Ammonia Sensor Correction During SCR Regeneration
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Solution Overview
Problem
Conventional systems for calculating ammonia concentration in exhaust gas from internal combustion engines fail to accurately compute correction values when NOx is present, leading to inaccurate sensor output due to NOx influence, especially during fuel cut conditions.
Innovation Solution
A concentration calculation apparatus and method that utilize a first sensor for detecting ammonia concentration and a second sensor for detecting a specific component in the exhaust gas, with a correction value computation section that calculates the correction value using both sensor outputs during filter regeneration, allowing for ammonia release from the selective reduction catalyst to influence the calculation, enabling computation at arbitrary timings and reducing system complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the correction value is computed at the time of fuel cut assuming no NOx in exhaust gas, then the computation can be performed with simple assumptions, but the correction value cannot be properly computed when NOx remains in the exhaust gas due to EGR configuration
Solution Approach 1:
The invention changes the timing parameter for correction value computation from 'fuel cut time' to 'filter regeneration time'. This parameter change allows the system to operate under conditions where ammonia is actively released from the catalyst, providing a reliable basis for correction computation even when NOx is present in the exhaust gas due to EGR.
Solution Approach 2:
The invention utilizes the ammonia released during filter regeneration as a self-provided calibration source. The ammonia naturally released from the selective reduction catalyst during regeneration serves as the test substance, eliminating the need for external reducing agent injection or special test procedures.
2Ease of operation
If the correction value computation is limited to fuel cut time, then the system maintains simple operation logic, but the frequency of correction updates is reduced and timing flexibility is limited
Solution Approach 1:
The invention establishes periodic correction value computation triggered by filter regeneration events. Since filter regeneration occurs periodically during normal engine operation, this creates regular opportunities for correction value updates, increasing the frequency and timing flexibility of corrections without complicating the overall operation logic.
3Measurement precision
If reducing agent injection is used to compute correction values, then accurate ammonia concentration data can be obtained, but the system requires special processes and additional complexity
Solution Approach 1:
The selective reduction catalyst serves itself by releasing stored ammonia during filter regeneration. This self-release mechanism provides the necessary ammonia concentration variations for correction computation without requiring external reducing agent injection systems or additional control processes.
Solution Approach 2:
The invention extracts and utilizes the ammonia release phenomenon that naturally occurs during filter regeneration. By taking out this existing operational phase and using it for correction computation, the system avoids adding separate reducing agent injection processes while still achieving accurate ammonia concentration measurement.
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 allows for accurate and frequent correction of ammonia concentration calculations, preventing decreases in detection accuracy and eliminating the need for special processes like reducing agent injection, thereby simplifying the system and improving timing flexibility.
Implementation Method 1
When the selective reduction catalyst is brought into a high temperature state, ammonia adsorbed by the selective reduction catalyst is released, and the released ammonia flows to a region downstream of the selective reduction catalyst
Data Source
AI summary
A concentration calculation apparatus, system and method which can compute a correction value for correcting an ammonia sensor output at a timing other than the time of fuel cut. A multi-gas sensor control apparatus (9) of a urea SCR system (1) begins recording (storing) a downstream NOx output value Sn and downstream ammonia output value Sa detected by a multi-gas sensor (8) (S120) when the control apparatus determines that a DPF regeneration process is currently being performed (an affirmative determination in S110). The apparatus (9) computes a downstream ammonia converted value Ca using a peak value of the downstream NOx output value Sn (S170), and calculates a Gain correction coefficient based on a comparison of the downstream converted value Ca and the output value Sa (S180). As a result, the Gain correction coefficient can be computed in accordance with the state of the ammonia detection section (202).