Abstract:
This transmission joint comprises a first and a second rotary member, a boot ( 7 ) connected by a front end region to the first rotary member and by a rear end region ( 33 ) to the second rotary member ( 6 ), and means for axially retaining the rear end region of the boot with respect to the second rotary member which comprise a retaining enlargement ( 20 ) and a groove ( 38 ) for housing the retaining enlargement, the rear end region ( 33 ) of the boot and the second rotary member having matching transverse outlines of which the directrix curves exhibit points of inflection. The enlargement is situated on the periphery of the second rotary member and spaced axially from the front end ( 22 ) of the second rotary member, and the groove ( 38 ) is formed on the periphery of the boot.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a transmission joint of the type comprising a first and a second rotary member, a boot connected by a front end region to the first rotary member and by a rear end region to the second rotary member, and means for axially retaining the rear end region of the boot with respect to the second rotary member which comprise a retaining enlargement and a groove for housing the retaining enlargement, the rear end region of the boot and the second rotary member having matching transverse outlines of which the directrix curves exhibit points of inflection. 
     The invention applies in particular to tripot constant-velocity transmission joints. 
     Such joints allow a rotary movement to be transmitted between a first shaft bearing a male element or tripod and a female element or bell housing which rotates as one with, for example, the output side gear of a differential. 
     The tripod has three arms each bearing a rolling assembly. Each rolling assembly is intended to roll on a pair of tracks formed in the bell housing. The tripod and the bell housing have ternary symmetry. 
     The rear end region of the boot is slipped over a front end region of the bell housing. 
     The bell housing is produced in particular by forging and, in cross section, has, in alternation, convex parts and concave or flat parts. The terms “convex” and “concave” are to be understood as meaning with respect to the outside of the bell housing. The convex parts are farther from the longitudinal axis of the bell housing than the concave or flat parts. 
     The groove that houses the retaining enlargement is therefore made in each of the convex parts from the radially outer surface of the bell housing. The retaining groove therefore extends discontinuously around the periphery of the bell housing. 
     The enlargement extends peripherally in a corresponding way on the radially inner surface of the boot. 
     A clamping member clamps the rear end region of the boot onto the front end region of the bell housing, holding the retaining enlargement inside the housing groove. 
     The housing groove is generally formed in the bell housing by turning. Because of the discontinuous nature of the groove, such a machining operation poses numerous problems including relatively high wear of the cutting tool used, and the difficulty of producing a groove whose various portions are concentric. 
     Furthermore, the number of portions of the housing groove and their angular extent depends on the number of convex parts of the bell housing and on their angular extent. 
     Thus, the total angular extent of the retaining housing groove may be relatively small and the axial retention of the rear end of the boot with respect to the bell housing may therefore not be satisfactory. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to solve these problems by providing a transmission joint of the aforementioned type that makes it possible to limit the difficulties of machining the bell housing and to increase the angular extent of the groove that houses the retaining enlargement for a given transverse profile of bell housing. 
     To this end, the subject of the invention is a transmission joint of the aforementioned type, characterized in that the enlargement is situated on the periphery of the second rotary member and spaced axially from the front end of the second rotary member and in that the groove is formed on the periphery of the boot. 
     According to particular embodiments, the transmission joint may include one or more of the following features, taken in isolation or in any technically feasible combination: 
     the retaining enlargement and the groove that houses the retaining enlargement have roughly matching longitudinal profiles, 
     the retaining enlargement extends discontinuously around the periphery of the second rotary member, 
     the retaining enlargement comprises several portions spaced roughly regularly about the periphery of the second rotary member, 
     the groove that houses the retaining enlargement extends around the periphery of the boot in a similar way to the retaining enlargement around the periphery of the second rotary member, 
     the boot comprises sealing means located axially on the same side with respect to at least part of the groove that houses the retaining enlargement, 
     the sealing means are located axially on the same side with respect to the entirety of the groove that houses the retaining enlargement, 
     the sealing means are located axially to the rear of said part of or the entirety of the groove that houses the retaining enlargement, 
     the sealing means are located radially on the same side of the boot as the housing groove, 
     it comprises a member for clamping the rear end of the boot onto the second rotary member, 
     the clamping member is located axially, with respect to at least part of the groove that houses the retaining enlargement, on the same side as the boot sealing means, 
     the retaining enlargement is situated on a radially outer surface of the second rotary member and in that the housing groove is formed on a radially inner surface of the boot, 
     the retaining enlargement is formed on the second rotary member by upsetting the material of the second rotary member. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be better understood from reading the description which will follow, given merely by way of example and made with reference to the appended drawings in which: 
     FIG. 1 is a longitudinal diagrammatic view in partial section of a transmission joint according to the invention, 
     FIG. 2 is a front view illustrating the transverse profile of the bell housing of the joint of FIG. 1, 
     FIGS. 3 to  5  are enlarged diagrammatic part views in section on III—III, IV—IV and V—V, respectively, of FIG. 2, 
     FIG. 6 is a view similar to FIG. 2 illustrating another embodiment of the transmission joint of FIG. 1, and 
     FIGS. 7 and 8 are enlarged partial diagrammatic views in section respectively on VII—VII and VIII—VIII of FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 illustrates a tripot constant-velocity joint  1 . 
     This joint  1 , with ternary symmetry about an axis X—X in its aligned position depicted in FIG. 1, essentially comprises: 
     a male element or tripod  3  comprising three arms  4  distributed angularly 120° apart and each bearing a rolling assembly  5 , 
     a female element or bell housing  6 , and 
     an elastic boot  7 . 
     The tripod  3  is borne by a rotary shaft  8 . 
     The bell housing  6  comprises a body  10  extended to the rear (to the right in FIG. 1) by a shank  11  intended to be connected, by splines  12 , for example, to the shaft of an output side gear of a differential, not depicted. 
     The body  10  comprises a bottom end  13  which bears the shank  11  and which is extended forward by a sidewall  14 . 
     As can be seen in FIG. 2, the wall  14  has a cylindrical transverse outline with respect to the longitudinal axis X—X of the bell housing  6 , whose directrix curve exhibits points of inflection. Thus, the wall  14  has six convex parts  16 , three concave parts  17  and three flat parts  18 . 
     The terms “convex” and “concave” are to be understood as meaning with respect to the outside of the bell housing  6 . 
     The exterior transverse outline of the convex parts  16  over most of the axial length of the wall  14  is depicted in dotted line in FIG.  2 . 
     The convex parts  16  are distributed at regular angles about the longitudinal axis X—X. These convex parts  16  are joined together alternately by the convex parts  17  and flat parts  18 . 
     Each convex part  16  is farther from the longitudinal axis X—X of the bell housing  6  than the concave parts  17  and flat parts  18 . 
     The convex parts  16  connected by one and the same flat part  18  internally delimit a pair of tracks  19  on which a rolling assembly  5  is intended to run. 
     A discontinuous peripheral enlargement  20  of axis X—X projects from the radially outer surface  21  of the sidewall  14  of the bell housing  6 . The enlargement  20  is spaced axially a short distance away from the front edge face or end  22  of the bell housing  6 . 
     The enlargement  20  has a portion  23  at each convex part  16 . 
     The enlargement  20  is interrupted at each concave part  17  or flat part  18  of the sidewall  14  of the bell housing  6  as can be seen in FIGS. 2,  4  and  5 . The top  24  of this enlargement  20  belongs to a cylinder of circular cross section and axis X—X. 
     As illustrated by FIG. 3, the front flank  25  of each portion  23  of the enlargement  20  is orthogonal to the axis X—X and the rear flank  26  of each portion  23  of the enlargement  20  is inclined with respect to the radial direction, outward and toward the front of the bell housing  6 . 
     Each front flank  25  of a portion  23  has a greater radial extent than the rear flank  26  of the same portion  23 . Each front flank  25  is connected to the front edge face  22  of the bell housing  6  by, in succession, a region  27  of the surface  21 , with generatrices parallel to the axis X—X, and a chamfered region  28  which is inclined with respect to the axis X—X forward and toward the inside of the bell housing  6 . 
     The six chamfered regions  28  located forward of the portions  23  of the enlargement  20  are distributed at regular angles about the axis X—X. 
     The bell housing  6  has been produced by forging, and then the chamfered regions  28  have been machined by turning and the portions  23  of the enlargement  20  formed by upsetting material toward the rear of the bell housing  6 . The regions  27  of the radially outer surface  21  have been formed during this upsetting. The front edge face  22  can remain, that is to say undergo no subsequent machining operation. 
     As can be seen in FIG. 1, a front end region  30  of the boot  7  is fixed to the first shaft  8 , some distance from the tripod  3 , by a clamping collar  31 . 
     In a rear end region  33 , the boot  7  has an internal cross section of a shape which in general matches that of the radially outer surface  21  of the sidewall  14  of the bell  6 . 
     The rear end region  33  of the boot  7  is slipped over a front end region  34  of the bell housing  6  which comprises the retaining enlargement  20 . 
     As can be seen in FIGS. 3 to  5 , the rear end region  33  of the boot  7  comprises, in succession, from the rear edge face or end  35  of the boot  7 , two peripheral and continuous sealing lips  37  which extend radially inward around the entire periphery of the boot  7 , and a peripheral groove  38  for housing the enlargement  20  of the bell housing  6 . 
     The groove  38  extends peripherally around the boot  7  In a similar way to the enlargement  20  around the periphery of the bell housing  6 . Thus, the groove  38  has several portions  39  regularly angularly spaced apart. 
     The longitudinal profile of the radially inner surface of the boot  7  near the groove  38  is, except as far as the sealing lips  37  are concerned, a match for that of the radially outer surface  21  of the bell housing  6  near the enlargement  20 . 
     Thus, the groove  38  has a bottom  42 , a front flank  43  and a rear flank  44  which are of shapes which match those of the top  24 , the front flank  25  and the rear flank  26  of the enlargement  20 , respectively, and which are pressed against these. 
     Furthermore, a region  46  of the radially inner surface of the boot  7  is pressed against the region  27  of the radially outer surface  21  of the sidewall  14  of the bell housing  6 . 
     The radially outer surface of the rear end region  33  of the boot  7  exhibits approximate symmetry of revolution about the axis X—X and, axially to the rear of the bottom  42  of the groove  38 , has a groove  49  for housing a clamping collar  50 . This clamping collar  50  extends axially over the sealing lips  37 . The clamping collar  50  is housed with a small amount of axial clearance in the groove  49 . 
     The seal between the rear end region  33  of the boot  7  and the front end region  34  of the bell housing  6  is provided satisfactorily by the lips  37  which are compressed around the entire periphery of the radially outer surface  21  of the bell housing  6  by the clamping collar  50 . 
     Furthermore, the rear end region  33  of the boot  7  is retained axially in both axial directions with respect to the bell housing  6  by the enlargement  20  and the retaining groove  38 . 
     It will be noted that the axial extent of the clamping collar, although limited, provides satisfactory retention of the boot  7  with respect to the bell housing  6  by virtue of the enlargement  20  and of the groove  38 . 
     What is more, the machining to be performed on the bell housing  6  to allow this axial retention of the boot  7  with respect to the bell housing  6  is relatively simple to perform and the tools used are damaged relatively little. 
     It is interesting to note that the chamfered regions  28  from which the enlargement  20  is formed by upsetting the material of the bell housing  6  are surfaces which are usually machined on the bell housings  6  of tripot joints  1  to center the bell housing  6  during finishing by rolling the splines  12  of the shank  11  of this bell housing  6 . 
     In the embodiment of FIGS. 1 to  5 , the enlargement  20  has as many portions  23  as the sidewall  14  of the bell housing  6  has convex parts  16 . The total angular extent of the enlargement  20  therefore corresponds to the total angular extent of these convex parts  16 . However, as will now be described with reference to FIGS. 6 to  8 , it is possible to produce a retaining enlargement  20  whose total angular extent is greater than the total angular extent of the parts  16  of the sidewall  14  farthest from the longitudinal axis X—X of the bell housing  6 . 
     FIG. 6 illustrates a bell housing  6  which differs mainly from that of FIGS. 1 to  5  in that the enlargement  20  that retains the boot  7  comprises nine portions  23 . Each concave part  17  of the sidewall  14  has a portion  23  of the enlargement  20 , and each flat part  18  has two portions  23  of the enlargement  20 . The portions  23  of the enlargement  20  of each flat part  18  are identical and angularly spaced apart. The outer transverse outline of the concave parts  17  and flat parts  18  over most of the axial length of the wall  14  is depicted partially in dotted line in FIG.  6 . 
     As illustrated in FIG. 7, each front flank  25  of the enlargement  20  is connected to the front edge face  22  of the bell housing  6  by a region  27  of the radially outer surface  21  of the bell housing  6 . Each region  27  has generatrices parallel to the longitudinal axis X—X of the bell housing  6 . 
     Furthermore, the boot  7  internally has an axial shoulder  60  which extends peripherally inside the boot  7  a short axial distance away from the front edge face  22  of the bell housing  6 . 
     The embodiment in FIGS. 6 to  8  makes it possible to have a retaining enlargement  20  whose total angular extent is markedly greater than that of the convex parts  16  of the sidewall  14  of the bell housing  6 . In addition, the portions  23  of the enlargement  20  are more closely angularly spaced than in the transmission joint of FIGS. 1 to  5 . 
     The axial retention of the boot  7  with respect to the bell housing  6  is thus satisfactory and the risk of the boot  7  gaping when the transmission joint is in operation are limited. 
     It is to be noted that the axial shoulder  60  of the boot  7  may also play a part in axially retaining the boot  7  with respect to the bell housing  6  when the rear end region  33  of the boot  7  tends to move backward with respect to the bell housing  6 . To play a part in such retention, the shoulder  60  comes into abutment against the edge face  22  of the bell housing  6 . 
     In an alternative form which is not depicted, it is possible to machine the front edge face  22  of the bell housing  6  so that it comes into contact with the shoulder  60  of the boot  7  around practically its entire periphery when the boot  7  is stressed axially.