CN112196906A

CN112196906A - Noise-optimized bearing unit for a power steering system

Info

Publication number: CN112196906A
Application number: CN202010650542.9A
Authority: CN
Inventors: 乔纳斯·吉尔斯多夫; 约翰内斯·兰格
Original assignee: Schaeffler Technologies AG and Co KG
Current assignee: Schaeffler Technologies AG and Co KG
Priority date: 2019-07-08
Filing date: 2020-07-08
Publication date: 2021-01-08
Also published as: DE102019118406A1

Abstract

The invention relates to a noise-optimized bearing unit suitable for use in a power steering system. A bearing unit for a steering mechanism of a motor vehicle comprises a rolling bearing with an outer ring, an inner ring and rolling bodies designed as balls; the outer ring is mounted in a pivotable manner by means of the hemispherical outer surface in a correspondingly designed bearing housing of the stationary outer body, so that the rolling bearing can be pivoted against the bearing housing about a pivot axis aligned transversely to the bearing axis and the relative position of the contact regions of the bearing housing and the outer ring can be varied to compensate for manufacturing tolerances; at least one circulation groove is introduced into the hemispherical outer surface of the outer ring, and a flexible pretensioning element supported on the bearing box of the outer body in a ball-and-socket shape in a force fit manner is matched in the circulation groove; the pretensioning element allows a slight pivoting movement of the worm spindle relative to the stationary housing in the operating state, which is formed by the toothing between the worm wheel and the worm spindle.

Description

Noise-optimized bearing unit for a power steering system

Technical Field

The invention relates to a bearing unit for a steering gear of a motor vehicle, comprising a rolling bearing with an outer ring, an inner ring and rolling bodies guided in the middle, said rolling bodies being designed as balls, wherein the outer ring with a hemispherical outer surface is mounted in a pivotable manner in a bearing housing of an outer body, which is of corresponding design, such that the rolling bearing can be pivoted against the bearing housing about a pivot axis aligned transversely to the bearing axis and the relative position of the contact regions of the bearing housing and the outer ring can be varied to compensate for installation and/or manufacturing tolerances.

Background

Electric steering assistance in motor vehicles is usually realized by an electric motor which transmits torque to a steering shaft via a worm gear. The worm gear is formed by a worm wheel and a worm shaft, wherein the worm wheel and the steering shaft form a structural unit. The worm shaft connected to the electric motor is supported by a floating bearing and a fixed bearing. In order to expose the gap between the worm wheel and the worm shaft, the worm shaft is tilted and for this purpose pressed against the worm wheel preferably by means of a floating bearing, wherein the associated fixed bearing is of tiltable or pivotable design. The pivoting of the fixed bearing unit is effected here by an outer body, also referred to as a pivot ring, whose ball socket receives the outer ring of the fixed bearing with a hemispherical outer surface.

The manufacturing process-dependent play between the outer body socket and the stationary bearing outer ring often causes undesirable and harmful noise when the vehicle is in operation. Attempts have been made to reduce the play present in the bearing unit with partly higher costs and a large number of additional components. For example, in order to minimize the clearance, the mating members, the outer shell surface of the outer ring, and the seat of the ball socket are ground with high precision, but this also does not provide satisfactory results.

EP 1453717B 1 shows a steering gear worm shaft which is designed to support a pivotably mounted fixed bearing on one end and a floating bearing on the other free shaft end. The worm shaft can be pivoted in the direction of the worm wheel by means of the pivot bearing and thereby can be brought into engagement with the worm wheel. The pressure-receiving element acting on the floating bearing, together with the spring element, ensures a radially elastic support and thus an engagement of the two gear parts, the worm shaft and the worm wheel. However, such a bearing unit with a pivot lever cannot be realized in a completely play-free manner.

Another bearing unit suitable for steering gears, which consists of an outer body and a rolling bearing, is known from DE 102007044618 a 1. In order to show the pivot bearing arrangement, the outer bearing ring with the semicircular outer lateral surface is supported on a bearing of the outer body formed by the two ring elements. Two ring elements arranged in a mirror-symmetrical manner are joined by an outer U-shaped connecting element and form a bearing for the outer bearing ring on the inside, which bearing is designed as a ball socket. For mounting the outer body, the ring element is pushed from different sides in the direction of the bearing axis of the rolling bearing onto the outer circumferential surface of the outer bearing ring. The ring element can be pressed with a defined pressing force against the outer circumferential surface of the outer bearing ring while maintaining the slight axial distance, wherein the outer U-shaped connecting element locks the position of the ring element by plastic deformation.

DE 102008042608 a2 shows a worm shaft bearing arrangement for a steering gear, comprising a floating bearing and a pivot bearing, wherein the pivot bearing comprises a spring element. For example, a spring washer is designed as the spring element, which exerts an axial force directly on the outer ring of the wobble bearing with two flange-like projections arranged opposite one another. With this elastic support, which acts on the pivotable bearing arrangement of the worm shaft, a play-free, noise-optimized pivot bearing is to be achieved.

Disclosure of Invention

The object of the invention is to provide a pivotable bearing unit for a steering gear, which has a noise-optimized and play-free rolling bearing assembly, can be mounted in a simplified manner and can be produced at low production costs.

This object is achieved by a bearing unit having a structure corresponding to the features of claim 1. Advantageous embodiments or embodiments are described in the dependent claims 2 to 10.

The solution according to the invention provides that at least one circulation groove is introduced into the hemispherical outer surface of the outer ring of the roller bearing of the pivotable bearing unit, in which circulation groove an elastic pretensioning element is fitted, which is supported in a force-fitting manner on a bearing housing of the outer body in the form of a ball and socket. The invention allows a slight pivoting movement of the worm spindle, also referred to as worm shaft, relative to the stationary housing, which is formed by the toothing between the worm wheel and the worm shaft in the operating state.

The pretensioning element generates a pretensioning force which is distributed almost uniformly over the circumference and acts both axially and radially as a function of the radius of the ball socket on the basis of the ball socket-shaped mating pressure surface of the outer body. This leads to an almost uniform gap reduction in the wobble region between the outer body made of sintered metal and the outer ring of the rolling bearing.

The outer ring of the rolling bearing is placed in all pivoting positions with no play against the outer body, also referred to as the pivot ring, by means of a resilient pretensioning element which can exert the action of a spring element. The use of a radially acting spring support in connection therewith provides a bearing structure for the worm shaft which does not allow free play and which is effective in damping movements and reducing noise.

Advantageously, the provision of the gap reduction by means of advantageous additional elements during the production process according to the invention makes it possible to allow a larger gap in the pivot region of the bearing unit, which leads to a cost reduction during the production process. By using the prestressing element, an effective, durable and inexpensive spring support can also be achieved in the defined installation space of the bearing unit.

With respect to known solutions, namely: by positioning the pretensioning element in a socket-like design of the outer body made of sintered metal, a simpler and more cost-effective production process can be achieved by mounting the pretensioning element in the outer ring of the rolling bearing. In the known solutions, the introduction of the circulation grooves on the inner contour of the outer body requires an additional machining operation, which results in disadvantageous, increased manufacturing costs. In contrast, the invention provides that, during the cutting-off of the outer ring, at least one circulation groove for the prestressing element needs to be introduced into the outer circumferential surface or outer diameter of the outer ring of the roller bearing made of roller bearing steel. The circulation tank can be realized simply at low additional costs, which has little effect on the production costs. In addition, the installation of the prestressing element on the outer diameter can be carried out significantly more simply, in particular mechanically, than the installation of the prestressing element on the inner diameter of the sintered ring.

By means of the geometric design of the circulation grooves and the width, number, position or arrangement and material selection of the springs or pretensioning elements, the pretensioning force and thus the installation gap between the outer body and the ball bearing outer ring can be influenced in a targeted manner. In this connection, it is advantageous that the steering gear can be specifically damped during operation, noise-reduced and the pivot moment controlled. In addition, the measures according to the invention also make it possible to effectively suppress disturbing noise when the steering is in operation, even when the load changes.

The solution according to the invention provides a pivotable bearing unit for a power-assisted steering system, which comprises a play-free and noise-optimized rolling bearing arrangement, which requires low outlay on production and assembly and can therefore be produced at low cost.

According to an advantageous embodiment of the invention, two spring biasing elements are mounted in the outer circumferential surface of the outer ring, each of which is axially spaced apart from the center of the roller bearing. Advantageously, the pretensioning element is positioned at a uniform distance from the center of the outer ring. In addition, the outer ring may optionally also comprise more than two, for example three or four, pretensioning elements of smaller dimensions in order to be able to cover a larger surface area of the outer shell.

An advantageous geometric design provides that the outer ring shell surface is designed to be convex and the bearing housing of the outer body is designed to be concave, wherein the interacting contact areas have a mutually corresponding design.

In order to obtain an optimized bearing unit for the component, the invention provides that an outer body of one-piece construction is mounted. The bearing housing of the outer body comprises a cylindrical section which extends from the end face over half the width of the outer body and to which a bearing of ball-and-socket design is directly connected. When using a one-piece outer body, the bearing housing allows the rolling bearing to be mounted into the outer body from the side.

The pretensioning element, which has a preferably circular or circular cross-sectional profile, is preferably mounted in a U-shaped circulation groove of the outer ring. As an alternative, it is also possible to use pretensioning elements having a non-circular cross-sectional shape, which can be combined with corresponding, for example non-U-shaped, circulation grooves.

The pretensioning element according to the invention, which surrounds the outer ring of the rolling bearing and is mounted in the circulation groove with play, is elastically deformed during assembly or in the installed state. The elastic deformation of the pretensioning element can be automatically adjusted on the basis of the automatically adjustable contact pressure between the contact region of the outer body ball-and-socket bearing housing and the hemispherical outer surface of the outer bearing ring of the rolling bearing. In order to achieve an elastic deformation of the pretensioning element when the rolling bearing is installed in the outer body, the cross-sectional profile of the circulation groove exceeds the cross-sectional profile of the pretensioning element.

Preferably, plastic is provided as the material of the pretensioning element mounted between the outer ring of the rolling bearing and the outer body. For example, elastomer springs or O-rings made of an elastomer can be used for this purpose. The advantage of O-rings is that they can in principle be obtained at low cost in a variety of standardized diameters or O-ring cross-sectional diameters. In this way, the pretensioning force in the pivoting region can be influenced in an advantageous manner and the customer requirements can be met. However, the material choice for the pretensioning element is not limited to plastic. Alternatively, it is proposed to use a prestressing element made of sheet metal, for example a radial wave spring made of spring steel.

The invention is preferably used for bearing units with power steering, in which the worm spindle is supported by means of a pivotable rolling bearing mounted in the outer body. In order to engage the worm spindle in the toothing of the worm wheel with reduced or no play, the bearing unit comprises at least one elastic pretensioning element. In addition, the bearing unit according to the invention is also suitable for different applications, for example when it is required to simplify manufacture, to optimize the mounting or to design the clearance independently of tolerances.

Drawings

The accompanying drawings illustrate preferred embodiments of the present invention, and together with the description below, further features, advantages and effects of the invention will become apparent from the following description of the drawings. However, the invention is not limited to the embodiments shown. Brief description of the drawings:

FIG. 1: a background art vehicle steering system is schematically shown;

FIG. 2: a bearing unit suitable for a assisted steering mechanism having the structure of the present invention is shown in a sectional view;

FIG. 3: the rolling bearing shown in the bearing unit of figure 2 is illustrated in a detail view;

FIG. 4: the bearing unit according to the invention is shown in perspective.

Description of the reference numerals

1 steering mechanism 2 motor 3 worm drive 4 steering column 5 output shaft 6 clutch 7 worm main shaft 8 worm wheel 9 rolling bearing 10 motion degree 11 rolling bearing 21 bearing unit 22 rolling bearing 23 outer body 24 inner ring 25 outer ring 26 rolling bearing retainer 27 rolling bearing 28 outer surface 29 bearing box 30 bearing axis 31 swing axis 32 pretension element 33 circulation groove 34 segment

Detailed Description

Fig. 1 shows the structure of a known motor vehicle power steering system 1 (also referred to as a power steering system), in which the output torque of an electric motor 2 is transmitted via a worm drive 3 to a steering column 4 (not shown) of the motor vehicle. For this purpose, the output shaft 5 of the electric motor 2 is coupled in a rotationally fixed manner via a clutch 6 to a worm spindle 7, whose toothing meshes with an external toothing of a worm wheel 8 of the steering column 4. When such a steering mechanism 1 is in operation, an excessive play between the worm wheel 8 and the worm spindle 7 can lead to the generation of undesirable noise. As a measure for noise avoidance, the bearing arrangement of the worm spindle 7 comprises a first rolling bearing 9, which is designed as a fixed bearing and which can be pivoted by means of a ball joint about a pivot axis oriented transversely to the bearing axis. The pivoting movement is achieved by a second spring-loaded rolling bearing 11, which is arranged at the end of the worm spindle 7 and is designed as a floating bearing and has a degree of movement 10. The ball joint of the roller bearing 9 comprises an outer bearing ring with a hemispherical outer jacket surface, which is introduced into a ball-and-socket-like seat of a stationary outer body (not shown) surrounding the roller bearing 9. In order to reduce the manufacturing or mounting clearance of the co-acting components, the contact surface between the outer body and the outer bearing ring needs to be manufactured with high precision.

Fig. 2 shows a bearing unit 21 according to the invention, which is suitable for a pivotable bearing arrangement of a worm spindle. The bearing unit 21 comprises a rolling bearing 22 designed as a ball bearing which is mounted in a swingable manner in a fixedly positioned outer body 23. Between the inner ring 24 and the outer ring 25 of the rolling bearing 22, rolling elements 27, which are guided on guide rails and are mounted in rolling element cages 26 and are designed as balls, are arranged. The outer ring 25 is mounted in a pivotable manner by means of a hemispherical outer shell surface 28 in a correspondingly designed ball-and-socket bearing housing 29 of the outer body 23. For this purpose, the roller bearing 22 can be pivoted to a limited extent against the bearing housing 29 about a pivot axis 31 aligned transversely to the bearing axis 30. In order to compensate for installation and/or manufacturing tolerances, a resilient pretensioning element 32 is provided between the contact area of the female bearing housing 29 of the outer body 23 and the contact area of the male housing surface 28 of the outer ring 25. In the mounted state, the pretensioning element 32 mounted in the circulating groove 33 of the outer ring 25 is supported in a force-fitting manner on the bearing housing 29 of the outer body 23. In order to be able to mount the outer ring 25 or the rolling bearing 22 in the one-piece outer body 23, a cylindrical segment 34, the diameter of which slightly exceeds the outer diameter of the rolling bearing outer ring 25, is connected to the ball-and-socket bearing housing 29 at the end face facing the outer body 23.

To show more detail, the rolling bearing 22 is shown in a single piece in fig. 3 and 4. In the convexly designed outer shell surface of the outer ring 25, two circulation grooves 33 with a U-shaped cross-sectional profile are introduced spaced apart from the center of the rolling bearing 22. The circulation grooves are each intended to receive a pretensioning element 32 designed as an O-ring.

Claims

1. Bearing unit (21) for a steering gear (1) of a motor vehicle, comprising a rolling bearing (22) having an outer ring (25), an inner ring (24) and rolling bodies (27) designed as balls, wherein the outer ring (25) is mounted in a correspondingly designed bearing housing (29) of a stationary outer body (23) in a pivotable manner by means of a hemispherical outer surface (28), as a result of which the rolling bearing (22) can be pivoted against the bearing housing (29) about a pivot axis (31) aligned transversely to a bearing axis (30) and the position of the contact region of the bearing housing (29) and the outer ring (25) can be varied to compensate for installation and/or manufacturing tolerances, characterized in that at least one circulation groove (33) is introduced into the hemispherical outer surface (28) of the outer ring (25), an elastic pretensioning element (32) is mounted in the circulation groove and is supported on the ball-and-socket bearing housing (29) of the outer body (25) in a force-fitting manner, wherein the pretensioning element (32) allows a slight pivoting movement of the worm spindle (7) relative to the stationary housing in the operating state, which is formed by the toothing between the worm wheel (8) and the worm spindle (7).

2. Bearing unit according to claim 1, wherein two spring biasing elements (32) are mounted in the outer circumferential surface (28) of the outer ring (25), each of which is axially spaced from the center of the rolling bearing (22).

3. Bearing unit according to any of the preceding claims, wherein the outer ring (25) has a convex outer shell surface (28) and the outer body (23) has a corresponding concave bearing housing (29).

4. Bearing unit according to any of the preceding claims, wherein an outer body (23) of one-piece construction is provided for the bearing unit (21).

5. Bearing unit according to any of the preceding claims, wherein the bearing housing (29) of the outer body (23) has a cylindrical section (34) to which the ball-and-socket-like designed region of the bearing housing (29) is connected.

6. Bearing unit according to any of the preceding claims, wherein a pretensioning element (32) with a circular cross-sectional profile is mounted in a U-shaped circulating groove (33) of the outer ring (25).

7. Bearing unit according to one of the preceding claims, wherein the cross-sectional profile of the circulation groove (33) exceeds the cross-sectional profile of the pretensioning element (32) and thereby ensures an elastic deformation of the pretensioning element (32) when the rolling bearing (22) is mounted into the outer body (23).

8. Bearing unit according to any of the preceding claims, wherein a pretensioning element (32) made of plastic is mounted between the outer ring (25) of the rolling bearing (22) and the outer body (23).

9. Bearing unit according to one of the preceding claims, wherein a pretensioning element (32) made of sheet metal is assigned to the outer ring (25) of the rolling bearing (22).

10. The bearing unit (21) as claimed in one of the preceding claims is suitable for a belt-assisted steering (1) comprising a pivotable rolling bearing (22) mounted in the outer body (23) for mounting the worm spindle (7), wherein the bearing unit (21) comprises at least one elastic pretensioning element (32) for engaging the worm spindle (7) in the toothing of the worm wheel (8) with reduced or no play.