Torque Sensor Yoke Structure for Axis Deviation Tolerance
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Solution Overview
Problem
Manufacturing errors during assembly can cause the central axis of a multipole magnet and a yoke member to deviate, leading to reduced detection accuracy in torque detection devices due to the generation of magnetic poles.
Innovation Solution
The yoke member is designed with primary and secondary yokes having teeth with widths smaller than their respective ring plates, and incorporating reducing portions to minimize magnetic flux to the ring plates, maintaining a gap between the yokes to reduce magnetic flux density and pole strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the central axis of the multipole magnet and yoke member are aligned precisely, then detection accuracy is improved, but manufacturing complexity and assembly difficulty increase due to the need for high precision
Solution Approach 1:
The patent converts the harmful effect of manufacturing errors and axis deviations into a beneficial feature by designing the yoke member with reduced magnetic flux paths. Instead of trying to eliminate deviations through higher precision manufacturing, the invention accepts deviations as inevitable and designs the magnetic circuit to minimize their impact, thereby converting a manufacturing disadvantage into a robust design advantage that maintains detection accuracy without requiring complex assembly procedures
2Strength
If the width of teeth in the yoke member is increased, then structural strength is improved, but magnetic flux density increases leading to generation of magnetic poles and reduced detection accuracy
Solution Approach 1:
The patent applies local quality by creating non-uniform magnetic flux distribution through strategically designed reducing portions in the yoke member. The teeth and ring plates have varying widths and thicknesses at different locations, with narrower sections positioned to reduce magnetic flux in specific areas. This local variation in geometry allows the yoke to maintain overall structural strength while creating localized reductions in magnetic flux density that prevent magnetic pole generation and maintain detection accuracy
3Measurement precision
If the gap between primary and secondary yokes is reduced, then magnetic flux density is improved for better detection, but manufacturing tolerance requirements increase
Solution Approach 1:
The patent converts the harmful effect of gap variations due to manufacturing tolerances into a beneficial feature by designing the magnetic circuit with reduced flux paths. The reducing portions in the yoke member compensate for gap variations, allowing the system to maintain acceptable detection performance without requiring extremely tight manufacturing tolerances. This approach transforms the sensitivity to gap variations into a design parameter that can be managed through geometric optimization rather than strict tolerance control
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 effectively limits the reduction in detection accuracy by reducing magnetic flux and pole strength, even when central axis deviations occur, enhancing the torque detection device's performance.
Implementation Method 1
a torque detection device that detects a change in a magnetic flux generated by relative rotation between a multipole magnet and a yoke member through a magnetic sensor
Implementation Method 2
The primary yoke has at least one reducing portion that is configured to reduce a magnetic flux that flows from a corresponding one of a plurality of primary teeth of the primary yoke to a primary ring plate of the primary yoke
Data Source
AI summary
A yoke member includes a primary yoke and a secondary yoke which are opposed to each other. The primary yoke is configured such that a maximum width of a widest portion of each of a plurality of primary teeth of the primary yoke is smaller than a minimum width of a narrowest portion of a primary ring plate of the primary yoke. The secondary yoke is configured such that a maximum width of a widest portion of each of a plurality of secondary teeth of the secondary yoke is smaller than a minimum width of a narrowest portion of a secondary ring plate of the secondary yoke.