Steering System Universal Joint Coupling for Axis Offset
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Solution Overview
Problem
Existing vehicle steering systems face challenges in accurately transmitting steering torque due to deviations in the central axes of the strut and worm wheel, leading to stress concentration and inaccurate power transmission to the steered wheels.
Innovation Solution
A vehicle steering system employing a laterally independent steer-by-wire system with electric motors and a coupling mechanism using universal joints to offset the axes of the input and output shafts, allowing for angular and eccentric offsets to reduce stress and ensure precise torque transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the central axis of the worm wheel and the central axis of the strut are coupled rigidly by splines, then the structural strength is improved, but the manufacturing precision deteriorates due to inability to accommodate axis offset
Solution Approach 1:
A coupling mechanism with universal joints is introduced as an intermediary between the worm wheel and the strut. This coupling mechanism includes a first universal joint that couples the input shaft (connected to worm wheel) and a coupling shaft, and a second universal joint that couples the coupling shaft and the output shaft (connected to strut), enabling accommodation of axis offset while maintaining strength
Solution Approach 2:
The rigid spline connection is segmented into multiple universal joints with intermediate coupling shafts. This segmentation allows each joint to handle specific angular and eccentric offsets independently, achieving both strength and alignment precision
2Adaptability or versatility
If rubber is interposed between the bearing and vehicle body to offset axis deviation, then the adaptability is improved, but the response time deteriorates due to time difference in rotation transmission
Solution Approach 1:
The rubber-based flexible connection is replaced with a mechanical coupling mechanism using universal joints. This mechanical system transmits rotation instantaneously without the time delay inherent in rubber deformation, while still accommodating axis offsets through the universal joint geometry
Solution Approach 2:
The coupling mechanism allows dynamic adjustment of angular and eccentric offset parameters through the universal joint configurations, maintaining adaptability while eliminating the time delay associated with rubber-based solutions
3Ease of manufacture
If the strut pivots about a bearing-supported portion that deviates from the pivot center, then the ease of manufacture is improved, but the measurement precision deteriorates due to inaccurate power transmission
Solution Approach 1:
The coupling mechanism with universal joints acts as an intermediary that decouples the bearing support position from the pivot center. This allows the bearing to be positioned easily for manufacturing while the universal joints compensate for the deviation to maintain accurate steering angle transmission
Solution Approach 2:
The universal joints provide dynamic compensation for the offset between bearing support position and pivot center, allowing the system to maintain measurement precision despite manufacturing variations in bearing positioning
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 system enables accurate steering of the wheels by reducing stress concentration and improving torque transmission efficiency, enhancing the durability and responsiveness of the steering mechanism.
Implementation Method 1
a first universal joint (51) that couples an input shaft (30) and a coupling shaft (53), and a second universal joint (52) that couples the coupling shaft (53) and an output shaft (40)
Data Source
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AI summary
A vehicle steering system (1) includes a steering operation mechanism configured to steer a steered wheel, and a steering operation motor (4L) configured to apply a drive force for steering the steered wheel to the steering operation mechanism. The steering operation mechanism includes an input shaft (30) to which the drive force from the steering operation motor is input, an output shaft (40) configured to output the drive force from the input shaft to the steered wheel, and a coupling mechanism configured to couple the input shaft and the output shaft to each other. The coupling mechanism includes a first universal joint (51) and a second universal joint (52) that transmit the drive force from the input shaft to the output shaft in a state in which the output shaft is angularly offset from the input shaft. The output shaft constitutes a part of a suspension.