Abstract:
A sliding vane pump includes a passageway that fluidly connects one or more pumping chambers to a side chamber. The passageway pressurizes the side chamber. This fluid pressure exerts a force that counteracts the force caused by pressure differences between the outlet pumping chambers and the inlet pumping chambers. At high speed, part of the side chamber is pressurized by the smallest volume outlet pumping chamber while another portion of the side chamber is pressurized by the largest volume outlet chamber. This results in a force counteracting an uncommanded displacement decrease of the pump.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure relates to the field of motor vehicle transmission pumps. More particularly, the disclosure pertains to a sliding pocket variable displacement vane pump. 
       BACKGROUND 
       [0002]    Many vehicles are used over a wide range of vehicle speeds, including both forward and reverse movement. Some types of engines, however, are capable of operating efficiently only within a narrow range of speeds. Consequently, transmissions capable of efficiently transmitting power at a variety of speed ratios are frequently employed. When the vehicle is at low speed, the transmission is usually operated at a high speed ratio such that it multiplies the engine torque for improved acceleration. At high vehicle speed, operating the transmission at a low speed ratio permits an engine speed associated with quiet, fuel efficient cruising. 
         [0003]      FIG. 1  illustrates a typical vehicle powertrain system  10 . Mechanical power flow connections are indicates with solid bold lines, the flow of hydraulic fluid is indicated with dashed lines, and the flow of electrical information signals is indicated with dotted lines. An internal combustion engine  12  drives a crankshaft  14  which supplies input power to transmission  16 . The transmission  16  adjusts the speed and torque and delivers the power to differential  18 . Differential  18  divides the power between left and rights wheels  20  and  22  while allowing slight speed differences as the vehicle turns a corner. 
         [0004]    Within transmission  16 , the speed and torque are adjusted by two components, torque converter  24  and gearbox  26 . Torque converter  24  includes an impeller and turbine that transmit power hydro-dynamically whenever the impeller rotates faster than the turbine. It may also include a stator that multiplies the torque. The torque converter may also include a bypass clutch that, when engaged, transmits power mechanically from the impeller to the turbine without the parasitic losses associated with hydro-dynamic power transfer. Gearbox  26  includes gearing and clutches arranged such that engaging various subsets of the clutches establish various power flow paths. The different power flow paths have different speed ratios. Gearbox  26  shifts from one speed ratio to another speed ratio by releasing some clutches and engaging other clutches to establish a different power flow path. 
         [0005]    Torque converter  24  and gearbox  26  are controlled by adjusting the pressure of hydraulic fluid supplied to various clutches. Pump  28  is driven by the transmission input which is driven by crankshaft  14 . Pump  28  draws fluid from sump  30  and supplies the fluid, at elevated pressure, to valve body  32 . The quantity of fluid supplies is based on engine speed and on a parameter of the pump geometry called pump displacement. In response to signals from controller  34 , valve body  32  supplies the fluid to the various clutches in torque converter  24  and gearbox  26  at controlled pressures less than the pressure supplied by pump  28 . The valve body also supplies fluid to the hydro-dynamic chamber of torque converter  24  and supplies fluid for lubrication to gearbox  26 . Fluid travels from gearbox  26  and valve body  32  back to the sump  30  to complete the cycle. The quantity of fluid needed varies depending on the current operating state of the transmission. In response to these changes and in response to changes in engine speed, controller  34  may also direct valve body  32  to adjust the pump displacement. 
       SUMMARY OF THE DISCLOSURE 
       [0006]    A sliding vane pump includes a fixed housing, a sliding housing configured to slide within the fixed housing, and a rotor. The fixed housing defines inlet and outlet ports. The sliding housing and fixed housing define a side chamber. The sliding housing defines a cylindrical chamber within which the rotor rotates. The rotor has a plurality of vanes configured to rotate with the rotor and to seal against a wall of the cylindrical chamber to define a plurality of pumping chambers. The side chamber is fluidly connected to a first pumping chamber such that fluid pressure in the side chamber exerts a first force on the sliding housing opposing a second force on the sliding housing due to differential fluid pressures among the pumping chambers. The first pumping chamber may be fluidly connected to the side chamber by a first passageway and fluidly connected to the outlet port by a second passageway separate from the first passageway. The first pumping chamber may have the least volume of any of the plurality of pumping chambers. The side chamber may also be fluidly connected to a second pumping chamber, which may have the largest volume of any of the plurality of pumping chambers. A spring may bias the sliding housing to a position relative to the fixed housing in which a pump displacement is a maximum. 
         [0007]    A pump includes a slider configured to slide within a housing and a rotor. The slider defines a cylindrical chamber. A plurality of vanes rotate with the rotor and seal against a wall of the cylindrical chamber to define a plurality of pumping chambers. The slider and the housing define a side chamber fluidly connected to a subset of the pumping chambers. The side chamber may be fluidly connected to the subset of pumping chambers by one or more passageways defined in the slider. 
         [0008]    A vane pump sliding housing includes opposing top and bottom surfaces, a cylindrical inner surface, and an outer surface. The outer surface configured to position the sliding housing within an outer housing in a first direction while permitting relative motion in a second direction. The sliding housing defines a first passageway connecting the cylindrical inner surface to the outer surface. The sliding housing may also define a second passageway connecting the cylindrical inner surface to the outer surface. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is schematic diagram of a vehicle powertrain. 
           [0010]      FIG. 2  is a cross section of a sliding pocket vane pump in a full displacement position. 
           [0011]      FIG. 3  is a cross section of a sliding pocket vane pump in a partial displacement position. 
           [0012]      FIG. 4  is a cross section of a sliding pocket vane pump with compensation grooves. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments can take various and alternative forms. The figures are not necessarily to scale; some features could be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations. 
         [0014]    A sliding pocket vane pump  28  is illustrated in  FIG. 2 . The pump includes a fixed outer housing  50  which may be integrated into a valve body housing. A sliding housing  52  fits within a chamber within outer housing  50 . A spring  54  biases the sliding housing toward the full displacement position shown in  FIG. 2 . The sliding housing defines a circular interior chamber. A rotor  56  rotates within the circular chamber about an axis that is fixed with respect to the outer housing  50 . A number of vanes  58  rotate with rotor  56  such that the tips of each rotor follow an inner surface  60  of the circular chamber of sliding housing  52 . The rotor, vanes, and sliding housing collectively define a number of pumping chambers  62 ,  64 ,  66 ,  68 ,  70 , and  72 . The volumes of chambers  62 ,  64 , and  66  increase as the rotor turns clockwise. An inlet port  74  is defined in the outer housing, extending above or below the plane of the cross section of  FIG. 2 , such that fluid is drawn from the inlet port into the expanding chambers. The volumes of chambers  68 ,  70 , and  72 , on the other hand, decrease as the rotor turns clockwise. An outlet port  76  is defined in the outer housing such that fluid is pushed into the outlet port as the chambers shrink. Fluid at controlled pressure is supplied to chambers  78 ,  80 ,  82 , and  84 . To command the pump to the full displacement position shown in  FIG. 2 , fluid at equal and low pressure is supplied to these chambers. 
         [0015]    When the demand for fluid is low and/or the engine speed is high, pump  28  is commanded to the low displacement condition illustrated in  FIG. 3  by supplying high pressure fluid to chamber  84 . Chambers  78 ,  80 , and  82  continue to be supplied with low pressure fluid, so there is a net hydraulic force pushing against spring  54 . In the condition shown in  FIG. 3 , the volumes of pumping chambers  62 ,  64 , and  66  continues to increase as rotor  56  turns clockwise, but by substantially less than in  FIG. 2 . Similarly, the volumes of pumping chambers  68 ,  70 , and  72  increases by substantially less than in  FIG. 2 . Consequently, the quantity of fluid draw from inlet  74  and pushed into outlet  76  per revolution of rotor  56  is substantially less. 
         [0016]    In addition to chambers  78 ,  80 ,  82 , and  84 , pumping chambers  62 ,  64 ,  66 ,  68 ,  70 , and  72  also exert force on sliding housing  52 . In order to push the fluid through downstream flow restrictions, the pressure in the outlet port  76  in higher than the pressure in inlet port  74 . At relatively low speed, the pressure in pumping chambers  62 ,  64 , and  66  is approximately equal to the pressure in inlet port  74  and the pressure in pumping chambers  68 ,  70 , and  72  is approximately equal to the pressure in outlet port  76 . These pressures produce a net force toward the left. This net force increases the frictional force between outer housing  50  and sliding housing  52 . This frictional force tends to make the sliding housing stay in the same position when commanded to change position, making the pump unresponsive to small displacement change commands. 
         [0017]    When the pump is rotating quickly, the pressures in chambers  68 ,  70 , and  72  are not equal. Due to entrained air in the fluid, the fluid has non-negligible compressibility. As the chamber moves through the position occupied by chamber  68  in  FIGS. 2 and 3 , the percentage change in volume per degree of rotation is small. Consequently, the pressure in the chamber in that position may be less than the pressure in outlet port  76 . On the other hand, the chamber in the position of chamber  72  has a large percentage decrease in volume per degree of rotation. Therefore, the pressure in higher than the pressure in outlet port  76 . This effect is particularly strong when the slider is in the full displacement position of  FIG. 2  and the air content of the fluid is high. The differential pressure between the chambers in these positions results in a net force biasing the sliding housing toward the low displacement position of  FIG. 3 . At high rotor speeds, this effect may overcome the force of spring  54  causing the displacement to decrease despite a full displacement command. If the controller had commanded full displacement in response to a high flow demand, the flow rate produced may fail to satisfy that demand. 
         [0018]      FIG. 4  illustrates a sliding vane pump designed to avoid the high speed control issues discussed above. Two grooves  92  and  94  have been added to the sliding housing  52 . Groove  92  connects the pumping chamber in the position of chamber  72  to the adjacent region of side chamber  82 . A side chamber is a chamber in the same plane as the rotor but on the outside of the sliding housing. Groove  94  connects the pumping chamber in the position of chamber  68  to the adjacent region of side chamber  82 . Unlike the pumps of  FIGS. 2 and 3 , side chamber  82  is not separately supplied with low pressure fluid from the valve body. Chambers  78  and  80  are continuously supplied with low pressure fluid. Chamber  84  is supplied with fluid at a pressure indicating the desired displacement. 
         [0019]    At all rotor speeds, the average pressure in side chamber  82  is approximately equal to the average pressure in chambers  68 ,  70 , and  72  such that no net side force is generated. Furthermore, at high rotor speed, the upper portion of side chamber  82  is at substantially higher pressure than the lower portion. Although some fluid will flow from the high pressure region to the low pressure region, the passage connecting these regions has sufficiently high flow resistance to maintain substantial pressure difference. The pressure gradient within side chamber  82  causes a net force on sliding housing  52  biasing it toward the full displacement position. This force counteracts the force produced by the differential pressures between chambers  68  and  72 . Consequently, the sliding housing stays in the full displacement position until commanded to move and then responds smoothly and proportionately to a command to decrease the displacement. In alternative embodiments, passageways  92  and/or  94  may be formed in outer housing  50  such that they pass under or over sliding housing  52 . 
         [0020]    While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes can be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments can be combined to form further embodiments of the invention that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics can be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. As such, embodiments described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and can be desirable for particular applications.