Note: Descriptions are shown in the official language in which they were submitted.
VANE PUMP WITH MULTIPLE CONTROL CHAMBERS
FIELD
[0001] The present invention relates to a variable capacity vane pump.
[0002] 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
[0003] 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.
[0004] 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
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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.
[0005] 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.
[0006] 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 output flow and hence pressure of the pump. In this manner, an
equilibrium pressure is obtained at the output of the pump.
[0007] 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.
[0008] 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.
[0009] 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.
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SUMMARY
[0010] 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.
[0011] 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.
[0012] 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.
DRAWINGS
[0013] Preferred embodiments
of the present invention will now be
described, by way of example only, with reference to the attached Figures,
wherein:
[0014] 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;
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[0015] Figure 2 is a front
perspective view of the pump of Figure 1 with
the control ring positioned for maximum rotor eccentricity;
[0016] 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;
[0017] Figure 4 shows a
schematic representation of a prior art variable
capacity vane pump;
[0018] 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;
[0019] Figure 6 provides an
exploded perspective view of an alternate
variable displacement pump;
[0020] Figure 7 provides
another exploded perspective view of the
pump depicted in Figure 6;
[0021] Figure 8 is a cross-
sectional view taken through the pump
depicted in Figures 6 and 7;
[0022] Figure 9 is a
schematic including a cross-sectional view of
another alternate variable capacity vane pump;
[0023] Figure 10 is an
exploded perspective view of the vane pump
depicted in Figure 9; and
[0024] 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
[0025] 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.
[0026] 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.
[0027] 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
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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.
[0028] 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
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.
[0029] 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.
[0030] 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.
[0031] 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
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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.
[0032] 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.
[0033] Pressurized working
fluid in control chamber 60 acts against
pump control ring 44 and, when the force on pump control ring 44 resulting
from
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.
[0034] 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.
[0035] 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.
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[0036] 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.
[0037] However, unlike with
conventional pumps, pump 20 can be
operated at a second equilibrium pressure. Specifically, by selectively
supplying
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.
[0038] 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.
[0039] 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.
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[0040] 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.
[0041] 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.
[0042] 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.
[0043] 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.
[0044] 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.
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[0045] 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.
[0046] 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 also reduced by a vertical component of the biasing
force
324 produced by return spring 56
[0047] 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.
[0048] 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
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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.
[0049] 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.
[0050] 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
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.
[0051] First seal assembly
446 is positioned relative to pivot pin 426 to
define a first radius or moment arm R1. 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 R1 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
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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.
[0052] 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.
Relatively low resistance to fluid discharge is
encountered by incorporating this configuration.
[0053] 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.
[0054] 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.
[0055] Figures 9-11 depict
another alternate variable displacement
pump at reference numeral 500. Pump 500 may form a portion of a lubrication
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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.
[0056] 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.
[0057] 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
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.
[0058] First seal assembly
528 is positioned at a first distance from a
center of pivot pin 558 to define a first moment arm R1. 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 R1 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 R1 and R2 may be designed to be
unequal if a permanent contribution from the pump outlet pressure is desired.
As
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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 R1 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 R1 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.
[0059] 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
chamber 550, may or may not contribute to the pressure controlling function as
described in relation to the relative lengths of moment arms R1 and R2.
[0060] 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.
[0061] 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 solely by the
claims
appended hereto.
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