Abstract:
An assembly comprising a shaft ( 14 ) and a female part ( 6 ) fixed in terms of rotation on the shaft by rotational-fixing means which cooperate through complementary shapes ( 16 ), the female part also being fixed axially on the shaft, and the female part ( 6; 160; 360 ) comprising axial first stops ( 52; 54; 152 ) which cooperate with associated second stops ( 44; 46; 144 ) belonging to the shaft. The first and second stops ( 44; 46; 52; 54; 144; 152 ) act in the direction of mounting. The female part ( 6 ) further comprises first axial-retention surfaces ( 60; 160; 360 ) cooperating with associated second axial-retention surfaces ( 50; 150; 350 ) belonging to the shaft. The first and second retention surfaces ( 50; 60; 150; 160; 350; 360 ) act in the opposite direction to mounting. The invention applies in particular to ball-type constant-velocity joints for motor vehicles.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates generally to a shaft assembly for ball-type constant velocity joints. Ball-type joints are widely used, for example, in the field of motor vehicle wheel shafts. A joint such as this generally comprises a bell socket connected firmly to a first shaft and a central element secured to a second shaft and housed in the bell socket.  
           [0002]    The bell socket and the central element each have six runway tracks distributed at equal angles, on their interior and exterior surfaces respectively. A ball is housed in each pair of tracks so as to transmit torque from the central element to the bell socket and so as to allow the joint to articulate during operation.  
           [0003]    A cage fitted between the bell socket and the central element prevents the balls from escaping. The central element is firmly fixed in terms of rotation on the shaft by associated splined profiles. Axial attachment of the central element is achieved in a first direction by stop surfaces, for example a shoulder of the shaft against which the central element abuts. In the second direction, the central element is retained by a split ring housed in a groove formed in the shaft.  
           [0004]    This conventional assembly has several drawbacks. For example, between the split ring and the central element or between the central element and the stop surfaces there is a clearance which allows the central element a small axial movement. This leads to the generation of noise while the joint is in operation. In order to keep this clearance as small as possible, close tolerances are needed, which is expensive from a manufacturing standpoint.  
           [0005]    In addition, the split rings are relatively complicated to mount and this mounting is difficult to automate because of the precision required in positioning the ring. In addition, in instances where the ring is covered by the central element, there is a problem of groove accessibility at the time of mounting and/or removal.  
           [0006]    Furthermore, because the split ring is located inside the joint, there is problem with accessing this ring when the central element needs to be removed.  
         SUMMARY OF THE INVENTION  
         [0007]    An object of the invention is to provide an assembly which will simply and reliably eliminate any axial play, particularly in the aforementioned application.  
           [0008]    The foregoing and other objects are obtained by an assembly comprising a shaft and a female part which is fixed in terms of rotation on the shaft by rotational-fixing means which cooperate by having complementary shapes. The female part is also fixed axially on the shaft. The female part comprises axial stop means which cooperate with associated stop means belonging to the shaft. The stop means act in the direction of mounting. The female part further comprises axial-retention surfaces cooperating with associated axial-retention surfaces belonging to the shaft. The retention surfaces act in the opposite direction to mounting. The retention surfaces are arranged beyond said associated means in the direction of mounting and cooperate through complementary shapes.  
           [0009]    Another object of the invention is to provide a ball-type joint comprising an assembly as defined hereinabove, and a female part intended to be used as the female part of an assembly as defined hereinabove.  
           [0010]    Other objects and advantages of the invention will become apparent upon reading the following detailed description and appended claims, and upon reference to the accompanying drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    The invention will be better understood from reading the specification which will follow, given solely by way of example with reference to the appended drawings, in which:  
         [0012]    [0012]FIG. 1 is a view in longitudinal section, on two axial half-planes which correspond to the line I-I in FIG. 3, of a ball-type joint comprising an assembly according to a first embodiment of the invention.  
         [0013]    [0013]FIG. 2 shows detail II of FIG. 1, on a larger scale.  
         [0014]    [0014]FIG. 3 is a view from the right of the central element of the joint of FIG. 1.  
         [0015]    [0015]FIG. 4 shows, in detail, and viewed in cross section, an assembly according to a first variant of the embodiment of FIG. 1.  
         [0016]    [0016]FIG. 5 is a view in longitudinal section on two axial half-planes which correspond to the line I-I of FIG. 3, of part of a ball-type joint comprising an assembly according to a second variant of the first embodiment.  
         [0017]    [0017]FIG. 6 is a view in section on VI-VI of FIG. 5.  
         [0018]    [0018]FIG. 7 depicts a detail of an assembly according to a second embodiment of the invention, the view corresponding to FIG. 2 of the first embodiment.  
         [0019]    [0019]FIG. 8 is a view in section on VIII-VIII of FIG. 7.  
         [0020]    [0020]FIG. 9 depicts a detail of an assembly according to a variant of the second embodiment of the invention, the view corresponding to FIG. 2 of the first embodiment.  
         [0021]    [0021]FIG. 10 is a view of a corresponding locking ring.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]    The constant-velocity joint  2  depicted in FIG. 1 consists of two main parts, namely an outer bell socket  4  and a central element  6 . Between the ball socket  4  and the central element  6 , there are six balls  8  (only one of which is visible in FIG. 1) and a cage  10  for keeping the balls in the plane bisecting the joint. When the joint  2  is mounted, the bell socket  4  is secured to a first shaft  12  of axis X-X, and the central element  6  is secured to a second shaft  14  of axis Y-Y. These two axes are coaxial in FIG. 1, in which the joint  2  is aligned.  
         [0023]    The expression “direction of mounting” will refer in what follows to the direction in which the central element  6  is displaced on the second shaft  14  at the time of mounting.  
         [0024]    The bell socket  4  is typically formed integrally with the first shaft  12 , which is a stub axle of a driving wheel. The central element  6  is fixed firmly in terms of rotation to the second shaft  14 , which is a drive shaft, by means which cooperate through having complementary shapes. In this particular instance, these means consist of axial splines  16  provided in the central opening  18  (see FIG. 3) of the central element  6 . The second shaft  14  comprises associated splines  20 .  
         [0025]    The bell socket  4  has a spherical cavity  22  of center O located on the axis X-X. This cavity  22  is open toward said second shaft  14  and in its wall are made six first grooves  24 , distributed at equal angles and each of which is contained in an axial half-plane of the bell socket  4 . Each groove  24  extends on each side of the diametral plane P of the bell socket  4  perpendicular to the axis X-X and opens onto an entry chamfer  30  of the bell socket  4 .  
         [0026]    The central element  6  has a spherical exterior surface  32  of center O in which are formed six second grooves  34  which are distributed at equal angles and each contained in an axial half-plane of the central element  6 . These grooves  34  extend on each side of the diametral plane of the central element  6  which is merged with the plane P when the joint  2  is aligned, and they open onto the two end faces of the central element, namely the socket end  36  and the shaft end  38 .  
         [0027]    The cage  10  comprises exterior and interior spherical surfaces of center O which cooperate respectively with the aforementioned spherical surfaces  22 ,  32  of the central element  6  and of the bell socket  4 . It additionally comprises six slots  40  in each of which one ball  8  is guided in the conventional way. Each ball  8  cooperates with a pair of grooves  24 ,  34 , which form runway tracks.  
         [0028]    Referring in particular to FIG. 2, it can be seen that a bulge  42  connects to the splines  20  of the second shaft  14 , at the shaft end, and forms oblique stop surfaces. These stop surfaces consist, at the spline end, of surfaces  44  at the bottoms of the splines  20  and of the frustoconical surface  46  of the bulge  42  which extends beyond the splines  20 .  
         [0029]    The bulge  42  forms, at the shaft end, oblique axial-retention surfaces  50  located beyond the stop surfaces  44 ,  46  in the direction of mounting.  
         [0030]    As depicted, the retention surfaces may be formed of an annular groove formed in the second shaft  14 .  
         [0031]    At the end facing toward the mounting direction, the splines  16  of the central element comprise chamfers  52  to which a frustoconical surface  54  connects, thus forming stop surfaces that complement those of the second shaft  14 , and which act in the direction of mounting.  
         [0032]    Six fixing tabs  56  project from the shaft-end end face  38  of the central element. They are distributed at equal angles between the second grooves  34  (see FIG. 3) and extend in the direction of mounting. The length of the fixing tabs  56  is chosen such that their ends protrude beyond the bulge  42  of the second shaft  14  when the stop surfaces belonging to the central element and to the shaft are cooperating.  
         [0033]    The radially interior surface  60  of each tab  56  extends, in the unmounted state, parallel to the axis Y-Y of the second shaft  14  and at a distance from this axis which corresponds to the maximum radius of the bulge  42 , as shown in broken line in FIG. 2.  
         [0034]    The central element  6  is mounted on the second shaft  14  as follows:  
         [0035]    The central element  6  is slipped onto the end of the second shaft  14  such that the splines  16 ,  20  of the shaft  14  and of the central element  6  cooperate. The slipping-on movement is continued until the stop surfaces  52 ,  54  of the central element press against the stop surfaces  44 ,  46  of the shaft. In this position, the ends of the fixing tabs  56  of the central element  6  protrude beyond the bulge  42  of the second shaft  14 .  
         [0036]    Next, the ends of the fixing tabs  56  are locally plastically deformed radially inward by a crimping operation, until they press against the retention surfaces  50  belonging to the second shaft  14 .  
         [0037]    Deformation may be performed by any known means, in the hot or in the cold state.  
         [0038]    When mounted, the radially interior surface  60  of each tab end, after folding down toward the axis Y-Y as described above, forms a retention surface pressing, with complementary shape and without axial play, against the retention surface  50  of the second shaft  14 , thus forming retention means acting in the opposite direction to mounting.  
         [0039]    In order to plastically deform the tabs  56 , it is preferable that they not be hardened. However, in order to avoid wear, the runway tracks  34  should be hardened. This situation may be achieved, for example, by local heat treatment of the tracks  34  or by masking the tabs  56  when employing an overall case-hardening process.  
         [0040]    Finally, in the known way, a protective boot  70  is gripped, on the one hand, in a groove  72  belonging to the bell socket  4  and, on the other hand, in a groove  74  formed in the second shaft  14 , by two clamping collars  76 ,  78 , to avoid dirt getting into the joint  2  and to retain the lubricant.  
         [0041]    It is noted that local deformation of zones of small thickness  56  belonging to the central element makes it possible to fix the central element  6  axially onto the shaft  14  in a play-free manner, thus eliminating the generation of noise during operation.  
         [0042]    In addition, this embodiment has the advantage that the number of parts is small, as, consequently, is the cost of manufacture. The fact that the collaboration of the retention surfaces is achieved by plastic deformation avoids the need for close manufacturing tolerances.  
         [0043]    It is to be noted that, as a variant, the central element  6  may have less than six fixing tabs  56 , or alternatively that just some of the six fixing tabs  56 , for example two tabs, are deformed.  
         [0044]    [0044]FIG. 4 depicts a first variant of the fixing of the central element to the shaft. In this variant embodiment of the invention, ribs  80  arranged on the central element  6  and extending substantially axially in the direction of mounting each have two fixing tabs  82 ,  84  projecting roughly circumferentially on their two opposed sides. To fix the central element  6  onto the shaft  14 , the tabs  82 ,  84  are plastically deformed radially inward until they apply on the surfaces  50  of the shaft  14 .  
         [0045]    [0045]FIGS. 5 and 6 depict a second variant of the fixing of the central element  6  on the shaft  14  of the embodiment of FIG. 1.  
         [0046]    At the bottom of each runway track  34  of the central element there is a zone  90  located at the shaft end of this track and which is not loaded by the ball  8  during operation, even when the joint  2  is articulated to its maximum angle. This zone  90  has a small thickness comparable with the thickness of the end of the fixing tab  56  of the central element  6  of FIG. 1, thanks to a counterbore  91 .  
         [0047]    In consequence, the central element  6  has no fixing tabs, but the zones  90  are plastically deformed radially inward and axially fix the central element  6  through being crimped against the surfaces  50 . In order to account for the fact that the deformed zone  90  is displaced axially in the opposite direction to the direction of mounting as compared with the variant of FIG. 1, the bulge  42  of the shaft is shifted and modified accordingly.  
         [0048]    The mounting steps remain similar to those of the variant of FIG. 1.  
         [0049]    It is to be noted that the runway tracks  34  are not hardened in the zone  90  (not loaded by the balls) that is to be deformed.  
         [0050]    [0050]FIGS. 7 and 8 depict a second embodiment of the invention. FIG. 7 corresponds to FIG. 2 of the first embodiment of the invention. The elements which perform functions similar to those of the first embodiment carry the same references increased by 100.  
         [0051]    Each fixing tab  156  belonging to the central element  106  has, on its radially interior surface, a recess  157  extending substantially circumferentially with respect to the axis of the second shaft  114 , in the mounted state. The axial-retention surface  160  is formed by the undercut surface which delimits the recess  157  at its end closest to the end of the fixing tab  156 .  
         [0052]    In contrast to the first embodiment, the fixing tab  156  is not intended to be deformed.  
         [0053]    As previously, the shaft  114  has an annular groove referenced  161 . This groove is directly facing the recesses  157  when the stop surfaces  144 ,  152  of the shaft and of the central element are cooperating. The axial-retention surface  150  of the shaft delimits the annular groove  161  at the same end of the shaft as the splines  120 .  
         [0054]    Collaboration between the axial-retention surface  160  of each fixing tab  156  and the axial-retention surface  150  of the shaft through complementary shapes is achieved indirectly via a locking member  162  which transmits the axial-retention force. The locking member  162  consists of solidified fluid substance, particularly a thermoset material, injected in the fluid state into the empty space between the two retention surfaces  150 ,  160 .  
         [0055]    As a variant, any other appropriate material, such as, for example, brazing filler may be used.  
         [0056]    The central element  106  is mounted on the second shaft  114  in a way similar to that of the first embodiment. However, having slipped the central element  106  onto the shaft  114 , the fluid substance is injected through at least one of the two lateral openings  164 ,  166  of the aforementioned empty space.  
         [0057]    It is seen that this embodiment also allows the central element to be fixed axially onto the shaft easily without axial play.  
         [0058]    [0058]FIG. 9 shows a variant of the second embodiment of the invention. FIG. 9 corresponds to FIG. 7 of the previous variant. The references of the elements which are similar to those of this previous variant are increased by 200.  
         [0059]    The central element  306  comprises fixing tabs  356  with recesses  357  and the shaft  314  has an annular groove  361 , all these features being similar to those of the previous variant.  
         [0060]    However, the locking member is a separate part. This separate part is a strip  362  which in radial cross section is substantially rectangular with rounded corners, complementing the shape of the empty space between the recess  357  and the annular groove  361 . The circumferential dimension of the strip  362  is substantially equal to that of said empty space and to that separating the tabs  356 , and its axial length increases slightly in a circumferential direction, so as to form a wedging surface  363  acting in the axial direction in the mounted state.  
         [0061]    Six strips  362  are connected, by the middle part of their end surface at the shaft end, to form one piece with a ring  365 , as depicted in FIG. 10. The strips  362  are distributed at angles on the ring in a way that corresponds to the fixing tabs  356  of the central element  306 .  
         [0062]    Furthermore, the ring  365  has a split  367  to make it possible to mount it on the shaft.  
         [0063]    In this variant, the central element  306  is mounted on the shaft  314  as follows.  
         [0064]    First, the central element  306  is slipped onto the end of the shaft  314 , as described above, as far as its axial stop.  
         [0065]    Next, the ring  365  is slipped onto the shaft  314  by an axial displacement in such a way that the tabs  356  of the central element  306  are inserted between the strips  362  of the ring  365 , until the strips  362  clip into the groove  361  of the shaft. Because of the split  367  made in the ring  365 , the ring can easily pass over those sections of the shaft  306  which have a diameter greater than its inside diameter at rest, by elastic deformation.  
         [0066]    Next, the ring  365  is rotated with respect to the longitudinal axis of the shaft  314  until the strips  362  are aligned with the fixing tabs  356  of the central element, thus simultaneously through a wedge effect immobilizing all the pairs of retention surfaces  350 / 360 . The ring  365  is locked against rotation by the friction of the strips  362 . It can be locked additionally by welding or bonding.  
         [0067]    It is noted that the retention of the central element on the shaft by retention surfaces which are beyond the stop surfaces allows the attachment free of axial play by using a space available in this region of the joint.  
         [0068]    From the foregoing, it will be seen that there has been brought to the art a new and improved shaft assembly which overcomes the drawbacks associated with prior shaft assemblies. While the invention has been disclosed in connection with one or more embodiments, it will be understood that the invention is not limited to those embodiments. On the contrary, the invention covers all alternatives, modifications, and equivalents as may be included in the spirit and scope of the appended claims.