Brushless Rotor Reinforcement Welding for Surface Magnet Centrifugal Loads
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Solution Overview
Problem
Brushless electric machines with surface magnets face challenges in mechanical strength against centrifugal forces, and existing attachment methods are inadequate to prevent defects and failures, especially at high speeds.
Innovation Solution
A thin-walled reinforcement is radially applied to the rotor's permanent magnets using welding points in a material and/or form-fitting manner, with the reinforcement designed as a hollow cylindrical sleeve, optimized in number, shape, and distribution based on operating parameters to securely attach the magnets without interfering with magnetic flux.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If surface magnets are used on the rotor, then the magnetic field strength is improved, but the mechanical strength against centrifugal forces deteriorates
Solution Approach 1:
A reinforcement element is inserted into a recess in the rotor base body, creating a nested structure where the reinforcement is housed within the rotor. This nesting approach allows the reinforcement to be securely integrated while maintaining the surface magnet configuration for optimal magnetic field strength.
Solution Approach 2:
The reinforcement element is pre-positioned in the recess before the surface magnets are mounted. This preliminary action ensures that the reinforcement is already in place to provide mechanical support against centrifugal forces before the magnets are attached, preventing defects and failures during operation.
2Reliability
If a thick reinforcement is used to secure permanent magnets, then mechanical strength is improved, but the gap between rotor and stator increases
Solution Approach 1:
The reinforcement element is designed as a thin-walled structure that provides sufficient mechanical strength to secure permanent magnets against centrifugal forces while maintaining a compact profile. The thin-walled design ensures that the reinforcement does not increase the rotor radius excessively, thereby minimizing the gap between rotor and stator.
Solution Approach 2:
The reinforcement element uses a thin-walled design that is optimized for strength-to-weight ratio, providing adequate mechanical support without excessive material usage. This approach allows for a compact rotor design that maintains small air gap dimensions while still securing the permanent magnets effectively.
3Ease of manufacture
If surface magnets are used instead of buried magnets, then manufacturing ease is improved, but mechanical strength against centrifugal forces deteriorates
Solution Approach 1:
The reinforcement element is nested within a recess in the rotor base body, creating an integrated structure that combines the ease of surface magnet mounting with enhanced mechanical strength. This nesting approach maintains the manufacturing simplicity of surface magnets while adding structural support to withstand centrifugal forces.
Solution Approach 2:
The reinforcement element is pre-installed in the rotor base body before the surface magnets are mounted. This preliminary action ensures that the mechanical strength enhancement is already in place before magnet installation, allowing the manufacturing process to remain simple while achieving improved mechanical reliability.
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 solution effectively secures the permanent magnets at high speeds, minimizes efficiency losses, and prevents damage to the electric machine, while allowing a small gap between the rotor and stator for improved efficiency.
Implementation Method 1
the reinforcement is connected to the permanent magnets by a plurality of welding points in a material and/or form-fitting manner
Data Source
AI summary
A brushless electric machine, in particular a brushless DC motor, has a stator and a rotor arranged within the stator so as to be rotatable relative thereto. The rotor has a cylindrical base body which is non-rotatably connected to a machine shaft and carries a plurality of permanent magnets on its outer circumference, and the stator has a stator winding with a plurality of single-tooth windings for driving the rotor via an electrically generated magnetic field. The permanent magnets of the rotor are fixed by a thin-walled reinforcement radially surrounding them, wherein the reinforcement is connected to the permanent magnets by a plurality of welding points in a materially and/or positively locking manner.