Rotor Magnet Retention Cap With Spring Bias Against Wobble
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Solution Overview
Problem
In brushless DC motors, manufacturing inefficiencies and inaccuracies can cause permanent magnets to wobble within the rotor core pockets due to mismatched lengths, leading to motor noise and vibration.
Innovation Solution
A magnet retention cap with a spring structure is used to axially support the rotor core, applying a biasing force to the permanent magnets, reducing or eliminating wobble by compensating for manufacturing inconsistencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If end caps are mounted on the rotor core to retain permanent magnets, then the magnets are secured within the pockets, but manufacturing tolerances cause gaps and wobble between the magnets and rotor core
Solution Approach 1:
The patent changes the physical state of the retention mechanism from rigid (end caps) to elastic (spring structure). The spring structure can deform elastically to accommodate variations in magnet length and positioning, absorbing tolerance stack-up errors while maintaining secure magnet retention. This elastic parameter change allows the system to adapt to manufacturing variations without requiring high precision.
Solution Approach 2:
The patent transitions from a static retention system (fixed end caps) to a dynamic system (spring structure with wave springs). The spring structure can dynamically adjust its compression and expansion to accommodate magnet movement and wobble, providing continuous adaptive retention force that compensates for manufacturing tolerances and operational vibrations.
2Device complexity
If rigid end caps are used to retain magnets, then the structure is simple, but magnet wobble causes noise and vibration
Solution Approach 1:
The patent changes the mechanical property parameter of the retention structure from rigid to elastic. The spring structure's elastic deformation capability allows it to absorb vibrations and eliminate magnet wobble, significantly reducing noise and vibration while maintaining structural simplicity through the use of spring elements.
Solution Approach 2:
The spring structure acts as a cushioning element that anticipates and absorbs potential vibrations and impacts before they can cause harm. The pre-compressed springs provide continuous damping force that prevents magnet wobble and reduces noise generation during motor operation.
3Reliability
If the spring structure is designed to accommodate tolerance variations, then magnet retention is improved, but the device complexity increases
Solution Approach 1:
The spring structure is designed to self-adjust and self-compensate for tolerance variations without requiring external control or adjustment mechanisms. The elastic deformation of the springs automatically accommodates magnet length variations and positioning errors, providing reliable retention while maintaining relatively simple device architecture.
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 significantly reduces motor noise and vibration by up to 80% by securely retaining the magnets within the rotor core pockets.
Implementation Method 1
the spring structure includes spring elements configured to apply biasing forces to the permanent magnets along the longitudinal direction of the magnet pockets
Implementation Method 2
a magnet retention cap mounted at an end of the rotor core to axially stop the movement of the permanent magnets out of the magnet pockets
Data Source
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AI summary
A motor assembly is provided including a stator assembly and a rotor assembly rotatably disposed relative to the stator assembly. The rotor assembly includes a rotor core having magnet pockets formed therethrough along a longitudinal direction, permanent magnets received within the magnet pockets, and a spring structure disposed in contact with the end of the rotor core. The spring structure includes spring elements configured to apply biasing forces to the permanent magnets along the longitudinal direction of the magnet pockets. Optionally a magnet retention end cap is provided to secure the spring structure to the end of the rotor core.