Electric drive unit with a heat exchanger that is formed by disks having a disk spring portion and which are received into a bore in a rotor shaft of an electric motor
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Solution Overview
Problem
Existing electric motor heat exchanger configurations are costly and difficult to manufacture due to the need for close tolerances between the heat exchanger and the rotor shaft, which complicates the cooling process and increases production costs.
Innovation Solution
The electric drive unit incorporates a heat exchanger with disk spring portions that are press-fit into the rotor shaft, featuring coolant apertures to form concentric passages, allowing for flexible engagement and reduced manufacturing complexity by utilizing disc spring portions that deflect to ensure contact with the rotor shaft, even with variations in diameter and cylindricity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the heat exchanger is designed to contact the rotor shaft interior surface throughout its entire length, then heat transfer efficiency is improved, but manufacturing complexity and cost increase due to close tolerance requirements
Solution Approach 1:
The heat exchanger is divided into multiple discrete plates stacked together, with each plate having an outer surface that contacts the rotor shaft. This segmentation allows each plate to be manufactured independently with standard tolerances, avoiding the need for a single complex component with close tolerances throughout its entire length.
Solution Approach 2:
The invention changes the physical state of the heat exchanger plates by utilizing thermal expansion. The plates are installed at a first temperature and expand when heated to an operating temperature, causing their outer surfaces to contact the rotor shaft interior surface. This parameter change (temperature) enables heat transfer efficiency improvement without requiring close manufacturing tolerances.
2Temperature
If close tolerances are specified between the heat exchanger and rotor shaft, then heat transfer performance is improved, but production cost increases
Solution Approach 1:
The invention utilizes thermal expansion by installing the heat exchanger plates at a lower temperature and allowing them to expand to contact the rotor shaft at operating temperature. This parameter change eliminates the need for expensive close tolerance manufacturing while maintaining effective heat transfer performance.
Solution Approach 2:
The invention incorporates a press-fit mechanism that provides preliminary contact force between the heat exchanger plates and rotor shaft at installation temperature. This beforehand cushioning ensures that when the plates expand due to thermal heating, they maintain consistent contact with the rotor shaft, compensating for any dimensional variations without requiring close tolerances.
3Temperature
If the heat exchanger plates are press-fit into the rotor shaft, then contact and heat transfer are improved, but assembly complexity increases
Solution Approach 1:
The heat exchanger is segmented into multiple plates that are individually press-fit into the rotor shaft. This segmentation simplifies the assembly process compared to installing a single large heat exchanger component, as each plate can be independently positioned and secured without complex alignment requirements.
Solution Approach 2:
The invention utilizes the thermal expansion parameter change to simplify assembly. The plates are installed at a first temperature with press-fit contact, and when heated to operating temperature, they automatically expand to improve contact quality. This eliminates the need for complex adjustment mechanisms or high-precision alignment procedures during 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
This design enhances heat transfer efficiency and manufacturing simplicity by allowing the heat exchanger plates to thermally expand and maintain contact with the rotor shaft, reducing the need for precise tolerances and lowering production costs while maintaining effective cooling performance.
Implementation Method 1
each disc spring portion is deflected from a pre-installation state
Implementation Method 2
allowing the heat exchanger plates to thermally expand and maintain contact with the rotor shaft
Implementation Method 3
cool components of the electric motor with a flow of liquid coolant, such as the rotor of the electric motor
Data Source
AI summary
An electric drive unit that includes an electric motor having a rotor with a rotor shaft and a heat exchanger that is received in the rotor shaft. The heat exchanger has a plurality of heat exchanger plates, each of which having a hub, a rim member, and disc spring portion that interconnects the hub and the rib member. Each disk spring portion defines a plurality of coolant apertures. The heat exchanger plates are press-fit to the rotor shaft such that each disc spring portion is deflected from a pre-installation state, and each rim member is engaged to an interior surface of the rotor shaft while being spaced apart from adjacent rim members along a rotational axis of the rotor. A first coolant passage is disposed through the hubs of the plates. The coolant apertures in the heat exchanger plates cooperate to form a plurality of second coolant passages.