Electric Power Steering Reducer Damping for Rattle Noise
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Solution Overview
Problem
Conventional electric power steering apparatuses experience rattle noise and uncomfortable steering due to backlash, friction, and wear between the worm and worm wheel, as well as increased rotational resistance and catching phenomena, which affect the driver's steering experience.
Innovation Solution
The introduction of a reducer with worm shaft bearings and a housing or plug damper system that provides axial resilient support to absorb vibrations and noise, reducing rotational resistance and improving the steering feel by mitigating the effects of friction and wear between the worm shaft and worm wheel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional reducer structure with worm and worm wheel is used, then power transmission function is achieved, but rattle noise and backlash occur due to friction and wear
Solution Approach 1:
A damper is installed between the worm shaft bearing outer race and the gear housing to provide beforehand cushioning against impacts and vibrations. The damper absorbs shocks from road surfaces and prevents them from transmitting through the worm shaft bearing, thereby reducing rattle noise and backlash while maintaining power transmission function.
Solution Approach 2:
The damper acts as an intermediary element between the worm shaft bearing and the gear housing. It mediates the transmission of vibrations and impacts by absorbing them, thereby preventing direct contact and collision between the worm and worm wheel that would otherwise generate rattle noise and backlash.
2Ease of operation
If worm shaft bearings are installed to support the worm shaft, then rotational support is provided, but catching phenomenon and rotational resistance increase due to friction and wear
Solution Approach 1:
The damper provides beforehand cushioning to the worm shaft bearing by absorbing impacts and vibrations before they reach the bearing. This reduces the friction and wear between the bearing components, thereby decreasing rotational resistance and preventing catching phenomenon while maintaining rotational support.
Solution Approach 2:
The damper converts harmful impacts and vibrations from road surfaces into beneficial cushioning effects. By absorbing these shocks, the damper protects the worm shaft bearing from excessive friction and wear, thereby reducing rotational resistance and preventing catching phenomenon.
3Stability of the object's composition
If the worm shaft bearing is fixed rigidly to the gear housing, then stable support is achieved, but vibrations and noise from road impacts are transmitted
Solution Approach 1:
The damper serves as an intermediary between the worm shaft bearing and the gear housing. It provides stable support while simultaneously absorbing vibrations and noise from road impacts, preventing their transmission to the gear housing and improving overall system stability.
Solution Approach 2:
The damper changes the mechanical parameters of the bearing support system by introducing vibration isolation characteristics. It transforms the rigid connection into a compliant one that can absorb vibrations and noise while maintaining the necessary stability for power transmission.
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
The solution effectively reduces rattle noise and enhances the steering experience by lowering noise levels and improving the operational feel, with noise reduction by 3 to 5 dB compared to conventional systems, allowing for smoother and more comfortable steering operations.
Implementation Method 1
a housing damper coupled to one of the worm shaft bearings between an end of the worm shaft opposite to a connecting portion of a motor shaft and an inner wall of the gear housing to support an outer race of the worm shaft bearing with an axial resilient force
Implementation Method 2
configured to absorb vibrations and noise generated by friction and wear during operations of a worm shaft and a worm wheel
Implementation Method 3
a plug damper coupled to one of the worm shaft bearings between an end of the worm shaft on a side of a connecting portion of a motor shaft and a plug bolt coupled to the worm shaft to support an outer race of the worm shaft bearing with an axial resilient force
Implementation Method 4
configured to absorb vibrations and noise generated by friction and wear during operations of a worm shaft and a worm wheel
Data Source
AI summary
A reducer of an electric power steering apparatus is disclosed. It reduces rattle noise generated by a backlash due to friction and wear of a worm and a worm wheel or an impact transmitted from a road surface through a wheel and a steering shaft and enhances a steering feeling of a driver by improving the catching phenomenon and rotational resistance generated between a worm shaft and a worm shaft bearing.