Abstract
A method for producing a profiled hollow shaft for a telescopic steering shaft of a motor vehicle may involve providing a hollow shaft to be processed, a profile mandrel, and a roller head comprising at least one roller. The method may further involve introducing the profile mandrel into the hollow shaft in order to produce a groove in the hollow shaft. The method may also involve moving the profile mandrel and the hollow shaft together relative to the roller head, wherein movement of the profile mandrel and the hollow shaft relative to the roller head is performed exclusively in a direction of a longitudinal axis of the hollow shaft in order to form a groove.
Claims
1.-11. (canceled)
12. A method for producing a profiled hollow shaft for a telescopic steering shaft of a motor vehicle, the method comprising: providing a hollow shaft to be processed, a profile mandrel, and a roller head comprising at least one roller; introducing the profile mandrel into the hollow shaft for purposes of producing a groove in the hollow shaft; and moving the hollow shaft relative to the roller head exclusively in a direction of a longitudinal axis of the hollow shaft to form the groove in the hollow shaft.
13. The method of claim 12 comprising moving the profile mandrel together with the hollow shaft, wherein movement of the profile mandrel and the hollow shaft relative to the roller head occurs exclusively in the direction of the longitudinal axis of the hollow shaft.
14. The method of claim 12 wherein the groove with a groove length on the hollow shaft is created by a continuous advancing movement of the hollow shaft relative to the roller head along the groove length, wherein the at least one roller of the roller head rolls along the hollow shaft in the longitudinal direction.
15. The method of claim 12 further comprising retracting the hollow shaft relative to the roller head.
16. The method of claim 12 wherein the groove is one of a plurality of grooves that are created on the hollow shaft by a common work step involving a continuous advancing movement.
17. A method for producing a telescopic steering shaft for a motor vehicle, the method comprising: introducing an inner hollow shaft with a groove profile into an outer hollow shaft with a groove profile; and calibrating the groove profile of the outer hollow shaft to the groove profile of the inner hollow shaft by way of at least one roller in a continuous advancing movement along a longitudinal axis of a steering shaft.
18. The method of claim 17 further comprising placing a plastic sleeve on the inner hollow shaft prior to introducing the inner hollow shaft into the outer hollow shaft, wherein after introducing the inner hollow shaft into the outer hollow shaft the plastic sleeve is positioned between the inner hollow shaft and the outer hollow shaft, wherein the inner hollow shaft, the plastic sleeve, and the outer hollow shaft are calibrated relative to one another.
19. A steering shaft for a motor vehicle comprising: an inner shaft with a profile of grooves; and an outer shaft with a profile of grooves that corresponds to the profile of grooves of the inner shaft, wherein the inner and outer shafts are positioned coaxially and are telescopic to one another, wherein the outer shaft is disposed about the inner shaft and the groove profile of the outer shaft is calibrated to the groove profile of the inner shaft by way of a continuous advancing movement of at least one roller along a longitudinal axis of the steering shaft.
20. The steering shaft of claim 19 wherein a flank angle of the profile of grooves in the outer shaft and/or the inner shaft and a flank angle of a profile top of an internal toothing of the outer shaft and/or the inner shaft amounts to 45° to 75°.
21. The steering shaft of claim 19 wherein a ratio of a difference of an inner diameter of a profile top of an external toothing and an inner diameter of a groove bottom of an internal toothing of the inner shaft and/or the outer shaft to a material thickness of the inner shaft and/or the outer shaft is between 1 and 4.
22. The steering shaft of claim 19 wherein a sleeve with a profile is disposed between the inner shaft and the outer shaft, the sleeve corresponding to the profile of grooves of the outer shaft and the profile of grooves of the inner shaft.
Description
BRIEF DESCRIPTION OF THE FIGURES
[0046] Other preferred embodiments and aspects of the present invention shall be explained more closely by the following description of the figures. There are shown:
[0047] FIG. 1 schematically, a perspective view of a steering shaft;
[0048] FIG. 2 schematically, a portion of an outer shaft and a portion of an inner shaft of the previous figure;
[0049] FIG. 3 schematically, a cross sectional view of the steering shaft of the previous figures;
[0050] FIG. 4 schematically, a detail view of the cross sectional view shown in FIG. 3;
[0051] FIG. 5 schematically, a cross sectional view of an outer shaft;
[0052] FIG. 6 schematically, a cross sectional view of an inner shaft;
[0053] FIG. 7 schematically, a cross sectional view of a sleeve;
[0054] FIG. 8 schematically, a perspective view of a roller head;
[0055] FIG. 9 schematically, a top view of the roller head of the previous figure;
[0056] FIG. 10 schematically, a detail view of the top view of the roller head shown in FIG. 9;
[0057] FIG. 11 schematically, a sectional view of the detail view of the roller head of the previous figure;
[0058] FIG. 12 schematically, a sectional view through the roller head of the previous figures, where the sectioning cut runs along the longitudinal axis of a profile mandrel;
[0059] FIG. 13 schematically, a sectional view of the roller head of the previous figures, where a hollow shaft is located in the roller head;
[0060] FIG. 14 schematically, a sectional view of the roller head of the previous figures, where a hollow shaft is located in the roller head; and
[0061] FIG. 15 schematically, a sectional view of a hollow shaft, making contact with a roller of the roller head.
DETAILED DESCRIPTION OF PREFERRED SAMPLE EMBODIMENTS
[0062] In the following, preferred sample embodiments shall be described with the aid of the figures. The same, similar, or equivalent elements shall be designated with identical reference numbers. To avoid redundancy, no repeat description of these elements will be provided at places in the following description.
[0063] FIG. 1 shows a steering shaft 10 for a motor vehicle. The steering shaft 10 comprises an outer shaft 20 and an inner shaft 30, which are telescopic in regard to each other. At an outer end, the outer shaft 20 comprises a fork 21, representing a portion of a universal joint, not shown, in order to integrate the steering shaft 10 into a steering train. Also the inner shaft 30 comprises at an outer end a fork 31, representing a portion of a universal joint, not shown, in order to integrate the steering shaft 10 into the steering train.
[0064] The outer shaft 20 and the inner shaft 30 are hollow shafts, made of a steel with good forming properties. Alternatively, the outer shaft 20 and the inner shaft 30 can also be made from aluminum alloys, refined steel, or the like.
[0065] FIGS. 1 and 2 show that the outer shaft 20 is profiled in the region serving to accommodate the inner shaft 30. Accordingly, the outer shaft 20 comprises grooves 22 in this region, running in the axial direction of the outer shaft 20. The grooves 22 with a groove length l on the outer circumferential surface 27 of the outer shaft 20 form an internal toothing on the inner circumferential surface 28 of the outer shaft 20. FIG. 2 shows that an end segment of the inner shaft 30, which in an operating state is inserted into the outer shaft 20, comprises an external toothing which corresponds to the internal toothing of the outer shaft 20. The external toothing of the inner shaft 30 is formed by grooves 32 on an outer circumferential surface 37 of the inner shaft 30. On the external toothing of the inner shaft 30 there is arranged a sleeve 40, corresponding both to the external toothing of the inner shaft 30 and the internal toothing of the outer shaft 20. The sleeve 40 is press-fitted onto the inner shaft 30, so that the sleeve 40 can move together with the inner shaft 30 relative to the outer shaft 20 inside it. In one embodiment not represented, the sleeve 40 is axially fixed to the inner shaft 30 by a caulking. In order to comply with the stiffness requirements of the steering shaft 10, a very slight play exists between the inner shaft 30 or the sleeve 40 and the outer shaft 20, so that it can almost be called play-free. Instead, a sliding fit is provided between the inner shaft 30 or the sleeve 40 and the outer shaft 20, allowing an adjustment of the length of the steering shaft 10 to a very low and constant force level.
[0066] FIGS. 3 and 4 are cross sectional views through the steering shaft 10. One can see that the profile of the outer shaft 20 corresponds to the profile of the sleeve 40 or the inner shaft 30. Thus, for example, the groove 22 of the outer shaft 20 matches up with the groove 42 of the sleeve 40 or the groove 32 of the inner shaft 30. The flanks 26, 46, 36 respectively adjoining the grooves 22, 42, 32 extend, as shown in FIGS. 5 and 6, from the groove bottom in each case at the same angle. Therefore, as shown in FIG. 4, the flanks 26, 36, 46 of the outer shaft, the sleeve and the inner shaft extend almost parallel to each other and the flow of force between the inner shaft 30 and the outer shaft 20 occurs only via the flanks 26, 36, 46. In the region outside of the flanks 26, 36, 46 there is no force-transmitting contact between the inner shaft 30, the sleeve 40 and the outer shaft 20.
[0067] Furthermore, FIGS. 3 and 4 show that a profile top 44 of the sleeve 40 borders on an inner circumferential surface of the profile top 24 of the outer shaft 20. In turn, a profile top 34 of the inner shaft 30 borders on the inner circumferential surface of the profile top 44.
[0068] Thanks to the mutually corresponding profiles of the outer shaft 20, the sleeve 40 and the inner shaft 30, the outer shaft 20 engages indirectly with the inner shaft 30 via the sleeve 40. Thus, it is possible to provide a transmittal of torque between the outer shaft 20 and the inner shaft 30.
[0069] FIGS. 5, 6 and 7 show separately the profile cross sections of the outer shaft 20, the inner shaft 30 and the sleeve 40. FIGS. 5 and 6 show an inner diameter of the profile top D1, an inner diameter of the groove D2 and a flank angle α. In order to provide a minimum degree of torsional stiffness, the ratio of the difference of the inner diameter of the profile top D1 and the inner diameter of the groove D2 to a material thickness b should be between 1 and 4, preferably between 1.5 and 3.5 and especially preferably between 2 and 3.
[0070] FIGS. 8 and 9 show a roller head 50 for the production of the above-described outer shaft. The roller head for production of the above-described inner shaft has a similar construction to the roller head 50 for the production of the outer shaft. The roller head 50 comprises eight rollers 52, which are arranged in the form of a star about a rolling axis. The rollers 52 are arranged relative to each other at an angle of 45°. Each roller 52 is mounted by two bearing cheeks 56. The two bearing cheeks 56 of a roller 52 are joined together by a roller bearing foot 58. The roller bearing foot 58 comprises bores 59 for fastening on a frame of the roller head 50.
[0071] FIGS. 8 and 9 show a profile mandrel 60, which is arranged in the middle of the eight rollers 52. Between the profile mandrel 60 and the rollers 52 there is provided a gap, so that the profile mandrel 60 can be moved along the rolling axis without the rollers 52 rolling against the profile mandrel 60.
[0072] Alternatively, the roller head can also comprise one, two, three, four, five, six, seven, nine, ten, eleven, twelve or more rollers 52, arranged spaced apart around the periphery with a corresponding angle to each other.
[0073] FIG. 10 is an enlarged view of the profile mandrel 60, there being provided a gap between the profile mandrel 60 and the rollers 52 corresponding to the profile of a shaft being produced by means of the roller head 50.
[0074] FIGS. 10 and 11 show that the rollers 52 are profiled and comprise a roller center profile 53 and a roller edge profile 54. The diameter of the roller center profile 53 here is greater than the diameter of the roller edge profile 54. The rollers 52 and the profile mandrel 60 are arranged with respect to each other such that a roller center profile 53 corresponds to a groove 62 of the profile mandrel 60. Moreover, the roller edge profiles 54 correspond to the profile tops 64 of the profile mandrel 60.
[0075] FIG. 11 shows a cross section of a detailed view of a roller head 50, the rollers 52 being in contact with an outer shaft 20, which has been shoved onto the profile mandrel 60. The outer shaft 20 here is being cold rolled, so that the outer shaft 20 receives on its inner circumferential surface the profile of the profile mandrel 60 and is formed on its outer circumferential surface by the rollers 52 and especially the roller profile.
[0076] Since the roller center profile 53 corresponds to the groove 52 of the profile mandrel, the material of the outer shaft 20 is pressed by the roller center profile 53 into the groove 62 of the profile mandrel 60. The roller edge profiles 54 roll along the profile tops 24 of the outer shaft 20, enabling a more intensive force application of the rollers 52 against the outer shaft 20 and a better formation of the internal toothing of the outer shaft 20. Alternatively, the inner shaft of a steering shaft can also be fabricated by means of a roller head so described.
[0077] FIGS. 12 to 14 show the movements of a double travel movement for the profiling of the outer shaft 20. These are cross sectional views, each time showing two oppositely situated rollers 52, with a profile mandrel 60 arranged between the rollers 52, onto which an outer shaft 20 has been shoved.
[0078] FIG. 12 shows an advancing movement of the profile mandrel 60. The profile mandrel 60 is moved relative to the rollers 52. No contact exists between the profile mandrel 60 and the rollers 52, so that the rollers 52 remain in a position of rest. The outer shaft 20 shoved onto the profile mandrel 60 is not yet in contact with the rollers 52 in FIG. 12.
[0079] FIG. 13 shows the profile mandrel 60 together with the outer shaft 20 still in the advancing movement, with the difference that now the outer shaft 20 makes contact with the rollers 52. The gap between the profile mandrel 60 and the rollers 52 is now filled up by the outer shaft 20. Thanks to the advancing movement of the profile mandrel 60 together with the outer shaft 20, the rollers 52 are placed in rotation. They roll along the outer circumferential surface of the outer shaft 20, so that the outer shaft 20 is given the above-described profiling, as the rollers 52 in the roller center profile 53 have a shorter distance from the profile mandrel 60 than the as yet unformed outer shaft 20.
[0080] Once the desired length of the profiling and the associated groove length l of the outer shaft 20 has been reached, the return travel movement indicated in FIG. 14 commences. The profile mandrel 60 and the outer shaft 20 move jointly in the opposite direction in relation to the advancing movement. Contact continues to exist between the outer shaft 20 and the rollers 52, so that the rollers 52 also rotate in the opposite direction during the return travel movement. The return travel movement can be maintained until the outer shaft 20 and the profile mandrel 60 have left the roller head 50. Alternatively, a new advancing movement can follow the return travel movement, for example in order to improve the quality of the profiling of the outer shaft. In order to improve the rolling of the rollers against the shaft being profiled and minimize the pitting in the contact surfaces, it is conceivable and possible to wet the rollers or the shaft with a lubricant on the corresponding contact surface.
[0081] FIG. 15 shows a sectional view of the outer shaft 20 and a roller 52, where the outer shaft 20 is at a reversal point from advancing movement to return travel movement relative to the roller 52. The grooves 22 here have the groove length l. In the example, the roller 52 is rolled along the groove length l continuously from the free end of the shaft 20 to the end of the groove 22. After this, the roller 52 is rolled back continuously from the reversal point at the end of the groove length l. In this way, the complex tube geometry is produced with a very simple rolling process.
[0082] Insofar as is applicable, all individual features which are represented in the individual sample embodiments can be combined with and/or exchanged for each other, without leaving the scope of the invention.
LIST OF REFERENCE NUMBERS
[0083] 10 Steering shaft [0084] 20 Outer shaft [0085] 21 Fork [0086] 22 Groove [0087] 24 Profile top [0088] 26 Flank [0089] 27 Outer circumferential surface [0090] 28 Inner circumferential surface [0091] 30 Inner shaft [0092] 31 Fork [0093] 32 Groove [0094] 34 Profile top [0095] 36 Flank [0096] 37 Outer circumferential surface [0097] 40 Sleeve [0098] 42 Groove [0099] 44 Profile top [0100] 46 Flank [0101] 50 Roller head [0102] 52 Roller [0103] 53 Roller center profile [0104] 54 Roller edge profile [0105] 56 Roller bearing cheek [0106] 58 Roller bearing foot [0107] 60 Profile mandrel [0108] 62 Groove [0109] 64 Profile top [0110] 66 Flank [0111] D1 Inner diameter of a profile top [0112] D2 Inner diameter of a groove bottom [0113] b Material thickness [0114] a Flank angle [0115] l Groove length
