EV Drive Unit Cooling Circuit With Ambient Pressure Equalization
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Solution Overview
Problem
Existing cooling systems for electric vehicles face challenges in efficiently managing pressure within the cooling circuits, leading to potential damage from excessive pressure fluctuations and increased costs due to the need for robust components to handle high pressures.
Innovation Solution
A drive unit with a cooling system featuring a pressure equalization assembly that temporarily connects the expansion tank to the ambient environment, using valves and filters to manage pressure differentials and prevent coolant discharge, allowing for a more cost-effective and environmentally friendly design with direct cooling of the electric motor's winding assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a robust cooling system is designed to handle high pressure fluctuations, then reliability is improved, but device complexity and cost increase
Solution Approach 1:
A pressure equalization assembly is introduced as an intermediary component between the cooling circuit and the ambient environment. This assembly includes a pressure equalization valve that opens during pressure spikes to vent excess pressure, and a check valve that prevents backflow. By mediating pressure fluctuations, the system achieves reliable operation without requiring all components to be designed for high pressure resistance, thus reducing overall complexity and cost.
Solution Approach 2:
The cooling system incorporates an expansion tank connected to the cooling circuit, which serves as a cushioning element. The expansion tank absorbs pressure fluctuations and volume changes before they propagate through the system, preventing excessive pressure spikes that would require robust high-pressure components. This beforehand cushioning allows the use of standard-pressure components while maintaining system reliability.
2Reliability
If high-pressure resistant components are used throughout the cooling system, then reliability is improved, but manufacturing cost increases
Solution Approach 1:
The patent applies local quality by differentiating pressure resistance requirements across different system locations. Components directly exposed to pressure fluctuations (such as the cooling circuit near the electric motor) are designed with appropriate pressure resistance, while other components benefit from the pressure equalization assembly that isolates them from high-pressure conditions. This localized approach to pressure resistance optimization reduces manufacturing costs by avoiding unnecessary high-pressure component specifications throughout the entire system.
3Reliability
If the expansion tank is completely sealed, then system reliability is improved, but pressure equalization with ambient environment is prevented
Solution Approach 1:
The pressure equalization assembly implements dynamics by transitioning between sealed and open states based on pressure conditions. The pressure equalization valve remains closed during normal operation to maintain sealing integrity, but automatically opens when pressure exceeds a threshold, allowing the system to adapt to pressure variations. This dynamic behavior enables the system to maintain reliability through sealing while adapting to ambient pressure changes when necessary.
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 reduces the maximum pressures within the cooling circuit, enabling the use of less expensive components, enhances environmental friendliness by minimizing coolant discharge, and ensures effective cooling while maintaining safety and efficiency.
Implementation Method 1
The pressure equalization assembly is configured to enable at least temporarily a fluidic connection between the expansion tank and an ambient environment of the drive unit, in order to at least partially cause a pressure equalization between the expansion tank and the ambient environment
Implementation Method 2
The first cooling circuit is connected to the stator housing inlet and the stator housing outlet so as to enable a direct cooling of the winding assembly
Data Source
AI summary
A drive unit for an electric vehicle including an electric motor, with a stator assembly and rotor assembly, and a cooling system. The stator assembly includes a housing, a stator core having grooves, and a winding assembly. The winding assembly extends through the grooves. The housing includes a housing inlet and outlet connected the grooves. The cooling system includes a first cooling circuit connected to the housing inlet and outlet to enable direct cooling of the winding assembly. The first cooling circuit includes an expansion tank assembly including an expansion tank, at least one inlet, one outlet, and a pressure equalization assembly. The expansion tank is connected to the first cooling circuit via the at least one inlet and the outlet. The pressure equalization assembly enables a connection between the expansion tank and an ambient environment to cause a pressure equalization between the expansion tank and ambient environment.