Bonded Field Magnet Press-Fitting for Accurate Yoke Inner Surfaces
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Solution Overview
Problem
Conventional methods for manufacturing field magnets with bonded magnets and yokes are costly due to the requirement for high accuracy in both the inner and outer surfaces of the yoke, which is not performance-critical, leading to increased manufacturing costs.
Innovation Solution
A method involving reheating and softening the bonded magnet after thermal curing to allow press-fitting into a yoke without restraining the outer circumferential side, enabling the bonded magnet to conform to the inner surface accuracy of the yoke, thus reducing the need for precise outer surface accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high accuracy is ensured for both inner and outer surfaces of the yoke, then assembly precision is improved, but manufacturing cost increases
Solution Approach 1:
The invention applies different quality requirements to different parts of the yoke: the inner surface requires high accuracy (within 0.05mm) to ensure proper gap with rotor armature, while the outer circumferential surface requires only ordinary accuracy. This local differentiation of quality standards reduces manufacturing cost while maintaining assembly precision where it matters.
Solution Approach 2:
The bonded magnet is subjected to thermal curing treatment before press-fitting to expand it, allowing it to be inserted into the yoke's inner surface. After insertion, the magnet contracts and firmly bonds to the inner surface. This preliminary thermal expansion action enables the magnet to conform to the inner surface accuracy without requiring the outer yoke surface to be highly accurate.
2Manufacturing precision
If the outer circumferential side of the yoke is restrained during press-fitting, then positioning accuracy is improved, but device complexity increases
Solution Approach 1:
The invention extracts the positioning function from the outer circumferential surface of the yoke and relocates it to the inner surface. By ensuring high accuracy only on the inner surface where the bonded magnet contacts, the need for complex restraint mechanisms on the outer surface is eliminated, simplifying the overall device structure.
Solution Approach 2:
The bonded magnet itself serves the positioning function through its thermal expansion and contraction behavior. When heated, the magnet expands and is easily inserted into the yoke; when cooled, it contracts and firmly bonds to the inner surface, automatically achieving accurate positioning without requiring external restraint mechanisms.
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 approach reduces the manufacturing cost of the yoke and field magnet by ensuring the desired gap between the inner surface of the bonded magnet and the rotor armature, while maintaining the necessary accuracy for motor performance.
Implementation Method 1
a softening step for reheating and softening the bonded magnet after thermal curing treatment
Implementation Method 2
a phenomenon that the bonded magnet disposed in the yoke oxidizes and expands by heating
Data Source
AI summary
A field magnet manufacturing method where a bonded magnet's inner surface press-fitted in a yoke has a certain accuracy irrespective of the accuracy of the yoke's outer circumferential surface. A cylindrical bonded magnet from binding magnet particles with a thermosetting resin is fixed in a tubular yoke of magnetic material. The method includes reheating and softening the bonded magnet after thermal curing; and press-fitting in the bonded magnet after the softening step from a tapered portion on one end side of the yoke to press the bonded magnet's outer circumferential surface against the yoke's inner surface. The press-fitting includes feeding the bonded magnet relatively into the yoke while allowing a relative posture variation between the bonded magnet and the yoke so the bonded magnet's inner surface to be remolded into a shape along the inner surface of the yoke exhibits almost the same accuracy as the yoke's inner surface.