Cooling Circuit Passivation for EV Safety
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Solution Overview
Problem
In electrically operated motor vehicles, the cooling circuit's coolant can experience increased electric conductivity due to interactions with components, leading to potential short circuits, electric arcs, and detonating gas formation, posing safety risks.
Innovation Solution
A method involving a comprehensive treatment of the cooling circuit before filling with coolant, including water filling, passivation, and rinsing operations, to prevent or reduce conductivity increases, ensuring the coolant remains ion-free and non-conductive, using ion-free water and a passivating agent like dicarboxylic acids, and sealing to prevent fluid ingress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cooling circuit is filled with coolant without treatment, then the filling process is simple and quick, but the electric conductivity of the coolant increases during operation leading to safety risks
Solution Approach 1:
The cooling circuit is treated with a passivating agent before being filled with coolant. This preliminary treatment creates a protective layer on the inner surfaces of the cooling circuit components, preventing ion detachment and salt release during operation. The method includes water filling, passivation treatment, and rinsing operations that must be completed before the final coolant filling, thereby eliminating safety risks while maintaining operational reliability.
Solution Approach 2:
The passivating agent is applied in advance to counteract the harmful effects of ion detachment and salt release from cooling circuit components. By treating the surfaces beforehand with substances like dicarboxylic acids, the method prevents the increase in electric conductivity that would otherwise occur during operation, directly addressing the safety concern before it can manifest.
2Reliability
If individual components are passivated separately before assembly, then the passivation effect is maintained, but the process becomes more complex and the protective effect may be reduced through contact with air
Solution Approach 1:
Instead of passivating individual components separately before assembly, the method merges all passivation operations into a single integrated process performed on the assembled cooling circuit. The cooling circuit is filled with water, treated with passivating agent, and rinsed in sequence without disassembly, maintaining the protective effect while simplifying the overall process and eliminating exposure to air that would occur during separate component treatment.
Solution Approach 2:
Water serves as an intermediary medium throughout the process. The cooling circuit is filled with water for passivation treatment, then rinsed with water to remove excess passivating agent, and finally the water is displaced by the coolant. This intermediary use of water allows the passivation treatment to be performed effectively on the assembled circuit without direct contact with air that would compromise the protective layer.
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 method simplifies and enhances the filling process while significantly increasing operational safety by maintaining the coolant's conductivity within safe limits, preventing undesirable electrical interactions and ensuring the cooling circuit operates safely.
Implementation Method 1
the cooling circuit is rinsed with ion-free water in such a manner that the ion-free water at least partially displaces the passivating agent out of the cooling circuit
Implementation Method 2
the cooling circuit is filled with a passivating agent in such a manner that during the filling of the cooling circuit with the passivating agent the water is simultaneously displaced out of the cooling circuit
Implementation Method 3
the suction pump is arranged downstream of the outlet connection and is configured to suck fluid out of the cooling circuit through the outlet connection and the inlet connection in the state connected to the cooling circuit
Data Source
AI summary
A method for filling a cooling circuit of a motor vehicle with a coolant may include filling the cooling circuit with ion-free water in a water filling operation, leaving the ion-free water in the cooling circuit for a water duration of action in a water operation of action, displacing the ion-free water out of the cooling circuit via filling the cooling circuit with a passivating agent in a passivating operation, rinsing the cooling circuit with ion-free water such that the ion-free water at least dilutes the passivating agent in the cooling circuit and a liquid including at least one of the ion-free water and the passivating agent remains in the cooling circuit in a rinsing operation, displacing the liquid out of the cooling circuit via filling the cooling circuit with the coolant in a coolant filling operation, and/or fluidically sealing the cooling circuit towards an outside in a sealing operation.