Hand-Wheel Stop Gear Assembly for Steer-by-Wire Over-Rotation
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Solution Overview
Problem
In steer-by-wire systems, the hand-wheel is free to rotate excessively, potentially damaging components like the clock spring, as there is no mechanical linkage to limit its rotation, unlike in traditional vehicles with direct mechanical linkages between the steering wheel and tires.
Innovation Solution
A hand-wheel actuator assembly with a housing, drive gear, and stop gear that allows more than 360 degrees of rotation while providing a 'hard stop' through engagement of drive gear teeth with stop gear teeth, preventing excessive rotation and incorporating features like a wave spring and elastomeric members to minimize noise and friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the hand-wheel is made free to rotate in steer-by-wire systems, then the steering operation flexibility is improved, but the risk of component damage from excessive rotation increases
Solution Approach 1:
The stop gear is designed to pivot between a retracted position (allowing free rotation) and an engaged position (providing hard stop). This dynamic positioning allows the system to switch between flexible operation and protective constraint based on operational needs, resolving the contradiction between ease of operation and reliability
Solution Approach 2:
The stop gear acts as an intermediary mechanism between the drive gear and the housing. It selectively engages to provide mechanical constraint when needed, while remaining passive during normal operation. This intermediary component enables the system to have both freedom of movement and protective limitation without compromising either aspect
2Reliability
If a mechanical stop is added to limit hand-wheel rotation, then component protection is improved, but the device complexity increases
Solution Approach 1:
The stop gear is integrated with the drive gear through direct meshing engagement of their teeth. The stop gear's pivot mounting combines the limiting function with the existing rotational mechanism, eliminating the need for separate complex limiting structures. This merging approach provides component protection while minimizing additional complexity
Solution Approach 2:
The stop gear automatically pivots into engagement when the drive gear approaches the rotation limit, and disengages when rotation is reversed. This self-actuating mechanism eliminates the need for external control systems, sensors, or actuators, providing reliable component protection with minimal added complexity
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 provides a cost-effective, easy-to-assemble, low-friction, and noise-minimizing hand-wheel actuator that can handle high torques (100 Nm to 250 Nm) with a 'hard stop' mechanism, preventing damage from excessive rotation and enhancing the reliability of steer-by-wire systems.
Implementation Method 1
incorporating features like a wave spring and elastomeric members to minimize noise and friction
Implementation Method 2
incorporating features like a wave spring and elastomeric members to minimize noise and friction
Data Source
AI summary
A hand-wheel actuator for preventing over rotation of a hand-wheel shaft. The hand-wheel actuator comprises a housing that defines an opening aligned about an axis. The hand-wheel shaft extends along and is rotatable about the axis. A drive gear is rotationally coupled to the hand-wheel shaft, wherein the drive gear is at least partially disposed in the opening and includes a drive gear tooth. A stop gear is coupled to the housing and includes a plurality of stop gear teeth for engagement with the drive gear tooth and prevents rotation of the drive gear over a predetermined threshold.