Magnetostrictive Torque Sensor Bobbin Thermal Equalization
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Solution Overview
Problem
Temperature differences between coils and magnetostrictive portions in existing magnetostrictive torque sensors lead to detection errors, resulting in inadequate auxiliary torque production in electrically assisted bicycles, affecting pedaling efficiency.
Innovation Solution
A magnetostrictive torque sensor design where a bobbin surrounds the magnetostrictive portion, with coils wound on the bobbin in contact with the magnetostrictive portion, allowing rotation and minimizing temperature differences through thermal insulation, ensuring constant distance and enhanced detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If coils and magnetostrictive portions are supported by separate members, then device structure is simplified, but temperature difference between coils and magnetostrictive portions increases causing detection error
Solution Approach 1:
The patent merges the support function for both coils and magnetostrictive portions into a single common support member (the rotational shaft). The magnetostrictive portions are formed directly on the rotational shaft, and the coils are wound around the rotational shaft, ensuring both components are supported by the same member. This eliminates temperature differences between separately supported components while maintaining structural simplicity.
2Ease of manufacture
If coils are located far from magnetostrictive portions, then device assembly is easier, but detection sensitivity decreases
Solution Approach 1:
The patent positions the coils in direct contact with the magnetostrictive portions on the rotational shaft, creating an optimal magnetic coupling field between the two components. This close positioning maximizes the magnetic interaction and detection sensitivity while the rotational shaft's structure naturally facilitates assembly, eliminating the need for complex positioning mechanisms.
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 detection accuracy and sensitivity by quickly equalizing temperatures between coils and magnetostrictive portions, reducing external influences and maintaining consistent torque detection.
Implementation Method 1
The magnetostrictive torque sensor includes coils and magnetostrictive portions, is disposed along an outer circumference of a crankshaft. The crankshaft is subjected to a torsional torque when the rider pedals the bicycle. The application of the torsional torque to the crankshaft causes a change in magnetic field in the magnetostrictive portions formed on an outer circumferential surface of the crankshaft. The change in magnetic field is detected by the coils
Data Source
AI summary
A magnetostrictive torque sensor includes a magnetostrictive portion formed on a rotational shaft, a bobbin surrounding an outer circumference of the magnetostrictive portion, and a coil wound on the bobbin for detecting a change in magnetic property of the magnetostrictive portion. The bobbin fits over the magnetostrictive portion in contact with the magnetostrictive portion in such a manner as to allow rotation of the magnetostrictive portion relative to the bobbin. The magnetostrictive torque sensor is carried on an electrically assisted bicycle or an electric power steering apparatus of a vehicle.