Abstract:
A pump is proposed, in particular a vane pump, for a liquid or gaseous medium, which can be driven with the help of a motor, in particular an electric motor, and which comprises a rotor ( 15 ) that can be coupled to a drive shaft ( 29 ) of the motor and is arranged in an operating chamber and at least one pressure plate ( 25 ) that closes the operating chamber ( 11 ) in the axial direction and on its lateral face ( 27 ) facing away from the rotor ( 15 ) is connected to a pressure chamber ( 23 ), and also a coupling element ( 47; 47 ′) which surrounds part of the drive shaft ( 29 ), cooperates with at least one seal and contributes to sealing off the pressure chamber ( 23 ) with respect to the motor, the drive shaft ( 29 ) extending through a through opening ( 35 ) in the pressure plate ( 25 ). The pump ( 1 ) is characterized in that the coupling element ( 47; 47 ′) has a sleeve-like section ( 49 ) which engages in the through opening ( 35 ) in the pressure plate ( 25 ).

Description:
The invention relates to a pump, in particular a vane pump, for a liquid or gaseous medium and particularly the sealing of the pressure chamber and the operating chamber of the pump. 
     Known pumps of this type are used, for example, for power steering systems in a motor vehicle. They comprise an operating chamber, which is closed in the axial direction by means of at least one pressure plate. Arranged in the operating chamber is a rotor, which can be coupled to the drive shaft of an electric motor. A separate mounting for the rotor is not provided, as the rotor is mounted exclusively via the drive shaft. This configuration, however, produces large external diameters for the at least one bearing of the drive shaft and a shaft sealing ring which seals off the electric motor with respect to the pump in the area of the drive shaft. 
     On the lateral face facing away from the rotor, the pressure plate is in contact with a pressure chamber, which is sealed off with respect to the motor by a coupling element that cooperates with at least one seal and surrounds part of the drive shaft. The coupling element engages over an annular flange on the pressure plate, which flange is provided on the side facing away from the rotor and has a greater external diameter. As a result, between the flange and the coupling element, a radially inner sealing face is formed which divides the pressure chamber from the pump unit and whose distance from the axis of rotation of the drive shaft is large. The arrangement of the inner sealing face also determines the distance between the pressure chamber and the axis of rotation of the drive shaft, which is accordingly very large. As a result, the external diameter of the rotating group has to be configured in a correspondingly large manner. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the invention to provide a pump of the type mentioned at the beginning in which a more compact design, in particular a pump unit with a small external diameter, can be implemented. 
     In order to achieve this object, a pump having the features of the invention is distinguished by the fact that the coupling element has a sleeve-like section which engages in the through opening in the pressure plate. The distance between a radially inner sealing face of the pressure chamber and the axis of rotation of the drive shaft between the coupling element and the through opening in the pressure plate is therefore only very small, so that a pump unit having the pressure plate and the rotor can be implemented with a small external diameter. As a result, a pump with a compact, space-saving construction can be provided. 
     According to a development of the invention, the diameter of the through opening made in the pressure plate is smaller, preferably considerably smaller, than the external diameter of a shaft sealing ring surrounding part of the drive shaft. Since the shaft sealing ring must not be connected to the pressure chamber, a radially outer sealing face of the pressure chamber is arranged at a great distance from the drive shaft, on account of the large external diameter of the shaft sealing ring. The area located between the radially inner and the outer sealing face is advantageously covered in a sealing manner with the aid of the coupling element. According to a first design variant, for this purpose the coupling element has a collar which accommodates the shaft sealing ring and reaches beyond the section of the casing, preferably at least one second seal, for example an O ring, being provided in order to seal a gap between the collar and the section of the casing. In another design variant of the pump, the coupling element cooperates with an end face of the section of the housing that accommodates the shaft sealing ring, that is to say it does not have a sealing collar but preferably bears with a lateral face facing away from the rotor on the end face of the section of the casing. In order to seal the gap between the coupling element and the end face of the section of the casing, in one advantageous embodiment at least a third seal, for example an O ring, which can be arranged in a groove in the end face, or a sealing disk is provided. In a further design variant, the coupling element engages with its collar in a recess in the section of the casing in which the shaft sealing ring is arranged, it being possible for the gap between the outer circumferential face of the collar and the wall of the recess to be sealed, preferably by means of a third seal. 
     In a preferred embodiment, there is a clearance connected to the pressure chamber between the coupling element and the pressure plate. On the basis of this configuration, it is possible for the entire projected lateral face, facing the coupling element, of the pressure plate to be acted on by the medium under pressure, for example oil, as a result of which the pressure plate is preferably pressed against a contour ring surrounding the operating chamber. Applying pressure to the entire lateral face of the pressure plate means that deformation of the pressure plate in the manner of a disk spring, which could lead to a short circuit between an inlet zone and a delivery zone of the pump, is prevented. In order to act on the pressure plate with a force oriented in the direction of the rotor, instead of the clearance or in addition to the clearance connected to the pressure chamber, a pressing device can be provided which, for example, comprises at least one disk spring. The pressing device is particularly advantageous when the coupling element is so configured that it cooperates with the end face of the section of the casing that accommodates the shaft sealing ring. 
     In addition, preference is given to an exemplary embodiment of the pump in which, in the area between the larger-diameter collar and the smaller-diameter section engaging in the through opening in the pressure plate, the coupling element has an annular bead, which is used to stiffen the coupling element. This makes it possible to form the coupling element with a thin wall. 
     Furthermore, preference is given to an exemplary embodiment of the pump which is distinguished by the fact that the coupling element consists of sheet metal and is preferably formed in one piece. The coupling element formed as a sheet-metal molding can therefore be produced cost-effectively. Of course, the coupling element can be produced from virtually any material which, for example, can be corrosion-resistant and whose strength properties are sufficient to withstand the pressure in the pressure chamber. Since the coupling element is located in the pressure chamber or adjoins the latter, in the case of a vane pump used to deliver oil, the coupling element can also consist of a metal susceptible to rusting, since the coupling element is protected against corrosion by the oil. 
     Further advantageous embodiments emerge from the other subclaims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is explained below with references the drawings, in which: 
     FIG. 1 shows a detail of an exemplary embodiment of a pump with a first embodiment of a coupling element in longitudinal section, and 
     FIG. 2 shows a longitudinal section of a second embodiment of the coupling element. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1 shows a detail of an exemplary embodiment of a pump  1 , which is designed here as a vane pump. The pump I is arranged in the interior  3  of a casing  5  which is closed by a cover  7 . The pump  1  comprises a pump unit  9  which comprises a cam ring  13  surrounding a substantially elliptical operating chamber  11  and a rotor  15  arranged in the operating chamber  11 , in which rotor slots running radially with respect to a longitudinal mix-axis  17  are made, in which radially displaceable vanes  19  are inserted. Pump chambers which become larger and smaller are enclosed between successive vanes  19 , so that during rotation of the rotor  15 , during which the vanes  19  follow the inner contour of the cam ring  13 , a medium, for example a hydraulic oil, is conveyed from tank connections  21  into a pressure chamber  23 . From the pressure chamber  23 , the medium passes via a connecting path  24  to a load, as indicated by arrows. 
     In order to laterally terminate the delivery chambers located between the vanes  19  in the axial direction, a pressure plate  25  is provided on one side of the pump unit  9  and the cover  7  is provided on the other side. These two rest on the lateral faces of the cam ring  13  in a sealing manner and having only a small spacing from the rotor  15  and the vanes  19 . On its side face  27  facing away from the rotor  15 , the pressure plate  25  is connected to the pressure chamber  23  or, in this exemplary embodiment, is arranged in the pressure chamber  23 . 
     In a different exemplary embodiment, not illustrated in the figures, two pressure plates are provided for the lateral sealing of the delivery chambers located between the vanes  19 , said pressure plates bearing on the lateral faces of the cam ring  13 , that is to say one of the pressure plates is arranged between the cam ring  13  and the cover  7 . 
     At one end of a drive shaft  29 , the rotor  15  is connected to the latter in a rotationally fixed manner with the aid of a splined connection  31 . The drive shaft  29  is part of a motor, not illustrated, preferably an electric motor. In order to mount the drive shaft  29 , in this exemplary embodiment a bearing  33  arranged in the casing  5  is provided, and here is formed as a rolling-contact bearing. It can be seen that the cantilever-mounted rotor  15  is not provided with its own mounting. This results in a correspondingly large external diameter for the bearing  33 . 
     As FIG. 1 reveals, the drive shaft  29  extends through a through opening  35  in the center of the pressure plate  25 . The through opening  35  is formed with a stepped shape, which means that it has a plurality of longitudinal sections of different diameters. The through opening  35  is preferably circular in cross section. The diameter of the through opening  35  in its center area is here substantially as large as the diameter of the drive shaft  29  in the area of the bearing  33 . In a different exemplary embodiment, not illustrated in the Figures, the diameter of the through opening  35  is smaller than that of the drive shaft  29  in the area of its longitudinal section arranged in the bearing. The diameter of the longitudinal section of the drive shaft  29  arranged in the through opening  35  is considerably smaller than the diameter of the through opening  35 . This results in an annular chamber  37  formed between the circumferential face of the through opening  35  and the external face of the drive shaft  29 . 
     In order to seal off the motor driving the pump  1 , in the exemplary embodiment shown in FIG. 1, a shaft sealing ring  39  known per se and a slinger disk  41  arranged in the area between the shaft sealing ring  39  and the bearing  33  and having a sleeve-like base body are provided. The shaft sealing ring  39  is arranged in the area of a section  46  of the casing which extends in the manner of a dome in the direction of the interior  3  of the pump  1 . The function of the slinger disk  41  is to guide small quantities of the medium conveyed by the pump  1 , which can possibly penetrate through the gaps between the shaft sealing ring  39  and the drive shaft  29  and the shaft sealing ring  39  and the casing  5 , radially outward against the wall  43  of a recess  45  that accommodates the slinger disk  41  and the shaft sealing ring  39 , where it can be led away in a suitable manner to the outside, for example by means of a relief duct, so that it does not reach the motor. 
     In order to seal the pressure chamber  23  with respect to the recess  45  containing the shaft sealing ring  39 , a coupling element  47  is provided, which is arranged in the area between the pressure plate  25  and the shaft sealing ring  39 . Here, the coupling element  47  is formed in one piece and as a sheet-metal molding and has a sleeve-like section  49  which engages in the through opening  35  on the side of the pressure plate  25  facing away from the rotor  15 . In order to seal the gap between the section  49  of the coupling element  47  and the wall of the through opening  35 , a first seal  51  is provided, which is formed by a round sealing ring here and is arranged in a larger-diameter section of the through opening  35 . The sleeve-like section  49  is adjoined by a wall section  53  which runs substantially perpendicular to the section  49  and, on its side facing the pressure plate  25 , has an annular bead  55 , which is used to stiffen the coupling element  47  which may have a very thin wall. The bead  55  is formed by a channel-like depression on the side facing away from the pressure plate  25 . The wall section  53  that extends in the radial direction beyond the recess  45  accommodating the shaft sealing ring  39  is adjoined by a collar  57 , which engages over the section  46  of the casing and preferably encloses it completely over its circumference. In order to seal a gap between the collar  57  and the section  46  of the casing, a further, second seal  59  is provided, which is formed here by a round sealing ring, which is arranged on an annular shoulder fitted to the outer side of the section  46  of the casing. 
     As can be seen from FIG. 1, the distance between the radially inner sealing face between coupling element  49  and the wall of the through opening  35  is considerably smaller than the distance from the radially outer sealing face between the coupling element  47  and the section  46  of the casing. On account of this configuration, a pump  1  or pump unit  9  can be formed whose delivery chambers lying between successive vanes  19  are at only a small distance from the axis of rotation of the drive shaft  29 , which means that a compact pump unit  9 , in particular one having a small external diameter, can be implemented. 
     The collar  57  plugged onto the section  46  of the casing has rounding, preferably a radius R 1 , on the inner side of its free end. The rounding is used to make it easier to plug the collar  57  onto the section  46  of the casing and to avoid damage to the second sealing ring  59 . In addition, the section  49  of the coupling element  47  is provided with a rounding, preferably a radius R 2 , at its free end on the outside. This rounding is intended to make it easier to plug the section  49  into the through opening  35  in the pressure plate  25  and to prevent damage to the first seal  51 . 
     In the area of its vertical wall section  53 , the coupling element  47  is formed or so matched to the lateral face  27  of the pressure plate  25  that a substantially annular clearance  61  is formed between coupling element  47  and an annular end wall section  60  of the pressure plate  25 , said clearance being connected to the pressure chamber  23  or forming part of the pressure chamber  23 . 
     During the operation of the pump  1 , the entire lateral face  27  of the pressure plate  25  and the second seal  59  in the through opening  35  are acted on by the medium under pressure, so that the pressure plate  25  is pressed against the cam ring  13 . At the same time, the coupling element  47  is pressed with the lateral face of its radial wall section  53  against the end of the section  46  of the casing. 
     In the exemplary embodiment illustrated in FIG. 1, a pressing device  63  is arranged in the pressure chamber  23  and has a compression spring  65 , which is supported on the casing  5  via the coupling element  47  and acts on the pressure plate  25 , on its lateral face  27 , with a force oriented in the direction of the axis of rotation of the drive shaft  29 . During the operation of the pump  1 , the pressing device  63  assists the action of pressing the pressure plate  25  against the cam ring  13 . In the unpressurized state, the pressure plate  25  is pressed against the cam ring  13  only by the pressing device  63 , so that lateral sealing of the delivery chambers between the vanes  19  is provided even before the pump  1  is started up. 
     The motor, not illustrated in the figures, and the pump  1  in the exemplary embodiment illustrated in FIG. 1 form a unit when assembled, which is also the subject of the invention, the assembly of the slinger disk  41  and in particular of the shaft sealing ring  39  being carried out only after the motor has been installed from the pump side. In the exemplary embodiment shown in FIG. 1, the bearing  33  for the drive shaft  29  is introduced into the casing  5  from the motor side. 
     In another exemplary. embodiment, not illustrated in the figures, provision is made for the bearing  33  for the drive shaft  29  also to be capable of being assembled from the pump side, just like the shaft sealing ring  29 , which is associated with advantages during assembly and the coupling of the pump and of the motor to each other. In this embodiment, in particular the shaft sealing ring  39  has a very large external diameter. However, since the coupling element  47  is arranged between the pressure chamber  23  of the pump  1  and the motor, the radially inner sealing face of the pressure chamber can nevertheless be arranged very close to the point at which the drive shaft  29  passes through the pressure plate  25 , so that a smaller external diameter of the pressure plate  25  can be implemented. 
     FIG. 2 shows a second exemplary embodiment of the coupling element  47 ′, identical parts being provided with identical reference symbols, so that to this extent reference is made to the description relating to FIG.  1 . 
     The coupling element  47 ′ differs from the coupling element  47  shown in FIG. 1 only in the fact that it does not have a collar  57 . In the assembled state, the wall section  53  of the coupling element  47 ′ is pressed with its lateral face  67  facing away from the motor against the end of the section  46  of the casing. The radially outer sealing face of the pressure chamber  23  is therefore no longer located on the outside of the section  46  of the casing and therefore closer to the drive shaft  29 . In order to seal the gap between the lateral face  67  of the wall section  53  of the coupling element  47 and the end of the section  46  of the casing, a third sea′ is provided in an advantageous exemplary embodiment. The coupling element  47 ′, which can be produced more simply as compared with the coupling element  47  shown in FIG. 1, is pressed continuously in a sealing manner against the end of the section  46  of the casing, with the aid of the pressing device  63 . Of course, it may also be possible, with the aid of the medium under pressure in the pressure chamber  23 , to ensure adequate pressing of the coupling element  47 ′ against the section  46  of the casing, even when there is a low pressure in the pressure chamber  23 , in order to ensure sealing, so that it may be possible to dispense with the pressing device  63 . Furthermore, it is possible for the pressing forces to be applied by the seals. 
     The fact that the coupling element  47 ′ illustrated in FIG. 2 covers only the mouth of the recess  45  in the casing  5  means that the risk of double centering of the pressure plate  25 , which is already centered by means of pins arranged in the pressure plate  25 , the cam ring  13  and the cover  7 , of which one pin  69  is illustrated in FIG. 1, can virtually be ruled out. 
     The coupling element  47 ,  47 ′ can consist of metal or plastic and is preferably formed in one piece. In a preferred embodiment, the coupling element  47 ,  47 ′—as illustrated in FIGS.  1  and  2 —is designed symmetrically with respect to the axis. 
     On account of the space-saving design of the pump  1 , in particular because of the small external diameter of the pump unit  9 , which is only possible through the coupling element  47  or  47 ′, the use of the pump  1  driven by the motor, preferably electric motor, is particularly advantageous in a motor vehicle, in which there is only little space available and a low weight is required. 
     The advantages of the coupling element  47  and  47 ′, respectively, as described in FIGS. 1 and 2, naturally result even when the pump  1  is designed as a rolling cellular pump, blocking vane pump or the like. 
     The patent claims filed with the application are proposed formulations without prejudice for the achievement of more extensive patent protection. The applicant reserves the right to claim still further features, as yet disclosed only in the description and/or drawing. 
     Back references used in subclaims point to the further development of the subject of the main claim by means of the features of the respective subclaim; they are not to be understood as dispensing with the achievement of independent, concrete protection for the features of the subclaims making such back references. However, the subjects of these subclaims also form independent inventions, which have a structure independent of the subjects of the preceding subclaims. 
     Nor is the invention restricted to the exemplary embodiments of the description. Instead, within the scope of the invention, numerous amendments and modifications, in particular those variants, elements and combinations and/or materials which are inventive, for example as the result of combination or modification of individual features or elements or method steps with those described in the general description and embodiments and in the claims and contained in the drawings and, by means of features which can be combined, lead to a new subject or to new method steps or sequences of method steps, including those which to this extent relate to the production, testing and working methods.