Variable Fuel Injection Ratio for NOx Purge Control
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Solution Overview
Problem
In lean burn engines, NOx purification is insufficient when a three-way catalyst is placed upstream of the NOx catalyst, leading to reduced NOx purging efficiency due to decreased reducing agent supply, which worsens fuel economy and exhaust gas purification performance.
Innovation Solution
An exhaust gas purification device with a NOx catalyst in the exhaust passage, a three-way catalyst upstream, and a catalyst temperature detection system that controls fuel injection to vary the main and sub fuel injection ratios based on temperature, ensuring sufficient NOx purging by optimizing the air-fuel ratio and injection timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the three-way catalyst is arranged upstream of the NOx catalyst to ensure early activation, then the exhaust gas purification performance immediately after engine start is improved, but the reducing agent supply to the NOx catalyst decreases during NOx purging, worsening the NOx purification efficiency
Solution Approach 1:
The patent applies dynamics by making the fuel injection quantity variable based on catalyst temperature. The ECU adjusts the fuel injection quantity in the second fuel injection timing according to the detected catalyst temperature, enabling the system to adaptively optimize reducing agent supply to the NOx catalyst during purging operations while maintaining the upstream three-way catalyst configuration for early activation.
2Productivity
If the rich operation time is extended or the air-fuel ratio is made further richer to improve NOx purging, then the NOx purification efficiency is improved, but the fuel economy deteriorates significantly
Solution Approach 1:
The patent applies parameter changes by adjusting the fuel injection quantity based on catalyst temperature parameters. Instead of using fixed rich operation conditions, the system dynamically modifies the air-fuel ratio and fuel injection timing parameters according to the actual catalyst temperature, enabling effective NOx purging while minimizing fuel consumption and avoiding significant deterioration in fuel economy.
3Temperature
If the catalyst temperature increases to improve purification capacity, then the catalytic activity is enhanced, but the amount of reducing agents supplied to the NOx catalyst decreases, lowering the exhaust gas purification performance
Solution Approach 1:
The patent applies feedback by using the catalyst temperature detection means to monitor the actual catalyst temperature and feeding this information back to the ECU. The ECU then adjusts the fuel injection quantity in the second fuel injection timing based on this temperature feedback, ensuring that sufficient reducing agents are supplied to the NOx catalyst even when the catalyst is highly activated, thereby maintaining effective exhaust gas purification performance.
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
Improves NOx purification rates while maintaining fuel economy by ensuring adequate reducing agent supply to the NOx catalyst, even when the three-way catalyst is activated, by adjusting the fuel injection ratio and timing in response to temperature.
Implementation Method 1
a NOx catalyst arranged in an exhaust passage of the internal combustion engine to absorb NOx contained in exhaust gas in lean operation of the internal combustion engine, and discharge and reduce the absorbed NOx in stoichiometric or rich operation
Implementation Method 2
a three-way catalyst arranged upstream of the NOx catalyst in the exhaust passage... a reducing agent such as HC or CO is purified by the three-way catalyst
Implementation Method 3
a catalyst temperature detection means for detecting or estimating the temperature of at least either of the NOx catalyst and the three-way catalyst
Implementation Method 4
a fuel injection means for injecting fuel directly into a combustion chamber of the internal combustion engine... by controlling the fuel injection means to perform main fuel injection and sub fuel injection
Data Source
AI summary
By performing main fuel injection and sub fuel injection to perform rich operation of an engine, NOx purging of a NOx catalyst is carried out, and in the NOx purging, the ratio between the main fuel injection quantity and the sub fuel injection quantity is variably determined, within the range of 5:1 to 2:1 where the ratio of the sub fuel injection quantity is relatively great, such that the ratio of the sub fuel injection quantity is greater as the temperature of a three-way catalyst becomes higher.