Abstract:
The invention relates to a vane pump comprising a rotor which is arranged therein, rotatably driven by a drive shaft. The rotor is provided with several grooves which are distributed through the circumference thereof and which extend substantially radially with respect to the axis of rotation of the rotor. In each groove a blade-shaped conveying element is slidingly guided. The end walls of the pump housing are adjacent to the rotor in the direction of the axis of rotation thereof. At least one ring-shaped groove surrounding the axis of rotation of the rotor is embodied in at least one front side of the rotor. The ring-shaped groove is connected to lower areas restricted by the blades in the grooves of the rotor, and to pressure areas. In a preferred embodiment, the ring-shaped groove is formed in the rotor by shaping.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a 35 USC 371 application of PCT/EP 2005/066201 filed on 11 Sep. 2006. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention is based on a vane pump. 
     2. Description of the Prior Art 
     A vane pump of this kind is known from DE 199 52 167 A1. This vane pump has a pump housing that contains a rotor, which is rotatably driven by a drive shaft. The rotor has a plurality of grooves distributed over its circumference that extend at least essentially radially in relation to the rotation axis of the rotor, with a vane-shaped delivery element guided in each groove in sliding fashion. The pump housing has a circumference wall encompassing the rotor, eccentric to the rotor&#39;s rotation axis, against which the radially outer ends of the vanes rest. The pump housing has housing end walls that adjoin the rotor in the direction of its rotation axis. Due to the eccentric arrangement of the circumference wall as the rotor rotates, expanding and contracting chambers are formed between the vanes and by means of a pressure increase, the medium to be supplied is fed from a suction region to a pressure region that is offset from it in the circumference direction. As the rotor rotates, centrifugal force holds the vanes in contact with the circumference wall; but when the vane pump is being started, at low rotation speed, only slight centrifugal forces are exerted so that the vane pump only delivers a small quantity. In the known vane pump, another feed pump that forms a combined pump apparatus with the vane pump supplies compressed medium into the internal regions delimited by the vanes in the grooves of the rotor, which causes the vanes to be pressed radially outward toward the circumference wall in addition to the centrifugal force. In this case, at least one housing end wall contains an annular groove, which extends over part of the circumference of the rotor and is supplied with compressed medium by the additional feed pump. Manufacturing the annular groove in the housing end wall in this case is complex and usually has to be carried out by means of a material-removing machining process such as milling. 
     SUMMARY AND ADVANTAGES OF THE INVENTION 
     The vane pump according to the invention has the advantage over the prior art that its manufacture is simplified in that the at least one annular groove can be produced more easily in the rotor than in the housing end wall. 
     The invention permits an exertion of pressure on both sides of the rotor so that at least essentially no axial forces act on it and the wear on the rotor and the housing end walls can be kept to a minimum. The invention makes it possible to at least almost completely prevent the exertion of axial forces on the rotor with a simultaneously limited span of the annular grooves in the two end surfaces of the rotor. It is particularly advantageous in that one annular groove only connects two successive grooves in the rotor to each other since this makes it possible to minimize possible leakage losses. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a simplified cross section through a vane pump, extending along the line I-I in  FIG. 3 , 
         FIG. 2  is a cross section through the vane pump, extending along the line II-II in  FIG. 3 , according to a first exemplary embodiment, 
         FIG. 3  is a longitudinal section through the vane pump, extending along the line III-III in  FIG. 1 , and 
         FIG. 4  is a cross section through the vane pump, extending along the line II-II, according to a second exemplary embodiment. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIGS. 1 through 4  show a vane pump that is preferably provided for delivering fuel, in particular diesel fuel. In this case, the vane pump delivers fuel from a tank to a high-pressure pump. The vane pump can either be situated separately from the high-pressure pump, attached to the high-pressure pump, or integrated into the high-pressure pump. The vane pump has a pump housing  10 , which is comprised of multiple parts, and a drive shaft  12  that protrudes into the pump housing  10 . The pump housing  10  has two housing end walls  14 ,  16  that delimit a pump chamber in the axial direction, i.e. in the direction of the rotation axis  13  of the drive shaft  12 . In the circumference direction, the pump chamber is delimited by a circumference wall  18  that can be embodied as integrally joined to one of the housing end walls  14 ,  16  or can be separate from them. The rotor  20  has end surfaces  201  and  202  oriented toward the housing end walls  14 ,  16 . 
     As depicted in  FIGS. 1 ,  3 , and  4 , the pump chamber contains a rotor  20  that is attached in nonrotating fashion to the drive shaft  12 , for example by means of a groove/spring connection  22 . The rotor  20  has a plurality of grooves  24  that are distributed over its circumference and extend at least essentially radially in relation to the rotation axis  13  of the rotor  20 . The grooves  24  extend into the rotor  20  from its outer circumference toward the rotation axis  13 . For example, four grooves  24  are provided; it is also possible for more or less than four grooves  24  to be provided. Each groove  24  accommodates a plate-shaped delivery element  26  in sliding fashion, which will be referred to below as a vane and whose radially outer end region protrudes out from the groove  24 . Each vane  26  delimits a radially inner internal region  25  in the respective groove  24 . 
     The inside of the circumference wall  18  of the pump housing  10  is situated eccentrically in relation to the rotation axis  13  of the rotor  20 , for example in circular fashion or in another form. In at least one housing end wall  14 ,  16  a suction region is provided, as depicted in  FIG. 2 , into which at least one suction opening  28  feeds. In the suction region, a suction groove  30  is preferably provided in at least one housing end wall  14 ,  16 ; this groove is elongated in the circumference direction of the rotor  20  and is curved in an approximately kidney-shaped fashion and the suction opening  28  feeds into it. The suction opening  28  preferably feeds into the suction groove  30  in its end region oriented away from the rotation direction  21  of the rotor  20 . The suction opening  28  is connected to a supply line leading from the tank. In addition, a pressure region is also provided in at least one housing end wall  14 ,  16 , into which region at least one pressure opening  32  feeds. In the pressure region, a pressure groove  34  is preferably provided in at least one housing end wall  14 ,  16 ; this groove is elongated in the circumference direction of the rotor  20  and is curved in an approximately kidney-shaped fashion and the pressure opening  32  feeds into it. The pressure opening  32  preferably feeds into the pressure groove  34  in its end region oriented in the rotation direction  21  of the rotor  20 . The pressure opening  32  is connected to an outlet leading to the high-pressure pump. The suction opening  28 , the suction groove  30 , the pressure opening  32 , and the pressure groove  34  are spaced radially apart from the rotation axis  13  of the rotor  20  and are situated close to the inside of the circumference wall  18 . The radially outer ends of the vanes  26  rest against the inside of the circumference wall  18  and slide along it during the rotating motion of the rotor  20  in the rotation direction  21 . Due to the eccentric arrangement of the inside of the circumference wall  18  in relation to the rotation axis  13  of the rotor  20 , chambers  36  with different volumes are formed between the vanes  26 . The suction groove  30  and the suction opening are situated in a circumference region in which, with a rotating motion in the rotation direction  21  of the rotor  20 , the volume of the chambers  36  increases so that they are filled with fuel. The pressure groove  34  and the pressure opening  32  are situated in a circumference region in which, with a rotating motion in the rotation direction  21  of the rotor  20 , the volume of the chambers  36  decreases so that fuel is displaced from the chambers into the pressure groove  34  and from it, into the pressure opening  32 . 
     In a first exemplary embodiment shown in  FIG. 2 , in at least one end wall  201 ,  202  ( FIG. 3 ) of the rotor  20  a ring-shaped groove  38  is provided, which extends over the entire circumference of the rotor  20  and communicates with the respective internal regions  25  that are delimited by each vane  26  in its respective groove  24 . The ring-shaped groove  38  will be referred to below as the annular groove  38 . For example, the annular groove  38  can extend so that its radially inner edge extends at least approximately at the same radial distance from the rotation axis  13  of the rotor  20  as the radially inner edges of the grooves  24  in the rotor  20 ; in this case, the annular groove  38  then feeds into the grooves  24  in approximately tangential fashion. It is also possible for the radially inner edge of the annular groove  38  to extend spaced a smaller radial distance apart from the rotation axis  13  than the radially inner edges of the grooves  24 ; in this case, the annular groove  38  then feeds into the groove  28  in an approximately radial fashion, for example. The annular groove  38  can also extend spaced a smaller radial distance apart from the rotation axis  13  than the radially inner edges of the grooves  24  and be connected to the internal regions  25  of the grooves  24  via an additional respective groove in the rotor  20 . The annular groove  38  can also extend spaced a greater radial distance apart from the rotation axis  13  than the radially inner edges of the grooves  24 , but should be spaced a smaller radial distance apart from the rotation axis  13  than the radially inner ends of the vanes  26 . The grooves  24  subdivide the annular groove  38  into a plurality of annular groove sections. It is possible for a respective annular groove  38  to be provided in both end surfaces  201 ,  202  of the rotor  20  or it is alternatively possible for an annular groove  38  to be provided in only one end surface  201  or  202  of the rotor  20 . In the housing end wall  14 ,  16  oriented toward the end surface  201 ,  202  of the rotor  20  in which the annular groove  38  is situated, a connecting groove  40  leads inward from the pressure groove  34  and ends approximately the same distance apart from the rotation axis  13  as the annular groove  38 , thus connecting the annular groove  38  to the pressure groove  34  and therefore to the pressure region. In lieu of the connecting groove  40 , it is also possible for a connecting bore to be provided. Between the annular groove  38  and the drive shaft  12 , a sealing region  39  is formed in which there is only a slight axial distance between the rotor  20  and the adjacent housing end wall  14 ,  16 . In the region around the drive shaft  12 , only a slight pressure prevails so that there is a pressure difference between the annular groove  38  and the region around the drive shaft  12 . 
     It is also possible for the annular groove  38  on one end surface  201  or  202  to extend not over the entire circumference of the rotor  38 , but instead over only a part of the circumference; it is also possible to provide several annular grooves  38  that are offset from one another in the circumference direction. For example, several annular grooves  38  can be provided, each of which connects only the internal regions  25  of two successive grooves  24  of the rotor  20  to each other. This eliminates two sections  381 ,  382  of the annular groove  38  in the embodiment according to  FIG. 2 . A two-sided, symmetrical arrangement of the annular grooves  38  on the rotor  20  offers the advantage that almost no resulting forces are exerted on the rotor  20  in the direction of its rotation axis  13  and no tilting moments are exerted perpendicular to the rotation axis  13  so that the rotor  20  rotates at least approximately in the middle between the two housing end walls  14 ,  16 , without coming into contact with them. If respective sections of annular grooves  38  that do not extend over the entire circumference of the rotor  20  are provided in both end walls  201 ,  202  of the rotor  20 , it is then possible to minimize the leakage through the sealing region  39 . 
     The connecting groove  40  can extend inward from the pressure groove  34 , for example radially, or can be inclined in relation to a line radial to the rotation axis  13 . In particular, the connecting groove  40  can extend in such a way that it approaches the annular groove  38  in the rotation direction  21  of the rotor  20 . In addition, the connecting groove  40  can be curved in spiral fashion. One end of the connecting groove  40  preferably feeds at least approximately tangentially into the pressure groove  34  and/or the other end feeds at least approximately tangentially into the annular groove  38 . Preferably, the connecting groove  40  feeds into the end region of the pressure groove  34  oriented away from the rotation direction  21  of the rotor  20 . The connection of the annular groove  38  to the pressure groove  34  causes an elevated pressure to prevail in the annular groove  38  and therefore in the internal regions  25  of the grooves  24  of the rotor  20  connected to it, thus intensifying the contact force of the vanes  26  against the inside of the circumference wall  18  and improving the delivery capacity of the vane pump. 
     The at least one annular groove  38  is preferably provided in the rotor  20  by the initial shaping process and not by a material-removing machining process. For example, the rotor  20  can be manufactured by means of a pressing or forging process; in this case, the at least one annular groove  38  is formed in the rotor  20  through a corresponding shape of the pressing or forging die during the manufacture of the rotor  20 . In particular, the rotor  20  can be composed of sintered metal in order to assure a sufficient strength and wear resistance of the rotor  20 . 
     It is possible for the connecting groove  40  that connects the annular groove  38  to the pressure groove  34  to be provided in only one housing end wall  14  or  16 ; it is also possible for at least one connecting groove  40  to be provided in both housing end walls  14  and  16 , with the respective connecting grooves  40  being situated in mirror image fashion in relation to each other in the housing end walls  14  and  16 . It is also possible for the suction groove  30  and/or the pressure groove  34  to be provided in only one housing end wall  14  or  16 , with the respective other housing end wall  16  or  14  being embodied as smooth, or for a suction groove  30  and pressure groove  34  to be provided in respective housing end walls  14  and  16 , with the respective suction and pressure grooves being situated in mirror image fashion in relation to each other in the housing end walls  14  and  16 . In this case, the suction opening  28  and pressure opening  32  are each provided in only one respective housing end wall  14  or  16 ; the suction opening  28  is provided in one housing end wall  14  and the pressure opening  32  is provided in the other housing wall  16 . Due to the mirror-image arrangement of the suction groove  30  and pressure groove  34  and of the annular grooves  38  and connecting grooves  40  in the two housing end walls  14  and  16 , the rotor  20  and the vanes  26  are subjected to at least approximately the same load in the axial direction at both ends, thus producing little or no resulting force on the rotor  20  and vanes  26  in the direction of the rotation axis  13 . The depth of the at least one annular groove  38  in the rotor  20  and of the connecting groove  40  in the housing end wall  14 ,  16  is between 0.1 and 2 mm, for example; preferably, the width of the grooves  38 ,  40  is greater than their depth. 
       FIG. 4  shows the vane pump according to a second exemplary embodiment whose essential design is the same as in the first exemplary embodiment. The two end surfaces  201 ,  202  of the rotor  20  each have at least one annular groove  3   8  let into them, with the annular grooves  38  of the one end surface  201  extending over a different circumference region of the rotor  20  than the annular grooves  38  of the other end surface  202 . In the exemplary embodiment shown, the rotor  20  has four grooves  24 ; two annular grooves  383  of the one end surface  201  are situated diametrically opposite each other and each extend over approximately 90° between two successive grooves  24 . The two annular grooves  384  of the other end surface  202  likewise extend over approximately 90°, but are offset by 90° in relation to the grooves  383  of the end surface  201  so that they do not overlap, and likewise each extend between two successive grooves  24 . The annular grooves  384  of the end surface  202  are depicted with dashed lines in  FIG. 4  since they are on the opposite end surface  202  of the rotor  20  and are therefore not actually visible in  FIG. 4 . The embodiment according to  FIG. 4  can also be transferred to other embodiments of the rotor  20  in which the rotor  20  has an even number of grooves  24 . In this case, the annular grooves  38  on each end surface  201 ,  202  of the rotor  20  each extend only between two successive grooves  24  and the annular grooves  38  of the two end surfaces  201 ,  202  are offset from one another in the circumference direction so that they do not overlap one another. Due to this arrangement of the annular grooves  38 , at least essentially no force is exerted on the rotor  20  in the direction of the rotation axis  13 , which would push the rotor  20  against one of the housing end walls  14 ,  16  and therefore lead to an increased amount of wear. The leakage through the sealing region  39  can also be kept to a minimum. 
     The foregoing relates to the preferred exemplary embodiment of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.