POWER-ASSISTED STEERING FOR A MOTOR VEHICLE

Abstract

A power assisted steering system may include a threaded spindle that engages in a spindle nut, extends in a direction of a spindle axis, and is axially displaceable in a housing; and a drive unit having a gearwheel that is connected to the spindle nut in a rotationally fixed manner, can be driven rotatably about the spindle axis, and is rotatably mounted in the housing in a bearing arrangement. The bearing arrangement may have at least one bearing outer ring that is axially supported on the housing at an end face via a spring element, that is received coaxially in a sleeve element, and that is held radially in the housing. The spring element may be formed as a spring portion, and the sleeve element may be formed as a sleeve portion that is connected in one piece to the spring portion, on a one-piece carrier sleeve.

Claims

1.-14. (canceled)

15. A power assisted steering system for a motor vehicle, comprising: a threaded spindle that engages in a spindle nut, extends in a direction of a spindle axis, and is axially displaceable in a housing; and a drive unit having a gearwheel that is connected to the spindle nut in a rotationally fixed manner, is rotatably drivable about the spindle axis, and is rotatably mounted in the housing in a bearing arrangement, with the bearing arrangement including a bearing outer ring that is axially supported on the housing at an end face via a spring element and that is received coaxially in a sleeve element and held radially in the housing, wherein the spring element is configured as a spring portion and the sleeve element is configured as a sleeve portion that is connected in one piece to the spring portion, on a one-piece carrier sleeve.

16. The power assisted steering system of claim 15 wherein the spring portion protrudes radially inwards from the sleeve portion.

17. The power assisted steering system of claim 15 wherein the spring portion has a wave spring.

18. The power assisted steering system of claim 15 wherein the spring portion has a disk spring.

19. The power assisted steering system of claim 15 wherein the sleeve portion is a tube.

20. The power assisted steering system of claim 15 wherein the sleeve portion is resiliently tensioned radially externally against the bearing outer ring.

21. The power assisted steering system of claim 15 wherein the sleeve portion is segmented in a circumferential direction.

22. The power assisted steering system of claim 15 wherein the sleeve portion includes fastening means for axial fixing on the bearing outer ring.

23. The power assisted steering system of claim 15 wherein the one-piece carrier sleeve is comprised of metallic material.

24. The power assisted steering system of claim 15 wherein the one-piece carrier sleeve is comprised of plastic.

25. The power assisted steering system of claim 15 wherein a rolling bearing of the bearing arrangement includes the bearing outer ring.

26. The power assisted steering system of claim 15 wherein the gearwheel is disposed axially between bearings in the bearing arrangement.

27. The power assisted steering system of claim 15 wherein the threaded spindle is connected to a toothed rack of a rack and pinion steering gear.

28. The power assisted steering system of claim 15 wherein the threaded spindle and the spindle nut form a ball screw drive.

Description

DESCRIPTION OF THE DRAWINGS

[0031] Advantageous embodiments of the invention are explained in more detail below with reference to the drawings. In detail:

[0032] FIG. 1 shows a schematic perspective view of an inventive steering system;

[0033] FIG. 2 shows a schematic perspective partial view of the spindle drive of the steering system according to FIG. 1 in isolation;

[0034] FIG. 3 shows a longitudinal section along the spindle axis through the spindle drive according to FIG. 2;

[0035] FIG. 4 shows a schematic illustration, exploded in the axial direction, of the bearing arrangement of the spindle drive according to FIGS. 2 and 3;

[0036] FIG. 5 shows a perspective view of an inventive carrier sleeve;

[0037] FIG. 6 shows a schematic exploded illustration of the bearing arrangement in a second embodiment;

[0038] FIG. 7 shows a longitudinal section through the bearing arrangement according to FIG. 6;

[0039] FIG. 8 shows an enlarged illustration of a detail from FIG. 7.

EMBODIMENTS OF THE INVENTION

[0040] In the various figures, the same parts are always denoted by the same reference signs and are therefore generally also only mentioned or explained once.

[0041] FIG. 1 shows a power assisted steering system 1 of a motor vehicle steering system in a schematic view. This power assisted steering system comprises a steering shaft 2, which is connected to a steering wheel 21, possibly via an intermediate shaft (not illustrated), at its rear end facing the driver's position in the vehicle interior, and may be rotated to input a manual steering command, as indicated by the arrow.

[0042] The front end of the steering shaft 2 is rotatably mounted in a housing 31 of a steering gear 3.

[0043] In the housing 31, a toothed rack 4 (illustrated separately in FIG. 2), which extends in the direction of a spindle axis S, is mounted to be displaceable in its longitudinal direction i.e. in the direction of said spindle axis S, as indicated by a double headed arrow in FIG. 1.

[0044] The toothed rack 4 has a toothing 41 and a thread 42. A steering pinion, mounted on the steering shaft 2 and arranged concealed within the housing 31, is in engagement with the toothing 41 so that a rotation of the steering shaft 2 is converted into a linear movement of the toothed rack 4 in the housing 31. At its two ends, to transfer the steering power, the toothed rack 4 is connected to the steering knuckles 52 of the steered wheels (not illustrated here) via track rods 5 and joint heads 51.

[0045] An auxiliary power drive has an electric motor 32 which is mounted on the housing 31 and via which a gearwheel 6 can be driven for rotation about the spindle axis S. For this purpose, the gearwheel 6 has an external ring gear 61 revolving coaxially about the spindle axis S and having a toothing which meshes with a drive pinion of the motor 32.

[0046] The hub of the gearwheel 6 has a spindle nut 62, which is screwed onto the thread 42 of the toothed rack 4 and is connected to the ring gear 61 in a fixed manner. In the example shown, the spindle nut 62 is designed as a ball nut or ball screw nut, having a threaded body 63 with helical ball channels. Balls circulate in a guided manner between the helical ball channels and the turns of the thread 42 and are returned externally via a deflection body 65, which is elevated radially outwards in the exploded illustration of FIG. 4.

[0047] The gearwheel 6 is mounted for rotation about the spindle axis S in a bearing arrangement between two mirror-symmetrically arranged rolling bearings 7 and, in this case, is axially supported against the housing 31 in the direction of the spindle axis S.

[0048] Each of the rolling bearings 7 has a bearing outer ring 71, in which balls 72 can roll internally, which balls are rotatably held in a ball cage 73. The bearing inner ring, which is connected to the gearwheel 6 in a fixed manner, is formed by ball raceways 74, which are arranged on the threaded body 63 of the spindle nut 62 and along which the balls 72 may roll. The ball raceways 74 may preferably be formed in one piece on the threaded body 63.

[0049] The thread 42 forms the threaded rod of a ball screw drive, which, by means of the motor 32, may be linearly axially displaced in the direction of the spindle axis via a rotating drive. Auxiliary power supporting the steering torque introduced manually via the steering shaft 2 may thus be exerted on the toothed rack 4.

[0050] An inventive carrier sleeve 8 (illustrated separately in FIG. 5) is pushed externally onto the bearing outer ring 71 in the axial direction in each case, as indicated by the arrows in FIG. 4.

[0051] The connecting lines (depicted by dashed lines in FIG. 3) between the contact points between the balls 72 and the ball raceways 74 and the bearing outer ring 71 intersect the spindle axis between the two rolling bearings 7 so that an X configuration is produced.

[0052] The carrier sleeve 8 has a tubular sleeve portion 81, which has a substantially hollow cylindrical design. The sleeve portion 81 is connected in one piece to an end-face spring portion 82. In the embodiment of FIGS. 3, 4 and 5, this spring portion is designed as a wave spring in the form of a washer, which protrudes radially inwards into the passage of the sleeve portion 81 and has waves 83 which undulate forwards and backwards in the direction of the spindle axis S. The carrier sleeve this has an approximately cup-shaped design, wherein the wave spring forms the base.

[0053] In the installed state, the undulating spring portion 82 is axially pre-tensioned between the outer end face of the bearing outer ring 71 and a preferably ring-shaped abutment inside the housing 31.

[0054] Resilient spring tongues 85 are formed by a plurality of axial incisions 84, which are distributed over the circumference and are incorporated from the side which faces away from the spring portion 82. These spring tongues are radially spaced such that, during the push-on procedure, they are spread slightly apart in a resilient manner in the radially outward direction by the bearing outer ring 71 and thereby elastically clamp the bearing outer ring 71. The carrier sleeve 8 may be simply pushed on axially for assembly purposes, wherein the outer bearing ring 71 penetrates into the sleeve portion 81 until it lies internally against the spring element 72. In this case, it is resiliently clamped by the spring tongues 85 and held with force fit.

[0055] Fastening means 86 may be provided axially with respect to the spring tongues 85, at the end which faces away from the spring portion 82, which fastening means have, for example, inwardly protruding holding projections which may embrace the bearing outer ring 71 or between which the bearing outer ring 71 may be snapped in place with form fit.

[0056] FIGS. 6, 7 and 8 show a bearing arrangement having bearings 7, with an inventive carrier sleeve 8 in a second embodiment. The other components are denoted by the same reference signs provided they have the same functional effect.

[0057] The carrier sleeve 9 likewise has a similarly designed sleeve portion 81 for fixing on the outer circumference of the bearing outer ring 71.

[0058] Instead of the wave spring having the undulating spring portion 82, a radially inwardly protruding ring portion 86, tapering axially outwards from the sleeve portion 81 in the form of a lateral cone surface, is provided. This ring portion is located with its radially outer contact region A against the end face of the bearing outer ring 71 and with its radially inner contact region B, which faces axially outwards, against the housing 31, as can be seen in the enlarged detailed view of FIG. 8. The ring portion 86 thus acts as a disk spring, which is in the form of a lateral cone surface and by means of which an axial resilient pre-tensioning force may be exerted on the bearing 7 and the gearwheel 6 arranged therebetween.

[0059] The carrier sleeve 8 may be designed as a one-piece plastic molded part, for example injection molded from a thermoplastic material, which may be fiber-reinforced. Alternatively, it is conceivable and possible for it to be manufactured as a formed sheet-metal part, for example cold formed from steel or spring steel sheet.

LIST OF REFERENCE SIGNS

[0060] 1 Power assisted steering system

[0061] 2 Steering shaft

[0062] 21 Steering wheel

[0063] 3 Steering gear

[0064] 31 Housing

[0065] 32 Motor

[0066] 4 Toothed rack

[0067] 41 Toothing

[0068] 42 Thread

[0069] 5 Track rod

[0070] 51 Joint head

[0071] 52 Steering knuckle

[0072] 6 Gearwheel

[0073] 61 Ring gear

[0074] 62 Spindle nut

[0075] 63 Threaded body

[0076] 64 Balls

[0077] 65 Deflection body

[0078] 7 Bearing (rolling bearing)

[0079] 71 Bearing outer ring

[0080] 72 Balls

[0081] 73 Ball cage

[0082] 74 Ball raceway

[0083] 8 Carrier sleeve

[0084] 81 Sleeve portion

[0085] 82 Spring portion

[0086] 83 Shaft

[0087] 84 Incision

[0088] 85 Spring tongue

[0089] 86 Ring portion

[0090] S Spindle axis

[0091] A, B Contact regions