Hollow Rotor Shaft Splines for Improved Coolant Heat Transfer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Hollow rotor shafts for electric motors lack sufficient heat transfer efficiency due to their axially symmetric structure, which complicates the incorporation of heat exchange features and assembly processes, leading to inefficient cooling and potential heat-related losses.
Innovation Solution
A hollow rotor shaft with radially inwardly extending circumferentially spaced splines that increase the surface area for heat transfer, manufactured using a method involving a mandrel with indentations and a flow forming process to capture cooling inserts, enhancing both heat exchange and assembly efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If hollow rotor shafts are formed with axially symmetric structure, then manufacturing is simplified, but heat transfer efficiency is insufficient
Solution Approach 1:
The patent introduces circumferentially spaced splines on the inner surface of the hollow rotor shaft, transforming the axially symmetric structure into an asymmetric one. These splines increase the surface area for heat transfer and create turbulence in the coolant flow, significantly improving heat transfer efficiency while maintaining manufacturing feasibility through flow forming processes
2Ease of manufacture
If hollow rotor shafts are formed without surface area increasing features, then manufacturing is easier, but heat exchange efficiency is insufficient
Solution Approach 1:
The patent combines multiple functions into the spline structure: it serves as both a surface area increasing feature for heat transfer and a structural element that can be integrated with the shaft body. The splines are formed directly during the flow forming process, merging the heat exchange function with the manufacturing process itself, thereby improving heat exchange efficiency without significantly complicating manufacturing
3Temperature
If circumferentially spaced splines are added to increase heat transfer, then heat exchange efficiency is improved, but device complexity increases
Solution Approach 1:
The patent applies splines only to specific portions of the inner surface of the hollow rotor shaft, particularly in regions where heat transfer is most critical. This localized application of surface area increasing features improves heat exchange efficiency while minimizing the overall structural complexity compared to a fully splined design
4Ease of manufacture
If cooling inserts are captured during flow forming, then assembly process is simplified, but manufacturing precision requirements increase
Solution Approach 1:
The patent incorporates cooling inserts into the hollow rotor shaft during the flow forming process itself, rather than assembling them separately afterward. The inserts are preliminarily positioned on mandrels before the flow forming operation, and the forming process captures them in place. This preliminary integration simplifies the final assembly process while the flow forming process itself provides the necessary positioning precision through the mandrel geometry and process control
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 increased surface area and improved coolant mixing significantly enhance heat transfer efficiency, leading to better cooling of the rotor shaft and increased motor efficiency, while simplifying the manufacturing and assembly processes.
Implementation Method 1
Each of the splines is configured to provide a heat exchanging structure for transferring heat from the rotor shaft to the coolant
Implementation Method 2
The increased surface area and improved coolant mixing significantly enhance heat transfer efficiency
Data Source
AI summary
A rotor shaft for an electric motor includes an axially extending tubular body having an inner circumferential surface defining a hollow interior thereof with at least a portion of the hollow interior configured to receive a coolant therein. A plurality of circumferentially spaced splines extends radially inwardly from the inner circumferential surface into the portion of the hollow interior configured to receive the coolant therein. Each of the splines is configured to provide a heat exchanging structure for transferring heat from the rotor shaft to the coolant. The splines are one of integrally formed with the tubular body or provided as inserts captured by the tubular body during a flow forming process.