Abstract:
A pump, in particular a vacuum pump for motor vehicles, wherein a rotor with at least one vane is mounted inside a pump housing, the rotor being rotatably driven by the combustion engine of the motor vehicle via a coupling device. An intermediate element is arranged between the rotor and the coupling device so as to captively retain the rotor and coupling device and protect them against wear.

Description:
The present invention relates to a pump, in particular a vacuum pump for motor vehicles, in which a rotor having at least one vane is rotatably driveably supported within a pump housing and is rotatably driven by the combustion engine of the motor vehicle via a coupling device, and in which an intermediate element is disposed between the rotor and the coupling device so as to provide a captive connection and wear protection between the rotor and the coupling device. 
     BACKGROUND 
     Pumps of this kind are generally known. However, they have the disadvantage that the intermediate element secures the coupling device to the rotor in such a manner that the coupling device is only able to perform a translational movement, but not a pivoting movement. Therefore, it is not possible to compensate for any misalignment between the driving device and the rotor, which would require the coupling element to perform a pivoting movement. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a pump which does not have these disadvantages. 
     The present invention provides a pump, in particular a vacuum pump for motor vehicles, in which a rotor having at least one vane is rotatably driveably supported within a pump housing and is rotatably driven by the combustion engine of the motor vehicle via a coupling device, and in which an intermediate element is disposed between the rotor and the coupling device so as to provide a captive connection and wear protection between the rotor and the coupling device, the intermediate element providing a pivot bearing within the rotor for the coupling device. A pump is preferred in which the intermediate element is designed such that the coupling device does not touch the rotor. This provides the advantage that the intermediate element also provides wear protection in the event of reverse rotation, as may occur when turning off the combustion engine or due to oscillations superimposed on the rotary motion. 
     A possible feature of a pump according to the present invention may include that the intermediate element is substantially in the form of a cap-shaped sheet-metal part which is disposed in a groove in the rotor and which, on the one hand, provides a captive connection to the coupling device while allowing the coupling device to perform a pivoting movement and, on the other hand, provides a fixed connection to the rotor. A pump is preferred in which the coupling device is substantially in the form of a strip-shaped element including a pivot portion which is rounded at one long side and supported within the intermediate element, and a rectangular engagement portion which is located on the opposite long side and engages with, for example, a groove of a driving device, such as the camshaft of a combustion engine of a motor vehicle. 
     In a preferred pump, the coupling device is, in addition, provided with lateral recesses into which are snapped the captive connectors of the intermediate element, which are in the form of clipping devices. 
     Also preferred is a pump in which the coupling device is supported in such a way that it can pivot in the intermediate element in the rotor and move about its longitudinal axis in the groove of the driving device. This provides the advantage that any offset between the drive shaft and the rotor can be compensated for by the pivoting movement on the one hand, and by the translational movement in the groove within the driving device. 
     It is a feature of a pump according to the present invention that the coupling device is made from sintered steel, or stamped out from bar stock. Also preferred is a pump in which the rotor is made of plastic, preferably PA6.6, or of aluminum. 
     Further preferred is a pump in which the rotor, the intermediate element, and the coupling device form a captive assembly after they are assembled, in particular after they are clipped together. A pump is preferred in which, after assembly, the components of the assembly are captively but separably connected to each other, the intermediate element having so-called “curved tongues”. Further preferred is a pump in which, after assembly, the components of the assembly are inseparably connected to each other, the intermediate element having so-called “hook tongues”, which act as barbs. 
     It is a feature of a pump according to the present invention that the intermediate element is made from sheet metal by stamping and bending. In addition, a pump is preferred in which the intermediate element has cutouts in the short sides and in the region of the rounded bottom, said cutouts allowing for inward flexing movements during insertion of the intermediate element into the rotor groove. Also preferred is a pump in which the intermediate element is clamped by its long sides within the rotor groove, while at its transverse sides, it is clamped, in particular clipped, into the recesses of the coupling device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be described with reference to the Figures. 
         FIG. 1  is a three-dimensional view of the three components, namely the rotor, the intermediate element, and the coupling device; 
         FIG. 2  is a cross-sectional view showing the elements of  FIG. 1  in an assembled condition; 
         FIG. 3  is a variant of  FIG. 1  with a different intermediate element; 
         FIG. 4  is a cross-sectional view showing the elements of  FIG. 3  in an assembled condition. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a three-dimensional view showing the three components of the assembly to which the present invention has application, namely a rotor  1  of a vacuum pump, an intermediate element  3 , and a coupling device  5 . Intermediate element  3  is shown in more detail in enlarged view  7 . Rotor  1 , which is preferably made of plastic, has a cylindrical portion of greater diameter  10 , which has a slot  12  to receive a vane  110 . Vacuum pumps constructed in this manner are therefore also called “mono-vane cell vacuum pumps”. Rotor  1  further has a cylindrical portion of smaller diameter  14 , which also serves as a plain bearing within a pump housing  100 . Moreover, rotor  1  has a second cylindrical portion of smaller diameter  16 , which serves as a second bearing within the vacuum pump housing. Cylindrical portion  14  has an end face  18  in which is formed a groove  20 . Groove  20  serves to receive intermediate element  3  or  7 , which can be made, for example, from a sheet iron material or a different metal material by stamping and bending. Intermediate element  3  can be inserted into groove  20  of rotor  1  by a type of resilient clamped connection, as will be described in greater detail hereinafter. A strip-shaped element is used as the coupling device  5 , said strip-shaped element having a rounded longitudinal surface  22  on one long side, and an approximately rectangular engagement portion  24  on the opposite long side. The long side with the rounded pivot portion  22  of coupling device  5  is supported in a rounded bottom portion  26  of intermediate element  7  or  3 , and thus can allow for slight pivoting movements of coupling device  5  within intermediate element  7 . Via the rectangular engagement portion  24 , which projects beyond the intermediate element, the coupling device can be engaged with, for example, a slot of a camshaft, so that rotor  1  of the vacuum pump is rotatably driven by the camshaft, and thus by the combustion engine, via coupling device  5 . In order to transmit the occurring driving forces, coupling element  5  is made of a metal material, preferably of sintered metal. Since, in order to reduce the inertial forces, rotor  1  is made of a softer plastic material, direct engagement of coupling device  5  with plastic groove  20  of rotor  1  would result in considerable wear and possibly destruction of the plastic rotor, because coupling device  5  must perform relative movements with respect to both rotor  1  and the driving camshaft in order to compensate for misalignment between camshaft and the plastic rotor. Intermediate element  3  or  7  is needed, inter alia, to avoid this wear problem. To this end, intermediate element  3  or  7  must be fixedly disposed in rotor groove  20 , so as to prevent relative movement between intermediate element  3  or  7  and rotor nut  20 . However, to be able to use the pivotable coupling element  5 , intermediate element  3 ,  7  must also be designed in such a way that the required pivoting movement can be performed within intermediate element  3 ,  7 . This is ensured by rounded bottom  26  of the intermediate element and rounded long side  22  of coupling device  5 . Coupling device  5  further has two additional recesses  28  provided in its short sides. When inserting coupling device  5  into intermediate element  7 , two tongues  34  having spherical segment-shaped depressions  30  are resiliently pressed apart, and then snap into recesses  28 , thereby captively connecting coupling device  5  to intermediate element  7 , which is fixedly seated in plastic rotor  1 , while still allowing coupling element  5  to perform a slight pivoting movement within connecting element  7 . To allow resilient flexure of the tongues  34  provided with the spherical segment-shaped depressions  30 , suitable slots  32  are provided between resilient tongues  34  and longitudinal side walls  36  of intermediate element  7 . Moreover, intermediate element  7  has cutouts  38  in its short sides in the region of the rounded bottom, thereby providing both a clearance for resilient movement of tongues  34  and a clearance for resilient clamping movement of side faces  36  in groove  20 . Since coupling element  5  is clipped within connecting element  7 , coupling element  5  is supported in such a way that it can, in fact, pivot but not move radially within rotor  1 . To be able to compensate for axial misalignment between the drive shaft and the pump motor, some radial movement must be allowed between rectangular engagement portion  24  and a corresponding slot in the camshaft of the combustion engine. 
       FIG. 2  shows in a cross-sectional view the three elements rotor  1 , intermediate element  3  or  7 , and coupling device  5  in an assembled condition. The cross-sectional view shows particularly well that spherical segment-shaped depressions  30  of intermediate element  3  or  7  snap into recesses  28  of coupling element  5 . Furthermore, the cross-sectional view shows particularly well that rounded bottom  26  and the tongues  34  with the spherical segment-shaped depressions  30  prevent contact between coupling element  5  and the walls of groove  20  in plastic rotor  1 . Thus, wear is prevented between coupling device  5  and plastic rotor  1 , and the maximum permitted surface pressure on the walls of groove  20  of plastic rotor  1  is not exceeded. Housing  100  and vane  110 , as well as camshaft  120  and engine  130  are shown schematically. 
       FIG. 3  shows the three components of another assembly according to the present invention, which are configured in a manner substantially similar to those in  FIG. 1 . The difference is in the configuration of intermediate element  39 , which now has resilient tongues  40  provided with hook-shaped latching members  42 . The required resilient movement is again made possible by cutouts  32  and  38 , as already described in  FIG. 1 . 
     In the cross-sectional view of  FIG. 4 , it can clearly be seen that, in this case, when attempting to extract coupling element  5 , the hook-shaped latching members  42 , which again snap into recesses  28 , would counteract such movement in the manner of barbs. In this case, due to the special shape of latching members  42 , the connection provided between coupling device  5 , intermediate element  39 , and plastic rotor  1  is clippable but cannot be separated anymore after assembly. 
     Thus, the present invention enables the pivotable drive coupling  5  of a vacuum pump to be mounted captively, in particular in a clipping manner, by applying a slight assembly force. Coupling  5  transmits the rotary motion of a camshaft to rotor  1  via a sheet-metal holder  3 ,  7 ,  39  (an insert for reducing wear), and, in addition to performing a pivoting movement, is able to compensate for misalignment in the axial and radial directions. Intermediate element  3 ,  7 ,  39 , i.e., the sheet-metal holder, can be formed by making a tongue  42 , a nose or a curvature  30  in the sheet metal holder in the longitudinal axis of the coupling by means of stamping and bending, and providing a corresponding recess  28  on the coupling for fixating purposes. Intermediate element  3  or  7 , i.e., the sheet-metal holder, can be fixed in rotor  1  by resilient longitudinal walls  36 , providing a clamped connection or a clipping connection. 
     LIST OF REFERENCE NUMERALS 
     
         
           1  rotor 
           3  intermediate element, sheet-metal holder 
           5  coupling device 
           7  intermediate element, shown enlarged 
           10  cylindrical portion of greater diameter 
           12  vane slot 
           14  cylindrical portion of smaller diameter 
           16  second cylindrical portion of smaller diameter 
           18  rotor end face 
           20  rotor groove 
           22  rounded longitudinal surface of the coupling 
           24  rectangular engagement portion of the coupling 
           26  rounded bottom portion of the intermediate element 
           28  lateral recesses of the coupling device 
           30  spherical segment-shaped depressions of the resilient tongues 
           32  slots between the resilient tongues and the longitudinal side walls 
           34  resilient tongues 
           36  longitudinal side walls of the intermediate element 
           38  cutouts of the intermediate element 
           39  different intermediate element 
           40  resilient tongues of intermediate element  39   
           42  latching members of the resilient tongues  40