Abstract:
A control system for a variable displacement pump. The control system is operably associated with an engine control unit for passively or actively controlling the output of the pump in response to signals from the engine control unit.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a non-provisional application basing priority on U.S. Provisional Application No. 60/369,829, filed Apr. 3, 2002. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to the control of the output of a variable displacement pump. More specifically, the present invention relates to control of an oil pump for oil pressure control in an internal combustion engine, transmission or the like.  
       BACKGROUND OF THE INVENTION  
       [0003]     It is desirable to properly lubricate the moving components in an internal combustion engine and provide hydraulic power. Typically, oil pumps used in engines are directly connected to the crankshaft of the engine. While this configuration is generally adequate, there are some disadvantages. First, there is not much control of the actual discharge pressure relative to the pressure needed by the engine under certain/given operating conditions. For instance, during start-up conditions it may be desirable to have higher initial pressure to get engine oil into the engine. At crucial start-up, this cannot be facilitated with the direct drive pumps. Additionally, with the pump shaft RPM directly tied to the engine RPM, in many areas over the RPM range the engine oil pressure is higher or lower than that which is desirable. This results in inefficient use of engine power and/or inefficient engine oil lubrication.  
         [0004]     In commonly assigned co-pending application U.S. Ser. No. 10/021,566, a mechanical hydraulic arrangement is shown for providing control of a variable displacement vane pump. This provides for a more optimized control of engine oil pressure. However, it is yet desirable to provide some further control depending on engine needs or variables. Thus, in the present invention there is provided a method of control and system for control of a variable displacement vane pump by the use of an engine control unit which actuates a solenoid for directly or indirectly controlling the stroke of a variable displacement vane pump.  
       SUMMARY OF THE INVENTION  
       [0005]     A control system for a hydraulic variable displacement vane-type pump wherein input from an engine control unit actuates a solenoid for controlling the engine oil pressure to the desired level under any operating conditions.  
         [0006]     A further understanding of the present invention will be had in view of the description of the drawings and detailed description of the invention, when viewed in conjunction with the subjoined claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0008]      FIG. 1  is a hydraulic schematic showing a first embodiment of the present invention;  
         [0009]      FIG. 2  is a hydraulic schematic showing a second embodiment of the present invention  
         [0010]      FIG. 2   a  is a variation of the second embodiment of the present invention;  
         [0011]      FIG. 3  is a hydraulic schematic showing a third embodiment of the present invention;  
         [0012]      FIG. 4  is a hydraulic schematic showing a forth embodiment of the present invention;  
         [0013]      FIG. 5  is a hydraulic schematic showing a fifth embodiment of the present invention;  
         [0014]      FIG. 6  is a hydraulic schematic showing a sixth embodiment of the present invention;  
         [0015]      FIG. 7  is a hydraulic schematic showing a seventh embodiment of the present invention; and  
         [0016]      FIG. 8  is a hydraulic schematic showing an eighth embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.  
         [0018]     In the present invention, a method of controlling a variable displacement pump  10  for an engine is provided. In a preferred embodiment of the invention that incorporates a solenoid  26 , unless stated otherwise, it should be understood that the solenoid  26  is normally, or is defaulted to, the closed position when no power is supplied to the solenoid  26 . When the solenoid  26  is in the closed position there will be high fluid displacement by the pump  10 . Thus, in an emergency event, such as when there is an electrical failure, the solenoid  26  will move to its default position so the engine oil pressure will remain high and that the vehicle can continue operating until it can serviced. However, it is to be understood that with the solenoid in a closed position the system could also be configured so that there is fluid displacement with the pump  10 .  
         [0019]     In accordance with  FIG. 1 , the pump is a vane-type variable displacement pump, as set forth in co-pending application Ser. No. 10/021,566, filed Dec. 12, 2000, the specification of which is incorporated by reference herein. Specifically, the pump is designed for an engine lubrication circuit. The pump is generally shown at  10 . The pump  10  may be a vane pump which has the displacement varied by movement of an eccentric ring  11 . It is also possible to incorporate other types of pumps, in which the stroke or displacement may be adjusted during operation.  
         [0020]     A flow control valve  12  is used to mechanically vary the displacement of a pump  10 , by moving the eccentric ring  11 , based on an engine pilot pressure  14  acting on the flow control valve  12  which controls the volume of oil in each control chamber on each side of the eccentric ring  11 . A compression spring  16  acts against a pilot pressure  14  for maintaining some pressure on the flow control valve  12  and to provide a return pressure in absence of the pilot pressure  14 . The flow control valve  12  in this particular embodiment is a spool valve such as a three-way spool valve. However, it should be understood that the flow control valve  12  can be a spool valve of any type of configuration. Also, the flow control valve  12  does not necessarily need to be a spool valve at all, as will be seen in  FIG. 6 . The compression spring  16  gives the spool portion of the valve  12  travel distance that is proportional to the differential between the actual pressure of the system and the desired or target system pressure. The differential pressure is variable by way of a valve  18 , which controls the amount of pressure acting on the variable target piston  20  against spring  22  for varying the amount of spring  16  pressure on valve  12 . An engine control unit (ECU)  24  monitors the engine conditions and parameters such as temperature, speed and engine load. In this embodiment, the engine control unit  24  monitors the engine conditions pressure, speed, and engine load and then selects a desired oil pressure, and sends the appropriate current to the solenoid  26  acting on valve  18 . This varies the pressure acting on the piston  20 , changing its position and thereby reducing or increasing target pressure, depending upon the desired engine oil pressure target. The flow control valve  12  then regulates the pump&#39;s  10  eccentric ring  11  to maintain target pressure.  
         [0021]     With respect to  FIG. 2 , like items referenced in  FIG. 1  are similarly designated with reference numerals differing by 100. The operation of this embodiment is similar to the embodiment shown in  FIG. 1 . The valve  112   a  includes a closed center valve portion  112   b . However, the main operating difference is the use of a pressure reducing and regulating valve  128 . The regulating valve  128  creates a fixed input pressure for the solenoid valve  118  in that the pressure, which in  FIG. 1  was taken from the discharge port of the pump  10  into the solenoid control valve  18 , is now at a constant pressure and, therefore, provides better control of the variable target pressure acting on piston  120 . This ultimately provides improved control over the desired movement of the eccentric ring  111  of the pump  110 .  
         [0022]      FIG. 2   a  operates in a similar manner as  FIG. 2 . The main difference between  FIG. 2  and  FIG. 2   a  is that the pressure reducing and regulating valve  128  of  FIG. 2   a  creates a fixed target pressure that acts directly on the piston  120 . The solenoid  126  opens or closes to further adjust the pressure of fluid acting on the piston  120 . When the solenoid  126  moves the valve  118   a  to the closed position there is an increase in variable target pressure. When the solenoid  126  moves the valve  118   a  to the open position the variable target pressure will decrease as the fluid moves to the sump with less resistance. Additionally, unreduced pressure is fed to the spool valve  112 A before pressure the pressure reducing and regulating valve  128  after the filter. Just as in  FIG. 2 , this embodiment is also a passive system for controlling oil flow and oil pressure since an engine control unit  124  controls the solenoid  126  for positioning the piston  120 , however, the engine control unit  124  does not directly sense oil pressure.  
         [0023]     With respect to  FIG. 3 , like items referenced in  FIG. 2  are similarly designated with reference numerals differing by 100. In  FIG. 3 , the source for the pressure which is regulated by the valve  218  is taken from the pilot line instead of the discharge line. Otherwise, the control operation is similar to that shown in  FIGS. 1 and 2 .  
         [0024]     With respect to  FIG. 4 , like items referenced in  FIG. 3  are similarly designated with reference numerals differing by 100. In this particular embodiment the solenoid  326  directly controls the movement of the variable target piston  320 . The engine control unit  324  is connected to the solenoid  326  and controls the actuation of the solenoid. The configuration of this embodiment (i.e., the solenoid acting directly on the variable target piston  320 ) allows the variable target piston to be adjusted in accordance with the engine control unit&#39;s  324  commands directly, rather than using additional hydraulics.  
         [0025]     With respect to  FIG. 5 , like items referenced in  FIG. 4  are similarly designated with reference numerals differing by 100. With respect to  FIG. 5 , this embodiment includes a solenoid  426  attached to the flow control spool valve  412  directly, to regulate the stroke or de-stroke conditions of the pump  410 . The solenoid  426  is connected directly to the engine control unit  424 . The engine control unit  424  samples the pilot pressure from a pressure transducer in the engine circuit in order to make the proper calculations as to the best spool position based on the current actual and target pressures. Return spring  416  provides the return pressure for adjusting the flow control spool valve  412  in absence of solenoid  426  input, and allows for predetermined functions of spool position versus current.  
         [0026]     With respect to  FIG. 6 , like items referenced in  FIG. 5  are similarly designated with reference numerals differing by 100. With respect to  FIG. 6 , a very simple control mechanism is used by the control solenoid  526  moving a valve  512 A for controlling the de-stroke actuator of the pump  510 . The solenoid  526  adjusts the pressure acting on the large piston which pushes against the discharge pressure acting on the small piston on the opposite side. An on-stroke return spring is provided for balancing the eccentric control ring against control inputs which can also work alone (as shown). In this embodiment, the engine control unit  524  samples the pilot pressure from a pressure transducer in the engine circuit in order to make the proper calculations as to the best valve  512 A position.  
         [0027]     With respect to  FIG. 7 , like items referenced in  FIG. 6  are similarly designated with reference numerals differing by 100.  FIG. 7  is another embodiment wherein engine control unit  624  directly controls a solenoid  626  which acts directly on either the actuating piston for the eccentric ring or directly on the eccentric ring. This allows direct control of the displacement of the pump  610  based on ECU  624  monitoring of the pilot pressure of the oil pressure circuit.  
         [0028]      FIG. 8  illustrates a further embodiment wherein the solenoid  726  directly actuates the spool flow control valve  712 . Again, the ECU  724  is monitoring the engine oil circuit pressure and adjusting the solenoid in accordance with the necessary engine oil pressure, as calculated by the ECU. In this embodiment, pressure from the discharge is reduced by the solenoid valve and used to bias the position of the flow control spool valve  712  against the spring for varying the displacement of the pump. Flow across the solenoid can be directed to the inlet port, as shown of the vane pump  710 , but can also be drained to the sump.  
         [0029]     As can be seen by the drawings, the methods shown in  FIGS. 1 through 4  are passive systems which allow the ECU to monitor engine conditions and provide a pressure target to the pump system, but the pump system is self-regulated to the pressure target by mechanical and hydraulic controls.  FIGS. 5 through 8  provide active control of the oil pressure by the ECU. In these embodiments, the ECU monitors the oil pressure and actively adjusts the system on a real time basis to control oil pressure in the engine.  
         [0030]     Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited, since other modifications will become apparent to the skilled practitioner upon a study of the drawings, specification and following claims.  
         [0031]     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the scope of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.