Internal Combustion Engine Control Device EGR Ratio Calculation
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Solution Overview
Problem
Existing control devices for internal combustion engines face challenges in accurately calculating the in-cylinder gas temperature and EGR ratio due to transport delays of external EGR, leading to reduced calculation accuracy and inappropriate engine control during transient operations.
Innovation Solution
A control device that calculates the ideal in-cylinder gas amount and temperature, using a speed-density method for mixed gas amounts and temperatures, and accounts for internal EGR, to minimize the influence of transport delays and accurately determine the EGR ratio, enabling precise engine control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external EGR amount and temperature are calculated using conventional methods, then calculation can be performed, but transport delay causes deviation from actual values reducing accuracy
Solution Approach 1:
The patent applies preliminary action by calculating the external EGR amount and temperature based on upstream conditions (exhaust manifold pressure and temperature) before the EGR gas actually reaches the intake passage. This allows the control device to predict what the EGR parameters will be when they arrive, compensating for the transport delay. The calculation uses the equation of state and isentropic expansion relationships to determine downstream conditions from upstream measurements, ensuring accurate EGR ratio calculation despite the time lag in physical transport.
2Measurement precision
If EGR ratio calculation uses actual external EGR values, then accuracy improves, but transport delay prevents access to accurate real-time values
Solution Approach 1:
The patent calculates the external EGR amount and temperature based on upstream conditions (exhaust manifold pressure and temperature) before the EGR gas actually reaches the intake passage. This allows the control device to predict what the EGR parameters will be when they arrive, compensating for the transport delay. The calculation uses the equation of state and isentropic expansion relationships to determine downstream conditions from upstream measurements, ensuring accurate EGR ratio calculation despite the time lag in physical transport.
3Measurement precision
If conventional calculation methods are used, then device complexity is low, but calculation accuracy deteriorates during transient operations
Solution Approach 1:
The patent applies parameter changes by transitioning from directly measuring downstream EGR parameters to calculating them from upstream parameters using thermodynamic relationships. Specifically, it uses the equation of state (PV=nRT) and isentropic expansion relationships to transform the calculation from direct measurement to predictive calculation based on exhaust manifold conditions. This parameter transformation approach maintains calculation simplicity while significantly improving accuracy during transient operations where direct measurement would be delayed and inaccurate.
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
The solution allows for accurate calculation of in-cylinder gas temperature and EGR ratio, even during transient operations, thereby improving engine control and reducing the impact of external EGR transport delays, ensuring proper engine operation.
Implementation Method 1
a temperature Tcyl of the in-cylinder gas actually charged in the cylinder is calculated by the following equation (A) using an intake air temperature Ta, an exhaust gas temperature Tex (internal EGR temperature), an external EGR temperature Tegr, an intake air amount Gaircyl, an internal EGR amount Ginegr, and an external EGR amount Gexegr
Implementation Method 2
the external EGR temperature Tegr is calculated by adding a temperature rise amount DTegr, which is caused by conducting the external EGR and which has been calculated in accordance with the external EGR amount Gexegr or the like, to the intake air temperature Ta that has been detected
Data Source
AI summary
In a control device for an internal combustion engine in which internal EGR and external EGR are conducted, an ideal in-cylinder gas amount and an ideal in-cylinder gas temperature in an ideal state in which neither of EGR gas recirculates into a cylinder are calculated (steps 1 and 2). A mixed gas amount of intake air and the external EGR gas present on a downstream side of a throttle valve is calculated, based on a rotation speed of the internal combustion engine and intake air pressure (step 21) to detect a mixed gas temperature. An actual in-cylinder gas temperature and amount and an EGR ratio are calculated, based on the ideal in-cylinder gas amount, the ideal in-cylinder gas temperature, the mixed gas amount, and the mixed gas temperature (steps 24, 4, and 5), and an internal combustion engine is controlled based on the EGR ratio.