Note: Descriptions are shown in the official language in which they were submitted.
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Title
Variable Displacement Sliding Vane Pump
Field of the Invention
The invention relates to a variable displacement
sliding vane. pump having a slide whose position is
controlled by a differential pressure, between a constant
pressure source and a variable pressure source, the
differential pressure equilibrating a spring force
applied to the slide to establish a desired flow rate and
pressure.
Background of the Invention
A lubrication system for an engine pressurizes and
distributes lubrication fluid to the engine lubrication
circuits. It employs a rotor and a slide with multiple
vanes and cavities which can vary the volume of fluid
delivered to the oil circuits.
The slide is eccentrically offset from the rotor to
create fluid chambers defined by the vanes, rotor, and
inner surface of the slide. A compression spring
positions the slide to create large fluid chambers as the
default. When the engine requires less volume of fluid or
less oil pressure by the pump, a pressure regulator
directs fluid from the pump output line to a regulating
chamber in the pump. Pressure in the regulating chamber
pivots the slide against the force of the spring to more
closely align the centers of the rotor and slide, thereby
reducing the size of the fluid chambers. This reduces the
amount of fluid drawn into the pump from the fluid
reservoir and likewise, the amount of fluid output by the
pump and thereby reduces the oil pressure as well.
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There are two ways to control pump output. The first
way is' to direct line pressure to the regulating chamber
via the pressure regulator to decrease pump output. The
second way is to remove pressure from the regulating
chamber via the pressure regulator by exhausting fluid to
increase pump output.
Representative of the art is U.S. patent no. 4342545
(1982) to Schuster discloses a variable displacement vane
type pump having a pivotally mounted ring member
control.lable to vary the eccentricity between the rotor
and the ring thus controlling the pump displacement. The
ring is positioned on the pivot such that the center
thereof is always located in one quadrant relative to
axes through the pivot.point and the center of th*e pump
rotor to continually maintain the net ring reaction
force, due to internal pressure, directed to one side of
the pivot connection in opposition to the displacement
control pressure, which is impressed on a portion of the
outer surface of the ring, whereby control stability
throughout the displacement range is improved.
What is needed is a variable displacement sliding
vane pump having a slide whose position is controlled by
a differential pressure between a constant pressure
source and a variable pressure source, the differential
pressure equilibrating a spring force applied to the
slide to establish a desired flow rate and pressure. The
present invention meets this need.
Summary of the Invention
The primary aspect of the invention is to provide a
variable displacement sliding vane pump having a slide
whose position is controlled by a differential pressure
between a constant pressure source and a variable
pressure source, the differential pressure equilibrating
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a spring force applied to the slide to establish a
desired flow rate and pressure.
Other aspects of the invention will be pointed out
or made obvious by the following description of the
invention and the accompanying drawings.
The invention comprises a variable displacement
sliding vane pump comprising a pump body, inlet and
outlet ports formed in said pump body, a drive shaft
rotatably mounted in said pump bo.dy, a rotor driven by
said drive shaft and co-axially aligried therewith, a
plurality of radially extending vanes slidably disposed
in said rotor, a pivot disposed in said pump body, a
slide pivotally disposed on said pivot in said pump body
and having a central axis eccentric to the axis of said
rotor, a plurality of fluid chambers defined by said
rotor, said vanes, and said slide that are successively
connected to said inlet and outlet ports, a spring acting
on said slide to urge said slide in one direction, a
first chamber and a second chamber, each suitable for
receiving a fluid pressure and each disposed.between said
pump body and an outer surface of said slide, the first
chamber in fluid communication with a pump outlet
discharge pressure, and a valve operable to selectively
pressurize and depressurize the second chamber.
Brief Description of the Drawings
The accompanying drawings, which are incorporated in
and form a part of the specification, illustrate
preferred embodiments. of the present invention, and
together with a description, serve to explain the
principles of the invention.
Fig. 1 is a front view of the pump with outer cover
removed.
Fig. 2 is an exploded view of the pump.
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Fig. 3 is a front view of the pump body without the
outer cover, slide, rotor and vanes.
Fig. 4 is a top/plan view of the pump rotor.
Fig. 5 is a plan view of the pump slide.
Fig. 6 is a schematic diagram of - the pump fluid
circuit.
Fig. 7 is a graph depicting the pump performance
including pump flow rate and press.ure.
Fig. 8 is a side view of an electric valve.
Fig. 9 is a graph depicting the pump performance
including pump flow rate and pressure.
Detailed Description of the Preferred Embodiment
Fig. 1 is a front view of the pump with outer cover
removed. The inventive pump 100 comprises body 10. Body
10 defines a cavity 11 within which is disposed slide 12
and rotor 13. A plurality of sliding vanes 14 are
radially disposed about rotor 13. ' Each vane 14 extends
radially from a slot 15 in rotor 13. Each vane 14 is
moveable within each slot 15.
Pump shaft 16 is rotatably mounted in body 10. A
splined end 160 of pump shaft 16 engages rotor 13. As
rotor 13 rotate.s vanes 14 are urged outwardly by a pair
of vane control rings 17 and centripetal force into a
sliding engagement with inner surface 120 of slide 12.
Slide 12 is pivotally engaged with the body at a
pivot member 18. Slide 12 pivots at pivot member 18
within cavity 11 thereby describing an arc which defines
the operating range of motion of.slide 12.
The position of each vane 14 is a function of the
position of slide 12 with respect to ring 17. Ring 17
occupies a space determined by the ends of vanes 14.
Ring 17 is substantially concentric with 'inner surface
120.
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The position of ring 17 with respect to rotor 13
determines the radial position of each vane 14 in each
slot 15, which in turn, determines a given slide 12
position as compared to the position of the axis of
rotation of rotor 13. This relationship determines the
volume of each of the chambers 21 between the inlet port
19 and the outlet port 20 for a given engine speed and
hence a given slide 12 position.
Body 12 defines a pair of kidney shaped ports 19, 20
which comprise an inlet port and an outlet port,
respectively, for the pump 100. A plurality of chambers
21 are formed by the vanes 14, rotor 13 and inner surface
120. Chambers 21 rotate with rotor 13 and expand and
contract during rotation, as is well-known in vane type
pumps.
Inlet port 19 accepts fluid from a source or
reservoir such as an engine oil system, not shown, and
passes the fluid to the chambers 21 in turn as rotor 13
rotates. Vanes 14 move the fluid in chambers 21 from the
inlet port 19 to the outlet port 20. As can be seen in
Fig. 1, if the pump rotor 13 is rotating in a
counterclockwise direction, chambers 21 are continually
expanding thereby creating a low pressure region which
causes an inflow of fluid in the area of inlet port 19
and are contracting thereby increasing fluid pressure
which causes an outflow of fluid in the area of the
outlet port 20.
The position of slide 12 is established by the
combined effect of the control pressure in each for two
chambers, namely, chamber 22 and chamber 23 acting in
balance with the spring force from spring 31. Chamber 22
extends about a portion of the outer circumference of
slide 12 from seal member 24 disposed in a groove 26 to
seal member 25 disposed in a groove 27, each formed in
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slide 12. Each seal member 24 and 25 is urged outwardly
against surface 28 by a resilient backing member 29, 30
respectively. Chamber 23 extends about a portion of the
outer circumference of slide 12 from seal member 24 to
pivot member 18.
Spring 31 acts in opposition to the sum of the fluid
pressures in chambers 22 and 23 such that as the total
pressure in chambers 22 and 23 increases, and therefore
the torque of the slide around the pivot member
increases, the pump slide 12 will move clockwise about
pivot member 18. The combined torque caused by the
pressure in chamber 22, 23 is balanced by the spring
force of spring 31.
The fluid pressure in chamber 22 is supplied by
fluid in ultimate communication with the outlet port 20
of pump 100 and is' therefore subject to the outlet
pressure of pump 100 or from a feedback channel to the
engine gallery, see Fig. 5. The fluid pressure in chamber
23 is supplied by fluid communication with a second
pressure source also connected to the outlet port 20 of
pump 100. The fluid pressure in chamber 22 is
proportional to the outlet pressure of pump 100. The
fluid pressure in chamber 23 is dependent upon the speed
of the pump 100, namely, for certain operating regimes
below a predetermined pump speed the pressure in chamber
23 is automatically vented to ambient, for example, an
oil storage reservoir. Above a' predetermined speed the
pressure in chamber 23 is equivalent to the pressure in
chamber 22. This is also referred to as the "switching
point" and can be set at any speed depending upon the
application. The sum of the pressures, and therefore
torque, in chambers 22 and 23 determine the position of
slide 12. The position of slide 12 determines the outlet
pressure and flow rate of the pump.
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Under most operating conditions, the axis of slide
12,, and therefore of inner surface 120, moves between
position 32 during low engine speed conditions to
position 33 during high engine speed conditions. As
vanes 14 are rotated from the inlet port 19 to outlet
port 20 a pressure transition takes place with the
chambers 21.
Since the inner surface 120 is subjected to the
internal pressure generation in chambers 21, slide 12 is
inherently unbalanced during operation. The net resultant
reaction force due to the internal pressure generation
passes through the central axis of inner surface 120. it
will be appreciated that the reaction forces always
provides a counterclockwise moment about axis 18 which is
in opposition to the clockwi.se moment generated by the
control pressure in chambers 22 and 23.
The pressures in chamber 22, 23 are balanced against
the force of spring 31 so that the displacement of the
pump, and as a result the flow, may be adjusted by
varying the chamber pressures. The inventive pump
controls both displacement and oil flow for two or more
outlet pressure levels based upon the pump outlet
pressure or the engine gallery pressure.
Typically the desirable pressure level in the pump
for each chamber is the pressure level required to
produce the proper oil flow and pressure for all engine
=speeds and load conditions. In some cases, at lower
rpm's the engine does not require a high oil pressure
level, therefore a somewhat lower pressure is acceptable,
and therefore the flow is reduced as well. The lower
operating pressure and flow is achieved by pressurizing
chamber 23.
The required magnitude of the lower oil pressure
depends upon different engine parameters, including
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whether, it is a gas or diesel engine, the engine
complexity, engine speed and load.
The inventive pump provides two levels of control.
The first is pressure control over a given speed range
due to the variable vane pump function. The second is
based upon'the ability of the pump to change between two
(or more) pressure levels by use of two (or more)
pressure chambers 22, 23, controlling the position of
slide 12.
A cover 70 is secured to the housing 10 by a
plurality of fasteners 37. Leakage from the chambers 21
radially outwardly past the cover 70 is prevented by
surface to surface contact.
Fig. 2 is an exploded view- of the pump. The
position of ring 17 with respect to rotor 13 determines
the radial position of each vane 14 in each slot 15,
which in turn, determines a slide 12 position as compared
to the position of the axis of rotation of rotor 13. An
inner edge 14a of each vane 14 bears upon the outer
20. surface 17a of ring 17. An outer edge 14b of each vane
14 also bears upon and slides upon inner surface 120 of
slide 12. The pump may use a single spring 31, or it may
use for example, two springs 31a and 31b.
Fig. 3 is a front view of the pump body without the
outer cover, slide, rotor and vanes. Inlet port 19 and
outlet port 20 are disposed in body 10. Conduit 34
transmits pressure from the main oil gallery 204 to
chamber 22, see Fig. S. Conduit 35 transmits pressure
from the main oil gallery 204 to chamber 23, see Fig. 5.
Conduit 34 is exposed to pump outlet pressure or engine
gallery oil pressure during all pump operating
conditions. The fluid pressure in conduit 35 is
determined by the position of valve 207, see Fig. 1.
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Fig. 4 is a top plan view of the pump rotor. Rotor
13 comprises slots 15 which are oriented radially about
the outer circumference. A vane 14 is slidingly engaged
in each slot 15. Drive shaft 16 engages rotor 13 through
splined hole 36. Drive shaft 16 may also be press fit in
hole 36. Each slot 15 comprises a radial length
sufficient to accommodate the entire range of movement of
each vane 14. During operation of the pump each vane 14
moves radially a predetermined distance which distance is
dependent upon the position of rings 17 with respect to
rotor 13.
Fig. 5 is a plan view of the pump slide. Slide 12
comprises inner surface 120. An outer edge of each vane
14 slidingly engages inner surface 120. Inner surface
120 is cylindrical, but the shape of the surface can be
slightly distorted to accommodate design geometries, for
example to an oval=or egg-shaped form. Pivot 18 engages
detent 121. Groove 26 and groove 27 each receive seal
members 24, 25 respectively, for sealing a fluid pressure
within each chamber 23, 22 respectively. Spring 31 bears
upon surface 122. Seal members 24, 25 may comprise any
material having a suitable compatibility with the pump
fluid, for example, synthetic and/or natural rubbers.
Fig. 6 is an example schematic diagram of the pump
fluid circuit 200. Fluid conduit 201 connects pump
outlet port 20 to an oil filter 202, oil cooler 203 and
to a main oil gallery 204. The main oil gallery 204 is
exposed to the outlet pressure of pump 100, subject to
friction losses normal to any fluid system. Main oil
gallery 204 is also connected to the engine oil system
210. This system is offered only as an example and does
not depict the varieties of engine oil systems to which
the inventive pump and system may be applied.
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Connected to the main oil gallery 204 is conduit 205
which connects to chamber 22=through cohduit 34, see Fig.
1. Connected to conduit 205 is conduit 209. Conduit 209
is connected to electric valve 207, see Fig. 7. Valve
207 is used to selectively connect or disconnect conduit
209 through conduit 206 to conduit 35 and chamber 23 in
Fig. 1, with the fluid pressure in conduit 205. Valve
207 is preferably contained within body 10. Valve'207 is
shown in Fig. 5 schematically separate from pump 100 for
ease of illustration. However, valve 207 may also be
separated from pump body 100 as schematically shown in
Fig. 5 in order to accommodate variable physical
constraints as required by system space requirements.
Valve 207 may also comprise a mechanical valve known in
15' the art, for example, a valve which regulates a
downstream pressure based upon an upstream pressure
commonly known as a pressure regulating valve.
The total force exerted against spring 31 by slide
12 is the sum of the torques created by the fluid
pressure in chamber 22 plus the fluid pressure in chamber
23, both acting about pivot member 18.
At or less than a first operating speed, valve 207
is OPEN thereby allowing the engine gallery pressure to
enter chamber 23. The pressure in chamber 23 and combined
with the pressure in chamber 22 causes slide 12 to pivot
about pivot member 18 an arcuate distance to a position
where the torque caused by the combined pressures i-n
chambers 22, 23 is balanced by the spring force of spring
31. The pump characteristics with slide 12 in this
position are shown by portion "A" of Fig. 7. The
pressure in chamber 22 and 23 is proportional to the pump
speed. As the engine speed, and thereby pump speed,
increase so does the pressure in the chambers 22, 23. In
this operating condition the pump output is a flow and
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pressure that is less than the flow and pressure of the
pump with the valve 207 closed (chamber 23 depressurized)
at the same engine speed. In portion "A" the position of
slide 12, and thereby of the pump output flow and
pressure, is a function of the pressure in both chambers
22, 23.
At an operating condition greater than the first
operating speed, valve 207 is closed thereby venting
chamber 23 to ambient pressure (approximately 1 bar).
The pressure in chamber 22 causes slide 12 to pivot about
pivot member 18 an arcuate distance to an equilibrium
position where the torque caused by the pressure in
chamber 22 is balanced by the spring force of spring 31.
Slide 12 pivots because as the pump speed increases, the
pressure in chamber 22 also increases, thereby increasing
the force exerted against spring 31. The pump
characteristics with.slide 12 in this position are shown
by portion B of Fig. 7. The operating regime in portion
B can also be characterized as a passive mode since
chamber 23 is vented to atmospheric pressure and the
entire pivot movement and position of slide 12 is=
determined by the level of pressurization of chamber 22.
In an alternate embodiment valve 207 may be opened
to a partial position thereby causing slide 12 to move to
a position that is intermediate position A and position
B, causing an intermediate outlet pressure and flow.
Placing valve 207 in any position between fully open and
fully closed allows the pressure in chamber 23 to b'e
variable, thereby providing a range of slide positions
for a given pump outlet pressure.
In the case of a failure of valve 207, the pump will
.continue to operate in a passive mode (chamber 23
depressurized) while meeting all oil requirements of the
engine. The passive opprating mode is still more
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efficient that a fixed displacement pump. With valve 207
in operation the instant invention provides incremental
horsepower reduction over the passive design.
Fig. 7 is an example graph depicting the pump
performance including=pump flow rate and pressure. A
range of engine speeds is represented on the x-axis and a
range of pump outlet pressures is represented on the y-
axis. A range of pump flow rates is also represented on
the second y-axis in liters per minute_
The engine speed range is from 0 RPM to 8000 RPM.
The outlet pressure range is from 0 bar to 6.00 bar. The
pump flow rate range is from 0 liters/minute to 90.00
liters/minute.
For the purposes of illustration an engine speed of
-3,500 RPM is selected to demonstrate the characteristics
of the inventive pump. The transition between operating
conditions- "A" and "B" is depicted as the "switching
point" in the center of the curves in the graph.
For engine speeds less than -3,500 RPM the maximum
pump outlet pressure is approximately 2.6 bar. The
maximum flow rate is approximately 20.0 liters/minute.
For engine speeds greater than -3,500 RPM the pump
outlet pressure quickly transitions up to a minimum
outlet pressure of approximately 4.9 bar at 7,500 RPM.
The flow rate transitions to a maximum of approximately
28.0 liters/minute at 7,500 RPM.
At the transition point the step change in pressure
is approximately 1.6 bar. The step change in flow is
approximately 5 1/min.
The performance transition is caused by slide 12
pivoting about pivot 18 caused by.deactivation of valve
207 venting chamber 23 to ambient atmospheric conditions.
Valve 207 is controlled by an electric signal transmitted
by an engine ECU, for example. Upon reaching the
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predetermined engine speed, in this case -3,500 RPM, ECU
208 (see Fig. 6) signals valve 207 to close, thereby
pressurizing chamber 23 with fluid pressure equal to that
in the main oil gallery 204.
As described previously, the pressures in chambers
22, 23 create a torque and hence force which is greater
than the combination of the force of the spring 31 and
,the fluid force in chambers 21, thereby causing spring 31
to compress. This causes slide 12 to pivot. By pivoting
in the clockwise direction the flow rate and outlet
pressure are each substantially decreased at the
predetermined engine speed because pump displacement is
reduced.
For the purposes of comparison, the dashed lines in
portion A of Fig. 7 below -3,500 RPM depict the behavior
of the outlet pressure and flow rate of a pump in the
case where the position of slide 12 is only controlled by
a single pressure chamber. In the single chamber case,
at relatively low engine speeds, say only slightly
greater than idle (-1,500 RPM), the pump would operate at
a comparatively el.evated outlet pressure and flow rate
not otherwise required by the engine. This is
inefficient. The inventive pump provides only the
required amount of flow and pressure for efficient
operation at reduced engine speeds. This equates to
considerable energy savings in the system. However, at
elevated engine speeds the pump can quickly and precisely
transition to higher flow rates and outlet pressures
necessary to meet engine demands.
Fig. 8 is a side view of an electric valve. Valve
207 is engaged with the body 10 of the pump. Valve 207
is connected to the electrical harness of the engine or
vehicle (not shown). An electrical connector (not shown)
engages the valve 207 at socket 208. When valve 207 is
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de-activated, pressure is vented from chamber 23, thereby
causing the pump to operate in region "A". When valve
207 is activated fluid pressure is admitted to chamber 23
from nozzle 211, thereby causing the pump to operate in
region "B"_ In order *to avoid engine failure caused by
inadequate fluid pressure at high speed, the valve must
be electrically de-activated to vent pressure from
chamber 23. This results in the fail safe situation at
high speed, namely, chamber 23 is vented upon electrical
failure of valve 207.
Fig. 9 is a graph depi=cting the pump performance
including pump flow rate and pressure. A range of engine
speeds is represented on the x-axis and a range of pump
outlet pressures is represented on the y-axis. A range
of pump flow rates is also represented on the second y-
axis.
The engine speed range is from 0 RPM to 8000 RPM.
The outlet pressure range is from 0 bar to 6.00 bar. The
pump flow rate range is from 0 liters/minute to 90
liters/minute.
For the purposes of illustration an engine speed of
-2,000 RPM is selected to demonstrate the characteristics
of the inventive pump. The transition between operating
conditions "A" and "B" is depicted as the "switching
point" at approximately 2,000 RPM.
In this example, valve 207 is OFF at start up and
for engine speeds less than 2,000 RPM, namely, chamber 23
is unpressurized and vented to ambient. For engine
speeds less than approximately 2,000 RPM the maximum pump
outlet pressure (Line Pressure) is approximately 3.6 bar.
The maximum flow rate (Flow Rate) is approximately, 25.0
liters/minute.
For engine speeds greater than approximately 2,000
RPM the pump outlet pressure (Line Pressure) quickly
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transitions down to a minimum outlet pressure of
approximately 2.4 bar at 2,000 RPM up to .3.2 bar at
approximately 7,500 RPM. The flow rate (Flow Rate)
transitions to a maximum of approximately 23.0
liters/minute at 7,500 RPM.
At the transition point the step change in pressure
is approximately 1.4 bar. The step change in flow is
approximately 5 1/min.
The performance transition in this example is caused
by slide 12 pivoting about pivot 18 caused by activation
of valve 207-thereby pressuring chamber 23. Valve 207 is
controlled by an electric signal transmitted by.an engine
ECU, for example. Upon reaching the predetermined engine
speed, in this case approximately 2,000 RPM, ECU 208 (see
Fig. 6) signals valve 207. to close, thereby pressurizing
chamber 23 with fluid pressure equal to that in the main
oil gallery 204. In the event of a failure of valve 207
chamber 23 would depressurize thereby putting the pump in
high discharge pressure mode.
Although a form of the invention has been described
herein, it will be obvious to those skilled in the art
that variations may be made in the construction and
relation of parts without departing from the spirit and'
scope of the invention described herein.
