Lead Screw Travel Stop Assembly for Steer-by-Wire Rotation Limits
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Solution Overview
Problem
In vehicle technology, hand-wheel actuators (HWA) and road-wheel actuators (RWA) lack effective mechanisms to prevent over-rotation of the hand-wheel, leading to potential damage to components like the clock spring and air bag coil due to the absence of mechanical linkages that limit rotation.
Innovation Solution
A travel stop assembly comprising a rotatable shaft with a lead screw and nut in threaded engagement, featuring stop pins that limit rotation and prevent locking, allowing for controlled axial movement and rotation of the hand-wheel shaft, thereby preventing over-rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If direct mechanical linkage is used between hand-wheel and tires, then rotation of hand-wheel is limited preventing damage to components, but the complexity of mechanical linkages increases
Solution Approach 1:
The patent extracts the rotation limiting function from the complex mechanical linkage system and implements it through a separate travel stop assembly that couples to the lead screw. This allows the HWA to operate without direct mechanical linkage while still providing rotation limits through the stop pins and stop arms mechanism.
Solution Approach 2:
The travel stop assembly acts as an intermediary between the HWA and the rotation control function. The stop pins extend from the lead screw and engage with stop arms to provide rotation limiting without requiring direct mechanical linkage between the hand-wheel and tires.
2Reliability
If stop pins are positioned on lead screw to limit rotation, then over-rotation damage is prevented, but the risk of nut locking to lead screw increases
Solution Approach 1:
The stop pins are designed to engage the stop arms before the nut can fully lock to the lead screw threads. By positioning the stop pins at specific locations on the lead screw, the system allows partial rotation travel but prevents excessive rotation that would cause nut locking, thus providing protection through controlled limitation.
3Ease of operation
If multiple moving parts are used in travel stop mechanism, then rotation control is achieved, but noise and vibration increase
Solution Approach 1:
The patent employs a channel structure that guides the stop arms and provides controlled movement. The channel constrains the motion paths of the stop arms and stop pins, reducing unwanted vibrations and noise while maintaining the rotation control function. The structured guidance minimizes chaotic movements of multiple parts.
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 travel stop assembly effectively limits hand-wheel rotation, preventing damage to components by providing a 'hard stop' mechanism that is adjustable and cost-effective, while reducing noise and vibration by minimizing moving parts.
Implementation Method 1
A lead screw may extend along the axis and be operatively engaged, and rotatable, with the shaft about the axis. A nut may be in threaded engagement with the lead screw and axially movable along a length of the lead screw upon rotation of the lead screw.
Data Source
AI summary
The present disclosure related to a travel stop assembly for preventing rotation, and undesired locking, of a shaft. The travel stop assembly may comprise a shaft that extends along an axis and is rotatable about the axis. A lead screw may extend along the axis and be operatively engaged, and rotatable, with the shaft about the axis. A nut may be in threaded engagement with the lead screw and axially movable along a length of the lead screw upon rotation of the lead screw. At least one stop pin may operatively engaged the lead screw and the at least one stop pin may extend from the lead screw perpendicularly relative to the axis. The stop pin may be positioned on the lead screw to stop rotation of the lead screw and the stop pin may prevent locking of the nut to the lead screw.