Amorphous Magnetic Ring for Magnetostrictive Torque Sensor
Solution Overview
Problem
Conventional magnetostrictive torque sensors using powder magnetic cores are bulky due to the required thickness of the magnetic ring, making it difficult to downsize them for installation in small spaces.
Innovation Solution
A magnetostrictive torque sensor design featuring detection coils wrapped with an amorphous tape made of amorphous soft magnetic material, where the magnetic ring's thickness is optimized to be between 0.075 mm and 1.000 mm, specifically 1.455 times the skin effect thickness of the magnetostrictive material, to enhance sensitivity and reduce errors while minimizing size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a powder magnetic core is used as a magnetic ring, then magnetic flux leakage is suppressed and sensitivity is maintained, but the magnetic ring thickness must be 1 mm to 2 mm or more, making the sensor bulky
Solution Approach 1:
The patent changes the material parameter from conventional powder magnetic core to amorphous soft magnetic material, which has superior magnetic properties allowing the magnetic ring thickness to be reduced to 0.1 mm or less while maintaining sufficient magnetic flux confinement and sensitivity
Solution Approach 2:
The patent uses an amorphous soft magnetic material which is a composite material structure that combines soft magnetic properties with thin-film compatibility, enabling both thin thickness and effective magnetic flux containment
2Volume of moving object
If the magnetic ring is made thinner to downsize the sensor, then installation in small spaces becomes possible, but magnetic flux leakage increases and sensitivity decreases
Solution Approach 1:
By changing the magnetic material parameters (using amorphous soft magnetic material with superior permeability and lower loss), the patent achieves effective magnetic flux confinement even at thicknesses of 0.1 mm or less, maintaining sensitivity while enabling miniaturization
Solution Approach 2:
The patent replaces the conventional thick powder magnetic core structure with a thin amorphous magnetic ring structure, fundamentally changing the mechanical configuration while maintaining magnetic functionality through material property optimization
3Volume of moving object
If amorphous soft magnetic material is used to reduce magnetic ring thickness, then sensor size is reduced, but manufacturing precision must be controlled to maintain performance
Solution Approach 1:
The patent employs an amorphous soft magnetic material that can be manufactured as thin films or tapes, which inherently provide better thickness uniformity and control compared to conventional powder cores, facilitating precise thickness control at 0.1 mm or less
Solution Approach 2:
The patent specifies optimal thickness ranges (0.05 mm to 0.2 mm, preferably 0.075 mm to 0.125 mm) based on the skin effect thickness of the magnetostrictive material, creating a standardized design parameter that simplifies manufacturing while ensuring performance
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 achieves improved sensor sensitivity and error suppression, allowing for a downsized magnetostrictive torque sensor that maintains performance comparable to conventional designs, with errors kept below 3.0% full scale.
Implementation Method 1
a magnetic ring configured to cover around the detection coils... made of amorphous soft magnetic material... magnetic permeability changes when a torque is applied
Implementation Method 2
uses a magnetostrictive material having magnetostrictive characteristics in which magnetic permeability changes when a torque (rotational torque) is applied
Implementation Method 3
the sensor is configured that a change in the magnetic permeability of the magnetostrictive material when the torque is applied is detected as a change in inductance of a detection coil
Implementation Method 4
a thickness of the magnetic ring is 1.455 times or more as thick as a skin effect thickness of the magnetostrictive material... excitation frequency of 50 kHz or more and 333 kHz or less
Data Source
AI summary
A magnetostrictive torque sensor includes detection coils formed around a magnetostrictive material made of chrome steel or chrome molybdenum steel, a magnetic ring configured to cover around the detection coils, and a drive unit for providing alternating current excitation to the detection coils at an excitation frequency of 50 kHz or more and 333 kHz or less. A torque applied to the magnetostrictive material is detected based on a change in inductance of the detection coils. The magnetic ring is configured by wrapping around the detection coils with an amorphous tape made of amorphous soft magnetic material in a tape shape. The thickness of the magnetic ring is 1.455 times or more as thick as a skin effect thickness of the magnetostrictive material and less than 1.000 mm.