Internal combustion engine and control method for internal combustion engine

An internal combustion engine comprising:

• an intake valve configured and arranged to selectively open to introduce fresh air into a combustion chamber;
• an exhaust valve configured and arranged to selectively open to release exhaust gas from the combustion chamber;
• a main passage fluidly coupled to the combustion chamber to discharge the exhaust gas from the combustion chamber;
• a main catalyst disposed in the main passage;
• a bypass passage bypassing the main passage on an upstream side of the main catalyst, the bypass passage having a transverse cross-sectional area that is smaller than a transverse cross-sectional area of the main passage;
• a bypass catalyst disposed in the bypass passage;
• a passage open/close unit disposed in a portion of the main passage bypassed by the bypass passage and configured and arranged to switch between an open state and a closed state to selectively open or selectively close the main passage;
• a residual gas amount changing unit configured and arranged to change an amount of residual gas remaining inside the combustion chamber;
• and
• a controller configured to control the residual gas amount changing unit when a passage opening condition for switching the passage open/close unit from the closed state to the open state is satisfied, the controller being configured to control the residual gas amount changing unit to maintain a substantially constant amount of the residual gas between before and after the passage open/close unit is switched from the closed state to the open state,
• with the residual gas amount changing unit including an intake valve open timing changing mechanism configured and arranged to change an open timing of the intake valve, and the controller being configured to control the intake valve open timing changing mechanism to advance the intake valve open timing when the passage open/close unit is switched from the closed state to the open state.

An internal combustion engine comprising:

• an intake valve configured and arranged to selectively open to introduce fresh air into a combustion chamber;
• an exhaust valve configured and arranged to selectively open to release exhaust gas from the combustion chamber;
• a main passage fluidly coupled to the combustion chamber to discharge the exhaust gas from the combustion chamber;
• a main catalyst disposed in the main passage;
• a bypass passage bypassing the main passage on an upstream side of the main catalyst, the bypass passage having a transverse cross-sectional area that is smaller than a transverse cross-sectional area of the main passage;
• a bypass catalyst disposed in the bypass passage;
• a passage open/close unit disposed in a portion of the main passage bypassed by the bypass passage and configured and arranged to switch between an open state and a closed state to selectively open or selectively close the main passage;
• a residual gas amount changing unit configured and arranged to change an amount of residual gas remaining inside the combustion chamber;
• and
• a controller configured to control the residual gas amount changing unit when a passage opening condition for switching the passage open/close unit from the closed state to the open state is satisfied, the controller being configured to control the residual gas amount changing unit to reduce the amount of residual gas upon the passage opening condition being satisfied prior to switching of the passage open/close unit from the closed state to the open state,
• with the residual gas amount changing unit including a valve overlap changing mechanism configured and arranged to change a valve overlap amount between the exhaust valve and the intake valve, and the controller being configured to control the valve overlap changing mechanism to reduce the valve overlap amount prior to switching the passage open/close unit from the closed state to the open state.