Rotation Detection Device Welded Holding Members
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Solution Overview
Problem
Existing rotation detecting devices suffer from decreased detection precision due to internal stress caused by cooling contracture during insert molding, leading to magnetic hysteresis and deformation in soft magnetic materials like Permalloy.
Innovation Solution
A rotation detecting device where a first holding member and a second holding member are welded and fixed to each other, sandwiching the detecting member, to restrain deformation and reduce internal stress, thereby enhancing detection precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If insert molding technique is used to integrally mold yokes and magnetism collecting rings with resin holder, then manufacturing efficiency is improved, but internal stress is generated causing deformation and reduced detection precision
Solution Approach 1:
The detecting member is divided into separate components (yokes and magnetism collecting rings) that are not integrally molded with the resin holder. This segmentation eliminates the internal stress caused by insert molding while maintaining manufacturing efficiency through modular assembly.
Solution Approach 2:
The yokes and magnetism collecting rings are extracted from the integral molding process and held separately by the resin holder. This extraction removes the harmful cooling contracture effect from the detecting member while the holder provides structural support.
2Ease of manufacture
If cooling contracture occurs during insert molding, then manufacturing process is completed, but internal stress deforms the detecting member reducing precision
Solution Approach 1:
The resin holder is designed to utilize its own cooling contracture characteristics to apply beneficial compressive force on the detecting member, counteracting the harmful internal stress from the molding process and preventing deformation.
Solution Approach 2:
The resin holder acts as an intermediary between the detecting member and the external environment, mediating the stress distribution and protecting the detecting member from deformation caused by manufacturing processes.
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 increases detection precision by suppressing deformation and magnetic hysteresis, improving the accuracy of torque sensing in power steering devices.
Implementation Method 1
a Hall IC sensor that detects the magnetic fluxes between the magnetism collecting rings
Implementation Method 2
a magnetic hysteresis of the Permalloy is increased
Data Source
AI summary
A rotation detecting device includes first and second members that are rotatable relative to each other around a rotation axis, a magnetic member fixed to the first member and having poles alternately arranged around the rotation axis, a detecting member arranged to face the magnetic member and made of a magnetic material, and a holding member fixed to the second member. The holding member is made of thermoplastic resin and includes first and second holding members that are welded and fixed to each other. The detecting member is disposed between the first and second holding members to prevent relative contact between the detecting member and the second member. The rotation detecting device further includes a magnetic sensor that detects relative rotation between the first and second members by sensing a change of magnetic field in the detecting member due to the relative rotation.