Steering Angle Sensor Backlash Reduction via Biasing
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Solution Overview
Problem
Conventional steering angle sensors experience errors in detecting the rotation angle of a steering shaft due to backlash between gears, which affects the accuracy of steering wheel rotation measurement.
Innovation Solution
A steering angle sensor design that includes a first gear with an annular body and teeth, a second gear with a magnetic member and teeth meshing with the first gear, a third gear with a magnetic member and teeth meshing with the second gear, and a biasing member to reduce backlash between the gears, using magnetoresistance effect elements to detect rotation angles and combine them to determine the absolute steering angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If gears are used to transmit rotation from the steering shaft, then the rotation angle can be detected, but backlash between gears causes detection error
Solution Approach 1:
The biasing member is pre-installed to apply a biasing force to the first gear, causing it to preliminarily engage with the second gear in a specific direction. This preliminary engagement eliminates backlash before rotation transmission begins, ensuring accurate detection from the start of steering input.
Solution Approach 2:
The biasing member acts as an intermediary element between the first gear and the housing. It mediates the interaction by applying continuous biasing force to maintain proper gear engagement, thereby eliminating the harmful backlash while allowing necessary rotational movement.
2Measurement precision
If a biasing member is added to reduce backlash, then detection accuracy improves, but device complexity increases
Solution Approach 1:
The biasing member serves multiple functions simultaneously: it applies biasing force to eliminate backlash, maintains proper gear engagement, and provides structural support for the first gear. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity.
Solution Approach 2:
The biasing member changes the engagement state parameter of the gears from loose (with backlash) to tight (without backlash). By adjusting this engagement parameter through applied force, the system achieves high detection accuracy without requiring complex mechanical constraints or multiple adjustment mechanisms.
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 effectively reduces errors in detecting the steering shaft's rotation angle by minimizing backlash and enhancing the accuracy of steering wheel rotation measurement, ensuring precise determination of the steering wheel's rotation from a neutral position.
Implementation Method 1
a first magnetoresistance effect element that detects a first rotation angle as a rotation angle of the second gear by detecting a change of magnetic field generated by the magnetic member of the second gear
Implementation Method 2
a second magnetoresistance effect element that detects a second rotation angle as a rotation angle of the third gear by detecting a change of magnetic field generated by the magnetic member of the third gear
Data Source
AI summary
A steering angle sensor for a vehicle including a steering angle sensor housing, a first gear, a rotation transmitting portion, a second gear meshing with the first gear, a third gear meshing with the first gear or the second gear, first and second magnetoresistance effect elements to detect first and second rotation angles as rotation angles of the second and third gears, respectively, and a biasing member disposed in the steering angle sensor housing to bias the first gear toward the second gear, wherein the first and rotation angles are combined to determine an absolute steering angle indicative of an amount of rotation of a steering wheel when the steering wheel is rotated from a neutral position in which a steerable road wheel is oriented to a straight ahead direction of the vehicle.