Permanent Magnet Fixing Structure with Gradient Adhesive Filling
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Solution Overview
Problem
The existing methods for fixing permanent magnets in motors, such as using adhesives, often result in stress and cracking due to differences in linear expansion coefficients between the magnet, housing, and adhesive, especially under temperature changes, leading to uneven adhesive coating and potential displacement of the magnet.
Innovation Solution
A fixing structure with a cylindrical housing and an adhesive layer where the filling rate of adhesive is higher at one axial end of the permanent magnet than the other, with the latter end having a higher density, configured to manage stress and prevent cracking by increasing strength at the higher stress region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If adhesive is coated on the inner circumferential surface of the case before inserting the permanent magnet, then the permanent magnet can be fixed to the housing, but the adhesive coating becomes uneven and displacement occurs due to dragging during insertion
Solution Approach 1:
The adhesive is pre-coated on the outer circumferential surface of the permanent magnet before insertion, rather than on the housing. This preliminary action ensures the adhesive is already in position and will not be disturbed or dragged during the insertion process, thereby maintaining uniform coating while achieving reliable fixation.
2Reliability
If the permanent magnet, case, and adhesive have different linear expansion coefficients, then temperature changes cause stress that can crack the permanent magnet, but increasing adhesive filling rate at high-stress regions increases manufacturing complexity
Solution Approach 1:
The adhesive filling rate is made non-uniform along the axial direction, with higher filling rates at axial ends where thermal stress concentrates. This local quality adjustment针对性地 strengthens high-stress regions without requiring complete redesign of the entire structure, balancing crack prevention with manufacturing feasibility.
Solution Approach 2:
The adhesive filling rate parameter is varied along the axial direction of the permanent magnet, creating a gradient distribution. This parameter change allows the adhesive layer to provide differential support - stronger at stress-prone axial ends and lighter in the middle - effectively managing thermal stress while maintaining reasonable manufacturing complexity.
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 configuration effectively prevents cracks in the permanent magnet by distributing stress more evenly and maintaining the magnetic properties, while also improving positioning precision and motor performance.
Implementation Method 1
If there is a difference in linear expansion coefficient between the permanent magnet, the case, and the adhesive, the permanent magnet will undergo a stress due to a change in the temperature
Implementation Method 2
an adhesive layer formed in a gap between the housing and the permanent magnet and having an adhesive for fixing the permanent magnet to the housing
Data Source
AI summary
A fixing structure for a permanent magnet includes: a cylindrical housing; a permanent magnet housed inside the housing; and an adhesive layer formed in a gap G between the housing and the permanent magnet and having an adhesive for fixing the permanent magnet to the housing. The adhesive layer is formed such that a filling rate of the adhesive is higher in the gap at another axial end of the permanent magnet than at one axial end of the permanent magnet. The permanent magnet is configured such that a density at said other axial end is higher than the density at said one axial end.