U.S. patent application number 11/252101 was filed with the patent office on 2007-04-19 for fluid pump and method.
Invention is credited to Steven T. Omachi.
Application Number | 20070084431 11/252101 |
Document ID | / |
Family ID | 37947005 |
Filed Date | 2007-04-19 |
United States Patent
Application |
20070084431 |
Kind Code |
A1 |
Omachi; Steven T. |
April 19, 2007 |
Fluid pump and method
Abstract
An internal combustion engine (200) includes a fluid pump (220)
having an inlet (218), a low pressure outlet (223), and a high
pressure outlet (222). A reservoir (226) is connected to the high
pressure outlet (222) and an oil sump (204) is in fluid
communication with the inlet (218). A pressure regulating valve
(228) connects the high pressure outlet (222) and the low pressure
outlet (223). A recirculation passage (227) fluidly connects the
low pressure outlet (223) with the inlet (218). A flow of oil at a
high pressure in the high pressure outlet (222) passes through the
regulating valve (228) and enters the inlet (218) when the fluid
pump (220) is in operation.
Inventors: |
Omachi; Steven T.; (Skokie,
IL) |
Correspondence
Address: |
INTERNATIONAL ENGINE INTELLECTUAL PROPERTY COMPANY
4201 WINFIELD ROAD
P.O. BOX 1488
WARRENVILLE
IL
60555
US
|
Family ID: |
37947005 |
Appl. No.: |
11/252101 |
Filed: |
October 17, 2005 |
Current U.S.
Class: |
123/196R |
Current CPC
Class: |
F01M 1/02 20130101; F01M
1/16 20130101; F01M 2001/123 20130101; F01M 9/04 20130101; F02M
57/025 20130101 |
Class at
Publication: |
123/196.00R |
International
Class: |
F01M 1/02 20060101
F01M001/02 |
Claims
1. An internal combustion engine, comprising: a fluid pump having a
pump inlet, a low pressure pump outlet, and a high pressure pump
outlet; a reservoir connected to the high pressure pump outlet; an
oil sump in fluid communication with the pump inlet; a pressure
regulating valve disposed between the high pressure pump outlet and
the low pressure pump outlet; a recirculation passage fluidly
connecting the low pressure pump outlet and the pump inlet; wherein
a flow of high pressure oil in the high pressure outlet bypasses
through the regulating valve and enters the pump inlet when the
pump is in operation.
2. The internal combustion engine of claim 1 further comprising a
first check valve disposed in the recirculation passage.
3. The internal combustion engine of claim 1, further comprising a
vent passage that includes a valve, wherein the vent passage
fluidly connects the recirculation passage with the oil sump.
4. The internal combustion engine of claim 3, further comprising an
additional vent passage that includes a pressure relief valve,
wherein the additional vent passage fluidly connects the
recirculation passage with the oil sump.
5. The internal combustion engine of claim 1, further comprising an
oil cooler disposed in the recirculation passage.
6. The internal combustion engine of claim 1, further comprising:
an oil temperature sensor disposed in the recirculation passage; an
electronic engine controller connected to the recirculation
passage; and an electronic valve connected to the electronic engine
controller; wherein the electronic valve fluidly connects the
recirculation passage with the oil sump when a temperature of oil
in the recirculation passage exceeds a predetermined value.
7. The internal combustion engine of claim 1, further comprising a
third check valve disposed in fluid communication with the pump
inlet to prevent backflow from the pump inlet to an oil
distribution circuit.
8. The internal combustion engine of claim 1, further comprising a
low pressure pump disposed in series between the fluid pump and the
oil sump.
9. The internal combustion engine of claim 1, further comprising a
core engine structure, wherein the core engine structure is
arranged and constructed to provide power that drives the fluid
pump.
10. A fluid pump, comprising: a pump housing; an injection pressure
regulator (IPR) valve disposed on the housing; a fluid inlet, a
high pressure outlet, and a low pressure outlet, formed in the pump
housing; a first check valve integrated in the pump housing and in
fluid communication with the low pressure outlet; a second check
valve integrated in the pump housing and in fluid communication
with an outlet of the first check valve and the fluid inlet;
wherein when the first check valve is open, the fluid inlet
receives an oil flow from the low pressure outlet of the pump.
11. The fluid pump of claim 10, wherein the fluid pump is disposed
in a high pressure oil system of an internal combustion engine.
12. The fluid pump of claim 10, wherein at least one of the first
check valve and the second check valve includes a bore formed in
the housing of the pump.
13. The fluid pump of claim 12, wherein the bore includes a spring
and a valve element.
14. The fluid pump of claim 10, further comprising a crankshaft,
wherein the crankshaft rotates and is arranged to receive power
from at least one of a mechanical geared connection to a core
engine structure and an electric motor.
15. The fluid pump of claim 14, wherein the low pressure output of
the pump includes an annulus, and wherein the annulus is disposed
adjacent to an interface between the crankshaft and the housing of
the pump.
16. A method for a pumping oil in an internal combustion engine
comprising the steps of: ingesting an oil flow at a low pressure
into an inlet of a fluid pump; compressing the oil flow to a high
pressure; sending a first portion of the oil flow to a high
pressure reservoir; venting a second portion of the oil flow to a
low pressure outlet; recirculating the from the low pressure outlet
to the inlet of the fluid pump through a recirculation path; mixing
the second portion with the inlet oil flow.
17. The method of claim 16, further comprising the step of
selectively venting oil from the recirculation path into an oil
sump.
18. The method of claim 16, further comprising the step of cooling
the oil quantity in the recirculation path.
19. The method of claim 16, further comprising the steps of:
sensing a temperature of the oil quantity in the recirculation
path; and opening a vent valve to fluidly connect the recirculation
path with an oil sump when the temperature of the oil quantity
exceeds a predetermined value.
20. The method of claim 16, wherein the step of compressing is
accomplished by use of a power input to the fluid pump from the
internal combustion engine.
Description
FIELD OF THE INVENTION
[0001] This invention relates to internal combustion engines,
including but not limited to fluid pumps for internal combustion
engines.
BACKGROUND OF THE INVENTION
[0002] Many internal combustion engines use fluid pumps to pump
fluid for various engine systems, for example, fuel systems,
lubrication systems, and/or hydraulic systems. Many fluid systems
pump fluid from a low or an intermediate pressure to a high
pressure. A high pressure pump on an engine may be used to pump
hydraulic fluid, for example, oil or fuel, to a plurality of
injectors. The injectors either inject high pressure fuel, or use
high pressure oil to intensify the pressure of low pressure fuel
within the injectors. In either case, high pressure fuel is
injected into engine cylinders and is mixed with air, often air
containing recirculated exhaust gas to provide combustion, as is
known in the art. Combustion in a plurality of cylinders provides
power that rotates a crankshaft and drives the engine.
[0003] Mechanical power generated by the rotation of the crankshaft
of the engine is often used in many forms to drive other
components, or is converted to other types of power, for example
electrical or thermal, to drive other systems on the engine or a
vehicle. Power used to drive anything other than the main output
shaft of the engine is referred to as "parasitic" loss. Examples of
parasitic losses on engines include cooling fans, air compressors,
air conditioning compressors, alternators driving various
electrical components, fuel and/or oil pumps, and so forth.
[0004] A fluid pump on an engine may be driven mechanically from a
rotating component of the engine, or may be driven electrically by
current generated by an alternator or a generator. Depending on the
capacity of the pump, the power output of the engine may be reduced
by as much as 10% or more at high engine speeds and loads. Often,
the entire output capacity of the pump is not required at high
engine speeds, but the direct mechanical connection between the
pump and the rotating engine component may not allow for modulation
of the pump's power consumption resulting in wasted power from
driving the fluid pump. Wasted power takes away from the useful
power of the engine, and increases the parasitic losses of the
engine thus increasing fuel consumption and engine wear.
[0005] Some solutions have been proposed in the past for reducing
parasitic losses associated with engine driven pumps. Most systems
proposed include use of an electric pump that provides a capability
of variable pump power. Such systems rely on driving a pump with an
electric motor that receives electrical power from an alternator or
a generator driven mechanically by the engine. These electrical
pump systems achieve a desirable modulation of the power consumed
by the pump, but introduce additional inefficiencies at times when
the full output of the pump is required. For example, the addition
of an alternator in a pump driving circuit inherently reduces the
overall efficiency of the system because there are power losses
associated with conversion of mechanical to electrical power in the
alternator, and additionally, there are power losses in the
transmission of electrical power to the pump motor and the
conversion of electrical power back to mechanical power in the
motor.
[0006] Accordingly, there is a need for more efficient modulation
of power consumption in a fluid pump for an internal combustion
engine.
SUMMARY OF THE INVENTION
[0007] An internal combustion engine includes a fluid pump having
an inlet, a low pressure outlet, and a high pressure outlet. A
reservoir is connected to the high pressure outlet and an oil sump
is in fluid communication with the inlet. A pressure regulating
valve connects the high pressure outlet and the low pressure
outlet. A recirculation passage fluidly connects the low pressure
outlet and the inlet. A flow of oil at a high pressure in the high
pressure outlet passes through the regulating valve and enters the
inlet when the pump is in operation.
[0008] In one embodiment, the fluid pump includes a pump housing
having the regulating valve integrated thereon. An inlet, a high
pressure outlet, and a low pressure outlet, are formed in the pump
housing. A first check valve is integrated in the pump housing and
is in fluid communication with the low pressure outlet. A second
check valve is also integrated in the pump housing and is in fluid
communication with an outlet of the first check valve and the inlet
of the pump. When the first check valve is open, the inlet of the
pump receives an oil flow from the low pressure outlet of the
pump.
[0009] A method for use with a fluid pump includes the steps of
ingesting an oil flow at a low pressure into an inlet of the fluid
pump, compressing the oil flow to a high pressure, sending a first
portion of the oil flow to a high pressure reservoir, venting a
second portion of the oil flow to a low pressure outlet,
recirculating an oil quantity from the low pressure outlet to the
inlet of the fluid pump through a recirculation path, and mixing
the oil quantity with the oil flow.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a block diagram of a prior art fluid system for an
internal combustion engine.
[0011] FIG. 2 is a block diagram of a fluid system for an internal
combustion engine in accordance with the invention.
[0012] FIGS. 3 and 4 are different perspective views of a fluid
pump for use with an internal combustion engine.
[0013] FIG. 5 is a perspective view of the fluid pump with a
driving gear removed.
[0014] FIG. 6 is a partial cut-away view of the fluid pump of FIG.
3.
[0015] FIGS. 7A and 7B are detail cut-away views of a check valve
of the fluid pump of FIG. 3 shown in an open and a closed
positions.
[0016] FIG. 8 is a partial cut-away view of the fluid pump of FIG.
3.
[0017] FIG. 9 is a magnified detail cut-away view of the fluid pump
shown in FIG. 8.
[0018] FIG. 10 is the cut-away view showing flow of oil through a
portion of the fluid pump shown in FIG. 8.
[0019] FIG. 11 is a flowchart for a method of operating a fluid
pump in accordance with the invention.
DESCRIPTION OF A PREFERRED EMBODIMENT
[0020] A typical prior art configuration of an oil circuit for an
internal combustion engine is shown in FIG. 1. A core engine 100
includes a base engine structure 102. An oil sump 104 contains an
oil pool 106. A low pressure oil pump 108 has an oil inlet 110 that
collects oil from the oil pool 106 to supply the pump 108. The low
pressure pump 108 is driven by power from the base engine structure
102, as denoted by a solid bold arrow 112. Typical low pressure
pumps use a gerotor (not shown) as an impeller for the low pressure
pump 108.
[0021] A rotating crankshaft (not shown) of the base engine 102
drives the low pressure pump 108. A low pressure outlet 114 of the
pump 108 is connected to an oil distribution circuit 116. The oil
distribution circuit 116 is connected to the base engine 102 to
supply oil for lubrication of various moving components, for
example, crankshaft bearings, valve train components, and so forth.
The supply circuit 116 is also connected to an inlet 118 of a high
pressure oil pump 120.
[0022] The high pressure oil pump 120 receives oil from the outlet
114 of the low pressure pump 108, and pressurizes the oil and
supplies it to a high pressure outlet 122. Typical pressures at the
outlet 114 may be between 10 and 50 PSI (70 and 345 kPa), and
typical pressures at the outlet 122 may be around 4500 PSI (30 MPa)
or more. High pressure oil from the outlet 122 of the high pressure
pump 120 passes through a check valve 124 before collecting in a
high pressure oil rail or reservoir 126. A desired pressure in the
high pressure reservoir 126 is controlled by an injection pressure
regulator (IPR) valve 128 that fluidly connects the outlet 122 of
the pump 120 with a low pressure drain passage 130. The drain
passage 130 receives oil from the IPR valve 128, and drains it back
into the sump 104. This process is known as "shunting", wherein
high pressure oil at the outlet of the pump 120 is "shunted" to
control the pressure of oil in the reservoir 126.
[0023] The reservoir 126 is connected to a plurality of fuel
injectors 132 and supplies them with high pressure oil. The oil
from the reservoir 126 is used in each of the injectors 132 in
conjunction with an intensifier piston (not shown) to elevate the
pressure of fuel coming to the injectors through a fuel circuit 134
to a level appropriate for injection into combustion cylinders (not
shown) included in the base engine 102.
[0024] The high pressure pump 120 is typically gear driven and
receives power from the base engine 102, as denoted by a solid bold
arrow 136. Because of a direct mechanical connection between the
base engine 102 and the high pressure pump 120, a rotational speed
of the pump 120 is proportional to a rotational speed of the
crankshaft in the base engine 102. Power consumption of the pump
120 increases as a speed of the base engine 102 increases, and can
reach 10% or more of the total power output of the engine 100
during operation at high speeds. If the engine 100 is operating at
a low load output requirement condition, a fuel quantity consumed
by the engine 100 is relatively low, and hence, a high pressure oil
quantity used from the reservoir 126 may be far below the oil
output capacity of the pump 120. Under such a condition, a large
quantity of oil is discharged though the drain passage 130, but the
power consumption 136 of the pump 120 remains high. This problem
may be rectified in the following solution which describes an
apparatus for and method of reducing parasitic power consumption of
a fluid pump for an internal combustion engine.
[0025] A core engine 200 includes a base engine structure 202. An
oil sump 204 contains an oil pool 206. A low pressure oil pump 208
has an oil inlet 210 that collects oil from the oil pool 206 to
supply the pump 208. A low pressure outlet 214 of the pump 208 is
connected to an oil distribution circuit 216. The oil distribution
circuit 216 is connected to the base engine 202 and also connected
to an inlet 218 of a high pressure oil pump 220. A first check
valve 219 is positioned upstream of the inlet 218 to prevent return
flow from the high pressure pump circuit 218.
[0026] High pressure oil from an outlet 222 of the high pressure
pump 220 passes through a second check valve 224 including a bleed
orifice before collecting in a high pressure oil rail or reservoir
226. A desired pressure in the high pressure reservoir 226 is
controlled by an IPR valve 228. The IPR valve 228 fluidly connects
the outlet 222 with a low pressure outlet 223 and the inlet 218 of
the high pressure pump 220 through a recirculation passage 227. The
recirculation passage 227 includes a third check valve 229 to
prevent back flow to the drain passage. The recirculation passage
227 is in direct fluid communication with the inlet 218, and is
disposed downstream of the first check valve 219. Oil in the
recirculation passage 227 is at a low to moderate pressure after
venting from the IPR valve 228, and enters back into the pump 220
instead of draining into the sump 204 as previously described.
[0027] The high pressure pump 220 may be gear driven and receive
power from the base engine 202, as denoted by a solid bold arrow
236. Alternatively, the high pressure pump 220 may receive power
from an electric motor (not shown) or any other mode used in the
art of internal combustion engines to operate a pump for an engine.
In the embodiment of FIG. 2, a direct mechanical connection between
the base engine 202 and the high pressure pump 220 ensures that a
rotational speed of the pump 220 is proportional to a rotational
speed of the base engine 202. Power consumption of the pump 220 may
either not increase or may increase at a lower rate as compared to
the power consumption of a typical pump as the base engine speed
increases, because oil at the inlet 218 of the pump is at a higher
pressure as compared to the prior art, and the work required by the
pump to elevate its pressure is reduced.
[0028] Two main considerations may be addressed for the engine 200
during operation. First, recirculation of oil around the pump 220
through the passage 227 may elevate the temperature of the
recirculated oil due to repeated compression cycles. A temperature
sensor 238, connected to an engine controller 239 may be included
in the passage 227 and monitor the temperature of the oil. In the
case when the temperature of oil in passage 227 exceeds a
predetermined value during operation of the engine 200, for
instance, 240 deg F. (116 deg C.), the electronic controller may
command a vent valve 240 to vent oil back into the sump 204 through
a vent passage 242 that fluidly connects the recirculation passage
227 with the sump 204. Venting of oil in the passage 227 will allow
for a quantity of oil at a lower temperature from the low pressure
pump 208 to reach the inlet 218, replace the quantity of oil that
was vented through the valve 240, and mix with warmer oil in the
recirculation passage 227 thus lowering the overall temperature of
oil passing through the pump 220.
[0029] Alternatively, an oil cooler 244 may be placed in the
recirculation passage 227 and be used instead of or in conjunction
with the valve 240 to control the temperature of oil passing
through the pump 220.
[0030] Second, depending on a control scheme used to operate the
IPR valve 228, controllability issues creating instabilities and
pressure fluctuations in the recirculation passage 227 may arise.
These issues may be related to a feedback loop time and response
time of the IPR valve 228 and may be resolved by a placement of an
additional vent passage 245 that fluidly connects the IPR valve 228
with the sump 204 and contains a pressure relief valve 246. The
pressure relief valve 246 may open to relieve pressure spikes in
the recirculation passage 227 that may be created when the IPR
valve 228 first opens or at times of drastic change in the speed of
the engine 202. The pressure relief valve 246 may be selected to
have an opening pressure value that allows it to remain closed
during normal engine operation, and only open when a pressure spike
is present.
[0031] One example of a high pressure oil pump 300 for an internal
combustion engine is shown in FIGS. 3, 4, and 5. The pump 300 has a
housing 302 containing a plurality of pistons 304. A driving gear
306 is connected to a crankshaft 502 that drives the pistons 304 as
is known in the art. As shown in FIG. 4, an inlet 402 is formed in
a flange 404 that may also serve as a mounting flange for the pump
300. A high pressure outlet 406 allows oil at a high pressure to
exit the pump 300 during operation, and is connected to the housing
302. An IPR valve 408 is integrated with the pump housing 302.
[0032] A view of the pump 300 with the driving gear removed is
shown in FIG. 5. A low pressure outlet 504 of the pump 300 exists
in a space between the crankshaft 502 and an annular oil seal 506.
During operation, oil enters the pump 300 through the inlet 402. A
mechanical connection with the engine rotates the gear 305 and thus
compresses the oil in the pistons 304. High pressure oil exits the
pump 300 from the outlet 406. A quantity of oil may be shunted away
from the outlet 406 by the IPR valve 408, and exit the pump 300
through the low pressure outlet 506. Oil exiting the outlet 506
serves a secondary purpose of lubricating the crankshaft 502 of the
pump 300 during operation.
[0033] A partial section of the pump 300 is shown in FIG. 6. The
pump housing 302 is partially cut away to expose a portion of an
annular retainer 602, a bushing 604, the crankshaft 502, and a seal
606. The crankshaft 502 passes through the retainer 602, and the
bushing 604 is between the crankshaft 502 and the retainer 602. Low
pressure oil exiting from the outlet of the pump 300 passes through
an interface between the bushing 604, the retainer 602, and the
crankshaft 502, before collecting in an annulus 608 and exiting by
passing between the seal 606 and the crankshaft 502. The seal 606
may be made from an elastomeric material, and may be configured to
act as a check valve. Oil collecting in the annulus 608 may push a
portion of the seal 606 away from the location shown to create a
temporary opening during operation for oil to escape. The temporary
opening effectively acts as the low pressure outlet 604. A check
valve 702 may be integrated in the housing 302 of the pump 300.
[0034] A detail cut-away view of the check valve 702 in a closed
position is shown in FIG. 7A, and in an open position in FIG. 7B.
The check valve 702 has an inlet port 704, an outlet port 706, a
central bore 708, an inlet plug 710, a priming port 711, and a stop
plug 712. The central bore 708 fluidly connects the inlet port 704
with the outlet port 706. The central bore 708 includes a valve
element 714 and a tension spring 716. When the valve 702 is in a
closed position, the spring 716 is at its natural length and
retains the valve 714 in a location within the central bore 708
that blocks the outlet 706. Oil at a moderate pressure from the
priming port 711 fills a priming volume 713 and helps push the
valve element 714 away from the stop plug 710. The valve element
714 in this position is retained away from the stop plug 712.
[0035] The check valve 702 will open when fluid, in this case oil,
enters through the inlet port 704 and pressure in the priming port
713 is low. A flow of oil under pressure into the inlet port 704
will push the valve element 714 toward the stop plug 712 and away
from the outlet port 706. With the valve element 714 pushed against
the stop plug 706, the spring 716 is extended and the outlet port
706 is opened to allow the flow of oil.
[0036] In one embodiment, the valve 702 may serve the function of
the first check valve 219 shown in FIG. 2, and may be integrated
with the housing 302. The third check valve 229 may also be
configured similarly to the first check valve 219, and may be
integrated with the housing 302. The recirculation passage 227 may
also include cross-drilled passages and be integrated in the
housing 302.
[0037] A pump 800 having integrated check valves and a
recirculation passage is shown in partial cut-away in FIGS. 8 and
9. The pump 800 includes a housing 802, an annular retainer 804, a
bushing 806, and an annular seal 808. The seal 808 is between the
retainer 804 and a crankshaft 810. An annulus 812 is defined by the
housing 802, the retainer 804, the seal 808, and the crankshaft
810. The annulus 812 receives oil at a low or moderate pressure
from an IPR valve 814 (not shown) as described above. A first
passage 816 serves as an inlet to a first check valve 818, and
fluidly connects the annulus 812 with the first check valve 818.
The first check valve 818 is configured to open when oil enters the
check valve 818 from the annulus 812. The first check valve 818 may
be integrated with the housing 802, and may include a first tension
spring 820, a first valve element 822, and a first plug 824. The
first spring 820 is connected to the first valve element 822, and
the two are included in a first valve bore 826. The bore 826 may be
formed into the housing 802, and is in fluid communication with the
first passage 816. The first plug 824 seals the bore 826 from the
environment and limits the travel of the valve element 822 in the
bore 826 during operation of the valve 818.
[0038] A second passage 828 fluidly connects an outlet of the first
check valve 818 with an outlet 830 of a second check valve 832. The
second check valve 832 is configured to open when oil enters the
check valve 818 from a pump inlet 834. The second check valve 832
may be integrated with the housing 802, and may include a second
tension spring 836, a second valve element 838, and a second plug
840. The second spring 836 is connected to the second valve element
838, and the two are included in a second valve bore 842. The bore
842 may be formed into the housing 802, and is in fluid
communication with the second passage 828 and the pump inlet 834.
The second plug 840 limits the travel of the valve element 838 in
the bore 842 during operation of the valve 832.
[0039] During operation of the pump 800, oil may enter through the
pump inlet 834 as shown in FIG. 10. The flow of oil is denoted by
arrows. The oil may be pressurized and partly exit from a high
pressure outlet (not shown). A quantity of oil may be released into
the annulus 812. From the annulus 812 the oil may pass through and
open the first check valve 818 and enter the second passage 828. If
the second check valve 832 is closed, oil in the second passage 828
may recirculate into a compressor inlet 844. If additional oil is
entering the pump inlet 834, the second check valve 832 may be
open, and additional oil may enter the second passage 828 from the
outlet 830. Thus, oil entering the compressor inlet 844 may be a
mixture of recirculated oil from the passage 828 and oil coming
from the pump inlet 834.
[0040] A method for recirculation of fluid around a pump is
presented in FIG. 11. Oil at a low pressure enters a fluid pump in
step 1002. The pump compresses the oil to a high pressure at step
1004. A first portion of oil at a high pressure is sent to a
reservoir at step 1006. A second portion of oil at a high pressure
is vented to a low pressure and is recirculated back to an inlet of
the pump at step 1008. Oil that was recirculated in step 1008 may
be mixed with new oil at a low pressure, and be recompressed in
step 1010. The process may repeat as required during operation of
an internal combustion engine.
[0041] Additional steps may be advantageous to the operation of the
pump. First, oil in the recirculation path coming from the low
pressure outlet of the pump may be cooled, for example by use of an
oil cooler connected to the recirculation path, before going back
into the pump inlet. Second, the temperature of oil in the
recirculation path may be monitored and used to control a valve
that will vent oil back into the sump of the engine, as described
above.
[0042] Numerous advantages may be realized with the embodiments
described herein. First, power consumption of a high pressure fluid
pump may be reduced during periods of engine operation not
requiring the full output capability of the pump. These embodiments
may help reduce parasitic losses of power for an engine, thus
reducing power loss and increasing fuel economy. Impacts to
existing fluid systems using a pump may be minimal in that the
additional paths and valves needed for this invention are typically
small and inexpensive, and can even be integrated into existing
pumps.
[0043] The present invention may be embodied in other specific
forms without departing from its spirit or essential
characteristics. The described embodiments are to be considered in
all respects only as illustrative and not restrictive. The scope of
the invention is, therefore, indicated by the appended claims
rather than by the foregoing description. All changes that come
within the meaning and range of equivalency of the claims are to be
embraced within their scope.
* * * * *