Electric Power Steering Reducer Rattle Noise Reduction
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Solution Overview
Problem
Conventional electric power steering apparatus reducers experience rattle noise due to increased backlash from wear between the worm and worm wheel, as well as impacts transferred from the road via the wheel and steering shaft, leading to an unpleasant driving experience.
Innovation Solution
The reducer incorporates a worm shaft with a ball-bearing mechanism between an inner and outer wheel, along with damper components to absorb vibrations and reduce backlash, utilizing a curved pivot surface to support rotation and pivot movement, and preloaded bearings to minimize noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional worm and worm wheel mechanism is used in the reducer, then the structure is simple and easy to manufacture, but backlash increases due to wear between the worm and worm wheel, causing rattle noise
Solution Approach 1:
A curved pivot surface is introduced as an intermediary element between the worm shaft bearing and the housing. This curved surface allows the worm shaft to perform pivot movement, absorbing impacts from the road and preventing direct transmission of vibrations that cause rattle noise, while maintaining the simplicity of the worm and worm wheel meshing mechanism
Solution Approach 2:
The curved inner wheel pivot surface is designed beforehand to accommodate pivot movement of the worm shaft. This pre-designed cushioning mechanism allows the worm shaft to naturally absorb impacts and vibrations before they can cause rattle noise, preventing the harmful effect rather than correcting it after occurrence
2Measurement precision
If the worm shaft is rigidly fixed to prevent movement, then positioning precision is improved, but impacts from the road are directly transmitted, causing rattle noise and discomfort
Solution Approach 1:
The worm shaft is transformed from a rigidly fixed component to a dynamically movable one through the curved pivot surface. The worm shaft can perform limited pivot movements within the curved surface, allowing it to dynamically absorb road impacts while maintaining sufficient positioning precision for normal operation. This dynamic adjustment prevents the rigid transmission of vibrations that cause rattle noise
3Object-generated harmful factors
If damping materials are added to reduce rattle noise, then noise reduction is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The curved pivot surface enables the worm shaft to self-absorb impacts through pivot movement. The system uses its own structural design rather than external damping materials to reduce rattle noise. The worm shaft's ability to pivot within the curved surface creates a self-cushioning effect that reduces noise without adding complex damping components
Solution Approach 2:
The curved inner wheel pivot surface uses a spherical or curved geometry to enable smooth pivot movement of the worm shaft. This curved design naturally guides the worm shaft's movement path, allowing it to absorb impacts effectively. The curvature itself serves as the damping mechanism, eliminating the need for additional damping materials and reducing device complexity
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 configuration effectively reduces rattle noise caused by backlash and impact, providing a more comfortable driving experience by minimizing resonance and absorbing vibrations through elastic materials and strategic bearing placement.
Implementation Method 1
a ball-bearing mechanism between an inner and outer wheel, along with damper components to absorb vibrations and reduce backlash
Implementation Method 2
utilizing a curved pivot surface to support rotation and pivot movement
Implementation Method 3
damper components to absorb vibrations and reduce backlash, providing a more comfortable driving experience by minimizing resonance and absorbing vibrations
Implementation Method 4
absorbing vibrations through elastic materials and strategic bearing placement
Data Source
AI summary
Disclosed is a reducer of an electric power steering apparatus. The disclosed reducer includes: a worm shaft bearing coupled with an end of the worm shaft's motor shaft coupling portion in such a manner that a ball coupled between an inner wheel and an outer wheel supports rotation of the worm shaft; and a first damper and a second damper which are tightly fitted in one side and the other side of the worm shaft bearing, respectively, while being insertedly-coupled with the worm shaft, so as to support the worm shaft and absorb a rattle noise transferred via the worm shaft, wherein each of the first damper and the second damper is provided with supporting plates at both sides thereof, and between the supporting plates, a damper made of an elastic material is coupled and formed. The reducer of the electric power steering apparatus reduces a rattle noise which occurs by an increase in backlash caused by abrasion of the worm and the worm wheel, or occurs by an impact transferred from a road via a wheel and the steering shaft, thereby providing a pleasant driving condition to the driver.