Internal combustion engine and control method thereof

A control method of an internal combustion engine that has a port injection valve and is capable of running on a gasoline/alcohol mixed fuel, the method comprising the steps of:

• detecting a load during operation of the internal combustion engine;
• detecting an alcohol concentration of the mixed fuel;
• and
• increasing a mixed fuel injection amount in a synchronous injection period in response to the engine load when the detected engine load is higher than a predetermined load value and the detected alcohol concentration is higher than a predetermined concentration value, while fixing a mixed fuel injection amount for an asynchronous injection period to be greater than zero, the synchronous injection period being a period in which a period in which an intake valve is opened and a period in which the mixed fuel is injected from the port injection valve overlap with each other, the asynchronous injection period being a period within the injection period of the mixed fuel in which the injection period of the mixed fuel does not overlap with the opening period of the intake valve, wherein
• the synchronous injection period is set on and after exhaust top dead center.

A controller for an internal combustion engine that has a port injection valve and is capable of running on a gasoline/alcohol mixed fuel, the controller comprising:

• load detecting means that detects a load during operation of the internal combustion engine;
• alcohol concentration detecting means that detects an alcohol concentration of the mixed fuel;
• and
• synchronous fuel injection increasing means that increases a mixed fuel injection amount in a synchronous injection period in response to the engine load when the engine load detected by the load detecting means is higher than a predetermined load value and the alcohol concentration detected by the alcohol concentration detecting means is higher than a predetermined concentration value, while fixing a mixed fuel injection amount for an asynchronous injection period to be greater than zero, the synchronous injection period being a period in which a period in which an intake valve is opened and a period in which the mixed fuel is injected from the port injection valve overlap with each other, the asynchronous injection period being a period within the injection period of the mixed fuel in which the injection period of the mixed fuel does not overlap with the opening period of the intake valve, wherein
• the synchronous injection period is set on and after exhaust top dead center.