Abstract:
A ball body is guided in a partially cylindrical hole into which a guide ring is inserted to secure it axially and to guide the pivoting movement. The tripod joint is suitable for the displaceable and pivotable driving connection of two shaft ends, in particular in conjunction with drive trains or side shafts of motor vehicles.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    The present application claims foreign priority to Application No. 101 41 427.7, filed on Aug. 23, 2001 in the Federal Republic of Germany, which is expressly incorporated herein in its entirety by reference thereto.  
         FIELD OF THE INVENTION  
         [0002]    The present invention relates to a tripod joint.  
         BACKGROUND INFORMATION  
         [0003]    Tripod joints are used, for example, as side shafts of motor vehicles. The tripod joints are used for transmitting driving torques between two driving elements of a drive train. The tripod joints allow a relative displacement and a relative pivoting of the driving elements to be compensated for. In the case of side shafts of a motor vehicle, relative movements of this type are caused by spring deflections of the vehicle wheels.  
           [0004]    U.S. Pat. No. 4,619,628 describes a tripod joint having a joint outer part and a joint inner part held in the latter. The joint inner part has a tripod star having ball bodies having pins. The ball bodies are accommodated pivotably in a partially spherical universal ball joint of a pressure element and are therefore mounted pivotably with respect to the pressure element. The pressure element is mounted movably via rolling bearings with respect to the mating surfaces of the joint outer part.  
           [0005]    The production of the recess in the pressure element for the purpose of forming the universal ball joint requires a high manufacturing outlay. In order to realize extensive bearing surfaces of the pressure element on the ball body, a curved surface is required to be manufactured with great precision. The installation of the ball body in the pressure element constitutes a further problem. Conventionally, a configuration of the connection as a bayonet connection is required for this purpose.  
         SUMMARY  
         [0006]    It is an object of the present invention to provide a different connection configuration, which may ensure pivoting, between the pressure element and ball body of a tripod joint.  
           [0007]    The above and other beneficial objects of the present invention are achieved by providing a tripod joint as described herein.  
           [0008]    The recess in the pressure body is configured with a cylindrical subregion. The latter may be manufactured with great precision in a simplified manner in comparison to a spherical surface. At least one guide ring is inserted into the pressure body in the region of the cylindrical subregion. This enables the installation options to be expanded. Furthermore, the guide ring may be manufactured from a different material than the pressure body. For example, a, e.g., more expensive, material having improved sliding properties may be used in the region of the at least one guide ring. The ball body is supported with respect to the pressure body via the guide ring. When the guide ring is removed, removal of the pressure element from the ball body may take place, for example. Complex bayonet connections are therefore rendered superfluous. The installation of the pressure body together with the ball body does not require any rotating movement as in the case of a bayonet connection. Furthermore, defined contact regions—in contrast to extensive bearing surfaces—for the transmission of force between the ball body and pressure body may be predetermined by the guide rings.  
           [0009]    In one example embodiment of the present invention, the recess is configured as a cylindrical hole into which two spaced apart guide rings are inserted. In order to manufacture this example embodiment, the hole and the grooves have merely to be made in the pressure element. The guide rings may be produced in large piece numbers.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a longitudinal cross-sectional view of a tripod joint.  
         [0011]    [0011]FIG. 2 is a cross-sectional view of a tripod joint.  
         [0012]    [0012]FIG. 3 is a cross-sectional view of a joint pin with pressure body, cage, rolling bodies and centering elements taken along the line A-A illustrated in FIG. 2.  
         [0013]    [0013]FIG. 4 is a cross-sectional view of a joint pin according to the present invention with pressure element, guide ring, moving cage and rolling bodies taken transversely with respect to longitudinal axis  13 - 13 .  
         [0014]    [0014]FIG. 5 is a cross-sectional view of a further joint pin according to the present invention with pressure element, guide ring, moving cage and rolling bodies taken transversely with respect to longitudinal axis  13 - 13 .  
         [0015]    [0015]FIG. 6 is a cross-sectional view of a further joint pin according to the present invention with pressure element, guide ring, moving cage and rolling bodies taken transversely with respect to longitudinal axis  13 - 13 . 
     
    
     DETAILED DESCRIPTION  
       [0016]    A tripod joint  10  has a joint inner part  11  and a joint outer part  12  holding the latter. The joint inner part  11  and the joint outer part  12  are in each case connected, at least in a rotationally fixed manner, to a driving element of a drive train of a motor vehicle, for example to a drive shaft and a vehicle wheel. The tripod joint  10  is used to transmit a driving torque between the joint inner part  11  and the joint outer part  12  while ensuring a relative displacement along the longitudinal axis  13 - 13  of the joint inner part  11  and along the longitudinal axis  14 - 14  of the joint outer part  12 , a relative pivoting of the joint inner part  11  with respect to the joint outer part  12 , which pivoting is associated with a change in the angle  15  between the longitudinal axes  13 - 13  and  14 - 14 , and a three-dimensional movement which arises from a combination of the abovementioned forms of movement.  
         [0017]    The joint inner part  11  has, at the end on the inside, three pins  16  which are formed as a single piece or a number of pieces together with the latter, are orientated radially and are distributed in each case at 120° in the circumferential direction and form a tripod star. The pins  16  have in each case a partially spherical ball body  17 . In order to transmit forces in both circumferential directions, the ball body  17  bears, in each case in the region of the spherical lateral surface, against a correspondingly configured recess  18  of a pressure element  19 . On the opposite side of the pressure element  19 , which side faces a flat mating surface  20  of the joint outer part  12 , the pressure element is of flat configuration with a running surface  21 .  
         [0018]    The running surface  21  and the mating surface  20  are orientated parallel to each other. Cylindrical rolling bodies  23 , in particular rollers or needles, are held between the latter forming a linear contact. A plurality of rolling bodies are guided in a cage  24  in such a manner that the relative position of the longitudinal axes of the rolling bodies with respect to the cages does not change substantially. In order to transmit circumferential forces in the opposite direction, each pin  16  is configured with two associated pressure elements  19 , the rolling bodies  23  and the surfaces  20 ,  21  symmetrically to a pin central plane accommodating the longitudinal axis  13 - 13 .  
         [0019]    The running surface  21  of a pressure element  19  may have a rectangular form, with the result that as many rolling bodies  23  as possible form a load-bearing contact with the surface pressure being reduced. However, circular or oval pressure elements  19  are also possible.  
         [0020]    The joint outer part  12  has a recess  25  orientated in the direction of the longitudinal axis  14 - 14  with an essentially circular, central hole  26  and three holding spaces  27  which are orientated radially and are distributed in each case at 120° C. in the circumferential direction and are used in each case for holding and supporting a pin  16 , two pressure elements  19  and rolling bodies  23 . In the section illustrated in FIG. 2, the holding spaces  27  have an essentially U-shaped contour open in the direction of the hole  26 , the side limbs of the U-shaped contour being formed with the mating surfaces  20 . In the exemplary embodiment illustrated in FIG. 2, the side limbs are of rectilinear configuration without a transitional region to the mating surfaces  20 . In the direction of the hole  26 , the side limbs do not, in particular, have any projections or depressions, but rather merge into the hole  26  in the end region on the inside with an enlargement of the spacing. In the position of the tripod joint illustrated in FIG. 2, the rolling bodies together with the cage are arranged spaced apart radially from the main limb of the U-shaped contour.  
         [0021]    As illustrated in FIG. 2, the rolling bodies  23  are guided in a cage  24 . The rolling bodies  23  are guided in the cages  24  with the relative position of the longitudinal axes  31  of the rolling bodies  23  with respect to each other being ensured. The cages  24  are guided in the radial direction with respect to the pressure element  19  over shoulders  32  engaging around and enclosing the pressure element  19  (FIGS.  4  to  6 ). The cages  24  may be “clipped” via the shoulders  32  onto the pressure element  19 , as illustrated. The cages  24  may furthermore be centered in the running direction of the rolling bodies  23  via centering or spring elements  33 . Two cages  24  of a pin  16  may be guided and centered via a common spring element  33 .  
         [0022]    For both circumferential directions, the pressure elements  19  assigned to a ball body  17  are connected via two connecting webs  34  to form a pressure body  29  configured as a single piece. According to the example embodiment illustrated in FIG. 3, an introduction of the ball body  17  into the single-piece pressure body  29  may be ensured by a configuration, e.g., a bayonet connection.  
         [0023]    According to the exemplary embodiment illustrated in FIGS. 2 and 3, two spring elements  33  are connected to the pressure body  29  or the ball body  17  via a respective fastening arrangement  36 . The spring elements  33  in each case have two elastic fingers  37  which bear against the opposite cages  24  or are connected thereto, for the purpose of supporting them.  
         [0024]    In comparison with the ball body  17 , the cage  24  having the rolling bodies has, in particular, just two degrees of freedom: a suitably selected connection of the ball body  17  to the pressure body  29  may ensure pivotability about an axis perpendicular with respect to the plane defined by the longitudinal axis  13 - 13  of the joint inner part  11  and the longitudinal axis of the pins  16 . The second degree of freedom is the connection between the cage  24  and pressure body  29 , which connection may be displaced in a translatory manner. In order to ensure the pivotability of the pressure body  29  with respect to the ball body  17 , as illustrated in FIG. 3 the pressure element  29  may hold the ball body  17  in a universal ball joint.  
         [0025]    In a departure from the previously illustrated form of holding in a universal ball joint, according to the present invention, holding occurs as illustrated in FIGS.  4  to  6 .  
         [0026]    According to the exemplary embodiment illustrated in FIG. 4, the recess  18  in the pressure body  29  has a first, cylindrical subregion  40  and a subregion  41  which is adjacent to the latter and corresponds essentially to a subsurface of a hemisphere. In the region of the subregion  41 , the latter bears extensively against the ball body  17 . Spaced apart from the transitional region from the cylindrical subregion  40  to subregion  41 , the cylindrical subregion has a groove  42  into which a guide ring  43  is inserted, in particular with radial expansion. Radially on the inside, the guide ring  43  bears against the ball body  17 .  
         [0027]    As illustrated in FIG. 4, the subregion  41  is arranged between the cylindrical subregion  40  and the central point of the tripod star while, as illustrated in FIG. 5, the cylindrical subregion  40  is arranged between the subregion  41  and the central point of the tripod star.  
         [0028]    An example embodiment of the present invention which may be simple to produce is illustrated in FIG. 6: the recess  18  is, e.g., completely, configured cylindrically in the form of a hole  44  and has two spaced apart grooves  42  with guide rings  43 . In this case, in the center of the two grooves  42  the ball body  17  bears against the hole  44  and against contact surfaces of the guide rings  43  radially on the inside. In the case of guide rings  43  having a different radial extent, the contact region of the ball body  17  may be displaced with the hole  44  out of the center in the direction of the guide ring  43  having a smaller radial extent. It is possible for the ball body  17  to bear only against the two guide rings  43  or against a third guide ring in the center.  
         [0029]    The guide rings  43  may be manufactured from a material having good sliding properties, for example brass. The guide rings  43  have, in particular, a rectangular, circular or oval cross-section or, in the region facing the ball body  17 , have a cross-sectionally concave curvature, in particular with the radius of the ball body  17 . At least one guide ring  43  may be connected fixedly to the pressure body  29 . For example, a guide ring  43  as illustrated in FIG. 6 is manufactured as an inner step of the recess  18  of the pressure body  19  or is connected to the latter with a cohesive material joint. Other forms of connecting the guide rings  43  to the pressure body  29 , in particular form-fitting or frictional forms or forms with a cohesive material joint are possible. For example, at least one guide ring  43  may have an outer thread by which the guide ring  43  may be screwed into the pressure body.  
         [0030]    Instead of the single-piece pressure body  29  illustrated in FIGS.  4  to  6 , the latter may be formed in a number of pieces, in particular with two separate pressure elements  19 .  
         [0031]    The configuration according to the present invention may be suitable for any arrangement of a tripod joint, in particular those based on a ball body  17  guided in a universal ball joint.  
         [0032]    The example embodiments described involve configurations only given by way of example. A combination of the described features for different example embodiments is possible. Further features, in particular features which have not been described, of the device parts belonging to the invention are to be taken from the device-part geometries illustrated in the drawings.