CONTROLLER FOR INTERNAL COMBUSTION ENGINE AND METHOD FOR CONTROLLING INTERNAL COMBUSTION ENGINE

A controller and a control method for an internal combustion engine are provided. The internal combustion engine uses hydrogen as fuel. A base value of a fuel injection amount is calculated based on a requested torque. A smaller one of an upper limit value of the fuel injection amount and the base value is set as a target value. The upper limit value corresponds to an engine load factor. A NOx concentration difference is a difference between a NOx concentration in exhaust gas and a reference value for the NOx concentration. When the NOx concentration difference is greater than or equal to a threshold value, a relationship between the engine load factor and the upper limit value is corrected such that the upper limit value decreases.