Segmented Rotor Heat Sink for Easier Hollow-Shaft Cooling
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Solution Overview
Problem
Existing electric motor cooling configurations, such as those using heat exchangers inside hollow shafts, are costly and difficult to manufacture due to the need for close tolerances between the heat exchanger and the shaft for effective heat transfer.
Innovation Solution
An electric drive unit with a rotor heat sink formed of heat sink elements, each comprising a central hub, an outer rim, and first rib members, which are integrally formed and arranged to create discrete coolant return passages, allowing for improved heat transfer and reduced manufacturing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a heat exchanger is used inside a hollow shaft with continuous contact throughout the entire length, then heat transfer efficiency is maximized, but manufacturing cost and difficulty increase due to close tolerance requirements
Solution Approach 1:
The heat exchanger is divided into multiple discrete heat sink elements arranged in series within the hollow shaft. Each element has interrupted thermal contact with the shaft, creating discrete contact points rather than continuous contact. This segmentation maintains effective heat transfer while significantly reducing manufacturing tolerance requirements and assembly complexity.
2Temperature
If close tolerances are maintained between the heat exchanger and hollow shaft, then heat transfer is maximized, but device complexity and manufacturing precision requirements increase
Solution Approach 1:
By segmenting the heat exchanger into discrete elements with interrupted contact, the patent eliminates the need for continuous close tolerances. Each element can be manufactured and assembled independently with relaxed tolerance requirements, while still achieving effective heat transfer through the discrete contact points.
Solution Approach 2:
The heat sink elements are designed to concentrate thermal contact at specific localized regions rather than requiring uniform contact throughout. This allows for non-uniform tolerance distribution, focusing precision only where thermally critical while allowing greater tolerance elsewhere in the assembly.
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 use of heat sink elements with discrete coolant return passages enhances heat transfer efficiency and reduces manufacturing costs by eliminating the need for close tolerances between the heat exchanger and the shaft, while also simplifying the manufacturing process.
Implementation Method 1
The flow of liquid coolant is input to the heat exchanger at a first end of the rotor to a first passage... to maximize potential heat transfer between the hollow shaft and the heat exchanger
Data Source
AI summary
An electric drive unit that includes an electric motor having motor output shaft and a heat sink that is received therein. The heat sink is comprises of a plurality of discrete heat sink elements that are stacked together and inserted into the motor output shaft. The heat sink elements have central hubs that cooperate to form a coolant supply passage that extends centrally through the heat sink. Each of the heat sink elements defines a plurality of discrete coolant return passages that are relatively shorter in length than the central hubs so that a void annular space is formed between the coolant return passages of adjacent heat sink elements.