Torque Sensor Magnet Fixation via Metal Sleeve
Solution Overview
Problem
Conventional torque sensor units face instability due to the susceptibility of resin materials to temperature changes, leading to thermal expansion and potential breakage, which affects the stable fixation of magnets in steering devices.
Innovation Solution
A torque sensor unit design featuring a metal sleeve with axial and radial position restricting parts, combined with a composite magnet and filling material of lower Young's modulus, ensures stable magnet fixation by preventing axial and radial displacement, and utilizing a metal sleeve and yoke members to maintain the magnet's position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If resin material is used to join the magnet and sleeve, then the magnet can be fixed to the sleeve, but the resin material becomes thermally expanded or broken by shrinkage during cold temperatures so that the magnet cannot be stably fixed in position
Solution Approach 1:
The invention changes the material parameter from resin to metal for the sleeve, which has superior thermal stability and mechanical strength. The metal sleeve maintains its dimensional stability across temperature variations, preventing the thermal expansion and cold shrinkage issues that plague resin materials, thereby ensuring reliable magnet fixation.
Solution Approach 2:
The invention uses a composite structure combining metal sleeve with resin filling material. The metal sleeve provides the primary structural support and thermal stability, while the resin filling material fills gaps and provides additional bonding. This composite approach leverages the strengths of both materials to achieve reliable fixation.
2Strength
If resin material is used to join the magnet and sleeve, then the magnet can be fixed to the sleeve, but the resin material is significantly deteriorated with time so that the magnet cannot be stably fixed in position
Solution Approach 1:
The invention changes the material parameter from resin to metal for the sleeve, which has significantly longer service life and resistance to deterioration over time. Metal materials do not degrade like resin, ensuring the fixation system maintains its integrity throughout the product's operational lifetime.
Solution Approach 2:
The composite structure with metal sleeve and resin filling material allows the durable metal component to provide long-term structural support while the resin provides initial bonding and gap filling, creating a fixation system with extended service life.
3Strength
If resin material is used to join the magnet and sleeve, then the magnet can be fixed to the sleeve, but the resin material has higher expansion coefficient than metal materials so that the magnet cannot be stably fixed in position
Solution Approach 1:
The invention changes the material parameter from resin to metal for the sleeve, which has a much lower thermal expansion coefficient. This dimensional stability ensures that the sleeve maintains its size and shape across temperature variations, providing stable magnet fixation without the expansion and contraction issues of resin materials.
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 solution effectively stabilizes the magnet's position, maintaining accurate torque detection despite temperature changes and material deterioration, enhancing the durability and reliability of the torque sensor unit.
Implementation Method 1
a magnetic sensor accommodated in an air gap between the first and second magnetosensitive members and adapted to detect a magnetic flux passing through between the magnetosensitive members
Implementation Method 2
a magnetic sensor having a hall element to detect a change in magnetic field between the first and second yoke members
Implementation Method 3
a torque sensor unit coupled around one of the shaft members of the steering shaft... the rotating element having first and second shaft members formed of a metal material and connected to each other through a torsion bar
Data Source
AI summary
Disclosed is a torque sensor unit including a magnetic member fixed to a first output shaft member, a pair of first and second yoke members fixed to an input shaft member and surrounding an outer circumferential side of the magnetic member and a magnetic sensor adapted to detect a magnetic flux passing through between the yoke members. The magnetic member is provided with a sleeve and a permanent magnet. The sleeve is formed of a metal material in a substantially cylindrical shape and has a plurality of radially extending support portions and a plurality of axially extending engagement protrusions between the support portions. The permanent magnet is formed into an annular shape and has a plurality of axially extending engagement grooves cut in an inner circumferential surface thereof. The permanent magnet and the sleeve are coupled via a resin-based filling material.