Magnetostrictive Torque Sensor Shaft Austenite Reduction
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Solution Overview
Problem
Magnetostrictive torque sensors with high non-magnetic austenite content exhibit reduced sensitivity and increased hysteresis error, while reducing austenite to improve sensitivity can compromise toughness and lead to shaft cracking.
Innovation Solution
A method involving heat treatment of chrome steel or chrome-molybdenum steel shafts through carburizing, quenching, and tempering, followed by shot peening with specific parameters to reduce austenite and enhance magnetic permeability sensitivity while maintaining toughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the amount of austenite in the shaft is reduced to improve sensitivity, then sensor sensitivity is improved, but toughness of the shaft is reduced causing cracks
Solution Approach 1:
The patent applies local quality by performing shot peening only at the sensor mounting position rather than the entire shaft. This creates a localized region with reduced austenite content and improved magnetic permeability sensitivity, while the rest of the shaft maintains its original toughness. The localized treatment resolves the contradiction by achieving high sensitivity where needed without compromising overall structural integrity.
Solution Approach 2:
The patent changes physical parameters through shot peening, specifically altering the microstructure and magnetic properties at the sensor mounting location. By controlling shot peening parameters (shot material, particle size, blasting strength, duration), the patent achieves optimal balance between sensitivity improvement and toughness preservation through parameter optimization.
2Measurement precision
If shot peening is performed to reduce austenite and improve sensitivity, then sensor sensitivity is improved, but hysteresis error increases
Solution Approach 1:
The patent optimizes shot peening parameters (shot material type, particle size distribution, blasting strength, and duration) to achieve the desired balance between reducing austenite content for sensitivity improvement and controlling hysteresis error. Through careful parameter selection, the patent minimizes excessive microstructural changes that would increase hysteresis while still achieving sufficient austenite reduction.
Solution Approach 2:
The patent applies partial action by performing shot peening only at the sensor mounting position rather than the entire shaft. This localized approach reduces austenite content sufficiently to improve sensitivity at the measurement location without excessive treatment that would increase hysteresis error throughout the entire shaft.
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 method improves sensor sensitivity and reduces hysteresis error while ensuring the shaft's toughness, achieving optimal performance across a wide temperature range with enhanced mass productivity.
Implementation Method 1
it is considered that shot peening causes transformation from non-magnetic austenite to magnetic martensite
Implementation Method 2
magnetostrictive shaft with magnetic permeability varying according to applied stress
Implementation Method 3
conducting heat treatment on a shaft material comprising chrome steel or chrome-molybdenum steel by carburizing, quenching and tempering
Data Source
AI summary
Provided is a method for manufacturing a magnetostrictive torque sensor shaft mounting a sensor portion of a magnetostrictive torque sensor. The method includes conducting heat treatment on a shaft material including chrome steel or chrome-molybdenum steel by carburizing, quenching and tempering, and conducting shot peening on the shaft material after the heat treatment at least on a position where the sensor portion is to be mounted. The shot peening is conducted by firing shot with a particle size of not less than 0.6 mm and a Rockwell hardness of not less than 60 at a jet pressure of not less than 0.4 MPa for a jet exposure time of not less than 2 minutes.