External Rotor Helical Spring Insert for Magnetic Circuit Closure
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Solution Overview
Problem
The production of external rotors for electric motors with precise dimensional tolerances is challenging, particularly in reducing manufacturing costs and avoiding the need for structurally rigid metal components, while maintaining a continuous magnetic circuit.
Innovation Solution
Employing a helical spring as a metal insert that elastically adapts to the annular configuration of the magnet, ensuring a secure and continuous magnetic circuit without the need for precise dimensional tolerances, and using overmoulding to integrate with a plastic cup-shaped body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal ring is used to close the magnetic circuit, then the magnetic circuit continuity is improved, but the manufacturing precision requirement and assembly difficulty increase due to the need for precise dimensional tolerances
Solution Approach 1:
The invention changes the physical state of the metal insert from rigid to elastic by using a helical spring configuration. This allows the metal insert to deform elastically during assembly, accommodating dimensional variations in the magnets while maintaining magnetic circuit continuity. The elastic property enables the system to absorb dimensional tolerances that would otherwise require extremely precise manufacturing.
Solution Approach 2:
The metal insert is designed as a helical spring, which is inherently flexible and elastic. This flexible structure can adapt to the dimensions of the magnets it surrounds, ensuring continuous magnetic circuit closure without requiring precise dimensional matching. The spring's flexibility allows it to conform to slight variations in magnet dimensions while maintaining structural integrity and magnetic continuity.
2Reliability
If a rigid metal ring is used, then the magnetic circuit closure is ensured, but the assembly process becomes costly and time-consuming due to precise tolerance requirements
Solution Approach 1:
The invention transforms the metal insert from a rigid structure to an elastic helical spring. This parameter change in material behavior allows the component to self-adjust during assembly, eliminating the need for expensive precision machining and complex assembly procedures. The elastic spring can be easily fitted around magnets of varying dimensions within a broader tolerance range, significantly reducing manufacturing costs and assembly time.
Solution Approach 2:
The helical spring's elastic nature enables it to self-adjust and self-align during the assembly process. When the spring is fitted around the magnets, it automatically conforms to their dimensions and ensures proper positioning, eliminating the need for complex alignment procedures or specialized assembly equipment. This self-adjusting capability simplifies the assembly process and reduces labor costs.
3Adaptability or versatility
If multiple magnetic wedges are used instead of a toroidal magnet, then the manufacturing flexibility is improved, but the liquid injection risk displacing the wedges increases during moulding
Solution Approach 1:
The helical spring acts as a flexible retaining structure that surrounds and secures the magnetic wedges in place. During the liquid injection moulding process, the spring's elastic structure prevents the liquid from displacing the individual wedges, while still allowing for the use of multiple separate wedge magnets rather than a single toroidal magnet. This maintains manufacturing flexibility while ensuring wedge position stability.
Solution Approach 2:
The helical spring is installed around the magnetic wedges before the liquid injection moulding process. This beforehand placement of the spring provides protective cushioning that prevents the injected liquid from displacing the wedges. The spring acts as a barrier and stabilizing structure, securing the wedges in their intended positions throughout the moulding process.
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
Simplifies the production process, reduces manufacturing costs, and ensures efficient assembly of the external rotor by maintaining magnetic continuity and alignment of magnetic elements.
Implementation Method 1
A helical spring, namely a spirally wound metal body which adapts elastically to the annular configuration of the at least one magnet
Data Source
Figure 1
Figure 2~3
Figure 4~5a
AI summary
Permanent magnet external rotor (1) for an electric motor, comprising a cup-shaped body (2) provided with a bottom (20) and a side wall (21); at least one magnet (3), defining a plurality of poles and fixed inside said cup-shaped body (2); and a metal insert (4), defined by a helical spring fitted around the at least one magnet (3) which forms the closure of a magnetic circuit of the electric motor.