Patent ID: 7715975

Claim:
An engine control system comprising: intake air amount control means for controlling the amount of air taken into an engine; an intake airflow sensor for detecting the amount of air taken into the engine; an EGR path for returning part of exhaust gas, the EGR path being connected to an exhaust path and an intake path in the engine; an EGR flow sensor for detecting the flow rate of an EGR gas that passes through the EGR path; EGR flow rate control means for controlling the flow rate of the EGR gas that passes through the EGR path; an intake pressure sensor for detecting the pressure in an intake pipe of the engine; and a fuel supply unit for supplying the engine with fuel; wherein said engine control system further comprises: first EGR rate estimation means for estimating the EGR rate of the engine on the basis of the output result of the intake airflow sensor and the output result of the EGR flow sensor; and second EGR rate estimation means for estimating the EGR rate of the engine on the basis of the detection result of the EGR flow sensor and the detection result of the intake pressure sensor.