Rotor Airflow and Pump Structure to Keep Oil Out of the Air Gap
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Solution Overview
Problem
Existing rotating electric machines face challenges in preventing cooling oil from entering the air gap, which leads to agitation loss, particularly at low and medium motor rotation speeds, and high-speed rotation increases pump loss.
Innovation Solution
A rotating electric machine design incorporating a rotor with a pump synchronized to the shaft, forming an air flow passage between the rotor and stator, and shaft flow passages that generate a differential pressure to prevent cooling oil entry into the air gap, utilizing a centrifugal force to circulate air and reduce agitation loss across various speed ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple straight flow passage is used to generate pressure for cooling oil entry prevention, then the structure is simple, but the agitation loss cannot be reduced in low and medium speed areas
Solution Approach 1:
The patent applies the dynamics principle by introducing a pump mechanism that rotates synchronously with the rotor shaft. This dynamic structure actively generates differential pressure between the high-pressure chamber and low-pressure chamber, enabling effective prevention of cooling oil entry into the air gap across all speed ranges, particularly improving performance in low and medium speed areas where passive pressure generation is insufficient.
2Stress or pressure
If high-speed rotation is used to generate sufficient pressure for cooling oil entry prevention, then pressure is sufficient, but pump loss increases
Solution Approach 1:
The patent applies segmentation by dividing the pump into multiple suction ports and discharge ports arranged circumferentially. This segmentation allows the pump to maintain effective differential pressure generation at lower speeds by utilizing multiple entry and exit points for the cooling oil, reducing the reliance on high-speed rotation and thereby decreasing pump losses while maintaining sufficient pressure.
Solution Approach 2:
The patent introduces a pressure equalization chamber as an intermediary between the suction and discharge sides of the pump. This intermediary structure helps regulate the differential pressure more efficiently, allowing the system to achieve sufficient pressure for cooling oil entry prevention without requiring excessive pump speed, thus reducing pump losses.
3Temperature
If cooling oil is discharged into the motor housing without air gap prevention, then cooling performance is high, but agitation loss occurs
Solution Approach 1:
The patent applies the taking out principle by extracting the cooling oil from the air gap region through the pump system. The pump actively removes cooling oil that would otherwise enter the air gap and cause agitation loss, while maintaining the cooling function by circulating the oil through dedicated channels in the rotor and stator, thus separating the cooling function from the air gap region.
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 prevents cooling oil from entering the air gap, reducing agitation loss and pump loss across a wide range of motor speeds, thereby enhancing cooling efficiency and motor performance.
Implementation Method 1
a differential pressure is generated between a high-pressure chamber and a low-pressure chamber
Implementation Method 2
the housing forms an air flow passage between the rotor and the stator, the shaft includes a shaft flow passage that communicates with the air flow passage
Data Source
AI summary
A rotating electric machine includes a rotor including a rotor core configured by laminating a plurality of electromagnetic steel plates and a shaft that supports the rotor core, a stator that faces the rotor via an air gap that is a predetermined space, on a radially outer side of the rotor, and a housing that houses the rotor and the stator, in which the housing forms an air flow passage between the rotor and the stator, the shaft includes a shaft flow passage that communicates with the air flow passage, and the rotor includes a pump that is coupled to the shaft and is synchronized with rotation of the shaft and a radial direction flow passage that communicates the shaft flow passage with the air gap.