Torque Sensor Magnetic Symmetry for Detection Stability

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Solution Overview

Problem

Conventional torque sensors experience detection property fluctuations between magnetic sensors, which affect the accuracy and reliability of torque measurement in electric power steering systems.

Innovation Solution

The torque sensor design includes a retaining portion that is magnetically symmetrical with respect to the magnetic sensors, retaining the magnetism collecting members in a position that equally affects both sensors, thereby stabilizing their detection properties and reducing fluctuations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If a retaining portion is used to hold magnetism collecting members, then the magnetism collecting members are securely retained, but detection property fluctuation between magnetic sensors increases

Engineering Contradiction:

Improveretention stability of magnetism collecting membersVSAvoiddetection property consistency between magnetic sensors

Core Design Contradiction:

Stability of the object's compositionVSMeasurement precision

Solution Approach 1:

The retaining portion is designed with asymmetric features including a retaining protrusion that contacts only one surface of each magnetism collecting member, and a biasing portion that applies unidirectional force. This asymmetric design prevents symmetric stress distribution that would cause detection fluctuations, while still achieving secure retention of the magnetism collecting members.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The retaining portion applies localized retention forces at specific points (retaining protrusion contacting one surface) rather than uniform distribution. The biasing portion provides localized preloading in a specific direction, creating controlled stress concentration that prevents fluctuation while maintaining secure retention.

Inventive Principle:

Principle #3Local quality

2Stability of the object's composition

If the retaining portion retains all end portions of magnetism collecting members, then retention is comprehensive, but stress distribution becomes uneven causing detection fluctuation

Engineering Contradiction:

Improvecomprehensive retention of magnetism collecting membersVSAvoidmagnetic field detection accuracy

Core Design Contradiction:

Stability of the object's compositionVSMeasurement precision

Solution Approach 1:

The design extracts the retention function from a symmetric multi-point contact system to a simplified asymmetric system with retaining protrusions contacting only one surface of each magnetism collecting member. This extraction removes the source of symmetric stress distribution while maintaining comprehensive retention through the biasing portion's preloading action.

Inventive Principle:

Principle #2Taking out (Extraction)

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 design enhances the detection accuracy and reliability of the torque sensors, ensuring proper control of the electric motor and reducing the influence of retaining portion-induced stress on magnetic field detection.

Implementation Method 1

first and second magnetism collecting members 221, 222 made of magnetic material

Methodology Applied

Scientific EffectMagnetic conduction: Magnetism

Implementation Method 2

first and second magnetic sensors 23, 24 disposed between the first and second magnetism collecting members 221, 222

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS11273866B2Torque sensor and electric power steering system

Publication Date: 2022.03.15 ASTEMO LTD

AI summary

Provided is a torque sensor and an electric power steering system, which are capable of suppressing a detection property fluctuation between two magnetic sensors. A retaining portion is disposed at first and second magnetism collecting members in such a position as to be magnetically symmetrical with respect to first and second magnetic sensors.