Torque Sensor Magnet Assembly with Segmented Sleeve

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Solution Overview

Problem

The existing torque sensor production process is complicated due to the need to position a magnet on a sleeve before attachment, which can lead to a reduction in detection accuracy.

Innovation Solution

A torque sensor design that includes an annular sleeve, an intermediate member with thin and thick portions, and a magnet placed on the outer surface of the intermediate member, which simplifies the production process and maintains detection accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the magnet is attached to the sleeve with adhesive, then the magnet can be secured to the sleeve, but the production process becomes complicated due to the need to position the magnet before attachment

Engineering Contradiction:

Improveproduction process complexityVSAvoiddetection accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

An intermediate member is introduced between the sleeve and the magnet. This intermediate member features a cylindrical outer surface that fits into a corresponding cylindrical groove in the sleeve, providing a precise positioning interface. The magnet is then attached to this intermediate member, eliminating the need for direct magnet-to-sleeve positioning while maintaining accurate radial positioning for detection.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Strength

If the sleeve is press-fitted into the first rotating member, then the sleeve can be securely attached, but deformation may occur in the intermediate member connecting portion that holds the magnet

Engineering Contradiction:

Improveattachment strengthVSAvoidpositioning precision

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The sleeve is divided into functionally distinct segments: a rotating member connecting portion for attachment to the first rotating member, an intermediate member connecting portion with a cylindrical groove for positioning the intermediate member, and an enlarged portion that acts as a stress buffer. This segmentation allows each portion to perform its specific function optimally while protecting the magnet-holding section from deformation during press-fitting.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The enlarged portion in the sleeve is positioned between the rotating member connecting portion and the intermediate member connecting portion. This enlarged section acts as a cushioning zone that absorbs and distributes the stress generated during press-fitting, preventing this stress from being transmitted to the intermediate member connecting portion where the magnet is mounted, thereby preserving positioning precision.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Measurement precision

If the distance between the magnet and yoke is maintained, then detection accuracy is preserved, but any deformation in the holding structure compromises this distance

Engineering Contradiction:

Improvedetection accuracyVSAvoidstructural stability

Core Design Contradiction:

Measurement precisionVSStability of the object's composition

Solution Approach 1:

The intermediate member serves as a stable intermediary platform between the sleeve and the magnet. Its cylindrical outer surface, which fits precisely into the cylindrical groove in the sleeve, creates a rigid connection that maintains the radial position of the magnet relative to the sleeve axis. This stable structure ensures the distance between the magnet and yoke remains constant during operation.

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 proposed design prevents deformation of the intermediate member connecting portion, maintains the distance between the magnet and yoke, and simplifies the production process, thereby enhancing detection accuracy and reducing production complexity.

Implementation Method 1

an inner circumferential surface of the thin portion and an inner circumferential surface of the thick portion are in contact with the intermediate member connecting portion

Methodology Applied

Scientific EffectFriction: Friction

Implementation Method 2

The rotating member connecting portion in contact with the first rotating member prevents deformation of the intermediate member connecting portion that holds the magnet when the sleeve is press-fitted into the first rotating member

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS12209925B2Torque sensor and manufacturing method of magnet assembly

Publication Date: 2025.01.28 NSK LTD

AI summary

In a torque sensor, a sleeve is an annular member that is attached to a first rotating member. An intermediate member is an annular member that is placed on an outer circumferential surface of the sleeve. A magnet is an annular member that is placed on an outer circumferential surface of the intermediate member. A yoke is attached to a second rotating member and faces the magnet in a radial direction. A rotating member connecting portion of the sleeve has a cylindrical shape and is contact with the first rotating member. An intermediate member connecting portion is at a position shifted with respect to the rotating member connecting portion in an axial direction. The intermediate member includes a thin portion and a thick portion having a thickness greater than that of the thin portion.