Abstract
The invention relates to a steering shaft (1) for a vehicle, and to a method for producing a steering shaft of this type. The steering shaft (1) comprises a tubular shaft body (10) which extends along the longitudinal axis (L) and has a first shaft end (11) and a second shaft end (12), a bending section (13) being arranged between the first shaft end (11) and the second shaft end (12), the bending section (13) having a plurality of grooves (21, 22, 23, 24) which run in the circumferential direction of the shaft body (10) for the formation of a groove structure, characterized in that the groove structure is of non-uniform configuration in the direction of the longitudinal axis (L).
Claims
1. A steering shaft (1) for a vehicle, comprising a tubular shaft body (10) which extends along a longitudinal axis (L) and has a first shaft end (11) and a second shaft end (12), a bending section (13) being arranged between the first shaft end (11) and the second shaft end (12), the bending section (13) having a plurality of grooves (21, 22, 23, 24) which run in the circumferential direction of the shaft body (10) for the formation of a groove structure, characterized in that the groove structure is of non-uniform configuration in the direction of the longitudinal axis (L).
2. The steering shaft as claimed in claim 1, characterized in that the geometry of a first groove (21) differs from the geometry of a second groove (22).
3. The steering shaft as claimed in either of the preceding claims, characterized in that a first groove (21) is at a first spacing (a1) from a second groove (22), the second groove (22) being at a second spacing (a2) from a third groove (23), the first spacing (a1) differing from the second spacing (a2).
4. The steering shaft as claimed in one of the preceding claims, characterized in that a depth of the grooves (21, 22, 23, 24), a width of the grooves (21, 22, 23, 24) and/or the spacing of two grooves (21, 22, 23, 24) increases or decreases from a side of the bending section (13), which side faces the first shaft end (11), toward a side of the bending section (13), which side faces the second shaft end (12).
5. The steering shaft as claimed in one of the preceding claims, characterized in that the wall thickness of the shaft body (10) in a groove region of a first groove (21) and that in a groove region of a second groove (22) differ from one another.
6. The steering shaft as claimed in one of the preceding claims, characterized in that at least one groove (21, 22, 23, 24) is configured so as to be recessed inward in an outer circumferential face (14) of the shaft body (10).
7. The steering shaft as claimed in one of the preceding claims, characterized in that the bending section (13) has at least three grooves (21, 22, 23, 24) which are in each case of different depth and/or are at a different spacing from one another in each case.
8. The steering shaft as claimed in one of the preceding claims, characterized in that the depth of a groove (21, 22, 23, 24) is between 0.1 and 3 times a wall thickness of the shaft body (10) outside the bending section (13).
9. The steering shaft as claimed in one of the preceding claims, characterized in that the tubular shaft body (10) has an enveloping circle diameter (D) and a wall thickness (s) outside the bending section (13), an enveloping circle diameter (HK) of the bending section (13) being smaller than or equal to the sum of the enveloping circle diameter (D) of the tubular shaft body (10) and twice the wall thickness (s) of the tubular shaft body (10).
10. A method for producing a steering shaft for a vehicle, comprising the following steps: providing of a tube which extends along a longitudinal axis (L) with an enveloping circle diameter (D) and a wall thickness (s); forming of the tube in order to configure a tubular shaft body (10) of a steering shaft (1) with a bending section (13) which is arranged between a first shaft end (11) and a second shaft end (12) of the shaft body (10), at least one groove (21, 22, 23, 24) which runs in the circumferential direction of the shaft body (10) being formed into a circumferential face (14) of the tube by way of rolling of at least one roller (30, 31, 32, 33, 34), characterized in that the enveloping circle diameter (HK) of the bending section (13) is smaller than or equal to the sum of the enveloping circle diameter (D) of the tube and twice the wall thickness (s).
11. The method as claimed in claim 10, characterized in that the bending section (13) has a plurality of grooves (21, 22, 23, 24) which run in the circumferential direction of the shaft body (10) for the formation of a groove structure, the groove structure being of non-uniform configuration in the direction of the longitudinal axis (L).
12. The method as claimed in claim 10 or 11, characterized in that the grooves (21, 22, 23, 24) are formed by way of a roller (30), at least one first groove (21) being formed in a first longitudinal position of the roller (30), and one second groove (22) being formed in a second longitudinal position of the roller (30), which second longitudinal position is spaced apart axially from said first longitudinal position, the roller (30) being advanced to a different extent onto the circumferential face (14) of the tube in the first and second longitudinal position, and/or the longitudinal positions of the roller (30) being spaced apart from one another to a different extent.
13. The method as claimed in claim 12, characterized in that the grooves (21, 22, 23, 24) are formed by way of at least two rollers (31, 32, 33, 34) which are spaced apart axially from one another, are arranged, in particular, along a common rolling axis (R), and have a different roller geometry, and/or different spacings (a1, a2) between a first roller (31) and a second roller (32) and between the second roller (32) and a third roller (33).
14. The method as claimed in one of claims 10 to 13, characterized in that the length of the tube is identical before and after the forming.
15. The method as claimed in one of claims 10 to 14, characterized in that the steering shaft is configured as claimed in one of claims 1 to 9.
Description
[0054] Exemplary embodiments of the invention will be described in greater detail in the following text on the basis of the drawings, in which:
[0055] FIG. 1A shows a schematic illustration of a first embodiment of a steering shaft according to the invention with grooves of different geometry for the provision of a non-uniform groove structure, in a half section view,
[0056] FIG. 1B shows a schematic illustration of the embodiment according to FIG. 1A with illustrated external diameters of the respective groove regions,
[0057] FIG. 2 shows a schematic illustration of a second embodiment of a steering shaft according to the invention with grooves which are spaced apart from one another to a different extent for the provision of a non-uniform groove structure, in a half section view,
[0058] FIG. 3 shows a schematic illustration of a third embodiment of a steering shaft according to the invention with three grooves which are spaced apart from one another to a different extent for the provision of an non-uniform groove structure, in a half section view,
[0059] FIG. 4 shows a schematic illustration of a first embodiment of the production method according to the invention for a steering shaft with a roller which can be advanced, in a half section view,
[0060] FIG. 5 shows a schematic illustration of a second embodiment of the production method according to the invention for a steering shaft with a plurality of rollers, in a half section view,
[0061] FIG. 6 shows a schematic illustration of a steering arrangement with a steering shaft according to the invention, in a perspective view,
[0062] FIG. 7 shows a schematic illustration of a fourth embodiment of a steering shaft according to the invention, in a half section view,
[0063] FIG. 8 shows a schematic illustration of a steering shaft according to the invention in the unbent state during normal operation, and
[0064] FIG. 9 shows a schematic illustration of the steering shaft according to FIG. 8 in the bent state after a crash.
[0065] In the following description of the invention, the same designations are used for identical and identically acting elements.
[0066] FIGS. 1A and 1B show one embodiment of a steering shaft 1 according to the invention with a shaft body 10 which has a first shaft end 11 and a second shaft end 12 which are provided for articulated coupling to a steering gear and a steering wheel of a vehicle. The tubular shaft body 10 is configured as a hollow shaft with a longitudinal axis L, an internal diameter d, an external diameter D which can also be called the enveloping circle diameter of the tubular shaft body 10 outside the bending section 13, and an interior cavity 15. The enveloping circle diameter is the diameter of the enveloping circle, by which the cross section of the shaft body 10, which cross section is oriented orthogonally with respect to the longitudinal axis, is circumscribed. Furthermore, the shaft body 10 has a wall thickness s which corresponds to half the difference of the external diameter and the internal diameter. Four grooves 21, 22, 23, 24 are formed into the outer circumferential face 14 of the shaft body 10 at identical spacings a1, a2, a3 from one another in a bending section 13 of the shaft body 10. The bending section 13 comprises four grooves 21, 22, 23, 24 which in each case have a different geometry, with the result that a non-uniform groove structure according to the invention is configured in the direction of the longitudinal axis L. The bending section 13 is delimited by way of the outer edges 211, 241 of the outer grooves 21, 24. The enveloping circle diameter HK of the bending section 13 is that diameter of the enveloping circle which circumscribes the maximum cross section of the bending section 13, which maximum cross section is oriented orthogonally with respect to the longitudinal axis. In other words, the enveloping circle diameter HK of the bending section 13 is the maximum external diameter in the bending section 13. The grooves 21, 22, 23, 24 are configured as annular grooves so as to run around the shaft body 10 in the circumferential direction, and configure depressions of circular segment-shaped cross section with respect to the circumferential face 14. The depth T of the axially adjacent grooves decreases from the first groove 21 on a side which faces the steering gear (on the left in the figures) as far as a side which faces the steering wheel (on the right in the figures) as far as the fourth groove 24. Accordingly, the external diameters D1, D2, D3, D4 which are illustrated in FIG. 1B of the associated grooves 21, 22, 23, 24 increase from left to right (D1<D2<D3<D4). The internal diameters d1, d2, d3, d4 of the associated grooves 21, 22, 23, 24 likewise increase from left to right (d1<d2<d3<d4). The wall thicknesses, for example defined by way of half the difference between the respective external diameter D1, D2, D3, D4 and the internal diameter d1, d2, d3, d4, that is to say, for example, (D1−d1)/2, in the respective groove regions increase from left to right. The diameters are determined in each case along a center line of the groove, that is to say in the center of the axial groove region or at the deepest point of the groove. The shaft body 10 curves inward into the interior cavity 15 in the bending section 13 in the groove regions. The external diameters D1, D2, D3, D4 in the groove regions are smaller than the external diameter D of the shaft body 10, and the internal diameters d1, d2, d3, d4 are smaller is the internal diameter d of the shaft body 10. The tubular shaft body 10 therefore has an enveloping circle diameter D and a wall thickness s outside the bending section 13, the enveloping circle diameter HK of the bending section 13 being smaller than the sum of the enveloping circle diameter D of the tubular shaft body 10 and twice the wall thickness (2s) of the tubular shaft body 10. In the shaft side sections to the side of, that is to say outside, the bending section 13, the shaft body 10 has substantially constant cross section, or a constant external diameter D and internal diameter d. The diameters and wall thicknesses of the shaft body 10 can also vary in the longitudinal direction L outside the region 13, however, for example for the provision of a coupling section for coupling the shaft body 10 to a fork of a universal joint.
[0067] FIG. 2 shows a second embodiment of a steering shaft 1 according to the invention which differs from the steering shaft 1 which is shown in FIGS. 1A and 1B in that the spacings a1, a2, a3 between in each case two adjacent grooves 21, 22, 23 and 24 are different, as a result of which an non-uniform groove structure according to the invention is provided in the direction of the longitudinal axis L. The spacings a1, a2, a3 shorten from left to right. The first spacing a1 between the first groove 21 and the second groove 22 is greater than the second spacing a2 between the second groove 22 and the third groove 23, which second spacing a2 is in turn greater than the third spacing a3 between the third groove 23 and the fourth groove 24.
[0068] FIG. 3 shows a third embodiment of a steering shaft according to the invention which corresponds to that in FIG. 2, the bending section 13 comprising only three grooves 21, 22, 23 with spacings a1 and a2 which are different than one another for the formation of an non-uniform groove structure.
[0069] The steering shafts 1 which are shown in FIGS. 1A to 3 have bending sections 13 with an non-uniform groove structure, which bending sections 13 bring about a defined bending behavior of the steering shaft 1 if, in the installed state, the latter is deformed by way of the forces which act in the case of a vehicle crash. Via the non-uniform groove structure such as the number, the geometry (depth T, width B) of the grooves and/or the spacings of the grooves from one another, the section modulus of the shaft body 10 with respect to deformation can be set locally, as a result of which the bending behavior of the overall steering shaft 1 can be influenced in accordance with a desired shape in the case of a vehicle crash (see FIGS. 8 and 9).
[0070] FIGS. 4 and 5 illustrate two alternative embodiments of a production method according to the invention for a steering shaft 1, comprising the following steps: [0071] providing of a tube which extends along a longitudinal axis L with an enveloping circle diameter D and a wall thickness s; [0072] forming of the tube for the configuration of a tubular shaft body 10 of a steering shaft 1 with a bending section 13 which is arranged between a first shaft end 11 and a second shaft end 12 of the shaft body 10,
[0073] at least one groove 21, 22, 23, 24 which runs in the circumferential direction of the shaft body 10 being formed into a circumferential face 14 of the tube by way of rolling of at least one roller 30, 31, 32, 33, 34. According to the invention, the enveloping circle diameter HK of the bending section 13 is smaller than or equal to the sum of the enveloping circle diameter D of the tube and twice the wall thickness.
[0074] As in the design variants of FIGS. 4 and 5, this can have a bending section 13 with four grooves 21, 22, 23, 24 of different geometry, in particular of different depth T and width B, in order to achieve a defined bending behavior. In the case of the methods which are shown, at least one roller 30 which is mounted such that it can be rotated about a rolling axis R (see FIG. 4) or rollers 31, 32, 33, 34 (see FIG. 5) is/are advanced in the radial direction (see radial double arrow) toward the circumferential face 14 of a tube which forms the shaft body 10, in order to exert a forming force on the tube. In this design variant, the rolling axis R and the longitudinal axis L are oriented substantially parallel to one another. The rollers 30, 31, 32, 33, 34 and the shaft body 10 rotate counter to one another (see arrows for rotational directions), preferably rolling on one another or turning on one another.
[0075] In the case of the production method which is illustrated in FIG. 4, a single roller 30 is provided which can be displaced axially in the longitudinal direction L (see axial double arrow), in order to form in each case one of the grooves 21, 22, 23, 24 in the tube at various longitudinal positions. Accordingly, the grooves 21, 22, 23, 24 are formed one after another. The tube might also be displaced or moved relative to the roller 30 (to the left in FIG. 4). Therefore, the bending section 13 has a plurality of grooves 21, 22, 23, 24 which run in the circumferential direction of the shaft body 10 for the formation of a groove structure, the groove structure being of non-uniform configuration in the direction of the longitudinal axis L.
[0076] In the case of the production method which is illustrated in FIG. 5, four rollers 31, 32, 33, 34 which are mounted such that they can be rotated about a common rolling axis are provided, all of the grooves 21, 22, 23, 24 being formed at the same time. The spacings of the rollers 31, 32, 33, 34 from one another can be variable, in order to produce different spacings a1, a2, a3 of the grooves 21, 22, 23, 24 from one another. Therefore, the bending section 13 has a plurality of grooves 21, 22, 23, 24 which run in the circumferential direction of the shaft body 10 for the formation of a groove structure, the groove structure being of non-uniform configuration in the direction of the longitudinal axis L.
[0077] The methods according to the invention have the advantage that a steering shaft 1 with a bending section 13 can be produced simply and has merely a small installation space requirement.
[0078] FIG. 6 shows a steering arrangement 100 which is known per se and comprises a steering shaft 1 according to the invention with a bending section 13, the bending section 13 having a plurality of grooves 21, 22, 23, 24 which run in the circumferential direction of the shaft body 10 for the formation of a groove structure, the groove structure being of non-uniform configuration in the direction of the longitudinal axis L. The steering shaft 1 is coupled to a joint 5 which faces a steering gear and to a joint 6 which faces a steering wheel. The steering wheel 1 protrudes through a bulkhead leadthrough 4 in a bulkhead 2.
[0079] The bulkhead leadthrough 4 is sealed by way of a sealing cuff 3 against spray water. The steering shaft is mounted rotatably in a steering column 600 between the joint 6 and the steering wheel (not shown), the steering column being configured as a manually adjustable steering column 600. As an alternative, other types of steering columns can also be used, such as rigid steering columns or electrically adjustable steering columns.
[0080] FIG. 7 shows one embodiment of a steering shaft 1 according to the invention with a sliding shaft section 16 which has positively locking elements 17 which are oriented in the longitudinal direction. An inner shaft 111 can be pushed into the sliding shaft section 16, said inner shaft 111 having complementary positively locking elements which can be brought into engagement with the positively locking elements 17 for the transmission of a torque. The inner shaft 111 and the shaft body 10 can be configured such that they can be telescoped with respect to one another.
[0081] FIG. 8 shows one embodiment of a steering shaft 1 according to the invention in the non-deformed (unbent) state during normal operation with a non-uniform groove structure before the occurrence of a crash. FIG. 9 shows the steering shaft 1 from FIG. 8 in the deformed (bent) state after the occurrence of a crash. The steering shaft 1 is bent, in particular, in the bending section 13, whereas the shaft side sections 18a and 18b which are arranged on both sides thereof are not bent or are bent merely slightly. As a result of the non-uniform groove structure according to the invention (see FIGS. 1 to 5), the bending section 13 overall is less flexurally stiff than the two shaft side sections 18a, 18b, a defined bending behavior (bending characteristic curve) and/or a resulting bending deformation and/or compression of the steering shaft 1 being specified structurally. The bending behavior can be predetermined by way of the non-uniform groove structure, for example by way of a suitable selection of the geometry and/or the spacings a1, a2, a3 of the grooves 21, 22, 23, 24, in such a way that, in the case of a vehicle crash, the steering shaft 1 does not penetrate into the passenger compartment of the vehicle 1. As a result, the risk of injury for the driver is reduced.
