Engine Intake Air Control for Exhaust Gas Recirculation Accuracy
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Solution Overview
Problem
The calculation accuracy of the exhaust gas recirculation ratio in internal combustion engines deteriorates due to deviations in intake air amount detection, especially when the intake air amount sensor fails or there is a disconnection in the exhaust gas recirculation or evaporative fuel passages, leading to misfire or knocking issues.
Innovation Solution
A control apparatus for internal combustion engines that includes rotational speed and intake pressure detection, wide-open intake air amount calculation, theoretical intake air amount calculation, air-fuel ratio correction, and a limit process to ensure the detected intake air amount is within a set lower limit value, enhancing the accuracy of exhaust gas recirculation ratio calculation and engine control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the detected intake air amount is used directly for calculating the exhaust gas recirculation ratio, then the calculation is simple, but the calculation accuracy deteriorates when the intake air amount sensor fails or passages are disconnected
Solution Approach 1:
The control apparatus performs preliminary detection of abnormal conditions (sensor failure, passage disconnection) before they significantly affect control accuracy. By detecting deviations in the detected intake air amount and identifying abnormal operating conditions in advance, the system can switch to alternative calculation methods or apply correction factors to maintain accurate exhaust gas recirculation ratio calculation even when the primary sensor is malfunctioning
Solution Approach 2:
The control apparatus introduces an intermediary detection mechanism that monitors the detected intake air amount for deviations and abnormal conditions. This intermediary system acts as a mediator between the faulty sensor and the control algorithm, detecting issues like passage disconnections or sensor failures and enabling the system to compensate for these problems through alternative calculation approaches
2Measurement precision
If the detected intake air amount deviates from the actual value due to sensor failure or passage disconnection, then the exhaust gas recirculation ratio calculation becomes inaccurate, but adding complex detection systems increases device complexity
Solution Approach 1:
The control apparatus uses the existing intake air amount sensor and available engine operating parameters to self-diagnose abnormal conditions. By monitoring deviations in the detected intake air amount and analyzing operating conditions, the system performs self-detection of sensor failures or passage disconnections without requiring additional dedicated detection hardware, thereby maintaining detection accuracy while avoiding increased device complexity
Solution Approach 2:
The control apparatus changes the parameters used for exhaust gas recirculation ratio calculation when abnormal conditions are detected. Instead of relying solely on the detected intake air amount, the system switches to alternative parameters or corrected values based on the identified abnormal condition, maintaining calculation accuracy without adding physical detection components
3Measurement precision
If air-fuel ratio feedback control is used to maintain desired air-fuel ratio, then fuel supply control accuracy is maintained, but ignition timing control still suffers from detection errors causing misfire or knocking
Solution Approach 1:
The control apparatus performs preliminary correction of the detected intake air amount by identifying and compensating for abnormal conditions before using it for ignition timing control. By detecting sensor failures or passage disconnections in advance and applying corrections to the intake air amount data, the system ensures reliable ignition timing control and prevents misfire or knocking caused by inaccurate detection values
Data Source
AI summary
A control apparatus for an internal combustion engine having a throttle valve disposed in an intake passage of the engine is provided. A wide-open intake air amount, which is an intake air amount corresponding to a state where the throttle valve is fully opened, is calculated, and a theoretical intake air amount, which is an intake air amount corresponding to a state where no exhaust gas of the engine is recirculated to a combustion chamber of the engine, is calculated according to the wide-open intake air amount and the intake pressure. An air-fuel ratio correction amount and a learning value thereof are calculated according to the detected air-fuel ratio, and a reference intake air amount is calculated using the intake pressure, the engine rotational speed, the air-fuel ratio correction amount, and the learning value. A lower limit value of the detected intake air amount is set according to the reference intake air amount, and a limit process is performed for limiting the detected intake air amount within a range of values which are equal to or greater than the lower limit value. An amount of the evaporative fuel/air mixture supplied to the intake passage is calculated, and the limit-processed intake air amount is corrected using the evaporative fuel/air mixture amount to calculate an intake gas amount. An exhaust gas recirculation ratio is calculated using the theoretical intake air amount and the intake gas amount.