The present disclosure relates to variable displacement vane pumps. More specifically, the present invention relates to a variable displacement vane pump and system whose output flow is continuously variable and which can be selected independent of the operating speed of the pump.
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 and thus the operating speed and output of the pump varies with the operating speed of the mechanical system. The lubrication requirements of the mechanical system do not directly correspond to the operating speed of the mechanical system.
To deal with these differences, prior art fixed displacement lubricating pumps were generally designed to operate effectively at a target speed and a maximum operating lubricant temperature resulting in an oversupply of lubricating oil at most mechanical system operating. 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 such as low oil temperatures, the overproduction of pressurized lubricating oil can 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 operate and 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, they still result in a significant energy loss as their displacement is 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 lubrication system. Accordingly, such variable displacement pumps must still be designed to provide oil pressures which meet the highest expected mechanical system requirements, despite operating temperatures and other variables, even when the mechanical system operating conditions normally do not necessitate such high requirements.
Another variable displacement pump control system is described within U.S. Pat. No. 7,018,178. The control system includes an electrical 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 requires a continuous supply of current to keep it active through operation of the pump. The use of the electrical power offsets the benefit of controlling the pump to minimize the amount of time where 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 capable of producing a desired lubricant flow while minimizing the energy required to do so.
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 lubrication system for a power transmission device includes a variable displacement vane pump including a moveable control ring for varying the displacement of the pump. A linear actuator directly acts on the control ring for moving the control ring 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.
Furthermore, a lubrication system for a power transmission device includes a variable displacement vane pump having a pivotable pump control ring for varying the displacement of the pump. A control system is operable to vary the displacement of the pump during operation of the pump to achieve an output pressure selected from a continuously variable range of output pressures from the pump which are independent from the operating speed of the pump. The control system includes a linear actuator coupled to the control ring for moving the control ring between minimum and maximum pump displacement positions. The linear actuator includes an electric stepper motor for bi-directionally rotating a nut threadingly engaged with an axially moveable actuator shaft. A coupler interconnects the shaft and the control ring and has multiple degrees of freedom to allow concurrent axial movement of the actuator shaft and rotation of the control ring.
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.
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.
Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.
Example embodiments will now be described more fully with reference to the accompanying drawings.
With reference to
Pump 14 includes a pump rotor 28 rotatably mounted within a rotor chamber 32. A drive shaft 34 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 pump control ring 40. A plurality of pumping chambers 44 are defined by inner surface 38, pump rotor 28 and vane 36. Control ring 40 includes an integrally formed pivot pin 46 positioned within a recess 48 formed in housing 16. It should be appreciated that control ring 40 may be pivotally mounted within housing 16 via many other suitable methods as well. Inner surface 38 of pump control ring 40 has a circular cross-sectional shape. An outer surface 50 of rotor 28 also has a circular cross-sectional shape. The center of surface 38 is eccentrically located with respect to the center of surface 50. 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 rotating pump control ring 40 about pivot pin 46. In particular, the amount of eccentricity between inner surface 38 of pump ring 40 and the outer surface 50 of rotor 28 changes as control ring 40 is rotated.
A radially outwardly protruding arm 60 is integrally formed with control ring 40 and protrudes outside of pumping chambers 44. An actuator assembly 62 is coupled to arm 60 and is operable to move control ring 40 between a first position, a second position and any point therebetween. In the first position, the control ring provides maximum eccentricity and maximum pump flow. At the second position, control ring 40 is positioned at a minimum eccentricity relative to rotor 28 and a minimum of output occurs.
To reduce the magnitude of force required to be provided by actuator assembly 62, a first pressure balance chamber 64 is formed on a first side of control ring 40 while a second pressure balance chamber 66 is formed on an opposite side of control ring 40. First pressure balance chamber 64 and second pressure balance chamber 66 are each in fluid communication with pressurized fluid provided from outlet 24. This arrangement effectively balances the forces acting on control ring 40 thereby minimizing the force required to move control ring 40 and vary the pump output. It should be appreciated that the pressure balanced arrangement may be desirable but is not a requisite portion of pumping system 10. With the pressure balancing chambers, actuator 62 may function but may be tasked to provide a greater input force to move control ring 40.
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. Actuator shaft 78 includes a distal end 80 coupled to arm 60 by a connector 81. A yoke 82 includes a first end 84 rotatably coupled to arm 60 via a pin 86. A second end 88 of yoke 82 is bifurcated defining a slot 90 bounded by first and second fingers 92, 94. A clevis pin 96 rotatably interconnects yoke 82 and actuator shaft 78.
Referring to
In operation, driveshaft 34 begins to rotate and drive rotor 28. Lubricant pressure and flow begin to increase at outlet 24. At start-up, controller 100 locates control ring 40 in the first position. As such, flow increases linearly with the speed of driveshaft 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 control ring 40, the linear motion of actuator shaft 78 changes the eccentricity of the pump and thus the pump output flow.
When the open loop control system of
With reference to
Another alternate interconnection method is shown in
As shown in
Yet another method for interconnecting actuator shaft 78 and control ring 40 is depicted at
A number of coupling techniques have 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 provides sufficient degrees of freedom to allow actuator shaft 78 to linearly translate and transfer a force to the pivotally moveable control ring 40. While many of the interconnections have been described as threaded couplings, it should be appreciated that any number of methods for fixing two components relative to one another 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.
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.
This application claims the benefit of U.S. Provisional Application No. 61/103,593, filed on Oct. 8, 2008. The entire disclosure of the above application is incorporated herein by reference.
Number | Name | Date | Kind |
---|---|---|---|
3323382 | Ruschmann | Jun 1967 | A |
4259039 | Arnold | Mar 1981 | A |
4325215 | Yamamoto | Apr 1982 | A |
4666330 | O'Connell | May 1987 | A |
5048474 | Matayoshi et al. | Sep 1991 | A |
5702242 | Nied-Menninger et al. | Dec 1997 | A |
5807090 | Agner | Sep 1998 | A |
5975868 | Agner | Nov 1999 | A |
6120270 | Parsch | Sep 2000 | A |
6152716 | Agner | Nov 2000 | A |
6164928 | Agner | Dec 2000 | A |
6227816 | Brener et al. | May 2001 | B1 |
6234775 | Agner et al. | May 2001 | B1 |
6244830 | Agner | Jun 2001 | B1 |
6413063 | Parsch et al. | Jul 2002 | B1 |
6485277 | Agner et al. | Nov 2002 | B2 |
6561155 | Williams | May 2003 | B1 |
6896489 | Hunter et al. | May 2005 | B2 |
7018178 | Hunter et al. | Mar 2006 | B2 |
7344361 | Kiefer | Mar 2008 | B2 |
8128386 | Veilleux, Jr. | Mar 2012 | B2 |
Number | Date | Country | |
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20100086424 A1 | Apr 2010 | US |
Number | Date | Country | |
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61103593 | Oct 2008 | US |