Device for level adjustment for a motor vehicle

Abstract

A device for level adjustment for a motor vehicle includes a ball screw. The screw nut of the ball screw is driven by an electric motor. The spindle of the ball screw is displaceable with respect to a housing. The ball screw is supported with respect to the housing using two axial self-aligning bearings with a common pivot point such that the housing can pivot with respect to the spindle, thereby avoiding loads on the balls of the ball screw.

Claims

1. A device for level adjustment for a motor vehicle, comprising a ball screw with a threaded spindle and a spindle nut which interacts with the threaded spindle via rolling bodies and which is drivable by means of an electric motor and which is mounted by two axial self-aligning ball bearings with respect to a housing which is displaceable with respect to the threaded spindle.

2. The device as claimed in claim 1, wherein the two axial self-aligning ball bearings have a common pivot point around which the spindle nut is pivotable together with the threaded spindle relative to the housing.

3. The device as claimed in claim 2, wherein the pivoting of the spindle nut together with the threaded spindle with respect to the housing is restricted by a plain bearing element which acts between the threaded spindle and the housing.

4. The device as claimed in claim 3, wherein the plain bearing element permits a pivoting between the threaded spindle and the housing up to an angle of at least 1.2 degrees.

5. The device as claimed in claim 4, wherein the pivoting between the threaded spindle and the housing is restricted to an angle of at most 5 degrees.

6. The device as claimed in claim 1, further comprising a pretensioning element which acts on one of the two axial self-aligning ball bearings.

7. The device as claimed in claim 1, wherein the electric motor interacts via a transmission with the spindle nut.

8. The device as claimed in claim 7, wherein a gear transmission is provided as a transmission.

9. The device as claimed in claim 1, wherein the axial self-aligning ball bearings are formed as multi-row self-aligning bearings.

10. The device as claimed in claim 2, wherein the common pivot point is not axially between the two self-aligning ball bearings.

11. A device for level adjustment for a motor vehicle, comprising: a housing; a threaded spindle displaceable with respect to the housing; and a spindle nut which interacts with the threaded spindle via rolling bodies, which is rotatable by means of an electric motor, and which is mounted relative to the housing by two axial self-aligning multi-row bearings, the two axial self-aligning multi-row bearings each having pivot points axially offset from the respective axial self-alignment multi-row bearing in a first axial direction.

12. The device as claimed in claim 11, wherein the pivot points of the two axial self-aligning multi-row bearings coincide with one another.

13. The device as claimed in claim 12, further comprising a plain bearing between the housing and the threaded spindle.

14. The device as claimed in claim 13, wherein the plain bearing element permits a pivoting between the threaded spindle and the housing up to an angle of at least 1.2 degrees and no more than 5 degrees.

15. The device as claimed in claim 11, further comprising a pretensioning element which acts on one of the two axial self-aligning multi-row bearings.

16. The device as claimed in claim 11, wherein the axial self-aligning multi-row bearings are ball bearings.

17. A device for level adjustment for a motor vehicle, comprising: a housing; a threaded spindle displaceable with respect to the housing; a plain bearing between the housing and the threaded spindle; and a spindle nut which interacts with the threaded spindle via rolling bodies, which is rotatable by means of an electric motor, and which is mounted relative to the housing by two axial self-aligning bearings, the two axial self-aligning bearings each having pivot points axially offset from the bearing in a first axial direction, wherein the pivot points of the two axial self-aligning bearings coincide with one another.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An exemplary embodiment is explained in greater detail below on the basis of a drawing. In the drawing:

(2) FIG. 1 shows a level adjustment device for a motor vehicle in a schematic sectional representation,

(3) FIG. 2 shows an axial self-aligning bearing according to FIG. 1 in a roughly schematic representation.

DETAILED DESCRIPTION

(4) A device for level adjustment for a motor vehicle designated in general by reference number 1, referred to in short as a level adjustment device, comprises a ball screw 2 with a threaded spindle 3 and a spindle nut 4, wherein balls run as rolling bodies 5 between threaded spindle 3 and spindle nut 4. Threaded spindle 3 is linearly displaceable within a housing 6 and is at the same time pivotable in relation to housing 6, wherein the pivoting of threaded spindle 3 with respect to housing 6 is restricted by a plain bearing element 7 which annularly surrounds threaded spindle 3. During operation of the motor vehicle, housing 6 is exposed to small, but not negligible pivoting movements about threaded spindle 3 which is connected to the vehicle structure.

(5) Spindle nut 4 is rotatable in housing 6 and simultaneously mounted in an axially fixed manner, as explained in greater detail below. An electric motor 9, which, in the exemplary embodiment, is arranged outside housing 6, drives spindle nut 4 via a transmission 8, namely a step-down transmission in the form of a gear transmission which is arranged within housing 6. Instead of gear transmission 8, a transmission of another design, for example, a belt drive could also be used. The motor shaft which couples electric motor 9 to transmission 8 is designated by 10. Motor shaft 10 is omitted in alternative configurations in which threaded spindle 3 is directly electrically driven and the rotor of electric motor 9 is connected as an annular rotor directly to threaded spindle 3.

(6) Two axial self-aligning bearings 11 which have in each case two bearings disks 12, 13 as well as balls 14 rolling between bearing disks 12, 13 are provided for mounting of spindle nut 4 in housing 6. Axial self-aligning bearings 11 are multi-row axial self-aligning ball bearings. Bearing disk 12 of each axial self-aligning bearing 11 is also referred to as a shaft-side bearing disk in short: shaft disk. Bearing disk 13 is the housing-side bearing disk, i.e. housing disk.

(7) In the case of a height adjustment of the structure of the motor vehicle having level adjustment device 1, the level of housing 6 is adjusted, while threaded spindle 3 is stationary. A spring plate which is only represented in outline and is connected above housing 6 fixedly thereto supports a chassis spring, not represented, wherein the longitudinal axis of the chassis spring generally does not coincide with the center axis of ball screw 2.

(8) A spring force F.sub.F is introduced into housing 6, wherein an angle α.sub.F is enclosed between the longitudinal axis of threaded spindle 3, i.e. the center axis of ball screw 2, and the direction of force vector F.sub.F. Said angle α.sub.F is represented in an exaggerated manner in FIG. 1. Force F.sub.F, in relation to the arrangement according to FIG. 1, acts on the upper of the two axial self-aligning bearings 11. In order to avoid this load in the case of a selected level adjustment of the chassis, a blocking device, not represented, exists, which has several adjustment levels and avoids the flow of force through rolling bodies 5. In this unloaded state of the two axial self-aligning bearings 11, a pretensioning force is generated by a pretensioning disk 15, generally referred to as a pretensioning element, which is arranged, relative to the arrangement according to FIG. 1, below lower axial self-aligning bearing 11, i.e. connected between its bearing disk 13 and housing 6. In this manner, rolling bodies 5 are always arranged in a play-free manner between bearing disks 12, 13 of axial self-aligning bearings 11.

(9) Each axial self-aligning bearing 11 can be tilted about a geometric pivot axis which is oriented orthogonally to the center axis of ball screw 2. The tilting direction is designated in FIG. 1 by KR and indicated by a curved arrow which lies in the pivoting plane. Pivotability means that both bearing disks 12, 13 of each axial self-aligning bearing 11 are pivotable relative to one another, wherein the corresponding pivot axis is referred to as center point M or pivot point. Pivot points M of both axial self-aligning bearings 11 coincide, as is apparent from FIG. 1, which is enabled by a different design of axial self-aligning bearings 11 which is not apparent from FIG. 1. The pivoting of housing 6 in relation to threaded spindle 3, which is enabled by the two axial self-aligning bearings 11, is restricted by means of plain bearing element 7 to a pivot angle of no more than 5 degrees.

(10) Within this pivoting range, the torque to be generated for actuation of ball screw 2 by electric motor 9 is independent of the orientation of threaded spindle 3 relative to housing 6. The function of a blocking device, not represented, with which discrete settings of level adjustment device 1 can be fixed while avoiding the flow of force running through running bodies 5, is independent of the pivotability of housing 6 produced by means of axial self-aligning bearings 11.

LIST OF REFERENCE NUMBERS

(11) 1 Level adjustment device 2 Ball screw 3 Threaded spindle 4 Spindle nut 5 Rolling body 6 Housing 7 Plain bearing element 8 Transmission 9 Electric motor 10 Motor shaft 11 Axial self-aligning bearing 12 Bearing disk 13 Bearing disk 14 Ball 15 Pretensioning element α.sub.F Angle F.sub.F Spring force HV Height adjustment KR Tilting direction M Center point, pivot point