Magnetostrictive Torque Sensor Shaft Manufacturing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing magnetostrictive torque sensors face reduced sensitivity due to high amounts of non-magnetic retained austenite in the shaft material, which also compromises the toughness of the shaft when attempts are made to reduce it, leading to increased errors in applications like transmission stroke control and engine output control.
Innovation Solution
A method involving carburizing, quenching, and tempering of an iron-based shaft followed by shot peening and surface polishing to reduce non-magnetic retained austenite, enhance magnetic permeability, and improve toughness, using a steel shot media with a Vickers hardness of 1200 HV and subsequent surface polishing to achieve uniform austenite distribution and remove Fe2B, thereby enhancing sensor sensitivity and reducing errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the amount of retained austenite in the shaft is reduced by adjusting heat treatment conditions, then sensor sensitivity is improved, but the toughness of the shaft decreases and the shaft may crack
Solution Approach 1:
The invention applies different treatments to different regions of the shaft. The surface layer is subjected to shot peening with high-hardness shot media to reduce retained austenite and improve sensitivity, while the core maintains traditional heat treatment to preserve toughness. This local differentiation allows simultaneous optimization of sensor sensitivity and shaft reliability.
Solution Approach 2:
The invention changes the hardness parameter of the shot media from conventional levels to 1200 HV or more. This parameter change enables more effective reduction of retained austenite in the surface layer while controlling the overall heat treatment process to maintain shaft toughness. The specific hardness value of the shot media becomes a key control parameter for achieving the desired microstructure.
2Measurement precision
If high-hardness shot media is used for shot peening, then retained austenite is effectively reduced and sensor sensitivity is improved, but manufacturing complexity increases
Solution Approach 1:
The invention specifies a clear parameter threshold for shot media hardness (1200 HV or more) to simplify the selection and procurement process. By establishing this concrete criterion, the manufacturing process becomes more standardized and controllable, reducing the complexity of process optimization while achieving effective retained austenite reduction.
3Manufacturing precision
If surface polishing is performed after shot peening, then Fe2B is removed and uniform austenite distribution is achieved, but manufacturing time increases
Solution Approach 1:
The invention performs surface polishing as a preliminary step before final sensor assembly and calibration. This preliminary surface preparation ensures uniform austenite distribution and removes Fe2B contaminants early in the process, avoiding the need for rework later and actually reducing overall manufacturing cycle time despite the additional polishing step.
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 approach improves sensor sensitivity, reduces hysteresis and angle errors, and maintains the toughness of the shaft, achieving a total error of not more than 3.5% by effectively managing retained austenite distribution and removing surface impurities like Fe2B through surface polishing.
Implementation Method 1
The shaft is manufactured by subjecting a steel shaft material to carburizing, quenching and tempering
Implementation Method 2
The shaft is manufactured by subjecting a steel shaft material to carburizing, quenching and tempering
Implementation Method 3
The shaft is manufactured by subjecting a steel shaft material to carburizing, quenching and tempering
Implementation Method 4
performing shot peening on the shaft material after the heat treatment step at least on a position where a sensor portion of the magnetostrictive torque sensor is to be mounted
Implementation Method 5
The magnetostrictive torque sensor uses a shaft having magnetostrictive characteristic whose magnetic permeability changes when stress is applied
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3
AI summary
This method for manufacturing a magnetostrictive torque sensor shaft 100 to which a sensor portion 2 of a magnetostrictive torque sensor 1 is to be attached includes: a heat treatment step of subjecting an iron-based shaft member to a carburizing, quenching, and tempering process; a shot peening step of performing shot peening using a steel shot media having a Vickers hardness at least equal to 1100 and at most equal to 1300, at least in a position on the shaft member, after the heat treatment step, to which the sensor portion 2 is to be attached; and a surface polishing step of subjecting the shaft member after the shot peening to surface polishing.