Sliding Bearing Bushing for a Steering System

Abstract

The disclosure relates to a steer-by-wire system for a motor vehicle including a steering rod, an electric servo unit configured to move the steering rod, and a sliding bearing which radially supports the steering rod in a housing. The housing, the sliding bearing, and the steering rod have complementary geometries whereby the steering rod is prevented from rotating. The sliding bearing includes multiple segments in the circumferential direction, at least one segment of the multiple segments is a sliding bearing location for the radial support. At least one segment of the multiple segments is a first supporting element configured to prevent rotation in one direction of rotation. At least one segment of the multiple segments is a second supporting element configured to prevent rotation in the opposite direction of rotation.

Claims

1. A steer-by-wire system for a motor vehicle, comprising: a steering rod; an electric servo unit configured to move the steering rod; and a sliding bearing which radially supports the steering rod in a housing, wherein the housing, the sliding bearing, and the steering rod have complementary geometries whereby the steering rod is prevented from rotating, the sliding bearing includes multiple segments in the circumferential direction, at least one segment of the multiple segments is a sliding bearing location for the radial support, at least one segment of the multiple segments is a first supporting element configured to prevent rotation in one direction of rotation, and at least one segment of the multiple segments is a second supporting element configured to prevent rotation in the opposite direction of rotation.

2. The steer-by-wire system as claimed in claim 1, wherein: the sliding bearing has at least one radial projection, which comprises a plurality of the multiple segments; a sliding bearing location is arranged on the at least one projection; and at least one of the first and second supporting elements is arranged laterally on the at least one projection.

3. The steer-by-wire system as claimed in claim 1, wherein: the sliding bearing has at least one radial recess which comprises a plurality of the multiple segments; a sliding bearing location is arranged in the at least one radial recess; and at least one of the first and second supporting elements is arranged laterally on the at least one radial recess.

4. The steer-by-wire system as claimed in claim 1, wherein: the sliding bearing has at least one radial projection and one radial recess, which each comprise a respective plurality of the multiple segments; a sliding bearing location is arranged on at least one of the projection and the recess; and at least one of the first and second supporting elements is arranged laterally on at least one of the projection and/or the recess.

5. The steer-by-wire system as claimed in claim 1, wherein: the first and second supporting elements are composed of an elastic material and can deflect under loading.

6. The steer-by-wire system as claimed in claim 5, wherein the first and second supporting elements each consist of a respective curved spring sheet.

7. The steer-by-wire system as claimed in claim 6, wherein the first and second supporting elements consisting of respective spring sheets are each secured on only one side.

Description

[0011] One embodiment of the invention is now described with reference to the figures, of which:

[0012] FIG. 1 shows a schematic illustration of a steering system of a vehicle

[0013] FIG. 2 shows a perspective view of the sliding bearing according to the invention

[0014] FIG. 3 shows the sliding bearing according to the invention in the installed state

[0015] FIG. 4 shows the sliding bearing according to the invention

[0016] FIG. 5 shows a detail view of the sliding bearing according to the invention

[0017] FIG. 1 shows a schematic illustration of a steer-by-wire system of a vehicle. The steering commands are recorded by a sensor 4 at the steering input unit with a steering wheel 1 and a force feedback motor 2. The signals are transmitted to a control device 5, which is situated on the lower assembly, the steering rack actuator. The control device 5 controls the servo motor 6, which drives the ball screw via a belt transmission 7, whereby ultimately the steering rod 3 is moved. The steering rod 3 adjusts the steering angle at the wheels via the tie rods 9. The steering rod 3 is supported by the sliding bearing 10 according to the invention.

[0018] FIG. 2 shows the sliding bearing 10 according to the invention. It can be seen that the sliding bearing in this embodiment is of clover leaf-shaped configuration in cross section, that is to say, for example, has four projections. The projections are uniformly distributed over the circumference. The uniform distribution makes it possible to achieve a virtual pair of forces, thereby ensuring that there is freedom from transverse forces, and hence the resulting frictional forces in the longitudinal direction of the rack are significantly reduced.

[0019] The clover leaf-shaped cross-sectional shape of the sliding bearing is also readily apparent in FIG. 3, which shows the sliding bearing 10 in the installed state. The sliding bearing 10 is arranged between the steering rod 3 and the housing 11.

[0020] FIG. 4 shows the sliding bearing in an enlarged view. A sliding bearing location 12 is arranged in each case on the projection or on a highest elevation. The contour of the sliding bearing location 12 is laterally arc-shaped. The arc-shaped design allows relative rotation of the steering rod about the longitudinal axis thereof in the sliding bearing, which means that no rotation prevention function is implemented at this location or that this function is affected. The sliding bearing locations 12 thus contribute purely to the function of radial support.

[0021] The supporting elements 13, 14 are arranged on the sides of a projection. On a first side of the projection, it is possible to arrange a supporting element 13 which acts when the steering rod is rotated clockwise. On the other side of the projection, it is possible to arrange a further supporting element 14, which acts when the rack is rotated counterclockwise.

[0022] The supporting elements 13, 14 are composed of an elastic material and can deflect under loading. As can be seen in FIG. 2, the supporting elements 13, 14 consist of a curved spring sheet, which has a plurality of curves. The amplitude, wavelength, width and sheet thickness of the curves can be defined precisely in accordance with requirements.

[0023] Between the projections there are connecting elements 15. These are used only as a guiding-supporting structure and do not necessarily have contact with the steering rod and the housing. The sliding bearing is delimited at its two ends by connecting rings. These two are merely part of the supporting structure and are not necessarily in contact with the steering rod.

[0024] The stiffness properties of the supporting elements 13, 14 can be set in accordance with requirements. For this purpose, each supporting element is given a suitable curvature. For example, the steering rod can be provided with a stronger spring action in the upward direction than in the downward direction.

[0025] The supporting elements 13, 14 can also contribute to the radial bearing function. This can be employed and used selectively through the choice of bearing clearance in the sliding bearing locations 12 in combination with the stiffness behavior of the supporting elements 13, 14. If, for example, a very small bearing clearance is chosen in the sliding bearing location 12 and the spring action of the supporting elements 13, 14 is very soft, this effect is negligible. If the bearing clearance in the sliding bearing location 12 is very large and the spring action of the supporting elements 13, 14 is very stiff, this effect assists radial support. In this case, a person skilled in the art must identify the optimum for the respective application.

[0026] The supporting elements 13, 14 provided with curves can increase in length when compressed, which may lead to stresses in the sliding bearing if they are secured on both sides. FIG. 5 therefore shows an embodiment in which the supporting element 13 is attached on only one side.