Engine EGR Ratio Calculation Using In-Cylinder Gas Temperature
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Solution Overview
Problem
The existing control system for internal combustion engines fails to accurately calculate the in-cylinder gas amount and EGR ratio when the in-cylinder gas temperature changes due to internal EGR, leading to overestimation of the EGR ratio and potential knocking issues.
Innovation Solution
A control system that calculates the reference and ideal in-cylinder gas amounts and temperatures, using sensors to detect rotational speed, intake pressure, and valve operation phases, allowing for accurate calculation of the EGR ratio and internal EGR amount, even with changing in-cylinder gas temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the stoichiometric intake air amount is calculated based on fully-open intake air amount and intake pressure without considering in-cylinder gas temperature, then the calculation method is simple, but the EGR ratio is overestimated and knocking may occur
Solution Approach 1:
The patent introduces in-cylinder gas temperature as an additional parameter to the stoichiometric intake air amount calculation. The ECU calculates the in-cylinder gas temperature based on exhaust gas recirculation amount and other operating parameters, then uses this temperature to correct the stoichiometric intake air amount. This parameter addition resolves the contradiction by maintaining calculation simplicity while improving EGR ratio accuracy through temperature compensation.
2Adaptability or versatility
If internal EGR is performed by changing operation phases of intake and exhaust valves, then the EGR ratio increases, but the in-cylinder gas temperature rises and causes overestimation of EGR ratio
Solution Approach 1:
The patent implements a feedback mechanism where the ECU continuously monitors in-cylinder gas temperature and adjusts the stoichiometric intake air amount calculation accordingly. The calculated in-cylinder gas temperature feeds back into the EGR ratio calculation process, allowing the system to accurately determine EGR ratio even when internal EGR is actively performed through valve phase changes. This feedback loop resolves the measurement accuracy issue while maintaining EGR control versatility.
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 enables precise control of the engine by accurately calculating the in-cylinder gas amount and EGR ratio, preventing knocking and optimizing engine performance across varying operating conditions.
Implementation Method 1
intake pressure-detecting means (intake pressure sensor 11) for detecting an intake pressure PBA in the engine
Implementation Method 2
rotational speed-detecting means (crank angle sensor 17) for detecting a rotational speed NE of the engine
Implementation Method 3
based on an equation of state of gas, the amount of in-cylinder gases actually filled in the cylinder is calculated by correcting the ideal in-cylinder gas amount according to the in-cylinder gas temperature
Data Source
AI summary
A control system and a control method for an internal combustion engine, which are capable of accurately calculating an in-cylinder gas amount and an EGR ratio by a relatively simple method even in a case where an in-cylinder gas temperature is changed by execution of internal EGR, and properly controlling the engine using the EGR ratio thus calculated. An in-cylinder gas amount Gact actually filled in the cylinder is calculated by correcting an ideal in-cylinder gas amount Gth, which is an amount of gases filled in a cylinder in an ideal state in which it is assumed that no exhaust gases of the engine are recirculated into the cylinder, using an ideal in-cylinder gas temperature Tcylth according to an in-cylinder gas temperature Tcyl, and an EGR ratio REGRT is calculated using the in-cylinder gas amount Gact and an intake air amount Gaircyl.