Low Axial Play Drive System for Vehicle Mirror
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Solution Overview
Problem
Existing drive systems for remotely adjusting external vehicle mirrors suffer from rotational position uncertainty due to backlash and axial play, leading to uncontrolled movement during vehicle vibrations, and transmit thrust loads to the front and rear walls of the drive housing, requiring reinforcement.
Innovation Solution
A drive system with a motor coupled to a shaft within a rigid drive housing, featuring a shaft retainer and thrust washers to eliminate axial play and channel thrust away from the housing walls, using a worm drive assembly with no separation between components to ensure engagement and prevent play.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional drive system with gear mesh is used, then the mirror can be adjusted remotely, but rotational position uncertainty occurs due to backlash and axial play
Solution Approach 1:
The patent replaces the conventional gear mesh mechanism with a rack and pinion mechanism. The rack is rigidly attached to the drive housing and engages with the pinion gear, eliminating backlash and axial play between meshing gears. This mechanical substitution provides precise rotational positioning and stability under vibration conditions.
2Reliability
If the drive gear is made as a worm gear to prevent back driving, then one-way rotation control is achieved, but thrust loads are transmitted to the housing walls requiring reinforcement
Solution Approach 1:
The patent extracts the thrust load path from the housing walls by introducing a dedicated thrust bearing at the pinion shaft. The thrust bearing absorbs and channels the axial forces generated by the worm gear mechanism, preventing these loads from being transmitted to the front and rear housing walls. This eliminates the need for reinforcement of the housing walls while maintaining one-way rotation control.
3Power
If multiple gear stages are used to achieve the required torque multiplication, then sufficient driving torque is obtained, but the device complexity increases
Solution Approach 1:
The patent combines multiple gear stages into a single integrated pinion gear that engages with the rack. The pinion gear incorporates both the worm drive functionality for torque multiplication and the directional control features, eliminating the need for separate gear stages. This merging reduces device complexity while maintaining sufficient driving torque through the lever arm of the rack mechanism.
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 rotational uncertainty and eliminates the need for reinforcement of the housing walls, providing stable and precise mirror adjustment with reduced manufacturing costs.
Implementation Method 1
The drive gear 18 is typically a worm, but may take a different form depending on the geometry of the axis gear 16
Data Source
AI summary
A drive system for rotating an assembly, such as an external vehicle mirror housing, about an axis is provided with a drive housing containing a worm drive assembly coupled to an axis gear mounted about the axis. The worm drive assembly is rotated by an electric motor. The axis gear is stationary with respect to the axis, such that rotation of the worm drive assembly will cause it to travel about the axis gear. Such movement of the worm drive assembly will cause the drive housing and the associated external vehicle mirror housing to rotate about the axis. Thrust transmitted to the worm drive assembly is transmitted to a central portion of the drive housing by a shaft retainer associated with the worm drive assembly. Play between the axis gear and the worm drive assembly is prevented by eliminating separation between adjacent components of the worm drive assembly.