Magnetostrictive Sensor Hollow Shaft Segmentation
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Solution Overview
Problem
Existing magnetostrictive torque and axial-force sensors face instability issues due to magnetism and strain effects from the torque-transmitting shafts, leading to unstable sensor signals and reduced precision in detecting high steering torques and axial forces, especially in applications requiring high mechanical strength like electric power steering systems.
Innovation Solution
A magnetostrictive mechanical quantity sensor design where a hollow shaft with a magnetostrictive film is separate from the operation shaft, allowing for optimal surface treatments on the operation shaft and thermal refining of the hollow shaft to enhance mechanical properties, while the magnetostrictive film is stabilized through heat treatments and demagnetization, reducing susceptibility to magnetism and strain effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If surface treatments such as carburization, induction hardening, shot peening are applied to the pinion to increase mechanical strength, then the mechanical strength of the torque-transmitting shaft is improved, but the magnetostrictive film becomes susceptible to magnetism and strain effects causing signal instability
Solution Approach 1:
The torque-transmitting shaft is divided into two separate components: a pinion shaft (operation shaft) that receives surface treatments for high mechanical strength, and a hollow shaft that carries the magnetostrictive film and is not subjected to harmful surface treatments. This segmentation allows each component to be optimized for its specific function without compromising the other.
Solution Approach 2:
The magnetostrictive film is extracted from the pinion shaft and placed on a separate hollow shaft. This extraction removes the magnetostrictive film from the harmful environment created by surface treatments (carbon diffusion, residual stresses), thereby stabilizing the sensor signals while allowing the pinion shaft to undergo necessary hardening treatments.
2Strength
If heat treatments are applied to the torque-transmitting shaft to enhance mechanical properties, then the strength and durability are improved, but the magnetostrictive film stability deteriorates due to magnetism and strain effects
Solution Approach 1:
The torque-transmitting shaft is segmented into a pinion shaft that undergoes heat treatments for mechanical strength, and a hollow shaft that houses the magnetostrictive film and avoids heat treatment to maintain film stability and measurement precision.
Solution Approach 2:
The hollow shaft acts as an intermediary component that transmits torque from the pinion shaft to the rack shaft while protecting the magnetostrictive film from the harmful effects of heat treatments. The magnetostrictive film is applied to the hollow shaft which does not undergo carburization or induction hardening, thus maintaining stable sensor signals.
3Strength
If a solid shaft with pinion is used as torque-transmitting shaft, then the mechanical strength is sufficient for high steering torque, but the magnetostrictive film cannot be stabilized due to carbon diffusion and residual stresses from surface treatments
Solution Approach 1:
The torque-transmitting system is segmented into a solid pinion shaft for high mechanical strength and a hollow shaft with magnetostrictive film for stable sensing. The pinion shaft undergoes carburization and induction hardening to achieve high strength, while the hollow shaft remains free from carbon diffusion and residual stresses.
Solution Approach 2:
The magnetostrictive film is taken out from the pinion shaft and placed on a separate hollow shaft that does not undergo surface treatments. This extraction eliminates the harmful interactions between carbon diffusion/residual stresses and the magnetostrictive film, while the pinion shaft retains its high mechanical strength properties.
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 increases the stability of magnetostrictive properties, leading to more precise detection of torque and axial forces, enhancing steerability and braking efficiency by stabilizing sensor signals and improving mechanical strength.
Implementation Method 1
The change in magnetostriction that occurs in the magnetostrictive film in response to the steering torque is detected by the magnetostrictive torque sensor using an electrical coil and a magnetostriction-detection circuit
Implementation Method 2
the magnetostrictive film is stabilized through heat treatments and demagnetization
Data Source
AI summary
A magnetostrictive mechanical quantity sensor for detecting torque or axial force is disclosed, which sensor comprises a hollow shaft and an operation shaft. The hollow shaft has a magnetostrictive film formed on its outer perimeter surface. The operation shaft is subject to torque or axial force acting from outside and is linked to and fit inside the hollow shaft.