Rotor Magnet Adhesive Bonding for Electrical Machines
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Solution Overview
Problem
The existing methods for adhering magnets to shafts in electrical machine rotors often result in weaker joins due to difficulties in achieving a continuous distribution of adhesive along the length of the magnet bore, particularly as magnet length increases, leading to potential fracture under tensile stress.
Innovation Solution
A method involving a rotor core assembly with end caps and a sleeve, where the shaft forms interference fits with the end caps and a clearance fit with the magnet, allowing adhesive to be drawn into the clearance between the magnet and shaft, creating a continuous and strong bond, and using different adhesives for securing the end caps and the magnet to the shaft to manage stress and alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If adhesive is applied by inserting shaft into magnet bore and rotating shaft, then adhesive distribution is improved, but for long magnets the adhesive distribution becomes discontinuous and bond strength decreases
Solution Approach 1:
The patent introduces an intermediary substance (adhesive with specific viscosity and curing properties) and an intermediary process (vacuum application, controlled dispensing) to ensure continuous adhesive distribution along the magnet-shaft interface, resolving the discontinuity problem in long magnets
Solution Approach 2:
The patent applies preliminary actions by pre-heating the adhesive to optimal temperature, pre-vacuuming the magnet bore to remove air pockets, and pre-positioning the adhesive delivery system before shaft insertion to ensure continuous adhesive distribution from the start
2Manufacturing precision
If adhesive is injected into clearance between shaft and magnet, then adhesive can reach full length, but air pockets are trapped and bond strength decreases
Solution Approach 1:
The patent utilizes pneumatic principles by applying vacuum pressure to the magnet bore during adhesive application, creating a pressure differential that draws adhesive into the clearance and actively removes air pockets, ensuring complete and reliable bonding
Solution Approach 2:
The patent changes physical parameters of the adhesive (temperature, viscosity) and the application environment (pressure, vacuum level) to optimize adhesive flow and air pocket removal, transforming the adhesive from a simple filler to an actively distributed bonding medium
3Ease of manufacture
If magnet is press fitted onto shaft, then assembly is simple, but magnet fractures under tensile stress due to brittleness
Solution Approach 1:
The patent replaces the permanent, brittle magnet-direct-fit approach with a sacrificial adhesive layer that absorbs stress, allowing the magnet to be easily assembled and protected from fracture throughout its service life
Solution Approach 2:
The patent creates a composite bonding system combining the magnetic material, adhesive material, and shaft material, where each material contributes its optimal properties (magnet provides magnetic function, adhesive provides stress distribution and protection, shaft provides structural support)
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 method ensures a continuous adhesive distribution between the magnet and shaft, enhancing the bond strength and preventing magnet fracture under stress, while also aligning the magnet concentrically with the shaft and managing radial stresses through the sleeve.
Implementation Method 1
the adhesive forming a wet seal between the shaft and the magnet such that adhesive is drawn into a clearance formed between the magnet and the shaft
Data Source
AI summary
A rotor that includes a rotor core assembly secured to a shaft. The rotor core assembly includes a magnet and an end cap secured to an end of the magnet. Each of the magnet and the end cap has a bore into which the shaft extends. The end cap forms an interference fit with the shaft. The magnet forms a clearance fit with the shaft and an adhesive is located in the clearance between the magnet and the shaft. Additionally, a method of manufacturing the rotor. The method includes inserting the shaft into the bore of the end cap. An adhesive is then introduced into the bore of the magnet and the shaft is inserted into the bore of the magnet so as to cause adhesive to be drawn into the clearance defined between the magnet and the shaft.