Electric Machine Bearing Cooling via Housing Return Flow
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Solution Overview
Problem
The rotor shaft and pivot bearing in electric machines for vehicles heat up significantly during operation, leading to bearing clearance issues and reduced service life due to heat-related expansions, which affects the reliability of the rotary bearing.
Innovation Solution
A coolant supply system is implemented where the free space between the rotor/stator arrangement and the electric machine housing wall is supplied with coolant, effectively cooling the pivot bearing on both sides, with a design that includes a coolant connection, catch contour, and overflow mechanism to prevent coolant backflow and enhance cooling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pivot bearing is cooled only from one side (from the electric machine compartment), then the cooling system is simple, but the cooling effectiveness is insufficient leading to bearing clearance consumption and reduced service life
Solution Approach 1:
The cooling system is segmented into two independent coolant supply paths: one from the electric machine compartment and another from the free space. This segmentation allows each path to contribute to cooling the pivot bearing, improving overall cooling effectiveness and bearing reliability without requiring a completely new complex system
Solution Approach 2:
The coolant connection is integrated into the existing housing structure, with the inlet opening into the free space and the outlet returning coolant to the electric machine compartment. This nested integration allows the additional cooling function to be added within the existing structural framework, minimizing overall system complexity
2Temperature
If coolant is supplied into the free space to cool the pivot bearing, then cooling effectiveness improves, but the risk of coolant backflow into the bearing increases
Solution Approach 1:
The outlet of the coolant connection is positioned at a specific location below the pivot bearing, creating a local coolant return path that prevents backflow into the bearing. This localized design ensures coolant flows in the intended direction while maintaining effective cooling of the bearing from the free space
Solution Approach 2:
The coolant connection design creates a gravitational equipotential path where coolant naturally flows from the inlet into the free space, cools the bearing, and returns through the outlet below the bearing. This gravitational flow path eliminates the need for additional pressure control mechanisms to prevent backflow
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 system ensures reliable operation of the rotary bearing by maintaining effective cooling of the pivot bearing, reducing heat-related expansions and improving bearing service life and stability.
Implementation Method 1
The free space is thus additionally supplied with coolant to ensure effective cooling of the pivot bearing
Implementation Method 2
The coolant can be guided through the inlet into the free space under the effect of gravity. The coolant can then be returned from the free space to the electric machine chamber via the outlet under the effect of gravity
Implementation Method 3
The coolant can be guided through the inlet into the free space under the effect of gravity. The coolant can then be returned from the free space to the electric machine chamber via the outlet under the effect of gravity
Data Source
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AI summary
The invention relates to a coolant supply system for an electric machine, in which electric machine a free electric-machine space (27) is provided between the rotor/stator assembly and an electric-machine housing wall (9) with respect to the axial direction, into which electric-machine space coolant can be introduced, in particular for stator cooling. The electric machine has a rotor-shaft bearing assembly, in which the rotor shaft (6) is rotationally mounted in a hub portion (31) of the electric-machine housing wall (9) by means of a rotary bearing (15), the bearing opening being sealed with respect to the housing exterior by means of a sealing element (33), such that a free space (59) is formed between the rotary bearing (15) and the sealing element. According to the invention, the electric-machine housing wall (9) has a coolant connection (61, 63), by means of which coolant can be led from the electric-machine space (27) into the free space (59).