Worm Gear Center Adjuster for Steering Backlash Suppression
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Solution Overview
Problem
Conventional steering devices experience backlash and noise due to changing reaction force directions in worm gears, especially when the worm shaft is not right-angled, leading to torsional misalignment and increased backlash between the worm shaft and worm wheel during rotation direction changes.
Innovation Solution
A steering device with a center adjuster mechanism where a bearing is biased by a wire spring in a direction inclined relative to the gear engagement, allowing the worm shaft to be adjusted to maintain proper engagement with the worm wheel, reducing backlash and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the worm shaft and worm wheel are engaged at a non-right angle, then the steering device can accommodate torsional misalignment, but backlash and noise occur during rotation direction changes
Solution Approach 1:
The bearing supporting the worm shaft is made movable along the worm shaft axis through a center adjuster mechanism. This dynamic adjustment capability allows the bearing position to be optimized for different rotation directions, eliminating backlash while accommodating torsional misalignment. The bearing can dynamically adapt its position to maintain optimal engagement between worm shaft and worm wheel teeth.
Solution Approach 2:
A biasing member (spring) is pre-installed to apply a biasing force to the bearing, preliminarily positioning it in a state that reduces backlash. This preliminary action ensures that the bearing is always pushed toward the optimal engagement position before rotation occurs, preventing backlash from occurring in the first place during direction changes.
2Manufacturing precision
If a spring is used to bias the bearing toward the worm wheel, then engagement state is adjusted, but backlash occurs during rotation direction switching
Solution Approach 1:
The biasing force from the spring is applied at an angle rather than directly along the worm shaft axis. This angular application of force creates a component that presses the bearing teeth together while still allowing axial adjustment. By changing the dimension of force application from purely axial to angular, the system achieves both precise engagement and backlash elimination.
Solution Approach 2:
The center adjuster mechanism allows asymmetric adjustment of the bearing position along the worm shaft axis, enabling different optimal positions for different rotation directions. This asymmetric capability permits the system to compensate for the directional nature of backlash, optimizing engagement for both clockwise and counter-clockwise rotations independently.
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 suppresses backlash and noise by ensuring consistent engagement between the worm shaft and worm wheel, improving steering precision and reducing wear, thereby enhancing the overall performance and reliability of the steering system.
Implementation Method 1
a bearing supporting a tip of the worm shaft is biased by a wire spring in a direction inclined with respect to a direction of gear engagement between the worm shaft and the worm wheel
Data Source
AI summary
A steering device includes: a worm wheel linked to a steering shaft; a worm shaft engaging with the worm wheel; an electric motor supplying rotational force to the worm shaft and including a motor shaft connected to a first end of the worm shaft; a gear housing containing the worm wheel and the worm shaft; a bearing supporting a second end of the worm shaft; a center adjuster that is contained in the gear housing and includes a holder and a collar, wherein the collar is disposed in the holder and retains the bearing so as to allow the bearing to move with respect to the holder in a gear engagement direction; and a biasing member disposed in the center adjuster and structured to bias the bearing in a direction inclined with respect to the gear engagement direction.