Electric Power Steering Reducer Worm Shaft Elastic Support
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Solution Overview
Problem
Conventional electric power steering apparatus reducers experience issues with increased torque due to worm wheel moisture absorption, size changes, playing from worm and worm wheel wear, and rattle noise from backlash and reverse load inputs, particularly on rough roads.
Innovation Solution
The reducer incorporates a worm shaft bearing, a bearing holder, elastic rings and supports, and a supporting member made of a material with low moisture absorption, which provides elastic support to minimize torque increases, compensate for wear, and inhibit rattle noise by allowing the worm shaft to move with worm wheel expansion, using a plastic material with controlled expansion to counterbalance the worm wheel's expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional reducer design is used, then the structure is simple, but torque increases due to worm wheel moisture absorption and size changes
Solution Approach 1:
The patent makes the worm shaft position adjustable through elastic supports that allow the worm shaft to move dynamically in response to worm wheel expansion from moisture absorption. This dynamic adjustment prevents excessive torque increase by accommodating the size changes of the worm wheel without creating excessive resistance.
Solution Approach 2:
The patent changes the physical state and position parameters of the worm shaft by introducing elastic supports that enable positional adjustment. This allows the system to adapt to parameter changes in the worm wheel (size expansion from moisture absorption) without causing excessive torque increase.
2Ease of manufacture
If a conventional reducer design is used, then the manufacturing is simple, but playing occurs due to wear of worm and worm wheel
Solution Approach 1:
The elastic supports enable the worm shaft to dynamically adjust its position to compensate for wear between the worm and worm wheel. This dynamic compensation eliminates playing (looseness) in the steering operation without requiring complex manufacturing processes.
3Device complexity
If a conventional reducer design is used, then the structure is simple, but rattle noise occurs from backlash and reverse load input
Solution Approach 1:
The elastic supports provide dynamic positioning of the worm shaft that maintains proper engagement between the worm and worm wheel even under reverse load conditions. This dynamic adjustment prevents backlash and eliminates rattle noise without significantly complicating the reducer structure.
4Stability of the object's composition
If the worm shaft is rigidly fixed, then the position is stable, but torque increases when the worm wheel expands from moisture absorption
Solution Approach 1:
The patent replaces rigid fixation with elastic supports that provide controlled flexibility. The worm shaft remains relatively stable during normal operation but can move elastically to accommodate worm wheel expansion from moisture absorption, preventing excessive torque increase while maintaining operational stability.
Solution Approach 2:
The elastic supports act as flexible elements that allow the worm shaft to adapt to size changes in the worm wheel caused by moisture absorption. This flexibility prevents the torque increase that would occur with rigid fixation while maintaining adequate positional stability during operation.
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 design maintains the driver's steering feel and performance by minimizing torque increases, eliminating playing and rattle noise, and ensuring stable operation even under conditions of high humidity and temperature.
Implementation Method 1
an elastic ring intervened between the worm shaft bearing and the bearing holder; an elastic support provided in an inner circumferential surface of a gear housing
Implementation Method 2
a supporting member positioned between an outer circumferential surface of the bearing holder and the inner circumferential surface of the gear housing so as to support the end portion of the worm shaft, wherein the supporting member is made of a plastic material having the amount of moisture-absorption expansion lower than or equal to that of a plastic material used for the worm wheel
Implementation Method 3
the supporting member is made of a plastic material having the amount of moisture-absorption expansion lower than or equal to that of a plastic material used for the worm wheel
Data Source
AI summary
A reducer of an electric power steering apparatus, which can prevent the steering feel for a driver, and the performance from being reduced by minimizing an increase in the torque, caused by moisture absorption of a worm wheel, and a size change due to the moisture absorption, and also can eliminate the playing caused by wearing of a worm and the worm wheel, and inhibit the occurring of a rattle noise caused by a backlash and a reversely input load.