An engine is provided, which includes a combustion chamber defined by a crown surface of a piston, an inner wall surface of a cylinder in which the piston is slidably accommodated, and a pentroof-type ceiling surface formed in a cylinder head and formed with an intake port and an exhaust port. The crown surface includes an exhaust-side bottom part, an intake-side bottom part, an exhaust-side sloped surface rising toward a center part of the crown surface from the exhaust-side bottom part, an intake-side sloped surface rising toward the center part from the intake-side bottom part, and a flat surface provided continuously between upper ends of the exhaust-side and intake-side sloped surfaces, and extending perpendicularly to a cylinder axial direction in the center part of the crown surface. A surface area of the flat surface is larger than a surface area of the exhaust-side sloped surface.

A combustion chamber structure for an internal combustion engine includes a recessed portion formed in a pent roof of a cylinder head on an upstream side of a tumble flow with respect to a spark plug.

An engine is provided, which includes a combustion chamber defined by a crown surface of a piston, an inner wall surface of a cylinder in which the piston is slidably accommodated, and a pentroof-type ceiling surface formed in a cylinder head and formed with an intake port and an exhaust port. The crown surface includes an exhaust-side bottom part, an intake-side bottom part, an exhaust-side sloped surface rising toward a center part of the crown surface from the exhaust-side bottom part, an intake-side sloped surface rising toward the center part from the intake-side bottom part, and a flat surface provided continuously between upper ends of the exhaust-side and intake-side sloped surfaces, and extending perpendicularly to a cylinder axial direction in the center part of the crown surface. A surface area of the flat surface is larger than a surface area of the exhaust-side sloped surface.

A method of controlling an engine is provided, which includes the steps of injecting main fuel by a fuel injector during an intake stroke or a compression stroke, providing a mixture gas containing fuel and air inside a cylinder, applying by an ignition device a high voltage between electrodes of a spark plug at a timing when the mixture gas is not ignited, detecting a parameter related to a current value of an electric-discharge channel generated between the electrodes, determining by a controller whether the detected parameter is within a range between a first threshold and a second threshold to determine a flowing state of a vortex inside the cylinder, operating the spark plug to carry out a supplemental ignition when the parameter is determined to be outside the range, and igniting the mixture gas by operation of the spark plug after the supplemental ignition.

An internal combustion engine for a motor vehicle has at least one cylinder, a cylinder head, and a piston which is movably mounted in the cylinder and has a combustion chamber side which delimits a combustion chamber with the cylinder head and the cylinder. The cylinder head has a combustion chamber roof, in which at least two valve seats for at least one inlet valve and at least one outlet valve are provided. The combustion chamber roof has at least one arched cylinder head section which is arranged between the at least two valve seats and points away from the combustion chamber.

A combustion chamber structure for an internal combustion engine includes a recessed portion formed in a pent roof of a cylinder head on an upstream side of a tumble flow with respect to a spark plug.

Diesel engines modified to be fueled with gaseous fuels experience problems with knocking and pre-ignition, limiting the compression ratio and efficiency of the engine. A new combustion chamber for a gaseous fueled internal combustion engine, in which the combustion chamber is defined by a cylinder head, a bore in a cylinder block and a piston reciprocating in the bore, comprises a piston portion of the combustion chamber defined by a recessed shape in a piston crown; and a head portion of the combustion chamber defined by a recessed surface in the cylinder head. A ratio between the piston portion of combustion chamber volume and the head portion of combustion chamber volume is in a range of 0.7 to 1.3.

A method of controlling an engine is provided, which includes the steps of injecting main fuel by a fuel injector during an intake stroke or a compression stroke, providing a mixture gas containing fuel and air inside a cylinder, applying by an ignition device a high voltage between electrodes of a spark plug at a timing when the mixture gas is not ignited, detecting a parameter related to a current value of an electric-discharge channel generated between the electrodes, determining by a controller whether the detected parameter is within a range between a first threshold and a second threshold to determine a flowing state of a vortex inside the cylinder, operating the spark plug to carry out a supplemental ignition when the parameter is determined to be outside the range, and igniting the mixture gas by operation of the spark plug after the supplemental ignition.

An internal combustion engine for a motor vehicle has at least one cylinder, a cylinder head, and a piston which is movably mounted in the cylinder and has a combustion chamber side which delimits a combustion chamber with the cylinder head and the cylinder. The cylinder head has a combustion chamber roof, in which at least two valve seats for at least one inlet valve and at least one outlet valve are provided. The combustion chamber roof has at least one arched cylinder head section which is arranged between the at least two valve seats and points away from the combustion chamber.

In a spark-ignition internal combustion engine in which a protrusion including an intake-side inclined surface and an exhaust-side inclined surface is formed on a top surface of a piston, and a cavity is formed in the protrusion at a position associated with a spark plug, the intake-side inclined surface and the exhaust-side inclined surface are formed in such a way that an angle defined by an orthogonal plane orthogonal to a center axis of a cylinder and the exhaust-side inclined surface) is smaller than an angle defined by the orthogonal plane and a valve head bottom surface of an exhaust valve, and an inclination angle difference between the exhaust-side inclined surface and the valve head bottom surface of the exhaust valve is larger than an inclination angle difference between the intake-side inclined surface and a valve head bottom surface of an intake valve by 3 degrees or larger.