Magnet Unit Thermal Shock Resistance Design
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Solution Overview
Problem
Existing position detection devices face challenges in maintaining thermal shock resistance when detecting linear movement of objects due to temperature changes, which can cause stress and damage to the magnet unit, especially when the magnet needs to be lengthened for increased movement.
Innovation Solution
A magnet unit design where the magnet is mounted on a magnet holding member with exposed end surfaces, allowing for thermal expansion without applying stress to the resin, and using positioning features like concave and convex portions to regulate the magnet's position and reduce thermal shock effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the magnet is lengthened to detect larger linear movement, then the detection range is improved, but thermal expansion stress on the resin magnet holding member increases causing cracks and reducing thermal shock resistance
Solution Approach 1:
The magnet is divided into multiple smaller magnets arranged in series along the detection direction. This segmentation allows each individual magnet to expand and contract independently with temperature changes, preventing the accumulation of thermal stress that would occur in a single long magnet, while still achieving the required total detection range through the combined length of multiple magnets.
Solution Approach 2:
The invention changes the physical configuration parameter of the magnet from a single continuous piece to multiple discrete units. This parameter change enables the system to accommodate thermal expansion differently - each small magnet can expand independently rather than creating stress throughout a long continuous magnet, thereby maintaining thermal shock resistance while preserving the extended detection range.
2Ease of manufacture
If the magnet is completely enclosed in the resin magnet holding member, then the structure is simplified and manufacturing is easier, but thermal expansion causes stress and damage to the resin
Solution Approach 1:
The magnet is segmented into multiple small magnets that are independently mounted in the resin housing. This segmentation creates natural expansion gaps between individual magnets and between magnets and the housing walls, allowing thermal expansion without generating damaging stress concentrations, while still maintaining a relatively simple overall manufacturing process.
Solution Approach 2:
The invention extracts the magnet from complete enclosure within the resin. By leaving portions of the magnet exposed or creating gaps between the magnet and resin boundaries, the design allows thermal expansion to occur without constraint, eliminating the harmful stress that would accumulate if the magnet were completely enclosed in the resin housing.
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 enables accurate position detection with enhanced thermal shock resistance, preventing damage from temperature changes and ensuring reliable operation even with large movement ranges.
Implementation Method 1
a magnet unit including a magnet 10 that moves linearly or rotatably with respect to a magnetic detection section 41 that detects a change in a magnetic field
Implementation Method 2
a linear expansion difference due to a temperature change between the magnet and a resin part may cause stress on the resin part
Data Source
AI summary
The present invention provides a magnet unit and a position detection device that are excellent in thermal shock resistance without the risk of being damaged due to a temperature change and that are capable of detecting a position with high accuracy. A magnet unit comprises: a magnet that moves in a linear or rotating manner relative to a magnetic detection element (magnetic detection section) for detecting a change in a magnetic field; and a magnet holding member that moves in a linear or rotating manner while being fixed to an object L to be detected and that holds the magnet attached thereto. The magnet holding member has a fixed part that is fixed to the object L to be detected and a magnet housing part to which the magnet is attached. The magnet housing part has openings where opposite end surface portions of the magnet are exposed.