Patent ID: 8733328

Claim:
A method for controlling operation of an internal combustion engine in which the engine is temporarily stopped according to a request for a stop to the engine having an exhaust gas recirculation system incorporated therein, and the engine is started again according to a request for a start to the engine, wherein the exhaust gas recirculation system includes: an EGR passage for recirculating a part of exhaust gas discharged from the engine to an air intake passage as EGR gas, one end of the EGR passage being communicated with the air intake passage and the other end thereof being communicated with an exhaust passage; an EGR control valve arranged on one end side of the EGR passage for controlling a flow rate of the EGR gas flowing through the EGR passage; and an on-off valve arranged on the other end side of the EGR passage for opening and closing the EGR passage, the method comprising the steps of: determining whether or not the engine is in a pressure-accumulable operational state in which the EGR gas is pressure-accumulated in the EGR passage between the EGR valve and the on-off valve; bringing the EGR valve into a full closed state when it is determined that the engine is in the pressure-accumulable operational state; comparing a pressure of exhaust gas interposed in the exhaust passage to be led to the EGR passage, and a pressure of the EGR gas interposed in the EGR passage between the EGR valve and the on-off valve after bringing the EGR valve into the full closed state; and bringing the on-off valve into the full closed state when the pressure of the exhaust gas interposed in the exhaust passage to be led to the EGR passage becomes lower than the pressure of the EGR gas interposed in the EGR passage between the EGR valve and the on-off valve.