Abstract: An internal combustion engine 1 at a standstill of a vehicle after cold starting can switch its combustion mode to a homogenous combustion mode or a stratified combustion mode. An operation range of the stratified combustion at the standstill of the vehicle after cold starting is expanded relative to an operation range of the homogenous combustion at the standstill of the vehicle after cold starting as an inclination of the vehicle decreases. With this technique, the operation range of the stratified combustion can be expanded while assuring an intake air negative pressure required for achieving the brake performance, so that HC reduction at the standstill of the vehicle after cold starting is obtained.

Abstract: An internal combustion engine 1 at a standstill of a vehicle after cold starting can switch its combustion mode to a homogenous combustion mode or a stratified combustion mode. An operation range of the stratified combustion at the standstill of the vehicle after cold starting is expanded relative to an operation range of the homogenous combustion at the standstill of the vehicle after cold starting as an inclination of the vehicle decreases. With this technique, the operation range of the stratified combustion can be expanded while assuring an intake air negative pressure required for achieving the brake performance, so that HC reduction at the standstill of the vehicle after cold starting is obtained.

Abstract: By setting the configuration of a cavity (25) of a piston (5) appropriately, tumble is produced in air that is aspirated into a combustion chamber (6) inside a cylinder (3) from an intake port (8), and by means of this tumble, the spray of fuel injected by a fuel injector (12) is caused to gather around the periphery of a spark plug (7). A predetermined tumble in the form of an upright ellipse is set in the longitudinal cross section of the cylinder (3) which includes an injection point (I) of the fuel injector (12) and an ignition point (T) of the spark plug (7). The bottom surface (26) of the cavity (25) is curved so as to conform to the radius of curvature (R1) of the lower end of the elliptical tumble, thereby advancing the formation of elliptical tumble which is unlikely to interfere with the cylinder wall surfaces.

Abstract: By setting the configuration of a cavity (25) of a piston (5) appropriately, tumble is produced in air that is aspirated into a combustion chamber (6) inside a cylinder (3) from an intake port (8), and by means of this tumble, the spray of fuel injected by a fuel injector (12) is caused to gather around the periphery of a spark plug (7). A predetermined tumble in the form of an upright ellipse is set in the longitudinal cross section of the cylinder (3) which includes an injection point (I) of the fuel injector (12) and an ignition point (T) of the spark plug (7). The bottom surface (26) of the cavity (25) is curved so as to conform to the radius of curvature (R1) of the lower end of the elliptical tumble, thereby advancing the formation of elliptical tumble which is unlikely to interfere with the cylinder wall surfaces.

Abstract: An in-cylinder direct-injection spark-ignition engine using at least a homogeneous combustion mode and a stratified combustion mode and equipped with a pentroof combustion chamber head having first and second shallow-angled surfaces, comprises intake valves disposed in the first shallow-angled surface, exhaust valves disposed in the second shallow-angled surface. A pair of substantially straight intake ports are formed in the cylinder head. A tumble-and-swirl control valve is disposed in a first intake port of the substantially straight intake ports for adjusting the amount of intake air passing through the first intake port.