Method for obtaining exhaust gas flow quantity, exhaust gas flow measurement apparatus, and exhaust gas recirculation control system

An exhaust gas flow measurement apparatus comprising:

• a gas flowmeter for exhaust gases, which is provided in a passage for exhaust gas recirculation between an exhaust side and an intake side, and has a heating resistor controlled so as to have a predetermined temperature difference with respect to the temperature of the exhaust gases;
• a means for predicting or sensing oxygen concentration of the exhaust gases;
• and
• a means for computing an flow quantity of the exhaust gases flowing through the passage on the basis of signals from the gas flowmeter and the means for predicting or sensing oxygen concentration.

An exhaust gas recirculation control system of an internal combustion engine comprising:

• an EGR valve provided in an exhaust gas recirculation passage of the internal combustion engine;
• a gas mass flowmeter provided in the exhaust recirculation passage for measuring mass flow of recirculation exhaust gases flowing through the exhaust gas recirculation passage;
• an intake air mass flowmeter for measuring mass flow of intake air flowing through an intake passage of the internal combustion engine;
• a first computing means for computing an instruction quantity of fuel injection on the basis of operating conditions of the internal combustion engine;
• a predicting means for predicting the concentration of any component in the exhaust gases every combustion in each cylinder of the internal combustion engine, by using signals of the measured intake air mass flow and recirculation exhaust gas mass flow, and information of the computed instruction quantity of fuel injection;
• a second computing means for computing oxygen concentration in total intake air containing the recirculation exhaust gases in the cylinder, and computing the ratio between an oxygen quantity in the total intake air and a fuel injection quantity (hereinafter it's called as “oxygen quantity/fuel injection quantity ratio”) on the basis of the intake air mass flow signal, the recirculation exhaust gas mass flow signal and the predicted concentration of any component in the exhaust gases, and
• a control means for controlling at least an opening of the EGR valve or the fuel injection quantity, by comparing said computed oxygen concentration in total intake air and oxygen quantity/fuel injection quantity ratio with target oxygen concentration in total intake air and a target oxygen quantity/fuel injection quantity ratio which are pre-set according to engine operating conditions,
• the system further comprises a correcting means for correcting the recirculation exhaust gas mass flow signal on the basis of the predicted concentration of any component in the exhaust gases, and
• the second computing means is constituted so as to compute the oxygen concentration in total intake air in the cylinder and the oxygen quantity/fuel injection quantity ratio, by using the corrected recirculation exhaust gas mass flow signal.