Abstract:
A radial roller bearing, in particular a single-track ball roller bearing, which has an outer bearing ring with an inner groove track, an inner bearing ring with an outer groove track and ball rollers, which are disposed parallel to one another and held in a peripheral direction at even distances from one another by a plastic bearing cage, that roll between the bearing rings in the groove tracks. Each roller has two lateral surfaces that are flattened symmetrically from a spherical base form and a defined axial tilting clearance. The cage has two axially separated, pocketed cage halves which can be assembled in a positive-fitted, form-locked or integral fashion by opposing connecting elements.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to a radial roller bearing according to the features of patent claim  1  which form the preamble, and it can be advantageously realized, in particular, on single track ball roller bearings for high speeds and high requirements for a low noise level, such as in motor vehicle transmissions or within the secondary drive of internal combustion engines. 
       BACKGROUND OF THE INVENTION 
       [0002]    It is generally known in roller bearing technology that the radial roller bearings which are used most frequently are single track and multiple track groove ball bearings, since they are distinguished above all by an equally high radial and axial loadbearing capacity and have the highest rotational speed limits of all radial bearings on account of their low friction. Said groove ball bearings comprise substantially an outer bearing ring and an inner bearing ring and a number of balls, which are arranged between the bearing rings as rolling bodies, which roll in each case in groove-shaped raceways in the inner side of the outer bearing ring and in the outer side of the inner bearing ring and are guided at uniform spacings from one another by a bearing cage. Here, said radial ball bearings are filled with the balls by the eccentric mounting method which has been disclosed by DE 168 499 and in which the two bearing rings are arranged eccentrically with respect to one another and the free space which is produced as a result between the bearing rings is fitted with the balls. 
         [0003]    However, it has been shown in practice that limits are nevertheless placed on groove ball bearings of this type in relation to the loadbearing capacity of the bearing on account of the low maximum number of balls which can be installed and/or the low maximum filling level of approximately 60%. In the past, a multiplicity of solutions were therefore proposed, in which the number of balls and, therefore, the loadbearing capacity of groove ball bearings was to be increased, for example, by the arrangement of filling openings in the raceways. Moreover, another possibility to increase the number of rolling bodies on a radial roller bearing has been disclosed by DE 43 34 195 A1. In this radial roller bearing, which is formed per se as a single track groove ball bearing, the rolling bodies are not formed by balls, however, but rather by what are known as ball rollers, which are configured as balls with two side faces, which are flattened symmetrically from a basic ball shape and are arranged parallel to one another. Here, the width of said ball rollers between their side faces is smaller than the spacing between the inner side of the outer bearing ring and the outer side of the inner bearing ring, with the result that, during filling of the bearing, the ball rollers can be introduced into the bearing, axially with respect to the bearing, through the spacing between the inner ring and the outer ring and can then be rotated by 90° into the raceways of the bearing rings. Since smaller spacings can be achieved between the individual rolling bodies as a result of this mounting method, a higher number of rolling bodies overall can therefore be introduced into the radial roller bearing. 
         [0004]    Since, in ball roller bearings of this type, however, exact axial guidance of the ball rollers is required and, above all, automatic rotation of the ball rollers transversely with respect to the running direction is to be avoided during bearing operation, a plurality of embodiments of corresponding bearing cages are also proposed in the document cited last. Here, one cage embodiment, which is particularly suitable for applications with high requirements, for low noise is a plastic snap action cage which is open on one side and comprises a circumferential solid-walled side ring with pocket webs which extend axially away from it on one side and merge at the level of a plane which is defined by the center points of the ball rollers into in each case two elastically yielding pocket tabs. Here, said pocket tabs are spaced apart from one another by an intermediate space and form in each case in pairs a plurality of cage pockets which spatially surround the running faces of the ball rollers. 
         [0005]    However, it has proven disadvantageous that the entire kinematic behavior of the ball rollers which occurs at different bearing loadings has not been taken into consideration in a snap action cage which is configured in this way. It has thus been determined, for example, that ball rollers as rolling bodies in radial roller bearings roll without offsetting movements stably in their raceways at relatively high speeds and uniform load on account of the gyroscopic effect which occurs, and do not require any axial guidance by the bearing cage. If, however, the bearing rotational speed drops below a permissible minimum rotational speed or the bearing is suddenly accelerated greatly, what is known as a tumbling effect occurs, in particular, in the loadfree zone of the bearing, during which tumbling effect the ball rollers tend to roll in their raceways in an undulating manner transversely with respect to the running direction. Here, first of all contact occurs between the running faces of the ball rollers and the side ring of the snap action cage, by way of which contact friction heat is generated and which contact is the cause of a disadvantageous rise in the operating temperature in the radial roller bearing. Here, the friction between the ball rollers and the bearing cage and the tumbling movements of the ball rollers can become so pronounced that the ball rollers ultimately even snap out of their cage pockets which are open on one side, via the elastically yielding pocket tabs, and stand transversely with respect to their raceways, with the result that destruction of the bearing cage and premature failure of the bearing occur. The ball rollers within a bearing cage of this type likewise have no possibility to orient themselves to the respective contact angle in the case of mixed radial and axial loading of the bearing, without contact between the ball rollers and the side ring of the snap action cage and the resulting disadvantageous consequences likewise occurring. 
       OBJECT OF THE INVENTION 
       [0006]    Proceeding from the described disadvantages of the known prior art, the invention is therefore based on the object of designing a radial roller bearing, particular a single track ball roller bearing, which is configured with a plastic bearing cage, by way of which sufficient axial guidance of the ball rollers is ensured at all times, even at low bearing rotational speeds or at a high bearing acceleration, and transverse positioning of the ball rollers in their raceways can be avoided, and which plastic bearing cage affords the possibility that the ball rollers are automatically oriented to the respective bearing contact angle without contact with the bearing cage, the case of mixed radial and axial loading of the bearing. 
       DESCRIPTION OF THE INVENTION 
       [0007]    According to the invention, this object is achieved in a radial roller bearing according to the preamble of claim  1 , in such a way that the plastic bearing cage comprises two axially divided pocket cage halves of substantially mirror-symmetrical configuration which can be assembled positively, nonpositively or with a material-to-material fit via complementary connecting elements which are arranged so as to lie opposite one another on their dividing faces, and form a separate cage pocket in the mounted state for each ball roller, which cage pocket encloses said ball roller completely, and in which cage pocket the ball rollers have a defined two-sided axial tilting clearance for automatic orientation to the respective bearing contact angle via low-friction linear contacts between their side faces and those longitudinal webs of the cage pockets which lie opposite them. 
         [0008]    Preferred refinements and developments of the radial roller bearing which is configured according to the invention are described in the subclaims. 
         [0009]    Accordingly, it is proposed as claimed in claim  2  in the case of the radial roller bearing which is configured according to the invention that the contour of the cage pockets corresponds substantially to the cross-sectional contour of the ball rollers, the spacing between the longitudinal webs of the cage pockets being greater, however, than the extent of the width of the ball rollers between their side faces. Here, the transverse webs between the cage pockets are of arched configuration in accordance with the diameter of the ball rollers or with the radius of their running faces and are connected via rounded transition regions to the longitudinal webs of the cage pockets. 
         [0010]    Moreover, as claimed in claims  3  and  4 , the radial roller bearing which is configured according to the invention is also distinguished by the fact that the linear contacts between the side faces of the ball rollers and the longitudinal webs of the cage pockets can preferably be produced via compensator webs, which are integrally formed onto the inner sides of the longitudinal webs, extend over the entire diameter of the side faces of the ball rollers and are wedge-shaped in profile cross-section. Here, the height of these wedge-shaped compensator webs corresponds in each case approximately to the spacing of the side faces of the ball rollers from those longitudinal webs of the cage pockets which lie opposite, a small air gap remaining between the compensator webs and the side faces of the ball rollers, however, in order to avoid permanent contact between the ball rollers and the bearing cage. For as long a guidance length as possible, moreover, the crest lines of the compensator webs are advantageously arranged on the pitch circle of the ball rollers and are of rounded configuration in order to prevent premature wear. 
         [0011]    As claimed in claim  5 , it is a further feature of the radial roller bearing which is configured according to the invention that the axial tilting clearance corresponds to an angular range of up to 35° on both sides of the longitudinal center axes of the ball rollers for automatic orientation of the ball rollers to the respective bearing contact angle within the cage pockets. As a result of the arrangement of the longitudinal webs of the cage pockets, which is spaced apart from the side faces of the ball rollers, the ball rollers can therefore perform axial tilting movements without contact with the bearing cage in a pivoting range of overall approximately 70°, which is delimited by the surfaces of the compensator webs on the longitudinal webs of the cage pockets. 
         [0012]    Finally, claim  6  also proposes, as an advantageous refinement of the radial roller bearing which is configured according to the invention, that the complementary connecting elements which are arranged so as to lie opposite one another on the dividing faces of the pocket cage halves are preferably configured on one cage half as journals, which can be pressed into corresponding holes on the other cage half and can be connected to said holes by ultrasonic welding. As an alternative to this, however, it is also possible to connect the two cage halves by way of suitable latching elements on their dividing faces or by adhesive bonding, or to combine the stated connection types with one another. 
         [0013]    In comparison with the roller bearings which are known from the prior art, the radial roller bearing which is configured according to the invention therefore has the advantage that it has a plastic bearing cage which can be assembled from two mirror-symmetrical parts, cannot be dismantled and by way of which it is possible in a simple way to arrange the ball rollers in the same completely enclosing cage pockets and to guide them axially in such a way that the tumbling movements of the ball rollers in their cage pockets, which occur at low bearing rotational speeds or at high bearing acceleration, are avoided effectively. At the same time, it is possible, as a result of low friction linear contacts between the ball rollers and the bearing cage and as a result of defined axial tilting clearances within the cage pockets, that the ball rollers are oriented automatically to the respective contact angle of the ball roller bearing without contact with the bearing cage. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    One preferred embodiment of the radial roller bearing which is configured according to the invention will be explained in greater detail in the following text with reference to the appended drawings, in which: 
           [0015]      FIG. 1  shows an overall view of a ball roller bearing which is configured according to the invention, in an exploded illustration, 
           [0016]      FIG. 2  shows a three-dimensional illustration specifically of the mounted plastic bearing cage, which is filled with ball rollers, of the ball roller bearing which is configured according to the invention, 
           [0017]      FIG. 3  shows a plan view of one cage half of the plastic bearing cage of the ball roller bearing which is configured according to the invention, 
           [0018]      FIG. 4  shows the side view of the cage half of the plastic bearing cage of the ball roller bearing in accordance with  FIG. 3  which is configured according to the invention, and 
           [0019]      FIG. 5  shows an enlarged illustration of the detail X in the side view of the cage half of the plastic bearing cage according to  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
       [0020]    A radial roller bearing, which is configured as a single track ball roller bearing  1 , is clearly apparent from  FIG. 1 , which radial roller bearing  1  comprises substantially an outer bearing ring  2  with an inner groove raceway  3  and an inner bearing ring  4  with an outer groove raceway  5  and a multiplicity of ball rollers  6 , which roll between said bearing rings  2 ,  4  in the groove raceways  3 ,  5  and in each case have two side faces  7 ,  8  which are flattened symmetrically from a basic ball shape and are arranged parallel to one another. It can likewise be seen in  FIG. 1  that the ball rollers  6  are held at uniform spacings from one another in the circumferential direction by a plastic bearing cage  9  which, according to the invention, comprises two axially divided pocket cage halves  10 ,  11  of substantially mirror-symmetrical configuration which can be assembled positively, nonpositively or with a material-to-material fit via complementary connecting elements  14 ,  15  which are arranged so as to lie opposite one another on their dividing faces  12 ,  13 . 
         [0021]    Moreover, it becomes clear from  FIG. 2  that the two pocket cage halves  10 ,  11  form a separate cage pocket  16  in the mounted state for each ball roller  6 , which cage pocket  16  encloses said ball roller  6  completely and in which cage pocket  16  the ball rollers  6  have a defined two-sided axial tilting clearance  19 ,  20  for automatic orientation to the bearing contact angle via low-friction linear contacts between their side faces  7 ,  8  and those longitudinal webs  17 ,  18  of the cage pockets  16  which lie opposite them. In a clearly discernible manner here, the contour of the cage pockets  16  corresponds substantially to the cross-sectional contour of the ball rollers  6 , the spacing between the longitudinal webs  17 ,  18  of the cage pockets  16  being greater, however, than the extent of the width of the ball rollers  6  between their side faces  7 ,  8 , and those transverse webs  21  between the cage pockets  16  which are of arched configuration in accordance with the diameter of the ball rollers  6  being connected via rounded transition regions  22 ,  23  (shown in greater detail in  FIGS. 4 and 5 ) to the longitudinal webs  17 ,  18  of the cage pockets  16 . 
         [0022]    Furthermore,  FIGS. 3 ,  4  and  5  show that the linear contacts between the side faces  7 ,  8  of the ball rollers  6  and the longitudinal webs  17 ,  18  of the cage pockets  16  can preferably be produced via compensator webs  24 ,  25  which are integrally formed onto the inner sides of the longitudinal webs  17 ,  18 , extend over the entire diameter of the side faces  7 ,  8  of the ball rollers  6  and are of wedge-shaped configuration in profile cross-section. Here,  FIG. 5  makes it clear that the wedge height of the compensator webs  24 ,  25  on the inner sides of the longitudinal webs  17 ,  18  of the cage pockets  16  corresponds, in each case, approximately to the spacing of the side faces  7 ,  8  of the ball rollers  6  from those longitudinal webs  17 ,  18  of the cage pockets  16 , which lie opposite, while it is indicated in  FIG. 3  that the crest lines  26 ,  27  of the compensator webs  24 ,  25  are arranged on the pitch circle  28  of the ball rollers  6 . 
         [0023]    Finally, it is also apparent from  FIGS. 1 and 5  that the axial tilting clearance  19 ,  20  corresponds to an angular range of approximately 35° on both sides of the longitudinal center axes of the ball rollers  6  for automatic orientation of the ball rollers  6  to the respective bearing contact angle within the cage pockets  16 , with the result that the ball rollers can perform axial tilting movements without contact with the plastic bearing cage  8  in a pivoting range of a total of approximately 70°, which is delimited by the surfaces of the compensator webs  24 ,  25  on the longitudinal webs  17 ,  18  of the cage pockets  16 . Here, those complementary connecting elements  14 ,  15  for the two cage halves  10 ,  11 , which are arranged so as to lie opposite one another on the dividing faces  12 ,  13  of the pocket cage halves  10 ,  11  are configured on one cage half  11  as journals  29 , which can be pressed into corresponding holes  30  on the other cage half  10  and can be connected to said holes  30  by ultrasonic welding. 
       List of Designations 
       [0000]    
       
           1  Ball Roller Bearing 
           2  Outer Bearing Ring 
           3  Groove Raceway in  2   
           4  Inner Bearing Ring 
           5  Groove Raceway in  4   
           6  Ball Rollers 
           7  Side Face on  6   
           8  Side Face on  6   
           9  Plastic Bearing Cage 
           10  Pocket Cage Half of  9   
           11  Pocket Cage Half of  9   
           12  Dividing Face on  10   
           13  Dividing Face on  11   
           14  Connecting Elements on  12   
           15  Connecting Elements on  13   
           16  Cage Pockets in  9   
           17  Longitudinal Web of  16   
           18  Longitudinal Web of  16   
           19  Axial Tilting Clearance in  16   
           20  Axial Tilting Clearance in  16   
           21  Transverse Webs of  16   
           22  Transition Region to  17   
           23  Transition Region to  18   
           24  Compensator Web on  17   
           25  Compensator Web on  18   
           26  Crest Line of  24   
           27  Crest Line of  25   
           28  Pitch Circle of  6   
           29  Journals on  12   
           30  Holes in  13