Torque Sensor Magnetic Shielding for External Field Interference
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Solution Overview
Problem
Existing torque sensors in power steering systems face accuracy issues due to the detection of external magnetic fields, which interfere with the internal magnetic field measurements, leading to decreased torque detection precision.
Innovation Solution
The torque sensor design incorporates a magnetic member with alternately arranged poles, paired yoke members, and arc-shaped magnetic flux concentration rings that shield and concentrate the internal magnetic field, using a Hall device to detect changes in the magnetic field between the yoke members and flux concentration rings, thereby isolating the external magnetic field interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the magnetic flux concentrators are exposed to the outside without shielding, then the magnetic sensor can detect the internal magnetic field, but external magnetic fields interfere with the detection and reduce accuracy
Solution Approach 1:
A magnetic shield member is introduced as an intermediary between the external magnetic field and the magnetic flux concentrators. This shield selectively blocks external magnetic fields while allowing the internal magnetic field to pass through to the sensor, thus resolving the contradiction between detecting internal fields and preventing external interference
Solution Approach 2:
The harmful external magnetic field is extracted or separated from the detection path by positioning the magnetic shield to block only external fields, while the internal magnetic field generated by the magnetic member remains accessible to the magnetic flux concentrators and sensor
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
This configuration enhances the accuracy of torque detection by attenuating external magnetic field effects, improving the precision of the torque sensor's measurements and reducing interference, thus providing reliable steering torque feedback for the power steering system.
Implementation Method 1
a magnetic member provided at the first shaft member so as to rotate integrally with the first shaft member and having different magnetic poles that are alternately arranged in a circumferential direction concentrically with a rotation axis of the rotation member
Implementation Method 2
a magnetic sensor arranged between the first and second magnetic flux concentration rings and having a Hall device that detects a change of internal magnetic field between the first and second magnetic flux concentration rings
Implementation Method 3
arc-shaped magnetic flux concentration rings that shield and concentrate the internal magnetic field
Data Source
AI summary
Torque sensor has: magnetic member; first yoke member having (a) first nail portions arranged concentrically to face the magnetic member in radial direction and (b) first ring portion; second yoke member having (c) second nail portions arranged concentrically so that the first and second nail portions are circumferentially alternately arranged and the second nail portions face the magnetic member in radial direction and (d) second ring portion; first magnetic flux concentration ring provided between the first and second ring portions; second magnetic flux concentration ring provided between the second ring portion and the first magnetic flux concentration ring; and magnetic sensor. The first and second magnetic flux concentration rings and the first and second ring portions are arranged in layers in radial direction. A part or all of axial direction area of the first and second magnetic flux concentration rings is surrounded and shielded by the second ring portion.