Abstract:
A reciprocating piston machine, such as an air-conditioning compressor for motor vehicles, including a pivot ring and a guide sleeve that is provided axially slidably on a drive shaft and is provided with radially projecting bearing sleeves. The pivot ring and the guide sleeve are interconnected by pins so as to be rotatable relative to each other while being axially joined in a fixed manner, the pins being mounted in bores of the pivot ring and in bores of the bearing sleeves of the guide sleeve.

Description:
The present invention relates to a reciprocating piston machine, such as an air-conditioning compressor for motor vehicles, having a pivot ring and a guide sleeve which is disposed axially slidably on a drive shaft and has radially projecting bearing sleeves, the pivot ring and the guide sleeve being interconnected by pins which are supported, on the one hand, in bores of the pivot ring and, on the other hand, in bores of the bearing sleeves of the guide sleeve in such a way that they are rotatable relative to each other, but are axially “fixed” to each other. 
   BACKGROUND 
   Reciprocating piston machines of this kind are generally known. However, there are some disadvantages associated therewith. For example, the related-art reciprocating piston machines have a one-piece guide sleeve which is manufactured as a lathe-cut part and thus requires a considerable amount of machining. In addition, during operation, these guide sleeves produce traces of wear on the drive shaft of the machine. 
   Moreover, between the bearing sleeves of the guide sleeve and the pivot ring, the known machines have a spherical-segment shaped contact surface, which is expensive to manufacture, but is necessitated by the annular inner circumferential wall of the pivot ring, in order to allow an unhindered motion of the pivot ring relative to the bearing sleeves. 
   Also, in the known machines, the press-fit connection between the pins and the bearing sleeves is disadvantageously configured in the guide sleeve, which can lead to associated tolerance problems. Thus, narrow tolerances are required between the pins and the bearing sleeves due to the coaxiality of the fixed cylinder-pin location holes, and, on the other hand, substantial play is created by the rotatable cylinder-pin location holes in the pivot ring, which can lead to associated noise and vibration problems. 
   SUMMARY OF THE INVENTION 
   It is, therefore, an object of the present invention to devise a reciprocating piston machine which will overcome these disadvantages. 
   The present invention provides a reciprocating piston machine, such as an air-conditioning compressor for motor vehicles, having a pivot ring and a guide sleeve which is disposed axially slidably on a drive shaft and has radially projecting bearing sleeves, the pivot ring and the guide sleeve being interconnected by pins which are supported, on the one hand, in bores of the pivot ring and, on the other hand, in bores of the bearing sleeves of the guide sleeve in such a way that they are rotatable relative to each other, but are axially “fixed” to each other, the guide sleeve having a pot-shaped part, in particular of deep-drawn sheet metal, in which the radially projecting bearing sleeves are inserted in radial bores. Here the advantage is derived that virtually no or only relatively little machining is required to manufacture the guide sleeve. It is thus possible to reduce the cost of component parts. 
   A reciprocating piston machine is preferred in which the material of the pot-shaped part of the guide sleeve is hardened, while the material of the bearing sleeves is not hardened. Here the advantage is derived that the tolerances of the bearing sleeves to be positioned with axial precision are not affected by thermal deformation. 
   A reciprocating piston machine is also preferred in which the pot-shaped part of the guide sleeve and the bearing sleeve are joined together by connection means, in particular by soldering. This advantageously makes it possible for a hardened and an unhardened component part to be united in a simple and reliable manner to form one assembly. 
   The reciprocating piston machine according to the present invention that the pot-shaped part of the guide sleeve may have bushings made of friction-bearing material in the guidance portion on the drive shaft. This advantageously minimizes wear to the shaft, since the hardened guide sleeve no longer executes axial movements on the shaft surface. It is thus possible to reduce wear in the guidance portion of the guide sleeve and the drive shaft. 
   A reciprocating piston machine is also preferred in which a bushing, in particular the bushing on the side where a return spring is located between the guide sleeve and the shaft, is designed as a collared bushing. Here the advantage is derived that this bushing is able to function simultaneously as a limit stop for the return spring, and, consequently, that the return spring, as well, is able to move against an antifriction bearing material while being subject to relatively little wear. 
   In addition, a reciprocating piston machine is preferred in which the bushings are pressed in place into the pot-shaped part of the guide sleeve. Here the benefit is derived of a simple fastening method that does not require any additional connection means. 
   A reciprocating piston machine according to the present invention may have the feature that the contact surfaces between the pivot ring and the bearing sleeves of the guide sleeve are constituted of plane surfaces. In this case, one obtains the advantages of reduced wear and simpler parts manufacturing since the contact surface area is larger than that of bearing sleeve surfaces having a spherical segment shape within an annular inner circumferential wall of the pivot ring. The planar contacting instead of the linear contacting also leads to a more efficient damping of the vibrational response between the pivot ring and the bearing sleeves. 
   A reciprocating piston machine is preferred in which the pivot ring has two flattened wall regions on the annular inner peripheral wall, so that the inner peripheral wall of the pivot ring has the shape of an oval. Thus, the plane contact surface is formed on the pivot ring side. 
   A reciprocating piston machine is also preferred in which, in the unmachined state, the pivot ring is formed as a forged part. The advantage of such a fabrication process is that it economizes on material and does not require a substantial outlay for machining. 
   In addition, a reciprocating piston machine is preferred in which the bearing sleeves each have a plane axial (contact) surface. 
   Another reciprocating piston machine according to the present invention may have the feature that the pins are press-fitted into the bores of the pivot ring and are rotatably supported in the bearing sleeves of the guide sleeve. In this case, the play between the cylinder-pin location hole in the pivot ring and the pins themselves is advantageously avoided, so that the amount of noise and vibration generated may be reduced. 
   Also preferred is a reciprocating piston machine in which the pins are supported by a convex end portion in the bearing sleeves of the guide sleeve. The narrow tolerances necessitated by the coaxiality of the cylinder-pin location holes may advantageously be avoided, since contacting now takes place at the surface area of the convex end portions, making it possible to compensate for angular errors in the axial direction. 
   A reciprocating piston machine is also preferred in which the pins, on the longitudinal sides thereof, have two flattened surfaces which are configured in the pivot ring in such a way that the interference fit between the pins and the pivot ring bores does not deform the sliding-shoe bearing surfaces of the pivot ring. A machine is preferred in which the flattened surfaces of the pins are positioned in parallel to the sliding-shoe bearing surfaces of the pivot ring. This makes it possible to advantageously prevent any warping of the sliding-shoe bearing surfaces when the pins are pressed in place. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention is described in the following with reference to the figures, which show: 
       FIG. 1  a pivot ring assembly including the drive shaft and the guide sleeve in accordance with the related art; 
       FIGS. 2   a  and  2   b  the contact surface between the bearing sleeves and the pivot ring in accordance with the related art; 
       FIGS. 3   a  and  3   b  the contact surfaces between the bearing sleeves and the pivot ring in accordance with the present invention; 
       FIGS. 4   a  and  4   b  a guide sleeve according to the present invention; 
       FIG. 5  a pin according to the present invention for press-fitting into the pivot ring; 
       FIG. 6  the interference fit between the pivot ring and a pin according to the present invention. 
   

   DETAILED DESCRIPTION 
     FIG. 1  illustrates the assembly of a pivot ring machine according to the related art including drive shaft  5 , guide sleeve  9  and pivot ring  1 . In response to rotation of drive shaft  5 , pivot ring  1  is set into rotation by a driving pin  3  which is fixed to drive shaft  5 . In addition, pivot ring  1  has two bores  7  for receiving pins about which the pivot ring is able to execute a rotary motion. Also accommodated on shaft  5  is guide sleeve  9  which has two radially projecting bearing sleeves  11  for receiving the pins. Guide sleeve  9  is slidable on shaft  5 . For this purpose, guide sleeve  9  has a recess  13 , which allows guide sleeve  9  to be supported axially movably on shaft  5  relative to driving pin  3 . Driving pin  3  engages by its upper end in a bore  15  of the pivot ring and allows the pivot ring to execute a pivoting movement to pivot about this upper end of driving pin  3 . Piston shoes for the pistons of the reciprocating piston machine which slide on surfaces  17  and  19  of the pivot ring. In this context, the pins supported inside of pivot ring bores  7  and bearing sleeves  11  form a swivel axis for pivot ring  1  that is displaceable in the axial direction of machine shaft  5 . The function of such a pivot ring drive for reciprocating piston machines is generally known and described in the related art, so that there is no need for further clarification here. 
   In a plan view,  FIG. 2  shows the contact surfaces between pivot ring  1  and bearing sleeves  11  in accordance with the related art. The same components are denoted here by the same reference numerals as in  FIG. 1 . In  FIG. 2   b , guide sleeve  9  and pivot ring  1  are shown in a plan and part-sectional view. It is discernible, in particular in enlarged representations Z of  FIG. 2   a  and X of  FIG. 2   b , that contact surfaces  21  of bearing sleeves  11  contacting pivot ring  1  must have an approximately spherical segment shape, in order not to hinder pivot ring  1 , whose inner circumferential surface is circular, in its rotational and slewing motion and to sufficiently support the same. As may be inferred from enlarged representations Z and X, the contact made between the inner circumference of pivot ring  1  and bearing sleeves  11  is a linear contacting represented by line  20  passing orthogonally through point  22 . It is also expensive and complicated to manufacture the spherical segment-shaped end faces of bearing sleeves  11 . Therefore,  FIG. 3  shows the inventive modification to the contact surfaces between improved pivot ring  23  and improved bearing sleeves  25 . Bearing sleeves  25  now have a plane surface section  27 , while pivot ring  23  likewise has a plane inner peripheral surface at contact surface  27  thereof, inner periphery  29  of improved pivot ring  23  consequently having the shape of an oval. Thus, between pivot ring  23  and bearing sleeves  25 , a planar contacting is provided which, due to the larger area of contact, produces less wear than the linear contacting known from the related art ( FIG. 2 ) and renders possible an improved damping in response to vibrations of the pivot mechanism. Moreover, the contact surfaces of bearing sleeves  25  are simpler and less expensive to manufacture. Thus, the contact surfaces between pivot ring  23  and bearing sleeves  25  are planar in both dimensions, as illustrated by enlarged representations Z and X in  FIGS. 3   a  and  3   b.    
   Two embodiments of the guide sleeve according to the present invention are shown in  FIG. 4 . The guide sleeve has a pot-shaped part  31 , which assumes the function of part  9  of  FIG. 1 , but in this inventive case, is made of deep-drawn sheet metal, for example, and is thus able to be mass-produced at a lower cost. Guide sleeve part  31  is bearing-supported in bores  33  and  35  on shaft  5  of  FIG. 1  and, via these bearings, is slidable on the shaft. A lateral bore  37  in the circumferential wall of guide sleeve part  31  corresponds to bore  13  of guide sleeve  9  of  FIG. 1  and thus creates the clearance space required for driving pin  3  of  FIG. 1  that extends from shaft  5  into bore  15  of pivot ring  1  and is configured not to hinder the axial mobility of guide sleeve  31 . Accommodated in two radial bores  39  of guide sleeve part  31  are two bearing sleeves  41 , which provide guidance for the pins that form a swivel axis for pivot ring  1 . While guide sleeve part  31  may be made of hardened, deep-drawn sheet steel in order to increase strength and reduce wear, bearing sleeves  41  may remain in the unhardened state and are, therefore, not subject to the inherent deformation risks of a thermal treatment process. Bearing sleeves  41  may be fastened in guide sleeve part  31  using connection means, such as soldering. 
   Also introduced into guide sleeve part  31  in  FIG. 4   b  are two bushings made of a friction-bearing material. Thus, for example, bore  33  has a collared bushing  43  inserted therein, which, on the one hand, acts as a friction bearing against shaft  5  and, on the other hand, together with collar  47 , forms a limit stop for a return spring, which, when the compressor is at a standstill, presses the pivot ring into a starting position. Inserted into bore  35  is a second friction-bearing bushing  45 . Wear to the shaft, as encountered in related art methods, is avoided through the use of friction-bearing bushings  43  and  45 . Also discernible in  FIGS. 4   a  and  4   b  is plane contact surface  49  according to the present invention, as already depicted in  FIG. 3  as contact surface  27 . Friction-bearing bushings  43  and  45  may be fastened using joining techniques, such as press-fitting of the same in guide sleeve part  31 . 
   In a perspective view,  FIG. 5  shows one of the two pins  51 , which, together with guide sleeve  9 , form the swivel axis of pivot ring  1  in the pivot ring mechanism. In this context, pins  51  are press-fitted in the pivot ring, into bores  7  of  FIG. 3 , and supported by their spherical segment-shaped end portions  53  in bearing sleeves  25  in  FIG. 3 , respectively  41  in  FIG. 4 . Cylindrical section  55  of pins  51  that is press-fittable in pivot ring  23  into bores  7  thereof has two flat portions  57 , which, in  FIG. 6 , are positioned in pivot ring  23  to extend in parallel to sliding surfaces  59  of pivot ring  23 . Sliding shoes, which are suitably supported in the axially reciprocating pistons of the reciprocating piston machine, glide on sliding surfaces  59  of the pivot ring. In  FIG. 6 , it is discernible that the interference fit between pins  51  and cylindrical end section  55  thereof and pivot ring  23  is only effected at lateral surfaces  61  and, thus, that that area of bore  7  in pivot ring  23  which faces sliding surfaces  59  is not deformed by the pressing in place of pins  51 . Thus, in comparison to the related art, pins  51 , as shown in  FIGS. 5 and 6 , are designed in such a way that the interference fit is shifted from guide sleeve  9  into pivot ring  23 , and a convex contact region is formed between bearing sleeves  25  of guide sleeves  9  and cylindrical pins  51 . Noted advantages are a broadening of tolerances with respect to the pin guidance in bearing sleeves  25  and, at the same time, a reduced play in the entire assembly between guide sleeve  9 , cylindrical pins  51  and pivot ring  23 . These measures result in reduced costs, a simplified assembly and, at the same time, in an improved noise and vibrational response of the pivot ring drive. Cylindrical pins  51  may also be optionally produced using deep-drawn blanks. To facilitate insertion of cylinder pin  51  during the press-fit operation, also discernible in  FIG. 5  in end region  63  is a grooved end section having a slot  65  for positioning pin  51  during assembly to the desired position, as shown in  FIG. 6 . A constricted region  67  between part  53  and cylindrical part  55  provides ease of mobility in the transitional region between bearing sleeves  25  and, respectively  41 , and pivot ring  23  in  FIG. 3 . 
   LIST OF REFERENCE NUMERALS 
     1  pivot ring 
     3  driving pin 
     5  drive shaft 
     7  bore in the pivot ring 
     9  guide sleeve 
     11  bearing sleeve 
     13  recess for driving pin 
     15  bore of the pivot ring for driving pin 
     17  sliding shoe surface of the pivot ring 
     19  sliding shoe surface of the pivot ring 
     20  line of contact between the contact surfaces of the pivot ring and bearing sleeve 
     21  spherical-segment shaped contact surface between the bearing sleeve and the pivot ring 
     22  pass-through point of the linear contacting 
     23  improved pivot ring 
     25  improved bearing sleeve 
     27  plane surface section of the bearing sleeve/contact surface to the pivot ring 
     29  inner periphery of the improved pivot ring 
     31  pot-shaped part of the guide sleeve 
     33  bearing bore for the shaft 
     35  bearing bore for the shaft 
     37  bore for the driving pin 
     39  radial bore for the bearing sleeves 
     41  improved bearing sleeves 
     43  collared-bushing friction bearing 
     45  friction-bearing bushing 
     47  collar of the collared bushing 
     49  plane contact surface of the bearing sleeve 
     51  cylindrical pins 
     53  spherical segment-shaped end part of the cylindrical pins 
     55  cylindrical section of the cylindrical pins 
     57  flat portions of the cylindrical pins 
     59  sliding surfaces of the pivot ring for piston shoes 
     61  lateral surface of pivot ring bore  7   
     63  end region of cylindrical pins  51   
     65  positioning slot of the cylindrical pins 
     67  constricted region of the cylindrical pins