Embedded Permanent Magnet Rotor Cooling and Flux Optimization
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Solution Overview
Problem
Conventional embedded permanent magnet rotary electric machines face issues with reduced magnetic flux due to increased magnetic resistance caused by insulating members covering inner cavity walls and ineffective cooling of permanent magnets, as the heat is radiated to cooling oil through outer yoke portions.
Innovation Solution
The design reduces adhesive usage and cross-sectional area of magnet housing apertures by fixing permanent magnets closer to the outer wall surfaces, forming cooling flow channels that allow coolant to directly contact the inside surfaces of the magnets, thereby reducing magnetic resistance and enhancing cooling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If insulating members are formed to completely cover inner wall surfaces of cavities, then insulation performance is improved, but cross-sectional area of cavities increases and distances between permanent magnets and inner wall surfaces increase, leading to increased magnetic resistance and reduced magnetic flux
Solution Approach 1:
The insulating member is designed with different thicknesses at different locations: thinner at the inner wall surface side (closer to permanent magnets) and thicker at the outer wall surface side. This local quality variation maintains adequate insulation performance while minimizing the increase in cavity cross-sectional area and distance between permanent magnets and inner wall surfaces, thereby reducing magnetic resistance and preserving magnetic flux.
2Device complexity
If cooling flow channels are formed between outer yoke portion and inner yoke portion, then structural cooling path is established, but heat from permanent magnets is radiated to cooling oil through outer yoke portion, resulting in ineffective cooling of permanent magnets
Solution Approach 1:
The cooling flow channels are extracted from the conventional location between yoke portions and repositioned to be formed between the insulating member and the permanent magnets. This extraction creates a direct cooling path that contacts the heat source (permanent magnets) directly, eliminating the thermal resistance introduced by the outer yoke portion and enabling effective heat removal from the permanent magnets.
3Stability of the object's composition
If adhesive is used to fix permanent magnets to inner wall surface of magnet housing apertures, then permanent magnets are securely fixed, but cross-sectional area of magnet housing apertures increases and distances between inner wall surfaces and permanent magnets increase, increasing magnetic resistance
Solution Approach 1:
The adhesive is applied in a controlled manner with specific thickness parameters: a first thickness at the inner wall surface side and a second thickness at the outer wall surface side. By optimizing these thickness parameters, the invention achieves secure fixation of permanent magnets while minimizing the increase in aperture cross-sectional area and distance, thereby reducing magnetic resistance and preserving magnetic flux.
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 configuration effectively suppresses reductions in magnetic flux and improves cooling of permanent magnets by reducing the distance between magnets and the rotor core, allowing for direct coolant contact and efficient heat absorption.
Implementation Method 1
cooling flow channels through which a coolant flows are formed by an inside surface that is positioned on a radially inner side of a surface of the permanent magnets and inside wall surfaces that are positioned on a radially inner side of inner wall surfaces of the magnet housing apertures
Data Source
AI summary
A permanent magnet 21 is housed in a magnet housing aperture 20, an adhesive is disposed only between an outside wall surface 20a that is positioned on a radially outer side of an inner wall surface of the magnet housing aperture 20 and an outside surface 21a that is positioned on a radially outer side of a surface of the permanent magnet 21 such that the permanent magnet 21 is fixed so as to be closer to the outside wall surface 20a, and a cooling flow channel 23 through which a coolant is made to flow is formed by an inside surface 21b that is positioned on a radially inner side of the surface of the permanent magnet 21 and an inside wall surface 20b that is positioned on a radially inner side of the inner wall surface of the magnet housing aperture 20.