Rotor Core Thickness Variation for Cooling and Strength
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Solution Overview
Problem
Conventional rotors with coolant flow paths experience a decrease in strength due to stress applied at thin sections when rotated at high speeds, particularly near the permanent magnet insertion area, leading to reduced rotor core strength.
Innovation Solution
The rotor design incorporates electric steel plates with varying thicknesses, featuring a first thicker portion and a second thinner portion extending radially to form a coolant flow path, which is work-hardened to maintain strength and reduce stress on thin sections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a slit (hole portion) that extends in the radial direction is formed in the electric steel plate to form a coolant flow path, then the coolant can flow through the rotor core to cool the permanent magnet, but the strength of the rotor core is decreased due to increased stress on thin sections
Solution Approach 1:
The electric steel plate is designed with different thicknesses in different regions: a first thickness in the radial direction for structural strength, and a second thickness (forming a groove) for coolant flow. This local differentiation allows the plate to simultaneously provide mechanical strength where needed and coolant passage where required, resolving the contradiction between cooling effectiveness and structural integrity
Solution Approach 2:
Instead of forming a through-hole in the radial direction (one-dimensional solution), the invention creates a groove structure that utilizes the thickness dimension (third dimension) of the electric steel plate. The groove extends in the rotational axis direction with a depth that is a fraction of the plate thickness, transforming the problem from a radial penetration issue to a multi-dimensional structural design that maintains strength while enabling coolant flow
2Productivity
If the rotor is rotated at high speed, then the cooling effect is improved, but the stress on thin sections of the rotor core is increased, leading to decreased strength
Solution Approach 1:
The electric steel plate structure provides localized thickness variation: thicker sections maintain structural strength to withstand high-speed rotation stresses, while the grooved sections provide coolant flow paths for effective cooling. This spatial differentiation of thickness allows the rotor to simultaneously achieve high-speed rotation capability and efficient cooling
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 the decrease in rotor core strength even with a coolant flow path, allowing for stable high-speed rotation while efficiently cooling the permanent magnets, thus preventing demagnetization due to temperature increases.
Implementation Method 1
a coolant supply port that supplies a coolant to the rotor core is provided in the shaft, and at least two electric steel plates of the plurality of electric steel plates each include a first portion that has a first thickness in a rotational axis direction and a second portion that has a second thickness in the rotational axis direction, which is thinner than the first portion, the second portion extending in a radial direction and configuring a flow path through which the coolant supplied from the coolant supply port of the shaft flows
Data Source
AI summary
A rotor that includes a shaft; a rotor core that is attached to the shaft and that is configured of a plurality of electric steel plates that are stacked; and a permanent magnet that is embedded in the rotor core, wherein: a coolant supply port that supplies a coolant to the rotor core is provided in the shaft, and at least two electric steel plates of the plurality of electric steel plates each include a first portion that has a first thickness in a rotational axis direction and a second portion that has a second thickness in the rotational axis direction, which is thinner than the first portion, the second portion extending in a radial direction and configuring a flow path through which the coolant supplied from the coolant supply port of the shaft flows.