Electric Vehicle View Device Worm Shaft Play Prevention
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Solution Overview
Problem
Conventional electric retractable vehicle view devices, such as mirrors, experience abnormal sound generation due to radial movement or inclination of the worm relative to the motor shaft, caused by the radial gap between the motor shaft and the worm, leading to contact between the worm's outer surface and the bearing recess.
Innovation Solution
A radial gap is formed between the distal end of the worm and the bearing recess, sized to prevent contact during rotation, and the worm wheel's position is set to minimize inclination, ensuring stable rotation and avoiding abnormal sound by maintaining the worm's axial alignment with the motor shaft.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a radial gap is provided between the motor shaft and the center hole of the worm to enable rotation and cancel sticking, then the worm can rotate relative to the motor shaft and cancel stuck state, but the worm may be moved or inclined radially relative to the motor shaft causing instable operating sound
Solution Approach 1:
A cylindrical play prevention member is introduced as an intermediary component between the worm and the case. This member has a play prevention outer peripheral surface that contacts the inner peripheral surface of the case, preventing radial movement of the worm while allowing the necessary rotational play between the motor shaft and worm center hole to cancel sticking.
Solution Approach 2:
The support structure is segmented into multiple functional elements: the motor shaft with radial gap to the worm center hole for rotational play, the play prevention member with its outer peripheral surface contacting the case, and the worm positioned between these elements. This segmentation allows each component to fulfill its specific function - the motor shaft provides rotation, the play prevention member prevents radial movement, and the worm transmits motion.
2Stability of the object's composition
If the worm is supported by a bearing recess to stabilize its position, then the worm's axial center should be stabilized, but contact between the worm's outer surface and the bearing recess during rotation generates abnormal sound
Solution Approach 1:
The play prevention member acts as an intermediary that bears the radial load from the worm to the case. Instead of the worm's outer surface directly contacting the bearing recess, the play prevention member's outer peripheral surface contacts the case's inner peripheral surface, mediating the support function and eliminating direct contact between the rotating worm and the bearing surface.
Solution Approach 2:
The radial support function is extracted from the bearing recess and transferred to the play prevention member. The bearing recess no longer needs to provide radial support, eliminating the source of abnormal sound, while the play prevention member assumes this support function through its contact with the case.
Data Source
AI summary
This invention intends to prevent generation of abnormal sound. A motor shaft is inserted in a center hole of a worm and fitted in the center hole in a direction around an axis of the worm. A distal end of the worm is received in a bearing recess. A worm wheel engages with the worm. A radial gap and rotational play are formed between the motor shaft and the center hole of the worm. A radial gap is formed between the distal end of the worm and the bearing recess. The gap between the distal end of the worm and the bearing recess is formed so as to have a size that prevents an outer circumferential surface of the distal end of the worm and an inner circumferential surface of the bearing recess from coming into contact with each other when the worm is rotating.