Outer Rotor Motor Yoke Design Reducing Leakage Flux
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Solution Overview
Problem
In outer rotor motors, leakage flux allows foreign materials like iron powder to intrude, causing operational noise due to exposed gaps between the rotor magnet and stator teeth, which existing technologies fail to adequately address.
Innovation Solution
A yoke that uninterruptedly covers the radially outer surface and axially-directed surfaces of the rotor magnet, combined with a plastic magnet and integral formation with other components, reduces leakage flux and prevents foreign material intrusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the gap between the rotor magnet and stator teeth is exposed to the outside, then the motor structure is simplified, but foreign materials such as iron powder can intrude into the gap causing operational noise
Solution Approach 1:
A non-magnetic resin member is introduced as an intermediary substance that fills the gap between the rotor magnet and stator teeth. This resin member prevents foreign materials from intruding into the gap while maintaining the simplified motor structure, thus resolving the contradiction between structural simplicity and operational reliability
2Device complexity
If leakage flux is not controlled, then the motor design is simpler, but foreign materials are attracted and cause operational noise
Solution Approach 1:
The non-magnetic resin member acts as a mediator that blocks the path of leakage flux, preventing it from attracting foreign materials. By filling the gap with this resin member, the design maintains simplicity while effectively reducing the harmful effects of foreign material attraction
Solution Approach 2:
The resin member functions as a flexible filling material that conforms to the gap geometry, creating a barrier that prevents both foreign material intrusion and leakage flux exposure, thus addressing the harmful effects without complicating the design
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
The solution effectively minimizes leakage flux and prevents the intrusion of foreign materials, enhancing the motor's operational reliability and productivity by integrating the yoke and rotor magnet through injection molding.
Implementation Method 1
leakage flux generated in the outer rotor motor 9 is discussed with reference to Figs. 11 and 12
Implementation Method 2
the rotor magnet 126 is formed from a plastic magnet made by binding magnetic powder by resin
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
An outer rotor motor (1) comprises a rotor (12) rotating about an axis (A1), and a fixed stator (14). Provided over the inner peripheral surface of a cylindrical part (122c) of a fan motor connecting resin member (12) are a ring-shaped yoke (124), a ring-shaped rotor magnet (126) fixed to a fixing slot defined in the radially inner surface of the yoke (124), and yokes (128) fixed to fixing slots defined in a radially inner surface (126i) of the rotor magnet (126). The rotor magnet (126) is so magnetized that magnetic poles alternately change in a circumferential direction. The yoke (124) covers a radially outer surface (126e) of the rotor magnet (126), and parts on a radially outer side of an axially upper surface (126u) and an axially lower surface (126d) of the rotor magnet (126).