Rotor Magnet Molding Structure for Air Trap and Weld Line Control
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Solution Overview
Problem
The existing methods for manufacturing motors, particularly in electric power steering systems, face issues with incomplete molding, air traps, and weld line generation due to the thin thickness of molding portions around magnets, which hinders smooth injection molding and air discharge.
Innovation Solution
Incorporating a protrusion part in the molding portion that guides air traps and weld lines away from functional areas, allowing for complete molding and secure air discharge without the need for preheating or cutting processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If injection molding is performed in a region with thin molding portion thickness around magnets, then the motor can be manufactured with magnets attached to the rotor core, but incomplete molding, air traps, and weld lines occur due to poor air discharge
Solution Approach 1:
The molding portion is divided into multiple regions: a first molding portion with greater thickness for smooth injection molding and air discharge, and a second molding portion with thinner thickness that maintains the original design. This segmentation allows the injection molding process to complete successfully in the first portion while the second portion retains its functional thinness, thereby resolving the contradiction between manufacturability and molding completeness.
2Volume of moving object
If the molding portion thickness is reduced to maintain compact motor design, then the motor size is minimized, but air discharge becomes difficult and weld lines are generated
Solution Approach 1:
The molding portion is segmented into a first region with increased thickness designed for smooth injection molding and air discharge, and a second region with reduced thickness that maintains compact motor dimensions. This spatial segmentation allows the motor to maintain a compact overall size while having specific regions optimized for manufacturing quality, thereby resolving the contradiction between miniaturization and manufacturing defects.
3Manufacturing precision
If preheating and cutting processes are added to prevent incomplete molding and air traps, then molding quality improves, but manufacturing complexity and time increase
Solution Approach 1:
The protrusion part is designed in advance during the molding portion configuration, creating a built-in feature that facilitates air discharge and prevents weld lines during injection molding. This preliminary structural action eliminates the need for subsequent preheating and cutting processes, thereby improving molding quality while reducing manufacturing process complexity and time.
Data Source
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AI summary
The present invention may provide a motor including a stator, a rotor disposed inside the stator, and a shaft coupled to the rotor, wherein the rotor includes a rotor core disposed outside the shaft, a magnet disposed outside the rotor core, and a molding part which molds the rotor core and the magnet, and the molding part includes an upper part disposed on an upper surface of the magnet, a lower part disposed on a lower surface of the magnet, a lateral part disposed on a side surface of the magnet, and a protrusion part which protrudes from the lateral part in an axial direction of the shaft.