Abstract:
A freewheel device includes at least one cage, a plurality of wedging members retained by the cage, and a member having a cylindrical surface which comes into contact with the cage. The cage has an axial portion provided with windows which receive immobilizing members and at least one generally annular and substantially radial portion having a flexing area and a plurality of tongues which are of substantially radial shape in a relaxed state and which flex in an axial direction so that ends of the tongues are in frictional contact with the cylindrical surface so that they are circumferentially and axially connected to the surface.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention concerns freewheel devices. 
     2. Description of the Prior Art 
     Freewheel devices generally include an outer ring provided with a cylindrical inner slideway for cams of the freewheel, an inner ring or a shaft provided with a cylindrical outer slideway for said cams of the freewheel, and a freewheel disposed between the slideway of the outer ring and the slideway of the inner ring or shaft. 
     The freewheel includes a single cage or a double cage consisting of two concentric cages, provided with windows in which are disposed cams which provide a unidirectional coupling between the outer and inner rings by being wedged or by sliding between the two slideways. 
     The cage generally has a radial flank imparting sufficient rigidity to the cage on at least one side. 
     The freewheel is therefore able to transmit a torque between the outer and inner rings in one direction and to allow free rotation in the other direction. 
     To encourage tilting of the cams in the wedging direction, a spring can be provided in the form of a strip exerting on each cam a return torque tending to hold the cams at all times in contact with the slideways. 
     These freewheel devices are used in automobile automatic transmissions in particular. 
     To improve the working of freewheel devices and/or to facilitate their assembly, devices for frictionally linking the outer ring of the freewheel and the cage have been envisaged. 
     The documents FR-A-2 474 121 and EP-A-0 641 948 disclose radially elastic members cut out from the cage and coming into contact with the bore of the outer ring. These devices operate satisfactorily. However, according to the document FR-A-2 474 121, bent strips are used, which must therefore be bent, which is a supplementary operation of non-negligible cost. The strips, because of their small section, are also relatively sensitive to impact, which necessitates a few precautions in connection with packaging and handling them. 
     The cage according to the document EP-A-0 641 948 necessitates a cutting operation on elastic parts which must be performed as a final reworking of the cage when it has already been formed to shape, which increases manufacturing time and leads to a relatively high manufacturing cost. Also, some portions of the cage, especially in the cylindrical part provided with the cam cells, are deformed and the overall rigidity of the cage is degraded, which can compromise correct working of the freewheel in some circumstances. 
     The present invention proposes to solve the problems referred to above. 
     The present invention proposes an economic and reliable freewheel device provided with a cage enabling easy fitting of the freewheel between the slideways and holding the freewheel effectively in that position. 
     SUMMARY OF THE INVENTION 
     The invention therefore proposes a freewheel device including at least one cage, a plurality of wedging members retained by the cage, and a member having a cylindrical surface adapted to come into contact with the cage, which has an axial portion provided with windows adapted to receive immobilizing members and at least one generally annular and substantially radial portion having a flexing area and a plurality of tongues of substantially radial shape in a relaxed state and adapted to flex in an axial direction so that ends of the tongues are in frictional contact with the cylindrical surface so that they are circumferentially and axially connected to the surface. 
     In one embodiment of the invention the flexing area is thinner than the remainder of the substantially radial portion. 
     The flexing area can be near the axial portion, i.e. nearer the axial portion than the free ends of the tongues. The flexing area can be in the immediate vicinity of the axial portion in the radial direction. 
     The flexing area can be radially between the ends of the tongues and the axial part. 
     The tongues can be generally trapezoidal. The cage can be made from sheet-metal, for example from steel plate. 
     In one embodiment of the invention the cage has an L-shaped section with an axial portion and a radial portion. 
     In another embodiment of the invention the cage has a U-shaped section with an axial portion and two radial portions. One radial portion can have a supplementary portion. Both radial portions could have a supplementary portion. 
     The freewheel can further include a spring to encourage tilting of the wedging members. 
     The member is advantageously a bore of an outer ring or an outside surface of an inner ring or a shaft. 
     The tongues can be oblique when mounted. 
     The tongues preferably prohibit by means of wedging effect axial movement in at least one direction relative to the member having a cylindrical surface in contact with the cage. 
     The member advantageously has a bevel at one end of the cylindrical surface. The bevel facilitates mounting the cage on the cylindrical surface. 
     In one embodiment the member has a shoulder at the other end of the cylindrical surface to form an axial abutment for the cage which is therefore retained in one direction by the axial abutment and in the other direction by friction between the free ends of the tongues on the cylindrical surface and the wedging effect of said supplementary portion. 
     The invention also proposes a method of manufacturing a freewheel cage, wherein the flexing area is formed at the same time as the substantially radial portion. 
     The flexing area and the substantially radial portion are advantageously formed in the same operation. 
     Thus the cage is provided with means providing a circumferential and axial friction connection with one of the rings of the freewheel. Those means prevent axial movement of the cage relative to the ring during assembly. 
     The invention will be better understood after studying the following detailed description of a few embodiments of the invention, given by way of non-limiting example only and shown in the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a half-view in axial section of a freewheel device in accordance with one aspect of the invention. 
     FIG. 2 is a perspective view of the cage of the freewheel from FIG.  1 . 
     FIGS. 3 and 4 show details of FIG.  2 . 
     FIG. 5 shows the steps of assembling the cage from FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As can be seen in FIG. 1, the freewheel device  1  has an outer ring  2  with a slideway  3  on the inside surface of its bore, an inner ring  4  with a slideway  5  on its cylindrical outside surface, and a freewheel  6  disposed between the slideway  3  on the inside surface of the outer ring  2  and the slideway  5  on the outside surface of the inner ring  4 . The freewheel  6  includes a row of cams  7  retained by a cage  8  and a spring  9  in the form of a strip for tilting the cam  7  in the wedging direction which wedges the cams  7  between the outer slideway  3  and the inner slideway  5 . 
     On the inside surface of its bore  10  the inner ring  4  has a plurality of teeth  11  which are regularly spaced in the circumferential direction and are intended to transmit a torque to a member represented as a mechanical member, on which the inner ring  4  can be mounted. Similarly, the outer ring  2  has on its outside cylindrical surface  12  a plurality of teeth  13  cooperating, in order to transmit a torque, with a mechanical member, not shown, in which the outer ring  2  could be mounted. The teeth  13  are formed across the entire axial width of the outer ring  2 . 
     To be more precise, the outer ring  2  has two radial surfaces  14  and  15 . On the same side as the surface  14 , the slideway  3 , which is formed by a cylindrical surface, is extended beyond the area in which the cams  7  come into contact and as far as a bevel  16  connecting with the front surface  14 . On the same side as the surface  15 , a shoulder  17  delimits the cylindrical surface of the slideway  3 . The shoulder  17  has a diameter smaller than that of the slideway  3 . The shoulder  17  forms an annular radial surface  18  joined to the cylindrical surface of the slideway  3 . 
     The cage  8  is generally annular and has an axial portion  19  in which windows  20  are formed. The cams  7  are mounted and regularly distributed in the windows  20 . The spring  9  can be in contact bearing engagement with the axial portion  19 . The cage  8  also has a substantially radial portion  21  disposed at the free end of the axial portion on the same side as the surface  14  and a radial portion  22  on the opposite side. The radial portion  22  extends toward the outer ring  2  and has an outside diameter greater than that of the shoulder  17 . The radial portion  22  can therefore come into abutting contact engagement with the radial surface  18  and cannot pass beyond the shoulder  17  in normal use. 
     The substantially radial portion  21  includes an annular base area  21   a  near the axial part  19  and an end area cut into tongues  23  in the direction of the outer ring  2  which, in the assembled state shown in FIG. 1, assumes a slightly flexed, in other words oblique shape, the free ends  23   a  of the tongues  23  being oriented slightly toward the surface  14 . The free ends  23   a  are in contact with the bore of the outer ring  2 , i.e. with a cylindrical surface extending the slideway  3 . 
     A circular groove  24  concentric with the cage  8  is formed in the substantially radial portion  21  and defines an area  25  of reduced thickness, also referred to as a “flexing area”. The flexing area  25  allows the tongues  23  to become slightly inclined relative to a radial plane, by deforming elastically. However, the deformation could be partly plastic. 
     The circular groove  24  is at a radial distance from the free end  23   a  and a radial distance from the axial portion  19 . A circular groove could also be provided in the immediate vicinity of the axial portion  19 , the substantially radial portion  21  being divided into tongues over the whole of its length in the radial direction. 
     In the relaxed state, shown in FIGS. 2,  3  and  4 , the tongues  23  are radial, the free ends  23   a  having a diameter slightly greater than that of the bore in the outer ring  2 , so that on inserting the cage into the outer ring  2 , said free ends  23   a  come into contact with said bore, flex slightly to enter it, and by virtue of their elasticity exert a force tending to move the tongues  23  into a radial plane. 
     As can be seen in FIGS. 2,  3  and  4 , the substantially radial portion  21  is divided into a plurality of tongues  23  of substantially trapezoidal shape. The cage  8  associated with the spring  6  and with the cams  7  is mounted in the outer ring  2  from the same side as the surface  14 . The radial portion  22  is first inserted into the bore of the outer ring  2 , and then the cams  7 . The position of the cage  27  is then that shown in FIG.  5 . The axial movement is continued. The free ends  23   a  of the tongues  23  come into contact with the bevel  16 . Further axial movement deforms the tongues  23 , the area  25  flexing to allow inclination of the tongues  23  in a direction opposite to the axial movement with which the cage is inserted, until the outside diameter of the tongues  23  enables them to enter the bore of the outer ring  2 . The axial movement continues as far as the position  28  of the cage. The radial portion  22  is then abutted against the radial surface  18  of the shoulder  17 , on the opposite side to the substantially radial portion  21 . The free ends  23   a  rub on the bore of the outer ring  2 . Any demounting movement in the direction of the surface  14  would jam the tongues  23  with an immediate axial immobilizing effect. The flexing of the tongues has been intentionally exaggerated in FIG. 5 to show this phenomenon more clearly. 
     The tongues of the cage could of course be directed inward and come into contact with an outside cylindrical surface of an inner ring or a shaft. 
     A cage could equally be used having a single substantially radial portion from which L-shaped section tongues originate. In the case of a U-shaped section cage, like the cage  8 , the other radial portion with no tongues must have some radial play relative to the slideway. The reduction in section in the direction of the axial thickness is provided toward the roots of the tooth-shaped tongues to confer some flexibility on them in the axial direction. The circular groove could be formed in masked time by forming it at the same time as forming the substantially radial portion supporting the tongues. Fabricating the tongues does not entail any supplementary bending operation and is therefore particularly economical. 
     The freewheel device is therefore economical to manufacture, easy to mount between the two rings or in the outer ring, and achieves effective centering of the cage in or around the cylindrical surface with which it cooperates during and after mounting. 
     The freewheel device provides effective retention to the cylindrical surface after mounting, thus avoiding any risk of accidental demounting during handling and transport. The benefit of the effect of axial self-immobilization of the cage in the ring in the direction opposite to the mounting direction is reinforced if said ring has axial abutment means such as a shoulder on the side opposite the entry side of the cage. Once the freewheel is in place, it is immobilized axially by mechanical abutment in the direction of the shoulder and by jamming of the tongues of the cage in the slideway in the direction away from the shoulder. The areas of permanent contact between the cage and the cylindrical surface are suitably distributed, whence effective friction fastening of the cage and the member provided with the cylindrical surface. The cage retains a good geometry and limits deformation of the locking tongues, with no unwanted effects on the other functional portions of the cage, in particular the axial portion provided with windows. 
     Of course, the freewheel device could be equipped with two concentric cages. 
     Without departing from the scope of the invention, the use of a molded plastics material cage instead of a metal cage could be envisaged.