Patent ID: 8005605
Filing Date: 2011-08-23
Classification: F02D

Abstract:
1. A control system for an internal combustion engine that has an exhaust system provided with a first exhaust gas purification device for purifying exhaust gases, the engine having fresh air drawn into a cylinder, fuel for combustion in the cylinder being supplied to the cylinder as first fuel, and unburned fuel being supplied to the first exhaust gas purification device as second fuel, the control system controlling an amount of the fresh air, an amount of the first fuel and an amount of the second fuel to thereby control an exhaust system temperature as a temperature of the exhaust system, and an air-fuel ratio of exhaust gases on a downstream side of the first exhaust gas purification device, the control system comprising: exhaust system temperature-detecting means for detecting the temperature of the exhaust system; oxygen concentration-detecting means provided at a location downstream of the first exhaust gas purification device, for outputting a signal indicative of a concentration of oxygen in exhaust gases; target output value-setting means for setting a target output value that serves as a target of an output value from said oxygen concentration-detecting means; first fuel amount-calculating means for calculating the amount of the first fuel; target air-fuel ratio parameter-calculating means for calculating a target air-fuel ratio parameter, which serves as a target of an air-fuel ratio parameter indicative of an air-fuel ratio of a combustion air-fuel mixture, such that the target air-fuel ratio parameter becomes leaner than an air-fuel ratio parameter of the combustion air-fuel mixture at which the output value from said oxygen concentration-detecting means becomes the target output value; air-fuel ratio parameter correction value-calculating means for calculating an air-fuel ratio parameter correction value with a first control algorithm including a predetermined feedback control algorithm such that the exhaust system temperature is caused to converge to a predetermined target temperature; corrected target air-fuel ratio parameter-calculating means for calculating a corrected target air-fuel ratio parameter by correcting the target air-fuel ratio parameter by the air-fuel ratio parameter correction value; target fresh air amount-calculating means for calculating a target fresh air amount that serves as a target of the amount of the fresh air, according to the corrected target air-fuel ratio parameter and the amount of the first fuel; target fuel amount-calculating means for calculating a fuel amount required for generating the combustion air-fuel mixture which makes the output value from said oxygen concentration-detecting means become the target output value, as a target fuel amount, according to the target fresh air amount; fuel amount correction value-calculating means for calculating a fuel amount correction value with a second control algorithm including a predetermined feedback control algorithm such that the output value from said oxygen concentration-detecting means is caused to converge to the target output value; and second fuel amount-calculating means for calculating the amount of the second fuel using the target fuel amount, the amount of the first fuel and the fuel amount correction value.