Engine Throttle Control for EGR Misfire Prevention
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Solution Overview
Problem
Internal combustion engines with EGR devices face misfires due to excessive EGR gas in the intake passage during deceleration and reacceleration, as existing techniques fail to effectively manage EGR gas recirculation, leading to combustion deterioration and potential misfires.
Innovation Solution
A control apparatus with an intake air quantity information determining arrangement, normal combustion threshold value computing, and misfire-avoidance control arrangement that estimates cylinder-inflow EGR gas quantity and controls the throttle opening degree to maintain intake air quantity above the normal combustion threshold, preventing misfires by promoting EGR gas scavenging during fuel cut operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the throttle valve is closed at a slower speed to limit combustion deterioration, then misfire is reduced, but the intake air quantity decreases below the normal combustion threshold when large EGR gas is already present in the intake passage
Solution Approach 1:
The control apparatus performs preliminary action by detecting when EGR gas quantity in the intake passage exceeds a predetermined threshold before deceleration occurs. When this condition is detected, the system pre-opens the throttle valve to maintain intake air quantity above the normal combustion threshold, preventing the situation where intake air quantity would otherwise drop below the threshold during deceleration with high EGR gas presence.
2Quantity of substance
If the EGR valve is closed to stop EGR gas recirculation, then EGR gas accumulation in the intake passage is reduced, but combustion efficiency deteriorates due to insufficient EGR gas for knocking reduction and emission control
Solution Approach 1:
The control apparatus employs feedback by continuously monitoring both EGR valve opening degree and throttle valve opening degree, and adjusting the throttle valve opening based on the detected EGR gas quantity in the intake passage. The system uses this feedback to determine when to activate misfire-avoidance control, creating a closed-loop control system that balances EGR gas management with combustion quality maintenance.
Solution Approach 2:
The system dynamically adjusts the throttle valve opening degree based on real-time operating conditions, including engine speed, load, and detected EGR gas quantity. Rather than using fixed throttle positions, the control apparatus continuously modifies throttle opening to maintain intake air quantity above the normal combustion threshold while accommodating varying EGR gas conditions during different engine operating phases.
3Reliability
If the throttle valve opening degree is increased to maintain intake air quantity above the threshold, then misfire is prevented, but torque output decreases due to reduced throttle restriction
Solution Approach 1:
The control apparatus applies partial action by activating misfire-avoidance control only under specific conditions when EGR gas quantity exceeds the predetermined threshold and the throttle valve is in a closing state. Rather than continuously adjusting the throttle valve, the system intervenes selectively to maintain intake air quantity above the normal combustion threshold only when necessary, minimizing the impact on torque output while preventing misfire.
Data Source
AI summary
An intake air quantity information determining arrangement senses or computes one of an intake air quantity and a torque of an internal combustion engine as intake air quantity information. A misfire-avoidance control arrangement executes a misfire-avoidance control operation, which avoids misfire by controlling a throttle opening degree of a throttle valve such that a value of the intake air quantity information does not decrease below a normal combustion threshold value.