Abstract:
A rolling bearing including an outer ring, an inner ring and two annular, cage-guided rolling body rows, the two rolling body rows being axially pre-stressed by at least one spring element which is disposed therebetween, the two rolling body rows each being pre-stressed against a rim at the end of the outer ring, while the inner ring is axially movable against the restoring force of the spring element.

Description:
FIELD OF THE INVENTION 
     The invention relates to a rolling bearing comprising an outer ring, an inner ring, and two annular, cage-guided rolling body rows. 
     BACKGROUND 
     In some applications it is necessary to support a component so that it can rotate but simultaneously can also move in the axial direction. 
     One example here is the support of control elements in the interior of motor vehicles, e.g., in the form of control knobs such as push-pull actuators. There, plastic sliding bushings are typically used in order to hold the bearing axis of the control knob so that it can rotate and move axially. One such plastic sliding bearing exhibits increased wear over its service life, which leads to oscillations of the friction moment and thus to oscillations of the torque or the pressure force to be applied to the control element. Another disadvantage of the plastic sliding bushings is that they can be adjusted without play in the radial and axial directions only with difficulty. 
     SUMMARY 
     The invention is thus based on the objective of providing a bearing in which, in particular, the play-free setting in the radial and axial directions is improved. 
     The objective is achieved by a rolling bearing of the type name above that is distinguished according to the invention in that the two rolling body rows are pre-stressed in the axial direction by at least one spring element arranged between the two rows, wherein the two rolling body rows are each pre-stressed against a rim at the end of the outer ring, while the inner ring can be moved against the restoring force of the spring element. 
     Consequently, the invention relates to a rolling bearing that is set without play in the axial direction by a spring element. The rolling bodies held in cage-side pockets roll on the outer lateral surface of the inner ring and the inner lateral surface of the outer ring as well as in the area of the rims of the outer ring. The spring element is located between the rolling body rows and generates a force that prestresses the rolling body rows against the rims on the outer ring. Through this prestressing it is guaranteed that the rolling bodies contact the outer ring without play. In this way, undesired sliding and axial play is prevented. An actuation element that is held in the inner ring with its bearing axis is consequently supported so that it can rotate without play and securely in this way. Because the two rolling body rows contact, in addition to the two rims, also the lateral surfaces of the outer ring and the inner ring, the rolling bearing is also set without play in the radial direction in addition to being set without play in the axial direction. This two-row arrangement of the rolling body rows offers greater support against tilting compared with a single-row variant, which is also advantageous for the operation of the control element. 
     Another advantage is provided in that, in addition to freedom from play, a reduction or minimization of the friction can also be achieved by selecting the prestressing generated by the spring element accordingly. If the spring element is produced, e.g., from plastic, through corresponding material selection or variation of the material thickness or the geometry of the spring element, the prestressing can be optimized accordingly. 
     Relative to a sliding bushing, thus a radial and axial setting without play is made possible. The invention also offers the advantages of a rolling bearing, which are realized in the form of a low and constant moment of friction without large fluctuations throughout the service life. 
     Through the movement of the inner ring relative to the outer ring, in addition to the mentioned advantages, the spring element offers the ability to guide the actuation element also during an axial movement caused by pressing on the actuation element. To do this, a bearing axis or a bearing journal of the actuation element is held fixed in the inner ring. Because the inner ring can move against the restoring force of the spring element, a reversible axial movement can be realized, wherein the inner ring is also always guided over the rolling body rows. This produces a safe and play-free guidance of the actuation element, e.g., the control knob of a push-pull actuator, in each degree of freedom of movement. 
     A first embodiment of the invention provides that the spring element is constructed integrally with the cage of one of the two rolling body rows. Through this construction, the manufacturing process can be simplified, because the cage can be injection molded together with the spring element, for example, from plastic. In this way, a simple and economical production can be enabled, because the rolling bearing is also constructed from only a few parts. 
     This invention alternative can be advantageously refined by constructing the one-part cage from two ring sections, of which the first ring section comprises pockets holding the rolling bodies of the first rolling body row and the second ring section is turned toward the second rolling body row. Between the two ring sections there is at least one spring element. Through this refinement of the rolling bearing according to the invention, a uniform force transfer of the spring element to the rolling body rows is made possible, because the spring element transfers its force via the two ring sections to the rolling body rows with its rolling bodies distributed symmetrically in the circumferential direction. 
     Although there is the ability to provide a single annular, surrounding spring element, e.g., in the form of an accordion-like, angled spring section that extends between the ring sections, one refinement of this one-piece invention alternative provides that multiple spring elements are arranged between the ring sections, wherein these spring elements are realized in the form of V-shaped spring bars. Here, the two ends of the V-shaped spring bars are connected to the two ring sections of the cage. In addition, it can be preferred that additional bars are formed between the individual spring bars, wherein these additional bars limit the maximum spring deflection to the extent that they define the minimum distance that the two ring sections can approach each other due to exertion of an axial force on the inner ring. 
     For the simple coupling of the inner ring with the spring element or spring elements for enabling the axial resettable inner ring movement, the invention further provides that the second ring section contacts a radial rim of the inner ring on whose other side the second rolling body row contacts. Through this construction it can be achieved that the force of the spring element is uniformly transferred via the radial rim of the inner ring to the inner ring and thus to the rolling body row contacting the other side of the radial rim. In addition, the inner ring is supported in the axial direction so that a compressive force on the inner ring has the result that the spring element is compressed together via the radial rim. Here, in a simple way a coupling of the inner ring with the spring element is made possible. If an axial force is exerted on the inner ring, the spring element is compressed via the radial rim. When the compressive force is taken away, the inner ring is brought back into the starting position by the restoring force of the spring element. 
     Alternatively, the rolling bearing can be constructed such that a separate spring element is arranged between the cages of the two rolling body rows. In this alternative, a separately produced spring element is formed as a standalone component between the rolling body rows. Therefore, dependent on the application, different prestressing forces that are adapted to the specific application can be generated in the rolling bearing according to the invention by exchanging spring elements of different spring stiffness values. 
     This alternative with a separate spring element can be refined according to the invention in that the cage of the first rolling body row has a ring section on which the similarly annular spring element is supported that contacts the radial rim of the inner ring on the opposite side, wherein the second rolling body row contacts its other side. In addition to a simple coupling of the spring element with the rolling body rows, the spring element can also transfer its force uniformly to the rolling body rows. 
     In this invention alternative, the spring element constructed as a separate part can also have two ring sections between which there are multiple V-shaped spring bars that are attached at their ends directly to the ring sections. 
     Alternatively, the use of other spring elements or shapes of spring bars would also be conceivable, e.g., a metallic helical spring, a spring element made from rubber, a bellows-like spring element, or a similar spring device that enables tensioning of the two rolling body rows against the rims on the outer ring of the rolling bearing. 
     The cage and/or the spring element are preferably made from plastic. Through the production of the cage from plastic, a contact of steel on steel between the cage and the rolling bodies is prevented. This offers the advantage that the bearing generates low noise. In addition, there is the advantage that especially in the embodiment in which the cage has the integrated spring element, the entire element can be produced in one piece by plastic injection molding, for example. This reduces the complexity and costs in the production process. The rolling bodies can likewise be made from steel or plastic, wherein a non-identical material pairing should be considered especially for enabling low-noise running. A production of the cage or the spring element from metal is also possible, as long as elasticity is guaranteed with respect to the spring element. 
     The outer ring and inner ring are finally preferably produced through deep-drawing of a steel sheet. This offers the advantage that the outer ring and inner ring can be produced easily and economically. Here, the outer ring and the inner ring can be made from hard steel or also from soft steel due to the low load. The construction of the outer ring and inner ring from plastic is also conceivable. 
     The rolling bearing according to the invention can also be refined to the extent that at least one disk for sealing the rolling bearing is arranged axially between the rolling body rows and the rims of the outer ring. Through the use of such a disk, a sealing effect can be realized. Therefore, it can be prevented on one hand that dirt and foreign particles can penetrate into the rolling bearing through the open positions between the rims of the outer ring and the outer lateral surface of the inner ring and thus the running properties of the rolling bearing are negatively affected. On the other hand, the attachment of such a disk for sealing is useful to the extent that lubricant loss can be prevented. Both mechanisms contribute to increasing the service life of the rolling bearing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An embodiment of the invention is shown in the drawing and is described in more detail below. Shown are: 
         FIG. 1  a section view through an embodiment of the rolling bearing, 
         FIG. 2  a perspective view of the cage of the rolling bearing from  FIG. 1 , 
         FIG. 3  a section view analogous to  FIG. 1  with deflected inner ring, and 
         FIG. 4  an embodiment of the cage of the rolling bearing with separate spring element. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a cross section of the rolling bearing  1  according to the invention. An outer ring  2  is shown that has radial chamfered rims  3  and  4  on its edges. An inner ring  5  is arranged coaxially within the outer ring  2 . The inner ring  5  has a radial rim  6  that is constructed radially in the direction of the outer ring  2  on the inner ring  5  through corresponding molding. The inner ring  5  and the outer ring  2  are deep-drawn from sheet steel in this embodiment. 
     Between the outer ring  2  and the inner ring  5  there are two cage-guided rolling body rows  7  and  8  comprising multiple rolling bodies in the form of balls. In the axial direction, the first rolling body row  7  contacts the rim  3  of the outer ring  2 . The second rolling body row  8  contacts, viewed axially, between the radial rim  6  of the inner ring  5  and the other rim  4  of the outer ring  2 . Viewed radially, the two rolling body rows  7  and  8  are in contact with the inner lateral surface of the outer ring  2  and the outer lateral surface of the inner ring  5  and roll on these surfaces. The two rolling body rows  7  and  8  are guided in cages  9  and  10 . The cages  9  and  10  have pockets that hold the rolling bodies  11  and  12  of the two rolling body rows  7  and  8 . The cage  9  is made from two ring sections  13  and  14 , wherein the first ring section  13  comprises the pockets holding the rolling bodies  11  of the first rolling body row  7  and the second ring section  14  contacts the radial rim  6 . 
     In the axial direction, multiple spring elements  15  are arranged between the ring section  14  and the ring section  13  in the intermediate space between the outer ring  2  and inner ring  5 . The spring elements  15  are shown in  FIG. 2  in a perspective view. It can be seen that the spring elements  15  run in the circumferential direction, wherein an orientation in the radial direction is to be preferred, because the spring elements  15  would otherwise require additional installation space for compression by a force F and freedom from play in the radial direction would be made more difficult. The spring elements  15  are formed in the shape of V-shaped spring bars  16 . At the ends of the spring bars  16 , these are connected integrally to the two ring sections  13  and  14  and thus integrally to the cage  9 . 
     Between the individual spring bars  16  there are bars  17  on the ring section  13  and facing the ring section  14 . The ring section  14  has recesses  18  that are complementary to the bars  17  and face these bars and in which the bars  17  engage when the spring element is compressed. By the use of these bars  17 , for the use of the rolling bearing in an actuation element formed as a push-pull button, the maximum axial movement travel of the actuation element when pressed can be set. 
     Through the restoring force of the spring elements  15 , the rolling body row  7  is pre-stressed without play by the ring section  13  and the rolling body row  8  is pre-stressed without play by the ring section  14  and the radial rim  6 . The two rolling body rows  7  and  8  here contact, on one hand, at the rims  3  and  4  of the outer ring  2 . In addition, the two rolling body rows  7  and  8  are pre-stressed in the radial direction between the outer lateral surface of the inner ring  5  and the inner lateral surface of the outer ring  2 . Thus, in the rolling bearing  1  according to the invention, play-free prestressing both in the radial and also axial directions is guaranteed. 
     In  FIG. 1  and  FIG. 3  it is also shown that by exerting a force F in the direction of the arrow on the inner ring  5 , this is moved relative to the outer ring  2  axially out of a starting position ( FIG. 1 ) against the restoring force FR generated by the spring element  15  into an axially displaced position ( FIG. 3 ). The inner ring  5  is here guided in each position by the two rolling body rows  7  and  8 . Here, the force F that is given, for example, by an actuation element held fixed in the inner ring with a bearing journal is transferred to the inner ring  5 , to the ring section  14  via the radial rim  6 , and thus onto the spring element  15 . The inner ring  5  or the bearing journal can press onto an element located behind the rolling bearing  1  by this movement relative to the rest of the rolling bearing  1  that is fixed axially in a bearing holder by means of the outer ring  2 . Through the compression of the spring element  15 , the restoring force FR of the spring element  15  is established. In  FIG. 3 , the inner ring  5  deflected out of its starting position and the compressed spring element  15  can be seen. 
     If the actuation element is relaxed again, the inner ring  5  is moved back in the direction of its starting position by the restoring force FR of the spring element  15 , which is shown in  FIG. 1 . 
     In contrast to the integral construction according to  FIGS. 1 to 3 ,  FIG. 4  shows the embodiment of the rolling bearing  1  with separate spring element  19 .  FIG. 4  differs from  FIG. 1  in that—for an otherwise identical construction—the spring element in  FIG. 4  is not connected integrally to the cage as in  FIG. 1 . Instead, the spring element  19  is located as a separate part between the cage  20  of the first rolling body row  7  and the radial rim  6 . In this embodiment, the two ring sections  21  and  22  are part of the spring element  19 . Here, the ring section  21  contacts the ring section  23  of the cage  20  of the first rolling body row  7  and the ring section  22  contacts the radial rim  6 . In this embodiment, the spring element  19  also comprises V-shaped spring bars  16  that generate the prestressing for tensioning the rolling body rows between the radial bars of the outer ring and also the restoring force for the axial displacement of the inner ring. 
     Thus, through the rolling bearing  1  according to the invention it is guaranteed, on one hand, that the two rolling body rows  7 ,  8  are pre-stressed without play in the axial and radial directions by spring-elastic elements  15 ,  19 , whereby the contacts between the rolling bodies  11 ,  12  and the inner ring  5  and outer ring  2  are under slight prestressing, but still generate no significant friction. On the other hand, the spring elements  15 ,  19  make possible a reversible axial movement of the inner ring  5 . 
     LIST OF REFERENCE NUMBERS 
     
         
           1  Rolling bearing 
           2  Outer ring 
           3  Rim 
           4  Rim 
           5  Inner ring 
           6  Radial rim 
           7  Rolling body row 
           8  Rolling body row 
           9  Cage 
           10  Cage 
           11  Rolling body 
           12  Rolling body 
           13  Ring section 
           14  Ring section 
           15  Spring element 
           16  Spring bar 
           17  Bar 
           18  Recess 
           19  Spring element 
           20  Cage 
           21  Ring section 
           22  Ring section 
           23  Ring section