Controller and control method for internal combustion engine

A method for controlling an internal combustion engine, the internal combustion engine including:

• a fuel injection valve;
• a cylinder into which air-fuel mixture containing fuel injected by the fuel injection valve is introduced;
• an ignition device that ignites the air-fuel mixture introduced into the cylinder with a spark;
• an exhaust passage through which gas discharged out of the cylinder flows;
• and
• a three-way catalyst device arranged in the exhaust passage, wherein
• the method comprises:
• executing a catalyst temperature-increasing control of increasing a temperature of the three-way catalyst device by introducing the air-fuel mixture, which contains the fuel injected by the fuel injection valve, into the exhaust passage without burning the air-fuel mixture in the cylinder;
• and
• controlling an air-fuel ratio of the air-fuel mixture during the execution of the catalyst temperature-increasing control such that the air-fuel ratio becomes a richer air-fuel ratio during a first period from a beginning of the catalyst temperature-increasing control to a specified air-fuel ratio switching timing than during a second period from the air-fuel ratio switching timing to a completion of the catalyst temperature-increasing control.

A controller configured to control an internal combustion engine, the internal combustion engine including:

• a fuel injection valve;
• a cylinder into which air-fuel mixture containing fuel injected by the fuel injection valve is introduced;
• an ignition device that ignites the air-fuel mixture introduced into the cylinder with a spark;
• an exhaust passage through which gas discharged out of the cylinder flows;
• and
• a three-way catalyst device arranged in the exhaust passage, wherein
• the controller comprises processing circuitry configured to:
• execute a catalyst temperature-increasing control of increasing a temperature of the three-way catalyst device by introducing the air-fuel mixture, which contains the fuel injected by the fuel injection valve, into the exhaust passage without burning the air-fuel mixture in the cylinder;
• and
• control an air-fuel ratio of the air-fuel mixture during the execution of the catalyst temperature-increasing control such that the air-fuel ratio becomes a richer air-fuel ratio during a first period from a beginning of the catalyst temperature-increasing control to a specified air-fuel ratio switching timing than during a second period from the air-fuel ratio switching timing to a completion of the catalyst temperature-increasing control.