Magnetostrictive Torque Sensor Segmented Hollow Shaft Design
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Solution Overview
Problem
Magnetostrictive torque sensors face challenges in maintaining high sensitivity and stability due to the susceptibility of magnetostrictive films to magnetism and strain from torque transmission shafts, especially when subjected to external forces and heat treatments, which affect the accuracy of steering torque detection in vehicles.
Innovation Solution
A magnetostrictive torque sensor design featuring separate hollow shafts with individually optimized magnetostrictive films on their external surfaces, allowing for different materials and heat treatment conditions, and a torque transmission portion that can be strengthened through surface treatments without affecting the films, thereby enhancing sensitivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If heat treatments are performed on the pinion to increase strength, then the mechanical strength of the pinion is improved, but the magnetostrictive properties of the magnetostrictive film deteriorate due to carbon diffusion and magnetization of the shaft surface
Solution Approach 1:
The shaft is divided into two separate components: a torque transmission shaft that undergoes heat treatment for strength, and a separate hollow shaft that serves as the substrate for the magnetostrictive film. This segmentation allows each component to be optimized independently - the torque transmission shaft can receive carburization and other heat treatments to enhance its mechanical properties, while the hollow shaft provides a stable, non-magnetizing surface for the magnetostrictive film, thereby resolving the contradiction between improving pinion strength and maintaining magnetostrictive stability.
Solution Approach 2:
The hollow shaft acts as an intermediary component between the torque transmission shaft and the magnetostrictive film. It provides a magnetically inert substrate that isolates the magnetostrictive film from the magnetic effects of the torque transmission shaft, even when the shaft undergoes heat treatment. This intermediary structure allows the torque transmission shaft to be strengthened through heat treatment while protecting the magnetostrictive film from magnetic interference, thus resolving the contradiction between strength improvement and magnetostrictive stability.
2Strength
If surface treatments like shot peening are applied to the pinion to increase strength, then the mechanical strength is improved, but compressive stress remains in the shaft surface which affects magnetostrictive stability
Solution Approach 1:
By separating the torque transmission shaft from the hollow shaft, the invention allows the torque transmission shaft to receive surface treatments like shot peening for strength enhancement without transferring compressive stress to the magnetostrictive film. The hollow shaft serves as a separate substrate that does not inherit the stress from the torque transmission shaft, thereby maintaining magnetostrictive stability while enabling the pinion to be strengthened through surface treatment.
Solution Approach 2:
The hollow shaft functions as an intermediary that decouples the stress state of the torque transmission shaft from the magnetostrictive film. Even when the torque transmission shaft undergoes shot peening or other surface treatments that induce compressive stress, the hollow shaft provides a stress-isolated substrate for the magnetostrictive film, preventing stress transfer and maintaining magnetostrictive stability while allowing the pinion to be strengthened.
3Strength
If the torque transmission shaft is made stronger to handle external forces, then the mechanical strength is improved, but the sensitivity of the magnetostrictive film deteriorates due to magnetic effects from the shaft
Solution Approach 1:
The invention segments the torque transmission function from the magnetostrictive sensing function by using separate shafts. The torque transmission shaft can be made stronger through heat treatment and surface treatments to handle external forces, while the hollow shaft provides a magnetically isolated substrate for the magnetostrictive film. This segmentation prevents magnetic effects from the strengthened shaft from interfering with the sensitivity of the magnetostrictive film, allowing both strength and sensitivity requirements to be met simultaneously.
Solution Approach 2:
The hollow shaft serves as a magnetically inert intermediary between the torque transmission shaft and the magnetostrictive film. It allows the torque transmission shaft to be strengthened without transferring magnetic effects to the magnetostrictive film, thereby maintaining the sensitivity required for precise torque detection while enabling the shaft to handle increased external forces.
4Measurement precision
If magnetostrictive film is formed on the torque transmission shaft, then torque detection is enabled, but the film is susceptible to magnetism and strain from the shaft which reduces stability
Solution Approach 1:
The invention separates the torque transmission shaft from the hollow shaft, allowing the magnetostrictive film to be formed on the hollow shaft rather than the torque transmission shaft. This segmentation isolates the magnetostrictive film from the magnetic and strain effects of the torque transmission shaft, thereby improving the stability of magnetostrictive properties while maintaining torque detection capability through the coupled system.
Solution Approach 2:
The hollow shaft acts as an intermediary substrate that provides a stable, magnetically inert surface for the magnetostrictive film. It mediates between the torque transmission shaft and the magnetostrictive film, allowing the film to be formed on a stable platform that does not transfer magnetic or strain effects from the torque transmission shaft, thus improving both detection capability and stability.
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 improves the precision and stability of torque detection, enabling stable and precise steering torque measurement even under increased external forces, enhancing the steering feel and reliability of the sensor.
Implementation Method 1
a magnetostrictive film is formed on an external peripheral surface of the torque transmission shaft... detect changes in magnetostriction that occur in the magnetostrictive film in accordance with the steering torque
Data Source
AI summary
A magnetostrictive torque sensor for detecting a torque comprises an operating shaft, a first hollow shaft, a second hollow shaft, a first magnetostrictive film, and a second magnetostrictive film. Torque acts on the operating shaft from the outside. The first and second hollow shafts are fitted and fixed separately on the operating shaft. The first magnetostrictive film is formed on an external peripheral surface of the first hollow shaft while the second magnetostrictive film is formed on an external peripheral surface of the second hollow shaft.