Fixed Bearing, Steering Gear, and Steering System

Abstract

A fixed bearing for a steering gear includes a rotational bearing that has an inner bearing ring configured to receive a pinion shaft of the steering gear and an outer bearing ring that is received in a bearing sleeve. The fixed bearing also includes a pivot ring that has an outer ring and an inner ring that are pivotally connected via one or more torsion webs. The inner ring is connected to the bearing sleeve. The outer ring is disposed in a housing of the steering gear and configured to support the fixed bearing. The inner ring and the outer bearing ring are clamped between an axial stop of the bearing sleeve and a clamping ring. Such clamping reduces backlash and prevents undesired noises due to motion of these elements within the bearing sleeve during the operation of the steering gear with the fixed bearing.

Claims

1. A fixed bearing for a steering gear, having comprising: a rotary bearing that includes an inner bearing ring configured to receive a pinion shaft of the steering gear and an outer bearing ring configured to be received in a bearing sleeve; and a pivot ring having an outer ring and an inner ring, the outer and inner rings pivotably connected by at least one torsion webs, wherein the inner ring is connected to the bearing sleeve and the outer ring is configured to mount the fixed bearing in a housing of the steering gear, and wherein the inner ring and the outer bearing ring of the rotary bearing are disposed so as to be braced between an axial detent of the bearing sleeve and a tension ring.

2. The fixed bearing as claimed in claim 1, wherein the axial detent is defined by an end portion of the bearing sleeve, the end portion configured by forming.

3. The fixed bearing as claimed in claim 1, wherein only the inner ring and the outer bearing ring of the rotary bearing are disposed between the axial detent of the bearing sleeve and the tension ring.

4. The fixed bearing as claimed in claim 1, wherein a pretensioning force causing the bracing is at least 8 kN.

5. The fixed bearing as claimed in claim 1, wherein the tension ring is disposed within the bearing sleeve.

6. The fixed bearing as claimed in claim 1, wherein the bearing sleeve externally defines a supporting protrusion.

7. The fixed bearing as claimed in claim 1, wherein the tension ring is welded to the bearing sleeve.

8. A method for producing a fixed bearing that includes a rotary bearing and a pivot ring, the rotary bearing including an inner bearing ring configured to receive a pinion shaft of a steering gear and an outer bearing ring configured to be received in a bearing sleeve, the pivot ring having an outer ring and an inner ring that are pivotably connected by at least one torsion web, the inner ring connected to the bearing sleeve and the outer ring configured to mount the fixed bearing in a housing of the steering gear, the method comprising: positioning the rotary bearing and the inner ring of the pivot ring within the bearing sleeve between an axial detent of the bearing sleeve and a tension ring; and generating a defined pretensioning force configured to brace the inner ring of the pivot ring and the outer bearing ring of the rotary bearing between the axial detent of the bearing sleeve and the tension ring.

9. A steering gear for a steering system of a motor vehicle, having comprising: a gear wheel; a pinion shaft that includes a helical pinion configured to mesh with the gear wheel; and a fixed bearing including: a rotary bearing with an inner bearing ring configured to receive a pinion shaft of the steering gear and an outer bearing ring configured to be received in a bearing sleeve, and a pivot ring having an outer ring and an inner ring that are pivotably connected by at least one torsion web, the inner ring connected to the bearing sleeve, the inner ring and the outer bearing ring of the rotary bearing disposed so as to be braced between an axial detent of the bearing sleeve and a tension ring, wherein the pinion shaft on one side of the helical pinion is mounted in the fixed bearing, and wherein the outer ring of the pivot ring of the fixed bearing is mounted directly or indirectly in a housing of the steering gear.

10. The steering gear as claimed in claim 9, wherein the pinion shaft is configured to be connected in a rotatably driving manner to a steering motor of a steering system.

Description

[0027] The invention will be discussed in more detail below on the basis of an exemplary embodiment illustrated in the drawings. In the drawings:

[0028] FIG. 1 shows a longitudinal section through a steering gear according to the invention;

[0029] FIG. 2 shows the fixed bearing of the steering gear according to FIG. 1 in a view from the front; and

[0030] FIG. 3 shows a longitudinal section through the fixed bearing according to FIG. 2.

[0031] FIG. 1 shows the substantial component parts of a steering gear of a steering system according to the invention. Said steering gear comprises a housing 1, a gear wheel 2 as well as a helical pinion 3 that meshes with the gear wheel 2 being rotatably disposed within said housing 1. The helical pinion 3 and a (helical) pinion shaft 4 comprising the helical pinion 3 are integrally configured in the form of a worm.

[0032] The gear wheel 2 is fixedly fastened on an output shaft 5 of the steering gear. Said output shaft 5 which in the exemplary design embodiment shown has a toothing for connecting in a rotatably fixed manner to the gear wheel 2 can mesh with a steering rod which at least in one portion is configured as a rack, for example, on account of which the rack carries out a translatory movement which in a manner known by way of a wheel control arm (not illustrated) can be converted to a pivoting movement of steering-capable wheels (not illustrated) of the motor vehicle. However, the output shaft 5 can also be a steering column of a power-assisted steering system, said steering column being connected to a steering wheel and acting on the rack by way of a steering pinion.

[0033] The helical pinion shaft 4 has a drive-side end by way of which said helical pinion shaft 4 is connectable to the output shaft (not illustrated) of a steering motor (for example an electric motor). The helical pinion shaft 4 by means of a first mounting is mounted in the housing 1 in the region of said drive-side end. Said mounting is configured as a fixed bearing 6 which permits pivoting of the helical pinion shaft 4 about a pivot axis 7 (cf. FIG. 2). This pivoting causes a deflection of the end of the helical pinion shaft 4 that is opposite the drive-side end, said helical pinion shaft 4 there being mounted in a corresponding receptacle of the housing 1 by means of a floating bearing 8. Said floating bearing 8 is configured such that said floating bearing 8 within limits permits the deflection of this end of the helical pinion shaft 4 resulting from the pivoting of the helical pinion shaft 4.

[0034] Both the fixed bearing 6 as well as the floating bearing 8 comprise in each case one rotary bearing 9, 10 in the form of a ball bearing. One portion of the helical pinion shaft 4 is in each case mounted in inner bearing rings 11 of said rotary bearings 9, 10, while outer bearing rings 12 of the rotary bearings 9, 10 are in each case mounted in one bearing device 13, 14 which in turn are received in associated receptacles of the housing 1. The bearing devices 13, 14 in terms of construction are configured such that said bearing devices 13, 14, in the case of the fixed bearing 6, enable the pivoting of the helical pinion shaft 4 about the pivot axis 7, or in the case of the floating bearing 8, enable the deflection of the free end of the helical pinion shaft 4.

[0035] To this end, the bearing device 13 of the fixed bearing 6 comprises a bearing sleeve 15 having a circular cross-section, which internally in a first longitudinal portion receives the outer bearing ring 12 of the rotary bearing 9 and in a second longitudinal portion receives an inner ring 17 of a pivot ring 16. The inner ring 17 of the pivot ring 16, inter alia on account of the effect of a disc-shaped tension ring 18, is mounted so as to be rotationally fixed and axially secured within the bearing sleeve 15, wherein the inner ring 17 is supported on the outer bearing ring 12 of the rotary bearing 9. Specifically, the inner ring 17 of the pivot ring 16, stressed on one side by the tension ring 18, is pushed against one side of the outer bearing ring 12 of the rotary bearing 9 which in turn on the other side thereof is supported on an axial detent 19 which is formed by an inwardly bent and, on account thereof, radially aligned, end portion of the bearing sleeve 15.

[0036] Apart from the inner ring 17, the pivot ring 16 also comprises an outer ring 20. The outer ring 20 is connected to the inner ring 17 by way of two torsion webs 21 (cf. FIG. 2). The outer ring 20, the inner ring 17, and the torsion webs 21 are preferably configured integrally, for example from spring steel.

[0037] Axial positional securing of the rotary bearing 9 on the helical pinion shaft 4 takes place by interposing a coupling piece 22 by means of a screw 23 which is screwed into an internal thread which is integrated into the drive-side end of the helical pinion shaft 4. The coupling piece 22 also serves for transmitting a drive output of the steering motor to the helical pinion shaft 4, to which end said coupling piece 22 and said helical pinion shaft 4 are connected to one another in a rotationally fixed manner. This rotationally fixed connection is achieved on account of an external toothing 27 of the helical pinion shaft 4 engaging in a complementary internal toothing of the coupling piece 22.

[0038] Axial positional securing of the outer ring 20 of the pivot ring 16 within the housing 1 takes place by means of a screw ring 24 which has an external thread which is screwed into a complementary internal thread of the housing 1.

[0039] The two torsion webs 21 define the position of the pivot axis 7 about which the outer ring 20 is pivotable relative to the inner ring 17. The torsion webs 21 and thus the pivot axis 7 herein do not run through the center of the pivot ring 16 and thus also not through the center of the cross section of the helical pinion shaft 4, but so as to be radially offset thereto (cf. FIG. 2). The pivot axis 7 thus does not intersect the longitudinal axis 25 of the helical pinion shaft 4. On account of the radial offset of the torsion webs 21 to the center of the pivot ring 16, the pivot axis 7 is repositioned close to the external circumference of the helical pinion shaft 4 on account of which a configuration of reaction moments which result, or would result, respectively, as a consequence of the toothing forces resulting from the toothed engagement of the helical pinion 3 and the gear wheel 2, in conjunction with the spacing of the effective line of said toothing forces from the pivot axis 7 can be minimized or avoided. In order for said reaction moments to ideally be completely avoided, it is provided that the pivot axis 7 lies within that tangential plane which is configured in the point of contact of the two pitch circles, or rolling pitch circles, respectively, of the gear wheel 2 and the helical pinion 3.

[0040] The torsion webs 21 of the pivot ring 16 not only enable pivoting of the outer ring 20 in relation to the inner ring 17 and thus of the helical pinion shaft 4 relative to the gear wheel 2 or to the housing 1, respectively, but at the same time cause that spring force by way of which the helical pinion 3 of the helical pinion shaft 4 is pushed into the toothing of the gear wheel 2, so as to achieve an ideally minor gear play and thus a minor generation of noise in the operation of the steering gear, in particular in case of so-called alternating steering. This spring force from the helical pinion shaft 4 in the assembly of the steering gear as a result of contact with the gear wheel 2 being deflected so far that sufficient torsioning of the torsion webs 21 results, on account of which the elastic restoring moments which result from the torsioning of the torsion webs 21 act counter to said deflection of the helical pinion shaft 4 and thus impinge the latter against the gear wheel 2.

[0041] In order for an unintended generation of noise as a result of a relative movement of the elements (inner ring 17 of the pivot ring 16 and outer bearing ring 12 of the rotary bearing 9) that are received within the bearing sleeve 15 to be avoided in the operation of the steering gear and in particular also over the entire envisaged service life of the steering gear, it is provided that the inner ring 17 of the pivot ring 16 and the outer bearing ring 12 of the rotary bearing 9 are disposed so as to be braced between the tension ring 18 and the axial detent 19 which is configured by the bearing sleeve 15.

[0042] To this end it is provided in the context of the production of the fixed bearing 6 provided as a contiguous unit for integration in the steering gear that first the rotary bearing 9, subsequently the inner ring 17 of the pivot ring 16, and finally the tension ring 18 are positioned within the bearing sleeve 15 and a pretensioning force F.sub.V that acts in the direction of the axial detent 19 is thereafter applied (in an ideally fully circumferential manner) to the tension ring 18 (cf. FIG. 3), said pretensioning force F.sub.V leading to the bracing of the elements received within the bearing sleeve 15, wherein said pretensioning force F.sub.V exerted on the tension ring 18 is supported in that the bearing sleeve 15 is supported on a counter bearing (not illustrated) (cf. reaction force F.sub.R in FIG. 3). To this end, the bearing sleeve 15 externally configures one or a plurality of, respectively, supporting protrusions 26 which (collectively) extend across the largest part of the circumference of the bearing sleeve 15 and which are disposed on that axial end of the bearing sleeve 15 on which the tension ring 18 within the bearing sleeve 15 is also positioned. Like the axial detent 19 of the bearing sleeve 15, the supporting protrusions 26 can also have been configured by forming an axial end portion of the bearing sleeve 15.

[0043] Even while the pretensioning force F.sub.V is being actively applied to the tension ring 18, the tension ring 18 is permanently connected to the bearing sleeve 15, for example by welding, in particular by means of laser welding. The bracing of the inner ring 17 of the pivot ring 16 and of the outer bearing ring 12 of the rotary bearing 9 between the tension ring 18 and the axial detent 19 of the bearing sleeve 15 is permanently maintained on account thereof.

[0044] On account of applying the pretensioning force F.sub.V to the tension ring 18, on account of which the latter by way of a correspondingly high force is pushed against the inner ring 17 of the pivot ring 16 and the latter in turn against the outer bearing ring 12 of the rotary bearing 9, said outer bearing ring 12 in turn being supported on the axial detent 19 of the bearing sleeve 15, (in particular) the axial detent 19 of the bearing sleeve 15 is elastically deformed to a relevant degree, on account of which it is ensured that a play-free disposal of the inner ring 17 of the pivot ring 16 and of the outer bearing ring 12 of the rotary bearing 9 between the tension ring 18 and the axial detent 19 is provided even toward the end of an envisaged service life of the steering gear, since a wear-related readjustment of the inner ring 17 of the pivot ring 16 as well as of the outer bearing ring 12 of the ball bearing 9 takes place on account of the restoring effect of the elastically deformed axial detent 19 of the bearing sleeve 15.

LIST OF REFERENCE SIGNS

[0045] 1 Housing [0046] 2 Gear wheel [0047] 3 Helical pinion [0048] 4 (Helical) pinion shaft [0049] 5 Output shaft [0050] 6 Fixed bearing [0051] 7 Pivot axis [0052] 8 Floating bearing [0053] 9 Rotary bearing of the fixed bearing [0054] 10 Rotary bearing of the floating bearing [0055] 11 Inner bearing ring of a rotary bearing [0056] 12 Outer bearing ring of a rotary bearing [0057] 13 Bearing device of the fixed bearing [0058] 14 Bearing device of the floating bearing [0059] 15 Bearing sleeve [0060] 16 Pivot ring [0061] 17 Inner ring of the pivot ring [0062] 18 Tension ring [0063] 19 Axial detent of the bearing sleeve [0064] 20 Outer ring of the pivot ring [0065] 21 Torsion web [0066] 22 Coupling piece [0067] 23 Screw [0068] 24 Screw ring [0069] 25 Longitudinal axis of the helical pinion shaft [0070] 26 Supporting protrusion [0071] 27 External toothing of the helical pinion shaft