Abstract:
An axial bearing in a transmission and a transmission having transmission elements adjacent to an axial bearing, particularly a stepless transmission, are provided. The axial bearing has a running surface or the orientation thereof predetermined directly by a shaft nut, in contrast with prior axial bearings, in which run-up disks form an additional component that must be precisely aligned with regard to adjacent components, so that parallel running surfaces result for the axial bearing.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     Applicants claim priority under 35 U.S.C. §119 of German Application No. 103 53 130.0 filed Nov. 14, 2003.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a bearing having a first transmission element and a second transmission element, which are mounted to rotate about an axis relative to one another, and which are supported against one another in the direction of the axis, by way of an axial bearing, wherein the first transmission element has a shaft nut, by means of which positional fixation of another transmission element disposed on the first transmission element takes place. Beyond that, the invention relates to the use of such bearings in stepless transmissions.  
         [0004]     2. The Prior Art  
         [0005]     In known bearings, a first transmission element as well as a second transmission element are mounted to rotate relative to one another about an axis. An axial support of the transmission elements in the direction of the aforementioned axis takes place by way of an axial bearing.  
         [0006]     In order to guarantee the function of the axial bearing, it is necessary that precisely parallel running surfaces, oriented crosswise for support in the direction of the aforementioned axis, are present, which are assigned to the first transmission element, for one thing, and to the second transmission element, for another thing. If the orientation of the running surfaces does not lie within a narrow tolerance band, problems can occur. These problems include vibration excitation of the transmission elements, function impairment, increased wear, failure of the axial bearing, and/or a reduction of the useful lifetime of the axial bearing. In order to avoid these problems, it is known to provide the running surface on running bodies whose orientation is precisely predetermined, in each instance, by means of area contact of the running bodies on the transmission elements. The area contact can involve, for example, a fit of an inside diameter of the running body with an outside diameter of a shaft, an outside diameter of the running body and an inside diameter of an adjacent transmission element, or a contact surface oriented crosswise to the longitudinal axis of the running body on an adjacent transmission element.  
       SUMMARY OF THE INVENTION  
       [0007]     It is an object of the present invention to provide a bearing and a use of a bearing, which guarantees sufficient functioning of the axial bearing with low effort and expenditure for the component and/or for assembly, as well as for material use.  
         [0008]     These and other objects are achieved by providing a bearing according to the inventions which makes use of a shaft nut by means of which positional fixation of another transmission element disposed on a transmission element, such as a gear wheel or a bearing body, takes place. According to the invention, a face of this shaft nut forms a running surface for roller bodies of the axial bearing.  
         [0009]     The invention is therefore based on the recognition that the use of a special, i.e. additional running body for presenting the running surface for the roller bodies of the axial bearing is not absolutely necessary. Instead of such an additional running body, the shaft nut finds multifunctional use, since it serves, on the one hand, to form the running surface for the roller bodies of the axial bearing and, on the other hand, for fixing the position of the other transmission element. With this arrangement, the invention overcomes the prejudice of a person skilled in the art, that a precise predetermination of an orientation of a face of a shaft nut is allegedly not possible. This prejudice results from the belief that the predetermination of an exact positional angle of the shaft nut by way of the connection of the thread of the shaft nut with the corresponding thread of the first transmission element is not possible. By means of the multifunctional use of the shaft nut in accordance with the invention, the additional component of a running body is therefore not necessary. In this way, construction space and/or weight for the bearing can be saved.  
         [0010]     In another aspect, a bearing is provided in which the roller bodies of the axial bearing roll on a run-up disk. An orientation of the run-up disk is exclusively predetermined by the shaft nut, in accordance with the invention. According to this aspect, a predetermination of the orientation of the running surface for the roller bodies takes place by way of the thread of the shaft nut. In this connection, the run-up disk can support itself particularly on an inside surface on a cylindrical mantle surface of the shaft nut and/or on a face of the shaft nut oriented crosswise to the longitudinal axis of the shaft nut. This aspect of the invention also makes use of the recognition that a precise predetermination of the position of a running surface is possible by way of the shaft nut.  
         [0011]     Preferably, the run-up disk lies against an axial face of the shaft nut. A continuation of the shaft nut is passed through the run-up disk, lying radially on the inside. The continuation and/or other components connected with it, lying on the inside or in the partial region that projects out of the run-up disk, can fulfill additional functionalities. These functionalities include preventing rotation of the shaft nut, particularly with related wedging regions, or making available another bearing surface.  
         [0012]     According to another embodiment of the bearing, the axial bearing has two run-up disks that enclose the roller bodies. In this case, the run-up disks are connected with one another by way of a cage. The axial bearing thereby forms a compact structural unit. For such a configuration, a non-precise and parallel orientation of the running surfaces leads to additional stress on the cage that connects the run-up disks, which, in the worst case, can result in mechanical failure of the cage. According to the invention, a predetermination of the orientation of the running surfaces also takes place by way of the shaft nut, in this case.  
         [0013]     A use of one of the aforementioned bearings in a stepless transmission that has a variator equipped with a looping means is of particular advantage. In this case, the first transmission element is configured as a variator shaft. The variator shaft is connected to rotate with a disk of the variator. A second transmission element is fixed in place axially on the variator shaft, by means of a shaft nut. For example, the additional transmission element is a roller bearing, by means of which the variator shaft is supported relative to a transmission housing. An adjacent second transmission element is axially supported relative to the variator shaft by way of an axial bearing. In accordance with a first variant of the invention, the face of the shaft nut that lies opposite the additional transmission element, forms a running surface for roller bodies of the axial bearing. The additional transmission element may be, for example, the roller bearing. In accordance with a second variant of the invention, the face of the shaft nut that lies opposite the additional transmission element exclusively determines the orientation of a run-up disk on which roller bodies of the axial bearing roll.  
         [0014]     The aforementioned advantages of the bearing according to the invention are adapted to be used in a stepless transmission having a variator. This use results in a particularly precise configuration of a stepless drive, particularly a particularly short variator shaft, and a particularly light configuration and/or one having few components.  
         [0015]     Preferably, the second transmission element can be connected with a transmission brake, so that support of the variator shaft takes place relative to a second transmission element fixed in place in the housing, in the switching state in question.  
         [0016]     In accordance with a further embodiment of the invention, the second transmission element connected with the transmission brake is configured for bearing at least one planet of a planetary gear set. The second transmission element thereby has a ridge for bearing the at least one planet. In this way, the bearing according to the invention can be integrated into the stepless transmission particularly well, taking over several functions.  
         [0017]     According to another specific embodiment, the bearing is used in a stepless transmission. In this case, the first transmission element is designed as a variator setting shaft. A means or device that acts together with the adjustment of the variator is axially fixed in place on the variator setting shaft, by way of the shaft nut. The aforementioned means is, for example, a setting piston for which the shaft nut predetermines an end position, or a centrifugal oil hood, see in this regard the German patent application DE 199 20 063 A1. Since the aforementioned means has both a radial and an axial expanse, small inaccuracies in the predetermination of the orientation of the means result in magnified deviations of the end surfaces of the means. For the case of the setting piston, these deviations cause an insufficient sealing effect or an increased wear of the seals of the setting piston provided in the end regions to occur. In the worst case, jamming of the setting piston can occur. Comparable problems also result for the centrifugal oil hood. Even for such intensified conditions, the inventors have recognized that a predetermination of the orientation of the means can take place according to the invention, by way of the setting nut. In this case, as well, the recognition according to the invention results in a reduced expenditure and effort for components, a simplified assembly and/or a reduced expenditure of material, and less required installation space.  
         [0018]     According to another embodiment, two bearings according to the invention are used in the stepless transmission. The first bearing is for bearing one transmission element relative to the variator shaft. The second bearing is for bearing another transmission element relative to the variator setting shaft. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]     Other objects and features of the present invention will become apparent from the following detailed description considered in connection with the accompanying drawings. It should be understood, however, that the drawings are designed for the purpose of illustration only and not as a definition of the limits of the invention.  
         [0020]     In the drawings, wherein similar reference characters denote similar elements throughout the several views:  
         [0021]      FIG. 1  shows a detail of a first example of a bearing according to the invention,  
         [0022]      FIG. 2  shows a detail of a second example of a bearing according to the invention,  
         [0023]      FIG. 3  shows a detail of a third example of a bearing according to the invention,  
         [0024]      FIG. 4  is a gear plan of a stepless transmission,  
         [0025]      FIG. 5  shows a detail of a stepless transmission having a bearing according to an embodiment of the invention, and  
         [0026]      FIG. 6  shows a detail of a stepless transmission having an alternative configuration of a bearing according to the invention.  
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0027]     Turning now in detail to the drawings, FIGS.  1  to  3  show the fundamental structure of alternative configurations of an axial bearing. In this connection, the support between a first component  100  and a second component  101  takes place with the guarantee of a relative twist of the components  101  about an axis X-X as well as under axial support.  
         [0028]     According to  FIG. 1 , an axial bearing  102  is disposed between faces of components  100 ,  101  that are oriented parallel and crosswise to axis X-X, which bearing has roller bodies  103  as well as a cage  104  that holds roller bodies  103 .  
         [0029]     An axial bearing  110  shown in  FIG. 2  has roller bodies  111 , a cage  112  that holds the roller bodies  111 , and a run-up body  113 . Run-up body  113  is designed to be L-shaped in cross-section. Run-up body  113  has a vertical run-up disk  114  and a horizontal part  115 . Horizontal part  115  is disposed on the side of axial bearing  110  facing axis X-X or, instead, on the side facing away from axis X-X. While roller bodies  111  roll directly on the faces of second component  101 , the roller bodies roll on run-up disk  114 , which rests against the face of first component  100  over a large area or the entire area, on the opposite side.  
         [0030]     According to an exemplary embodiment shown in  FIG. 3 , an axial bearing  120  has roller bodies  121 , a cage  122  holding the roller bodies, as well as run-up bodies  123 ,  124 . Run-up body  123  is designed to correspond to run-up body  113  according to  FIG. 5  and is disposed between the face of first component  100  and roller bodies  121 . Run-up body  124  is designed to be L-shaped in cross-section. The vertical part of the L-shaped cross-section of run-up body  124  forms a run-up disk  125 , which is oriented parallel to the run-up disk of run-up body  123 . Run-up body  124  furthermore has a horizontal part  126 , which is disposed on the side of roller bodies  121  that lies opposite the horizontal part of run-up body  123 . First and/or second component  100 ,  101  is/are preferably a shaft nut according to the invention, a first transmission element and/or a second transmission element. The faces of components  100 ,  101 , as shown, as well as of run-up bodies  113 ,  114  as well as  123 ,  124  are oriented approximately parallel to one another as well as crosswise to axis X-X.  
         [0031]     The aforementioned axial bearings are preferably used in a transmission, preferably a stepless transmission  10  of a motor vehicle having front or rear wheel drive.  
         [0032]     In the case of the stepless transmission  10  shown in  FIG. 4 , an engine shaft  11  is connected with a transmission input shaft  13  by way of a hydrodynamic torque converter  12 . Hydrodynamic torque converter  12  has a converter bridging coupling and suitable vibration damping devices. Transmission input shaft  13  is connected with the drive disk set  14  of a variator  15 , so as to rotate with it, which variator can be adjusted by means of a setting unit  16 . Drive disk set  14  is in a drive connection with the power take-off disk set  18 , which has a first disk  19  as well as a second disk  20 , by way of a looping means  17 . Power take-off disk set  18  has a setting unit  21  for stepless adjustment of the translation of variator  15  assigned to it.  
         [0033]     Disk  20  is in a drive connection with a transmission shaft  23 , by way of an intermediate transmission  22 . Transmission shaft  23  passes axially through power take-off disk set  18 . On the side of variator  15  that faces away from intermediate transmission  22 , transmission shaft  23  bears a gear wheel  24 . Gear wheel  24  is part of a transmission stage  25 . By means of transmission stage  25 , a transfer off the moment of transmission shaft  23  to an intermediate shaft  26 , which in turn is in a drive connection with a distributor transmission  27 , takes place.  
         [0034]     Intermediate transmission  22  has a variator shaft  28  that is configured as a hollow shaft, through which transmission shaft  23  is passed and which is connected to rotate with disk  20 , in an axial end region. In the opposite end region, variator shaft  28  bears a gear wheel  29  as well as a coupling disk  30 , which are disposed closely adjacent to one another. Gear wheel  29  is part of a planetary gear set  31 , which furthermore has planets  32  as well as a ring gear  33 . Ring gear  33  is connected to rotate with transmission shaft  23 . A ridge  34  of planets  32  can be connected with the transmission housing by way of a brake  35 . Coupling disk  30  can be connected with ring gear  33 , i.e. transmission shaft  23 , by way of a coupling  36 .  
         [0035]     In accordance with the exemplary embodiment shown in  FIG. 5 , disk  20  is configured in one piece with the variator shaft  28 . Variator shaft  28  has four partial regions  37  to  40 , starting with disk  20 , which regions are arranged in the aforementioned sequence, one behind the other. Each partial region  37 ,  38 ,  39 ,  40  has a narrowing in cross-section. The partial regions are connected with one another in each instance by way of a respective undercut.  
         [0036]     Partial region  37  bears a roller bearing  41  on its cylindrical mantle surface.  
         [0037]     Partial region  38  has an outside thread onto which the threaded nut  42  is screwed on. An inner ring of the roller bearing  41  is fixed or clamped in place axially between a facing face of disk  20  and a face  43  of shaft nut  42 . Face  43  is disposed crosswise to the axis of rotation X-X of disk  20 , variator shaft  28 , and transmission shaft  23 .  
         [0038]     Partial region  39  has radial recesses taken out of the cylindrical mantle surface, in which tenon regions  44  that are formed by axial continuations of shaft nut  42  engage.  
         [0039]     In the region of the mantle surface of partial region  40 , a positive-lock connection of variator shaft  28  with gear wheel  29  is formed, for example by means of a dovetail gearing or a feather key. Gear wheel  29  is axially displaceable relative to partial region  40 .  
         [0040]     Shaft nut  42  has a face  45  on the side facing away from disk  20 , which face is oriented parallel to face  43 . Ridge  34  has a circular ring-shaped continuation  46  radially on the inside, which continuation is configured to be approximately U-shaped in the cross- section shown. The side shanks of U-shaped continuation  46  are formed by faces  47 ,  48 . Gear wheel  29  has faces  49 ,  50 . Transmission shaft  23  has a face  51 . The faces  43 ,  45 ,  47 ,  48 ,  49 ,  50 ,  51  are oriented parallel to one another and crosswise to axis X-X.  
         [0041]     An axial bearing  52  is disposed between faces  45 ,  47 . Axial bearing  52  corresponds to the exemplary embodiment shown in  FIG. 3 , in a mirror-image installation position. In this embodiment, component  100  is formed by shaft nut  42  and component  101  is formed by ridge  34 , i.e. by continuation  46 . Axial bearing  52  has two run-up bodies  123 ,  124 , between which roller bodies  121  disposed in a cage  122  are accommodated. Run-up body  124  facing shaft nut  42  is designed to be L-shaped in cross-section. The vertical part of the L-shaped cross-section forms a run-up disk  125 , which rests against shaft nut  42  over a large part or its entire area in the region of the face  45 , and on which the roller bodies  121  roll on the side facing away from shaft nut  42 .  
         [0042]     The radially inside end region of run-up disk  125  makes a transition into the horizontal partial region  126  of the L-shaped cross-section. Horizontal part  126  is oriented approximately parallel to axis X-X. A radial play is provided between run-up body  124  and shaft nut  42 , so that run-up body  124  is in contact with shaft nut  42  merely in the region of run-up disk  125 . The run-up disks  125 ,  127  are oriented crosswise to axis X-X. Run-up body  123  disposed on the side of axial bearing  52  facing away from shaft nut  42  also has an L-shaped cross-section. The horizontal part  128  of the L-shaped cross-section of run-up body  123  is disposed radially outside of the vertical part (run-up disk  127 ). Run-up disk  127  makes contact with face  47  of ridge  34 , while horizontal part  128  finds (precisely fitted) accommodation in a collar  53  of ridge  34 . Run-up bodies  123 ,  124  are connected with one another firmly, i.e. elastically, by way of a cage Preferably, horizontal parts  126 ,  128  of run-up bodies  123 ,  124  form radial guides for the roller bodies.  
         [0043]     An axial bearing  54  is disposed between faces  48 ,  49 , whereby axial bearing  54  is configured with mirror symmetry to a plane oriented crosswise to the axis X-x to axial bearing  52 . Axial bearing  54  corresponds to the exemplary embodiment shown in  FIG. 3 , whereby component  100  is formed with ridge  34 , i.e. continuation  46 , and component  101  is formed with gear wheel  29 . Axial bearings  52 ,  54  have essentially the same diameter. The outside diameter of axial bearings  52 ,  54  essentially corresponds to the outside diameter of shaft nut  42 , i.e. of gear wheel  29 .  
         [0044]     An axial bearing  55  is disposed between faces  50 ,  51 . Axial bearing  55  corresponds to the exemplary embodiment according to  FIG. 2 . In this embodiment, component  100  is formed with gear wheel  29  and component  101  is formed with face  51 , i.e. with a related shoulder of transmission shaft  23 . Axial bearing  55  merely has a run-up body  113 , which is disposed between roller bodies  111  and gear wheel  29 . On the side lying opposite run-up body  113 , roller bodies  111  roll directly on face  51  of transmission shaft  23 . By means of predetermining, i.e. setting the distance between faces  51  and  45 , a bias of axial bearings  52 ,  54 ,  55  can be predetermined.  
         [0045]      FIG. 6  shows a setting unit  21  that has a setting piston  60  as well as a centrifugal oil hood  61 . With regard to the structure and function of the setting unit, as well as the components involved and their interaction, reference is made to the German patent DE 199 20 063 C1, with its entire scope. This patent shows a variator that has a rotary shaft and a piston-cylinder device which rotates with the shaft for setting the position of an axially adjustable cone disk of a cooperating cone disk pair for a transmission belt in a continuously variable transmission. The piston-cylinder device has at least one pressure chamber and at least one compensation chamber, for compensating the centrifugal force during the rotation of the piston-cylinder device, receiving the pressure medium via four radial channels.  
         [0046]     As shown in  FIG. 6 , a setting piston  60  as well as a centrifugal oil hood  61  each have circular ring-shaped end regions  62 ,  63 , which are oriented crosswise to axis X-X Disk  20  is connected to rotate with a variator setting shaft  64 . In the exemplary embodiment shown in  FIG. 3 , variator setting shaft  64  and disk  20  are configured in one piece. In the end region of variator setting shaft  64  facing away from disk  20 , the shaft has partial regions  65 ,  66 ,  67 , and  68 , in that sequence. Partial regions  65  to  68  follow one another with a reduction in cross-section, in each instance and, in particular, with the interposition of a respective undercut.  
         [0047]     In the transition from partial region  65  to partial region  66 , a shoulder  69  is formed. The face of end region  62  that faces away from a shaft nut  70  makes contact with shoulder  69  in a contact region oriented crosswise to axis X-X. Partial region  66  has a cylindrical mantle surface, which is surrounded by a cylindrical inside surface of end regions  62 .  63 . End regions  62 ,  63 , on the one hand, and the cylindrical mantle surface of partial region  66 , on the other hand, form a fit, particularly a transition or press fit, or a gap.  
         [0048]     Partial region  67  has an outside thread onto which shaft nut  70  is screwed on. Partial region  68  possesses radial recesses out of a cylindrical mantle surface, into which tenon regions  71  that are formed by axial continuations of the shaft nut enter.  
         [0049]     By tightening shaft nut  70  on variator setting shaft  64 , the face  72  of shaft nut  70  and the face  73  of end region  63 , the opposite face  74  of end region  63 , and the facing face  75  of end region  62 , as well as the opposite face  76  of end region  62 , and shoulder  69 , can be braced against one another. Faces  72 ,  73 ,  74 ,  75 ,  76  are oriented parallel to one another and essentially crosswise to axis X-X. The precise orientation of centrifugal oil hold  61  as well as of setting piston  60  is predetermined by means of the aforementioned faces.  
         [0050]     Shaft nut  70  has an extension  80 , in the form of a hollow cylinder, on the side facing away from setting unit  21 , which is followed by tenon region  71 . Extension  80  and tenon region  71  enter into a corresponding recess out of the gear wheel  24 , at least in part. Extension  80  has a cylindrical mantle surface. An axial bearing  83  is disposed between a face  81  of the shaft nut that faces away from face  72  of shaft nut  70 , and a face  82  of gear wheel  24 . The roller bodies of the axial bearing  83  roll directly on face  82  of gear wheel  24 . The roller bodies of axial bearing  83  are guided in a cage. On the side facing away from gear wheel  24 , the roller bodies of axial bearing  83  roll on a circular ring-shaped run-up disk  84 . Run-up disk  84  surrounds extension  80  of shaft nut  70 , forming a fit or a connection with radial play, and lies against face  81  of shaft nut  70  on the side facing away from axial bearing  83 .  
         [0051]     Axial bearing  83  therefore corresponds to axial bearing  102  shown in  FIG. 1 , whereby component  100  is formed by gear wheel  24  and component  101  is formed by run-up disk  84 .  
         [0052]     The threads of shaft nut  70  and related partial region  67 , as well as of shaft nut  42  and related partial region  38 , are usual threads. In particular, a fine-pitch thread and/or a thread having elevated requirements with regard to the production tolerances may be used.  
         [0053]     The axial bearings that are used are also referred to as multi-purpose bearings.  
         [0054]     Shaft nuts  42 ,  70  as well as the related threads are produced from forged blanks with subsequent lathing work in this connection, the lathing contour has hardly any effect on the costs of the shaft nuts. Contact disks or surfaces can therefore be implemented in almost cost-neutral manner, by forming these disks or surfaces, according to the invention, directly or indirectly by the shaft nut. The invention goes against the prejudice of the art that a precise predetermination of the orientation of a shaft nut is not possible. If a bearing runs up on the shaft nut, large bearing diameters having a high support number and a long lifetime can be implemented. By running the axial bearing up on the nut, the bearing can be removed from the determining axial component chain of the shaft. This arrangement results in a clearly reduced transmission construction length.  
         [0055]     Accordingly, although only a few embodiments of the present invention have been shown and described, it is to be understood that many changes and modifications may be made thereunto without departing from the spirit and scope of the invention as defined in the appended claims.