Electric Machine Gearbox Shaft Oil Pumping for Integrated Cooling
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Solution Overview
Problem
Existing arrangements for electric machines and gearboxes face challenges in cooling, particularly in automotive applications, where traditional methods like water cooling and splash lubrication are inefficient and may lead to oil entering the electric machine's air gap, causing drag, and the use of mechanical pumps is costly and prone to failure.
Innovation Solution
The integration of a fluid transportation means that rotates with the shaft, acting as a torque-proof pump to transport fluid along the shaft, eliminating the need for external pumps and ensuring efficient cooling by varying fluid flow with rotation rate, while preventing fluid intrusion into the electric machine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If water cooling is used for the shaft, then cooling efficiency is improved, but risk of water entering the gearbox increases
Solution Approach 1:
The patent extracts the harmful element (water) from the cooling system and replaces it with oil, which is already present in the gearbox environment. This eliminates the risk of water contamination while maintaining effective cooling of the shaft and surrounding components.
Solution Approach 2:
The patent makes the oil serve multiple functions: it acts as both the cooling medium for the shaft and the lubricant for the gearbox. This multi-functional approach eliminates the need for separate water cooling systems and prevents contamination issues.
2Temperature
If splash lubrication is used in the gearbox, then cooling is provided, but volume flow control accuracy deteriorates
Solution Approach 1:
The rotating shaft itself serves as the pump mechanism, using its own rotation to draw oil from the sump and force it through the bore. This self-service approach eliminates the need for external pumps while providing automatic flow control based on rotation speed.
3Ease of operation
If a mechanical pump is added for fluid distribution, then fluid distribution capability is improved, but device complexity and cost increase
Solution Approach 1:
The rotating shaft performs the pumping function itself by utilizing its rotation to create pressure differential that draws oil from the sump and forces it through the bore. This eliminates the need for separate mechanical pumps and reduces system complexity.
Solution Approach 2:
The shaft serves multiple functions simultaneously: it transmits torque, provides structural support, and acts as a pump for oil distribution. This multi-functionality reduces the total number of components needed in the system.
4Temperature
If the shaft rotates faster, then cooling efficiency is improved, but fluid intrusion risk into the air gap increases
Solution Approach 1:
The patent removes the harmful element (water) and replaces it with oil, which is compatible with the gearbox environment. This eliminates the harmful effect of fluid intrusion into the air gap while maintaining effective cooling at high rotation speeds.
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 solution enhances cooling efficiency with increased rotation rates, achieves high power density, and integrates the electric machine and gearbox within a single housing, reducing component costs and preventing fluid intrusion into the electric machine's air gap.
Implementation Method 1
the fluid transportation means rotates with the shaft and transports the fluid, particularly oil, from or to the gearbox-side end of the shaft in axial direction
Implementation Method 2
The cooling device is configured to cool the fluid flowing through the cooling circuit
Data Source
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AI summary
Arrangement (1) comprising an electric machine (2) and a gearbox (3), wherein the gearbox includes at least one shaft (4, 29) - being rotatably coupled with a rotor (5) of the electric machine (2), - having a bore (18, 30) extending axially from a gearbox-side end into the direction of the electric machine (2) and - comprising at least one fluid transportation means (37, 39, 43) configured to transport a fluid through the bore (18, 30) by means of rotating the shaft (4, 29).