Abstract:
A constant velocity joint ( 11 ) in the form of a counter track joint wherein, when the joint is in the aligned condition, the ratio (V 1 ) of the pitch circle diameter (PCDS) of the shaft toothing in the inner joint part ( 15 ) in the power of three relative to the product of the ball diameter (DK) squared and pitch circle diameter (PCDB) of the balls ( 17 ) assumes a value ranging between 0.9 and 1.3.

Description:
TECHNICAL FIELD 
   The invention relates to a constant velocity joint in the form of a counter track joint with the following characteristics: an outer joint part having a first longitudinal axis and comprising first outer ball tracks and second outer ball tracks; an inner joint pan having a second longitudinal axis and comprising first inner ball tracks and second inner ball tracks; the first outer ball tracks and the first inner ball tracks form first pairs of tracks; the second outer ball tracks and the second inner ball tacks form second pairs of tracks; the pairs of tracks each accommodate a torque transmitting ball; a ball cage is positioned between the outer joint part and the inner joint part and comprises circumferentially distributed cage windows which each receive at least one of the balls; when the joint is in the aligned condition, the first pairs of tracks open in the central joint plane in a first direction, and when the joint is in the aligned condition, the second pairs of tracks open in the central joint plane in a second direction. 
   BACKGROUND 
   Counter track joints of the aforementioned type are basically known from U.S. Publication No. 2004/0033837 A1, wherein joints with 6 balls and with 8 balls are shown. The type of ball tracks here corresponds to the type known from Rzeppa joints (RF joints) and undercut free-joints (UF joints). This means that the center lines of the ball tracks consist of uniform radii (RF joint) or consist of radii and adjacent axially parallel lines (UF joint). In the described counter track joints, the axial opening direction of the pairs of tracks alternates circumferentially, resulting in the type of counter track joint. 
   Known from DE 103 37 612 A1 are counter track joints in which the track center lines of the first pairs of tracks having an opening angle with an opening direction with aligned joint pointing toward the joint bottom designed in such a way that the opening angle experiences a reversal in its opening direction starting at a specific articulation angle when the joint is articulated. In particular, this is realized by virtue of the fact that the center lines of the ball tracks of the first pairs of tracks are S-shaped, and thereby each exhibit a turning point. 
   Known inter alia from U.S. Publication No. 2004/116192 A1 are counter track joints in which the center lines of the first ball tracks have a turning point near the joint opening, so that the center lines of the first outer ball tracks are S-shaped. Due to the symmetry condition, the same holds true for the center lines of the first inner ball tracks of the joint inner part. The articulation angle of these counter track joints can be increased in this way. 
   Joints of the kind mentioned at the outset have been manufactured in various sizes, wherein the geometric conditions were derived from the available ball sizes taking into account the required torque capacity, using standard balls from ball bearing manufacture as the joint balls. In addition, the configuration of known joints has also been determined or influenced by the fitting dimensions of the available intermediate shafts, i.e., in particular the pitch circle diameter of the shaft splines of such intermediate shafts, and must correspond to the pitch circle diameter of the shaft splines in the joint inner part. 
   SUMMARY OF THE INVENTION 
   An object of this invention is to create a counter track joint of the kind mentioned at the outset optimized to the building space, which occupies the least possible radial building space at a given torque capacity. 
   A first solution provides that the ratio (V 1 ) between the pitch circle diameter (PCDS) of the shaft splines in the joint inner part to the third power and the product of ball diameter (DK) squared and pitch circle diameter of the balls with aligned joint (PCDB) assumes a value of between 0.9 and 1.3, i.e.,
 
0.9&lt; V 1&lt;1.3 with  V 1 =PCDS   3 /( DK   2   −PCDB ).
 
   In a second solution, the ratio (V 3 ) between the pitch circle diameter of the shaft splines in the joint inner part PODS and the OR factor lies between 0.34 and 0.37, wherein the OR factor is defined as the sum of the pitch circle diameter of the balls (PCDB) with aligned joint and the ball diameter (DK), so that
 
0.34 &lt;V 3&lt;0.37 with  V 3 =PCDS /( PCDB+DK ).
 
   The above approaches are based on postulations that the optimized configuration must have the necessary section modulus of the shaft splines in the joint inner part, and at the same time that the permissible load on the balls may not be exceeded taking into account the Hertz pressure, and finally that the outer diameter of the joint is to be kept low. To this end, the above approaches are used to indicate suitable configuration conditions with which these requirements are satisfied by selecting a large enough pitch circle diameter of the shaft splines and ball diameter, wherein the pitch circle diameter of the balls, being of importance besides the ball diameter for the outer diameter of the joint is designed as low as possible. 
   Each of the two approaches mentioned leads to the objective on its own. However, the result can be optimized by also using both approaches in combination to further pinpoint the results according to the invention. 
   One embodiment provides that the ratio (V 2 ) between the IR factor and the OR factor measures between 0.525 and 0.585, wherein the IR factor is defined as the difference between the pitch circle diameter of the balls with aligned joint (PCDB) and the ball diameter (DK), and the OR factor is defined as the sum of the pitch circle diameter of the balls with aligned joint PCDB and the ball diameter DK, so that
 
0.525 &lt;V 2&lt;0.585 with  V 2=( PCDB−DK )/( PCDB+DK ).
 
   In combination with at least one of the two aforementioned approaches, this dimensioning yields a particularly favorable result. 
   Another embodiment further provides that the ratio (V 4 ) between the pitch circle diameter of the shaft splines in the joint inner part (PCDS) and the IR factor measures between 0.58 and 0.65, wherein the IR factor is defined as the difference between the pitch circle diameter of the balls with aligned joint (PCDB) and the ball diameter (DK), so that
 
0.58 &lt;V 4&lt;0.65 with  V 4 =PCDS /( PCDB−DK ).
 
   In combination with at least one of the two aforementioned approaches, this dimensioning yields a particularly favorable result. 
   With respect to the forces on the ball cage and other properties that determine joint function, it has proven favorable to alternate the first pairs of tracks and the second pairs of tracks over the circumference of the joint. 
   The joint can be designed as a six-ball joint, and in a particularly favorable design, is an eight-ball joint. The joint is configured in a particularly advantageous way, wherein the articulation angle ranges from 25° to 45°, in particular from 30° to 40°. This stipulation means that the balls are still reliably slung in the inner and outer ball tracks within these articulation angle ranges, and that the first balls only start exiting the ball tracks at articulation angles exceeding these ranges. 
   The joint according to the invention can be designed as a disc joint with unilateral flanging on the joint outer part, or as a monoblock joint, wherein a joint bottom and shaft journal are integrally molded on the joint outer part. 
   Joints according to the invention can be used for the side shafts of motor vehicles that establish the connection between the differential output and wheel hub. In this case, there is a particularly favorable application as a differential-side fixed joint in such side shafts, which have two fixed joints and a plunging unit in the intermediate shaft. 
   Joints according to the invention can also be used in longitudinal drive shafts of motor vehicles that comprise at least one fixed joint and a plunging joint or at least two fixed joints and a plunging unit. 
   Another application involves multi-part longitudinal drive shafts in motor vehicles, which in addition to a fixed joint have at least one intermediate joint and a plunging joint and/or at least one intermediate joint and a longitudinal plunging unit. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred exemplary embodiments of the invention are shown in the drawings, and will be described below. 
       FIG. 1  shows a counter track joint according to an embodiment of the invention with six balls, designed as a disc joint: 
     A) in an axial view; and 
     B) in a longitudinal section along the B-B line. 
       FIG. 2  shows a counter track joint according to an embodiment of the invention with eight balls, designed as a disc joint: 
     A) in an axial view; and 
     B) in a longitudinal section along the B-B line. 
       FIG. 3  shows a counter track joint according to an embodiment of the invention with six balls, designed as a monoblock joint: 
     A) in an axial view; 
     B) in a longitudinal section along the B-B line; and 
     C) in a longitudinal section along the C-C line. 
       FIG. 4  shows a counter track joint according to an embodiment of the invention with eight balls, designed as a monoblock joint: 
     A) in an axial view; 
     B) in a longitudinal section along the B-B line; and 
     C) in a longitudinal section along the C-C line. 
       FIG. 5  shows a drive shaft according to an embodiment of the invention with at least one joint according to the invention and a plunging unit in partial longitudinal section. 
       FIG. 6  shows an installation scenario according to an embodiment of the invention for a drive shaft according to  FIG. 5  in a motor vehicle in partial longitudinal section. 
       FIG. 7  shows a longitudinal drive shaft according to an embodiment of the invention with a fixed joint according to the invention and a plunging joint in longitudinal half section. 
       FIG. 8  shows a longitudinal drive shaft according to an embodiment of the invention with a fixed joint according to the invention as an intermediate joint, another universal joint as an intermediate joint, and a plunging joint in longitudinal half section. 
       FIG. 9  illustrates a motor vehicle schematic, illustrating the side shafts, drive shafts, differential and drive unit. The joints ( 11 ,  111 ,  112  and  211 ) that are the subject of this disclosure are represented generically as joint  11 . 
   

   DETAILED DESCRIPTION 
   The two depictions on  FIG. 1  wilt be described together below. The universal joint  11  according to the invention is designed as a so-called disc joint. It encompasses a joint outer part  12  with a first opening  13  and a second opening  14 . The joint further encompasses a joint inner part  15 , a ball cage  16  and torque-conveying balls  17 . First outer ball tracks  18  in the joint outer part  12  and first inner ball tracks  19  in the joint inner part  15  accommodate balls  17   1  and form first pairs of tracks with each other. Second outer ball tracks  20  in the joint outer part  12  and second inner ball tracks  21  in the joint inner part  15  form second pairs of tracks with each other, which accommodate second balls  17   2 . The two types of pairs of tracks ( 18 ,  19 ;  20 ,  21 ) are alternately arranged over the circumference. Six pairs of tracks are especially provided. The first pairs of tracks form an opening angle with each other that points in a first direction R 1  to the opening  13 . The second pairs of tracks form an opening angle with each other that points in a second direction R 2  toward the opening  14 . A center joint plane E that accommodates the centers P of the balls intersects the longitudinal axis of the joint defined by the longitudinal axes A 12  of the joint outer part and A 15  of the joint inner part in a joint center M. The ball cage  16  holds the first balls  17   1  and second balls  17   2  in alternating circumferentially distributed cage windows  24   1 ,  24   2 . The pitch circle diameter on which the ball centers P lie with the aligned joint is denoted with PCDB. The pitch circle diameter of the insertion opening  27  of the joint inner part  15 , which generally has shaft splines not shown here in detail, is denoted with PCDS. The ball diameter is marked DK. 
   The two depictions on  FIG. 2  will be described together below. The universal joint  11   2  according to the invention is designed as a so-called disc joint. It encompasses a joint outer part  12   2  with a first opening  13  and a second opening  14 . The joint further encompasses a joint inner part  15   2 , a ball cage  16   2  and torque-conveying balls  17 . First outer ball tracks  18  in the joint outer part  12   2  and first inner ball tracks  19  in the joint inner part  15   2  accommodate balls  17   1  and form first pairs of tracks with each other. Second outer ball tracks  20  in the joint outer part  12   2  and second inner ball tracks  21  in the joint inner part  15   2  form second pairs of tracks with each other, which accommodate second balls  17   2 . The two types of pairs of tracks ( 18 ,  19 ;  20 ,  21 ) are alternately arranged over the circumference. Eight pairs of tracks are especially provided. The first pairs of tracks form an opening angle with each other that points in a first direction R 1  to the opening  13 . The second pairs of tracks form an opening angle with each other that points in a second direction R 2  toward the opening  14 . A center joint plane E that accommodates the centers P of the balls intersects the longitudinal axis of the joint defined by the longitudinal axes A 12  of the joint outer part and A 15  of the joint inner part in a joint center M. The ball cage  16   2  holds the first balls  17   1  and second balls  17   2  in alternating circumferentially distributed cage windows  24   1 ,  24   2 . The pitch circle diameter on which the ball centers P lie with the aligned joint is denoted with PCDB. The pitch circle diameter of the insertion opening  27  of the joint inner part  15   2 , which generally has shaft splines not shown here in detail, is denoted with PCDS. The ball diameter is marked DK. Since two first pairs of tracks ( 18 ,  19 ) are cut in plane A-A, the sectionally depicted pairs of tracks both open in the first direction R 1  toward the opening  13 . 
   The individual depictions on  FIG. 3  will be described together below. The same details as on  FIG. 1  are labeled with the same reference numbers, and modified features are indexed by 100. Reference is made to the corresponding description. Instead of a second opening  14 , the joint outer part  112  here has a formed-on bottom  25  followed by a shaft journal  26 . The joint otherwise largely corresponds with the one shown on  FIG. 1 . A first (upper) and second (lower) pair of tracks is cut in a radially opposing manner in plane AA, while a second (upper) and a first (lower) pair of tracks is cut in a radially opposing manner in plane BB. 
   The individual depictions on  FIG. 4  will be described together below.  FIG. 4  is a monoblock joint like  FIG. 3 , but includes eights balls like the joint of  FIG. 2 . The same details as on  FIG. 2  and  FIG. 3  are labeled with the same reference numbers, and modified features are further indexed by 100. Reference is made to the corresponding description. Instead of a second opening  14  ( FIG. 2 ), the joint outer part  212  here has a formed-on bottom  25  followed by a shaft journal  26 . The joint otherwise largely corresponds to the one shown in  FIG. 2 . Two second pairs of tracks  120 ,  121  are cut in the plane AA in a respectively radially opposing manner, while two first pairs of tracks  118 ,  119  are cut in a radially opposing manner in plane BB. 
     FIG. 5  shows a drive shaft  55 , illustrated in  FIG. 9 , that has a universal joint according to the invention as a monoblock joint based on one of  FIG. 3  or  4 , along with an intermediate shaft  35  and a second universal joint  31 , which can also be a joint according to the invention, especially structurally identical with the joint  111 ,  211 . The intermediate shaft  35  encompasses an axial plunging unit  28 , which includes a sleeve  29 , a journal  30  as well as torque-conveying balls active between the two and not denoted in specific detail as the essential components, and permits a longitudinal compensation of the drive shaft  55  between the universal joints  111 ,  211  and  31 . 
     FIG. 6  shows a drive shaft  55  according to  FIG. 5  installed as a side shaft  40  in a motor vehicle  54 , illustrated in  FIG. 9 . The shaft journal of the joint  111 ,  211  according to the invention is inserted into a differential gear  32  and secured therein, while the shaft journal of the second fixed joint  31  is inserted into a wheel hub arrangement  33  with a wheel mount  34 , the same details are marked with the same reference numbers as on  FIG. 5 . 
     FIG. 7  shows a drive shaft  55 , illustrated in  FIG. 9 , according to the invention with a joint  11 ,  112  according to the invention designed as a disc joint according to one of  FIG. 1  or  2 , which takes the form of a longitudinal drive shaft  55 . An intermediate shaft  41  comprises a shaft tube  39  and two shaft journals  36 ,  37  welded thereto. The shaft journal  37  is connected with a plunging joint  38 , in particular a so-called VL-joint. The shaft journal  36  is connected with the joint  11 ,  112  according to the invention. 
     FIG. 8  shows a cardan drive shaft  55 , illustrated in  FIG. 9 , according to the invention with a joint  11 ,  112  according to the invention designed as a disc joint according to one of  FIG. 1  or  2 , which takes the form of a longitudinal drive shaft  55 , and has a disc joint  42 , an intermediate shaft  43  with a flange  44  and a journal  45  from right to left, along with an elastic intermediate bearing  46 , wherein the joint  11 ,  112  is followed by another intermediate shaft  47  with a shaft journal  48 , another intermediate bearing  49  and a universal joint  50 ; finally, there is another intermediate shaft  51  with shaft journals  52  connected with a universal plunging joint  53 , in particular a VL-joint. Shafts of this kind are incorporated in the longitudinal drive train of motor vehicles  54  between a gearbox output  47  and a differential  32  input, illustrated in  FIG. 9 . 
   In each embodiment of the joints  11 ,  11   2 ,  111 ,  211 , the ratio (V 1 ) between the pitch circle diameter (PCDS) of the shaft splines in the joint inner part to the third power and the product of ball diameter (DK) squared and pitch circle diameter of the balls with aligned joint (PCDB) assumes a value of between 0.9 and 1.3, i.e.,
 
0.9 &lt;V 1&lt;1.3 with  V 1 =PCDS   3 /( DK   2   −PCDB ).
 
   Alternatively or, in addition, the ratio (V 3 ) between the pitch circle diameter of the shaft splines in the joint inner part (PCDS) and the OR factor lies between 0.34 and 0.37, wherein the OR factor is defined as the sum of the pitch circle diameter of the balls (PCDB) with aligned joint and the ball diameter (DK), so that
 
0.34 &lt;V 3&lt;0.37 with  V 3 =PCDS /( PCDB+DK ).
 
   In combination with at least one of V 1  or V 3  being satisfied, the ratio (V 2 ) between the IR factor and the OR factor measures between 0.525 and 0.585, wherein the IR factor is defined as the difference between the pitch circle diameter of the balls with aligned joint (PCDB) and the ball diameter (DK), and the OR factor is defined as the sum of the pitch circle diameter of the balls with aligned joint (PCDB) and the ball diameter (DK), so that
 
0.525 &lt;V 2&lt;0.585 with  V 2=( PCDB−DK )/( PCDB+DK ).
 
   Further in combination with at least one of V 1  or V 3  being satisfied, the ratio (V 4 ) between the pitch circle diameter of the shaft splines in the joint inner part (PCDS) and the IR factor measures between 0.58 and 0.65, wherein the IR factor is defined as the difference between the pitch circle diameter of the balls with aligned joint (PCDB) and the ball diameter (DK), so that
 
0.58 &lt;V 4&lt;0.65 with  V 4 =PCDS /( PCDB−DK ).
 
   For each embodiment, the joint can be configured wherein the articulation angle ranges from 25° to 45°, in particular from 30° to 40°.