STEERING SHAFT FOR A MOTOR VEHICLE

Abstract

A steering shaft may include a hollow shaft in which an inner shaft is arranged telescopically coaxially in an axial direction. A rolling body may be held in a form fit manner in a circumferential direction and configured to roll in the axial direction in a rolling body holding element of a rolling body cage disposed between the inner and hollow shafts, which is arranged in the axial direction between radially projecting stop elements of the hollow shaft and of the inner shaft. The rolling body cage may have end-face axial support surfaces that are oriented in the axial direction against the stop elements. The rolling body cage may have at least one transfer element extending axially between the end-face axial support surfaces.

Claims

1.-11. (canceled)

12. A steering shaft for a motor vehicle comprising: an inner shaft; a hollow shaft in which the inner shaft is disposed telescopically coaxially in an axial direction; and a rolling body held in a form-fit manner in a circumferential direction and configured to roll in the axial direction in a rolling body holding element of a rolling body cage disposed between the inner shaft and the hollow shaft, which is disposed in the axial direction between radially projecting stop elements of the hollow shaft and radially projecting stop elements of the inner shaft, wherein the rolling body cage includes end-face axial support surfaces that are oriented in the axial direction against the radially projecting stop elements, wherein the rolling body cage includes a transfer element extending axially between the end-face axial support surfaces.

13. The steering shaft of claim 12 wherein the transfer element is at least one of harder, more rigid, or stronger than the rolling body holding element.

14. The steering shaft of claim 12 wherein the transfer element has a material thickening.

15. The steering shaft of claim 12 wherein the transfer element is comprised at least partially of a material that is at least one of harder, more rigid, or stronger than a material of the rolling body holding element.

16. The steering shaft of claim 15 wherein the material of the transfer element is metallic.

17. The steering shaft of claim 12 wherein the rolling body holding element is an injection-molded plastic part.

18. The steering shaft of claim 12 wherein the transfer element and the rolling body holding element are joined together by at least one of form fit, force locking, or material bonding.

19. The steering shaft of claim 12 wherein the transfer element comprises a reinforcement element.

20. The steering shaft of claim 12 wherein the transfer element is one of a plurality of transfer elements of the rolling body cage.

21. The steering shaft of claim 12 wherein the rolling body cage is sleeve shaped.

22. A rolling body cage for a steering shaft, the rolling body cage comprising: a rolling body holder for holding a rolling body in a freely rotatable manner; and axial support surfaces; and a transfer element disposed axially between the support surfaces.

23. The rolling body cage of claim 22 wherein the steering shaft is the steering shaft of claim 12.

Description

DESCRIPTION OF THE DRAWINGS

[0030] Advantageous embodiments of the invention are explained more closely in the following with the aid of the drawings. Specifically, there are shown:

[0031] FIG. 1 a schematic perspective view of a steering shaft,

[0032] FIG. 2 a partial view of a steering shaft according to FIG. 1 in the disassembled condition,

[0033] FIG. 3 a partial view of the inner shaft of a steering shaft according to FIG. 1 in the disassembled condition,

[0034] FIG. 4 a cross section through the steering shaft according to FIG. 1,

[0035] FIG. 5 a longitudinal section A-A through the steering shaft according to FIG. 1,

[0036] FIG. 6 a schematic perspective view of the rolling body cage of the steering shaft according to FIG. 1,

[0037] FIG. 7 a second embodiment of a steering shaft in a perspective partial view,

[0038] FIG. 8 a cross section through the steering shaft according to FIG. 7,

[0039] FIG. 9 a longitudinal section B-B through the steering shaft according to FIG. 7,

[0040] FIG. 10 a third embodiment in a cross section,

[0041] FIG. 11 a fourth embodiment in a cross section.

EMBODIMENTS OF THE INVENTION

[0042] In the various figures, the same parts are given the same reference numbers in each case and therefore as a rule are only named or mentioned once.

[0043] FIG. 1 shows in perspective view a schematically represented steering shaft 1, comprising a hollow shaft 20, also known as an outer shaft, and an inner shaft 30, which are mutually telescopic in the axial direction of the longitudinal axis L, i.e., in the axial or longitudinal direction indicated by the double arrow.

[0044] The hollow shaft 20 comprises at its free end, which is facing away from the inner shaft 30 in the longitudinal direction, a fork 21, which is part of a universal joint by which the steering shaft 1 is connected in torque-locking fashion to the steering train, not further shown. Accordingly, the inner shaft 30 has at its free end, which is facing away from the hollow shaft 20 in the longitudinal direction, a fork 31, which forms part of a further universal joint by which the steering shaft 1 is connected in torque-locking fashion to the steering train. The hollow shaft 20 is fabricated preferably as a hollow profile made from good cold-workable steel. The inner shaft 30 in the example shown is configured as a solid shaft. Alternatively, however, it may also be provided that the inner shaft 20 is configured as a hollow shaft.

[0045] FIG. 2 shows the steering shaft 1 of FIG. 1 in an exploded view, where the inner shaft 30 is shown pulled out from the hollow shaft 20 in the direction of the longitudinal axis L.

[0046] Between the hollow shaft 20 and the inner shaft 30 there are arranged rolling bodies in the form of balls 4, as can be seen in the cross section of FIG. 4 and in the longitudinal section of FIG. 5.

[0047] The hollow shaft 20 has grooves 22 running in its inner surface in the longitudinal direction, and the inner shaft 30 has corresponding radially opposite grooves 32, serving as rolling body running tracks for the balls 4, i.e., forming ball running tracks. The balls 4 are arranged between these grooves 22 and 32 such that they can roll in them in the direction of the longitudinal axis L and thus form a linear roller bearing for an axial telescopic relative movement of the inner shaft 30 and the hollow shaft 20. Furthermore, the balls 4 serve as form-fit elements, which engage by form fitting in the grooves 22 and 32 regarding a relative rotation about the longitudinal axis L, thereby transmitting a torque introduced as a steering torque into the inner shaft 30 to the hollow shaft 20, or vice versa. In the example shown, four respective grooves 22 and 32 are distributed in the circumferential direction about the longitudinal axis L. The inner shaft 30 in the example shown is configured as a solid shaft. Alternatively, however, it is also conceivable and possible for the inner shaft 30 to be configured as a hollow shaft.

[0048] The balls 4 are held in a rolling body cage 5, which is configured as a ball cage. The roller bearing cage 5 comprises a rolling body holder 51 for each of the balls 4 in the form of a radially continuous opening, in which a ball 4 is held with play so as to turn freely about its ball center, and protruding radially inwardly and outwardly so that it can roll unhindered in the grooves 22 and 32 in the longitudinal direction.

[0049] The arrangement of the rolling body cage 5 with inserted balls 4 mounted on the inner shaft 30 is shown in FIG. 3, showing a perspective view of the free end 33 of the inner shaft 30, which in the assembled state of FIG. 1 plunges into the opening of the hollow shaft 20.

[0050] In each case a plurality of rolling body holders 51 is arranged with an axial spacing from each other in the longitudinal direction, so that the balls 4 held therein in each case form an axial row of balls 41, in the example shown consisting of six balls 4 in each case. The rolling body holders 51 for the balls 4 of one row of balls 41 are formed in each case in a rolling body holding element 52. In the circumferential direction, each of the four rolling body holding elements 52 shown in the example extends in the area of the grooves 22 and 32.

[0051] In the circumferential direction, transfer elements 53 according to the invention are arranged between the rolling body holding elements 52, the four rolling body holding elements 52 and likewise four transfer elements 53 being arranged alternately in the circumferential direction and joined together. Thanks to this arrangement, the rolling body cage 5 has the shape of a sleevelike hollow profile with octagonal cross section, whose side surfaces are formed alternately by rolling body holding elements 52 and transfer elements 53.

[0052] In the embodiment shown in FIGS. 3 to 6, the rolling body holding elements 52 comprise form-fit elements 521 and the transfer elements 53 comprise form-fit elements 531, which mesh together in form fitting. The form-fit elements 521 are formed as strip-like protrusions running in the longitudinal direction with an undercut head-shaped cross section, by which they can interlock by form fitting with the corresponding form-fit elements 531 in the transfer elements 53, formed as undercut grooves, in the circumferential direction. In addition or alternatively, the connection can be by material bonding, for example by gluing or ultrasonic welding.

[0053] The transfer elements 53 each have an axial support surface 54 on their two axial end faces. In other words, each of the transfer elements 53 extends between its support surfaces 54. At the one end face, facing toward the end 33, one of the support surfaces 54 lies opposite a respective stop element 34 in the axial direction, which projects radially outward from the inner shaft 30. Such a stop element 34 is formed for example by a plastically deformed region, such as a caulking, which protrudes into the gap between the inner shaft 30 and the hollow shaft 20, as is shown in the longitudinal section through the assembled steering shaft 1 in FIG. 5.

[0054] The support surfaces 54 on the other end face, which is facing away from the end 34, lie opposite a respective stop element 24 in the axial direction, which protrudes inwardly from the inside of the hollow shaft 20 radially into the gap between the inner shaft 30 and the hollow shaft 20. A stop element 24 can likewise be formed by a caulking, as shown, which comprises a plastically deformed region in the radial direction.

[0055] The stop elements 24 and 34 protrude into the gap between the hollow shaft 20 and the inner shaft 30 in which the transfer elements 53 move forward or back during an adjustment of the steering shaft 1 in the direction of the longitudinal axis L. When the steering shaft 1 is pulled apart, the stop elements 24 and 34 move toward each other until they come to lie against said support surfaces 54 on the rolling body cage 5 lying in between.

[0056] FIG. 4 shows a cross section through the steering shaft 1. This reveals the octagonal cross section in its basic form, with the grooves 22 and 32 distributed evenly around the circumference in every second side surface, between which are arranged the rolling body holding elements 52 with the balls 4. On the side surfaces lying in between in the circumference, the transfer elements 53 according to the invention are situated in the gap between the inner shaft 30 and the hollow shaft 20.

[0057] FIG. 5 shows in a cut-out view in the longitudinal section A-A of FIG. 4 the stop situation with the steering shaft 1 pulled out to the maximum. Here, a relative pull-out force F is acting on the hollow shaft 20 and the inner shaft 30. Thanks to the stop elements 34 and 24, this pull-out force F is transmitted as a compressive force to the support surfaces 54. The two oppositely directed force arrows indicate how the pull-out force F acts axially on the transfer element 53. The transfer element 53 is more loaded with compression in the longitudinal direction the larger the pull-out force F is.

[0058] In order to make sure that no harmful deformation of the rolling body holding elements 52 occurs due to large pull-out forces F, the transfer elements 53 according to the invention have a higher dimensional rigidity than the rolling body holding elements 52, especially in regard to an axial loading. For example, the transfer elements 53 can be made of steel, preferably as cold-worked parts, as sintered metallic parts, as die-cast parts or as injection-molded parts. Thanks to their relatively simple shape as a continuous profile segment in the longitudinal direction with constant cross section, a rational production as an endless semifabricated product is possible, from which transfer elements 53 are cut off in the length dictated by the rolling body cage 5. Thanks to the high strength and hardness, the transfer elements 53 made of metallic material even with relatively small material cross sections already withstand high compressive forces with no risk of plastic deformation.

[0059] The rolling body holding elements 52 are preferably formed as injection-molded plastic parts made from thermoplastic elastomer or thermoplastic material. In this way, a complex shaping can be realized with no problems in order to configure the rolling body holders 51, and a rational production is possible. The elastic plastic furthermore makes it possible for the rolling body holders 51 to be at least partly springlike elastic, for example with resilient holding elements, so that the balls 4 can be snapped in in a springlike fashion and are held captively in loose form fit, making the handling and assembly process easier. The form-fit elements 521 for connection to the transfer elements 53 may likewise be realized easily, for example as resilient latching elements with form fit locking.

[0060] Due to the relatively slender construction and the relatively soft plastic, the rolling body holding elements 52 can only absorb a slight force. This function is taken over by the transfer elements 53 according to the invention, so that the rolling body holding elements 52 remain essentially force-free even under large bearing forces. Accordingly, even under high peak loading there is no danger of impairing the function of the roller bearing cage 5.

[0061] The transfer elements 53 fill up the polygonal cross section of the gap between the hollow shaft 20 and the inner shaft 30 as can be seen in FIG. 4. In this way, they form form-fit elements with regard to a relative rotation of the hollow shaft 20 and the inner shaft 30, which are in a loose form fit in the operating condition shown, i.e., not lying, or at least not lying at the same time, against the hollow shaft 20 and the inner shaft 30. In an emergency, when balls 4 are damaged or have been removed from the grooves 22 and 32, the transfer elements 53 can take over the function as form-fit elements, making possible the transmitting of a steering torque. Thus, the transfer elements 53 can additionally provide a redundant torque transmission between the hollow shaft 20 and the inner shaft 30. For this additional function, it is likewise advantageous that the transfer elements are made from a dimensionally stiff, preferably metallic material, such as steel. In this way, the safety level of the steering shaft and thus of a steering column is heightened.

[0062] FIG. 6 shows yet again a rolling body cage 5 according to the preceding figures in an individual perspective representation without balls 4.

[0063] In FIGS. 7, 8 and 9 is shown a second embodiment of a steering shaft 1, in views corresponding to FIGS. 3, 4 and 5. FIG. 9 shows a section B-B according to FIG. 8.

[0064] The inner shaft 30 is configured the same as in the previous embodiment. The rolling body holding elements 52 are likewise configured identically, at least in regard to the arrangement of the balls 4. The rolling body holding elements 52 here are joined together by weblike connection elements 55 in ring fashion in the circumferential direction to form a sleevelike structure, which together with the rolling body holding elements 52 is formed as a single piece of injection-molded plastic. This can be seen well in the cross section of FIG. 8.

[0065] The connection element 55 furthermore serves as a fastening element, which can be used for the fastening in a form-fit element 532 in the form of a corresponding recess or indentation in the transfer element 53 by form fit. The holding action can be provided by locking elements (not shown), static friction, or additionally or alternatively by gluing or ultrasound welding. The arrangement in the assembled state can be seen in FIGS. 8 and 9, the longitudinal section B-B in FIG. 9 showing the form-fitting engagement of the connection element 55 in the form-fit element 532. In this way, the transfer element 53 is held securely in position on the rolling body cage 5.

[0066] FIG. 10 shows in a cross section view like FIGS. 4 and 7 a third embodiment. Here, in each case two rolling body holding elements 52 are joined together as a single piece by a connection element 55, preferably in the form of an injection-molded plastic part. The two rolling body holding elements 52 are joined together to form an overall sleeve-shaped rolling body cage 5 by means of two transfer elements 53, which may be configured the same way as in the embodiment of FIG. 4. Corresponding form-fit elements 521, 531 can likewise be provided for the connection.

[0067] A further possible embodiment is shown likewise in cross section in FIG. 11. Here, in each case two individual, separate rolling body holding elements 52, which may be designed similar to FIG. 4, are joined together across a transfer element 53, which can be designed similar to FIG. 10 or 4. Contrary to the preceding embodiments, the rolling body cage 5 is not a single closed piece in the form of a sleeve, but rather is divided into two in the area 25 of the gap in the longitudinal direction. This produces a segmented design, making possible a radial mounting on the inner shaft 30.

[0068] It can be seen with the aid of the different embodiments according to FIGS. 4, 7, 10 and 11 that the combination according to the invention of rolling body holding elements 52 and transfer elements 53 makes possible a flexible adapting to different requirements.

LIST OF REFERENCE NUMBERS

[0069] 1 Steering shaft [0070] 20 Hollow shaft [0071] 21 Fork [0072] 22 Groove [0073] 24 Stop element [0074] 25 Gap [0075] 30 Inner shaft [0076] 31 Fork [0077] 32 Groove [0078] 33 End [0079] 34 Stop element [0080] 4 Ball [0081] 41 Row of balls [0082] 5 Rolling body cage [0083] 51 Rolling body holder [0084] 52 Rolling body holding element [0085] 521 Form-fit element [0086] 53 Transfer element [0087] 531 Form-fit element [0088] 532 Form-fit element [0089] 54 Support surface [0090] 55 Connection element [0091] L Longitudinal axis [0092] F Pull-out force