Zero-Lash Position Sensor Wheel for Ball Screw Feedback
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Solution Overview
Problem
Existing position sensors in vehicular systems face challenges in packaging and robustness, particularly in providing precise position control and feedback in steering systems, where zero-lash and precise angular resolution are critical.
Innovation Solution
A position sensor design incorporating an angle sensor, sensor shaft, and sensor wheel with a torsionally preloaded mechanism using a leg spring, which couples the first and second wheel-halves to eliminate gear-lash and provide precise rotational feedback, integrated with a ball screw drive for accurate position sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a position sensor is designed for precise angular resolution and zero-lash in steering systems, then measurement precision is improved, but device complexity increases due to the torsionally preloaded mechanism with multiple wheel-halves and leg springs
Solution Approach 1:
The sensor wheel is divided into two separate wheel-halves (first wheel-half and second wheel-half) that can rotate relative to each other. This segmentation allows the implementation of a torsionally preloaded mechanism where each wheel-half can be independently positioned and loaded, enabling zero-lash measurement while maintaining manageable structural complexity through modular design
Solution Approach 2:
The leg spring is pre-loaded in a torsional direction before operation to create a predetermined force that maintains constant contact between the wheel-halves and the sensor shaft. This preliminary action ensures zero-lash conditions are already established during assembly, eliminating the need for complex real-time adjustment mechanisms and simplifying the overall device structure
2Reliability
If a position sensor incorporates a torsionally preloaded mechanism with leg springs to eliminate gear-lash, then reliability is improved, but manufacturing precision requirements increase due to the precise alignment of multiple components
Solution Approach 1:
The leg spring is designed to automatically self-align the wheel-halves to the sensor shaft through its torsional preload force. The spring's elastic deformation capability allows it to compensate for minor manufacturing tolerances and automatically establish the correct geometric relationship between components during assembly, reducing the need for high-precision manufacturing while maintaining reliability
Solution Approach 2:
The leg spring's torsional stiffness and preload force are carefully selected to provide optimal balance between eliminating gear-lash and accommodating manufacturing tolerances. By adjusting the spring parameters (stiffness, preload, geometry), the system can maintain reliable zero-lash operation even with moderate manufacturing precision, as the spring parameters compensate for dimensional variations
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 achieves zero-lash and precise angular resolution, enhancing the accuracy of position sensing and control in steering systems, thereby improving the robustness and reliability of vehicular position sensors.
Implementation Method 1
the second wheel-half is torsionally preloaded to the first wheel-half through the leg spring
Data Source
AI summary
A position sensor may include an angle sensor, sensor shaft, and sensor wheel. The sensor wheel may include a first wheel-half, a second wheel-half, and a leg spring. The angle sensor may sense the rotation of the sensor shaft. The first wheel-half may be affixed to the sensor shaft. The first wheel-half may impart the rotations on the sensor shaft for sensing via a coupling with an external device, such as external threads of a ball screw nut. The second wheel-half may be supported by the sensor shaft and configured to rotate relative to the sensor shaft. The leg spring may torsionally couple the first wheel-half and the second wheel-half. The leg spring may cause the second wheel-half to an opposing lash of the external threads of the ball screw nut, thereby providing zero gear-lash.