Control device and control method for internal combustion engine

An internal combustion engine control device comprising:na turbocharger provided on an internal combustion engine;a first exhaust valve that opens and closes an exhaust port that communicates with a first exhaust passageway on which a turbine of the turbocharger is provided;a second exhaust valve that opens and closes an exhaust port that communicates with a second exhaust passageway that bypasses the turbine;a catalyst disposed at a downstream side of a meeting point of the first exhaust passageway and the second exhaust passageway;an engine load acquisition device that acquires an engine load; anda control portion that opens only the second exhaust valve when the engine load is less than a first predetermined value, and that opens both the first and second exhaust valves when the engine load is greater than or equal to the first predetermined value and less than a second predetermined value, and that opens only the first exhaust valve when the engine load is greater than or equal to the second predetermined value,wherein the control portion sets the first predetermined value to be lower during a lean combustion than during a stoichiometric combustion.

An internal combustion engine control device comprising:na turbocharger provided on an internal combustion engine;a first exhaust valve that opens and closes an exhaust port that communicates with a first exhaust passageway on which a turbine of the turbocharger is provided;a second exhaust valve that opens and closes an exhaust port that communicates with a second exhaust passageway that bypasses the turbine;a catalyst disposed at a downstream side of a meeting point of the first exhaust passageway and the second exhaust passageway; anda control portion that, during a lean combustion, brings the second exhaust valve to rest in a closed state, and sets an amount of valve overlap between the first exhaust valve and an intake valve to be less than a predetermined value.

A control method for an internal combustion engine that includes a turbocharger, a first exhaust valve that opens and closes an exhaust port that communicates with a first exhaust passageway on which a turbine of the turbocharger is provided, a second exhaust valve that opens and closes an exhaust port that communicates with a second exhaust passageway that bypasses the turbine, and a catalyst disposed at a downstream side of a meeting point of the first exhaust passageway and the second exhaust passageway, the control method comprising:nsetting a first region that is an operation region of the internal combustion engine in which only the second exhaust valve is opened, a second region that is an operation region of the internal combustion engine in which both the first and second exhaust valves are opened, and a third region that is an operation region of the internal combustion engine in which only the first exhaust valve is opened;calculating an engine rotation speed and an engine load;determining whether or not a lean combustion is being performed based on the engine rotation speed and the engine load; andsetting a first predetermined value that is an upper-limit value of the first region or both the first predetermined value and a second predetermined value that is an upper-limit value of the second region to be lower when it is determined that the internal combustion engine is presently operated in the lean combustion than when it is determined that the internal combustion engine is presently operated in a stoichiometric combustion.

A control method for an internal combustion engine that includes a turbocharger, a first exhaust valve that opens and closes an exhaust port that communicates with a first exhaust passageway on which a turbine of the turbocharger is provided, a second exhaust valve that opens and closes an exhaust port that communicates with a second exhaust passageway that bypasses the turbine, and a catalyst disposed at a downstream side of a meeting point of the first exhaust passageway and the second exhaust passageway, the control method comprising:nsetting a first region that is an operation region of the internal combustion engine in which only the second exhaust valve is opened, a second region that is an operation region of the internal combustion engine in which both the first and second exhaust valves are opened, and a third region that is an operation region of the internal combustion engine in which only the first exhaust valve is opened;calculating an engine rotation speed and an engine load;determining whether or not a lean combustion is being performed based on the engine rotation speed and the engine load;detecting a bed temperature of the catalyst; andbringing the second exhaust valve to rest in a closed state and setting an amount of valve overlap between the first exhaust valve and an intake valve to be less than a predetermined value, when it is determined that the internal combustion engine is presently operated in a lean combustion and the catalyst bed temperature is greater than or equal to a reference value.