Disk Rotor Magnet Securing via Hub Bonding and Cover Plates
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Solution Overview
Problem
In high-speed alternating current synchronous servomotors with disk-shaped rotors, the challenge is securing permanent magnets effectively against centrifugal forces without increasing the magnetic air gap, which compromises torque and efficiency due to the small contact surface area between magnets and the rotor, leading to potential detachment and reduced motor performance.
Innovation Solution
The solution involves a combination of a hub with a non-conductive material and a unique geometry that includes flat planes and interstices for the magnets, which are secured using a bonding agent and cover plates, eliminating the need for axial reinforcement bands, thereby reducing the magnetic air gap and enhancing mechanical rigidity and torque transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a band is used to secure permanent magnets against centrifugal force, then the magnets are restrained from radial displacement, but the band stretches and breaks at high speeds, causing magnet detachment
Solution Approach 1:
The rotor is divided into a hub and a metal sheet assembly, with magnets secured through a combination of bonding to the hub and mechanical constraint by cover plates, replacing the single-band solution with multiple functional segments that share the load
Solution Approach 2:
The solution combines epoxy resin bonding (adhesive material) with metal cover plates (structural material) to create a composite fastening system that leverages both chemical bonding and mechanical constraint, eliminating the need for a purely elastic band
2Reliability
If axial reinforcement bands are used to prevent magnet detachment, then magnet security is improved, but the magnetic air gap increases, reducing motor torque and efficiency
Solution Approach 1:
The fastening system transitions from purely axial reinforcement (bands wrapping around) to a combination of radial bonding (magnets to hub) and axial constraint (cover plates), utilizing multiple spatial dimensions to achieve both security and compactness
Solution Approach 2:
The axial reinforcement function is extracted from the band and transferred to the cover plates, allowing the band to be eliminated entirely and the air gap to be minimized while maintaining magnet retention through the bonding agent and plate constraint
3Power
If the magnet volume is increased to compensate for reduced magnetic force due to larger air gap, then torque is maintained, but the centrifugal force and axial force on magnets increase, requiring stronger fastening
Solution Approach 1:
The bonding agent is applied in advance to secure magnets to the hub before rotation, creating a pre-established mechanical bond that prevents radial displacement and reduces the effective centrifugal force impact, allowing smaller magnets to be used
Solution Approach 2:
The combination of epoxy resin bonding and metal cover plate constraint creates a composite fastening system with superior load-bearing capacity, enabling the use of smaller magnets that generate less centrifugal force while maintaining secure attachment
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 ensures secure magnet attachment at high speeds, maintains efficiency by minimizing the magnetic air gap, and reduces the volume and material requirements for a given torque, enhancing the motor's performance and reliability.
Implementation Method 1
secured using a bonding agent
Implementation Method 2
centrifugal force created by the rotation of the rotor
Data Source
AI summary
The present invention relates to an alternating-current-synchronous-servomotor having a disk-shaped rotor (55, 56) which is located between two stator halves. The rotor comprises an even number of flat permanent magnets pieces (56) having magnet field lines extending parallel to the shaft of the rotor. The permanent magnet pieces (56) form an annular like series including interstices extending around a hub (55) supported on the shaft. The magnet pieces are made of a magnetically non-conductive material and have flat sides acting as magnetic pole surfaces (N, S) which extend in parallel planes to which the axis of the shaft extend perpendicularly. The permanent magnet pieces (56) have limiting surfaces located radially inwards, which are supported each on one of peripheral planes of the hub (55). Said peripheral planes and said limiting surfaces comprise cooperating means (57, 58, 59, 60) for fixing said magnet pieces (54) on said hub (55).