Scavenged gas amount calculation device and internal EGR amount calculation device for internal combustion engine

A scavenged gas amount calculation device for an internal combustion engine in which a valve overlap time period of an intake valve and an exhaust valve of a cylinder is changed by changing valve timing of at least one of the intake valve and the exhaust valve, comprising:

• intake pressure parameter-obtaining means for obtaining an intake pressure parameter indicative of an intake pressure which is a pressure within an intake passage of the engine;
• exhaust pressure parameter-obtaining means for obtaining an exhaust pressure parameter indicative of an exhaust pressure which is a pressure within an exhaust passage of the engine;
• time period parameter-obtaining means for obtaining a time period parameter indicative of a length of the valve overlap time period;
• and
• scavenged gas amount-calculating means for calculating a scavenged gas amount which is an amount of gases scavenged from within the cylinder of the engine into the exhaust passage when the intake pressure is higher than the exhaust pressure during the valve overlap time period, according to the intake pressure parameter, the exhaust pressure parameter, and the time period parameter,
• wherein the scavenged gas amount is used to change the valve timing of at least one of the intake valve and the exhaust valve,
• wherein said exhaust pressure parameter-obtaining means includes minimum exhaust pressure-calculating means for calculating, as the exhaust pressure parameter, a minimum exhaust pressure which is a minimum value of the exhaust pressure during the valve overlap time period, according to a value indicative of an operating condition of the engine, and
• wherein said scavenged gas amount-calculating means includes scavenged gas production degree parameter-calculating means for calculating a scavenged gas production degree parameter indicative of a degree of production of the scavenged gases during the valve overlap time period, according to the time period parameter, and
• wherein the scavenged gas amount is calculated according to the scavenged gas production degree parameter, the intake pressure parameter, and the minimum exhaust pressure.