Abstract:
The invention relates to a constant velocity ball joint in the form of a counter track joint, comprising an outer joint part with outer tracks, an inner joint part with inner tracks, torque transmitting balls received in pairs of tracks formed of outer tracks and inner tracks which are outwardly curved with reference to the longitudinal joint axis, and a ball cage with cage windows in which the balls are held in a common plane and guided on to the angle-bisecting plane when the joint is articulated. First outer tracks, together with first inner tracks, form first pairs of tracks whose first control angles open in a first axial direction and in which first balls are held. Second outer tracks, together with second inner tracks, form second pairs of tracks whose control angles open in a second axial direction and in which second balls are held, with the control angles being defined as angles between the tangents at the ball contact points in the pairs of tracks. The outer joint part and the inner joint part are axially displaceable relative to one another. The first control angle and the second control angle change in opposite senses when a relative axial displacement occurs. The axial displacement path is limited to observing a minimum value of at least 8° for the respective smaller control angle.

Description:
TECHNICAL FIELD  
         [0001]    The present invention relates to a constant velocity ball joint permitting axial displacement.  
         BACKGROUND OF THE INVENTION  
         [0002]    The most frequent type of plunging joints are so-called VL joints (cross-groove joints) such as according to DE 31 02 871 C2 wherein the center lines of the outer tracks and of the inner tracks each form oppositely directed angles of intersection with the longitudinal joint axis and are positioned in planes extending parallel to the longitudinal joint axis or on a cylindrical face around the longitudinal joint axis.  
           [0003]    From U.S. Pat. No. 3,133,431, there are known plunging joints wherein the center lines of the outer tracks and of the inner tracks form identically sized angles of intersection with the longitudinal joint axis, i.e., they are positioned in planes which contain the longitudinal joint axis itself.  
           [0004]    Both the above-mentioned types of joint are joints with straight tracks.  
           [0005]    It would be desirable to provide a new type of plunging joint for large articulation angles and relatively short displacement paths.  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention provides a constant velocity ball joint in the form of a counter track joint. The joint includes an outer joint part with outer tracks, an inner joint part with inner tracks, torque transmitting balls which are received in pairs of tracks consisting of outer tracks and inner tracks which are curved outwardly with reference to the longitudinal joint axis A, and a ball cage with cage windows in which the balls are held in a common plane and are guided on to the angle-bisecting plane when the joint is articulated. First outer tracks, together with first inner tracks, form first pairs of tracks whose first control angles β 1  open in a first axial direction and in which first balls are held. Second outer tracks, together with second inner tracks, form second pairs of tracks whose second control angles β 2  open in a second axial direction and in which second balls are held. The control angles β 1 , β 2  are defined as angles between tangential planes at the ball contact points in the tracks. Further, the outer joint part and the inner joint part are axially displaceable relative to one another and the first control angles β 1  and the second control angles β 2  change in opposite senses when a relative axial displacement occurs. The axial displacement path V max  is limited to a maximum value that produces a minimum value of at least 8° for the respective smaller control angles β 1 , β 2 . The present joint provides an axial displacement path having at least 0.8 mm, and preferably more than 1.0 mm of play. This is substantially above the axial play of fixed joints, which in comparison is at most 0.5 mm.  
           [0007]    In one form of the displacement path, the joint in accordance with the invention provides a way to uncouple axial vibrations and thus contributes towards improving the noise, vibration, harshness (NVH) behavior. The present design is also advantageous in that it is possible to un-fine the surfaces during the machining operations. Also, the design of the tracks provides a joint with axial centring characteristics.  
           [0008]    In particular, the tracks are curved as in Rzeppa joints or undercut-free (UF) joints. As a consequence, even with larger articulation angles, there is achieved adequate ball control due to sufficiently large control angles.  
           [0009]    By limiting the axial displacement path, it is ensured that the control angles do not become too small as a result of the axial displacement. The stops for delimiting the axial plunging path can become effective exclusively between the outer joint part and the cage, or exclusively between the inner joint part and the cage, or between both pairs simultaneously; in each case when the joint is in the aligned position, in which case the longitudinal axes of the inner joint part and of the outer joint part coincide. As the ball cage is radially set free relative to the inner joint part and to the outer joint part, the joint is characterised by particularly low friction. Furthermore, because of the counter-track formation, it is ensured that the joint is axially self-centring and that the forces acting on the cage are kept within certain limits. In addition, the way in which the balls are enveloped by the tracks in a cross-sectional view is particularly advantageous.  
           [0010]    Other 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]    For a more complete understanding of this invention, reference should now be made to the embodiments illustrated in greater detail in the accompanying drawings and described below by way of examples of the invention.  
         [0012]    In the drawings, fixed joints with counter tracks are compared with inventive joints; both will be described in detail below.  
         [0013]    [0013]FIG. 1 shows a prior art fixed joint with counter tracks according to the state of the art, having Rzeppa tracks: (a) in a longitudinal section through a pair of counter tracks; (b) in a bent longitudinal section through a cage web.  
         [0014]    [0014]FIG. 2 shows a prior art fixed joint with counter tracks, having undercut-free (UF) tracks: (a) in a longitudinal section through a pair of counter tracks; (b) in a bent longitudinal section through a cage web.  
         [0015]    [0015]FIG. 3 shows an inventive joint in a first embodiment with Rzeppa tracks in a bent longitudinal section through a cage web.  
         [0016]    [0016]FIG. 4 shows a detail X of FIG. 3 in an enlarged scale: (a) in an axially centered position of the joint; (b) with maximum axial displacement of the joint.  
         [0017]    [0017]FIG. 5 shows an enlarged detail of a joint similar to that illustrated in FIG. 3 with maximum axial displacement: (a) in a first modified embodiment; (b) in a second modified embodiment.  
         [0018]    [0018]FIG. 6 shows an inventive joint in a second embodiment with Rzeppa tracks in a bent longitudinal section through a cage web.  
         [0019]    [0019]FIG. 7 shows a detail X of FIG. 6 in an enlarged illustration: (a) in an axially centered position of the joint; (b) with maximum axial displacement of the joint.  
         [0020]    [0020]FIG. 8 shows an inventive joint in a third embodiment with Rzeppa tracks in a bent longitudinal section through a cage web.  
         [0021]    [0021]FIG. 9 shows the detail X of FIG. 8 in an enlarged scale: (a) in an axially centered position of the joint; (b) with a maximum axial displacement of the joint.  
         [0022]    [0022]FIG. 10 shows an inventive joint in a fourth embodiment with Rzeppa tracks in a bent section through a cage web.  
         [0023]    [0023]FIG. 11 shows the detail X of FIG. 10 in an enlarged scale: (a) in an axially centered position of the joint; (b) with maximum axial displacement of the joint.  
         [0024]    [0024]FIG. 12 illustrates the principle of an inventive joint in a longitudinal section through a pair of counter tracks, leaving out the ball cage: (a) with maximum axial displacement in a first direction; (b) in an axially centered position of the joint; (c) with maximum axial displacement in the second direction.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0025]    [0025]FIGS. 1 and 2 refer to prior art joints for comparative purposes and to complete the description. They will be described jointly. A joint  11  includes an outer joint part  12  with a formed-on journal  13 , an inner joint part  14  with a plug-in aperture  15  for a shaft, balls  16   1 ,  16   2  and a cage  17  having windows  18  in which the balls are held. The joints are counter track joints. Thus, first outer ball tracks  19   1  in the outer joint part  12  and first inner ball tracks  20   1  in the inner joint part  14 , which tracks hold first balls  16   1 , are designed axially oppositely relative to second outer ball tracks  19   2  in the outer joint part  12  and second inner ball tracks  20   2  in the inner joint part  14 , which tracks hold second balls  16   2 . The first pairs of tracks  19   1 ,  20   1  have control angles which open in a first direction R 1 . The second pairs of tracks  19   2 ,  20   2  have control angles which open in a second direction R 2 . The counter track formations are achieved in that the centers of curvature of the outer ball tracks  19   1 ,  19   2  in the outer joint part are circumferentially alternately offset in opposite axial directions relative to the central joint plane E, and equally, the centers of curvature of the inner ball tracks  20   1 ,  20   2  in the inner joint part  14  are circumferentially alternately offset in opposite axial directions relative to the central joint plane E. The central joint plane is defined by the centers of the balls.  
         [0026]    The ball cage  17  includes a spherical outer face  21  which is guided in a spherical inner face  22  of the outer joint part  12 . Furthermore, the cage includes a spherical inner face  23  in which there is guided a spherical outer face  24  of the inner joint part  14 . As a result of this configuration, the joints become fixed joints.  
         [0027]    The track center lines  9   1 ,  10   1  of the tracks  19   1 ,  20   1  as well as the track center lines  9   2 ,  10   2  of the tracks  19   2 ,  20   2  intersect one another in the central joint plane E when the joint is in the aligned condition. Whereas in FIG. 1, the center lines  9 ,  10  of the tracks are entirely circular arches, the center lines  9 ,  10  of the tracks in FIG. 2 are formed by circular arches with an adjoining axis-parallel tangent.  
         [0028]    [0028]FIG. 3 shows a joint  11   3  which is similar to that shown in FIG. 1 but differs substantially in certain details. The details which correspond to one another have been given the same reference numbers. To that extent, reference is made to the description above. In particular, reference is made to the illustrated outer tracks  19   1  and inner tracks  20   1  as well as to the outer tracks  20   2  and inner tracks  20   2  which are not shown in FIG. 3 for simplification. The details which deviate from FIG. 1 have been given the index  3  and will be referred to below. With the joint of FIG. 3, the spherical outer face  21   3  of the ball cage  17   3  is arranged at a radial distance from the spherical inner face  22   3  of the outer joint part  12   3 . Furthermore, the spherical inner face  23   3  of the ball cage  17   3  is arranged at a radial distance from the spherical outer face  24   3  of the inner joint part  14   3 . As a result, there is achieved, as will be explained in greater detail below, a relative axial displaceability between the outer joint part  12   3  and the inner joint part  14   3 , with the ball cage  17   3  setting itself to half the path.  
         [0029]    In FIG. 4 a , in the enlarged detail X of FIG. 3, any details corresponding to those in FIG. 3 have been given the same reference numbers, with reference being made to the previous description.  
         [0030]    In FIG. 4 b,  the enlarged detail X of FIG. 3 is in a modified position, with the central joint plane, in its relative position relative to the outer joint part  12   3 , being arbitrarily used as the reference plane E B . With respect hereto, the inner joint part  14   3  is axially moved towards the right by the displacement path VI, whereas the ball cage  17   3  is moved towards the right by half the size of the displacement path VC. In this position, an inner edge  25   3  of the outer joint part  12   3  stops against the outer face  21   3  of the ball cage  17   3 , whereas at the same time an outer edge  26   3  of the inner joint part  14   3  stops against the inner face  23   3  of the ball cage  17   3 . An outer edge  27   3  of the ball cage and a second outer edge  28   3  of the inner joint part form corresponding stops, with the displacement path of the same size extending in the opposite direction. An angle ∝ 1  at the ball cage is the angle between the central plane of the ball cage and the line of contact with the edge  25   3 , and an angle ∝ 2  at the ball cage  17   3  is the angle between the central plane of the ball cage and the line of contact with the edge  26   3 . The radius of the inner face  22   3  at the outer joint part has been given the reference symbol RO and the radius of the face  21   3  at the ball cage has been given the reference symbol RC.  
         [0031]    [0031]FIG. 5 a  shows part of a modified inventive joint similar to that illustrated in FIG. 4 b . Identical parts have been given identical reference numbers, but are identified by the index  4 . As a result of modified radii, only one circumferential edge  26   4  of the inner joint part  14   4  touches the inner face  23   4  of the ball cage  17   4 , whereas in this axial stopping position, the outer face  21   4  of the ball cage  17   4  still has radial play relative to the inner edge  25   4  of the outer joint part  12   4 . A second outer edge  28   4  of the inner joint part forms a corresponding stop, with the displacement path of the same size extending in the opposite direction. An angle ∝ at the ball cage  17   4  is the angle between the displaced central plane and a radius through the contacting edge.  
         [0032]    [0032]FIG. 5 b  shows part of a modified inventive joint similar to that illustrated in FIG. 4 b . Identical parts have been given identical reference numbers, but are identified by the index  5 . As a result of modified radii, only one circumferential edge  25   5  of the outer joint part  12   5  touches the outer face  21   5  of the ball cage  17   5 , whereas in this axial stopping position, the inner face  23   5  of the ball cage  17   5  still has radial play relative to the outer face  23   5  of the inner joint part  14   5 . An outer edge  27   5  of the ball cage forms a corresponding stop, with the displacement path of the same size extending in the opposite direction. An angle ∝ at the ball cage  17   5  is the angle between the displaced central plane and a radius through the contacting edge.  
         [0033]    [0033]FIG. 6 shows a joint  11   6  which is similar to that shown in FIG. 1 but differs substantially in certain details. The details which correspond to one another have been given the same reference numbers. To that extent, reference is made to the description above. In particular, reference is made to the illustrated outer tracks  19   1 , and inner tracks  20   1  as well as to the outer tracks  19   2  and inner tracks  20   2  which are not shown in FIG. 6, for simplification. The details which deviate from FIG. 1 have been given the index  6  and will be referred to below. With the joint of FIG. 6, the spherical outer face  21   6  of the ball cage  17   6  is radially centered in an internally cylindrical inner face  22   6  of the outer joint part  12   6 , but has axial play relative to two adjoining internally conical stop faces  29   6 ,  30   6 . Furthermore, the inner face  23   6  of the ball cage  17   6  is arranged at a radial distance from the spherical outer face  24   6  of the inner joint part  14   6 . As a result, there is achieved, as will be explained in greater detail below, a relative axial displaceability between the outer joint part  12   6  and the inner joint part  14   6 , with the ball cage  17   6  setting itself to half the displacement path.  
         [0034]    In FIG. 7 a , in the enlarged detail X of FIG. 6, the same details as in FIG. 6 have been given the same reference numbers, with reference being made to the previous description.  
         [0035]    In FIG. 7 b , the enlarged detail X of FIG. 6 is in a modified position, with the central joint plane, in its relative position relative to the outer joint part  12   6 , being arbitrarily used as the reference plane E B . With reference hereto, the inner joint part  14   6  is axially moved towards the right by the displacement path VI, whereas the ball cage  17   6  is moved towards the right by half the size of the displacement path VC. In this position, an inner edge  25   6  of the outer joint part  12   6  stops against the outer face  21   6  of the ball cage  17   6 , whereas at the same time an outer edge  26   6  of the inner joint part  14   6  stops against the inner face  23   6  of the ball cage  17   6 . An outer edge  27   6  of the ball cage and a second outer edge  28   6  of the inner joint part form corresponding stops, with the displacement path of the same size extending in the opposite direction. An angle ∝ at the ball cage  17   6  is the angle between the central plane of the ball cage and the line of contact with the edge  25   6 . The radius of the face  21   6  at the ball cage has been given the reference symbol RC.  
         [0036]    [0036]FIG. 8 shows a joint  11   8  which is similar to that shown in FIG. 1, but differs substantially in certain details. The details which correspond to one another have been given the same reference numbers. To that extent, reference is made to the description above. In particular, reference is made to the illustrated outer tracks  19   1  and inner tracks  20   1  as well as to the outer tracks  19   2  and inner tracks  20   2  which are not shown in FIG. 8, for simplification. The details which deviate from FIG. 1 have been given the index  8  and will be referred to below. With the joint of FIG. 8, the spherical outer face  21   8  of the ball cage  17   8  is radially centered in the spherical inner face  22   8  of the outer joint part  12   8 . Furthermore, the inner face  23   8  of the ball cage  17   8  is arranged at a radial distance from the spherical outer face  24   8  of the inner joint part  14   8 . As a result, there is achieved, as will be explained in greater detail below, a relative axial displaceability between the outer joint part  12   8  and the inner joint part  14   8 , with the ball cage  17   8  setting itself to half the displacement path.  
         [0037]    In FIG. 9 a , in the enlarged detail X of FIG. 8, the same details as in FIG. 8 have been given the same reference numbers, with reference being made to the previous description.  
         [0038]    In FIG. 9 b , the enlarged detail X of FIG. 8 is in a modified position, with the central joint plane, in its relative position relative to the outer joint part  12   8 , being arbitrarily used as the reference plane E B . With reference hereto, the inner joint part  14   8  is axially moved towards the right by the displacement path VI, whereas the ball cage  17   8  is moved towards the right by half the size of the displacement path VC. In this position, an outer edge  26   8  of the inner joint part  12   8  stops against the inner face  23   8  of the ball cage  17   8 . A second outer edge  28   8  of the inner joint part forms a corresponding stop, with the displacement path of the same size extending in the opposite direction. An angle ∝ at the ball cage  17   8  is the angle between the central plane of the ball cage and the line of contact with the edge  26   8 . The radius of the outer face  24   8  at the inner joint part has been given the reference symbol RI and the radius at the inner face  21   8  at the ball cage has been given the reference symbol RC.  
         [0039]    [0039]FIG. 10 shows a joint  11   10  which is similar to that shown in FIG. 1, but differs substantially in certain details. The details which correspond to one another have been given the same reference numbers. To that extent, reference is made to the description above. In particular, reference is made to the illustrated outer tracks  19   1  and inner tracks  20   1  as well as to the outer tracks  19   2  and inner tracks  20   2  which are not shown in FIG. 10, for simplification. The details which deviate from FIG. 1 have been given the index  10  and will be referred to below. With the joint of FIG. 10, the spherical outer face  21   10  of the ball cage  17   10  is radially centered in an internally cylindrical inner face  22   10  of the outer joint part  12   10 . Furthermore, the spherical outer face  24   10  of the inner joint part  14   10  is centered in the internally cylindrical inner face  23   10  of the ball cage  17   10 . As a result, there is achieved, as will be explained in greater detail below, a relative axial displaceability between the outer joint part  12   10  and the inner joint part  14   10 , with the ball cage  17   10  setting itself to half the displacement path.  
         [0040]    In FIG. 11 a  in the enlarged detail X of FIG. 10, the same details as in FIG. 10 have been given the same reference numbers, with reference being made to the previous description.  
         [0041]    In FIG. 11 b , the enlarged detail X of FIG. 10 is in a modified position, with the central joint plane, in its relative position relative to the outer joint part  12   10 , being arbitrarily used as the reference plane E B . With respect hereto, the inner joint part  14   10  is axially moved towards the right by the displacement path VI, whereas the ball cage  17   10  is moved towards the right by half the size of the displacement path VC. In this position, an inner edge  25   10  of the outer joint part  12   10  stops against the outer face  21   10  of the ball cage  17   10 . An outer edge  27   10  of the ball cage forms a corresponding stop, with the displacement path of the same size extending in the opposite direction. An angle ∝ at the ball cage  17   10  is the angle between the central plane of the ball cage and the line of contact with the edge  25   3 . The radius of the face  21   10  at the ball cage has been given the reference symbol RC.  
         [0042]    [0042]FIG. 12, in a simplified illustration without the cage, shows the outer joint part  12 , the inner joint part  14  and the balls  16  which carry the same reference numbers as used in FIG. 1. In all three illustrations, the central plane defined by the ball centers is referred to as the central joint plane E, i.e., a new artificial reference plane is not introduced. The tracks  19 ,  20  are referred to by their track base lines and their track center lines  9 ,  10  only. For the sake of simplicity, the track edges have also been eliminated. The position of the balls is defined by the points of intersection of the track center lines  9 ,  10 . As a result of the relative displacement V max  between the outer joint part and the inner joint part, the centers of curvature of the track center lines  9 ,  10  are displaced relative to one another, as a result of which the control angles between the associated track center lines  9 ,  10  simultaneously change in opposite senses, i.e. the one increases, the other decreases. The minimum distance of the centers of curvature from the central joint plane E is referred to as Q min  and the maximum distance of the centers of curvature from the central joint plane E is referred to as Q max . The angles between the radii positioned perpendicularly on the tangents in the points of intersection of the track center lines correspond to the control angles β 1 , β 2  between said track center lines. Each half of said angles between the radii is referred to as β max/2 , β min/2 . The axial displacement is to be delimited to such an extent that β min/2  is not less than 4° and that the smallest control angle β min  thus is not less than 8°.  
         [0043]    From the foregoing, it can be seen that there has been brought to the art a new and improved constant velocity joint. While the invention has been described in connection with one or more embodiments, it should be understood that the invention is not limited to those embodiments. Thus, the invention covers all alternatives, modifications, and equivalents as may be included in the spirit and scope of the appended claims.