U.S. patent application number 09/681659 was filed with the patent office on 2002-11-21 for variable pressure oil pump.
Invention is credited to Berger, Alvin Henry.
Application Number | 20020172604 09/681659 |
Document ID | / |
Family ID | 24736212 |
Filed Date | 2002-11-21 |
United States Patent
Application |
20020172604 |
Kind Code |
A1 |
Berger, Alvin Henry |
November 21, 2002 |
VARIABLE PRESSURE OIL PUMP
Abstract
A variable pressure oil pump assembly for use with a vehicle
having a controller includes a pump body having an inlet, an
outlet, a valve chamber, a first passage disposed between the inlet
and the valve chamber, and a second passage disposed between the
outlet and the valve chamber. The assembly further includes a
pressure relief valve subassembly having a movable plunger that is
disposed at least partially in the valve chamber for controlling
flow of oil through the valve chamber so as to control outlet oil
pressure at the outlet. A plunger adjustment mechanism is
associated with the valve subassembly and adapted to communicate
with the controller. The plunger adjustment mechanism is operable
to control movement of the plunger based on control signals
provided by the controller.
Inventors: |
Berger, Alvin Henry;
(Brownstown, MI) |
Correspondence
Address: |
BROOKS & KUSHMAN P.C./FGTI
1000 TOWN CENTER
22ND FLOOR
SOUTHFIELD
MI
48075
US
|
Family ID: |
24736212 |
Appl. No.: |
09/681659 |
Filed: |
May 17, 2001 |
Current U.S.
Class: |
417/307 |
Current CPC
Class: |
F04B 2205/11 20130101;
F04B 49/035 20130101; F04B 53/18 20130101; F01M 2001/0207 20130101;
Y10T 137/7876 20150401; F01M 1/16 20130101; F04B 2205/05
20130101 |
Class at
Publication: |
417/307 |
International
Class: |
F04B 049/00 |
Claims
1. A variable pressure oil pump assembly for use with a vehicle
having a controller, the assembly comprising: a pump body having an
inlet, an outlet, a valve chamber, a first passage disposed between
the inlet and the valve chamber, and a second passage disposed
between the outlet and the valve chamber; a pressure relief valve
subassembly including a movable plunger that is disposed at least
partially in the valve chamber for controlling flow of oil through
the valve chamber so as to control outlet oil pressure at the
outlet; and a plunger adjustment mechanism associated with the
valve subassembly and adapted to communicate with the controller,
the plunger adjustment mechanism being operable to control movement
of the plunger based on control signals provided by the
controller.
2. The assembly of claim 1 wherein the plunger adjustment mechanism
includes a solenoid subassembly connected to the pump body and
adapted to be electrically connected to the controller.
3. The assembly of claim 2 wherein the plunger is movable between a
seated position for inhibiting flow of oil through the valve
chamber and an open position for allowing oil to flow through the
valve chamber, and wherein when the solenoid subassembly is
energized, the solenoid subassembly draws the plunger toward the
open position.
4. The assembly of claim 1 wherein the plunger has an enlarged head
having first and second sides, and the plunger adjustment mechanism
includes a housing connected to the pump body and defining a
housing chamber that receives the enlarged head, the housing
including first and second apertures, the first aperture being in
fluid communication with the first side of the enlarged head, the
second aperture being in fluid communication with the second side
of the enlarged head and further being connected to the inlet, the
plunger adjustment mechanism further including a solenoid valve
adapted to be electrically connected to the controller and further
connected to the first aperture, the inlet and the outlet, wherein
when the solenoid valve is energized, the first aperture is exposed
to the outlet oil pressure, and when the solenoid valve is
de-energized, the first aperture is exposed to inlet oil
pressure.
5. The assembly of claim 1 wherein the plunger has an enlarged head
having first and second sides, and the plunger adjustment mechanism
includes a housing connected to the pump body and defining a
housing chamber that receives the enlarged head, the housing
including first and second apertures, the first aperture being in
fluid communication with the first side of the enlarged head, the
second aperture being in fluid communication with the second side
of the enlarged head and further being connected to the inlet so as
to expose the second side of the enlarged head to inlet oil
pressure, the plunger adjustment mechanism further including an
additional pump connected between the first aperture and the inlet
and adapted to be electrically connected to the controller, wherein
when the additional pump is not activated, the additional pump
provides the inlet oil pressure to the first aperture, and when the
additional pump is activated, the additional pump provides oil
pressure to the first aperture that is greater than the inlet oil
pressure.
6. A variable pressure oil pump assembly for use with a vehicle
having a controller, the assembly comprising: a pump body having an
inlet, an outlet, a first passage arrangement in fluid
communication with the inlet, a second passage arrangement in fluid
communication with the outlet, and a valve chamber disposed between
the passage arrangements; a pressure relief valve subassembly
including a movable plunger that is disposed at least partially in
the valve chamber for controlling flow of oil through the valve
chamber so as to control outlet oil pressure at the outlet; and a
plunger adjustment mechanism associated with the valve subassembly
and adapted to communicate with the controller, the plunger
adjustment mechanism being operable to control movement of the
plunger based on control signals provided by the controller.
7. A lubrication system for supplying oil to an engine, the system
comprising: an oil pump assembly including a pump body having an
inlet, an outlet, a first passage arrangement in fluid
communication with the inlet, a second passage arrangement in fluid
communication with the outlet, and a valve chamber disposed between
the passage arrangements, the oil pump assembly further including a
pressure relief valve subassembly having a movable plunger that is
disposed at least partially in the valve chamber for controlling
flow of oil through the valve chamber so as to control outlet oil
pressure at the outlet, and a plunger adjustment mechanism
associated with the valve subassembly for controlling movement of
the plunger; and an electronic controller electrically connected to
the plunger adjustment mechanism for controlling operation of the
plunger adjustment mechanism.
8. The system of claim 7 wherein the plunger adjustment mechanism
includes a solenoid subassembly connected to the pump body and
electrically connected to the controller.
9. The system of claim 8 wherein the plunger is movable between a
seated position for inhibiting flow of oil through the valve
chamber and an open position for allowing oil to flow through the
valve chamber, and wherein when the solenoid subassembly is
energized, the solenoid subassembly draws the plunger toward the
open position.
10. The system of claim 7 wherein the plunger has an enlarged head
having first and second sides, and the plunger adjustment mechanism
includes a housing connected to the pump body and defining a
housing chamber that receives the enlarged head, the housing
including first and second apertures, the first aperture being in
fluid communication with the first side of the enlarged head, the
second aperture being in fluid communication with the second side
of the enlarged head and further being connected to the inlet, the
plunger adjustment mechanism further including a solenoid valve
electrically connected to the controller and further connected to
the first aperture, the inlet and the outlet, wherein when the
solenoid valve is energized, the first aperture is exposed to the
outlet oil pressure, and when the solenoid valve is de-energized,
the first aperture is exposed to inlet oil pressure.
11. The system of claim 7 wherein the plunger has an enlarged head
having first and second sides, and the plunger adjustment mechanism
includes a housing connected to the pump body and defining a
housing chamber that receives the enlarged head, the housing
including first and second apertures, the first aperture being in
fluid communication with the first side of the enlarged head, the
second aperture being in fluid communication with the second side
of the enlarged head and further being connected to the inlet so as
to expose the second side of the enlarged head to inlet oil
pressure, the plunger adjustment mechanism further including an
additional pump connected between the first aperture and the inlet
and electrically connected to the controller, wherein when the
additional pump is not activated, the additional pump provides the
inlet oil pressure to the first aperture, and when the additional
pump is activated, the additional pump provides oil pressure to the
first aperture that is greater than the inlet oil pressure.
Description
BACKGROUND OF INVENTION
[0001] The invention relates to a variable pressure oil pump for
use with an engine, such as an internal combustion engine of a
motor vehicle.
[0002] A typical motor vehicle includes an internal combustion
engine and a lubrication system for providing oil to various
lubrication locations of the engine. Such lubrication locations
include sleeve bearings that support a rotating shaft, such as a
camshaft. The oil produces a viscous friction drag on the rotating
shaft, and the frictional drag converts mechanical energy from the
shaft into heat energy within the oil. To prevent the oil from
overheating within the bearings, the bearings are continually
provided pressurized, lower temperature oil from an oil pump of the
lubrication system. The pressurized, lower temperature oil is
forced into the bearings and displaces heated oil out of the
bearings.
[0003] When the engine is cold, such as during a cold start,
however, the oil in the bearings is cold and the viscosity of the
oil is high. As a result, it is not desirable to replace this oil
with pressurized, low temperature oil.
[0004] Systems have been developed to vary oil pressure of oil
provided to bearings of an internal combustion engine. U.S. Pat.
No. 5,339,776, for example, discloses a lubrication system that
includes an oil pump that draws oil from an oil sump, and a bypass
valve that is capable of diverting oil supplied by the oil pump
back into the oil sump without routing the oil to the bearings.
Because high pressure oil is dumped back into the sump, however,
aeration of the oil may occur. Furthermore, the oil dumped back
into the sump will likely experience significant heat loss.
SUMMARY OF INVENTION
[0005] The present invention addresses the shortcomings of the
prior art by providing a variable pressure oil pump assembly that
can vary outlet oil pressure based on one or more operating
conditions. Furthermore, outlet oil pressure may be varied without
diverting high pressure oil into an oil sump.
[0006] Under the invention, a variable pressure oil pump assembly
for use with a vehicle having a controller includes a pump body
having an inlet, an outlet, a valve chamber, a first passage
disposed between the inlet and the valve chamber, and a second
passage disposed between the outlet and the valve chamber. The
assembly further includes a pressure relief valve subassembly
having a movable plunger that is disposed at least partially in the
valve chamber for controlling flow of oil through the valve chamber
so as to control outlet oil pressure at the outlet. A plunger
adjustment mechanism is associated with the valve subassembly and
adapted to communicate with the controller. The plunger adjustment
mechanism is operable to control movement of the plunger based on
control signals provided by the controller.
[0007] The plunger adjustment mechanism may be any suitable
mechanism that is configured to affect movement of the plunger. For
example, the plunger adjustment mechanism may include a solenoid
subassembly connected to the pump body and adapted to be
electrically connected to the controller. With such a
configuration, when the solenoid subassembly is energized, the
solenoid subassembly draws the plunger toward an open position for
allowing oil to flow through the valve chamber.
[0008] In another embodiment of the invention, the plunger has an
enlarged head having first and second sides, and the plunger
adjustment mechanism includes a housing connected to the pump body
and defining a housing chamber that receives the enlarged head.
Furthermore, the housing including first and second apertures. The
first aperture is in fluid communication with the first side of the
enlarged head. The second aperture is in fluid communication with
the second side of the enlarged head and is further connected to
the inlet. In addition, the plunger adjustment mechanism includes a
solenoid valve adapted to be electrically connected to the
controller and further connected to the first aperture, the inlet
and the outlet. When the solenoid valve is energized, the first
aperture is exposed to the outlet oil pressure. When the solenoid
valve is de-energized, the first aperture is exposed to inlet oil
pressure.
[0009] In yet another embodiment of the invention, the plunger has
an enlarged head having first and second sides, and the plunger
adjustment mechanism includes a housing connected to the pump body
and defining a housing chamber that receives the enlarged head.
Furthermore, the housing includes first and second apertures. The
first aperture is in fluid communication with the first side of the
enlarged head. The second aperture is in fluid communication with
the second side of the enlarged head and is further connected to
the inlet so as to expose the second side of the enlarged head to
inlet oil pressure. In addition, the plunger adjustment mechanism
includes an additional pump connected between the first aperture
and the inlet and adapted to be electrically connected to the
controller. When the additional pump is not activated, the
additional pump provides the inlet oil pressure to the first
aperture. When the additional pump is activated, the additional
pump provides oil pressure to the first aperture that is greater
than the inlet oil pressure.
[0010] These and other objects, features, and advantages of the
present invention are readily apparent from the following detailed
description of the preferred embodiments when taken in connection
with the accompanying drawings.
BRIEF DESCRIPTION OF DRAWINGS
[0011] FIG. 1 is a schematic diagram of an engine that incorporates
a lubrication system according to the invention, wherein the
lubrication system includes an oil pump assembly that provides
pressurized oil to lubrication locations of the engine;
[0012] FIG. 2 is a enlarged fragmentary view of the oil pump
assembly showing a plunger of the oil pump assembly in a seated
position;
[0013] FIG. 3 is a enlarged fragmentary view of the oil pump
assembly showing the plunger in an open position;
[0014] FIG. 4 is a schematic view of a second embodiment of the oil
pump assembly showing a plunger of the oil pump assembly in a
seated position;
[0015] FIG. 5 is a schematic view of the second embodiment of the
oil pump assembly showing the plunger in an open position;
[0016] FIG. 6 is a schematic view of a third embodiment of the oil
pump assembly showing a plunger of the oil pump assembly in a
seated position; and
[0017] FIG. 7 is a schematic view of the third embodiment of the
oil pump assembly showing the plunger in an open position.
DETAILED DESCRIPTION
[0018] FIG. 1 shows an automotive internal combustion engine 10
that incorporates a lubrication system 12 according to the
invention. The lubrication system 12 includes an oil sump or pan 14
and a suction pipe 16 that routes oil from the oil pan 14 to an oil
pump assembly 18. The oil pump assembly 18 provides pressurized oil
to a discharge pipe 19, which leads to an oil filter 20. An oil
passage such as a main gallery 22 leads from the filter 20 to a
crankshaft 24 and a camshaft 26 of the engine 10. Internal passages
(not shown) through the crankshaft 24 provide oil to crankshaft
bearings 27 and connecting rod bearings 28. Similarly, internal
passages (not shown) through the camshaft 26 provide oil to
camshaft bearings 30. Gravity drains 32 return the oil to the oil
pan 14. The lubrication system 1 2 also includes an electronic
controller, such as electronic control unit 34, that is connected
to the oil pump assembly 18.
[0019] Referring to FIGS. 1 through 3, the oil pump assembly 18
includes a pump body 36 and a pump element 38 disposed in the pump
body 36 for pressurizing the oil. The pump body 36 has an inlet 40
connected to the suction pipe 16, and an outlet 42 connected to the
discharge pipe 19. The pump body 36 further includes a valve
chamber 44, a first or low pressure passage arrangement 46 in fluid
communication with the valve chamber 44, and a second or high
pressure passage arrangement 48. The first passage arrangement 46
includes a first passage 50 disposed between the inlet 40 and the
valve chamber 44, and an inlet passage 51 extending between the
inlet 40 and the pump element 38. The second passage arrangement 48
includes a second passage 52 extending between the outlet 42 and
the valve chamber 44, and an outlet passage 53 extending between
the pump element 38 and the outlet 42. In addition, the pump body
36 includes a connector passage 54 extending between the valve
chamber 44 and the first passage 50.
[0020] The oil pump assembly 18 further includes a relief valve
subassembly 55 and a plunger adjustment mechanism 56 associated
with the valve subassembly 55. The valve subassembly 55 includes a
piston or plunger 58 that is disposed at least partially in the
valve chamber 44. The plunger 58 is movable between a seated
position, shown in FIG. 2, and an open position shown in FIG. 3.
The plunger 58 includes a plunger body 59 and a head 60 connected
to the plunger body 59. A passage (not shown) may also be provided
through the head 60 to allow oil and/or air that is displaced by
head 60 to flow from one side of the head 60 to the other side of
the head 60. While the plunger 58 may comprise any suitable
material, in the embodiment shown in FIG. 2 and 3, the plunger body
59 comprises steel, and the head 60 comprises iron.
[0021] The valve subassembly 55 also includes a spring 61 that
biases the plunger 58 toward the seated position. The plunger 58 is
movable against the bias of the spring 61 when a sufficient
pressure differential exists between the second passage 52 and the
first passage 50. Furthermore, the plunger 58 is movable against
the bias of the spring 61 when the plunger adjustment mechanism 56
is activated as described below in detail.
[0022] In the embodiment shown in FIGS. 1 through 3, the plunger
adjustment mechanism 56 is a solenoid subassembly that includes a
housing 62 and a solenoid winding 63 attached to the housing 62.
Furthermore, the solenoid winding 63 is electrically connected to
the electronic control unit 34. When the solenoid winding 63 is
de-energized, the plunger 58 moves between the seated position and
the open position based on the pressure differential existing
between the first and second passages 50 and 52, respectively. When
the solenoid winding 63 is energized, the head 60 of the plunger 58
is drawn toward the solenoid winding 63, thereby causing the
plunger 58 to move toward the open position shown in FIG. 3. Thus,
plunger adjustment mechanism 56 may provide a force that acts on
plunger 58, in addition to the force created by the pressure
differential between the passages 50 and 52, to move the plunger 58
against the bias of the spring 61 toward the open position.
Alternatively, the plunger adjustment mechanism 56 may be any
suitable mechanism that is configured to affect movement of the
plunger 58.
[0023] Referring to FIG. 1, the electronic control unit 34 is in
communication with a plurality of sensors, such as oil pressure
sensor 64, oil temperature sensors 66 and 67, engine load sensor
68, engine speed sensor 70, coolant temperature sensor 72, and oil
viscosity sensor 73. Based on input received from the sensors
64-73, the electronic control unit 34 generates appropriate control
signals for controlling operation of the plunger adjustment
mechanism 56.
[0024] Electronic control unit 34 may be provided as part of oil
pump assembly 18. For example, electronic control unit 34 may be
mounted on or proximate to pump body 36. Alternatively, electronic
control unit 34 may be provided as a separate component from oil
pump assembly 18. For example, electronic control unit 34 may be an
engine controller that is mounted on or proximate to engine block
74 of engine 10. With such a configuration, electronic control unit
34 may be used to control other components of engine 10, such as a
fuel supply system (not shown) and/or a coolant system (not
shown).
[0025] Referring to FIGS. 1 through 3, operation of engine 10
having lubrication system 12 will now be described in detail. It is
understood that bearings 27, 28 and 30 are typically designed to
have a leakage rate that will allow an adequate amount of oil to
flow through the bearings 27, 28 and 30 to maintain a non-damaging
temperature under the most severe operating conditions. Under
normal operating conditions, however, this flow of oil may cause
the bearings 27, 28 and 30 to operate at lower temperatures than
necessary. These lower temperatures may result in more fuel
consuming friction between the bearings 27, 28 and 30 and the oil.
Advantageously, the lubrication system 12 is able to adjust oil
pressure under such operating conditions, as well as other
operating conditions, so as to vary the amount of oil flowing
through the bearings 27, 28 and 30.
[0026] The electronic control unit 34 continually receives input
from the sensors 64-73 so as to monitor engine operating
conditions. Based on these operating conditions, the electronic
control unit 34 determines desired oil pressure for the lubrication
system 12. The electronic control unit 34 then generates
appropriate control signals for controlling operation of the
plunger adjustment mechanism 56 so as to regulate oil pressure.
[0027] For example, under low engine load conditions such as normal
operating conditions and/or startup conditions, the electronic
control unit 34 may energize the solenoid winding 63 so as to move
the plunger 58 toward the open position shown in FIG. 3. As a
result, high pressure oil will flow from the second passage 52 to
the first passage 50, thereby reducing outlet oil pressure at
outlet 42.
[0028] As another example, as engine loads increase above a
predetermined level, the electronic control unit 34 may de-energize
solenoid winding 63. Consequently, the plunger 58 will move between
the seated and open positions based on the pressure differential
between the passages 50 and 52 only.
[0029] The electronic control unit 34 may also generate appropriate
control signals to achieve a desired duty cycle for the solenoid
winding 63. Moreover, the clearance between the head 60 and the
housing 62 may be appropriately designed to achieve a damping
effect as the plunger 58 moves between the seated and open
positions. With such a configuration, the plunger 58 may maintain
an intermediate position between the seated and open positions, or
intermediate range of positions between the seated and open
positions, for a particular duty cycle. Furthermore, by varying the
duty cycle, the intermediate position or intermediate range of
positions of the plunger 58 may be varied so as to provide desired
oil pressure to the bearings 27, 28 and 30.
[0030] For example, at periodic intervals, measurements may be
taken with the various sensors 64-73, and the electronic control
unit 34 may calculate an inferred oil film thickness within the
bearings 27, 28 and 30 based on the measurements. If the inferred
oil film thickness is too low or too high for the particular engine
speed and/or engine load, then the duty cycle for the solenoid
winding 63 may be adjusted so as to increase or decrease oil
pressure provided to the bearings 27, 28 and 30.
[0031] As oil passes through the oil pump assembly 18, the pump
element 38 consumes mechanical energy so as to increase pressure of
the oil. For example, the pump element 38 may be driven either
directly or indirectly by the crankshaft 24, or by other suitable
means. Part of the mechanical energy is converted to thermal energy
within the oil due to such factors as friction and shearing of the
oil. The rest of the mechanical energy is converted into hydraulic
energy (oil pressure increase times the volume of oil pumped). When
the pressure of the oil eventually drops, such as within the
bearings 27, 28 and 30 or across the relief valve subassembly 55,
this hydraulic energy is converted into thermal energy. Thus,
virtually all of the mechanical energy consumed by the pump element
38 is converted into thermal energy within the oil.
[0032] When the relief valve subassembly 55 allows high pressure,
high temperature oil to be passed directly from second passage 52
to first passage 50, the temperature of the oil on the inlet side
of pump element 38 is increased. Consequently oil entering the pump
element 38 has reduced viscosity, which results in improved
efficiency of the oil pump assembly 18. Moreover, the temperature
of oil exiting the oil pump assembly 18 is increased, and, as a
result, viscous friction within the bearings 27, 28 and 30 is
reduced.
[0033] The lubrication system 12 also provides several other
advantages. First, because high pressure oil is not returned to the
oil pan 14, potential aeration of the oil in the oil pan 14 is
inhibited. Second, if the plunger mechanism 56 fails for any
reason, the plunger 58 can still move between the seated and open
positions based on the pressure differential between the passages
50 and 52.
[0034] FIGS. 4 and 5 show a second embodiment 110 of the oil pump
assembly. The oil pump assembly 110 includes a pump body 112, a
pressure relief valve subassembly 114 and a plunger adjustment
mechanism 116. The pump body 112 is similar to the pump body 36 of
the oil pump assembly 10. Consequently, similar elements common to
both the pump body 112 and the pump body 36 have been given the
same reference numerals. The pump body 112, however, may be
provided without connector passage 54 of pump body 36.
[0035] The valve subassembly 114 is similar to the valve
subassembly 55, and includes a plunger 118 and spring 61. The
plunger 118 has a plunger body 121 and an enlarged portion, such as
head 122, having a first side 124 and a second side 126. The
plunger 118 is movable between a seated position shown in FIG. 4,
and an open position shown in FIG. 5.
[0036] The plunger adjustment mechanism 116 includes a housing 128
that is connected to the pump body 112 and defines a housing
chamber 130 for receiving the head 122. Preferably, the housing 128
forms a seal with the outer perimeter of the enlarged head 122. The
housing 128 further includes first and second apertures 132 and
134, respectively. The first aperture 132 is in fluid communication
with the first side 124 of the enlarged head 122, and the second
aperture 134 is in fluid communication with the second side 126 of
the enlarged head 122. The second aperture 134 is also connected to
inlet 40 of pump body 112.
[0037] The plunger adjustment mechanism 116 also includes a
suitable valve, such as solenoid valve 136, that is mounted on the
pump body 112 and is connected to electronic control unit 34.
Alternatively, the solenoid valve 136 may be spaced away from the
pump body 112.
[0038] The solenoid valve 136 has first and second inlet ports 138
and 140, respectively, and an outlet port 142. The first inlet port
138 is connected to inlet 40 of pump body 112, the second inlet
port 140 is connected to the outlet 42 of pump body 112, and the
outlet port 142 is connected to the first aperture 132. When the
solenoid valve 136 is de-energized, both sides 124 and 126 of the
enlarged head 122 are exposed to the same pressure. As a result,
the plunger adjustment mechanism 116 exerts no net force on the
plunger 118, and the plunger 118 moves between the seated and open
positions based on the pressure differential between the passages
50 and 52. When the solenoid valve 136 is energized by electronic
control unit 34, outlet oil pressure is provided to the first
aperture 132, thereby urging the plunger 118 toward the open
position shown in FIG. 5. Thus, plunger adjustment mechanism 116
may provide a force that acts on plunger 118, in addition to the
force created by the pressure differential between the passages 50
and 52, to move the plunger 118 against the bias of the spring 61
toward the open position. Furthermore, duty cycle of the solenoid
valve 136 may be adjusted, in a similar manner as described above,
so as to achieve a desired intermediate position between the seated
and open positions, or intermediate range of positions between the
seated and open positions, for the plunger 118.
[0039] FIGS. 6 and 7 show a third embodiment 210 of the oil pump
assembly. The oil pump assembly 210 includes pump body 112 and
relief valve subassembly 114 of the oil pump assembly 110, and
further includes a plunger adjustment mechanism 212. The plunger
adjustment mechanism 212 is similar to the plunger adjustment
mechanism 116, and includes housing 128. The plunger adjustment
mechanism 212 further includes an additional pump 214 having an
inlet 216 connected to inlet 40 of pump body 112, and an outlet 218
connected to first aperture 132 of the housing 128. The additional
pump 214 is also connected to electronic control unit 34.
Furthermore, the additional pump 214 may be mounted on the pump
body 112, as shown in FIG. 6, or the additional pump 214 may be
spaced away from the pump body 112.
[0040] When the additional pump 214 is not activated, inlet oil
pressure is provided to the first aperture 132. With such an
arrangement, plunger 118 moves between a seated position, shown in
FIG. 6, and an open position, shown in FIG. 7, based on the
pressure differential between passages 50 and 52. When the
additional pump 214 is activated by electronic control unit 34, the
additional pump 214 provides oil pressure to the first aperture 132
that is higher than inlet oil pressure. As a result, the piston 118
is urged toward the open position shown in FIG. 7. Thus, plunger
adjustment mechanism 212 may provide a force that acts on plunger
118, in addition to the force created by the pressure differential
between the passages 50 and 52, to move the plunger 118 against the
bias of the spring 61 toward the open position. Furthermore, duty
cycle of the additional pump 214 may be adjusted, in a similar
manner as described above, so as to achieve a desired intermediate
position between the seated and open positions, or intermediate
range of positions between the seated and open positions, for the
plunger 118.
[0041] In each of the above embodiments, the electronic control
unit 34 provides necessary power for controlling operation of the
plunger adjustment mechanism 56, 116 or 212. Alternatively, an
additional power source (not shown) may be connected to the plunger
adjustment mechanism 56, 116, or 212, such as between the
electronic control unit 34 and the plunger adjustment mechanism 56,
116 or 212.
[0042] While the best mode for carrying out the invention has been
described in detail, those familiar with the art to which this
invention relates will recognize various alternative designs and
embodiments for practicing the invention as defined by the
following claims.
* * * * *