VARIABLE PRESSURE PUMP WITH HYDRAULIC PASSAGE

Abstract

A variable capacity pump includes a control ring moveable within a pump chamber to alter the volumetric capacity of the pump. First and second control chambers individually receive pressurized fluid to create forces to bias the control ring in a predetermined direction. A return spring urges the control ring toward a maximum volumetric capacity pump position. The control ring connects and disconnects the second control chamber from a source of pressurized fluid based on a position of the control ring. Forces from the control chambers and the spring act in combination with one another or against one another and against the spring force to establish first and second equilibrium pressures based on a pressurized or vented condition of the second control chamber.

Claims

1. A variable capacity pump, comprising: a pump casing including a pump chamber, an inlet and an outlet; a pump member movably positioned within the pump chamber, the pump member pumping a fluid from the inlet, through the pump chamber and to the outlet; a control ring being movable within the pump casing to alter the volumetric capacity of the pump; first and second control chambers at least partially defined by the pump casing and the control ring, the control chambers operable to individually receive pressurized fluid to create individual forces to bias the control ring toward a first position corresponding to a minimum volumetric capacity of the pump; a return spring urging the control ring toward a second position corresponding to a maximum volumetric capacity of the pump, a force of the return spring acting against a combined force generated by the pressurized fluid within the control chambers to establish a first equilibrium pressure, wherein the control ring connects and disconnects the second control chamber from a source of the pressurized fluid based on a position of the control ring, the return spring acting against the force of the first control chamber to establish a secondary equilibrium pressure when the second control chamber is disconnected from the source of pressurized fluid.

2. The variable capacity pump of claim 1, wherein the control ring includes a channel connecting and disconnecting the second control chamber with the source of pressurized fluid based on the position of the control ring.

3. The variable capacity pump of claim 2, wherein the channel connects and disconnects the second control chamber with a discharge passage, the channel being connected to the discharge passage to reduce the fluid pressure within the second control chamber when the control ring is in a position disconnecting the pressurized fluid source from the second control chamber.

4. The variable capacity pump of claim 3, wherein the control ring blocks an opening to the discharge passage when the channel connects the pressurized fluid source and the second control chamber.

5. The variable capacity pump of claim 3, wherein the channel includes a blind recess extending along a surface of the control ring that slides relative to the pump casing.

6. The variable capacity pump of claim 1, wherein the pump casing includes a supply passage having a feeding orifice in fluid communication with the pressurized fluid source, the feeding orifice being positioned within the pump chamber and selectively blocked based on the position of the control ring.

7. The variable capacity pump of claim 1, wherein the pump member is positioned within a cavity of the control ring.

8. The variable capacity pump of claim 7, wherein the pump member is driven by a rotatable rotor.

9. The variable capacity pump of claim 1, further including a third control chamber at least partially defined by the control ring and the pump casing and operable to receive pressurized fluid to create a force urging the control ring toward the first position.

10. The variable capacity pump of claim 9, further including an electrically operated hydraulic solenoid valve to control the supply of pressurized fluid to the third chamber, the pump outputting fluid according to a high mode pressure curve when the third chamber is not supplied with pressurized fluid, and a low mode pressure curve when the third chamber is supplied with pressurized fluid.

11. The variable capacity pump of claim 10, wherein the electrically operated solenoid valve is an on/off type.

12. The variable capacity pump of claim 10, wherein the electrically operated solenoid valve is a proportional type operable to modulate the pressure in the third control chamber between a pump outlet pressure and either atmospheric pressure or a pump inlet pressure.

13. The variable capacity pump of claim 1, further including an inner rotor and an outer rotor positioned within a cavity of the control ring.

14. The variable capacity pump of claim 13, wherein the pump member includes a pendulum slide coupled to one of the inner and outer rotors.

15. The variable capacity pump of claim 1, further including a rotor rotatably positioned within the pump chamber and wherein the pump member includes a plurality of vanes engaging the rotor and the control ring.

16. The variable capacity pump of claim 2, wherein the channel extends across a width of the control ring in a direction perpendicular to a direction that the control ring moves.

17. A variable capacity pump, comprising: a pump casing including a pump chamber, an inlet and an outlet; a pump member movably positioned within the pump chamber, the pump member pumping a fluid from the inlet, through the pump chamber and to the outlet; a control ring being movable within the pump casing to alter the volumetric capacity of the pump; first and second control chambers at least partially defined by the pump casing and the control ring, the first control chamber operable to receive pressurized fluid to create a force urging the control ring toward a first position corresponding to a minimum volumetric capacity of the pump, the second control chamber operable to receive pressurized fluid to create a force urging the control ring toward a second position corresponding to a maximum volumetric capacity of the pump; and a return spring urging the control ring toward the second position, a force of the return spring acting against the force generated by the pressurized fluid within the first control chamber to establish a first equilibrium pressure, wherein the control ring connects and disconnects the second control chamber from a source of the pressurized fluid based on a position of the control ring, the return spring force acting with the force generated by the second control chamber and against the force generated by the first control chamber to establish a secondary equilibrium pressure when the second control chamber is connected to the source of pressurized fluid.

18. The variable capacity pump of claim 17, wherein the control ring includes a channel connecting and disconnecting the second control chamber with the source of pressurized fluid based on the position of the control ring.

19. The variable capacity pump of claim 18, wherein the channel connects and disconnects the second control chamber with a discharge passage, the channel being connected to the discharge passage to reduce the fluid pressure within the second control chamber when the control ring is in a position disconnecting the pressurized fluid source from the second control chamber.

20. The variable capacity pump of claim 18, wherein the control ring blocks an opening to the discharge passage when the channel connects the pressurized fluid source and the second control chamber.

21. The variable capacity pump of claim 18, wherein the channel includes a blind recess extending along a surface of the control ring that slides relative to the pump casing.

22. The variable capacity pump of claim 17, wherein the pump casing includes a supply passage having a feeding orifice in fluid communication with the pressurized fluid source, the feeding orifice being positioned within the pump chamber and selectively blocked based on the position of the control ring.

23. The variable capacity pump of claim 17, further including a third control chamber at least partially defined by the control ring and the pump casing and operable to receive pressurized fluid to create a force urging the control ring toward the first position.

24. The variable capacity pump of claim 23, further including an electrically operated hydraulic solenoid valve to control the supply of pressurized fluid to the third chamber, the pump outputting fluid according to a high mode pressure curve when the third chamber is not supply with pressurized fluid, and a low mode pressure curve when the third chamber is supplied with pressurized fluid.

25. The variable capacity pump of claim 23, wherein the electrically operated solenoid valve is an on/off type.

26. The variable capacity pump of claim 23, wherein the electrically operated solenoid valve is a proportional type operable to modulate the pressure in the third control chamber between a pump outlet pressure and either atmospheric pressure or a pump inlet pressure.

27. The variable capacity pump of claim 17, further including an inner rotor and an outer rotor positioned within a cavity of the control ring.

28. The variable capacity pump of claim 27, wherein the pump member includes a pendulum slide coupled to one of the inner and outer rotors.

Description

DRAWINGS

[0015] The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

[0016] FIG. 1 is a partial plan view of a variable capacity pump constructed in accordance with the teachings of the present disclosure;

[0017] FIGS. 2A-2D show the pump at different eccentricity stages;

[0018] FIG. 3 is a graph of the pressure output of the pump depicted in FIGS. 2A-2D versus the oil pressure demand of the mechanical system;

[0019] FIG. 4 is a partial plan view of another variable capacity pump;

[0020] FIGS. 5A-5D show the pump of FIG. 4 different eccentricity stages;

[0021] FIG. 6 is a partial plan view of another variable capacity pump;

[0022] FIGS. 7A-7D show the pump of FIG. 6 at different eccentricity stages;

[0023] FIG. 8 is a graph of the pressure output of the pump shown in FIGS. 7A-7D versus the minimum and maximum oil pressure demand of a mechanical system;

[0024] FIG. 9 is a partial plan view of another variable capacity pump;

[0025] FIGS. 10A-10D show the pump of FIG. 9 at different eccentricity stages; and

[0026] FIG. 11 is a partial plan view of a variable capacity pump including a pendulum slider mechanism.

[0027] Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

DESCRIPTION

[0028] A variable capacity vane pump in accordance with an embodiment of the present invention is indicated generally at 20 in FIG. 1. Pump 20 includes a casing or housing 22 with a front face 24 which is sealed with a pump cover (not shown) and optionally a suitable gasket (not shown), to an engine (not shown) or the like, for which pump 20 is to supply pressurized working fluid.

[0029] Pump 20 includes a 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 driven by drive shaft 28. A series of slidable pump vanes 40 rotate with rotor 32, the outer end of each vane 40 engaging the inner circumferential 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.

[0030] Pump control ring 44 is mounted within housing 22 via a pivot pin 52 that 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 FIG. 1) of pump 20, and smaller at the high pressure side (the right hand side of pump chamber 36 in FIGS. 2A-2D) of pump 20. This change in volume of working fluid chambers 48 generates the pumping action of pump 20, drawing working fluid from a pump inlet 50 and pressurizing and delivering it to a pump outlet 54.

[0031] 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 engages a tab 55 of control ring 44 and housing 22 to bias pump control ring 44 to the position, shown in FIG. 1, wherein the pump has a maximum eccentricity.

[0032] A first control chamber 61 is formed between pump housing 22, pump control ring 44, a seal 71 and a seal 72, mounted on pump control ring 44 and abutting housing 22. In the illustrated configuration, first control chamber 61 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 first control chamber 61.

[0033] As will be apparent to those of skill in the art, first control chamber 61 need not be in direct fluid communication with pump outlet 54 and can instead be supplied from any suitable source of working fluid, directly or indirectly, such as from oil gallery in an automotive engine being supplied by pump 20.

[0034] A second control chamber 62 is formed between pump housing 22, pump control ring 44, seal 72 and a seal 73, mounted on pump control ring 44 and abutting housing 22.

[0035] Second control chamber 62 is supplied with pressurized fluid via a feeding orifice 81 into the housing 22, and located partially under the pump control ring 44. Pressurized fluid for orifice 81 can be supplied either from pump outlet 54, or other source of working fluid, such as an oil gallery in an automotive engine. A discharge passage 82 is located in the housing 22 and under the pump control ring 44 in communication with the pump inlet 50. A channel or recess 83 extends across the width of control ring 44 in a direction perpendicular to a direction that the control ring moves. As shown in FIGS. 2A-2D, feeding orifice 81, discharge passage 82 and recess 83 are positioned and sized to create a pump pressure output versus speed as shown in FIG. 3. There are four distinctive steps, shown in FIGS. 2A-2D, that generate the pump pressure output curve.

[0036] In curve portion A-B1, both first control chamber 61 and second control chamber 62 are energized because the feeding orifice 81 is connected to second control chamber 62 and the discharge passage 82 is not connected, being completely covered by the pump control ring 44. However, at low pump operating speeds, the force and consequently the turning moment around the pivot pin 52 created by the pressure build up in the two control chambers is insufficient to counter the force of the return spring 56, and as such the pump remains at maximum eccentricity.

[0037] In curve portion B1-C1, the pressure build up due to higher speeds of the pump has generated enough force, from the pressure in the two control chambers and consequently the turning moment, acting around the pivot pin 52 to exceed the force of the return spring 56, which is providing an opposing turning moment acting around the pin to reduce the pump control ring eccentricity. In this phase, the slight movement of the control ring 44 has not yet opened the discharge passage 82 to second control chamber 62, hence both control chambers are still working.

[0038] Curve portion C1-D1 represents a transition phase, where the movement of the pump control ring started in portion B1-C1 has reached a point where the recess 83 is changing second control chamber 62 connections. Pressure feeding orifice 81 is closed and discharge passage 82 is opened, ultimately venting second control chamber 62. As such, with a further increase in operating speed and pressures, only first control chamber 61 is energized and a new force balance is established around pivot pin 52. The pressure from first control chamber 61 acts against the force generated by the return spring 56. In this phase, the slight pressure increase in first control chamber 61 cannot move the control ring 44 and the pump eccentricity remains essentially constant.

[0039] In curve portion D1-E1, the pressure within first control chamber 61 increases due to higher pump operating speeds to generate enough force from the pressure in the first control chamber 61, acting as a turning moment, around the pivot pin 52 to exceed the force of the return spring 56, which is providing an opposing turning moment around the pin. A reduction of the pump control eccentricity occurs.

[0040] Another pump constructed according to the principles of the present disclosure is shown in FIG. 4 and identified at reference number 20a. In this arrangement, two control chambers are located on opposite sides of the pivot pin 52a, and act against each other. The pump outlet 54a is connected to a pressure port 57a via a drilled internal channel within the housing 22a. In this arrangement, a first control chamber 61a is formed in the pump chamber 36a, between pump control ring 44a, pump housing 22a, seal 71a and pivot pin 52a, and when energized, it creates a force, acting as a turning moment around pivot pin 52a, opposite to the force of the return spring 56a. In the illustrated configuration, first control chamber 61a is supplied with pressurized fluid from engine oil gallery or pump outlet via a feeding channel 84a.

[0041] A second control chamber 62a is formed in the pump chamber 36a, between pump control ring 44a, pump housing 22a, seal 72a and pivot pin 52a, and when energized, it creates a force, acting as a turning moment, around pivot pin 52a, acting in the same direction as the force of the return spring 56a.

[0042] Second control chamber 62a is supplied with pressurized fluid via a feeding orifice 81a into the housing 22a, and located under the pump control ring 44a. Pressurized fluid for orifice 81a can be supplied either from pump outlet 54a, or other source of working fluid, directly or indirectly, such as an oil gallery in an automotive engine. A discharge passage 82a located in the housing 22a and partially under the pump control ring 44a, is in connection to the pump inlet 50a. A channel 83a is shaped as a blind recess having an opening at an edge of control ring 44a that extends along a surface of the control ring that slides relative to pump housing 22. As shown in FIGS. 5A-5D, pump 20a is equipped with feeding orifice 81a, discharge passage 82a, and connecting channel 83a in pump control ring 44a to create a pump pressure output as shown in FIG. 3. There are four distinctive steps, shown in FIGS. 5A-5D, that generate that pump pressure output curve.

[0043] In curve portion A-B1, first control chamber 61a is energized via feeding channel 84a and second control chamber 62a is not energized, since second control chamber 62a is vented to the inlet via discharge passage 82a and the connecting channel 83a. The feeding orifice 81a is not connected to second control chamber 62a, being completely covered by the pump control ring 44a. At low pump operating speeds, the force, acting as a turning moment, around the pivot pin 52a created by the pressure build up in first control chamber 61a is not sufficient to counter the force created by the return spring 56a, and as such the pump remains at maximum eccentricity.

[0044] At curve portion B1-C1, the pressure build up due to higher operating speeds of the pump has generated enough force from first control chamber 61a, acting as a turning moment, around the pivot pin 52a to exceed the force of the return spring 56a, acting as an opposing turning moment, around the pin, determining a reduction of the pump eccentricity. In this phase, the slight movement of control ring 44a has not yet connected the feeding orifice 81a to the connecting channel 83a, hence only first control chamber 61a is still working.

[0045] Curve portion C1-D1 represents a transition phase, where the movement of the pump control ring started in portion B1-C1 has reached a point where the control channel 83a is changing second control chamber 62a connections, by connecting pressure feeding orifice 81a with second control chamber 62a and closing the second control chamber 62a connection to discharge passage 82a. As such, with further increase in pump operating speed and pressures, both control chambers 61a and 62a are energized and a new force balance is established around pivot pin 52a. The pressure from first control chamber 61a acts against the force generated by the return spring 56a and second control chamber 62a.

[0046] At curve portion D1-E1, the pressure build up due to higher operating speeds of the pump has generated enough force from first control chamber 61a, acting as a turning moment, around the pivot pin 52a to exceed the force of the return spring 56a combined with the force from second control chamber 62a, determining a reduction of the pump eccentricity.

[0047] It should be appreciated that the feeding orifice 81, discharge passage 82, and recess 83 described in relation to pump 20 and depicted in FIG. 1 may alternatively be applied to pump 20a in lieu of feeding orifice 81a, discharge passage 82a and recess 83a. It is also contemplated that the geometry incorporated to provide the passive control features of pump 20a may be applied to pump 20.

[0048] Another alternate variable capacity pump is presented in FIG. 6 and identified as reference number 20b. Pump 20b is substantially similar to pump 20 shown in FIG. 1, to which a third control chamber 63b connected to an electrically controlled hydraulic solenoid valve 91b was added. Use of the third control chamber 63b provides the flexibility to generate either a high (A-B1-C1-D1-E1) or a low (A-B2-C2-D2-E2) pump pressure output in relation to operating speed as shown in FIG. 8. It may be beneficial to provide a pump operable to meet different demand requirements that may occur during the operation on an automobile engine. For example, many newer vehicles are selectively operable in a high load engine pressure demand mode, as well as the more traditional low load engine pressure demand mode. A pressure output may be required from the pump to provide lubricating and cooling oil to an auxiliary system such as an internal combustion engine piston cooling system. The high load engine pressure demand curve in FIG. 8 may include a greater inflection in the pressure versus engine speed curve at a predetermined engine speed. One skilled in the art should appreciate that the present configuration of pump 20b equipped with third control chamber 63b and solenoid valve 91b provides a simple and cost effective solution to the requirement for substantially different pressure demand curves. In particular, it is contemplated that electrically controlled hydraulic solenoid valve 91b is an inexpensive on/off valve. It should also be appreciated that if greater control is required, the electrically controlled solenoid valve may be a proportional type operable to modulate the pressure in third control chamber 63b between the system pressure and either atmospheric pressure or pump inlet pressure.

[0049] As presented in FIG. 6, first control chamber 61b is formed between pump housing 22b, pump control ring 44b, seal 71b and seal 72b, mounted on pump control ring 44b and abutting housing 22b. In the illustrated configuration, first control chamber 61b is in direct fluid communication with pump outlet 54b such that pressurized working fluid from pump 20b which is supplied to pump outlet 54b also fills first control chamber 61b.

[0050] As will be apparent to those skilled in the art, first control chamber 61b need not be in direct fluid communication with pump outlet 54b and can instead be supplied from any suitable source of working fluid, directly or indirectly, such as from an oil gallery in an automotive engine being supplied by pump 20b.

[0051] Second control chamber 62b is formed between pump housing 22b, pump control ring 44b, seal 73b and seal 74b, mounted on pump control ring 44b and abutting housing 22b. Second control chamber 62b is supplied with pressurized fluid via a feeding orifice 81b into the housing 22b, and located partially under the pump control ring 44b. Pressurized fluid for orifice 81b can be supplied either from pump outlet 54b, or other source of working fluid, such as an oil gallery in an automotive engine. A discharge passage 82b located into the housing 22b and under the pump control ring 44b, is in connection to the pump inlet 50b.

[0052] Third control chamber 63b is formed between pump housing 22b, pump control ring 44b, seal 72b and seal 74b and is supplied in pressurized oil from the solenoid valve 91b via a feeding channel 85b. As shown in FIGS. 7A-7D, pump 20b includes feeding orifice 81b, discharge passage 82b and recess 83b in the pump control ring 44b, designed and sized to create a pump pressure output as shown in FIG. 8. When third control chamber 63b is not energized with pressurized working fluid from the solenoid valve, the pump works in high mode, and generates the pressure curve A-B1-C1-D1-E1 as shown in FIG. 8. There are four steps, shown in FIGS. 7A-7D, that generate the high mode pump pressure output curve.

[0053] In curve portion A-B1, both first control chamber 61b and second control chamber 62b are energized, because the feeding orifice 81b is connected to second control chamber 62b and the discharge passage 82b is not connected, being completely covered by the pump control ring 44b. At low pump operating speeds, the force, acting as a turning moment, around the pivot pin 52b created by the pressure build up in control chambers 61b, 62b is not sufficient to counter the force created by the return spring 56b, which is acting around the pin as an opposing turning moment, and as such the pump remains at maximum eccentricity.

[0054] In curve portion B1-C1, the counter pressure build up due to higher operating speeds of the pump has generated enough force from the two control chambers, acting as a turning moment, around the pivot pin 52b to exceed the force of the return spring 56b, acting as an opposing turning moment, around the pin to reduce of the pump eccentricity. In this phase, the slight movement of the control ring 44b has not yet opened the discharge passage 82b to second control chamber 62b, hence both control chambers are still working.

[0055] Curve portion C1-D1 represents a transition phase, where the movement of the pump control ring started in portion B1-C1 has reached a point where the recess 83b is changing second control chamber 62b connections, by closing its pressure feeding orifice 81b and opening the discharge passage 82b, ultimately venting second control chamber 62b. As such, with a further increase in pump operating speed, system pressure and feeding pressures, only second control chamber 62b is energized and a new force balance is established around pivot pin 52b, the pressure from second control chamber 62b acting against the force generated by the return spring 56b.

[0056] At curve portion D1-E1, the pressure due to higher operating speeds of the pump has generated enough force from first control chamber 61b, acting around the pivot pin 52b to exceed the force of the return spring 56b acting around the pin, causing a reduction of the pump eccentricity.

[0057] Pressure curve A-B2-C2-D2-E2 is generated in a similar fashion with the exception that solenoid valve 91b is energized to provide pressurized fluid to third control chamber 63b via feeding channel 85b. A force acting in an opposite direction to the spring force is applied when third control chamber 63b is pressurized. As such, the eccentricity of control ring 44b is reduced. An offset, low pressure output curve results.

[0058] Another variable capacity pump 20c is depicted in FIG. 9. Pump 20c is substantially similar to pump 20a with the exception that a third control chamber 63c connected to an electrically controlled hydraulic solenoid valve 91c are included. Control of valve 91c allows pump 20c to generate either the high (A-B1-C1-D1-E1) or low (A-B2-C2-D2-E2) pump pressure output in relation to operating speed. As presented in FIG. 9, two control chambers are located on one side of the pivot pin 52c, while a third control chamber and the return spring 56c are on an opposite side of the pivot. The pump outlet 54c is connected to the pressure port 57c via a drilled internal channel within the housing 22c. Pump 20c includes first control chamber 61c formed in the pump chamber 36c, between pump control ring 44c, pump housing 22c, seal 71c and pivot pin 52c, and when energized, it creates a force, acting as a turning moment around pivot pin 52c, opposite to the force of the return spring 56c. In the illustrated configuration, first control chamber 61c is supplied with pressurized fluid from engine oil gallery or pump outlet via a feeding channel 84c.

[0059] A second control chamber 62c is formed in the pump chamber 36c, between pump control ring 44c, pump housing 22c, seal 72c and pivot pin 52c, and when energized, it creates a force, acting as a turning moment, around pivot pin 52c, acting in the same direction as the momentum created by the force of the return spring 56c.

[0060] Second control chamber 62c is supplied with pressurized fluid via a feeding orifice 81c into the housing 22c, and located under the pump control ring 44c. Pressurized fluid for orifice 81c can be supplied either from pump outlet 54c, or other source of working fluid, directly or indirectly, such as an oil gallery in an automotive engine. A discharge passage 82c located into the housing 22c and partially under the pump control ring 44c, is in connection to the pump inlet 50c.

[0061] A third control chamber 63c is formed between pump housing 22c, pump control ring 44c, seal 71c and seal 73c and is supplied in pressurized oil from the solenoid valve 91c via a feeding orifice 87c. As shown in FIGS. 10A-10D, pump 20c includes feeding orifice 81c, discharge passage 82c and connecting channel 83c in the pump control ring 44c. Pump 20c is designed and sized to create a pump pressure output as shown in FIG. 8. When third control chamber 63c is not pressurized, pump 20c generates pump pressure output curve A-B1-C1-D1-E1 as shown in FIGS. 10A-10D.

[0062] At curve portion A-B1, first control chamber 61c is energized and second control chamber 62c is not energized, since second control chamber 62c is vented to the inlet via discharge passage 82c and the connecting channel 83c. The feeding orifice 81c is not connected to second control chamber 62c, being completely covered by the pump control ring 44c. At low pump operating speeds, the force, acting as a turning moment, around the pivot pin 52c created by the pressure build up in first control chamber 61c is not sufficient to counter the force created by the return spring 56c, and as such the pump remains at maximum eccentricity.

[0063] At curve portion B1-C1, the pressure build up due to higher operating speeds of the pump has generated enough force from first control chamber 61c, acting as a turning moment, around the pivot pin 52c to exceed the force of the return spring 56c, acting as an opposing turning moment, around the pin, determining a reduction of the pump eccentricity. In this phase, the slight movement of the control ring 44c has not yet connected the feeding orifice 81c to the connecting channel 83c, hence only first control chamber 61c is still working.

[0064] Curve portion C1-D1 represents a transition phase, where the movement of the pump control ring started in portion B1-C1 has reached a point where the control channel 83c is changing second control chamber 62c connections, by connecting pressure feeding orifice 81c with second control chamber 62c and closing the second control chamber 62c connection to discharge passage 82c. As such, with further increase in pump operating speed and pressures, both first and second control chambers 61c, 62c are energized and a new force balance is established around pivot pin 52c. The pressure from first control chamber 61c acts against the force generated by the return spring 56c and the second control chamber 62c.

[0065] At curve portion D1-E1, the pressure build up due to higher operating speeds of the pump has generated enough force from the first control chamber 61c, acting as a turning moment, around the pivot pin 52c to exceed the force of the return spring 56c combined with the force from second control chamber 62c, determining a reduction of the pump eccentricity.

[0066] Pressure curve A-B2-C2-D2-E2 is generated in a similar fashion when solenoid valve 91c is emerged. Pressurized working fluid is provided to third control chamber 63c via the feeding orifice 87c.

[0067] FIG. 11 depicts another alternate pump identified at 20d. Pump 20d is substantially similar to pump 20, with the exception that the pumping members used to urge fluid from the inlet to the outlet are configured as a pendulum-slide cell instead of the vane arrangement previously described. Accordingly, like elements will retain their previously introduced reference numerals including a d suffix. Pump 20d includes an inner rotor 102 coupled to a plurality of pendulum slides 104 via an outer rotor 106. Pendulum slides 104 are pivotally mounted to outer rotor 106. Pendulum slides 104 are movable within radially extending slots 108 extending into inner rotor 102. Inner rotor 102 together with pendulum slides 104 and outer rotor 106 define pumping chamber 110. According to the rotational position of inner rotor 102, outer rotor 106, pumping chambers 110 serve as suction chambers or as pressure chambers for transferring fluid. It should be appreciated with either the outer rotor 106 or the inner rotor 102 may be a driven member of pump 20d.

[0068] The above-described configurations are intended to be examples and alterations and modifications may be effected thereto, by those of skill in the art, without departing from the scope of the present disclosure.

[0069] Moreover, it will be obvious to those skilled in the art that additional control chambers can be configured on either side of the pivot pin and these could be passively controlled by additional similar features in the control ring and therefore responsive to movement of the control ring. One or more of the control chambers may be actively controlled by an electrically operated solenoid valve to optimize the volume and pressure output characteristics of a pump to suit a given application.