Abstract:
An axial piston machine, in particular to an air-conditioning compressor for motor vehicles, including a drive unit for taking-in and compressing a pressure medium The drive unit is rotatably driven by a shaft, the rotatable movement of the shaft is convertible into the reciprocating motion of the pistons in the drive unit and the shaft is mounted in the casing of the axial piston machine, in particular by an axial bearing.

Description:
The present invention relates to an axial piston machine, in particular an air-conditioning compressor for motor vehicles, having a drive mechanism for drawing in and compressing a pressurizing agent, the drive mechanism being rotary driven by a shaft and the rotary motion being converted in the drive mechanism to a reciprocating motion of the pistons, and the shaft being supported in part by an axial bearing in a casing part of the axial piston machine. 
     BACKGROUND 
     Such machines are known. The axial forces that occur are supported on the casing through the axial bearing. As a result, pulsations and vibrations are transmitted into the casing through this bearing point, and can then be heard from outside. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to present an axial piston machine that does not have these disadvantages. 
     The present invention provides an axial piston machine, in particular an air-conditioning compressor for motor vehicles, having a drive mechanism for drawing in and compressing a pressurizing agent, the drive mechanism being rotary driven by a shaft and the rotary motion being converted in the drive mechanism to a reciprocating motion of the pistons, and the shaft being supported in part by an axial bearing in a casing part of the axial piston machine, there being according to the present invention a rubberized metal sheet situated between the axial bearing and the contact face of the bearing in the casing as a damping element. 
     The use of a rubberized metal sheet (a metal sheet as a substrate, covered on both sides with a coating of rubber) has the advantage of very flat construction on the one hand and of with-standing high surface pressures continuously on the other hand. A pure elastomer element as a damping element does not withstand the continuous strain from the constantly changing rotating axial forces. The elastic damping of the rubberized metal sheet reduces the external noise of the compressor significantly. 
     Also preferred is an axial piston machine in which a device for articulated (pivoting/rocking) bearing support between shaft and axial bearing is situated between the axial bearing and the contact face of the shaft on the axial bearing. Preferred in addition is an axial piston machine in which the device has a first washer having an axially projecting conical rim and a second washer, which represents a bearing washer of the axial bearing, having a conically beveled edge on the outer circumference, the axially projecting conical rim of the first washer bearing on the conically beveled edge of the second washer in such a way that contact between the first and the second washers occurs only between the two cones, and otherwise an axial intermediate space is formed between the first and second washers. This has the advantage that the cone fulfills the function of a spherical segment surface in simplified form, without high demands on the precision of fabrication. When there is rotating radial flexing of the shaft, the first washer may undergo an angular displacement against the second washer due to a tipping motion, and the axial forces may be transmitted from the shaft to the bearing essentially flatly (all around) via the contact surfaces between the cones (possibly also spherical segments or domed surfaces), despite the angular position. In contrast to a non-articulated axial bearing, which would have a rotating point contact, here a nearly circular ring-shaped pressure line is obtained, which also contributes to more uniform loading of the damping element. Thus the service life of this type of damping device is increased further by this flat transmission of force. 
     Also preferred is an axial piston machine in which the conical angle is in the range of 30 degrees to 60 degrees, preferably 45 degrees. 
     A pump according to the present invention may have an elastomer-coated metal washer, in particular a rubberized metal sheet, used as the damping element. That has the advantage that the construction of the damping element is very flat, and that high surface pressure is made possible by the metal, since the elastomer coating cannot flow away under pressure, as in the case of a pure elastomer element. That makes it possible to achieve a long service life of the damping element. Furthermore, a rubberized metal sheet washer has a multiple damping effect, since the transition from the metal bearing to the first layer of rubber and from the first layer of rubber to the metal sheet and from the metal sheet to the second layer of rubber and from the second layer of rubber again to a part of the bearing permits five impedance jumps, and hence a corresponding suppression of vibration. 
     Therefore an axial piston machine is preferred in which the rubber-coated metal sheet is preferably coated on both sides. An axial piston machine is also preferred in which a plurality of rubberized metal sheet washers are situated one above the other in a so-called sandwich construction. Also preferred is an axial piston machine in which the rubberized metal sheet or sheets have rubber coatings or elastomer coatings of different thicknesses. This has the advantage that different frequencies may be damped by damping elements of differing thicknesses, making it possible for the damping elements to be targeted at the disturbing frequencies. 
    
    
     
       BRIEF DECRIPTION OF THE DRAWING 
       The present invention will now be described on the basis of the figures without being limited thereto. 
         FIG. 1  shows part of an axial piston machine having the corresponding configuration of an axial bearing. 
         FIG. 2  shows the configuration of the axial bearing having a damping element according to the present invention. 
         FIG. 3  shows the sandwich construction of the damping element. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows part of an axial piston machine  1  in cross section. Inside a machine casing  3  a shaft  7  is supported by an axial bearing  9  and a radial bearing  11  in a bearing sleeve  5 , which is situated in machine casing  3 . Shaft  7  is driven via a belt pulley  13  in the belt drive of a combustion engine. Belt pulley  13  is also supported on bearing sleeve  5  by a separate roller bearing  15 . The interior of the axial piston machine is sealed against the atmosphere by a mechanical seal  17 . In drive chamber  18  of the machine, a tiltable drive ring  19  is set in rotary motion by shaft  7 . On tiltable drive ring  19 , piston shoes  21  in turn slide, which perform wobbling motions within reciprocating pistons  23  and thereby convert the rotary motion of shaft  7  into a reciprocating motion of pistons  23 . Pistons  23  are supported inside a cylinder block, and inside cylinder liners situated therein, draw corresponding coolant in through valve devices, compress this coolant, and expel it again through appropriate valve devices. Important for the present invention are a first bearing washer  27  and a second bearing washer  25  in the area of axial bearing  9 . Shaft  7  having an axial shaft collar  29  is supported axially on first washer  27 . As defined herein, collar  29  and washer  27  define an articulated bearing support, which is a separate element from shaft  7  and bearing system  9 . First washer  27  has an axially projecting conical rim  31 , second washer  25  has a conically beveled edge  33 . Conically projecting rim  31  of first washer  27  rests on conically beveled edge  33  of second washer  25  in such a way that contact only occurs between the two cones, and otherwise an intermediate space  35  is formed between the first and second washers. This has the advantage that when a rotating radial flexing of shaft  7  occurs, produced by the rotating forces of the axial piston drive mechanism, the first washer may shift its angle on the cone against second washer  25  due to tilting motions, and the axial forces of shaft  7  may be transmitted to bearing  9  through the contact surfaces between cones  31  and  33  in a flat pattern all around, despite the angular position. First washer  27  is thus able to perform a wobbling motion with respect to second washer  25 . 
       FIG. 2  once again shows, in a cutaway view, the structure of the bearing arrangement, but here in addition with damping element  40 . First washer  27  with conically projecting rim  31  and second washer  25  with conically beveled edge  33  are situated above rolling element  37  of axial bearing  9  from  FIG. 1 . Rolling element  37  continues to run on a lower bearing washer  39 . A damping device in the form of a rubberized metal sheet  40  is now situated between lower bearing washer  39  and a support washer  42 . Damping element  40  is made up here of an elastomer or rubber layer  44  which is vulcanized onto the top of a metal sheet substrate  46 , and a second rubber layer  48  which is vulcanized onto the underside of metal sheet substrate  46 . 
     Thus axial forces and axial vibrations that are fed into the bearing device by way of axial shaft collar  29  must penetrate firstly elastomer layer  44 , secondly metal sheet layer  46  and thirdly second elastomer layer  48 , before they are able to be transmitted through support washer  42  into the compressor casing or bearing sleeve  5  at a contact face  47  of bearing  9 . The present invention therefore consists in damping element  40  being situated in the power flow between drive shaft  7  and machine casing  3  or bearing sleeve  5  in the area of axial bearing  9 . Vibrations that occur are damped first simply by the two elastomer or rubber layers  44  and  48 . The second damping effect comes about through the high impedance jump between rubber and metal (energy is consumed or used when a vibration passes from one material into the other). Rubberized metal sheet  40  has the advantage here of being able to utilize this effect repeatedly, since the first impedance jump occurs from metal bearing washer  39  to rubber layer  44 , the second impedance jump from rubber layer  44  to metal sheet substrate  46 , the third impedance jump from metal sheet substrate  46  to second rubber layer  48  and the fourth impedance jump from rubber layer  48  into support washer  42 . 
     Because of the low construction height of these damping washers  40 , the possibility also exists of a sandwich construction (damping washer  140 , metal washer, again a damping washer  240 , another metal washer, axial bearing, etc.). as shown in  FIG. 3 . This enables the damping effect to be increased still further. It is also possible to use rubber layers  144  and  148  in different thicknesses vulcanized to the top and underside of metal sheet substrate  146  respectively, as shown, order to damp different frequencies. 
     The durability of this type of damping is achieved in particular through the fact that the axial force is transmitted from the shaft through a ring-shaped contact surface in a distributed manner because of the articulated axial bearing support achieved by the two washers  27  and  25 . That prevents partial overloading of damping element  40 , which would come about through a non-articulated bearing system. 
     REFERENCE NUMERALS 
     
         
           1  axial piston machine 
           3  machine casing 
           5  bearing sleeve 
           7  shaft 
           9  axial bearing 
           11  radial bearing 
           13  belt pulley 
           15  roller bearing for belt pulley 
           17  mechanical seal 
           18  drive chamber 
           19  tiltable drive ring 
           21  piston shoes 
           23  pistons 
           25  second bearing washer 
           27  first bearing washer 
           29  axial shaft collar 
           31  axially projecting conical rim 
           33  conically beveled edge 
           35  intermediate space between first and second washer 
           37  rolling element 
           39  lower bearing washer 
           40  rubberized metal sheet 
           42  support washer 
           44  elastomer layer 
           46  metal sheet substrate 
           48  second elastomer layer