Exhaust Purging Control Device for NOx Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional exhaust purging devices for internal combustion engines rely solely on estimated reductant usage, leading to potential over-supply and increased HC emissions and fuel consumption due to variations in reductant usage by the NOx catalyst, which can result in inefficient NOx reduction and excessive reductant discharge.
Innovation Solution
A control device for the exhaust purging system that includes a NOx catalyst and an air-fuel ratio sensor, which calculates the sum of reductant supplied and ends the purge control based on both a predetermined threshold and a downstream air-fuel ratio condition, ensuring efficient NOx reduction without excessive reductant leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If purge control is based solely on estimated reductant usage, then NOx reduction is achieved, but excessive reductant discharge occurs leading to increased HC emissions and fuel consumption
Solution Approach 1:
The system uses feedback from the air-fuel ratio sensor to monitor the actual air-fuel ratio downstream of the NOx catalyst and adjusts purge control accordingly. When the air-fuel ratio reaches the predetermined value indicating sufficient NOx reduction, the control ends automatically, preventing excessive reductant discharge while maintaining reliable NOx reduction.
Solution Approach 2:
The patent replaces the conventional mechanical/estimated-based purge control with a sensor-based detection system. The air-fuel ratio sensor provides real-time feedback that substitutes for indirect estimation, enabling precise control termination when NOx reduction is sufficient, thereby eliminating waste of reductant.
2Reliability
If reductant supply is increased to ensure complete NOx reduction, then NOx reduction reliability improves, but fuel consumption increases
Solution Approach 1:
The air-fuel ratio sensor provides continuous feedback on the exhaust gas composition downstream of the NOx catalyst. The control system uses this feedback to determine when NOx reduction is complete (when air-fuel ratio reaches predetermined value), allowing the system to stop reductant supply at the optimal moment, ensuring complete NOx reduction while minimizing fuel consumption.
Solution Approach 2:
The system dynamically adjusts the air-fuel ratio parameter during purge control based on real-time sensor readings. By monitoring changes in the air-fuel ratio downstream of the catalyst, the system identifies the precise moment when NOx reduction is sufficient and terminates control, optimizing the balance between reduction completeness and fuel efficiency.
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 effectively suppresses excessive reductant discharge and maintains efficient NOx reduction by ending the purge control when the air-fuel ratio downstream of the NOx catalyst reaches a predetermined value, preventing reductant leakage and optimizing fuel consumption.
Implementation Method 1
The NOx catalyst, for example, stores the NOx discharged under lean conditions and reduces the stored NOx during rich operation to therefore purify the exhaust gas
Implementation Method 2
an air-fuel ratio sensor that detects an air-fuel ratio in a downstream portion of the exhaust passage
Data Source
AI summary
The present disclosure relates to ECU for an exhaust purging system comprises: a NOx catalyst provided in an exhaust passage; and a second composite sensor detecting an air-fuel ratio in a downstream of the NOx catalyst, the ECU, which performs a routine of a purge control, calculates the sum of values of the reductant that have been supplied to the NOx catalyst since the start of the routine of the purge control, determines whether the sum is greater than or equal to an end determination threshold, determines whether the air-fuel ratio is less than or equal to a predetermined value, and ends the routine of the purge control in response to an earlier one of a first affirmative determination that the sum is greater than or equal to the end determination threshold and a second affirmative determination that the air-fuel ratio is less than or equal to the predetermined value.