CONTROLLER AND CONTROL METHOD FOR INTERNAL COMBUSTION ENGINE

A controller is used for an internal combustion engine including a cylinder and a direct injection valve that injects gaseous fuel into the cylinder. A CPU of the controller executes acquisition of an in-cylinder pressure that is a pressure in the cylinder during one combustion cycle and a supply fuel pressure that is a pressure of the gaseous fuel supplied to the direct injection valve, and calculation of a backflow rate that is an amount of combustion gas flowing into the direct injection valve from the cylinder during one combustion cycle of the cylinder. In the calculation of the backflow rate, the CPU calculates the backflow rate such that the backflow rate becomes larger as the in-cylinder pressure increases and the backflow rate becomes larger as the supply fuel pressure decreases.