Actuating Reducing Agent Dosing Valve via Pressure Drop Estimation
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Solution Overview
Problem
Existing reducing agent dosing systems for internal combustion engine exhaust systems face inaccuracies in reducing agent quantity due to pressure drop oscillations and delayed pressure sensor responses, leading to deviations in the actual dosed quantity from the intended amount.
Innovation Solution
The formation of actuation signals for the reducing agent dosing valve is made dependent on estimated values for the influence of injection pressure drops, using data stored in a control unit to adjust actuation durations and quantities, ensuring more accurate dosing by accounting for pressure drop offsets and delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the reducing agent dosing valve is actuated with opening action to dose reducing agent, then the reducing agent quantity is increased, but the injection pressure drops causing inaccurate dosing
Solution Approach 1:
The control unit calculates an estimated value for the injection pressure drop before the actual dosing occurs. This preliminary estimation allows the system to compensate for the pressure drop that will happen when the valve opens, ensuring accurate dosing by adjusting the actuation signal in advance based on the expected pressure reduction.
Solution Approach 2:
The system uses feedback from pressure sensors to monitor the actual injection pressure and compares it with the estimated pressure drop. Based on this feedback, the control unit adjusts the actuation signals to compensate for deviations, ensuring the reducing agent quantity matches the intended dose despite pressure variations.
2Device complexity
If a pressure sensor is mounted remotely at the pump to measure pressure, then the device complexity is reduced, but the measurement precision is degraded due to propagation time delay
Solution Approach 1:
The control unit performs preliminary calculations to estimate the pressure drop at the dosing valve based on known system characteristics and pump output, rather than waiting for the pressure sensor to detect the actual pressure change. This estimation compensates for the time delay in pressure signal propagation from the remote sensor.
Solution Approach 2:
The system introduces an intermediary calculation layer that estimates the pressure drop between the pump and the dosing valve. This intermediary estimation model bridges the gap caused by the remote sensor placement, allowing the system to account for pressure variations without requiring a sensor directly at the valve.
3Ease of operation
If the actuation signal is formed based on nominal pressure only, then the ease of operation is improved, but the manufacturing precision is degraded due to dosing deviations
Solution Approach 1:
The control unit performs preliminary estimation of the pressure drop effect on dosing accuracy. By calculating the expected pressure reduction before actuation, the system can adjust the actuation signal in advance, maintaining simple operation while achieving precise dosing that accounts for pressure variations.
Solution Approach 2:
The system dynamically adjusts the actuation signal parameters based on estimated pressure drop values. Instead of using a fixed nominal pressure, the control unit modifies the actuation duration or intensity according to the calculated pressure reduction, thereby maintaining dosing precision while keeping the control mechanism relatively simple.
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 approach enhances the accuracy of reducing agent dosing by compensating for pressure drop-induced deviations, ensuring the intended reducing agent quantity is injected, thereby improving the functionality of the exhaust-gas purification system.
Implementation Method 1
a pump which generates an injection pressure at the feed connector
Implementation Method 2
the reducing agent dosing valve reacts with an opening action which takes place as a result of hydraulic connection of the feed connector to the injection opening
Data Source
AI summary
A reducing agent dosing valve (24) on an exhaust system (12) of an internal combustion engine (10), having a pump (32) which generates an injection pressure (p_24), and having a control unit (14) which actuates the reducing agent dosing valve (24) with actuation signals is presented, wherein the actuation signals are formed in a manner dependent on a reducing agent pressure (p_36) prevailing at the pump side. The method is distinguished by the fact that the actuation signals are formed additionally in a manner dependent on at least one estimated value for an influence of a drop in the injection pressure (p_24), which occurs upon the opening of the reducing agent dosing valve (24), on the injected reducing agent quantity.