Reducing Agent Unfreezing Control for Exhaust Purification
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Solution Overview
Problem
In cold climates, the aqueous urea solution used as a reducing agent in exhaust purifying apparatuses for internal combustion engines can freeze, leading to inadequate NOX purification when the engine is not started for an extended period, as unfreezing control may not be initiated promptly upon startup.
Innovation Solution
A control apparatus and method that includes speed detection, unfreezing necessity determination, unfreezing time calculation, and injection permitting means, which determine the need for unfreezing based on engine speed and atmospheric temperature, using a heating device to unfreeze the reducing agent before allowing injection control in the exhaust passage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the aqueous urea solution is adjusted to have a concentration giving the lowest freeze temperature, then the freezing resistance of the reducing agent is improved, but the freeze temperature remains at least -11 degrees and the liquid reducing agent may still be frozen in cold climate areas
Solution Approach 1:
The control apparatus determines the necessity of unfreezing before injection control is executed. By calculating the necessary unfreezing time in advance and comparing it with the time elapsed since engine startup, the system ensures unfreezing control is performed before injection begins, preventing purification control failures.
Solution Approach 2:
The control apparatus continuously monitors engine startup time and calculates unfreezing time based on stored temperature-time characteristics. This feedback mechanism allows the system to adjust injection control timing dynamically, ensuring injection only occurs after the reducing agent has sufficiently thawed.
2Device complexity
If unfreezing control is determined based on atmospheric temperature at startup switch turn-on, then the control simplicity is improved, but when the engine is not started for a long time, unfreezing control may not be performed even when necessary
Solution Approach 1:
The control apparatus determines the necessity of unfreezing as a preliminary step before permitting injection control. By establishing this determination logic that considers both temperature and startup duration, the system proactively identifies when unfreezing is needed and executes it before injection begins.
Solution Approach 2:
The control apparatus dynamically adjusts injection control permission based on real-time conditions. The injection permitting means monitors whether the elapsed time since startup exceeds the calculated unfreezing time, and only permits injection when this condition is met, making the control adaptive to varying environmental conditions.
3Productivity
If injection control is started immediately after startup switch turn-on, then the productivity is improved, but when the reducing agent is frozen, purification control cannot be performed appropriately
Solution Approach 1:
The control apparatus performs unfreezing determination and time calculation as preliminary actions before enabling injection control. This ensures that the reducing agent is properly prepared (unfrozen) before injection begins, guaranteeing purification effectiveness while minimizing delay through efficient time management.
Solution Approach 2:
The control apparatus calculates the necessary unfreezing time in advance and uses this information to determine when injection can safely begin. By rushing through the unfreezing process efficiently (when needed) and then immediately permitting injection, the system minimizes overall delay while ensuring proper preparation.
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
Ensures that the reducing agent is properly unfrozen before initiating injection control, ensuring efficient NOX purification even when the engine is not started for a long time, by calculating the necessary unfreezing time and permitting injection control only when the agent is thawed.
Implementation Method 1
unfreezes the frozen liquid reducing agent using a heating device
Data Source
AI summary
The control method for reducing agent supply apparatuses, when a liquid reducing agent is frozen, unfreezes the frozen liquid reducing agent using a heating device and enables the injection control of the liquid reducing agent in an exhaust passage of the internal combustion engine. The control method includes determining the necessity of unfreezing of the liquid reducing agent and calculating the necessary time required for the unfreezing when the speed of the internal combustion engine exceeds a predetermined threshold during startup of the internal combustion engine and permitting the injection control of the liquid reducing agent when the unfreezing is not necessary or the unfreezing is completed.