Patent Publication Number: US-2006019758-A1

Title: Homokinetic joint for a wheel hub

Description:
The present invention relates to a homokinetic joint for a wheel hub.  
      In general, well-known kinds of homokinetic joints for wheel hubs are coupled in such a way as to be able to rotate around a spindle of the relative wheel hub, and comprise a cylindrical coupling end which is inserted inside an axial passing housing of the spindle, and a coupling device, which is shared between the cylindrical end and the axial housing, and which usually comprises a grooved outline which is suitable for transmitting a torque moment between the homokinetic joint and the wheel hub.  
      Homokinetic joints of the kind which have just been described, while having been shown to be reliable and resistant, have however demonstrated some disadvantages which are essentially due to the complexity, mainly geometrical but also in terms of production, of the above-mentioned grooved outline also in consideration of the relatively difficult level of manipulation of the relative coupling end.  
      The aim of the present invention is to produce a homokinetic joint for a wheel hub, which will permit the resolution of the above-described disadvantages in a simple and cost-effective manner.  
      According to the present invention a homokinetic joint for a wheel hub will be produced, the homokinetic joint being able to be coupled in such a way as to rotate around a spindle of the relative wheel hub in order to rotate around a rotation axis, and comprising: 
          a coupling end which is inserted inside a passing axial housing of the spindle; and 
            a coupling device, which is suitable for transmitting a torque moment between the homokinetic joint and the wheel hub, and which comprises, in its turn, a first connecting outline which is obtained around the coupling end, and a second connecting outline which is obtained inside the axial housing; the homokinetic joint being characterised by the fact that the said first and second connecting outlines present a shape which is complementary to each other, and a radius of angularly variable dimensions with continuity on a plane which is transverse to the rotation axis; the first and second connecting outlines both comprising, in relation to the rotation axis, at least one respective convex portion.   
               

    
    
      The present invention will now be described with reference to the attached drawings, which illustrate a non-limiting of embodiment of the present invention, in which:  
       FIG. 1  is a section view of a preferred form of embodiment of a homokinetic joint for a wheel hub produced according to the present invention; and  
       FIG. 2  shows a section along the line II-II which is shown in  FIG. 1 . 
    
    
      With reference to  FIG. 1 , the number  100  indicates in its entirety a homokinetic joint, which is coupled to a bearing wheel hub unit, indicated with the numbers  10  and  20  respectively, in such a way as to be able to rotate around a rotation axis A.  
      The bearing  10  comprises an inner race  11  which is co-axial to the axis A, an outer race  12  which is co-axial to the inner race  11 , and two crowns  14  of rolling bodies  15 , which are interposed between the two races  11  and  12 , and which are both mounted inside a respective rolling track  16 .  
      In the form of embodiment which is shown in  FIG. 1 , the rolling bodies  15  are defined by spheres, and the inner race  11  comprises a portion  11   a  which is integrated with the wheel hub  20  and is provided with a relative track  16   a , and a portion  11   b  which is mounted on the wheel hub  20  itself and is provided with a relative track  16   b.    
      The wheel hub  20  comprises a flange  21  which is transverse to the axis A, and a spindle  22 , which is integral with the flange  21  itself, and which extends along the axis A inside the inner race  11  ending in a small rolled border  23  which abuts the portion  11   b  itself in order to axially block the portion  11   b  against the portion  11   a.    
      The spindle  22  presents an axial passing housing  24 , which extends for the whole of the length of the spindle  22  itself along the axis A, and is axially delimited by an outlet surface  24   a  and an entry surface  24   b.  In particular, the surfaces  24   a  and  24   b  are both transverse to the axis A and external to the housing  24 , and, in addition, the surface  24   b  is substantially defined by the small border  23 .  
      The homokinetic joint  100  comprises a dome  40  which is arranged in such a way as to abut the small border  23 , and an end body  50 , which is integral with the dome  40 , and which is inserted inside the housing  24  in order to couple the homokinetic joint  100  to the wheel hub  20  in such a way that it can rotate.  
      In addition, the homokinetic joint  100  comprises a coupling device  60 , which is suitable for transmitting a torque moment between the body  50  and the wheel hub  20 , and which comprises, in its turn, a peripheral connecting outline  70  which is obtained around the body  50 , and a complementary connecting outline  80  which is obtained inside the axial housing  24 , and which presents a shape which is complementary to a shape of the peripheral outline  70 .  
      In particular, as is better illustrated in  FIG. 2 , the outlines  70  and  80  present a radius R of angularly variable dimensions with continuity on a plane which is transverse to the axis A, and both comprise a number N 1  of convex portions  71  and  81  in relation to the axis A itself, and a number N 2  of concave portions  72  and  82  also in relation to the axis A. The values of the numbers N 1  and N 2  depend on the necessary construction and planning characteristics, and may be equal to each other as in cases of this kind, or may be different from each other.  
       FIG. 2  illustrates a case in which both the number N 1  and the number N 2  have a value which is equal to three and the portions  71 ,  81  and  72 ,  82  are alternated in relation to each other around the axis A. Alternatively, and in a way which is easily understandable from the foregoing description, the outlines  70  and  80  may each be provided with only one relative convex portion  71 ,  81  arranged between two relative concave portions  72 ,  82  contiguous in relation to each other.  
      In addition, the outlines  70  and  80  present a tapering shape which decreases towards the surface  24   a , or rather decreases in the direction of the introduction of the body  50  inside the axial housing  24 , in order to permit the axial blocking of the body  50  inside the spindle  22 .  
      Finally, the homokinetic joint  100  comprises a small border  90 , which defines a free end portion of the body  50 , and is turned up and rolled in such a way as to abut the outlet surface  24   a  of the axial housing  24  in order to axially block in definitive fashion the body  50  itself inside the axial housing  24 , and to render the dome  40  in contact with the entry surface  24   b , or rather against the small border  23 .  
      It is intended that the present invention should not be limited to the form of embodiment which is herein described and illustrated, which is to be considered as an example of a form of embodiment of the homokinetic joint for a wheel hub, and which might instead by subject to further modifications relating to the shape and disposition of its parts, as well as to details pertaining to construction and assembly.