Variable Travel Stop for Worm Gear Durability
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Solution Overview
Problem
Worm gear durability is compromised due to high loads applied at end-of-travel positions, leading to fatigue, particularly when driven in opposite directions, which existing control systems fail to effectively manage, resulting in reduced lifespan and potential over-travel issues in machines like electric power steering systems.
Innovation Solution
A control system that includes a processor and memory to rotate a driveshaft, drive a worm gear, and stop the motor at predetermined stop positions, allowing for the worm gear to change stop positions to distribute wear and torque more evenly, thereby reducing stress on the worm gear teeth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the motor stops the worm gear at fixed end-of-travel positions, then the control system is simple to implement, but the worm gear teeth experience concentrated wear and reduced durability
Solution Approach 1:
The patent applies the dynamics principle by making the stop positions variable rather than fixed. The controller dynamically adjusts the stop positions within the operating range of the worm gear, preventing the same teeth from consistently engaging at end-of-travel positions. This dynamic adjustment redistributes wear across multiple teeth, improving durability without requiring fundamental changes to the mechanical structure.
Solution Approach 2:
The patent implements parameter changes by modifying the stop position parameters during operation. Instead of using fixed stop positions, the controller varies the stop positions within acceptable operational limits, changing the engagement points of the worm gear teeth. This parameter variation effectively reduces concentrated wear while maintaining full steering functionality.
2Ease of operation
If the worm gear operates through the full range of travel including end positions, then the steering system maintains complete functionality, but the worm gear teeth experience high loads and premature wear
Solution Approach 1:
The system dynamically adjusts stop positions to prevent excessive wear while maintaining full steering travel capability. By varying the stop positions within the operational range rather than fixing them at extreme ends, the system preserves complete steering functionality while redistributing mechanical loads across different teeth over time.
Solution Approach 2:
The patent employs periodic action by alternating between different stop positions during successive steering operations. This periodic variation ensures that no single set of teeth is consistently subjected to maximum end-of-travel loads, thereby extending the overall lifespan of the worm gear while maintaining full operational range.
Data Source
AI summary
Technical solutions are described for controlling operation of a motor using a controller to: energize the motor to rotate driveshaft and a worm; drive a worm gear by the worm; stop the motor from rotating the driveshaft in response to the worm gear rotating to a given one of a plurality of first stop positions; and change the given one of the first stop positions to another one of the first stop positions. A method for controlling a machine comprises: rotating a driveshaft by a motor; driving a worm gear by a worm to cause the worm gear to rotate; stopping the motor from rotating the driveshaft in response to the worm gear rotating to a given one of a plurality of first stop positions; and changing the given one of the first stop positions to another one of the first stop positions.