Rotor Coolant Flow Path Design for Uniform Magnet Cooling
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Solution Overview
Problem
Existing rotary electric machine rotors face challenges in uniformly cooling high-temperature magnet portions without degrading the strength of slit-formed steel plates due to centrifugal forces during rotation, and existing cooling methods often result in inadequate temperature reduction across the rotor core.
Innovation Solution
A rotor design featuring a coolant flow path with a first flow passage extending along the axial direction near the magnet and a second flow passage connecting the shaft coolant supply to the first passage, formed by overlapping slits in steel plates with different radial positions, ensuring uniform cooling and rotational symmetry to maintain steel plate strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a coolant flow path is formed by elongated slits in the rotor core extending from the shaft toward the magnets, then the cooling effect on magnets is improved, but the centrifugal force during rotation increases the stress on the slit-formed steel plates, causing strength degradation
Solution Approach 1:
The coolant flow path is divided into multiple segments: a first coolant flow path extending from the shaft to the magnet, and a second coolant flow path extending from the shaft to the opposite end of the magnet. This segmentation allows coolant to reach different portions of the magnet independently, improving cooling effectiveness while distributing the structural stress of slits across multiple shorter paths rather than one long path, thereby reducing centrifugal stress on the steel plates.
2Device complexity
If a single coolant flow path extends through the entire rotor core from inner periphery to outer periphery, then the structure is simple, but the cooling effectiveness is insufficient due to temperature increase of coolant along the flow path
Solution Approach 1:
The coolant flow path is segmented into multiple independent paths (first and second coolant flow paths) that branch from the shaft and terminate at different axial locations. This segmentation prevents the cumulative temperature increase that would occur in a single long flow path, as each segment carries coolant over a shorter distance. The increased structural complexity from multiple paths is justified by the significant improvement in cooling effectiveness.
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 design effectively cools high-temperature magnet portions with lower-temperature coolant while preventing strength degradation of the steel plates, achieving uniform cooling and improved magnet performance without compromising the rotor's structural integrity.
Implementation Method 1
the centrifugal force during rotation of the rotor increases the resulting stress applied to the slit-formed portion of the electromagnetic steel plates
Implementation Method 2
a coolant received from a shaft at an axially central portion of a rotor core is guided toward magnets and then is caused to flow to opposite ends of the rotor core in order to cool the magnets in the rotor core
Implementation Method 3
Magnets, which are provided in a rotor core to extend along an axial direction of the rotor core, are apt to have a high temperature due to a heat accumulation at an axially central portion of the rotor core
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
A rotor (14) includes a shaft having a coolant flow passage and a coolant supply port, a rotor core (24) fixed on the shaft and formed of laminated steel plates, and a magnet set (32) provided in the rotor core (24) to extend along an axial direction thereof. The rotor core (24) has a first flow passage (34) provided near the magnet to extend therealong and a second flow passage (36) that connects the coolant supply port (28) of the shaft (22) and the first flow passage (34), thereby constituting a coolant flow path. The second flow passage (36) is formed by overlapping second slits (37) formed in the respective steel plates at an axially intermediate region A of the rotor core (24), the formed position of the second slit (37) being different for each steel plate combined. The first flow passage (34) and the second flow passage (36) join at the axially intermediate region A of the rotor core (24).