Torque Detector Magnetic Shield Angle Design for Thermal Stress Reduction
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Solution Overview
Problem
Conventional torque detectors experience large thermal stresses due to the difference in thermal contraction between the sensor housing and the magnetic shield, leading to potential water ingress and reduced water-tightness.
Innovation Solution
A torque detector design with a magnetic shield having a second angle smaller than the first angle, where the outer side face of the shield end portion is not orthogonal to the radial direction of the sensor housing, reducing the perpendicular pressing force and thereby minimizing thermal stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sensor housing and magnetic shield are formed with different linear expansion coefficients to achieve water-tightness, then water-tightness is improved, but large thermal stresses are generated due to differential thermal contraction
Solution Approach 1:
The magnetic shield is designed with different angles at different locations: the shield body has a first angle (α1) that is larger than the second angle (α2) of the shield end portions. This local differentiation allows the shield body to maintain strong contact with the sensor housing for water-tightness, while the shield end portions with smaller angles reduce thermal stress concentration at the contact points with the magnetic flux collecting holder.
Solution Approach 2:
The invention changes the geometric parameters of the magnetic shield by defining specific angle relationships (α1 > α2) between different portions. This parameter optimization allows the shield to accommodate differential thermal contraction between materials while maintaining effective contact for water-tightness sealing.
2Ease of manufacture
If the shield end portions are made orthogonal to the radial direction for simple manufacturing, then ease of manufacture is improved, but large thermal stresses are generated at the contact points with the sensor housing
Solution Approach 1:
Rather than making the entire shield orthogonal for ease of manufacture, the invention applies different angular configurations to different portions: the shield body maintains a larger angle (α1) while the shield end portions use a smaller angle (α2). This local optimization reduces thermal stress at critical contact points without significantly complicating the overall manufacturing process.
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 configuration effectively suppresses the generation of large thermal stresses in the sensor housing, enhancing water-tightness and reducing thermal stress-related issues.
Implementation Method 1
a magnetic flux collecting ring that is attached to an inner peripheral face of the magnetic flux collecting holder and that collects magnetic fluxes of the magnetic yoke
Implementation Method 2
a magnetic shield formed by bending a metal plate and attached to an outer peripheral face of the magnetic flux collecting holder
Data Source
AI summary
A torque detector includes: a magnetic flux collecting unit including a magnetic flux collecting holder formed in an annular shape by resin molding and a magnetic shield formed by bending a metal plate and attached to an outer peripheral face of the magnetic flux collecting holder; and a sensor housing formed integrally with the magnetic flux collecting unit. The magnetic shield has a shield body, a shield end portion, and a bent portion. A second angle formed between an outer side face of the shield end portion and a radial direction is smaller than a first angle formed between an outer peripheral face of the shield body and the radial direction.