Abstract:
A pump, in particular a sliding-vane pump, a roller cell pump, or a gear pump includes a rotating assembly, with, amongst other things, a rotor with radially-sliding vanes, rollers or gears and a drive shaft is provided. The rotor or a gearwheel is connected to the drive shaft by a toothing on the drive shaft and on the rotor or gearwheel for rotational drive.

Description:
BACKGROUND 
   The present invention relates to a pump, in particular to a vane-type pump, roller-cell pump, or gear pump, having a rotary assembly, which includes, inter alia, a rotor having radially displaceable vanes or rollers, or gear wheels, and having a drive shaft, the drive shaft and the rotor, respectively a gear wheel, being interlinked by a toothing on the drive shaft and on the rotor, respectively on the gear wheel, for purposes of rotational entrainment. 
   Pumps of this kind are generally known. In this context, the pumps have toothed-shaft connections having involute flanks according to DIN 5480 or spline-shaft connections having straight flanks according to DIN 5463. Neither type of connection exhibits axial convexity on the toothing, so that it is not possible to compensate for any skewed position among the drive partners. Moreover, due to the minimal clearance between the tooth flanks, torsional shocks from the drive shaft are transmitted, undamped, to the drive partners, thereby promoting wear on the drive partners. 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to devise a pump which will overcome these disadvantages. 
   This objective is achieved by a pump, in particular a vane-type pump, roller-cell pump, or gear pump, having a rotary assembly, which includes, inter alia, a rotor having radially displaceable vanes or rollers, or gear wheels, and having a drive shaft, the drive shaft and the rotor, respectively a gear wheel, being interlinked by a toothing on the drive shaft and on the rotor, for purposes of rotational entrainment, the toothing being designed in accordance with the present invention to be axially convex and radially externally centered. 
   The external centering has the advantage of making it possible to brace against transversal forces. In the case of two-stroke vane pumps, the external centering provides for a better centering. 
   A pump is preferred in which the toothing, in addition, exhibits a circumferential clearance among the tooth flanks. It is a distinguishing feature of a pump according to the present invention that the circumferential clearance encompasses an angular region of 3° to 12°, preferably of 6°. 
   A pump is also preferred in which the toothing, in addition, is able to be acted upon by a transversal force. 
   It is a distinguishing feature of a pump according to the present invention that the transversal force acting on the external centering surfaces produces tangential frictional forces between the drive shaft and the rotor, and respectively the gear wheel. This has the advantage of enabling torsional shocks to be damped, due to the circumferential clearance and the frictional forces. A pump is also preferred in which the tooth flanks of the toothing have the form of an involute toothing. A pump is also preferred in which the flanks may have a convex design in the axial direction. 
   It is a distinguishing feature of a pump according to the present invention that the teeth of the shaft are designed to be wider than the teeth of the rotor or of the gear wheel. As a result, the teeth of the shaft, which are required to absorb the transversal force and produce the moment of friction, are advantageously able to have high enough strength for this purpose. A pump is also preferred in which the teeth of the shaft are more than twice as wide as the teeth of the rotor or of the gear wheel. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     The pump is now described with reference to the figures, which show: 
       FIG. 1  a plan view of a rotor having a toothing according to the present invention. 
       FIG. 2  an enlarged detail of the rotor toothing. 
       FIG. 3  an end of a drive shaft having the toothing according to the present invention. 
       FIG. 4  an enlarged detail of the toothing of the drive shaft, in cross section. 
       FIG. 5  a plan view of the assembly of a vane-type pump including the toothing according to the present invention between the drive shaft and the rotor. 
   

   DETAILED DESCRIPTION 
   A rotor  1  of a six-vane vane pump having an internal toothing according to the present invention is shown in  FIG. 1 . The rotor includes six slots  3  in which vanes (not shown here) are mounted radially displaceably, and which glide, by their vane tips, along a corresponding lifting ring contour of the vane-type pump. At its center, the rotor includes a toothing having four teeth  7 , which are shown, inwardly from the rotor, having a chamfer. 
   In  FIG. 2 , the rotor toothing is shown in an enlarged detail. The four teeth  7  have flanks  9 , which, in their form, are designed as involute toothing. Tooth roots  13  lead into a root-circle diameter  11 , which is used as an external centering circle between the rotor toothing and the shaft toothing. 
     FIG. 3  shows toothed end  15  of a drive shaft  17 . Toothed shaft end  15  has four teeth  19 , which, axially, have a slightly convex design at tooth tips  21  thereof, which is not readily discernible in the representation. Shaft end  15  terminates in a centering and mounting tip  22 , thereby facilitating mounting of the shaft in the rotor. As is more readily discernible in  FIG. 4 , teeth  19  have a correspondingly large width. 
   In  FIG. 4 , the toothing of the shaft is shown in cross section. The four teeth  19  have a relatively large width, including a tooth tip surface  24 , this surface representing a circular outside diameter which provides for the centering of the rotor on the shaft. At points  25 , circular outside diameter  23  of shaft toothing merges transitionally into an involute tooth flank  27 , which then merges transitionally into a root circle  29  of the toothing. It is clearly discernible that the width of shaft teeth  19  is substantially greater than the width of rotor teeth  7 . This is deliberately intended in accordance with the present invention since, considered in terms of strength, the shaft toothing must both absorb the transversal forces acting on the rotor, as well as introduce the driving torque from the shaft into the rotor. This requires that the shaft, in particular the shaft toothing, have a suitable material cross section. In this regard, it is precisely the absorption of transversal forces that is problematic for known toothings. 
     FIG. 5  shows the assembly of a corresponding vane-type pump  31 . Supported within a pump housing  33  is a lifting contour ring  35 , which is mounted within the housing by a pin  39  in a round bore and by another pin  37  in a slotted bore. Lifting contour ring  35  has a lifting contour  41  which, in this case, is circular; in other cases, for example when working with two-stroke vane pumps, it may also have any given other contour. Six vanes  43 , which are mounted radially slidingly in the slots of rotor  1 , glide with their vane tips along lifting contour  41  and thereby form suction and positive-displacement chambers. The function of a vane-type pump of this kind is known and does not require any further explanation here. Important for the function of the pump in this case is that, due to the position of its pressurized cell, for example cell  45 , as a single-stroke vane pump, the pump produces a radial force  47 , shown here by an arrow, which acts upon the rotor and is transmitted by the rotor toothing to the shaft and must be absorbed by shaft  17 . In the process, the radial force is transmitted via circular toothing surface  11  of the rotor to circular toothing surface  24  of the shaft, these two parts of the toothing form representing an external-diameter centering on the shaft. 
   Another feature of the toothing according to the present invention is that, between teeth  7  of the rotor and teeth  19  of the shaft, a clearance  49  results, which may include an angular region of 3° to 12°, preferably of 6°. The advantage of this clearance is that, when working with minor torsional shocks of the shaft within this clearance region, the torsional shocks are not transmitted to the rotor in a manner that produces positive engagement. The frictional forces occurring between outside diameter  23  of shaft toothing  19  and inside diameter  11  of rotor toothing  7  act in this context as damping forces between the two motions of the rotor and shaft. 
   The approach in accordance with the present invention with regard to this toothing thus provides for combining the advantages of an outside diameter-centered spline shaft connection, of a toothed-shaft connection including involute flanks, of axial convexity of the toothing for preventing angular errors between the rotor and shaft, and of an increased clearance among the tooth flanks. The present invention is especially useful for those pumps which are subject to torsional vibrations due to their mounting location, such as diesel presupply pumps, where the diesel motor produces such vibrations at the drive shaft. The axial convexity of the toothing compensates for any possible skewed position of the rotor relative to the drive shaft which is secured, for example, to a camshaft of the combustion engine. The outside-diameter centering of the toothing on the shaft braces against the transversal forces during operation. This prevents a relative motion of the drive partners along the toothing flanks and thus reduces the wear that the toothing is subject to compared to a conventional toothing. At the same time, the friction present at the outside-diameter centering of the toothing of the drive partners is used for damping of the torsional vibrations. The increased clearance among the tooth flanks permits rotation of the drive partners relative to one another, as well as damping of the effects of the torsional vibrations, due to the friction present at the outside-diameter centering. As a result, contact shocks at the tooth flanks are minimized or eliminated due to torsional vibrations, thereby minimizing wear. 
   The present invention may be used analogously for other pumps as well, such as for gear pumps, for example, where the torque entrainment between the drive shaft and the gear wheel driven by the shaft is also subject to the action of corresponding transversal forces. However, this toothing is likewise advantageous for pumps that are not subject to transversal forces, such as two-stroke vane pumps, since the outside-diameter centering of the shaft toothing and the inside-diameter centering of the rotor provide for a better centering of the shaft than do known toothings. In this case as well, any possible skewed position of the rotor relative to the shaft is able to be compensated by the axial convexity of this toothing according to the present invention. 
   LIST OF REFERENCE NUMERALS 
   
       
         1  rotor 
         3  slot 
         7  teeth of the rotor toothing 
         9  tooth flanks of the rotor toothing 
         11  root-circle diameter of the rotor toothing 
         13  tooth root of the rotor toothing 
         15  toothed end of the drive shaft 
         17  drive shaft 
         19  teeth of the drive shaft 
         21  tooth tips of the drive shaft 
         22  mounting tip of the drive shaft 
         23  outside diameter of the shaft toothing 
         24  tooth-tip surface of the drive shaft 
         25  transition of the shaft toothing into the involute tooth flank 
         27  involute tooth flank of the shaft toothing 
         29  root circle of the shaft toothing 
         31  vane-type pump 
         33  pump housing 
         35  lifting contour ring 
         37  pin for lifting contour ring 
         39  pin for lifting contour ring 
         41  lifting contour of the lifting contour ring 
         43  vane 
         45  cell of the vane-type pump 
         47  radial force acting on the rotor 
         49  clearance between the rotor toothing and the shaft toothing