Worm Drive

Abstract

A worm drive for a power steering system of a motor vehicle is disclosed. The worm drive includes a worm gear, a worm which meshes with the worm gear, and an electric motor which drives the worm. One side of the worm is connected by a coupling to the electric motor and the other side of the worm is mounted in a floating bearing. The coupling consists of a hub and an elastic spring bush. The floating bearing is oval-shaped in order to allow vertical movements of the worm, and the worm is spring-loaded on the worm gear by the coupling.

Claims

1. A worm drive for a power-assisted steering system of a motor vehicle, comprising: a worm gear; a worm configured to mesh with the worm gear; an electric motor configured to drive the worm; a coupling; and a floating bearing, wherein one side of the worm is connected by the coupling to the electric motor and the other side of the worm is supported in the floating bearing, wherein the coupling comprises a hub and an elastic spring bush, wherein the floating bearing is configured to be oval-shaped so as to allow vertical movements of the worm, and wherein the worm is preloaded onto the worm gear by the coupling.

2. The worm drive as claimed in claim 1, further comprising a fixed bearing configured to support the worm on the drive shaft of the electric motor.

3. The worm drive as claimed in claim 1, wherein: the hub is pressed onto the drive shaft of the electric motor, and the worm is pressed into the elastic spring bush.

4. The worm drive as claimed in claim 1, wherein: the hub has an integrated key, the elastic spring bush defines a slot, and the elastic spring bush engages the hub via mating of the slot with the integrated key.

5. The worm drive as claimed in claim 1, wherein: the elastic spring bush comprises an outer ring and an inner ring, and the elastic spring bush further comprises a rubber-elastic material is arranged between the outer ring and the inner ring.

6. The worm drive as claimed in claim 1, wherein: the floating bearing includes an outer ring and an inner ring, and the floating bearing further includes a rubber-elastic material arranged between the outer ring and the inner ring.

Description

[0013] An exemplary embodiment is described with reference to the figures. More specifically:

[0014] FIG. 1 shows the worm drive according to the invention

[0015] FIG. 2 shows the hub of the coupling

[0016] FIG. 3 shows the elastic spring bush

[0017] FIG. 4 shows the assembled coupling with the hub and the spring bush

[0018] FIG. 1 shows the worm drive according to the invention. An electric motor 8 drives a worm 1. The worm 1 is in engagement with the worm gear 3. The drive shaft 5 of the electric motor 8 is connected to the worm 1 via a coupling, wherein the coupling comprises a hub 4 and an elastic spring bush 2. In this case, the hub 4 is pressed onto the drive shaft 5. The elastic spring bush 2 is pressed onto the worm 1. The hub 4 has an opening, into which the elastic spring bush 2 is pressed.

[0019] One side of the worm is then supported by the fixed bearing 6 on the drive shaft 5 of the electric motor 8. The other side of the worm is supported by the oval floating bearing 10. FIG. 1 shows the oval floating bearing 10 again in another, enlarged view. The oval shape allows vertical movements of the worm 1 for backlash compensation, while preventing lateral drifting of the worm 1.

[0020] For the preloading of the worm 1 onto the worm gear 3, the center distance a is reduced by a preloading dimension x during assembly.

[0021] FIG. 2 shows the hub 4 as an isolated component. On one side, the hub 4 has a bore, by means of which the hub 4 is pressed onto the drive shaft 5. On the other side, the hub 4 has a larger bore, into which the elastic spring bush 2 can be pressed. A key 9 can be arranged in this bore and is preferably formed integrally with the hub from a sintered material. The elastic spring bush 2 can then engage in this key 9 via a slot in order to obtain an additional means of ensuring the transmission of torque.

[0022] On the outer circumference of the hub 4, a recess is provided, which serves as an assembly aid, in that an assembly tool can engage there.

[0023] FIG. 3 illustrates the elastic spring bush 2 as an isolated component. In this case, a rubber-elastic material is arranged between an outer and an inner ring.

[0024] This is preferably produced by extrusion or vulcanization in the rings, resulting in a firm connection between the rubber-elastic material and the two rings. The spring bush 2 can thus damp axial and radial forces, transmit the torque and provide spring loading for the worm.

[0025] A slot 11 can be provided on the spring bush 2 and it engages in a key 9 in the hub 4. There is play between the key and the slot. The slot of the inner ring rests against the key only in the case of a corresponding overload. In this way, reliable torque transmission can be ensured.

[0026] FIG. 4 illustrates the complete coupling consisting of the hub 4 and the elastic spring bush 2. The elastic spring bush 2 is pressed into the hub 4. In the process, it engages via a slot in the key 9 of the hub 4.