Worm shaft articulation control method for eps worm gears

Patent metadata

Field	Value
Publication number	US-2020102002-A1
Application number	US-201916578452-A
Country	US
Kind code	A1
Filing date	Sep 23, 2019
Priority date	Sep 27, 2018
Publication date	Apr 2, 2020
Grant date	—

Abstract

An electric power steering system with a worm gear includes a worm shaft and a worm wheel, wherein an electric motor is associated with the worm shaft, which is connected to the worm shaft in a force-transmitting manner. A bearing element, arranged on the worm shaft at the end of the worm shaft facing away from the electric motor, is received in a guide bush, wherein the guide bush has, on its circumferential side, a passage opening. It is provided a pre-tensioning device comprising a spring-loaded actuator element extending through the passage opening of the guide bush and acting on the worm shaft in the direction of the worm wheel with a defined pre-tensioning force (K), wherein the pre-tensioning device comprises a limiting device which is adapted to limit a pivoting movement that displaces the worm wheel away from the worm shaft. Furthermore, it is proposed a method for the production of steering systems and a test system for performing the method.

First claim

What is claimed:

1 . An electric power steering system, comprising:
a worm gear comprising a worm shaft and a worm wheel, wherein an electric motor is associated with the worm shaft, which is connected to the worm shaft in a force-transmitting manner. a bearing element, arranged on the worm shaft, at the end of the worm shaft facing away from the electric motor, a guide bush, in which the bearing element is received, wherein the guide bush has, on its circumferential side, a passage opening, and a pre-tensioning device comprising a spring-loaded actuator element extending through the passage opening of the guide bush and acting on the worm shaft in the direction of the worm wheel with a defined pre-tensioning force, wherein the pre-tensioning device comprises a limiting device, which is adapted to limit a pivoting movement that displaces the worm wheel away from the worm shaft.

2 . The electric power steering system according to claim 1 wherein the limiting device and the actuator element each comprise an abutment, wherein the abutments in mutual contact limit the pivoting movement that displaces the worm wheel away from the worm shaft.

3 . The electric power steering system according to claim 2 wherein a distance between the abutments is essentially equal to the deflection of the worm shaft due to the defined pre-tensioning force.

4 . The electric power steering system according to claim 3 wherein the distance between the abutments is set based on one of an ambient temperature or an ambient humidity, in particular, based on one of an expected ambient temperature profile or an expected ambient humidity profile.

5 . The electric power steering system according to claim 4 wherein the worm wheel consists of a plastic material, wherein a relative humidity of the plastic material is acclimatized to an expected ambient humidity, in particular, to the expected ambient humidity profile.

6 . The electric power steering system according to claim 2 wherein the limiting device comprises a clearance adjusting device, by means of which the abutment of the limiting device is adjustable.

7 . The electric power steering system according to claim 2 wherein the pre-tensioning device comprises a force adjusting device by means of which the pre-tensioning force (K) is adjustable.

8 . The electric power steering system according to claim 2 wherein the defined pre-tensioning force (K) is between 8 N and 12 N, preferably in about 10 N.

9 . The electric power steering system according to claim 2 wherein it is provided at least one damping device acting radially on the bearing element, in particular wherein the damping device acts bidirectional radially on the bearing element.

10 . The electric power steering system according to claim 2 wherein the guide bush is the damping device.

11 . The electric power steering system according to claim 10 wherein the damping device is formed as a viscous damper.

12 . A method for the production of steering systems comprising the steps of:
Adjusting the pre-tensioning force (K) to a predefined value; Measuring the radial clearance (z S ) of the worm shaft; Adjusting the radial clearance (z S ) to the predefined target value (z Z ) for the radial clearance (z S ); and Repeating the previous two steps until the target value (z Z ) for the radial clearance (z S ) is achieved.

13 . The method according to claim 12 wherein the target value (z Z ) for the radial clearance (z S ) is set, based on an ambient temperature and/or an ambient humidity, in particular based on an expected ambient temperature profile and/or an expected ambient humidity profile.

Assignees

• Trw Automotive Gmbh

Inventors

• Kirschstein Stefan
• Müller Toni

Classifications

• F16H2057/127

  using springs · CPC title

• F16H57/021

  Shaft support structures, e.g. partition walls, bearing eyes, casing walls or covers with bearings · CPC title

• F16H2057/0222

  Lateral adjustment · CPC title

• F16H2057/0213

  Support of worm gear shafts · CPC title

• B62D5/0409 Primary

  Electric motor acting on the steering column · CPC title