Abstract:
A hydraulic vane pump includes a plurality of members forming a recession and an orifice in fluid communication with one another and with rotating vane cells at an inlet sector of the pump. Air entrained in the vane cells is exhausted through the recession and the orifice prior to fluid passing from the inlet sector to a discharge sector, thereby increasing pump capacity and decreasing cavitation noise. A method of pumping fluid in a vane pump to decrease cavitation noise is also provided.

Description:
TECHNICAL FIELD  
       [0001]     The invention relates to a hydraulic vane pump configured to vent entrained air from pumped fluid.  
       BACKGROUND OF THE INVENTION  
       [0002]     Air entrained in fluid pumped by a hydraulic vane pump reduces pump capacity and may cause unwanted pump noise due to cavitation. Cavitation occurs when the entrained air collapses or implodes as it passes from a relatively low pressure region of a pump, such as a fluid inlet, to a relatively higher pressure region, such as a discharge or outlet region.  
       SUMMARY OF THE INVENTION  
       [0003]     The invention comprises a hydraulic vane pump configured to vent entrained air from pumped fluid before the fluid passes to the discharge area, thereby increasing pump capacity and reducing unwanted cavitation noise. The pump includes a plurality of vanes circumferentially spaced about a rotor for rotation therewith. A plurality of members cooperate with the rotating vanes and rotor to define reciprocally expanding and contracting vane cells in a fluid inlet sector and a fluid discharge sector, respectively. The members may include a cam ring defining a generally oval cavity, the rotor and vanes being rotatable within the cavity.  
         [0004]     The plurality of members defines an air flow path, including an orifice and a recession disposed at the inlet sector and in fluid communication with one another and the vane cells such that entrained air in the fluid is vented through the orifice to the recession before the fluid is transferred by the rotating vanes to the outlet sector. The air flow path thus creates a connection capacitance between the vane cells and the inlet sector to discharge entrained air. By discharging the entrained air at the inlet sector, pump capacity is increased because the volume of pumped fluid is not unnecessarily decreased by the volume of entrained air (i.e., pump capacity is maximized). By discharging the entrained air, pump cavitation noise is reduced or eliminated.  
         [0005]     In one aspect of the invention, the recession and orifice are radially aligned so that entrained air is vented from one of the vane cells through the orifice to the recession as the vane cell rotates past the orifice.  
         [0006]     In yet another aspect of the invention, the recession extends from the orifice toward the fluid inlet to form an air vent passage from the vented vane cell back to the fluid inlet.  
         [0007]     In a further aspect of the invention, the plurality of members includes a pump housing disposed on one side of the rotor. The recession may be formed in the pump housing.  
         [0008]     In yet another aspect of the invention, the plurality of members includes a thrust plate disposed on the same side of the rotor as the pump housing. The orifice may be formed in the thrust plate. The thrust plate may form both the fluid inlet and the fluid outlet.  
         [0009]     In still a further aspect of the invention, the vane cells may define two inlet sectors, i.e., first and second inlet sectors, as well as first and second discharge sectors. First and second recessions and first and second orifices may be formed respectively at the first and second inlet sectors. By providing a recession that is in fluid communication with an orifice at each of the inlet sectors, pump capacity is further increased and cavitation noise further decreased.  
         [0010]     A method of decreasing cavitation noise in a vane pump includes forming a recession in pump structure. The method further includes forming an orifice in other pump structure. The method further includes locating the recession and the orifice in fluid communication with one another and with rotating vane cells in an inlet sector of the vane pump between a fluid inlet and a fluid outlet. The method further includes providing fluid to the vane cells. The method further includes venting entrained air from the fluid through the orifice to the recession. After the exhausting step, the method includes discharging the fluid from the vane cells. Accordingly, entrained air is vented prior to discharging the fluid.  
         [0011]     The method may include installing the vane pump on a vehicle for pumping fluid, such as transmission fluid. The vane pump may alternatively be used for pumping other fluids on the vehicle such as brake or steering fluids.  
         [0012]     The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  is a schematic illustration of a vehicle having a transmission with a hydraulic vane pump for pumping fluid within the transmission;  
         [0014]      FIG. 2  is a schematic perspective illustration in exploded view of the hydraulic vane pump of  FIG. 1 ;  
         [0015]      FIG. 3  is a schematic illustration in plan view of a rotor having a plurality of vanes rotating within an oval cavity formed by a cam ring in the hydraulic vane pump of  FIGS. 1 and 2 ;  
         [0016]      FIG. 4  is a schematic illustration in plan view of a thrust plate used in the hydraulic vane pump of  FIGS. 1 and 2 ;  
         [0017]      FIG. 5  is a schematic illustration in plan view of a pump housing of the hydraulic vane pump of  FIGS. 1 and 2 ;  
         [0018]      FIG. 6  is a schematic illustration in fragmentary plan view of the rotating vanes of  FIG. 3  abutting the thrust plate of  FIG. 4  and the pump housing of  FIG. 5  to illustrate an air flow path; and  
         [0019]      FIG. 7  is a flow diagram illustrating a method of decreasing cavitation noise in a vane pump.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0020]     Referring to the drawings, where like reference numbers refer to like components,  FIG. 1  illustrates a vehicle  10  having a transmission  12  for transmitting power from a power plant  14 , such as an engine, to wheels  16  as is well understood by those skilled in the art. A hydraulic vane pump  18  is mounted within or connected to the transmission  12  for pumping transmission fluid throughout the transmission  12 .  
         [0021]     Referring to  FIG. 2 , the hydraulic vane pump  18  is shown in greater detail. An end cover retaining ring  20  acts to retain a pump end cover  22  to a pressure plate  24 . A pump end cover O-ring seal  26  as well as a pressure plate spring  28  are disposed between the pump end cover  22  and the pressure plate  24 .  
         [0022]     A cam ring  30  having a generally oval-shaped cavity  32  is disposed between the pressure plate  24  and a thrust plate  34 . A pump rotor  36  forms a plurality of vane slots  38  circumferentially spaced about the rotor  36 . A plurality of vanes  40  are received within the slots  38 . The rotor  36  and vanes  40  are rotatable within the oval-shaped cavity  32  of the cam ring  30  between the abutting pressure plate  24  and thrust plate  34 . A pump drive shaft  42  is connected to a source of power such as the power plant  14  or an electric motor and rotates to turn the rotor  36 . A pump drive shaft retaining ring  44  helps to keep a toothed shaft  46  of the pump drive shaft  42  within a central annulus  48  of the rotor  36 .  
         [0023]     Cam ring dowel pins  50  secure the end cover  22 , pressure plate  24 , cam ring  30  and thrust plate  34  to a pump housing  52 . A pump O-ring seal  54  is disposed between the assembled pressure plate  24  cam ring  30  and thrust plate  34  and the pump housing  52 . A pump drive shaft seal  56  seals the drive shaft  42  within the pump housing  52 . A pressure release valve assembly  58  is connected to the pump housing  52  and acts to relieve pressure when pressure within the pump  18  rises above a predetermined level.  
         [0024]     Referring now to  FIG. 3 , the cam ring  30  defines the oval-shaped cavity  32  in which the rotor  36  and plurality of vanes  40  rotate. The vanes  40  define a plurality of vanes cells  58  (a vane cell being between each pair of adjacent vanes) that expand and contract as the vanes  40  rotate within the oval-shaped cavity. The expanding and contracting vane cells  58  create fluid inlet sectors  60 A and  60 B generally in the area of expanding vane cells, and fluid discharge sectors  62 A and  62 B generally in the area of the contracting vane cells. Dowel pin openings  64 A,  64 B are formed within the cam ring  34  for receiving the cam ring dowel pins  50  of  FIG. 2 .  
         [0025]     Referring to  FIG. 4 , the thrust plate  34  is formed with dowel pin openings  64 A′,  64 B′ alignable with the dowel pin openings  64 A,  64 B of  FIG. 3 , and dowel pin openings  64 A″,  64 B″ of the pump housing  52  of  FIG. 5 , with the thrust plate  34  positioned between the rotor  30  and the pump housing  52 . The thrust plate  34  forms inlet notches  66 A and  66 B positioned at the inlet sectors  60 A,  60 B of  FIG. 3 , respectively, through which fluid is supplied to the vane cells from a pump sump (not shown). Discharge ports  68 A,  68 B are also formed in the thrust plate  34  and are positioned at the discharge sectors  62 A,  62 B, respectively. Importantly, two orifices  70 A and  70 B are formed in the thrust plate  34 . The orifices are positioned relatively close to the inlet notches  66 A,  66 B. In a preferred embodiment, each of the orifices is 1.8 mm in diameter and is located radially 20.86 mm from the center C of the thrust plate  34 . In this preferred embodiment, the center of each of the orifices  70 A,  70 B is displaced 72 degrees from the center of the respective dowel pin openings  64 A′,  64 B′.  
         [0026]     Referring now to  FIG. 5 , the pump housing  52  is shown with a generally planar inner surface  72  formed with two discharge ports  68 A′,  68 B′ generally alignable with the respective discharge ports  68 A,  68 B of  FIG. 4 .  
         [0027]     Two recessions  74 A,  74 B are machined or otherwise formed into the inner surface  72 . In a preferred embodiment, the recessions  74 A,  74 B are generally shaped with a main portion and an elongated tail portion extending therefrom (main portion  76 A and tail portion  78 A of recession  74 A labeled in  FIG. 6 ). The center of each of the main portions is angularly displaced from the respective dowel pin openings  64 A″,  64 B″ about 73 to 78 degrees so that the respective main portions abut the orifices  70 A,  70 B, when the thrust plate  34  is placed adjacent to the inner surface  72  of the pump housing  52  (as may be viewed with respect to orifice  70 A and main portion  76 A of recession  74 A in  FIG. 6 ) and the orifices  70 A,  70 B and recessions  74 A,  74 B are located at respective inlet sectors  60 A,  60 B. The elongated tail portions extend rearward from the main portions to be in fluid communication with the openings defined by the inlet notches  66 A,  66 B (i.e., the fluid inlets), as illustrated with tail portion  78 A and inlet notch  66 A in  FIG. 6 .  
         [0028]     Referring to  FIG. 6 , the orifice  70 A (shown in phantom) is positioned in fluid communication with the main section  74 A. As the vanes  40  rotate past the fluid inlet at the inlet notch  66 A, air entrained within the fluid is vented through the orifice  70 A to the main portion  76 A of the recession  74 A. Because the elongated tail portion  78 A of the recession  74 A extends toward the fluid inlet at the notch  66 A to establish fluid communication with the inlet, vented air in the recession  74 A is expelled back to the inlet region. Thus, the vane cell  58  shown in  FIG. 6  is generally free of entrained air before it moves to the discharge port  68 A. More complete fluid compression is therefore possible as the vane cell  58  is further contracted in moving towards the discharge port  68 A. Because entrained air is vented earlier in the compression process, cavitation noise is reduced. The arrow A in  FIG. 6  denotes an air flow path including the orifice  70 A and the recession  74 A between the vane cell  58  and the inlet area at the inlet notch  66 A.  
         [0029]     Referring to  FIG. 7 , a method  100  of decreasing cavitation noise in the vane pump includes forming a recession in pump structure  102 . The method  100  further includes forming an orifice in other pump structure  104 . The method  100  further includes locating  106  the recession and the orifice in fluid communication with one another and with vane cells in the vane pump at an inlet sector between a fluid inlet and a fluid outlet. The vane pump has reciprocally expanding and contracting vane cells in fluid communication with the fluid inlet and the fluid outlet, respectively. The method  100  further includes providing fluid to the vane cells  108 . The method  100  further includes venting entrained air  110  from the fluid through the orifice to the recession. The method  100  further includes, after the venting step  110 , discharging the fluid  112  from the contracting vane cells through the fluid outlet. Finally, the method  100  may further include installing  114  the vane pump on a vehicle for pumping transmission or other fluid, such as brake or steering fluid.  
         [0030]     While the best mode for carrying out the invention has been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.