Magnetostrictive Torque Sensor Housing for Noise Reduction

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Solution Overview

Problem

Conventional magnetostrictive torque sensors in electrically operated power steering systems are susceptible to noise from alternating magnetic fields, leading to inaccurate torque detection and vibrations, which affect the driver's steering experience.

Innovation Solution

A magnetostrictive torque sensor design featuring a housing with a resin part, a tubular metal part, and a metal flange, where the tubular part and flange are made of soft or nonmagnetic metals to redirect alternating magnetic fluxes away from the sensor components, reducing noise interference and improving accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the torque sensor uses a conventional aluminum alloy housing with coils connected to external pins, then the structure is simple and easy to manufacture, but alternating magnetic flux passes through the shaft and magnetostrictive films causing noise and conduction failures

Engineering Contradiction:

Improvetorque detection accuracyVSAvoidhousing structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The housing is segmented into three distinct parts: a resin part (housing the coils and connector), a tubular metal part (providing magnetic shielding), and a flange (providing structural support and grounding). This segmentation allows each part to perform its specific function optimally while collectively solving the noise and conduction problems.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The housing combines multiple materials with different properties: resin (electrical insulation), soft magnetic metal (magnetic flux guidance), and nonmagnetic metal (structural support). This composite structure creates a multi-functional housing that simultaneously provides mechanical support, magnetic shielding, and electrical insulation.

Inventive Principle:

Principle #40Composite materials

2Object-affected harmful factors

If low-pass filters are added to remove noise from alternating magnetic flux, then noise is reduced, but the torque detection response becomes delayed

Engineering Contradiction:

Improvenoise from alternating magnetic fluxVSAvoidtorque detection response

Core Design Contradiction:

Object-affected harmful factorsVSSpeed

Solution Approach 1:

Instead of filtering out the alternating magnetic flux as a harmful element, the invention redirects it through the tubular metal part and flange to flow paths that bypass the magnetostrictive films and coils. This converts the potentially harmful alternating flux into a benign path, eliminating noise without delaying the torque detection response.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Ease of manufacture

If the leading and trailing ends of coils are connected to external pins, then electrical connection is simple, but conduction failure occurs when coils contact the aluminum alloy housing

Engineering Contradiction:

Improvecoil connectionVSAvoidelectrical conduction

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The resin part acts as an intermediary between the coil leads and the external connector pins. It provides electrical insulation while maintaining mechanical connection, preventing direct contact between the coil leads and the conductive housing structure, thereby eliminating conduction failures.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 design enhances torque detection accuracy and reduces noise-induced vibrations, providing a smooth and responsive steering experience by isolating the sensor from alternating magnetic fields, thus eliminating the need for low-pass filters and minimizing interference with other sensors.

Implementation Method 1

the tubular part and flange are made of soft or nonmagnetic metals to redirect alternating magnetic fluxes away from the sensor components

Methodology Applied

Scientific EffectMagnetic flux redirection: Magnetic Field

Implementation Method 2

a magnetostrictive member disposed on a shaft member, coils for detecting a change in a magnetic property of the magnetostrictive member

Methodology Applied

Scientific EffectMagnetostriction: Magnetostriction

Data Source

PatentUS8701503B2Magnetostrictive torque sensor and electrical power steering device

Publication Date: 2014.04.22 HONDA MOTOR CO LTD

AI summary

Disclosed are a magnetostrictive torque sensor and an electrical power steering device, wherein a first torque sensor has: one magnetostrictive film provided on a steering shaft; a first coil and a second coil that detect changes in the magnetic characteristics of the magnetostrictive film; and a first housing that contains, at least, the steering shaft, the magnetostrictive film, the first coil, and the second coil. The first housing has a resin part, a cylindrical part made of a metal that is soft magnetic, and a flange part made of a metal that is soft magnetic. The resin part, the cylindrical part, and the flange part are formed as a unit.