Electric Power Steering Worm Shaft Backlash Elimination
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Solution Overview
Problem
Conventional electric power steering systems face complications due to the need for backlash removal between the worm shaft and worm wheel, leading to rattle issues during vehicle travel, and existing solutions complicate the structure with additional support mechanisms.
Innovation Solution
An electric power steering system with a simplified structure, utilizing a joint with a rotational element that press-fits the worm shaft's first end portion and includes an elastic body between the bearing's inner ring and flange to urge the worm shaft axially toward the electric motor, maintaining torque transmission and reducing backlash.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an elastic body is supported between a nut or circular plate and an inner ring of the bearing to remove backlash, then backlash is eliminated, but the device complexity increases due to additional support mechanisms
Solution Approach 1:
The patent combines the elastic body support function with the existing joint structure. The elastic body is integrated between the joint body and the bearing inner ring, merging the backlash elimination function into the existing torque transmission path rather than adding separate support mechanisms. This reduces device complexity while maintaining effective backlash elimination.
Solution Approach 2:
The joint structure serves multiple functions: it transmits torque between the worm shaft and rotary shaft, supports the elastic body for backlash elimination, and provides axial positioning. By making the joint multi-functional, the patent eliminates the need for separate dedicated support structures, thereby reducing overall device complexity.
2Power
If a joint mechanism is added to connect the worm shaft with the rotary shaft for torque transmission, then torque transmission is enabled, but the device complexity increases
Solution Approach 1:
The patent merges the torque transmission function with the elastic body support function in a single integrated joint structure. The joint body simultaneously transmits torque and supports the elastic body that eliminates backlash, eliminating the need for separate mechanisms and reducing overall device complexity.
Solution Approach 2:
The joint structure is designed as a multi-functional component that performs torque transmission, elastic body support, and axial positioning simultaneously. This universal design approach enables torque transmission without adding excessive complexity, as the same structure fulfills multiple critical functions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively eliminates backlash and simplifies the system structure, improving steering feel by allowing the worm shaft to oscillate smoothly and maintaining zero backlash, while reducing axial space and enhancing accuracy in axial load application.
Implementation Method 1
an elastic body that is provided between an inner ring of the bearing and the flange, and urges the worm shaft in the axial direction toward the electric motor through the rotational element
Implementation Method 2
a joint that includes a rotational element that has a boss into which the first end portion of the worm shaft is press-fitted and a flange extending radially from the boss, the joint connecting the first end portion of the worm shaft with the rotary shaft so that torque is transmittable
Data Source
AI summary
An electric power steering system includes a joint that connects a rotary shaft of an electric motor with a worm shaft of a speed reducer. The joint includes a first rotational element that has a boss into which a first end portion of the worm shaft is press-fitted, and a flange extending radially from the boss. The first bearing is held by a housing and supports the first end portion so that the first end portion is rotatable and movable in an axial direction. A first elastic body, which urges the worm shaft in the axial direction toward the electric motor through the first rotational element, is provided between an inner ring of the first bearing and the flange.