Controller and control method for internal combustion engine

1. A controller for an internal combustion engine that includes

a three-way catalyst that is arranged in an exhaust passage and purifies exhaust gas,

a particulate filter that is arranged in a section of the exhaust passage at a downstream side of the three-way catalyst to trap particulate matter contained in the exhaust gas,

an exhaust gas recirculation passage that extends from a section of the exhaust passage at an upstream side of the particulate filter and communicates with an intake passage to recirculate the exhaust gas to the intake passage, the exhaust gas recirculation passage being connected to a section of the intake passage at the upstream side of a throttle valve that is provided in the intake passage, and

an exhaust gas recirculation valve that opens and closes a flow path of the exhaust gas recirculation passage,

the internal combustion engine being configured to burn, in a cylinder, an air-fuel mixture containing fuel injected from a fuel injection valve by spark discharge of an ignition device,

wherein the controller is configured to execute a fuel introduction process while combustion in the cylinder is stopped under a situation in which a crankshaft of the internal combustion engine is rotating,

the fuel introduction process causes fuel to be injected from the fuel injection valve and causes the fuel to flow out unburned from inside the cylinder to the exhaust passage,

the controller includes a recirculation valve controlling section that controls opening and closing of the exhaust gas recirculation valve,

an opening degree of the exhaust gas recirculation valve is a preliminary opening degree at a point in time when switching from a state in which an execution condition of the fuel introduction process is not satisfied to a state in which the execution condition of the fuel introduction process is satisfied, and

the recirculation valve controlling section is configured to cause the opening degree of the exhaust gas recirculation valve to be smaller than the preliminary opening degree during execution of the fuel introduction process so as to restrict returning of the fuel that has been introduced into the exhaust passage from inside the cylinder and the gas that has been heated in the three-way catalyst to the intake passage via the exhaust gas recirculation passage.

2. The controller according to claim 1 , wherein the recirculation valve controlling section is configured to set the opening degree of the exhaust gas recirculation valve to 0 during the execution of the fuel introduction process.

3. The controller according to claim 1 , wherein the recirculation valve controlling section is configured to cause, after the execution condition of the fuel introduction process is satisfied, the opening degree of the exhaust gas recirculation valve to be smaller than the preliminary opening degree in a period from a point in time before the fuel is injected from the fuel injection valve to a point in time during the execution of the fuel introduction process.

4. The controller according to claim 1 , wherein the exhaust gas recirculation passage is connected to the exhaust passage at the downstream side of the three-way catalyst.

5. A control method for an internal combustion engine that includes

a three-way catalyst that is arranged in an exhaust passage and purifies exhaust gas,

a particulate filter that is arranged in a section of the exhaust passage at a downstream side of the three-way catalyst to trap particulate matter contained in the exhaust gas,

an exhaust gas recirculation passage that extends from a section of the exhaust passage at an upstream side of the particulate filter and communicates with an intake passage to recirculate the exhaust gas to the intake passage, the exhaust gas recirculation passage being connected to a section of the intake passage at the upstream side of a throttle valve that is provided in the intake passage, and

an exhaust gas recirculation valve that opens and closes a flow path of the exhaust gas recirculation passage,

the internal combustion engine being configured to burn, in a cylinder, an air-fuel mixture containing fuel injected from a fuel injection valve by spark discharge of an ignition device,

wherein the control method comprises:

performing a fuel introduction process, in which, while combustion in the cylinder is stopped under a situation in which a crankshaft of the internal combustion engine is rotating, fuel is injected from the fuel injection valve and the fuel is caused to flow out unburned from inside the cylinder to the exhaust passage,

controlling opening and closing of the exhaust gas recirculation valve, wherein an opening degree of the exhaust gas recirculation valve is a preliminary opening degree at a point in time when switching from a state in which an execution condition of the fuel introduction process is not satisfied to a state in which the execution condition of the fuel introduction process is satisfied, and

causing the opening degree of the exhaust gas recirculation valve to be smaller than the preliminary opening degree during execution of the fuel introduction process so as to restrict returning of the fuel that has been introduced into the exhaust passage from inside the cylinder and the gas that has been heated in the three-way catalyst to the intake passage via the exhaust gas recirculation passage.

6. A non-transitory computer readable memory medium storing a program that causes a processor to execute a controlling process of an internal combustion engine that includes

a three-way catalyst that is arranged in an exhaust passage and purifies exhaust gas,

a particulate filter that is arranged in a section of the exhaust passage at a downstream side of the three-way catalyst to trap particulate matter contained in the exhaust gas,

an exhaust gas recirculation passage that extends from a section of the exhaust passage at an upstream side of the particulate filter and communicates with an intake passage to recirculate the exhaust gas to the intake passage, the exhaust gas recirculation passage being connected to a section of the intake passage at the upstream side of a throttle valve that is provided in the intake passage, and

an exhaust gas recirculation valve that opens and closes a flow path of the exhaust gas recirculation passage,

the internal combustion engine being configured to burn, in a cylinder, an air-fuel mixture containing fuel injected from a fuel injection valve by spark discharge of an ignition device,

wherein the controlling process includes

performing a fuel introduction process, in which, while combustion in the cylinder is stopped under a situation in which a crankshaft of the internal combustion engine is rotating, fuel is injected from the fuel injection valve and the fuel is caused to flow out unburned from inside the cylinder to the exhaust passage,

controlling opening and closing of the exhaust gas recirculation valve, wherein an opening degree of the exhaust gas recirculation valve is a preliminary opening degree at a point in time when switching from a state in which an execution condition of the fuel introduction process is not satisfied to a state in which the execution condition of the fuel introduction process is satisfied, and

causing the opening degree of the exhaust gas recirculation valve to be smaller than the preliminary opening degree during execution of the fuel introduction process so as to restrict returning of the fuel that has been introduced into the exhaust passage from inside the cylinder and the gas that has been heated in the three-way catalyst to the intake passage via the exhaust gas recirculation passage.