Abstract:
This invention provides both a pump and a lubrication and cooling system with a pump which includes a pump housing, a rotor, a relief valve and a bypass valve. The relief valve is configured to relieve pump pressure when the pump pressure is indicative of an abnormal restriction of flow. The bypass valve is configured to direct fluid flow from an outlet chamber of the pump to an intake chamber of the pump when pressure in the outlet chamber is at a value associated with a predetermined speed of rotor rotation.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation application of U.S. application Ser. No. 13/232,959 filed Sep. 14, 2011, which claims the benefit of U.S. Provisional Application No. 61/382,603, filed Sep. 14, 2010, which is hereby incorporated by reference in their entireties. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    It is desired to provide a lubrication and cooling system for a transmission and a pump for use in such a system which responds to fluid flow restrictions that might occur in a cooler or in a filter. It is also desired to provide such a system for a transmission and a pump which reduces the opportunity for pump cavitation at elevated pump speeds. 
       SUMMARY OF THE INVENTION 
       [0003]    This invention provides both a pump and a lubrication and cooling system with a pump which includes a pump housing, a rotor, a relief valve and a bypass valve. The relief valve is configured to relieve pump pressure when the pump pressure is indicative of an abnormal restriction of flow. The bypass valve is configured to direct fluid flow from an outlet chamber of the pump to an intake chamber of the pump when pressure in the outlet chamber is at a value associated with a predetermined speed of rotor rotation. 
         [0004]    This invention also overcomes the pump cavitation at elevated speeds by directing unneeded fluid flow directly from the outlet chamber to an intake chamber by way of the bypass valve. Flow of fluid to the lubrication system is maintained in the event of a restriction in either a cooler or a filter by way of the relief valve. 
     
    
     
       DESCRIPTION OF DRAWINGS 
         [0005]      FIG. 1  is a schematic view of a transmission lubrication and cooling system including a pump. 
           [0006]      FIG. 2  is a perspective view of the pump of  FIG. 1 . 
           [0007]      FIG. 3  is a perspective view of a housing of the pump of  FIG. 2 . 
           [0008]      FIG. 4  is a perspective view of a cover plate of the pump of  FIG. 2 . 
           [0009]      FIG. 5  is a perspective view of a rotor of the pump of  FIG. 2 . 
           [0010]      FIG. 6  is a perspective view of a pump idler of  FIG. 2 . 
           [0011]      FIG. 7  is a top view of the pump of  FIG. 2 . 
           [0012]      FIG. 8  is a rear view of the pump of  FIG. 2 . 
           [0013]      FIG. 9  is a rear view of the pump of  FIG. 8  with the cover plate removed. 
           [0014]      FIG. 10  is a sectional view of the pump of  FIG. 8  in the direction of arrows  10 . 
           [0015]      FIG. 11  is a sectional view of the pump of  FIG. 7  in the direction of arrows  11 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    The terms top, bottom, and other directional terms such as front, rear, upper and lower are only used to provide the relative orientation of surfaces and features of the components and system, and are not indicative of the absolute position or orientation of any component or feature. 
         [0017]      FIG. 1  shows a transmission lubrication and cooling system  20  including a lubrication and cooling circuit  22 , a pump  24  and a sump  26 . A suction channel  28  is disposed between and fluidly connects sump  26  and pump  24 . A cooler  30  and a filter  32  are fluidly connected to pump  24  by cooling and filter channel  34 . A lubrication channel  36  is connected to cooling and filter channel  34 . Lubrication channel  36  serves as a conduit of fluid to lubrication system  38 . An optional return channel  40  may be used to return fluid to sump  26 . 
         [0018]    Pump  24  includes a relief valve  42  and a bypass valve  44 . Both valves  42  and  44  are incorporated into a housing  46  of pump  24 . A cover plate  48  is disposed on a rear or back side of pump housing  46 . Cover plate  48  defines outlet port  50 . 
         [0019]    A suction port  52  of pump  24  is connected to sump  26  by suction channel  28 . The illustrated pump is a gerotor style pump, and includes a pump rotor or inner rotor  54  and a pump idler or outer rotor  56 , both of which are disposed inside of pump housing  46 . As suggested by the figures which variously show rotor  54  having four lobes and idler  56  having five teeth, and rotor  54  having five lobes and idler  56  having six teeth, the invention is not intended to be limited to pumps having a particular count of meshing features. A pump shaft  58  is rotatably fixed to pump rotor  54  by a key (not shown) or equivalent means. Pump shaft  58  rotates about an axis of rotation  60  normal to the pump rotor  54 . A drive gear  62  is disposed outside of housing  46  and is rotatably fixed to shaft  58  by a key or equivalent means. Drive gear  62  is an exemplary means by which torque and speed is transferred to shaft  58  and rotor  54 . The illustrated drive means is not intended to be limiting. 
         [0020]    Housing  46  includes a rotor chamber  64  in which each of rotor  54  and idler  56  are disposed. Other features of housing  46  include an intake chamber  66  which connects directly to suction port  52  and a pump inlet chamber  68  which is fluidly connected with and open to rotor chamber  64 . Additionally, an outlet chamber  70  is fluidly connected with both rotor chamber  64  and outlet port  50 . 
         [0021]    As best seen in  FIG. 11 , relief valve  42  is operably disposed between an outlet chamber  70  and a relief port  72 . A plurality of ports  72  may be provided. Valve  42  is configured to open to operably fluidly connect outlet chamber  70  with relief port  72 . In the embodiment illustrated, a relief valve plug  74  is disposed in housing  46  to retain relief valve bias spring  76 . Spring  76  biases relief valve check ball  78  against relief valve ball seat  80 . A relief channel  82  fluidly connects relief port  72  with lubrication channel  36 . 
         [0022]    Bypass valve  44  is operably disposed between outlet chamber  70  and intake chamber  66 . Valve  44  is fluidly connected to intake chamber  66  by a bypass channel  84 . A bypass passage  86  fluidly connects valve  44  with outlet chamber  70 . Valve  44  is configured to open to operably fluidly connect outlet chamber  70  with intake chamber  66 . In the embodiment illustrated, a bypass valve plug  88  is disposed in housing  46  to retain bypass valve bias spring  90 . Spring  90  biases bypass valve check ball  92  against bypass valve ball seat  94 . Passage  86  defines a restrictive orifice through which fluid reaching valve  44  must pass. A travel limit pin  96  may electively be configured to limit the displacement of check ball  92  from seat  94  is disposed in housing  46 . Pin  96  may be formed as part of plug  88 , or may be a separate component. 
         [0023]    A description of the invention operation follows. Pump  24  relies on a conventional gerotor arrangement to draw and pressurize its operating fluid. The operation of such pumps is well known and illustrated in references such as U.S. Pat. No. 4,041,703. In a first condition, at relatively low rotational speeds of shaft  58  and rotor  54 , with no abnormal restrictions in cooling and filtering channel  34 , each of relief valve  42  and bypass valve  44  are in a closed condition, with all of the fluid displaced by the rotation of rotor  54  being drawn from sump  26  through suction channel  28  and passing through outlet port  50 , through cooler  30  and filter  32  and lubrication system  38 . Examples of conditions constituting an abnormal restriction include a plugged or partially plugged cooler  30 , and a plugged or partially plugged filter  32 . An abnormal restriction might also result from high fluid viscosity at start-up due to a low ambient temperature. 
         [0024]    In a second condition, at a first pressure within outlet chamber  70  corresponding to a predetermined speed of rotor  54 , bypass valve  44  opens to allow operating fluid to flow from outlet chamber  70  to intake chamber  66  where it joins fluid being drawn up from sump  26  through channel  28 . The quantity of fluid reaching intake chamber beneficially helps avoid cavitation of the pump. While alternative solutions might include increasing the sizing of the suction channel and optimizing the location of the pump relative to the sump, the present invention enables greater flexibility in the location of the pump. The restriction provided by the orifice sizing of passage  86  reduces the rate of flow to the intake chamber. The combination of spring selection and orifice sizing enable one skilled in the art to provide a pressure and flow combination suited for the application at hand. Intake chamber  66  has a greater cross sectional area in the flow direction than suction channel  28 , accommodating the additional volumetric flow past bypass valve  44  and facilitating an increased volumetric flow into adjoining inlet chamber  66  which feeds operating fluid to rotating rotor  54 . All of the pressurized operating fluid in outlet provided by the rotation of rotor  54 , excepting that which travels past valve  44 , exits through outlet port  50  and passes through cooler  30 , filter  32  and lubrication system  38 . An exemplary range of pressure at which valve  44  opens is 67 pounds per square inch (psi) to 71 psi. 
         [0025]    In a third condition, as the operating fluid within outlet chamber  70  reaches a second pressure indicative of an abnormal restriction of flow in cooling and filtering channel  34 , relief valve  42  opens to allow operating fluid to flow from outlet chamber  70  to lubrication system  38  via relief channel  82 . Routing the flow from the relief valve to the lubrication system instead of directly to the sump enables system  20  to maintain the flow of operating fluid critical lubrication of the transmission, thereby avoiding damage to the transmission. As in the second condition, operating fluid flows past bypass valve  44 . The amount of fluid, if any, passing through cooler  30  and filter  32  will depend on the extent of blockage. An exemplary range of pressure at which valve  42  opens is 114 psi to 142 psi. The appropriate range of pressures for any particular application of the inventive system will vary with that application. Factors influencing pressure ranges for both the bypass and relief valves include, but are not limited to, the viscosity of the operating fluid, the anticipated operating temperatures, and the anticipated back pressure of the system under normal operating conditions. 
         [0026]    The scope of the invention is set forth in the claims below.