Corrugated Ring Stator Cooling for Thermal Expansion
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Solution Overview
Problem
The existing electric machine systems face issues with thermal expansion and contraction, leading to a loosening of press fits and increased temperatures due to heat generation, which can result in inefficient heat removal and potential mechanical failures.
Innovation Solution
The use of corrugated rings between the stator assembly and the outer housing creates a radial gap for fluid transfer, allowing for controlled heat removal while maintaining a secure attachment, accommodating thermal expansion and contraction, and enabling efficient heat transfer through a high percentage of cylindrical surface area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a press fit is used to secure the stator assembly to the housing, then the stator assembly is firmly attached, but thermal expansion and contraction cause loosening of the press fit
Solution Approach 1:
The single press fit connection is segmented into multiple discrete press fit points around the stator assembly circumference. This segmentation allows localized thermal expansion and contraction at each point without compromising the overall attachment integrity, as the distributed connections can independently accommodate dimensional changes.
Solution Approach 2:
The design transitions from a rigid press fit to a compliant press fit by changing the material properties or geometric parameters of the housing or stator assembly. This compliance allows the structure to flex and accommodate thermal expansion and contraction while maintaining secure attachment, preventing loosening that would occur with a completely rigid connection.
2Stability of the object's composition
If the stator assembly is tightly secured to the housing, then mechanical stability is improved, but heat removal efficiency deteriorates
Solution Approach 1:
A thermal interface material or heat transfer medium is introduced as an intermediary between the stator assembly and housing. This intermediary substance fills the gap created by the compliant press fit and provides an efficient thermal conduction path while allowing the mechanical structure to remain compliant for thermal expansion accommodation.
Solution Approach 2:
A flexible thermal interface film or coating is applied to the contact surfaces between the stator assembly and housing. This thin film maintains thermal contact while allowing relative movement due to thermal expansion, ensuring both heat transfer efficiency and mechanical stability under varying thermal conditions.
3Temperature
If corrugated rings are used to create a radial gap for fluid cooling, then heat transfer efficiency is improved, but structural complexity increases
Solution Approach 1:
The corrugated rings serve multiple functions simultaneously: they provide the radial gap for fluid cooling channels, maintain concentricity between the stator assembly and housing, and accommodate thermal expansion through their flexible corrugated structure. This multi-functionality reduces the need for separate components and simplifies the overall design despite the increased local complexity of the corrugated features.
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 ensures a secure connection between the stator and housing while effectively cooling the electric machine, maintaining concentricity during thermal growth and torque application, and enhancing heat transfer efficiency.
Implementation Method 1
a pump configured to transfer a fluid through the gap between the stator assembly and housing to remove heat from at least one of the stator assembly or outer housing
Implementation Method 2
a fluid may be transferred, e.g., pumped via a pump, within the gap to remove heat from the stator assembly and/or housing
Implementation Method 3
the electric machine system may employ a heat exchanger to remove heat from the fluid after the fluid is transferred through the gap between the housing and stator assembly
Data Source
AI summary
In some examples, an electric machine system including an outer housing; a stator assembly within the outer housing; a corrugated ring located between the stator assembly and the outer housing, the corrugated ring defining a gap between the stator assembly and the outer housing; and a pump configured to transfer a fluid through the gap between the stator assembly and housing to remove heat from at least one of the stator assembly or outer housing.