Abstract:
A self-priming vane pump includes a cylindrical rotor disposed in a cavity in a housing including inlet and outlet ports. The rotor defines a plurality of axially extending slots which each receive one of a like plurality of vanes. A garter spring or similar resilient annulus is disposed within the rotor and provides a radially outwardly directed force on the vanes which maintains their contact with the cavity walls during pump start-up and rapidly self-primes the pump. The spring or annulus rests against a shoulder within the hollow rotor and is retained therein by a pressed in collar.

Description:
FIELD 
       [0001]    The present disclosure relates to vane pumps and more particularly to a self-priming vane pump. 
       BACKGROUND 
       [0002]    The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art. 
         [0003]    Gear pumps and gerotor pumps are often the preferred choice for a fixed or positive displacement pump in applications requiring flows and pressures of low to medium nominal values. One drawback of such pumps, however, is their efficiency. Due to their construction, there is backflow or leakage through the meshing rotors and around the ends of the rotors when they are operating which results in reduced forward flow and thus reduced pumping efficiency. 
         [0004]    Fixed displacement vane pumps perform in the same flow and pressures ranges and exhibit improved efficiency due to reduced leakage and backflow. Such reduced leakage and backflow are the result of better sealing between the outer edges of the vanes and the walls of the rotor cavity. However, since contact between the pump vanes and pump cavity and thus the seal quality is primarily the result of centrifugal force and line pressure acting on the center of the rotor, both of which push the vanes outward to seal on the wall of the pump cavity, the seal quality improves with higher rotational speeds and higher line pressure and degrades with lower speeds and lower line pressure. This aspect of vane pump operation is especially problematic at startup of an unprimed pump. Since at startup, the pump will typically be operating at reduced speed and zero pressure, seal quality is low and this problem in exacerbated by the unprimed state of the pump such that establishment of priming and delivery of pressurized fluid may take an undesirably long period of time. 
         [0005]    The present invention provides a solution to the dual problems of startup of an unprimed vane pump. 
       SUMMARY 
       [0006]    The present invention provides a self-priming fixed displacement vane pump. The pump includes a hollow cylindrical rotor disposed in an elliptical cavity in a housing including inlet and outlet ports. The rotor defines a plurality of axially extending slots which each receive one of a like plurality of vanes. A garter spring or similar resilient annulus is disposed within the rotor and provides a radially outwardly directed force on the vanes which maintains their contact with the cavity walls during pump start-up and rapidly self-primes the pump. The spring or annulus rests against a shoulder within the hollow rotor and is retained therein by a pressed in collar. 
         [0007]    It is thus an object of the present invention to provide a self-priming vane pump. 
         [0008]    It is a further object of the present invention to provide a fixed displacement self-priming vane pump. 
         [0009]    It is a still further object of the present invention to provide a vane pump having a spring which urges the pump vanes into contact with the wall of the pump cavity. 
         [0010]    It is a still further object of the present invention to provide a vane pump having a garter spring disposed within the pump rotor which urges the pump vanes into contact with the wall of the pump cavity. 
         [0011]    It is a still further object of the present invention to provide a vane pump having a resilient annulus disposed within the pump rotor which urges the pump vanes into contact with the wall of the pump cavity. 
         [0012]    It is a still further object of the present invention to provide a self-priming vane pump having a spring disposed within the pump rotor and retained by a collar which urges the pump vanes into contact with the wall of the pump cavity. 
         [0013]    Further objects, advantages and areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0014]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0015]      FIG. 1  is a full sectional view of a self-priming vane pump according to the present invention disposed in an automatic transmission; 
           [0016]      FIG. 2  is an end view of a self-priming vane pump according to the present invention; 
           [0017]      FIG. 3  is a fragmentary, sectional view of a self-priming vane pump according to the present invention taken along line A-A of  FIG. 1 ; 
           [0018]      FIG. 4  is a fragmentary, sectional view of a self-priming vane pump according to the present invention taken along line B-B of  FIG. 1 ; and 
           [0019]      FIG. 5  is a plan view of a retaining collar of a self-priming vane pump according to the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
         [0021]    With reference to  FIG. 1 , a portion of an automatic transmission incorporating the present invention is illustrated and generally designated by the reference number  10 . The automatic transmission  10  includes a housing  12 , a portion of which is illustrated in  FIG. 1 . The housing  12  encases and protects various components of the automatic transmission  10  such as a vane pump housing  14  and a drive shaft  16  which is supported in the vane pump housing  14 . A front plate  18 , retained by suitable fasteners such as bolts  19 , closes off the front of the vane pump housing  14 . The drive shaft  16  drives a vane pump  20  incorporating the present invention. The vane pump  20  draws hydraulic fluid or oil from a sump (not illustrated) within the transmission housing  12  and provides such hydraulic fluid or oil under pressure to the various control circuits and devices (not illustrated) of the automatic transmission  10  as well as to the bearings, clutches and brakes (also not illustrated) to lubricate and cool them. 
         [0022]    Referring now to  FIG. 2 , the vane pump  20  includes, as noted, a housing  14  which includes an elliptical or oval pump cavity  22  defined by an elliptical or oval wall  24 . It should be appreciated that wall profiles other than elliptical or oval may also be utilized. Centrally disposed for rotation within the pump cavity  22  is a hollow cylindrical pump rotor  26 . The pump cavity  22  is thus defined by the outer surface of the pump rotor  26  and the elliptical or oval wall  24  and therefore takes the shape of two opposed and symmetrical arcuate or crescent like first and second pumping chambers  28 A and  28 B. Adjacent the two regions where the first and second pumping chambers  28 A and  28 B are the narrowest, are disposed a plurality of ports which provide fluid communication into and out of the chambers  28 A and  28 B. For purposes of explanation, it will be assumed that the pump rotor  26  rotates clockwise as viewed in  FIG. 2 . So driven, a first inlet port  32 A provides hydraulic fluid or oil to the first pumping chamber  28 A and a first outlet port  34 A exhausts the pressurized hydraulic fluid or oil from the first pumping chamber  28 A. Likewise, a second inlet port  32 B provides hydraulic fluid or oil into the second pumping chamber  28 B and a second outlet port  34 B exhausts the pressurized hydraulic fluid or oil from the second pumping chamber  28 B. Rotation of the pump rotor  26  in the opposite direction, i.e., counter-clockwise when viewed in  FIG. 2 , will reverse the function and thus the designation of the inlet ports  332 A and  32 B and the outlet ports  34 A and  34 B as those familiar with vane pumps will readily appreciate. 
         [0023]    The pump rotor  26  includes a plurality of, but preferably four as illustrated, equally circumferentially spaced axially extending and radially oriented slots  36  which each receive one of a like plurality of pump vanes  40 . It will be appreciated the more or fewer slots  36  and pump vanes  40  may be utilized depending upon the design criteria of the vane pump  20 . Any pressure generated by the vane pump  20  is routed by a passageway (not illustrated) to the center of the pump  20  to drive the pump vanes  40  radially outwardly to aid sealing. As the pump rotor  26  rotates, the pump vanes  40  slide radially in and out and contact the elliptical or oval wall  24  of the pump cavity  22  due to the centrifugal force and the centerline pressure generated by rotation of the rotor  26 . 
         [0024]    Clearly, in order for the vane pump  20  to provide pressurized hydraulic fluid or oil, a reasonably good seal must be maintained between the outer edges of the pump vanes  40  and the elliptical or oval wall  24  of the pump cavity  22 . When the pump rotor  26  is rotating relatively rapidly, the necessary seal quality is achieved by centrifugal force and centerline pressure. At low speeds, pump efficiency may drop due to reduced centrifugal force and increased leakage. A worst case scenario is the startup of an unprimed pump. If sufficient suction cannot be generated in spite of the lack of oil or fluid, reduced operating speed, reduced centrifugal force and thus reduced seal quality, the vane pump may take an undesirably long time to prime. 
         [0025]    Referring now to  FIGS. 2 ,  3  and  4 , the pump rotor  26  is, as noted, hollow and includes a stepped, inner wall  44  having a first, smaller diameter shoulder  46  adjacent the mid-point of its axial length. The shoulder receives and supports a nominally circular spring  50 , i.e., a spring which is circular in its relaxed state. The spring  50  may be a garter spring or it may be an annulus of a resilient material such as an elastomer, e.g., rubber or neoprene. In fact, any suitably rugged and durable material or spring configuration capable of providing a radially outward biasing force to the pump vanes  40  is suitable. Preferably, the spring  50  is located axially so that it engages the axial midpoint of the pump vanes  40  in order to bias and maintain them parallel to the elliptical or oval wall  24  of the pump cavity  22 . 
         [0026]    Referring now to  FIGS. 4 and 5 , the spring  50  is retained in position on the shoulder  46  of the inner wall  44  and in contact with the inner edges of the pump vanes  40  by a disc or collar  52 . The disc or collar  52  includes a plurality of, preferably four as illustrated, narrow slits  54  which accept and provide clearance for each of the pump vanes  40  as they reciprocate in the pump rotor  26 . The disc or collar  52  will include a number of slits  54  at least equal to the number of pump vanes  40  and the slits  54  will be arranged similarly in order to provide clearance for the pump vanes  40 . The disc or collar  52  is preferably a circular, relatively thick metal disc which has an outside diameter just slightly larger than the larger diameter portion of the stepped inner wall  44  of the pump rotor  26  such that it may be pressed in place to bottom out on a second, larger diameter shoulder  56 . 
         [0027]    Thus it will be appreciated that a vane pump  20  including a spring  50  according to the present invention exhibits improved seal quality both when the pump is not primed and when it is operating at low speeds due to the radially outwardly directed force imposed on the pump vanes  40  by the spring  50  which maintains them in close contact with the elliptical or oval wall  24  of the pump cavity  22 . 
         [0028]    The description of the invention is merely exemplary in nature and variations that do not depart from the gist 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.