Overmolded Permanent Magnet Rotor for Adhesive-Free Assembly
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Solution Overview
Problem
Existing permanent magnet rotors face challenges in securely fixing magnets to the rotor without adhesives and require additional assembly steps for bearing parts, leading to increased complexity and weight.
Innovation Solution
A permanent magnet rotor design featuring a cylindrical outer section with annularly disposed magnets having tapered end sections, overmolded with a polymer material to securely attach to a magnetic annular ring, eliminating the need for adhesives and simplifying assembly by integrating the magnets and bearing parts in a single molding step.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If magnets are fixed to the rotor using traditional methods (adhesives, mechanical fasteners), then the magnets can be securely attached, but the assembly complexity and number of manufacturing steps increase
Solution Approach 1:
The patent combines the magnet fixation function with the rotor body structure by integrating magnets directly into the rotor during the injection molding process. The polymer material serves both as structural support and as the fixing medium, eliminating separate fixation components and steps while ensuring secure attachment through direct integration.
Solution Approach 2:
The magnets are positioned in their final locations within the rotor body before the polymer material is injected. This preliminary positioning ensures that the magnets are securely fixed in the correct orientation and position, while the subsequent injection process automatically provides the fixation without requiring additional assembly steps.
2Reliability
If a thick layer of polymer material is used to cover the magnets, then the magnets are well protected and securely fixed, but the rotor weight increases
Solution Approach 1:
The polymer material thickness is optimized locally rather than uniformly throughout. The injection molding process allows the polymer to concentrate where needed for magnet fixation and protection, while minimizing thickness in areas where it is not required, thus reducing overall rotor weight while maintaining adequate protection and fixation.
Solution Approach 2:
The patent optimizes the polymer material thickness parameter to achieve the minimum required for secure fixation and protection. By carefully controlling the injection parameters and polymer flow, the design achieves adequate fixation with reduced material quantity, directly reducing rotor weight while maintaining reliability.
3Reliability
If additional assembly steps are used for bearing parts, then the bearing components can be properly installed, but the manufacturing time and productivity decrease
Solution Approach 1:
The patent merges the bearing installation process with the main rotor manufacturing process by integrating bearing components into the injection molding cycle. The bearing parts are positioned and secured within the rotor body during the same manufacturing step, eliminating separate installation operations and significantly improving productivity while maintaining installation quality.
Solution Approach 2:
Bearing components are pre-positioned within the rotor mold cavity before the polymer injection. This preliminary action ensures proper bearing installation while allowing the polymer material to automatically secure them during the injection process, eliminating the need for subsequent assembly steps and improving manufacturing efficiency.
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 design provides a lightweight, securely fixed magnet arrangement with reduced assembly complexity, protecting components from unwanted contact and enabling direct attachment of a cooling fan, while minimizing the gap between magnets and stator.
Implementation Method 1
The tapered sections of the magnets facilitate the flow of the overmolding polymer material to the center section of the magnets
Data Source
AI summary
A permanent magnet rotor for a motor is disclosed. The rotor includes a generally cylindrical outer section and a bearing section arranged radially inwards of the cylindrical outer section for rotatably supporting the rotor. The cylindrical outer section and the bearing section are connected by a generally radially extending cover wall. The cylindrical outer section, the bearing section and the radially extending cover wall define at least partly a space for receiving a stator. The cylindrical outer section includes an annular ring of a magnetic material, a plurality of annularly disposed magnets and an inner wall, the inner wall having a substantially cylindrical inner surface. Each magnet has a first and a second end in a circumferential direction and is provided with a radially inwards facing surface having a central section and first and second tapered end sections in the circumferential direction.