Compact power steering system

Patent metadata

Field	Value
Publication number	US-2021016821-A1
Application number	US-202016928325-A
Country	US
Kind code	A1
Filing date	Jul 14, 2020
Priority date	Jul 18, 2019
Publication date	Jan 21, 2021
Grant date	—

Abstract

A compact power steering system is suitable for small vehicles. A torque sensor on a steering shaft detects operator intention to turn. In response, a motor provides torque to assistance in rotating the steering shaft. A strain wave gear set multiplies the motor torque. A coupler having a torsional isolator links the gearbox output to the steering shaft.

First claim

What is claimed is:

1 . A power steering system comprising:
a central shaft; a motor having a rotor supported for rotation about the shaft; a first coupling element fixed to the shaft and having a first set of external teeth; a second coupling element having internal teeth interspersed with the external teeth; a ring having compressible, resilient prongs extending between the internal teeth and the external teeth; and a gear set drivably connecting the rotor to the second coupling element such that the second coupling element rotates slower than the rotor.

2 . The power steering system of claim 1 wherein the gear set is a strain wave gear set comprising:
a fixed housing having a second set of internal teeth;
an eccentric inner ring fixed to the rotor; and
a flexible band supported by the eccentric inner ring by a bearing and having a second set of external teeth that mesh in at least one circumferential region with the second set of internal teeth.

3 . The power steering system of claim 2 wherein the strain wave gear set further comprises a third set of internal teeth on the second coupling element which mesh in the at least one circumferential region with the second set of external teeth.

4 . The power steering system of claim 3 wherein a number of teeth in the third set of internal teeth is less than a number of teeth in the second set of internal teeth.

5 . The power steering system of claim 3 wherein a number of teeth in the third set of internal teeth differs by exactly two from a number of teeth in the second set of internal teeth.

6 . A power steering system comprising:
a central shaft; a motor having a rotor supported for rotation about the shaft; a fixed housing having a first set of internal teeth; an eccentric inner ring fixed to the rotor; and a flexible band supported by the eccentric inner ring by a bearing and having a first set of external teeth that mesh in at least one circumferential region with the first set of internal teeth.

7 . The power steering system of claim 6 further comprising a coupler having a coupler input and a coupler output separated by a compressible, resilient element, the coupler output fixed to the shaft, the coupler input having a second set of internal teeth which mesh in the at least one circumferential region with the external teeth.

8 . The power steering system of claim 7 wherein a number of teeth in the second set of internal teeth is less than a number of teeth in the first set of internal teeth.

9 . The power steering system of claim 7 wherein a number of teeth in the second set of internal teeth differs by exactly two from a number of teeth in the first set of internal teeth.

10 . The power steering system of claim 7 wherein:
the coupler output has a second set of external teeth;
the coupler input has a third set of internal teeth interspersed with the second set of external teeth; and
the compressible, resilient element is a ring having prongs that extending between the teeth of the third set of internal teeth and the teeth of the second set of external teeth.

11 . A method of assembling a power steering system comprising:
fixing a first coupling element to a shaft, the first coupling element having a set of external teeth; sliding a torsional isolator over the first coupling element, the torsional isolator having a ring and a set of compressible, resilient prongs; and sliding a second coupling element over the torsional isolator, the second coupling element having internal teeth, such that the prongs extend between the internal teeth and the external teeth.

12 . The method of claim 11 further comprising drivably connecting a rotor of an electric motor to the second coupling element.

13 . The method of claim 12 wherein drivably connecting the rotor to the second coupling element comprises providing a speed reduction gearbox.

14 . The method of claim 13 wherein the speed reduction gearbox is a strain wave gear set.

Assignees

• Schaeffler Technologies Ag

Inventors

• Vazquez Andre
• Hooker Craig

Classifications

• B62D5/043 Primary

  characterised by clutch means between driving element, e.g. motor, and driven element, e.g. steering column or steering gear · CPC title

• B62D5/0415 Primary

  the axes being coaxial · CPC title

• F16D3/68

  the elements being made of rubber or similar material · CPC title

• F16H49/001

  Wave gearings, e.g. harmonic drive transmissions · CPC title