STEERING SHAFT FOR A MOTOR VEHICLE

Abstract

A steering shaft for a vehicle includes a hollow outer shaft arranged telescopically and coaxially about an inner shaft and connected in a torque-transmitting manner via at least one rolling body. The rolling body bears against the inner shaft and the outer shaft in a positively locking manner in the circumferential direction with regard to a rotation about the longitudinal axis. The steering shaft includes a securing element fixed on the outer shaft and a torque-transmitting coupling section via which the inner shaft and the outer shaft are connected. For an improved redundant transmission of torque in the case of the failure of rolling bodies, the coupling section has at least one transmission body which engages in a loose positively locking connection with regard to a rotation about the longitudinal axis between the rolling body raceways of the inner shaft and the outer shaft.

Claims

1.-11. (canceled)

12. A steering shaft for a motor vehicle, the steering shaft comprising: a hollow outer shaft; an inner shaft arranged coaxially within the outer shaft, the inner shaft configured to telescope relative to the outer shaft in the direction of a longitudinal axis of the steering shaft; a rolling body that connects in a torque-transmitting manner the outer shaft to the inner shaft; wherein the rolling body is configured to roll in the direction of the longitudinal axis, said rolling body bearing against the inner shaft and against the outer shaft in a positively locking manner between rolling body raceways in the circumferential direction with regard to a rotation about the longitudinal axis; and a securing element fixed on the outer shaft, the securing element comprising a coupling section disposed between the inner shaft and the outer shaft and configured, in a torque-transmitting manner, to connect the inner shaft and the outer shaft; wherein the coupling section includes a transmission body which engages in a loose positively locking connection with regard to a rotation about the longitudinal axis between the rolling body raceways of the inner shaft and the outer shaft.

13. The steering shaft of claim 12 wherein the coupling section has a carrier, in which at least one separate transmission body is receivable.

14. The steering shaft of claim 13 wherein the carrier has at least one fastening means, on which the transmission body is fixable.

15. The steering shaft of claim 13 wherein the transmission body consists of a transmission body material, and the carrier consists of a carrier material which is different than said transmission body material.

16. The steering shaft of claim 15 wherein the transmission body material is harder and/or stronger and/or stiffer than the carrier material.

17. The steering shaft of claim 12 wherein the coupling section has connecting means which is configured to connect to the outer shaft in a positively locking and/or non-positive and/or integrally joined manner.

18. The steering shaft of claim 12 wherein the number of transmission bodies corresponds to the number of rolling body raceways.

19. The steering shaft of claim 12 wherein said transmission body has a smaller cross-sectional area than said rolling body.

20. The steering shaft of claim 12 where said transmission body has a higher shear strength with regard to a shear in the circumferential direction between rolling body raceways which lie radially opposite one another than one of the rolling bodies which are arranged therein.

21. The steering shaft of claim 12 wherein the carrier has an outwardly projecting collar which is configured to be supported on the outer shaft.

22. The steering shaft of claim 12 wherein the securing element is configured as a pull-out securing means which prevents complete pulling out of the inner shaft from the outer shaft.

Description

DESCRIPTION OF THE DRAWINGS

[0023] Advantageous embodiments of the invention will be described in greater detail in the following text on the basis of the drawings, in which, in detail:

[0024] FIG. 1 shows a diagrammatic perspective view of a steering shaft according to the invention,

[0025] FIG. 2 shows a part of a steering shaft according to FIG. 1 in a disassembled state,

[0026] FIG. 3 shows a diagrammatic perspective detailed view of the steering column according to FIG. 1,

[0027] FIG. 4 shows the detail shown in FIG. 4, in a disassembled state,

[0028] FIG. 5 shows the securing element of the steering column according to FIGS. 2 to 4 in a disassembled state,

[0029] FIG. 6 shows a longitudinal section through a second embodiment of a steering column according to the invention,

[0030] FIG. 7 shows a detailed view of the longitudinal section according to FIG. 6,

[0031] FIG. 8 shows a cross section A-A of the steering column according to FIG. 6, and

[0032] FIG. 9 shows a detailed view of the cross section according to FIG. 8.

EMBODIMENTS OF THE INVENTION

[0033] In the various figures, identical parts are always provided with the identical designations and will therefore as a rule also be named or mentioned in each case only once.

[0034] FIG. 1 shows a perspective view of a diagrammatically illustrated steering shaft 10 which has an outer shaft 20 (also called an outside shaft or hollow shaft) and an inner shaft 30 (also called an inside hollow shaft) which can be telescoped with respect to one another in the direction of the longitudinal axis L, that is to say in the longitudinal direction which is indicated by way of the double arrow.

[0035] At its outer end which faces away from the inner shaft 30 in the longitudinal direction, the outer shaft 20 has a fork 21 which forms a part of a universal joint, by way of which the steering shaft 10 can be connected to the steering line in a moment-transmitting manner. In a corresponding manner, at its outer end which faces away from the outer shaft 20 in the longitudinal direction, the inner shaft 30 has a fork 31 which can form a part of a further universal joint, by way of which the steering shaft 10 can be connected to the steering line in a moment-transmitting manner. The inner shaft 20 and the outer shaft 30 are preferably manufactured from steel with satisfactory cold forming properties.

[0036] The inner shaft 30 is inserted coaxially into the open internal cross section of the outer shaft 20, and can be displaced in a telescoping manner longitudinally in both directions relative to said outer shaft 20, as indicated in FIG. 1 by way of the double arrow.

[0037] FIG. 2 shows a part of the steering shaft 1 according to FIG. 1 in an exploded illustration, in the case of which the individual constituent parts are shown pulled apart from one another in the longitudinal direction, that is to say in the direction of the longitudinal axis L. It is apparent from this that the outer shaft 20 is profiled in its circumferential region which faces the inner shaft 30 and into which the inner shaft 30 can be pushed in the longitudinal direction as indicated by way of the arrow. The profiling of the outer shaft 20 comprises rolling body raceways which are configured as grooves 22 and extend in the inner circumferential surface in the longitudinal direction. Convexly projecting bead-like shaped-out formations are configured in the outer circumferential surface so as to lie opposite the grooves 22 on the outside with regard to the wall of the outer shaft 20. In the embodiment which is shown, both the inner shaft 30 and the outer shaft 20 are configured as hollow profiles with a substantially square cross-sectional basic shape. Here, a total of four grooves 22 are arranged distributed uniformly over the circumference of the outer shaft 20, namely in each case in the center of one of the sides of said square cross section. The grooves 22 are configured as rolling body raceways, specifically as ball raceways.

[0038] That end section of the inner shaft 30 which faces the outer shaft 20 and can be pushed in a telescoping manner into the latter is likewise profiled, as shown in FIG. 1. The profiling likewise comprises rolling body raceways in the form of grooves 32 which extend from the end which can be plugged into the outer shaft 20 in the outer circumferential surface of the inner shaft 30 in the longitudinal direction, that is to say in the direction of the longitudinal axis L. The grooves 32 extend over that part section of the inner shaft 30 which can be pushed into the outer shaft 20 in the longitudinal direction.

[0039] Balls 40 are arranged as rolling bodies between the inner shaft 30 and the outer shaft 20 in the rolling body raceways which are delimited by way of grooves 22 and 32 which lie radially opposite one another in each case in pairs. In each case a plurality of (in the example which is shown in FIG. 2, six) balls 40 are arranged behind one another in the longitudinal direction in each case in a rolling body raceway. Here, they are held at a defined spacing relative to one another such that they can be rotated freely in a sleeve-shaped rolling body cage or ball cage 50.

[0040] In normal operation, the balls 40 lie in the grooves 22 and 32, and roll or turn therein in the case of a relative displacement in the longitudinal direction between the outer shaft 20 and the inner shaft 30, with the result that a smooth-running and secure roller-mounted linear guide is formed. By virtue of the fact that the cross section of the balls 40 fills the rolling body raceways in a positively locking manner, which rolling body raceways are delimited by way of the grooves 22 and 32, said balls 40 produce a positively locking connection in the circumferential direction between the inner shaft 30 and the outer shaft 20 and, as a consequence, a torque-transmitting connection. As a result of the positively locking connection, an introduced steering moment can be transmitted practically without play between the inner shaft 30 and the outer shaft 20.

[0041] A securing element 70 according to the invention is inserted in the longitudinal direction into the opening of the outer shaft 20, as indicated in FIG. 2 and FIG. 4 by way of the arrow, until the assembly position which is shown in FIG. 3 is reached.

[0042] The securing element 70 has a carrier 71 which comprises a coupling section 72 and a collar 73 which projects radially to the outside from the latter. The coupling section 72 has a hollow profile section-shaped basic shape which can be inserted with play into the intermediate space between the inner shaft 30 and the outer shaft 20. In the example which is shown, the coupling section 72 has a total of four receptacles 74 as fastening means.

[0043] The carrier 70 including the collar 73 and the coupling section 72 with the receptacles 74 is manufactured as a plastic injection molded component from thermoplastic polymer which forms the so-called carrier material.

[0044] In each case one transmission body 8 (in the example which is shown, a cylindrical pin or bolt) is attached in the receptacles 74, which transmission body 8 consists of a transmission body material which has a higher strength than the abovementioned carrier material, for example steel. The transmission bodies 8 have a longitudinal axis Z and a smaller diameter than the balls 40.

[0045] The receptacles 74 are formed and dimensioned as open recesses in such a way that in each case one transmission body 8 can be snapped into said receptacles 74 with elastic widening of the plastic, for example in the radial insertion direction, as indicated by way of the arrows in the state shown in FIG. 5 before the assembly. In the assembled state which is ready for installation, as shown in FIGS. 2, 3 and 4, each transmission body 8 is held in a receptacle 74 in a positively locking manner. As an alternative or in addition, a non-positive and/or integrally joined fastening can take place, for example by way of adhesive bonding or welding or by way of overmolding by means of the material of the carrier 71.

[0046] In the mounted state of the steering shaft 10, the coupling section 72 is inserted into the opening of the hollow shaft 20, as shown in FIG. 3, it being possible for the carrier 71 to be pressed with the coupling section 72 into the outer shaft in a non-positive and/or positively locking manner, until the collar 73 bears in the longitudinal direction against the end face 23 of the outer shaft 20 (see FIG. 4). Here, the transmission bodies 8 which are held in the receptacles 74 are arranged between the grooves 22 and 32, and are oriented with their longitudinal axis Z parallel to the longitudinal axis L. Here, they are positioned in a loose positively locking connection in such a way that they have play S with respect to the grooves 22 and 32, in other words are spaced apart from the rolling body raceways which receive the balls 40 without play.

[0047] The illustrations of FIGS. 6 to 9 show a further embodiment of a securing element 8 according to the invention. Like the first embodiment according to FIGS. 1 to 5, it has a coupling section 72 which is preferably configured as a plastic injection molded part, and likewise has four receptacles 74 which are distributed over the circumference and in which in each case one cylindrical transmission body 8 is fastened, for example is snapped in a positively locking manner.

[0048] One difference from the first embodiment is that the securing element 70 does not have a collar 73, and, as a result, the coupling section 72 in this design is identical to the carrier 71. Otherwise, the arrangement, the function and the action of the coupling section 72 which is fixed on the outer shaft 20 and of the transmission bodies 8 are in principle identical.

[0049] It can be seen clearly in the longitudinal section of FIG. 6 that the coupling section 72 of the securing element 70 is arranged, like the ball cage 50, in the radial intermediate space between the inner shaft 30 and the outer shaft 20. Whereas the balls 40 bear against the grooves 22 and 32 such that they can roll without play, the transmission bodies 8 which are fixed via the securing element 70 on the outer shaft 20 have play S with respect to the grooves 22 and 32, as can be seen clearly in the enlarged longitudinal section of FIG. 7 and the enlarged cross section of FIG. 9. The arrangement and the dimensions of the transmission bodies 8 and the configuration and arrangement of the ball cage 50 in the case of the second embodiment according to FIGS. 6 to 9 are in principle comparable with those of the first embodiment which is shown in FIGS. 1 to 5.

[0050] For fixing in the opening of the outer shaft 20, the coupling section 72 has fastening elements 75 which can be configured as holding projections, for example as shown in FIG. 9, which fix the coupling section 72 on the inner side of the outer shaft 20 in a non-positive and/or positively locking and/or integrally joined manner. The fastening elements 75 can likewise be formed in one piece on the carrier 71 in the plastic injection molding operation. As a result, the transmission bodies 8 can be fixed in a positionally precise manner, with the result that they have play S with respect to the grooves 22 and 32, as can be seen clearly in FIGS. 9 and 7.

[0051] In the longitudinal direction, the securing element 70 is fixed in the outer shaft 20 by way of a projection 24 which projects into the opening cross section into the intermediate space between the inner shaft 30 and the outer shaft 20, for example by way of one or more calked portions or the like which are made in the end face 23. By virtue of the fact that the securing element 70 is fixed in the outer shaft 20 in the longitudinal direction, it forms a longitudinal stop for the ball cage 50 which is therefore likewise secured against being pulled out of the outer shaft 20.

[0052] In its end region, the inner shaft 30 has a stop element 33 which projects to the outside into the intermediate space toward the outer shaft 20 and, in the case of the inner shaft 30 being pulled out, comes into contact with the ball cage 50 or a rolling body 40 which is guided in the ball cage 50, the ball cage 50 coming into contact with the securing element 70 and therefore serving as a pull-out securing means. As a result of said described pull-out securing means, a force flow is provided in the direction of the longitudinal axis L from the inner shaft 30 to the outer shaft via the stop elements 33, the ball cage 50, the securing element 70 and the projection 24. The securing element 70 therefore limits the telescoping capability of the inner shaft 30 with respect to the outer shaft 20.

[0053] In normal operation, the balls 40 serve as torque transmission elements. The transmission bodies 8 which are positioned in the loose positively locking connection by way of the carrier 71 are not in contact with the faces of the grooves 22 and 32, and therefore also do not cause any undesired friction or wear. In the case of the failure of the balls 40, the transmission bodies 8 pass in the circumferential direction into a real positively locking connection between the grooves 22 and 32, with the result that they then ensure the transmission of torque. It is one advantage of the fixing according to the invention of the transmission bodies 8 on the outer shaft 20 that, even if the ball cage 50 is deformed or damaged by way of overloading, the securing of the transmission bodies 8 in the coupling section 72 is not impaired, and a redundant transmission of torque is ensured.

LIST OF DESIGNATIONS

[0054] 10 Steering shaft [0055] 20 Outer shaft [0056] 21 Fork [0057] 22 Groove (rolling body raceway) [0058] 23 End face [0059] 24 Projection [0060] 30 Inner shaft [0061] 31 Fork [0062] 32 Groove (rolling body raceway) [0063] 33 Stop elements [0064] 40 Ball [0065] 50 Ball cage [0066] 70 Securing element [0067] 71 Carrier [0068] 72 Coupling section [0069] 73 Collar [0070] 74 Receptacle [0071] 75 Fastening element [0072] 8 Transmission body [0073] L Longitudinal axis [0074] Z Longitudinal axis [0075] S Play