DIRECT CONTROL LINEAR VARIABLE DISPLACEMENT VANE PUMP

Abstract

A fluid pumping system for a power transmission device includes a variable displacement vane pump having a housing containing a rotor, a plurality of vanes coupled to the rotor and a linearly translatable slide for varying the displacement of the pump. A control system varies the displacement of the pump and provides a fluid output pressure selected from a continuously variable range of output pressures which are independent from the operating speed of the pump. The control system includes a linear actuator for moving the slide between minimum and maximum pump displacement positions. The linear actuator includes an electric stepper motor for bi-directionally translating an actuator shaft acting on the slide.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/157,601, filed on Mar. 5, 2009. The entire disclosure of the above application is incorporated herein by reference.

FIELD

The present disclosure relates to a fluid pumping system for an automobile. More specifically, the present disclosure relates to a variable displacement vane pump and control system for providing a continuously variable output flow independent of the operating speed of the pump.

BACKGROUND

Mechanical systems, such as internal combustion engines and automatic transmissions, typically include a lubrication pump to provide lubricating oil, under pressure, to many of the moving components and/or subsystems of the mechanical systems. In most cases, the lubrication pump is driven by a rotating component of the mechanical system. The operating speed and output of the pump varies with the operating speed of the mechanical system. The lubrication requirements of the mechanical system, however, typically do not directly correspond to the operating speed of the mechanical system.

Previously known fixed displacement lubricating pumps were generally designed to provide sufficient flow at a relatively low speed corresponding to an engine idle speed and a maximum operating lubricant temperature. This design philosophy resulted in an oversupply of lubricating oil during a large portion of vehicle operation. In at least one arrangement, a pressure relief valve was provided to return the surplus lubricating oil back into the pump inlet or oil sump to avoid over pressure conditions in the mechanical system. In some operating conditions, the overproduction of pressurized lubricating oil may be 500% of the mechanical system's needs. The result is a significant amount of energy being used to pressurize the lubricating oil which is subsequently exhausted through the relief valve.

More recently, variable displacement vane pumps have been employed as lubrication oil pumps. Such pumps generally include a control ring, or other mechanism, which can be operated to alter the volumetric displacement of the pump and thus its output at an operating speed. Typically, a feedback mechanism is supplied with pressurized lubricating oil from the output of the pump to alter the displacement of the pump to avoid over pressure situations in the engine throughout the expected range of operating conditions of the mechanical system.

While such variable displacement pumps provide some improvements in energy efficiency over fixed displacement pumps, a significant energy loss may result due to pump displacement being controlled, directly or indirectly, by the output pressure of the pump which changes with the operating speed of the mechanical system, rather than with the changing requirements of the mechanical system.

Another variable displacement pump control system is described within U.S. Pat. No. 7,018,178. The control system includes an electric solenoid coupled to a variable displacement pump for varying the displacement of the pump during engine operation. While an electric solenoid may provide an additional degree of pump control, several disadvantages from its use exist. In particular, a solenoid typically requires a continuous supply of current to keep it active through operation of the pump. The electrical power consumption may offset the benefit of controlling the pump to minimize the amount of time that the pump provides excess lubricant flow. Furthermore, the maximum force capability of the solenoid is limited by the size of the electromagnet and the current applied thereto. For certain applications, the size of the electromagnet required to provide the desired force may be prohibitive for packaging the solenoid within an automotive environment. Accordingly, a need exists for an improved lubrication system for producing a desired lubricant flow while minimizing the energy required to do so.

SUMMARY

This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

A fluid pumping system for a power transmission device includes a variable displacement vane pump having a housing containing a rotor, a plurality of vanes coupled to the rotor and a linearly translatable slide for varying the displacement of the pump by changing its eccentricity. A control system varies the displacement of the pump and provides a fluid output pressure selected from a continuously variable range of output pressures that are independent from the operating speed of the pump. The control system includes a linear actuator for moving the slide between minimum and maximum pump displacement positions. The linear actuator includes an electric stepper motor for bi-directionally translating an actuator shaft acting on the slide.

Furthermore, the present disclosure describes a fluid pumping system for a power transmission device including a variable displacement vane pump having a linearly moveable slide for varying the displacement of the pump. A linear actuator moves the slide between maximum and minimum pump displacement positions. The linear actuator includes an electric motor for rotating a drive member. The drive member engages a driven actuator shaft to cause linear translation of the actuator shaft in response to rotation of the drive member. A control system includes a controller for signaling the actuator to extend or retract the actuator shaft to vary the pump displacement.

Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

DRAWINGS

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.

FIG. 1 is a cross-sectional view of an exemplary directly controlled variable displacement vane pump;

FIG. 2 is an enlarged fragmentary perspective view of the pumping system depicted in FIG. 1;

FIG. 3 is a fragmentary perspective view of a connector coupling the actuator shaft and the slide;

FIG. 4 is a schematic of an open loop control system for controlling the variable displacement vane pump;

FIG. 5 is a schematic depicting a closed loop control system cooperating with the variable displacement vane pump;

FIG. 6 is a fragmentary perspective view of another variable displacement vane pump;

FIG. 7 is a plan view of a slide and actuator arrangement of the pump depicted in FIG. 6; and

FIG. 8 is a plan view of the housing for the pump shown in FIG. 6.

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

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference to the accompanying drawings.

With reference to FIGS. 1-3, a pumping system 10 is shown plumbed in communication with an exemplary power transmission device 12. Power transmission device 12 is shown schematically and may include any number of devices including an internal combustion engine, a transmission, a transfer case, an axle assembly or the like. Pumping system 10 includes a variable displacement pump 14 including a housing 16 with a flange 17 for mounting pump 14 to power transmission device 12. Alternatively, housing 16 may be integrally formed with the power transmission device. An inlet 18 extends through housing 16 interconnecting a low pressure gallery 20 with a sump 22 storing the fluid to be pumped. An outlet 24 of housing 16 interconnects a high pressure chamber 26 with power transmission device 12.

Pump 14 includes a pump rotor 28 rotatably mounted within a rotor chamber 32. A drive shaft 34 is part of power transmission device 12 and is fixed for rotation with pump rotor 28 to provide energy for pumping the lubricant. A plurality of pump vanes 36 are coupled to rotor 28 and radially slidable relative thereto. The radial outer end of each vane 36 engages an inner surface 38 of a slide 40. A plurality of pumping chambers 44 are defined by inner surface 38, pump rotor 28 and vanes 36.

Slide 40 includes a first arm 46 slidably positioned within a first recess 48 formed in housing 16. Slide 40 also includes a second arm 50 slidably positioned within a second housing recess 52. Slide 40 also includes substantially parallel opposite walls 54, 56 positioned in close proximity to walls 58, 60 of housing 16, respectively. Based on the geometric features previously described, slide 40 may linearly translate between first and second positions but is restricted from rotation relative to housing 16.

Inner surface 38 of slide 40 has a circular cross-sectional shape. An outer surface 61 of rotor 28 also has a circular cross-sectional shape. A centerline of cylindrical surface 38 is eccentrically located with respect to the center of outer surface 61. Accordingly, the volume of each pumping chamber 44 changes as rotor 28 rotates. The volume of chambers 44 increases at the low pressure side of the pump in communication with inlet 18. Pumping chambers 44 decrease in size at the high pressure side in communication with outlet 24 of pump 14. The change in volume of pumping chambers 44 generates the pumping action by drawing working fluid from sump 22 and delivering pressurized fluid from outlet port 24.

The output of pump 14 may be varied by translating slide 40. In particular, the amount of eccentricity between inner surface 38 of slide 40 and the outer surface 61 of rotor 28 is a maximum when slide 40 is at the first position shown in FIG. 1. Pump output flow is greatest at this position. When slide 40 is at the second position, eccentricity and the output of pump 14 are minimized and may be zero.

A linear actuator assembly 62 is coupled to second arm 50 and is operable to move slide 40 along an axis 63 to the first position, the second position and any point therebetween. Accordingly, pump 14 may be controlled to output a fluid pressure selected from a continuously variable range of output pressures that are independent from the operating speed of the pump.

To reduce the magnitude of force required to be provided by actuator assembly 62, a pressure balance chamber 64 surrounds a portion of slide 40. Pressure balance chamber 64 is in fluid communication with pressurized fluid provided from outlet 24. The shape and position of pressure balance chamber 64 effectively balances the forces acting on slide 40 thereby minimizing the force required to move slide 40 and vary the pump output. Pressure balance chamber 64 extends along one side of slide 40 on opposite sides of a line perpendicularly intersecting axis 63 and extending through the centerline of surface 38. It should be appreciated that the pressure balanced arrangement may be desirable but is not a requisite portion of pumping system 10. Without the pressure balancing chamber, actuator 62 may function but may be tasked to provide a greater input force to move slide 40.

As shown in FIGS. 2 and 3, actuator assembly 62 includes an electric stepper motor 70 including a stator 72 and a rotor 74 supported in a housing 75. Rotor 74 is coupled to a nut 76 that is threadingly engaged with an externally threaded actuator shaft 78. Housing 75 includes a flange 79 coupled to pump housing 16. Flange 79 may alternatively be fixed to power transmission device 12.

FIG. 3 depicts actuator shaft 78 including a distal end 80 coupled to second arm 50 by a clip 82. Actuator shaft 78 includes a groove 84 in receipt of a semi-circular portion 86 of clip 82. Clip 82 also includes an elongated upper portion 88 that may be translated into a slot 90 formed within second arm 50 to couple actuator shaft 78 to slide 40.

Referring to FIG. 4, actuator assembly 62 is in communication with a controller 100, a power supply 102 and a drive 104. Controller 100 may be programmed with an algorithm or algorithms referencing speed, pressure, flow or temperature maps to enable the controller to control the flow of the pump using an open loop control system as depicted in FIG. 4. FIG. 5 depicts a closed loop control system including a pressure sensor 106 in communication with controller 100.

In operation, drive shaft 34 begins to rotate and drive rotor 28. Lubricant pressure and flow begin to increase at outlet 24. At start-up, controller 100 locates slide 40 in the first position to provide maximum flow. As such, flow increases linearly with the speed of drive shaft 34. At a particular speed, the flow produced by pump 14 will exceed the lubrication requirements of power transmission device 12. At this time, controller 100 provides a signal to drive 104. Drive 104 is in receipt of electrical power from power supply 102. Drive 104 generates electrical pulses and supplies pulses to electric stepper motor 70 causing nut 76 to rotate in one of two directions to extend or retract actuator shaft 78 as signaled by controller 100. Because actuator shaft 78 is directly coupled to slide 40, the linear motion of actuator shaft 78 and slide 40 changes the eccentricity of the pump and thus the pump output flow.

When the open loop control system of FIG. 4 is implemented, controller 100 continues to signal drive 104 to position slide 40 based on any one or more of speed, pressure, flow or temperature mappings of the control algorithm. A dedicated pressure sensor associated with pump 14 is not required. Alternatively, the closed loop feedback system depicted in FIG. 5 includes pressure sensor 106 providing a signal indicative of the pressure output by pump 14 to controller 100. Controller 100 outputs a signal to drive 104 to position slide 40 and cause pump 14 to output a desired lubricant pressure.

A coupling technique has been described to facilitate a ridged mounting of actuator housing 75 to pump housing 16 or another portion of power transmission device 12. The connection allows actuator shaft 78 to linearly translate and transfer a force to linearly moveable slide 40. It should be appreciated that any number of methods for fixing actuator shaft 78 to slide 40 such as pinning, riveting, welding, press-fitting, adhesive bonding or the like, are contemplated as being within the scope of the present disclosure. Furthermore, while the closed loop control system was previously described as being in communication with a pressure sensor, it should be appreciated that any number of other sensors may be implemented to provide controller 100 with data for decision making relating to the control of actuator 62 and pumping system 10.

FIGS. 6 and 7 depict an alternate variable displacement pump identified at reference numeral 150. Pump 150 is substantially similar to pump 14. Accordingly, like elements will retain their previously introduced reference numerals including a prime suffix. Pump 150 differs from pump 14 in the manner in which slide 40′ is urged toward the first or maximum eccentricity position. One end of a compression spring 152 is positioned within a pocket 154 formed within slide 40′. An opposite end of spring 152 is positioned within a recess 156 formed in housing 16′. Spring 152 is continuously under compression to urge slide 40′ toward the first position.

Through this arrangement, actuator 62′ is no longer required to move slide 40′ toward the first position. Actuator 62′ applies a force to move slide 40′ toward the second position. As such, an adapter 158 may be fixed to actuator shaft 78′. Adapter 158 includes an end face 160 in contact with a land 162 formed on slide 40′. End face 160 and land 162 remain in contact with one another due to the force provided by compression spring 152. At the first or most eccentric position, land 162 is forced into contact with a seat 164 formed on housing 16′.

During pump operation, actuator 62′ may be selectively energized to extend actuator shaft 78′ and move slide 40′ from the first position toward the second position. Once electrical energy is no longer supplied to actuator 62′, the position of slide 40′ will be maintained due to the internal configuration of stepper motor 70′. To move slide 40′ toward the first position, actuator 62′ is energized once again to allow slide 40′ to translate under the force provided by spring 152. An infinite number of positions between the first position providing maximum flow and the second position providing minimum flow may be obtained through control of actuator 62′ as previously discussed.

Furthermore, the foregoing discussion discloses and describes merely exemplary embodiments of the present disclosure. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims, that various changes, modifications and variations may be made therein without departing from the spirit and scope of the disclosure as defined in the following claims.

Claims

1. A fluid pumping system for a power transmission device, comprising:

a variable displacement vane pump having a housing containing a rotor, a plurality of vanes coupled to the rotor and a linearly translatable slide for varying the displacement of the pump; and

a control system for varying the displacement of the pump and providing a fluid output pressure selected from a continuously variable range of output pressures which are independent from the operating speed of the pump, the control system including a linear actuator for moving the slide between minimum and maximum pump displacement positions, the linear actuator including an electric stepper motor for bi-directionally translating an actuator shaft acting on the slide.

2. The fluid pumping system of claim 1 wherein the housing includes a pressure balance chamber in communication with the slide and in receipt of pressurized working fluid, the fluid balancing forces acting on the slide wherein the resultant force on the slide approaches zero.

3. The fluid pumping system of claim 2 wherein the control system includes a controller in communication with a drive providing electrical pulses to the stepper motor.

4. The fluid pumping system of claim 1 wherein the slide includes a first arm having substantially parallel opposite faces positioned proximate substantially parallel opposite walls of a recess formed in the housing, the first arm restricting relative rotation between the slide and the housing.

5. The fluid pumping system of claim 4 wherein the slide includes a second arm having substantially parallel opposite faces positioned proximate substantially parallel opposite walls of another recess formed in the housing, the second arm restricting relative rotation between the slide and the housing, wherein the first and second arms are diametrically opposed to one another.

6. The fluid pumping system of claim 5 wherein the second arm includes a pocket in receipt of the actuator shaft.

7. The fluid pumping system of claim 6 further including a clip interconnecting the actuator shaft and the second arm.

8. The fluid pumping system of claim 2 wherein the slide includes a bore in receipt of the vanes and the pressure balance chamber extends along one side of the slide to allow fluid to act on portions of the slide on opposite sides of a centerline extending through the slide bore.

9. The fluid pumping system of claim 1 wherein the actuator shaft and the slide each translate parallel to one another.

10. The fluid pumping system of claim 9 wherein the slide includes a bore in receipt of the vanes, the translation line of the actuator shaft intersecting a centerline of the slide bore.

11. The fluid pumping system of claim 1 further including a spring urging the slide into contact with the actuator shaft, wherein the actuator shaft is not fixed to the slide.

12. A fluid pumping system for a power transmission device, comprising:

a variable displacement vane pump including a linearly moveable slide for varying the displacement of the pump;

a linear actuator for moving the slide between maximum and minimum pump displacement positions, the linear actuator including an electric motor for rotating a drive member, the drive member engaging a driven actuator shaft to cause linear translation of the actuator shaft in response to rotation of the drive member; and

a control system including a controller for signaling the actuator to extend or retract the actuator shaft to vary the pump displacement.

13. The fluid pumping system of claim 12 wherein the controller operates in an open loop control mode and is not in receipt of a signal indicative of the pressure being output by the pump.

14. The fluid pumping system of claim 12 wherein the controller operates in a closed loop mode in response to a signal indicative of the pressure output by the pump.

15. The fluid pumping system of claim 12 wherein the electric motor is a stepper motor operable to position the slide at various positions between the minimum and maximum displacement positions.

16. The fluid pumping system of claim 12 wherein the pump includes a housing with a pressure balance chamber in communication with the slide and in receipt of pressurized working fluid, the fluid balancing forces acting on the slide wherein the resultant force on the slide approaches zero.

17. The fluid pumping system of claim 16 wherein the slide includes a first arm having substantially parallel opposite faces positioned proximate substantially parallel opposite walls of a recess formed in the housing, the first arm restricting relative rotation between the slide and the housing.

18. The fluid pumping system of claim 17 wherein the slide includes a second arm having substantially parallel opposite faces positioned proximate substantially parallel opposite walls of another recess formed in the housing, the second arm restricting relative rotation between the slide and the housing, wherein the first and second arms are diametrically opposed to one another.

19. The fluid pumping system of claim 18 wherein the second arm includes a pocket in receipt of the actuator shaft.

20. The fluid pumping system of claim 19 further including a clip interconnecting the actuator shaft and the second arm.

21. The fluid pumping system of claim 12 further including a spring urging the slide into contact with the actuator shaft, wherein the actuator shaft is not fixed to the slide.

22. The fluid pumping system of claim 12 wherein the actuator shaft and the slide each translate along the same line.