresponds to the desired operation of the electronic oil pump
72A as
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calculated by the ECU 160. An example as to how this is achieved for fuel
injectors,
and which could be adapted for use on electronic oil pumps, is described in
United
States Patent 7,164,984, issued January 16, 2007. In oil pump 72B, this time
delay
does not need to be provided since the time at which lubricant is actually
initially
expelled from the electronic oil pump 72B corresponds to when the electrical
path
between the leads 139 and 169 is opened.
[0070] Due to manufacturing tolerances, the amount of lubricant being
expelled per stroke by the electronic oil pump 72A varies from one electronic
oil
pump 72A to the other. Therefore, the electronic oil pump 72A has a specific
pump
output 183 associated therewith that corresponds to the actual amount of
lubricant
being expelled per stroke by the electronic oil pump 72A. The pump output 183
is
stored on a computer readable storage medium, such as a bar code or a RFID
tag,
associated with the electronic oil pump 72A. The computer readable storage
medium
could be the same as the one used for the time delay 182 or could be a
different one.
The pump output 183 is provided to the ECU 160 and is taken into account when
regulating the application of current to the electronic oil pump 72A such that
the
actual operation of the electronic oil pump 72A corresponds to the desired
operation
of the electronic oil pump 72A as calculated by the ECU 160. It is
contemplated that
only one of the time delay 182 and the pump output 183 may be provided for the
electronic oil pump 72A.
[0071] Turning now to Fig. 10, a method of controlling the electronic
oil
pump 72A will be described. A method of operating the electronic oil pump 72B
is
the same as the method of operating the electronic oil pump 72A, unless
specifically
explained otherwise below.
[0072] The method is initiated at step 200, once the key (not shown) is
inserted in the snowmobile 10 or once the engine 24 is started. In the present
method,
a boolean variable called "Cold Limit" is used to indicate whether the
lubricant being
used by the pump 72A has a viscosity which is higher than expected during
normal
operation of the snowmobile 10. A "Cold Limit" which is set to "true"
indicates such
a higher viscosity. A "Cold Limit" which is "false" indicates that the
lubricant has a
viscosity within a range which is expected during normal operation of the
snowmobile. As previously explained, a low lubricant temperature would result
in a
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high viscosity of the lubricant (herein the name "Cold Limit"). Although the
name of
the boolean variable "Cold Limit" suggests a relationship with temperature, it
should
be understood that using a lubricant which has a high viscosity, even at
normal
operating temperatures of lubricant in a snowmobile 10, could also result in
the
boolean variable "Cold Limit" being set to "true" during the present method.
At step
202, the boolean variable "Cold Limit" is set to false since no data is
available at this
point to determine otherwise. Then at step 204, the ECU limits the maximum
engine
speed to a value of A RPM, which corresponds to an engine speed limit during
normal
operation of the snowmobile 10.
[0073] At step 206, the ECU 160 then applies current to the coil 156 of the
oil
pump 72A. Then at step 208, the ECU 160 determines if a signal which indicates
that
the circuit including the leads 131 and 169 is closed is received within a
predetermined time limit t 1. As previously described, this signal is
indicative that the
that the pump 72A has reached its full stroke position. If the signal is not
received
within ti, then at step 210 the ECU 160 stops applying current to the coil 156
of the
oil pump 72A to return the oil pump 72A to its fully retracted position. Since
not
receiving a signal within ti at step 208 indicates that the oil pump 72a is
unable to
reach its full stroke position, and therefore unable to efficiently pump
lubricant, at
step 212 the ECU 160 enters a fault operation mode. The problem could be that
one
of the components of the pump 72A is faulty or that the lubricant inside the
oil pump
72A is too viscous for the oil pump 72A to pump the lubricant. The fault
operation
mode limits the performance of the engine 24 so as to prevent damaging the
engine
24. It is contemplated that the ECU 160 could also enter a fault mode if a
signal
which indicates that the circuit including the leads 131 and 169 is closed is
received in
less than another predetermined time limit, which would indicate that there is
no
lubricant present in the oil pump 72A. If at step 208, a signal is received
within the
time ti, then the ECU 160 continues to step 214.
[0074] At step 214, the ECU 214 determines the estimated cycle time
(ECT).
The estimated cycle time corresponds to the sum of the time it took the pump
72A to
reach its full stroke position (full stroke time, FST) and of the estimated
time it will
take the pump 72A to reach it fully retracted position (estimated return time,
ERT).
The full stroke time is determined from the time it took to receive the signal
from the
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circuit including the leads 131 and 169 that the circuit is closed as
described above.
The estimated return time is determined from various experimentally determined
maps stored in the ECU 160 or other electronic storage devices accessible by
the ECU
160. The maps provide estimated return times for various full stroke times.
Should
the full stroke time not correspond to a value in the maps, the ECU 160 can
interpolate the estimated return time from two known values in the maps. As
previously described, a long full stroke time is indicative of a high
lubricant viscosity.
A high lubricant viscosity, as should be understood, makes it more difficult
for the
pump 72A to suck lubricant back inside the pump 72A. Therefore, the longer the
full
stroke time is, the longer the estimated return is. In a method using the oil
pump 72B,
the estimated return time only needs to be determined in this manner (i.e.
using maps)
the first time step 214 is performed. When the step 214 is subsequently
performed,
the estimated return time used is the time elapsed between the circuit
including the
leads 131 and 169 becoming opened and the circuit including the leads 139 and
169
becoming closed. As should be understood, the estimated cycle time determined
at
step 214 determines the maximum frequency at which the pump 72A can be used.
[0075] From step 214, the ECU 160 continues to step 216 and determines
if
the "Cold Limit" variable has a value of "true". The first time step 216 is
performed,
the value of the "Cold Limit" variable is "false" and the method continues to
step 222
where the ECU 160 stops applying current to the coil 156 of the oil pump 72A
to
return the oil pump 72A to its fully retracted position. When step 216 is
subsequently
performed, if the value of the "Cold Limit" variable is "true" as a result of
step 230
described below, then the ECU 160 continues to step 218. As previously
described,
when the "Cold Limit" variable is "true", it is as a result of the lubricant
having a high
viscosity, which can be caused by the lubricant being at a low temperature. As
should
be understood, the viscosity of the lubricant can therefore be reduced by
heating the
lubricant. As described in more detail in PCT application no.
PCT/US2008/055477,
published as WO 2009/002572 Al on December 31, 2008, by continuing to apply
current to the coil 156 after the pump 72A has reached its full stroke
position, the coil
156 generates heat which can help reduce the viscosity of the lubricant. At
step 218,
the ECU 160 determines a maximum amount of time (power-on time, POT) for which
the current can be applied to the coil 156 of the pump 72A before having to
return the
oil pump 72A to its fully retracted position in order to initiate the next
pumping cycle.
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The power-on time corresponds to the difference between the calculated cycle
time
(CCT) and the estimated cycle time (ECT) determined at step 214. The
calculated
cycle time is the cycle time at which the pump 72A needs to be operated in
order to
supply the amount of lubricant required by the engine 24 at the current
operating
conditions. The ECU 160 uses the signals received from at least some of the
sensors
described above with respect to Fig. 9, including the engine speed sensor 170,
to
calculate the calculated cycle time. International publication WO 2009/002572
Al
describes some methods in which the cycle time can be calculated by the ECU
160,
but other methods are contemplated. Generally, the faster the engine speed is,
the
shorter the calculated cycle time will be, however the relationship between
the engine
speed and the calculated cycle time does not need to be a linear one. From
step 218,
the ECU 160 continues to step 220 where it determines if the amount of time
elapsed
since the current has been applied to the coil 156 of the pump 72A (time t2)
is greater
than or equal to the power-on time. If it is not, then the ECU 160 will
continue to
loop back to step 220 until that is the case. Once the time t2 is greater than
or equal to
the power-on time, the ECU 160 continues to step 222 where the ECU 160 stops
applying current to the coil 156 of the oil pump 72A to return the oil pump
72A to its
fully retracted position.
[0076] From step 222, the ECU 160 continues to step 224. At step 224
the
ECU 160 determines if the amount of time elapsed since step 222 (time t3) is
greater
than the estimated return time determined at step 214. As should be
understood, the
time t3 also corresponds to the amount of time elapsed since the circuit
including the
leads 131 and 169 has been opened. If at step 224, the time t3 is greater than
the
estimated return time, then the ECU 160 continues to step 232. If at step 224,
the
time t3 is not greater than the estimated return time, then at step 226 the
ECU 160
determines if the estimated cycle time determined at step 214 is greater than
the
calculate cycle time (which is calculated as described above with respect to
step 218).
If the estimated cycle time is not greater than the calculated cycle time,
then the pump
72A can adequately supply lubricant to the engine 24 under the current
operating
conditions (i.e. the pump 72A can perform a complete pumping cycle faster than
what
is required) and the ECU 160 returns to step 224. If however, the estimate
cycle time
is greater the calculated cycle time, then the pump 72A cannot adequately
supply
lubricant to the engine 24 (i.e. the pump 72A cannot perform a complete
pumping
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cycle within the required amount of time) and the ECU 160 continues to step
228. At
step 228 the ECU reduces the maximum allowable engine speed by an amount of B
RPM (10 RPM for example), and then sets the "Cold Limit" variable to "true"
such
that when the method subsequently comes to step 216, steps 218 and 220 will be
performed to warm the lubricant as described above. From step 230, the ECU 160
returns to step 224 and if the time t3 is not greater than the estimated
return time, then
step 226 is performed again. If the engine 24 was previously operating at a
speed
greater than the maximum allowable engine speed calculated at step 228, then
the
engine speed has been reduced and therefore the calculated cycle time should
have
increased. If at step 226 the estimated cycle time is still not greater than
the
calculated cycle time, then step 228 is repeated. Step 228 will continue to be
performed until either the time t3 is greater than the estimated return time
(step 224)
or the estimated cycle time is greater than the calculated cycle time (step
226),
whichever occurs first.
[0077] In a method using the oil pump 72B, step 224 could be replace by a
step where the ECU 160 determine if a signal indicative that the circuit
including the
leads 139 and 169 has been closed has been received. If this circuit is
opened, then
the ECU 160 continues to step 226 and if it is closed the ECU 160 continues to
step
232.
[0078] Once it is determined at step 224 that the time t3 is greater than
the
estimated return time, then at step 232 the ECU determines if the maximum
allowable
engine speed is less than the engine speed limit during normal operation of
the
snowmobile 10 of A RPM. If it is not less than A RPM, then the ECU 160
continues
to step 236, set the value of the variable "Cold Limit" to false, and then
returns to step
206 where it will apply current to the coil 156 of the pump 72A at the
beginning of
the next pumping cycle. If the maximum allowable engine speed is less than A
RPM,
the ECU will increase the maximum allowable engine speed by a predetermined
amount of C RPM (but without exceeding A RPM), so as to gradually increase the
maximum allowable engine speed each time step 234 is performed. From step 234
the ECU 160 returns to step 206 where it will apply current to the coil 156 of
the
pump 72A at the beginning of the next pumping cycle.
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[0079] Modifications and improvements to the above-described
embodiments
of the present invention may become apparent to those skilled in the art. The
foregoing description is intended to be exemplary rather than limiting. The
scope of
the present invention is therefore intended to be limited solely by the scope
of the
appended claims.
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