STEERING SHAFT FOR A MOTOR VEHICLE

Abstract

A steering shaft for a motor vehicle includes a hollow shaft and an inner shaft which is arranged coaxially in the hollow shaft. The inner shaft is configured to be telescoped relative to the hollow shaft in the direction of the longitudinal axis of the steering shaft and is connected in a torque-transmitting manner to the hollow shaft via at least one rolling body. The rolling body is received in a rolling body cage such that it can roll in the direction of the longitudinal axis between the inner shaft and the hollow shaft. In order to achieve a high operational reliability with a relatively low manufacturing complexity, the rolling body cage has at least one seal element which bears sealingly against the hollow shaft and/or the inner shaft.

Claims

1.-10. (canceled)

11. A steering shaft for a motor vehicle, comprising: a hollow shaft; an inner shaft arranged coaxially in the hollow shaft; and a rolling body received in a rolling body cage, the rolling body disposed between the inner shaft and the hollow shaft and configured to roll in the direction of a longitudinal axis of the steering shaft so as to permit the inner shaft to telescope relative to the hollow shaft in the direction of the longitudinal axis; and a seal element disposed on the rolling body cage that is configured to bear and seal against one or both of the hollow shaft or the inner shaft.

12. The steering shaft of claim 11, wherein the seal element is configured so as to run around the rolling body cage.

13. The steering shaft of claim 11, wherein at least two seal elements are received in the rolling body cage and spaced axially apart from one another.

14. The steering shaft of claim 11, wherein the seal element is configured to run around on a circumferential face of the rolling body cage.

15. The steering shaft of claim 14, wherein the seal element encloses the rolling body or a group of rolling bodies.

16. The steering shaft of claim 11, wherein the seal element is of elastic configuration.

17. The steering shaft of claim 11, wherein at seal element is connected fixedly to the rolling body cage.

18. The steering shaft of claim 11, wherein the seal element is configured integrally in one piece with the rolling body cage.

19. The steering shaft of claim 11, wherein the rolling body cage is configured as a plastic injection molded part.

20. The steering shaft of claim 11, wherein a spatial region defined between the seal element and the rolling body cage and/or the inner shaft and/or the hollow shaft is filled at least partially with a lubricant.

Description

DESCRIPTION OF THE DRAWINGS

[0027] Advantageous embodiments of the invention will be described in greater detail in the following text using the drawings, in which, in detail:

[0028] FIG. 1 shows a diagrammatic perspective view of a steering shaft,

[0029] FIG. 2 shows a partial view of a steering shaft according to FIG. 1 in an exploded state,

[0030] FIG. 3 shows a longitudinal section along the longitudinal axis through the steering shaft according to FIG. 1,

[0031] FIG. 4 shows a cross-section B-B through the steering shaft according to FIG. 3,

[0032] FIG. 5 shows a perspective view of the anti-friction bearing cage of the steering shaft according to FIG. 1 in a first embodiment,

[0033] FIG. 6 shows a perspective view of an exploded steering shaft as in FIG. 2 with an anti-friction bearing cage in a second embodiment, and

[0034] FIG. 7 shows a cross section A-A through the steering shaft according to FIG. 6 in the assembled state.

EMBODIMENTS OF THE INVENTION

[0035] In the various figures, identical parts are always provided with the same designations and will therefore as a rule also be cited or mentioned in each case only once.

[0036] FIG. 1 shows a perspective view of a diagrammatically shown steering shaft 1 which has a hollow shaft 20 (also called an outer shaft or outside shaft) and an inner shaft 30 (also called an inside shaft) which can be telescoped with respect to one another in the direction of the longitudinal axis L, that is to say in the axial or longitudinal direction which is indicated by way of the double arrow.

[0037] At its free end which faces away in the longitudinal direction with regard to the inner shaft 30, the hollow shaft 20 has a fork 21 which forms a part of a universal joint, by way of which the steering shaft 1 is connected in a torque-transmitting manner to the steering line. In a corresponding manner, at its free end which faces away in the longitudinal direction with regard to the hollow shaft 20, the inner shaft 30 has a fork 31 which forms a part of a further universal joint, by way of which the steering shaft 1 is connected in a torque-transmitting manner to the steering line. The shafts 20 and 30 are preferably both manufactured as hollow profiles from steel which can be cold formed in a satisfactory manner.

[0038] FIG. 2 shows the steering shaft 1 according to FIG. 1 in an exploded illustration, in which the inner shaft 30 is shown pulled out of the hollow shaft 20 in the direction of the longitudinal axis L.

[0039] Rolling bodies which are configured as balls 40 are arranged between the hollow shaft 20 and the inner shaft 30, as can be seen clearly in the longitudinal section in FIG. 3.

[0040] In its inner face, the hollow shaft 20 has grooves 22 which are continuous in the longitudinal direction, and the inner shaft 30 has corresponding grooves 32 which lie radially opposite said grooves 22 and serve as rolling body raceways for the balls 40, that is to say form ball raceways. The balls 30 are arranged between said grooves 22 in such a way that they can roll therein in the direction of the longitudinal axis L and therefore form a linear anti-friction bearing system for a telescoping relative movement of the inner shaft 30 and the hollow shaft 20. Moreover, the balls 40 act as positively locking elements which engage into the grooves 22 and 32 in a positively locking manner with regard to a relative rotation about the longitudinal axis L, as a result of which they transmit a torque which is introduced into the inner shaft 30 as a steering torque to the hollow shaft 20. In the example which is shown, in each case four grooves 22 and 32 are arranged distributed about the longitudinal axis L in the circumferential direction. The inner shaft 30 is configured as a solid shaft. It is likewise conceivable and possible, however, that the inner shaft 30 is configured as a hollow shaft.

[0041] The balls 40 are received in an anti-friction bearing cage 50 which is configured as a ball cage. The anti-friction bearing cage 50 has a rolling body receptacle 51 for each of the balls 40 in the form of a radially continuous opening, in which in each case one ball 40 is received such that it can rotate freely with play and projects radially to the inside and to the outside to such an extent that it can roll in the grooves 22 and 32 in the longitudinal direction in an unimpeded manner.

[0042] In each case a plurality of rolling body receptacles 51 are arranged in the longitudinal direction in each case at a spacing A from one another, with the result that the balls 40 which are received therein in each case form an axial ball row 41, comprising in each case six balls 40 in the example which is shown, which balls 40 can roll between grooves 22 and 32 which lie opposite one another radially in each case in pairs. By way of the rolling body cage 50, the balls 40 of the ball rows are guided at the spacing A from one another in the case of a telescoping relative movement of the inner shaft 30 and the hollow shaft 20.

[0043] In the embodiment according to FIGS. 2, 3, 4 and 5, the rolling body cage 50 has seal elements 52 according to the invention, of which in each case one is arranged in an axial end region of the rolling body cage 50.

[0044] FIG. 4 shows an axial view from the left of a cross section B-B through the steering shaft 1 according to FIG. 3 (indicated by way of the arrow as in FIG. 3). It can be seen from this that the seal element 52 tightly fills the radial, substantially annular cross section of the intermediate space between the inner shaft 30 and the hollow shaft 20. Here, on its outer circumference which forms an outer circumferential sealing face 521 with regard to the longitudinal axis L, the seal element 52 bears sealingly from the inside against the inner face of the hollow shaft 20. On its inner circumference, the seal element 52 has an inner circumferential sealing face 522, by way of which it bears sealingly against the outer face of the inner shaft 30. As can be seen clearly from FIG. 4, the sealing faces 521 and 522 follow the cross-sectional contours of the inner shaft 30 and the hollow shaft 20 which is configured as an outer shaft including the grooves 32 and 22, with the result that the inner shaft 30 is sealed against the hollow shaft 20. In other words, the seal element 52 brings it about that the anti-friction bearing cage 50 is guided in the longitudinal direction in a sealed manner as a type of annular piston between the hollow shaft 20 and the inner shaft 30. Here, the seal element 52 is dimensioned in such a way that the circumferential play permits smooth sliding of the rolling body cage 50 in the direction of the longitudinal axis L, but as far as possible prevents an entry of contaminants between the inner shaft 30 and the hollow shaft 20 and also an escape of lubricant from the intermediate space between the inner shaft 30 and the hollow shaft 20.

[0045] It is apparent from FIG. 3 that in each case one seal element 52 is arranged in an axial end region of the rolling body cage 50. By way of the above-described sealing means, a sealed spatial region 60 is delimited axially by way of the two seal elements 52 over the length of the rolling body cage 50 between the inner shaft 30 and the hollow shaft 20. As a consequence, said spatial region 60 is enclosed by way of the two seal elements 52, the sections of the hollow shaft 20 and the inner shaft 30, which sections extend over the length of the anti-friction bearing cage 50, and the surface regions of the antifriction bearing cage 50 which lie between the seal elements 52.

[0046] Lubricant, namely lubricating grease, is introduced into the spatial region 60, with the resuit that the spatial region 60 serves as a lubricant container. As a result, the balls 40 which are likewise situated in the spatial region 60 are surrounded by lubricating grease, with the result that their rolling movement in the grooves 22 and 32 and also in the rolling body receptacles 51 is lubricated in the case of a telescoping relative movement of the hollow shaft 20 and the inner shaft 30.

[0047] The lubricant is enclosed in a sealed manner by way of the seal elements 52 according to the invention in the spatial region 60 which is also moved with the rolling body cage 50 in the direction of the longitudinal axis L. This ensures that there is sufficient lubricating grease for sufficient lubrication in the region of the balls 40 in the long term, even after a multiplicity of longitudinal adjustments of the steering shaft 1. Here, the lubricant is not distributed irregularly over the entire length of the adjusting region as in the prior art, with the result that a smaller quantity of lubricating grease is sufficient. The undesired escape of lubricant from the hollow shaft 20 is largely prevented by way of the seal elements 52, as is the entry of contaminants into the spatial region 60, which entry might impair the lubricating action.

[0048] As is shown individually in an exposed manner in FIG. 5, the rolling body cage 50 including the seal elements 52 according to the invention can be produced as a single-piece integral component, preferably as a plastic injection molded part. Here, the rolling body cage 50 can be manufactured from a single thermoplastic material, for example from polyoxymethylene (POM), polypropylene (PP) or the like, or the body of the rolling body cage 50, in which the rolling body receptacles 51 are configured, is molded from a first thermoplastic polymer which has a high mechanical strength, and the seal elements 52 are molded from a rubber-like, elastic thermoplastic elastomer onto the body of the rolling body cage 50, likewise using the injection molding process. As a result of the elastomer, for example, sealing lips can be molded which run around along the sealing faces 521 and 522. Sealing lips of this type are elastically deformable and bear resiliently against the hollow shaft 20 and the inner shaft 30, as a result of which a particularly satisfactory sealing effect is achieved, and at the same time a smooth displaceability of the rolling body cage 50 remains ensured.

[0049] A second embodiment of the invention is shown in FIGS. 6 and 7. Therein, a seal element is configured as a web-shaped outer sealing lip 53 which is arranged on the outside on the anti-friction bearing cage 50. A further seal element is configured as a web-shaped inner sealing lip 54 which is arranged on the inside on the anti-friction bearing cage 50. The sealing lips 53 and 54 enclose in each case one surface region of the circumferential face, in which surface region a ball row 41 is situated which is formed from a plurality of balls 40 which are arranged in the longitudinal direction, from six balls 40 in the example which is shown.

[0050] The sealing lips 53 and 54 run in the longitudinal direction in each case along both sides of a ball row 41, and transversely with respect thereto in the circumferential direction over the circumference of shaped parts 55. The shaped parts 55 are of similar shape to the seal element 52 of the first embodiment according to FIG. 4 in the region of the grooves 22 and 32, and fill the groove cross section. As a result, the sealing lips 53 and 54 on the shaped parts 55 bear sealingly against the grooves 22 and 32, respectively.

[0051] The outer sealing lip 53 seals the enclosed region, in which the balls 40 of the ball row 41 are situated, against the hollow shaft 20. The inner sealing lip 54 seals the enclosed region, in which the balls 40 of the ball row 41 are situated, against the inner shaft 30. In a corresponding manner, in each case one spatial region 61 is enclosed by way of the seal elements according to the invention in the form of the sealing lips 53 and 54 and the surface regions of the hollow shaft 20 and the inner shaft 30 which are enclosed by in each case one sealing lip 53 or 54, in which spatial region 61 one or a plurality of balls 40 of a ball row 41 is/are situated. Accordingly, four spatial regions 61 of this type are configured in the example which is shown with four ball rows 41 which are arranged in the circumferential direction. As described above for the spatial region 60, the spatial regions 61 are filled with lubricant, for example lubricating grease. As a result, each of the spatial regions 61 forms a lubricant container for in each case one of the ball rows 41.

[0052] As described above for the spatial region 60, the balls 40 are supplied in the spatial regions 61 with lubricating grease. The sealing lips 53 and 54 likewise ensure that no contaminants pass to the balls 40, and also that no lubricant escapes to the outside.

[0053] The sealing lips 53 and 54 can enclose in each case one ball row 41 sealingly, or else can enclose groups of balls 40 within a ball row 41, or else can enclose individual balls 40. In every case, one or more sealed spatial regions is/are provided by way of seal lips 53 and 54 according to the invention, which spatial region 61 are moved together with the rolling body cage 50 and in which spatial regions 61 the balls 40 are received.

[0054] The sealing lips 53 and 54 can be configured in one piece with the anti-friction bearing cage 50, and can preferably be manufactured using plastic injection molding. It is possible here that the anti-friction bearing cage 50 including the sealing lips 53 and 54 is molded from a thermoplastic polymer. Furthermore, it is one advantageous possibility that the body of the anti-friction bearing cage 50, in which the balls 40 are received, is molded from a mechanically resilient polymer, and the sealing lips 53 and 54 are molded in one piece onto the body from a rubber-like elastic elastomer.

[0055] As an alternative, it is conceivable and possible that the sealing lips 53 and 54 or seal elements 52 are separately manufactured completely or in part and are provided for subsequent mounting on the anti-friction bearing cage 50. For example, sealing lips 53 and 54 can be formed by way of O-rings which are made from an elastomer material and are fastened to the rolling body cage 50, for example by way of insertion into circumferential groove-like depressions. O-rings of this type can also be used on sealing elements 52, for circumferential sealing against the hollow shaft 20 and the inner shaft 30.

LIST OF DESIGNATIONS

[0056] 1 Steering shaft [0057] 20 Hollow shaft [0058] 21 Fork [0059] 22 Groove [0060] 30 Inner shaft [0061] 31 Fork [0062] 32 Groove [0063] 40 Ball [0064] 41 Ball row [0065] 50 Rolling body cage [0066] 51 Rolling body receptacle [0067] 52 Seal element [0068] 521, 522 Sealing face [0069] 53, 54 Sealing lips [0070] 55 Shaped part [0071] 60, 61 Spatial region [0072] L Longitudinal axis [0073] A Spacing