Abstract:
An air-conditioning compressor comprises a shaft rotationally assembled through a casing. A pulley is attached to the compressor by a roller bearing. A torque-transmitting member engages the pulley and the shaft together. Openings are formed between arms of an external torque transmitting part and a bore of an inner ring has a radius such to enable insertion of a crimping tool into the torque-transmitting subassembly to reshape local plastic features for assembly of the torque-transmitting subassembly. The local plastic deformations of the casing interfere with a transverse face of the inner ring, wherein the local plastic deformations are positioned in axial alignment with the empty spaces in at least one relative angular position between the torque-transmitting member and the inner ring.

Description:
CROSS-REFERENCE 
     This application claims priority to a Patent Application filed under the Patent Cooperative Treaty (PCT), application Serial Number PCT/FR2008/050652 filed on 11 Apr. 2008, which claims the benefit of French Patent Application no. 0754932 Filed on 9 May 2007, the contents of both of which are incorporated by reference as if fully set forth herein. 
     FIELD OF THE INVENTION 
     The present invention relates to the field of air-conditioning compressors for motor vehicles. 
     BACKGROUND OF THE INVENTION 
     In air-conditioning compressor drive devices it is possible to use electromagnetic clutches. In other scenarios, the pulley actuated by a drive belt drives the compressor shaft via a drive plate. A mechanical “fuse” may be interposed between the pulley and the compressor shaft that is to be driven, so that if excess high torque, for example caused by compressor seizure, occurs, the pulley can continue to turn. Should the pulley become jammed, the belt would begin to slip on the pulley, and this would soon lead to the destruction of the said belt. Other components also driven by the said belt would then experience a loss of drive. This type of device is described notably in document U.S. Pat. No. 6,332,842. 
     However, it is necessary to mount the rolling bearing equipped with its pulley on the compressor shaft, then to mount a circlip which axially secures the rolling bearing to the shaft, into a groove machined in the shaft and then finally to mount the drive plate. The number of operations performed at the premises of the manufacturer of the compressor is therefore high. What is more, it is difficult to automate these operations as this results in high costs. 
     The invention sets out to address the above-mentioned disadvantages. 
     The invention proposes an air-conditioning compressor that entails a low number of operations with a view to assembling it, it being possible for these operations to be automated. 
     The air-conditioning compressor is provided with a casing, with a shaft able to rotate about an axis, and with a torque-transmitting device comprising a pulley, a rolling bearing positioned inside the pulley and a torque-transmitting member. The rolling bearing comprises an inner ring, an outer ring, and at least one row of rolling elements. The torque-transmitting member comprises an external part angularly connected to the pulley, an internal part fixed to the shaft and at least two spokes or arms connecting the external part and the internal part. Empty spaces are formed between the arms. The bore of the inner ring has a radius greater than the distance between the axis of rotation and an internal end of the said empty spaces so as to allow the insertion of a crimping tool. Local plastic deformations of the casing interfere with a transverse face of the inner ring. The local plastic deformations are positioned in axial alignment with the said empty spaces in at least one relative angular position between the torque-transmitting member and the inner ring. 
     The plastic deformations may be obtained at low cost. The plastic deformations may be angularly separated from one another. 
     In one embodiment, the arms have a small-section region intended to break in the event of a torque higher than a threshold value. The small-section regions may be positioned in close proximity to the internal part and have an axial thickness less than that of the remainder of the arms. The small-section regions may be obtained by circular knurling of a radial part. 
     In one embodiment, the external part comprises a plurality of axial fingers. An angularly elongate elastic sleeve may be positioned around at least one finger. The sleeve enables damping of the angular movement of the pulley with respect to the plate. The said sleeve may be mounted in an opening of the external part of the pulley. The sleeve may be provided with a hole that forms a housing for a finger. The hole may be provided at unequal distances from the lateral edges of the sleeve in order to encourage damping in the direction in which torque is transmitted. 
     One method of assembling an air-conditioning compressor may comprise the following steps:
         an assembly comprising a pulley, a rolling bearing positioned in the pulley and comprising an inner ring, an outer ring and at least one row of rolling elements, and a torque-transmitting member comprising an external part angularly connected to the pulley, an internal part and at least two arms connecting the external part and the internal part is mounted on a compressor shaft, empty spaces being formed between the arms, the bore of the inner ring having a radius greater than the distance between the axis of rotation and an internal end of the said empty spaces,   the inner ring is crimped onto a compressor casing by inserting a crimping tool between the arms of the torque-transmitting member, the said tool being equipped with several axial teeth that enter the empty spaces formed between the arms and form punches upsetting the material of the casing against the transverse face of the inner ring in an axial movement.       

     The assembly may be manufactured at a first industrial establishment then delivered to a second industrial establishment which mounts the assembly on a driven machine, for example a compressor. The assembly is mounted through an axial movement of the said assembly with respect to the compressor shaft and casing, then by a crimping tool which crashes a non-rotating part, for example a rim of a casing, against the inner ring of the rolling bearing. 
     In one embodiment the step of mounting the assembly on a compressor shaft comprises fitting the inner ring onto the shaft. The fit may or may not be a tight fit. 
     In one embodiment, the inner ring is fitted using a tool that acts as a push rod pressing against a transverse face of the inner ring, by entering via the said empty spaces. 
     In one embodiment, the crimping tool and the fitting tool are coaxial. 
     The pulley/bearing/torque-transmitting member assembly can be handled with a low risk of loss of parts and can be mounted on a support very simply. In the assembled state, the said assembly limits the torque transmitted, damps vibrations and ensures continuity of operation of the pulley in the event of excessive torque insofar as the pulley is supported by the rolling bearing. After the torque-transmitting member which acts as a mechanical “fuse” has broken, the pulley can continue to turn. Other components driven by the belt in contact with the pulley can continue to operate normally. The rolling bearing centres the pulley and allows it to turn. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be better understood from reading the description of a few embodiments, which are given solely by way of entirely nonlimiting examples, and which are illustrated in the attached drawings: 
         FIG. 1  is a rear elevation of the assembly according to a first embodiment; 
         FIG. 2  is an axial section through the assembly of  FIG. 1 ; 
         FIG. 3  is a front elevation of the assembly of  FIG. 1 ; 
         FIGS. 4 and 5  are partial axial sections of the assembly of  FIG. 1  in the process of being assembled; 
         FIG. 6  is a front elevation of the assembly tool used in  FIGS. 4 and 5 ; 
         FIG. 7  is a side elevation of the assembly tool of  FIG. 6 ; 
         FIG. 8  is a front elevation of a combined assembly tool; and 
         FIG. 9  is a side elevation of the assembly tool of  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In  FIGS. 1 to 5 , the torque-transmitting device  1  is mounted on a compressor  2  comprising a non-rotating casing  3  and a shaft  4  able to rotate about a geometric axis  5 . The shaft  4  may be provided with a stepped end  4   a  ending in a threaded portion  4   b  so that it can collaborate with a nut  6 . 
     The torque-transmitting device  1  comprises a pulley  7 , a rolling bearing  8  and a torque-transmitting plate  9 . The pulley  7  comprises an annular peripheral part  10  offering an exterior surface  10   a  intended to collaborate with a belt, not depicted, a bore  10   b  and two lateral radial surfaces  10   c  and  10   d . The exterior surface  10   a  may be provided with annular ribs to collaborate with a belt of the poly-V type for example. The pulley  7  comprises an annular central part  11  coaxial with the peripheral part  10  and comprising an exterior surface  11   a , a bore  11   b  and two lateral radial surfaces  11   c  and  11   d . The bore  11   b  may take the form of annular ribs. The lateral radial surfaces  11   c  and  11   d  may respectively be set back relative to the lateral radial surfaces  10   c  and  10   d.    
     The pulley  7  also comprises a connecting part  12  positioned between the peripheral part  10  and the central part  11 . The connecting part  12  may be set back very slightly with respect to the radial surfaces  10   c  and  10   d  of the peripheral part  10 . The peripheral part  10 , the central part  11  and the connecting part  12  may be of one piece, for example cast as one. The pulley  7  may be made of resin, for example a polyamide resin, a phenolic resin or alternatively polyurethane. 
     The connecting part  12  may comprise a radial central disc  12   a  and a plurality of stiffening ribs  12   b  perpendicular to the disc  12   a  and extending, widening axially, from the central part  11  to the peripheral part  10 . Furthermore, a plurality of holes  13  are formed in the disc  12   a . The holes  13  may be provided between two ribs  12   b  and extend radially over all or part of the height of the disc  12  between the peripheral part  10  and the central part  11 . In the embodiment depicted, there are three ribs  12   b  situated between two holes  13 . The holes  13  may be six in number. The ribs  12   b  may be symmetric with respect to a radial plane perpendicular to the axis  5 . 
     The rolling bearing  8  comprises an inner ring  14 , an outer ring  15 , at least one row of rolling elements  16 , a cage  17  to maintain the even circumferential spacing of the rolling elements  16  and two seals  18  and  19 . The inner ring  14  comprises an axisymmetric exterior surface  14   a , a bore  14   b  in contact with an axial surface  2   a  of the casing  2  and two lateral radial surfaces  14   c  and  14   d , the lateral surface  14   d  being in contact with a radial surface  3   b  of the casing  3 , for example a shoulder. A raceway  14   e  of toroidal shape is formed by machining from the exterior surface  14   a . The exterior surface  14   a  is in rubbing contact with the seals  18  and  19 . 
     The outer ring  15  comprises an exterior surface  15   a , a bore  15   b  and two transverse radial surfaces  15   c  and  15   d  aligned respectively with the radial surfaces  14   c  and  14   d . The radial surfaces  15   c  and  15   d  may be set back from the radial surfaces  11   c  and  11   d  of the central part  11 . A raceway  15   e  is formed by machining from the bore  15   b . The raceway  15   e  is of toroidal shape. 
     Rolling elements  16 , for example balls, are positioned between the raceways  14   e  and  15   e  of the inner  14  and outer  15  rings. Annular grooves are formed from the exterior surface  15   a  of the outer ring  15  to complement the shape of the ribs of the bore  11   d  of the central part  11  of the pulley  7 . In other words, the interior surface  11   b  of the pulley  7  and the exterior surface  15   a  of the rolling bearing  8  have mating shapes. The pulley  7  may be overmoulded onto the outer ring  15  of the rolling bearing  8 . This results in excellent cohesion between these two parts. The seals  18  and  19  may be force-fitted into grooves formed from the bore  15   b  and near the radial surfaces  15   c  and  15   d  of the outer ring  15 . 
     The casing  2  illustrated in  FIGS. 1 ,  2  and  4  is in an intermediate state of assembly in which definitive attachment of the inner ring  14  of the rolling bearing  8  to the said casing  2  has not yet been performed. 
     The torque-transmitting plate  9  is in the form of a one-piece component which may be made of a synthetic material or alternatively may be made of light alloy. The plate  9  comprises a small-diameter sleeve  20  mounted on the end  4   a  of the shaft  4 , having a diameter smaller than the remainder of the shaft  4  so that the sleeve  20  can be clamped between a shoulder and the nut  6  which may be supplemented by a washer. The plate  9  comprises a plurality of radial arms  21  extending outwards from an axial end of the small-diameter sleeve  20  in proximity to the nut  6 . From the free end of the arms  21 , the plate  9  comprises a plurality of fingers  22  of cylindrical overall shape running parallel to the axis  5 . The arms  21  leave wide openings  23  or empty spaces between them. In this instance, there are six of these empty spaces  23  distributed uniformly around the plate  9  in the circumferential direction. At their small-diameter and large-diameter ends, the arms  21  meet in a small-diameter annular portion  24  and in a large-diameter annular portion  25 . The empty spaces  23  run radially between the large-diameter annular portion  25  and the small-diameter annular portion  24 . Formed on the outer edge of the small-diameter annular portion  24  is a cut  26  of circular shape, allowing a small-thickness portion  27  to remain, this portion being liable to break if excess torque is transmitted by the plate  9 . The cut  26  may be formed from the face of the plate  9  opposite to the sleeve  20  and to the fingers  22 . 
     The torque-transmitting device  1  further comprises a plurality of damping pads  28  positioned in the holes  13  around the fingers  22 . In other words, the fingers  22  may be surrounded by the pads  13  which form a vibration damper to damp vibrations between the pulley  7  and the plate  9 . The pads  28  may be made of a resilient material, for example one based on elastomer. The pads  28  may be positioned between the exterior surface  11   a  of the central part  11  and the bore  10   b  of the peripheral part  10  of the pulley  7 . The pads  28  may be positioned between two ribs  12   b  of the connecting part  12 . The pads  28  may have an angular dimension that exceeds their radial dimension in order to provide good damping in the angular direction. Holes  29  are formed in the pads  28  for the fingers  22 . The holes  29  may be cylindrical and parallel to the axis  5 . 
     The torque-transmitting device  1  comprising the pulley  7 , the rolling bearing  8 , the plate  9  and the pads  28  forms an assembly that can be handled with very low risk of loss of components and can then be mounted on a component that is to be driven, for example an air-conditioning compressor, the inner ring  14  of the rolling bearing  8  coming up against an axial exterior surface of a casing while the bore of the small-diameter sleeve  20  of the plate  9  may come up against an axial exterior surface of a rotating part, for example a shaft. Attachment to the shaft may be performed using the nut  6 . Attachment to the casing  2  may be performed by upsetting material with a view to forming a plurality of localized bulges  30  that can be seen in  FIGS. 3 and 5 . The bulges  30  result from plastic deformations caused to the end of the casing  3 , causing outward expansion of an axial exterior surface  3   a , from a radial transverse surface  3   c  of the said casing  3 . The axial length of the exterior surface  3   a  may be slightly greater than the axial length of the inner ring  14  so that the transverse surface  3   c  of the casing  3  is offset from the transverse surface  14   c  of the inner ring  14 , making it possible to have enough material to deform to form the bulge  30 . 
     The bulge  30  is situated at a radial distance from the geometric axis  5  that is greater than the minimum distance between the empty spaces  23  and the said geometric axis  5 . Further, the bulges  30  are preferably angularly distributed about the geometric axis  5  in exactly the same way as the angular distribution of at least some of the empty spaces  23 . The bulges  30  can thus be seen in  FIG. 3  through the empty spaces  23 , the torque-transmitting plate  9  being mounted on the pulley  7 . As may also be seen in  FIG. 3 , the bore  14   b  of the inner ring  14  has a radius greater than the distance between the geometric axis  5  and the internal end  23   a  of the empty spaces  23  formed in the annular radial part of the torque-transmitting plate  9 . In other words, the internal end  23   a  of each empty space  23  is inwardly radially offset towards the axis  5 , with respect to the bore  14   b  of the inner ring  14 . 
     More specifically, the bore of the axial exterior surface  3   a  of the casing  3  has a radius greater than the distance between the geometric axis  5  and the internal end  23   a  of the empty spaces  23 . The internal end  23   a  of the empty spaces  23  is therefore offset radially inwards with respect to the bore of the axial exterior surface  3   a  of the casing  3 . The internal edges  23   a  of the empty spaces are therefore situated at a distance from the axis of rotation  5  that is less than the radius of the bore of the axial exterior surface  3   a.    
     The holes  29  of the elastic sleeves  28  may have a diameter in the free state that is slightly smaller than the diameter of the fingers  22  of the torque-transmitting plate  9  so that the said fingers  22  are mounted into the holes  29  forcibly, thus ensuring mutual axial retention of the torque-transmitting plate  9  with respect to the sleeve  28  and to the pulley  7 . This then yields an assembly that can be handled with low risks of loss of parts with a view to mounting it on a component, for example an air-conditioning compressor. 
     Mounting can be done as follows. The assembly comprising the pulley  7 , the rolling bearing  8  and the torque-transmitting plate  9  is brought through an axial movement towards the casing  3  and the shaft  4  of the driven component. The inner ring  14  of the rolling bearing  8  is fitted onto the exterior surface  3   a  of the casing  3  until it comes into abutment against an annular radial bearing surface  3   b  provided for this purpose. At the same time, the sleeve  20  of the torque-transmitting plate  9  is mounted around the end  4   a  of the shaft  4 . The nut  6  is then screwed onto the threaded part  4   b  of the shaft  4 , thus immobilizing the torque-transmitting plate  9 . The state thus obtained is illustrated in  FIG. 2 . 
     The bulges  30  are then formed, see  FIGS. 4 and 5 , by deforming the free end of the casing  3 , particularly by upsetting some of the material that forms the radial end surface  3   c  of the said casing  3  in close proximity to the exterior surface  3   a  in order to cause the material to flow towards the transverse face  14   c  of the inner ring  14  and slightly radially outwards, thus causing an interference in shape preventing the inner ring  14  from moving axially with respect to the casing  3 . 
     The crimping step may be performed using a crimping tool  31  illustrated in  FIGS. 6 and 7 , comprising an annulus  32  supporting a plurality of axial teeth  33  or punches extending on one and the same side of the annulus  32 . The teeth  33  may have a radial free end  33   a . The teeth  33  may be positioned at a distance from the geometric axis  5  such that the end surface  33   a  interferes with the end surface  3   c  of the casing  3 . The teeth  33  enter the empty spaces  23  formed in the torque-transmitting plate  9 , see  FIGS. 2 and 4 , then come into contact with the free end of the casing  3 , see  FIG. 5 , and cause the material to flow outwards, thus forming the bulges  30 . 
     In the embodiment illustrated in  FIGS. 8 and 9 , a combined fitting and crimping tool is provided which comprises an internal part formed of a crimping tool  31  identical to that of the preceding embodiment, and an external tool  34  comprising an annulus  35  and a plurality of axial teeth  36  or push rods of a length that slightly exceeds the teeth  33  and which are positioned on the exterior surface of the said teeth  33 . The teeth  36  have a radial end surface designed to press against the radial surface  14   c  of the inner ring  14  of the rolling bearing  8  in order to fit the said inner ring  14  onto the exterior surface  3   a  of the casing  3 . The external tool  34  can thus be actuated first of all for the push-fit, then the internal tool  31  is actuated in turn and moved in an axial movement to crimp the inner ring  14  of the rolling bearing onto the casing  3 . 
     By virtue of the invention, there is no longer any need to use circlips for the axial retention of the rolling bearing or to machine the circlip groove in the casing. The operation of mounting the assembly on the component that is to be driven, which operation is performed at the premises of the equipment manufacturer, then becomes very simple and can easily be automated. It simply amounts to operating two tools with axial fingers in an axial translational movement. This then provides a significant reduction in the costs of mounting a driven component, notably an air-conditioning compressor, in a motor vehicle.