CONTROLLER FOR INTERNAL COMBUSTION ENGINE

An internal combustion engine includes a fuel injection valve configured to inject hydrogen gas into the cylinder, a selective catalytic reduction catalyst located in an exhaust passage and configured to remove NOx, a urea water injection valve configured to inject urea water into the catalyst, a tank that stores urea water injected by the urea water injection valve, and a remaining amount detection sensor configured to detect a remaining amount of urea water stored in the tank. A controller for the internal combustion engine is configured to execute a restriction process that controls, when the remaining amount is less than a set value, an injection amount of hydrogen gas by the fuel injection valve such that an air excess ratio in the cylinder becomes greater than or equal to a specified excess ratio that is greater than 1.