Disk Coupling for Electric Power Steering Motor Worm Deviation

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Solution Overview

Problem

Existing electric power steering systems face challenges with direct spline connections between the electric machine and worm, which fail to effectively compensate for radial and axial deviations, leading to abnormal noises and wear due to excessive drive gaps and improper meshing.

Innovation Solution

The proposed solution involves using multiple disks with through-holes and bolts between the electric machine and worm mounting flanges, allowing for radial and axial deviation compensation through elastic adjustment, thereby eliminating abnormal noises and wear.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If direct spline connection is used between electric machine shaft and worm shaft, then the structure is simple, but radial deviation and axial deviation cannot be compensated, resulting in excessive drive gap and abnormal noises

Engineering Contradiction:
Improveconnection structureVSAvoidmeshing accuracy
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

A disk is introduced as an intermediary component between the electric machine shaft and the worm shaft. The disk includes a first connection portion connected to the electric machine shaft and a second connection portion connected to the worm shaft, serving as a mediator that enables deviation compensation while maintaining structural simplicity

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The connection parameters between shafts are made adjustable through the disk structure. The disk allows radial and axial position parameters to be changed to compensate for deviations, transforming fixed parameters into adjustable ones to achieve proper meshing

Inventive Principle:
Principle #35Parameter changes

2Manufacturing precision

If plastic coupling connection is used between electric machine shaft and worm shaft, then radial deviation can be compensated to a certain extent, but axial deviation cannot be compensated

Engineering Contradiction:
Improveradial alignmentVSAvoiddeviation compensation capability
Core Design Contradiction:
Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The disk structure performs multiple functions simultaneously: it connects the two shafts, compensates for radial deviation through its radial positioning capability, and compensates for axial deviation through its axial positioning capability. This multi-functional design overcomes the limitation of plastic couplings that only handle radial deviation

Inventive Principle:
Principle #6Universality (Multi-functionality)

3Reliability

If disk is provided between electric machine shaft and worm shaft, then deviation compensation is improved, but the structure becomes more complex

Engineering Contradiction:
Improvedeviation compensationVSAvoidconnection structure
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The connection structure is segmented into distinct functional portions: the disk body and the first connection portion (to electric machine shaft) and second connection portion (to worm shaft). This segmentation allows each portion to be optimized independently while maintaining overall simplicity through modular design

Inventive Principle:
Principle #1Segmentation

Data Source

PatentEP3395649B1Motor and worm connection device for electric power steering system
Publication Date: 2021.04.14 THYSSENKRUPP PRESTA SHANGHAI
  • EP3395649B1 patent drawingFigure 1

AI summary

The present invention provides an apparatus for connecting an electric machine and a worm for an electric power steering system, comprising an electric machine (1), an electric machine shaft (2) connected to the electric machine (1), and a worm (3), wherein an end of the electric machine shaft (2) is provided with a first mounting flange (5), and an end of the worm (3) is provided with a second mounting flange (6). The apparatus for connecting an electric machine and a worm is characterized in that at least one disk (4) is provided between the first mounting flange (5) of the electric machine shaft (2) and the second mounting flange (6) of the worm (3). The apparatus for connecting an electric machine and a worm for an electric power steering system provided in the present invention is structurally simple, and at the same time as transferring electric machine torque with high efficiency, can effectively compensate for radial deviation and axial deviation between the electric machine shaft and a worm shaft.