Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
705062CA2DIV Patent
VANE PUMP WITH MULTIPLE CONTROL CHAMBERS
FIELD OF THE INVENTION
[0001] The
present invention relates to a variable capacity vane pump.
More specifically, the present invention relates to a variable capacity vane
pump
including multiple control chambers. Different sources of pressurized fluid
may be
provided to the control chambers to control the pump displacement.
BACKGROUND OF THE INVENTION
[0002] Variable capacity
vane pumps are well known and can include a
capacity adjusting element, in the form of a pump control ring that can be
moved
to alter the rotor eccentricity of the pump and hence alter the volumetric
capacity
of the pump. If the pump is supplying a system with a substantially constant
orifice
size, such as an automobile engine lubrication system, changing the output
flow of
the pump is equivalent to changing the pressure produced by the pump.
[0003] Having
the ability to alter the volumetric capacity of the pump to
maintain an equilibrium pressure is important in environments such as
automotive
lubrication pumps, wherein the pump will be operated over a range of operating
speeds. In such environments, to maintain an equilibrium pressure it is known
to
employ a feedback supply of the working fluid (e.g. lubricating oil) from the
output
of the pump to a control chamber adjacent the pump control ring, the pressure
in
the control chamber acting to move the control ring, typically against a
biasing force
from a return spring, to alter the capacity of the pump.
[0004] When
the pressure at the output of the pump increases, such as
when the operating speed of the pump increases, the increased pressure is
applied
to the control ring to overcome the bias of the return spring and to move the
control
ring to reduce the capacity of the pump, thus reducing the output flow and
hence
the pressure at the output of the pump.
[0005]
Conversely, as the pressure at the output of the pump drops, such
as when the operating speed of the pump decreases, the decreased pressure
applied to the control chamber adjacent the control ring allows the bias of
the return
spring to move the control ring to increase the capacity of the pump, raising
the
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output flow and hence pressure of the pump. In this manner, an equilibrium
pressure is obtained at the output of the pump.
[0006] The
equilibrium pressure is determined by the area of the control
ring against which the working fluid in the control chamber acts, the pressure
of the
working fluid supplied to the chamber and the bias force generated by the
return
spring.
[0007]
Conventionally, the equilibrium pressure is selected to be a
pressure which is acceptable for the expected operating range of the engine
and
is thus somewhat of a compromise as, for example, the engine may be able to
operate acceptably at lower operating speeds with a lower working fluid
pressure
than is required at higher engine operating speeds. In order to prevent undue
wear
or other damage to the engine, the engine designers will select an equilibrium
pressure for the pump which meets the worst case (high operating speed)
conditions. Thus, at lower speeds, the pump will be operating at a higher
capacity
than necessary for those speeds, wasting energy pumping the surplus,
unnecessary, working fluid.
[0008] It is
desired to have a variable capacity vane pump which can
provide at least two selectable equilibrium pressures in a reasonably compact
pump housing. It is also desired to have a variable capacity vane pump wherein
reaction forces on the pivot pin for the pump control ring are reduced.
SUMMARY OF THE INVENTION
[0009] It is
an object of the present invention to provide a novel variable
capacity vane pump which obviates or mitigates at least one disadvantage of
the
prior art.
[0010] A
variable capacity vane pump includes a first control chamber
between a pump casing and a first portion of a pump control ring. The first
portion
of the control ring circumferentially extends on either side of a pivot pin. A
second
control chamber is provided between the pump casing and a second portion of
the
pump control ring. The first and second control chambers are operable to
receive
pressurized fluid to create a force to move the pump control ring to reduce
the
volumetric capacity of the pump. A return spring biases the pump ring toward a
position of maximum volumetric capacity.
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[0011] A
variable volumetric capacity vane pump includes a pump casing
including a pump chamber having an inlet port and an outlet port. A pump
control
ring pivots within the pump chamber to alter the volumetric capacity of the
pump.
A rotor is rotatably mounted within the pump control ring and includes slots
in
receipt of slidable vanes. First, second, and third control chambers are
formed
between the pump casing and an outer surface of the pump control ring. The
first
and second control chambers are selectively operable to receive pressurized
fluid
to create forces to move the pump control ring to reduce the volumetric
capacity of
the pump. The third chamber is in constant receipt of pressurized fluid from
the
outlet of the pump. A return spring is positioned within the casing to act
between
the pump ring and the casing to bias the pump ring toward a position of
maximum
volumetric capacity and act against the force generated by the pressurized
fluid
within the first and second control chambers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012]
Preferred embodiments of the present invention will now be
described, by way of example only, with reference to the attached Figures,
wherein:
[0013] Figure
1 is a front view of a variable capacity vane pump in
accordance with the present invention with the control ring positioned for
maximum
rotor eccentricity;
[0014] Figure
2 is a front perspective view of the pump of Figure 1 with
the control ring positioned for maximum rotor eccentricity;
[0015] Figure
3 is the a front view of the pump of Figure 1 with the control
ring position for minimum eccentricity and wherein the areas of the pump
control
chambers are in hatched line;
[0016] Figure
4 shows a schematic representation of a prior art variable
capacity vane pump;
[0017] Figure
5 shows a front view of the pump of Figure 1 wherein the
rotor and vanes have been removed to illustrate the forces within the pump;
[0018] Figure
6 provides an exploded perspective view of an alternate
variable displacement pump;
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[0019] Figure
7 provides another exploded perspective view of the pump
depicted in Figure 6;
[0020] Figure
8 is a cross-sectional view taken through the pump
depicted in Figures 6 and 7;
[0021] Figure 9 is a
schematic including a cross-sectional view of
another alternate variable capacity vane pump;
[0022] Figure
10 is an exploded perspective view of the vane pump
depicted in Figure 9; and
[0023] Figure
11 is a partial plan view of the pump depicted in Figures 9
and 10 having the pump control ring positioned at a location of minimum pump
volumetric capacity.
DETAILED DESCRIPTION
[0024] A variable capacity vane pump in accordance with an
embodiment of the present invention is indicated generally at 20 in Figures 1,
2
and 3.
[0025]
Referring now to Figures 1, 2 and 3, pump 20 includes a housing
or casing 22 with a front face 24 which is sealed with a pump cover (not
shown)
and a suitable gasket, to an engine (not shown) or the like for which pump 20
is to
supply pressurized working fluid.
[0026] Pump 20
includes an input member or drive shaft 28 which is
driven by any suitable means, such as the engine or other mechanism to which
the
pump is to supply working fluid, to operate pump 20. As drive shaft 28 is
rotated,
a pump rotor 32 located within a pump chamber 36 is turned with drive shaft
28. A
series of slidable pump vanes 40 rotate with rotor 32, the outer end of each
vane
40 engaging the inner surface of a pump control ring 44, which forms the outer
wall
of pump chamber 36. Pump chamber 36 is divided into a series of working fluid
chambers 48, defined by the inner surface of pump control ring 44, pump rotor
32
and vanes 40. The pump rotor 32 has an axis of rotation that is eccentric from
the
center of the pump control ring 44.
[0027] Pump
control ring 44 is mounted within casing 22 via a pivot pin
52 which allows the center of pump control ring 44 to be moved relative to the
center of rotor 32. As the center of pump control ring 44 is located
eccentrically
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with respect to the center of pump rotor 32 and each of the interior of pump
control
ring 44 and pump rotor 32 are circular in shape, the volume of working fluid
chambers 48 changes as the chambers 48 rotate around pump chamber 36, with
their volume becoming larger at the low pressure side (the left hand side of
pump
chamber 36 in Figure 1) of pump 20 and smaller at the high pressure side (the
right
hand side of pump chamber 36 in Figure 1) of pump 20. This change in volume of
working fluid chambers 48 generates the pumping action of pump 20, drawing
working fluid from an inlet port 50 and pressurizing and delivering it to an
outlet
port 54.
[0028] By moving pump
control ring 44 about pivot pin 52 the amount of
eccentricity, relative to pump rotor 32, can be changed to vary the amount by
which
the volume of working fluid chambers 48 change from the low pressure side of
pump 20 to the high pressure side of pump 20, thus changing the volumetric
capacity of the pump. A return spring 56 biases pump control ring 44 to the
position, shown in Figures 1 and 2, wherein the pump has a maximum
eccentricity.
[0029] As
mentioned above, it is known to provide a control chamber
adjacent a pump control ring and a return spring to move the pump ring of a
variable capacity vane pump to establish an equilibrium output flow, and its
related
equilibrium pressure.
[0030] However, in
accordance with the present invention, pump 20
includes two control chambers 60 and 64, best seen in Figure 3, to control
pump
ring 44. Control chamber 60, the rightmost hatched area in Figure 3, is formed
between pump casing 22, pump control ring 44, pivot pin 52 and a resilient
seal
68, mounted on pump control ring 44 and abutting casing 22. In the illustrated
embodiment, control chamber 60 is in direct fluid communication with pump
outlet
54 such that pressurized working fluid from pump 20 which is supplied to pump
outlet 54 also fills control chamber 60.
[0031] As will
be apparent to those of skill in the art, control chamber 60
need not be in direct fluid communication with pump outlet 54 and can instead
be
supplied from any suitable source of working fluid, such as from an oil
gallery in an
automotive engine being supplied by pump 20.
[0032]
Pressurized working fluid in control chamber 60 acts against
pump control ring 44 and, when the force on pump control ring 44 resulting
from
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the pressure of the pressurized working is sufficient to overcome the biasing
force
of return spring 56, pump control ring 44 pivots about pivot pin 52, as
indicated by
arrow 72 in Figure 3, to reduce the eccentricity of pump 20. When the pressure
of
the pressurized working fluid is not sufficient to overcome the biasing force
of return
spring 56, pump control ring 44 pivots about pivot pin 52, in the direction
opposite
to that indicated by arrow 72, to increase the eccentricity of pump 20.
[0033] Pump 20
further includes a second control chamber 64, the
leftmost hatched area in Figure 3, which is formed between pump casing 22,
pump
control ring 44, resilient seal 68 and a second resilient seal 76. Resilient
seal 76
abuts the wall of pump casing 22 to separate control chamber 64 from pump
inlet
50 and resilient seal 68 separates chamber 64 from chamber 60.
[0034] Control
chamber 64 is supplied with pressurized working fluid
through a control port 80. Control port 80 can be supplied with pressurized
working
fluid from any suitable source, including pump outlet 54 or a working fluid
gallery
in the engine or other device supplied from pump 20. A control mechanism (not
shown) such as a solenoid operated valve or diverter mechanism is employed to
selectively supply working fluid to chamber 64 through control port 80, as
discussed below. As was the case with control chamber 60, pressurized working
fluid supplied to control chamber 64 from control port 80 acts against pump
control
ring 44.
[0035] As should now be apparent, pump 20 can operate in a
conventional manner to achieve an equilibrium pressure as pressurized working
fluid supplied to pump outlet 54 also fills control chamber 60. When the
pressure
of the working fluid is greater than the equilibrium pressure, the force
created by
the pressure of the supplied working fluid over the portion of pump control
ring 44
within chamber 60 will overcome the force of return spring 56 to move pump
ring
44 to decrease the volumetric capacity of pump 20. Conversely, when the
pressure
of the working fluid is less than the equilibrium pressure, the force of
return spring
56 will exceed the force created by the pressure of the supplied working fluid
over
the portion of pump control ring 44 within chamber 60 and return spring 56
will to
move pump ring 44 to increase the volumetric capacity of pump 20.
[0036]
However, unlike with conventional pumps, pump 20 can be
operated at a second equilibrium pressure. Specifically, by selectively
supplying
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pressurized working fluid to control chamber 64, via control port 80, a second
equilibrium pressure can be selected. For example, a solenoid-operated valve
controlled by an engine control system, can supply pressurized working fluid
to
control chamber 64, via control port 80, such that the force created by the
pressurized working fluid on the relevant area of pump control ring 44 within
chamber 64 is added to the force created by the pressurized working fluid in
control
chamber 60, thus moving pump control ring 44 further than would otherwise be
the
case, to establish a new, lower, equilibrium pressure for pump 20.
[0037] As an
example, at low operating speeds of pump 20, pressurized
working fluid can be provided to both chambers 60 and 64 and pump ring 44 will
be moved to a position wherein the capacity of the pump produces a first,
lower,
equilibrium pressure which is acceptable at low operating speeds.
[0038] When
pump 20 is driven at higher speeds, the control mechanism
can operate to remove the supply of pressurized working fluid to control
chamber
64, thus moving pump ring 44, via return spring 56, to establish a second
equilibrium pressure for pump 20, which second equilibrium pressure is higher
than
the first equilibrium pressure.
[0039] While
in the illustrated embodiment chamber 60 is in fluid
communication with pump outlet 54, it will be apparent to those of skill in
the art
that it is a simple matter, if desired, to alter the design of control chamber
60 such
that it is supplied with pressurized working fluid from a control port,
similar to control
port 80, rather than from pump outlet 54. In such a case, a control mechanism
(not
shown) such as a solenoid operated valve or a diverter mechanism can be
employed to selectively supply working fluid to chamber 60 through the control
port.
As the area of control ring 44 within each of control chambers 60 and 64
differs, by
selectively applying pressurized working fluid to control chamber 60, to
control
chamber 64 or to both of control chambers 60 and 64 three different
equilibrium
pressures can be established, as desired.
[0040] As will
also be apparent to those of skill in the art, should
additional equilibrium pressures be desired, pump casing 22 and pump control
ring
44 can be fabricated to form one or more additional control chambers, as
necessary.
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[0041] Pump 20
offers a further advantage over conventional vane
pumps such as pump 200 shown in Figure 4. In conventional vane pumps such
as pump 200, the low pressure fluid 204 in the pump chamber exerts a force on
pump ring 216 as does the high pressure fluid 208 in the pump chamber. These
forces result in a significant net force 212 on the pump control ring 216 and
this
force is largely carried by pivot pin 220 which is located at the point where
force
212 acts.
[0042]
Further, the high pressure fluid within the outlet port 224
(indicated in dashed line), acting over the area of pump ring 216 between
pivot pin
220 and resilient seal 222, also results in a significant force 228 on pump
control
ring 216. While force 228 is somewhat offset by the force 232 of return spring
236,
the net of forces 228 less force 232 can still be significant and this net
force is also
largely carried by pivot pin 220.
[0043] Thus
pivot pin 220 carries large reaction forces 240 and 244, to
counter net forces 212 and 228 respectively, and these forces can result in
undesirable wear of pivot pin 220 over time and/or "stiction" of pump control
ring
216, wherein it does not pivot smoothly about pivot pin 220, making fine
control of
pump 200 more difficult to achieve.
[0044] As
shown in Figure 5, the low pressure side 300 and high
pressure side 304 of pump 20 result in a net force 308 which is applied to
pump
control ring 44 almost directly upon pivot pin 52 and a corresponding reaction
force,
shown as a horizontal (with respect to the orientation shown in the Figure)
force
312, is produced on pivot pin 52. Unlike conventional variable capacity vane
pumps such as pump 200, in pump 20 resilient seal 68 is located relatively
closely
to pivot pin 52 to reduce the area of pump control ring 44 upon which the
pressurized working fluid in control chamber 60 acts and thus to significantly
reduce the magnitude of the force 316 produced on pump control ring 44.
[0045]
Further, control chamber 60 is positioned such that force 316
includes a horizontal component, which acts to oppose force 308 and thus
reduce
reaction force 312 on pivot pin 52. The vertical (with respect to the
orientation
shown in the Figure) component of force 316 does result in a vertical reaction
force
320 on pivot pin 52 but, as mentioned above, force 316 is of less magnitude
than
would be the case with conventional pumps and the vertical reaction force 320
is
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also reduced by a vertical component of the biasing force 324 produced by
return
spring 56
[0046] Thus,
the unique positioning of control chamber 60 and return
spring 56, with respect to pivot pin 52, results in reduced reaction forces on
pivot
pin 52 and can improve the operating lifetime of pump 20 and can reduce
"stiction"
of pump control ring 44 to allow smoother control of pump 20. As will be
apparent
to those of skill in the art, this unique positioning is not limited to use in
variable
capacity vane pumps with two or more equilibrium pressures and can be employed
with variable capacity vane pumps with single equilibrium pressures.
[0047] Figures 6-8
depict another variable capacity vane pump
constructed in accordance with the teachings of the present disclosure and
identified at reference numeral 400. Pump 400 includes a housing 402 including
a
first cover 404 fixed to a second cover 406 by a plurality of fasteners 408. A
dowel
pin 409 aligns the first and second covers. Pump 400 includes an input or a
drive
shaft 410 having at least one end protruding from housing 402. Drive shaft 410
may be driven by any suitable means such as an internal combustion engine. A
rotor 412 is fixed for rotation with drive shaft 410 and positioned within a
pumping
chamber 414 defined by pump housing 402. Vanes 416 are slidably engaged
within radially extending slots 418 defined by rotor 412. Outer surfaces 420
of each
vane slidably engage a sealing surface 422 of a moveable pump control ring
424.
Sealing surface 422 is shaped as a circular cylinder having a center which may
be
offset from a center of drive shaft 410. Retaining rings 425 limit the inboard
extent
to which the vanes may slide to maintain engagement of surfaces 420 with
surface
422.
[0048] Pump control ring
424 is positioned within chamber 414 and is
pivotally coupled to housing 402 via a pivot pin 426. Pump control ring 424
includes
a radially outwardly extending arm 428. A bias spring 430 engages arm 428 to
urge pump control ring 424 toward a position of maximum capacity.
[0049] Pump
control ring 424 includes first through third projections
identified at reference numerals 432, 434, 436. Each of the first through
third
projections includes an associated groove 438, 440, 442. A first seal assembly
446 is positioned within first groove 438 to sealingly engage housing 402. A
second seal assembly 448 is positioned within second groove 440 to sealingly
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engage a different portion of housing 402. A third seal assembly 450 is
positioned
within third groove 442. Third seal assembly 450 sealingly engages another
portion of housing 402. Each seal assembly includes a cylindrically shaped
first
elastomer 452 engaging a second elastomer 454 having a substantially
rectangular
cross-section. Each seal assembly is positioned within an associated seal
groove.
A first chamber 460 extends between first seal assembly 446 and third seal
assembly 450 and between an outer surface of pump control ring 424 and housing
402. A second chamber 462 is defined between first seal assembly 446 and
second seal assembly 448, as well as the other surface of pump control ring
424
and housing 402.
[0050] First
seal assembly 446 is positioned relative to pivot pin 426 to
define a first radius or moment arm Ri . The position of third seal assembly
450
also defines a radius or moment arm R2 in relation to the center of pivot pin
426.
The length of moment arm R I defined by first seal assembly 446 is greater
than
the length of moment arm R2 defined by the position of third seal assembly 450
such that a turning moment is generated when first chamber 460 is pressurized.
The turning moment urges pump control ring 424 to oppose the force applied by
bias spring 430. First seal assembly 446 is circumferentially spaced apart
from
third seal assembly 450 an angle greater than 100 degrees with the angle
vertex
being the center of the pump control ring cavity bounded by surface 422.
Figure 8
depicts this angle as approximately 117 degrees. It should be appreciated that
the
position of first seal assembly 446 and second seal assembly 448 relative to
pivot
pin 426 also causes the pressurized fluid entering the second chamber to
impart a
moment of pump control ring 424 that opposes the force applied by bias ring
430.
[0051] An outlet port
470 extends through housing 402 to allow
pressurized fluid to exit pump 400. An enlarged discharge cavity 472 is
defined by
housing 402. Enlarged discharge cavity 472 extends from third seal assembly
450
to outlet port 470. It should be appreciated that enlarged discharge cavity
extends
on either side of pivot pin 426. This feature is provided by having the outer
surface
476 of pump control ring 424 being spaced apart from an inner wall 478 of
housing
402. In particular, first cover 404 includes a stanchion 482 including an
aperture
484 for receipt of pivot pin 426. Stanchion 482 is spaced apart from inner
wall 478.
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Relatively low resistance to fluid discharge is encountered by incorporating
this
configuration.
[0052] In
operation, pump 400 may be configured to operate in at least
two different modes. In each of the modes of operation, first chamber 460 is
provided pressurized fluid at pump outlet pressure. In a first mode of
operation,
second chamber 462 may be selectively supplied pressurized fluid from any
source
of pressure through the use of an on/off solenoid valve. In this first
operation mode,
an upper equilibrium pressure of pump 400 is defined by the pump outlet
pressure
and a lower equilibrium pressure may be defined by the second source.
[0053] In a second mode
of operation, pump 400 may be associated with
a proportional solenoid valve which may be operable to continuously vary the
pressure to second chamber 462 and allow intermediate equilibrium pressures.
As
such, pump 400 operates at an infinite number of equilibrium pressures and not
only the two fixed pressures as provided in the first arrangement.
[0054] Figures 9-11
depict another alternate variable displacement
pump at reference numeral 500. Pump 500 may form a portion of a lubrication
system 502 useful for supplying pressurized lubricant to an engine,
transmission
or other vehicle power transfer mechanism. Lubrication system 502 includes a
reservoir 504 providing fluid to an inlet pipe 506 in fluid communication with
an inlet
508 of pump 500. An outlet 510 of pump 500 provides pressurized fluid to a
cooler
512, a filter 514 and a main gallery 516. Pressurized fluid travelling through
main
gallery 516 is supplied to the component to be lubricated, such as an internal
combustion engine. Pressurized fluid is also provided to a feedback line 518.
Feedback line 518 is in direct communication with a first control chamber 520
of
pump 500. A solenoid valve 522 acts to control the fluid communication between
feedback line 518 and a second control chamber 524.
[0055] Pump
500 is similar to pump 400 regarding the use of a pivoting
pump control ring 526, first through fourth seal assemblies 528, 530, 532,
534, a
bias spring 536, vanes 538, a rotor 540, a rotor shaft 542 and retaining rings
544.
Similar elements will not be described in detail.
[0056] First
seal assembly 528 and second seal assembly 530 act in
concert with an outer surface 546 of control ring 526 and a cavity wall 548 to
at
least partially define first control chamber 520. Second control chamber 524
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extends between second seal assembly 530 and third seal assembly 532 as well
as between outer surface 546 and cavity wall 548. An outlet passage 550
extends
between first seal assembly 528 and fourth seal assembly 534. A stanchion 554
includes an aperture 556 in receipt of a pivot pin 558 to couple control ring
526 for
rotation with stanchion 554. As previously described in relation to pump 400,
the
enlarged outlet passage 550 substantially reduces restriction to pressurized
fluid
exiting pump 500. In yet another alternate arrangement not depicted, pivot pin
558
may provide a sealing function and allow removal of fourth seal assembly 534.
[0057] First
seal assembly 528 is positioned at a first distance from a
center of pivot pin 558 to define a first moment arm Ri. In similar fashion, a
moment arm R2 is defined by the position of fourth seal assembly 534 in
relation
to pivot pin 558. If moment arm lengths Ri and R2 are set to be equal, the
pressure
within outlet passage 550 provides no contribution to pressure regulation. On
the
other hand, moment arms Ri and R2 may be designed to be unequal if a
permanent contribution from the pump outlet pressure is desired. As such,
outlet
passage 550 may function as a third control chamber. For example, it may be
beneficial to provide a pressure regulation at a vehicle cold start condition.
At cold
start, it may be desirable to urge control ring 526 toward a position of
minimum
displacement as shown in Figure 11. This may be accomplished by having
moment arm Ri be longer than moment arm R2. Alternatively, it may be desirable
to compensate for forces acting internally within pump 500 and acting on pump
control ring 526. To address this concern, it may be desirable to construct
moment
arm Ri at a length less than the length of moment arm R2 to urge pump control
ring 526 toward the maximum displacement position. Figure 9 represents control
ring 526 at a position of maximum eccentricity, thereby providing maximum pump
displacement. For the pump depicted in Figures 9-11, first seal assembly 528
is
circumferentially spaced apart from fourth seal assembly 534 an angle greater
than
80 degrees.
[0058] In
operation, first control chamber 520 is always active and may
be in receipt of pressurized fluid from any source, such as the pump output.
Second control chamber 524 is switched on and off via solenoid 522. The supply
of pressurized fluid may be from any source. Outlet passage 550, or third
control
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chamber 550, may or may not contribute to the pressure controlling function as
described in relation to the relative lengths of moment arms Ri and R2.
[0059] Pump
500 need only be associated with an on/off type solenoid
valve 522 due to the provision of three control chambers. Third control
chamber
550 provides for a very low restriction outlet flow path. First control
chamber 520
and second control chamber 524 allow two equilibrium pressures that are
determined by sources other than the pump outlet pressure.
[0060] The
above-described embodiments of the disclosure are intended
to be examples of the present disclosure and alterations and modifications may
be
effected thereto, by those of skill in the art, without departing from the
scope of the
disclosure which is defined by the claims appended hereto.
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