Overmolded Rotor Assembly with Interlocking Interface
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Solution Overview
Problem
Existing rotor assemblies for electric motors face challenges in achieving bi-directional magnetization without adhesives, which leads to issues with thermal degradation and slippage, increasing manufacturing complexity and cost, and compromising the motor's robustness and accuracy.
Innovation Solution
A rotor assembly is designed with a cylindrical magnet member and output shaft overmolded together using moldable magnetic and plastic materials, eliminating the need for adhesives and incorporating complementarily-engagable interface elements to prevent dislocation, and optionally featuring an integrally formed pinion gear for enhanced robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If adhesives are used to connect the output shaft to the magnet, then the rotor assembly can be assembled, but the adhesive degrades under high operating temperatures reducing motor effectiveness
Solution Approach 1:
The invention removes the adhesive component entirely from the rotor assembly. Instead of using adhesive to connect the output shaft to the magnet, the patent employs a mechanical interference fit system where the output shaft is press-fit into a recess in the magnet with complementary interface elements (protrusions and recesses) that prevent relative motion without requiring thermal-resistant bonding agents.
Solution Approach 2:
The invention introduces complementary interface elements (protrusions on one component and recesses on the other) as intermediaries between the output shaft and magnet. These interface elements serve as mechanical mediators that transfer torque and prevent slippage without relying on adhesive bonding, thereby eliminating the thermal degradation issue while maintaining assembly capability.
2Ease of manufacture
If adhesives are used to connect components, then assembly is achieved, but slippage occurs under high torque damaging the output shaft
Solution Approach 1:
The invention employs complementary interface elements with precisely engineered geometric profiles (protrusions and recesses) that mate together to prevent relative motion between the output shaft and magnet. This geometric interlocking system provides robust torque transmission by distributing mechanical loads across the interface surfaces rather than relying on adhesive shear strength, eliminating slippage under high torque conditions.
3Ease of manufacture
If adhesives are used for connection, then the rotor can be assembled, but manufacturing cost and difficulty increase
Solution Approach 1:
The invention eliminates the adhesive application step from the manufacturing process. By using a mechanical interference fit with complementary interface elements, the patent removes the need for adhesive dispensing, curing, and quality inspection steps associated with adhesive bonding, thereby reducing manufacturing complexity and cost while maintaining assembly capability.
4Manufacturing precision
If electromagnetic coils are used to impart bi-directional magnetization, then the magnet can be magnetized, but excessive heat is generated deforming other rotor components
Solution Approach 1:
The invention replaces the electromagnetic coil system with a mechanical magnetization system using permanent magnets mounted on the tooling. This substitution eliminates the excessive heat generation associated with electromagnetic coils while maintaining the capability to impart bi-directional magnetization to the rotor magnet, thereby protecting temperature-sensitive rotor components from thermal deformation.
5Manufacturing precision
If electromagnetic coils are used for magnetization, then bi-directional magnetization can be achieved, but the system is vulnerable to coil activation failures
Solution Approach 1:
The invention replaces the electromagnetic coil system with a mechanical permanent magnet system. Permanent magnets provide a passive, fail-safe magnetization source that does not require electrical activation, eliminating the risk of coil activation failures. The mechanical arrangement of permanent magnets on the tooling ensures reliable bi-directional magnetization through direct magnetic field interaction during the molding 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
This solution reduces manufacturing complexity and cost, enhances the rotor's robustness and accuracy by ensuring precise magnetization and torque handling, while avoiding thermal degradation and slippage, resulting in a more reliable and efficient electric motor.
Implementation Method 1
the creation of a bi-directional magnetization of the magnet member of the rotor assembly requires the use of an electromagnetically-generated magnetic field to impart the necessary magnetization
Implementation Method 2
an inner surface of the magnet member and an outer surface of the output shaft have complementarily-engagable interface elements thereon to prevent or limit dislocation of the magnet member and output shaft, at least one of the interface elements being formed by overmolding of the magnet member and output shaft
Data Source
AI summary
A rotor assembly is provided for an electric motor. The rotor assembly includes: a cylindrical magnet member having magnetization in both axial and radial directions, the magnet member being formed from a moldable magnetic material; and an output shaft receivable within the magnet member. An inner surface of the magnet member and an outer surface of the output shaft have complementarily-engagable interface elements thereon to prevent or limit dislocation of the magnet member and output shaft, and at least one of the interface elements is formed by overmolding of the magnet member and output shaft with the other of magnet member and output shaft.