Patent Publication Number: US-2013251570-A1

Title: Variable Displacement Variable Pressure Vane Pump System

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/161388, filed on Jul. 18, 2008, which is a National Phase of PCT/CA2007/000118, filed Jan. 31, 2007, which claims the benefit of U.S. Provisional Application No. 60/763720, filed Jan. 31, 2006. The entire disclosures of each of the above applications are incorporated herein by reference. 
    
    
     FIELD 
     The present invention relates to variable displacement vane pumps. More specifically, the present invention relates to a variable displacement variable pressure vane pump system for mechanical systems such as internal combustion engines or automatic transmissions. 
     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 mechanical linkage to the mechanical system and thus the operating speed, and output, of the pump varies with the operating speed of the mechanical system. While the lubrication requirements of the mechanical system also vary with the operating speed of the mechanical system, unfortunately the variation in the output of the pump and the variation of the lubrication requirements of the mechanical system are generally nonlinear. The difference in these requirements is further exacerbated when temperature related variations in the viscosity and other characteristics of the lubricating oil are factored in. 
     To deal with these differences, prior art fixed displacement lubricating pumps were generally designed to operate effectively at high, or maximum, oil temperatures, resulting in an oversupply of lubricating oil at most mechanical system operating conditions and a waste, or pressure relief, valve was provided to “waste” 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&#39;s needs so, while such systems work reasonably well, they do result in a significant energy loss as energy is used to pressurize the unneeded lubricating oil which is “wasted” 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 moved to alter the displacement of the pump and thus its output at an operating speed. Typically, a feedback mechanism, in the form of a piston or control chamber supplied with pressurized lubricating oil from the output of the pump, either directly or via an oil gallery in the mechanical system, alters the displacement of the pump to avoid over pressure situations in the engine over the expected range of operating conditions of the mechanical system. An example of such a pump is shown in U.S. Pat. No. 4,342,545 to Schuster. 
     While such variable displacement pumps provide some improvements in energy efficiency over fixed displacement pumps, they still result in a significant energy loss as they must still be designed to provide oil pressures which meet the highest expected mechanical system requirements and operating temperatures, even when the mechanical system operating conditions normally do not necessitate such high requirements. 
     SUMMARY 
     It is an object of the present invention to provide a novel variable displacement variable pressure vane pump which obviates or mitigates at least one disadvantage of the prior art. 
     According to a first aspect of the present invention, there is provided a variable displacement variable pressure vane pump system for providing lubrication oil to a mechanical system comprises: a variable displacement variable pressure vane pump having a control slider which is moveable to alter the displacement of the pump; a biasing means to bias the control slider towards a position corresponding to the maximum displacement position of the pump; a first control mechanism responsive to the pressure of the lubrication oil output from the pump to apply a force to the control slider to counter the biasing force of the biasing means and to urge the control slider away from the position corresponding to the maximum displacement position of the pump; a second control mechanism responsive to the pressure of the lubrication oil output from the pump to apply a force to the control slider to counter the biasing force of the biasing means and to urge the control slider away from the position corresponding to the maximum displacement position of the pump; and a control means operable to vary the lubrication oil supplied to the second control mechanism to alter the output of the pump to more closely correspond to the lubrication requirements of the mechanical system. 
     The present invention provides a variable displacement variable pressure vane pump system for providing lubrication oil to mechanical systems such as internal combustion engines and/or automatic transmissions. The system includes at least a first control mechanism, which can be a control chamber directly acting on the control slider or a control chamber and control cylinder which acts on the control slider and a second control mechanism which is a control chamber and control cylinder which acts on the control slider. A control valve, operated by an engine control unit or other suitable control mechanism, can selectively vary pressurized lubrication oil to the second control mechanism to allow the output of the pump system to more closely match the requirements of the mechanical system. In one embodiment, the control mechanism merely applies or removes pressurized lubrication oil and in another embodiment, the control mechanism can control the pressure of the pressurized lubrication oil provided to the second control mechanism. In another embodiment a third control mechanism, which is a control chamber and control cylinder which acts on the control slider, is provided to provide finer granularity in controlling the output of the pump system to more closely correspond to the lubrication requirements of the engine. In yet another embodiment, both the first and second control mechanisms are control chambers and control cylinders which act on the control slider. 
    
    
     
       DRAWINGS 
       Preferred embodiments of the present invention will now be described, by way of example only, with reference to the attached Figures, wherein: 
         FIG. 1  shows an example of a plot of the oil pressure demand of a mechanical system versus the output of a prior art lubricating pump; 
         FIG. 2  shows a hydraulic circuit of a variable displacement variable pressure vane pump system in accordance with the present invention with the pump system in a lower speed, higher displacement and low pressure state; 
         FIG. 3  shows the pump system of  FIG. 2  in a lower speed, low displacement and low pressure state; 
         FIG. 4  shows the pump system of  FIG. 2  in a higher speed, high displacement and high pressure state; 
         FIG. 5  shows the pump system of  FIG. 2  in a higher speed, low displacement and high pressure state; 
         FIG. 6  shows an example plot of oil pressure demand of a mechanical system versus the output of the pump system of  FIGS. 2 through 5 ; 
         FIG. 7  shows a hydraulic circuit of another variable displacement variable pressure vane pump system in accordance with the present invention wherein the output of the pump is directly fed to the control devices; 
         FIG. 8  shows another hydraulic circuit for the pump system of  FIGS. 2 through 5 ; 
         FIG. 9  shows a hydraulic circuit of another embodiment of a variable displacement variable pressure vane pump system in accordance with the present invention with the pump system in a high displacement state; 
         FIG. 10  shows a plot of oil pressure demand of a mechanical system versus the output of the pump system of  FIG. 9 ; 
         FIG. 11  shows a hydraulic circuit of another embodiment of a variable displacement variable pressure vane pump system in accordance with the present invention with the pump system in a lower speed, high displacement and lower pressure state; 
         FIG. 12  shows a hydraulic circuit of another embodiment of a variable displacement variable pressure vane pump system in accordance with the present invention with the pump system in a high displacement state; and 
         FIG. 13  shows a hydraulic circuit of another embodiment of a variable displacement variable pressure vane pump system in accordance with the present invention with the pump system in a high displacement state. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a typical plot of the lubricating oil pressure requirement (shown in solid line) of a mechanical system, such as a typical internal combustion engine, versus the output (shown in dashed line) of a prior art variable displacement pump, such as the pump taught in the above-mentioned Schuster patent. The corner on the output (dashed line) results from the movement of the control slide by the control piston to reduce the displacement of the pump as the output of the pump reaches a preset value. The shaded area between the engine demand curve and the pump output curve represents the engine operating conditions wherein energy is lost as the pump pressure output exceeds engine demand. 
     A lubrication pump system in accordance with the present invention is indicated generally at  20  in  FIG. 2 . While in the following discussion the lubrication needs of an internal combustion engine are discussed, the present invention is not so limited and the present invention can be advantageously employed with a variety of mechanical systems including internal combustion engines, automatic transmission systems, etc. 
     System  20  includes a Variable Displacement Vane Pump (VDVP)  24 , which can be any suitable VDVP, such as one similar to that taught in the above-mentioned U.S. Patent to Schuster. VDVP  24  includes a rotor  28 , which is driven by the internal combustion engine on which pump system  20  is installed. Rotor  28  includes a set of radially extending vanes  32  which engage the inner surface of a control slider  36  which can be moved about a pivot point  38  to alter the eccentricity between the rotor and vanes and the inner surface of control slider  36 , thus altering the displacement of VDVP  24 . 
     VDVP includes a biasing spring  40  which biases control slider  36  to the maximum displacement position and a control piston  44  is provided to, under certain conditions, move control slider  36 , against the bias of biasing spring  40 , towards the minimum displacement position. 
     VDVP  24  includes an inlet  48  which is in fluid communication with a source  52  of lubricating oil, such as the sump of an engine and an outlet  56  which supplies pressurized lubricating oil to the engine, normally through an oil filter  60 . In the case of clean oil actuation, where the oil has passed through filter  60 , pump outlet  56  is connected to an overpressure relief valve  64  which opens to return some lubricating oil to source  52  if the output pressure of VDVP  24  exceeds a pre-selected pressure in order to protect oil filter  60 . If the actuation is performed with unfiltered oil, directly from pump outlet  56 , the circuit feedback is direct, as described below with respect to the embodiment of  FIG. 7 , allowing the omission of overpressure relief valve  64 . 
     As shown, chamber  68  at one end of control piston  44  is in fluid communication with the pressurized lubricating oil supplied to the engine and the force developed on control piston  44  in chamber  68 , which increases with the pressure of the lubricating oil, moves control slide  36  against biasing spring  40  to reduce the displacement of VDVP  24  and hence reduce the output flow. 
     As will be apparent to those of skill in the art, the components of system  20  described so far, and in particular biasing spring  40  and control piston  44 , are conventional and would result in VDVP  24  operating in much the same manner as illustrated in the plot of  FIG. 1 . 
     However, unlike conventional lubricating pumps (like the pump taught in Schuster) and conventional pump systems, VDVP  24  further includes a control chamber  72  formed between the interior wall of the pump housing of VDVP  24 , pivot point  38 , slider seal  74  and the outer surface of control slider  36  on the same side of pivot point  38  as control piston  44 . Control chamber  72  is in fluid communication with a control valve  76  which is, in turn, in fluid communication with a source of pressurized lubricating oil from an engine gallery, oil line or any other suitable source of pressurized lubricating oil supplied from VDVP  24  and which has a return line  78  to source  52  to relieve pressure in control chamber  72  when control valve  76  is in the appropriate position. 
     Volume  80 , formed between the interior wall of the housing of VDVP  24 , pivot point  38 , slider seal  74  and the outer surface of control slider  36  on the same side of pivot point  38  as biasing spring  40 , is substantially sealed from the pressurized lubricating oil and is in fluid communication with source  52  and is thus maintained at, or close to, atmospheric pressure. 
     As should now be apparent to those of skill in the art, when control chamber  72  is supplied with pressurized lubricating oil, a force is developed by this lubricating oil on control slider  36 . The force developed by chamber  72  adds to the force developed by control piston  44  and the resulting sum of these forces acts against the biasing force of biasing spring  40 , moving control slider  36  to reduce the displacement of VDVP  24  to a greater extent than would be the case if just the force of control piston  44  was applied. 
     Preferably, the projected area of control chamber  72  (i.e.—the area of control chamber  72  over which the pressure of the lubrication oil generates a force on control slider  36 ) is much larger than the projected area of control piston  44 . Thus, at lower operating speeds, control chamber  72  will generate larger forces on control slider  36 , to counter the biasing force of biasing spring  40 , than the forces that are developed by control piston  44 . This arrangement allows a reduced size of VDVP  24 , biasing spring  40  and control piston  44  thus reducing the weight and cost of VDVP  24 . 
     Control valve  76  can selectively apply or remove pressurized fluid in response to any suitable control mechanism. In the illustrated embodiment, control valve  76  is controlled via a solenoid which is electrically actuated by a signal from the engine controller unit (ECU) which knows the engine operating speed and, in many cases, will also know at least some measure of the load on or temperature of the engine, and will actuate control valve  76  to decrease or increase the displacement of VDVP  24  as necessary to provide the designed oil pressure at different engine operating conditions. 
     System  20  is not limited to control valve  76  being controlled by the ECU, nor to control valve  76  being electrically controllable, although both of these are presently preferred, and control valve  76  can be operated by any suitable means as will occur to those of skill in the art. 
     As should now be apparent, in  FIG. 2  system  20  is illustrated in a lower speed range, maximum displacement configuration wherein the force developed, due to oil pressure output from VDVP  24 , in chamber  68  and in control chamber  72  act to move control slider  36  from the maximum displacement position and, due to the operating speed of VDVP  24 , this force is insufficient to counter the biasing force of biasing spring  40 . 
       FIG. 3  shows system  20  in a low speed range, minimum displacement configuration. As illustrated, despite the relatively low speed (but higher speed than that of the configuration of  FIG. 2 ) at which VDVP  24  is operating, control slider  36  has been moved against the biasing force of biasing spring  40  by the combined forces generated in chambers  68  and chamber  72 . 
       FIG. 4  shows system  20  in a high speed range, maximum displacement configuration. As illustrated, control valve  76  has been moved to disconnect the pressurized lubricating oil from control chamber  72  and to allow the pressure of the lubricating oil in control chamber  72  to return to source  52  through return line  78 . Thus, control piston  44  exerts the only substantial force on control slider  36  to counter the biasing force of biasing spring  40  and this force is insufficient to counter the biasing force of biasing spring  40 . 
       FIG. 5  shows system  20  in a high speed, minimum displacement configuration wherein control valve  76  is in the same position as in  FIG. 4 , removing the pressure from control chamber  72 . However, due to the relatively high operating speed of VDVP  24 , the pressure of the lubricating oil in chamber  68  develops sufficient force on control piston  44  to move control slider  36  to the illustrated minimum displacement position against the biasing force of biasing spring  40 . 
       FIG. 6  shows a plot, similar to that of  FIG. 1 , of the lubricating oil pressure requirement (shown in solid line) of a typical internal combustion engine versus the output (shown in dashed line) of an embodiment of system  20 . System  20  is in the: low speed, maximum displacement configuration of  FIG. 2  in the region of the plot indicated by reference numeral  90 ; low speed, reduced displacement configuration similar to that of  FIG. 3  in the region of the plot indicated by reference numeral  94 ; high speed, higher displacement configuration similar to that of  FIG. 4  in the region of the plot indicated by reference numeral  96 ; and high speed, reduced displacement configuration similar to that of  FIG. 5  in the region of the plot indicated by reference numeral  100 . 
     As is apparent, the shaded area between the engine demand curve and the output curve of system  20 , wherein energy is lost as the output of system  20  exceeds engine demand, is much smaller than the comparable region of  FIG. 1 . 
     While in the embodiments of system  20  illustrated above control chamber  72  and chamber  68  are supplied with pressurized “clean” lubrication oil downstream of oil filter  60 , it will be apparent to those of skill in the art that the present invention is not so limited and either or both of control chamber  72  and chamber  68  can be supplied with pressurized lubricating oil from a point prior to oil filter  60 , as illustrated in  FIG. 7  wherein like components to those of  FIGS. 2 through 5  are indicated with like reference numerals. 
     As illustrated in  FIG. 8 , wherein like components to those of  FIGS. 2 through 5  are indicated with like reference numerals, the present invention is not limited to control valve  76  being in fluid communication with control chamber  72  and chamber  68  being in fluid communication with a supply of pressurized lubricating oil. Instead, as illustrated in  FIG. 8 , control valve  76  can be used to control the supply of pressurized lubricating oil to chamber  68  while control chamber  72  is directly connected to a supply of pressurized lubricating oil. 
     It is further contemplated that, for any of the configurations of  FIGS. 2 through 5  and  FIG. 7  or  8  control valve  76  can be a variable orifice valve which can control the pressure of the lubrication oil supplied to control chamber  72 , rather than just connect chamber  72  to the lubrication oil pressurized by VDVP  24  or return line  78 . In this manner, a pump output characteristic can be obtained, under proper control by the ECU or other suitable control means, which very closely corresponds to the requirements of the engine rather than just two distinct pressure settings. 
     Another embodiment of a lubrication pump system in accordance with the present invention is indicated generally at  200  in  FIG. 9 , wherein like components to those of system  20  are indicated with like reference numerals. In system  200 , VDVP  204  includes a pair of control cylinders  208  and  212 , preferably of different diameters and thus having different areas, each of which has a respective chamber  216  and  220  which can be connected to a supply of pressurized lubrication oil by a two port control valve  224  while control chamber  72  is in direct fluid communication with the pressurized lubrication oil pressurized by VDVP  204 . In the illustrated embodiment, control piston  208  has a larger cross sectional area than control piston  212 , thus producing a greater force for a given pressure of pressurized lubrication oil. This allows for a finer granularity of control of the output of VDVP  204 . 
     Control valve  224  can be operated by the ECU, or any other suitable control means, to supply neither or either of chambers  216  and  220  with pressurized lubrication oil and/or to connect either or both chambers  216  and  220  to source  52 , via return line  78 . If neither of chambers  216  or  220  are supplied with pressurized lubrication oil, the force created by the pressurized lubrication oil in control chamber  72  is the only force acting on control slider  36  against the biasing force of biasing spring  44 . If one of chambers  216  and  220  is supplied with pressurized lubrication oil, then the forced developed on the respective one of control cylinders  208  and  212  adds to the force developed by control chamber  72 . As will now be apparent, system  200  allows the output characteristic of VDVP  204  to more closely match the requirements of the engine. 
     While the embodiment of  FIG. 9  shows only one configuration for a VDVP system  200  with three selectable pressures and, as should now be apparent to those of skill in the art, different configurations and or/types of valve  224  can be employed to accommodate different VDVP output requirements. 
       FIG. 10  shows a plot, similar to that of  FIG. 1 , of the lubricating oil pressure requirement (shown in solid line) of a typical internal combustion engine versus the output (shown in dashed line) of system  200 . When the engine is at low speeds, control valve  224  is opened so that the larger chamber  216  is supplied with pressurized lubrication oil and thus each of control chamber  72  and control cylinder  208  can apply force to control slider  36 . 
     The transition point labeled “A” in the plot corresponds to the pressure of the lubrication oil output by VDVP  204  reaching the point wherein the sum of the resulting forces from control chamber  72  and control cylinder  208  is sufficient to begin moving control slider  36  against the biasing force of biasing spring  44 . 
     The transition point labeled “B” in the plot corresponds to control valve  224  removing the supply of pressurized lubrication oil from chamber  216  and adding the supply of oil to control chamber  220  thus control chamber  72  and control cylinder  212  then apply force to control slider  36 . 
     The transition point labeled “C” in the plot corresponds to control valve  224  also removing the supply of pressurized lubrication oil from chamber  220  and thus only control chamber  72  then applies force to control slider  36 . 
     As is apparent, the shaded area between the engine demand curve and the output curve of system  200 , wherein energy is lost as the output of system  200  exceeds engine demand, is much smaller than the comparable regions of  FIGS. 1 and 6 . 
     Another embodiment of a lubrication pump system in accordance with the present invention is indicated generally at  300  in  FIG. 11  wherein like components to those of system  20  and/or system  200  are indicated with like reference numerals. In system  300 , VDVP  304  is not equipped with a control chamber  72  and, instead, volume  304  is maintained at substantially atmospheric pressure, similar to volume  80  as there is no slide seal in this embodiment. However, chamber  224  is connected directly to a supply of pressurized lubrication oil and, along with control cylinder  208 , provides force to control slider  36  in the manner of control cylinder  44  of  FIGS. 2 through 5  or in the manner of control chamber  72  of  FIG. 7 . Chamber  220  is connected to control valve  76  and, when connected by control valve  76  to a source of pressurized lubricating oil, applies force to control slider  36  via control cylinder  212 . 
     Another embodiment of a lubrication pump system in accordance with the present invention is indicated generally at  400  in  FIG. 12 , wherein like components to those of system  20  are indicated with like reference numerals. In system  400 , VDVP  404  includes a double acting control cylinder  408  and a first control chamber  412  and a second control chamber  416 . Second control chamber  412  has a smaller projected area on control cylinder  408  than does control chamber  416 . 
     Control chamber  416  is connected directly to a supply of pressurized lubrication oil while control chamber  412  can be connected to the same supply of pressurized lubrication oil via control valve  420 . As shown in the Figure, control valve  420  is operable to either connect control chamber  412  to the above-mentioned supply of pressurized lubrication oil or to connect chamber  412  to source  52 , to allow pressurized lubrication oil to leave control chamber  412  and return to source  52 . 
     As will now be apparent, pressurized lubrication oil in control chamber  416  generates a force on control cylinder  408  which acts against biasing spring  40  to move control slide  36  to decrease the displacement of VDVP  404 . However, when control valve  420  allows pressurized lubrication oil to enter control chamber  412 , the force developed on control cylinder  408  in control chamber  412  adds to the force of biasing spring  40  to oppose the force generated in control chamber  416  on control cylinder  408 . By appropriately operating control valve  420 , the output of VDVP  404  can be more closely matched to the requirements of the engine. 
     Another embodiment of a lubrication pump system in accordance with the present invention is indicated generally at  500  in  FIG. 13 , wherein like components to those of system  20  are indicated with like reference numerals. In system  500 , VDVP  504  includes a control cylinder  508  and a first control chamber  512  and a second control chamber  516 . Second control chamber  516  is directly connected to a supply of pressurized lubrication oil while control chamber  72  and first control chamber  512  can selectively be connected to the supply of pressurized lubrication oil or to a return line to source  52  via control valve  520 . As illustrated, and unlike the embodiment of  FIG. 12  discussed above, the forces produced in first control chamber  512  and second control chamber  516  both act on control cylinder  508  to counter the force of biasing spring  40  on control slide  36  as does the force on control slide  36  produced in chamber  72 . 
     As will now be apparent, the output of system  500  can be adjusted between three states, allowing control of the output of system  500  with relatively fine granularity. Specifically, the three states are achieved by pressurizing: second control chamber  516 ; second control chamber  516  and chamber  72  (by moving control valve  520  to connect chamber  72  to the supply of pressurized lubricating oil); second control chamber  516  and first control chamber  512  (by moving control valve  520  to connect first control chamber  512  to the supply of pressurized lubricating oil). As the projected area of chamber  72  differs from the area of first control chamber  512 , and in the illustrated embodiment the projected area of chamber  72  is larger than the area of first control chamber  512 , the above described embodiment provides three stages of output for system  500 . 
     Further, in case of a failure of the control signals from the ECU, or control valve  520  itself, assumes a centered position wherein chamber  72  and first control chamber  512  are connected to source  52  by their respective return lines, ensuring that system  500  assumes its maximum displacement operating state as a failsafe configuration. As will be apparent to those of skill in the art, similar failsafe configurations can be provided for the other embodiments described above. 
     The present invention provides a variable displacement variable pressure vane pump system for providing lubrication oil to internal combustion engines. The system includes at least a first control mechanism, which can be a control chamber directly acting on the control slider or a control chamber and control cylinder which acts on the control slider and a second control mechanism which is a control chamber and control cylinder which acts on the control slider. A control valve, operated by the engine control unit or other suitable control mechanism, can selectively apply or remove pressurized lubrication oil to the second control mechanism to allow the output of the pump system to more closely match the requirements of the engine. In one embodiment, the control mechanism merely applies or removes pressurized lubrication oil and in another embodiment, the control mechanism can control the pressure of the pressurized lubrication oil provided to the second control mechanism. In another embodiment a third control mechanism, which is a control chamber and control cylinder which acts on the control slider, is provided to provide finer granularity in controlling the output of the pump system to more closely correspond to the lubrication requirements of the engine. In yet another embodiment, both the first and second control mechanisms are control chambers and control cylinders which act on the control slider. 
     While the embodiments illustrated above show scenarios wherein the ECU, or other means, is providing a simple control signal that has two or three conditions related to engine speed, it will be apparent to those of skill in the art, that the control signal provided can be related to other parameters such as: temperature; the use of piston cooling jets; or a combination of parameters programmed into the ECU or other control processor or device. In all those scenarios, the principle of varying the pump capacity as well as pump pressure output is the same as that described herein. 
     The above-described embodiments of the invention are intended to be examples of the present invention and alterations and modifications may be effected thereto, by those of skill in the art, without departing from the scope of the invention which is defined solely by the claims appended hereto.