Injection-Molded Rotor Magnet Rib Structure for Thin-Wall Molding
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Solution Overview
Problem
The challenge of manufacturing rotor magnets with reduced thickness leads to increased injection pressure, limiting productivity and increasing costs due to decreased production capacity and molding defects.
Innovation Solution
A rotor magnet design with a cylindrical portion having a thickness smaller than the pinpoint gate tip end portion and a rib protruding in the radial direction, equal to or larger than the gate's inner diameter, facilitating reduced injection pressure and enabling multi-piece molding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the thickness of the cylindrical portion is reduced to improve weight and thickness reduction, then the rotor magnet becomes thinner and lighter, but the injection pressure increases and productivity decreases
Solution Approach 1:
The rotor magnet is segmented into two functional portions: a cylindrical portion with reduced thickness for weight reduction, and a rib portion with increased thickness for maintaining injection pressure. This segmentation allows each portion to serve its specific function optimally without compromising overall productivity
Solution Approach 2:
Different portions of the rotor magnet are given different thickness characteristics: the cylindrical portion has small thickness for weight reduction, while the rib portion has large thickness for facilitating material injection. This local differentiation of properties resolves the contradiction between weight reduction and injection pressure management
2Length of stationary object
If the thickness of the cylindrical portion is reduced to improve rotor compactness, then the rotor magnet becomes more compact, but the injection pressure increases causing molding defects
Solution Approach 1:
The rotor magnet is divided into a cylindrical portion for compactness and a rib portion for injection facilitation. This segmentation allows the cylindrical portion to achieve reduced thickness for compactness while the rib portion maintains sufficient thickness to prevent injection pressure-related molding defects
Solution Approach 2:
The rib portion acts as an intermediary structure that mediates between the thin cylindrical portion and the injection molding process. It provides a thicker pathway for material injection, ensuring proper filling and curing without defects, while allowing the cylindrical portion to maintain its compact dimensions
3Length of stationary object
If the thickness of the cylindrical portion is reduced to improve rotor compactness, then the rotor magnet becomes thinner, but the number of magnets produced per charging step decreases
Solution Approach 1:
The rotor magnet is segmented into a thin cylindrical portion for compactness and a thicker rib portion for injection facilitation. This allows multiple thin cylindrical magnets to be produced per charging step since the rib portion ensures proper material flow and filling, thereby maintaining high productivity despite reduced cylindrical thickness
Solution Approach 2:
Different regions of the rotor magnet have different thickness optimized for their specific functions: the cylindrical portion is thin for compactness while the rib portion is thick for injection purposes. This local quality differentiation enables both compact design and high production capacity
Data Source
AI summary
A rotor magnet of the disclosure is provided turnably relative to a substrate to which a stator or a rotation angle sensor is fixed, is disposed so as to face the stator or the rotation angle sensor, and is formed by injection-molding a material mixture of a magnetic material and a resin through a pinpoint gate. The rotor magnet includes a cylindrical portion formed in a cylindrical shape and having a plurality of magnetic poles arranged, and a rib formed in a shape protruding in a radial direction at an end portion of the cylindrical portion in an axial direction. The thickness of the cylindrical portion is smaller than the inner diameter of a tip end portion of the pinpoint gate, and the thickness of the rib is equal to or larger than the inner diameter of the tip end portion of the pinpoint gate.