SCR System Urea Defrosting Warm Air Priority Control
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Solution Overview
Problem
The urea aqueous solution in SCR systems for diesel vehicles often freezes in cold conditions, leading to delayed defrosting and disruption of engine warm air and cabin heating, with existing solutions like tank heaters facing inefficiencies due to low engine cooling water temperatures and potential misdiagnosis of faulty components.
Innovation Solution
An SCR system with a temperature sensor and tank heater valve configuration that prioritizes warm air heating by only activating the tank heater when the engine cooling water reaches a certain temperature, using a defrosting permission value map to adjust this threshold based on outdoor temperatures, ensuring uninterrupted engine and cabin heating while efficiently defrosting the urea solution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the tank heater is activated immediately at engine start to defrost the urea aqueous solution, then the defrosting speed is improved, but the engine warm air supply and cabin heating are interrupted
Solution Approach 1:
The control unit checks whether the cooling water temperature has reached a predetermined temperature (e.g., 50°C) before permitting tank heater activation. This preliminary temperature check ensures that the cooling water has sufficient heat capacity to defrost the urea solution without compromising engine warm air supply or cabin heating, thereby preventing interruption of these critical functions while still enabling timely defrosting
2Temperature
If the tank heater valve is opened when cooling water temperature is low, then the urea aqueous solution can be defrosted, but the cooling water temperature cannot increase and cabin heating is delayed
Solution Approach 1:
The control unit continuously monitors the cooling water temperature and uses this feedback to determine whether to permit tank heater activation. By checking if the cooling water temperature has reached the predetermined threshold before allowing heater operation, the system ensures that defrosting only occurs when sufficient thermal energy is available, preventing delays in cabin heating while still achieving timely urea solution defrosting
3Reliability
If the tank heater operates continuously to ensure complete defrosting, then the defrosting reliability is improved, but the risk of misdiagnosis of tank heater faults increases
Solution Approach 1:
The system dynamically adjusts the tank heater operation based on real-time cooling water temperature conditions. The heater is permitted to operate only when the cooling water temperature exceeds the predetermined threshold, creating a conditional and adaptive defrosting strategy. This dynamic approach ensures reliable defrosting under appropriate conditions while preventing false fault diagnoses that would occur with continuous or unconditional heater operation
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 system effectively defrosts the urea solution without interrupting engine or cabin heating, reducing defrosting time and preventing misdiagnosis of tank heater issues, while ensuring timely urea injection even in cold starts, and allowing immediate injection in warm conditions.
Implementation Method 1
a temperature sensor provided in the urea aqueous solution tank and configured to detect the temperature of the urea aqueous solution
Implementation Method 2
The tank heater can defrost the urea aqueous solution by exchanging heat between the cooling water and the urea aqueous solution
Implementation Method 3
reduces and purifies NOx on an SCR catalyst by the ammonia
Data Source
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AI summary
Provided is an SCR system that can defrost the urea aqueous solution without interruption of warm air of an engine or heating of a vehicle cabin. The SCR system includes a defrosting control unit 1 configured to open a tank heater valve 124 at the time of starting the engine and close the tank heater valve 124 when the temperature of the urea aqueous solution detected by a temperature sensor 121 reaches a predetermined defrosting completion determination value, and a warm air priority control unit 2 configured to prohibit the opening of the tank heater valve 124 by the defrosting control unit 1 when the temperature of the cooling water is less than a predetermined defrosting permission value and permit the opening of the tank heater valve 124 by the defrosting control unit 1 when the temperature of the cooling water is equal to or more than the defrosting permission value.