To accurately evaluate combustion stability in consideration of the effect of the trend even at the time of the transient operation. The present invention is configured to have a combustion energy calculation unit that calculates a combustion energy W_t of one combustion cycle in an internal combustion engine, a trend calculation unit that calculates a trend Tr of change in the combustion energy W_t calculated by the combustion energy calculation unit in a plurality of the combustion cycles, and a combustion stability judgment unit that judges combustion stability based on the combustion energy W_t in the plurality of combustion cycles and the trend Tr of change calculated by the trend calculation unit.

An internal combustion engine includes: a piston guided by a cylinder to reciprocate along a cylinder axis and forming a combustion chamber with a crown surface facing a cylinder head; and a fuel injection valve having an injection port facing the combustion chamber and injecting fuel to a forward tumble flow in the combustion chamber. A ridge formed on the crown surface rises toward a ceiling surface side relative to a reference plane, orthogonal to the cylinder axis and including an outer peripheral edge of the crown surface, and has a ridge line formed by a curved surface to surround a recessed part. The recessed part is recessed toward a center of the crown surface in a direction orthogonal to a virtual plane including the cylinder axis and parallel to a rotation axis of a crankshaft, and is recessed toward the center in an axial direction of the crankshaft.

Methods and systems are provided for a fuel injector. In one example, a system comprises an injector spool valve having a fuel outlet shaped to flow fuel to different portions of a nozzle inlet based on an actuation of the injector spool valve, thereby adjusting a fuel injection angle of a fuel injection.

Combustion cylinder (10) of an internal combustion engine, having a combustion chamber wall (20), which surrounds a combustion chamber (30), and a combustion chamber cover (40), which closes off the combustion chamber (30) on the upper side, wherein at least one inlet valve (50) for letting in a fluid is arranged on an inlet side (42) in the combustion chamber cover (40), and at least one outlet valve (60) for letting out a fluid is arranged on an outlet side (44) in the combustion chamber cover (40), wherein, furthermore, a prechamber spark plug (70) is arranged between the at least one inlet valve (50) and the at least one outlet valve (60) in the combustion chamber cover (40), which prechamber spark plug is arranged between the at least one inlet valve (50) and an injector (80) for injecting combustion fluid.

Emission of unburned hydrocarbons and soot is reduced while ensuring startability (ignitability) in a cold start mode of an internal combustion engine. Thus, fuel is injected with a first injection rate as an injection rate of a fuel injection valve 100 in a warm state in which a temperature of an engine 30 is equal to or higher than a set temperature, and the fuel is injected with a second injection rate lower than the first injection rate as the injection rate of the fuel injection valve 100 in a cold state in which the temperature of the engine 30 is lower than the set temperature at the same fuel pressure as that in the warm state.

An internal combustion engine includes: a piston guided by a cylinder to reciprocate along a cylinder axis and forming a combustion chamber with a crown surface facing a cylinder head; and a fuel injection valve having an injection port facing the combustion chamber and injecting fuel to a forward tumble flow in the combustion chamber. A ridge formed on the crown surface rises toward a ceiling surface side relative to a reference plane, orthogonal to the cylinder axis and including an outer peripheral edge of the crown surface, and has a ridge line formed by a curved surface to surround a recessed part. The recessed part is recessed toward a center of the crown surface in a direction orthogonal to a virtual plane including the cylinder axis and parallel to a rotation axis of a crankshaft, and is recessed toward the center in an axial direction of the crankshaft.

A fuel injection device is provided with reduced adherence of fuel spray with respect to an intake valve, a wall surface in an engine cylinder, or a piston. The fuel injection device includes a valve body and a seat surface to perform sealing of fuel cooperatively and injection holes. Inlet opening surfaces are formed on the seat surface. A first injection hole and a second injection hole arranged closest to the first injection hole. The first injection hole is larger than the second injection hole in an injection hole angle to be an angle formed by a normal direction of the seat surface and a center axis of the injection hole. The second injection hole is larger than the first injection hole in an area of a cross-section perpendicular to the center axis of the injection hole.

The invention relates to an internal combustion engine and to a method for operating the internal combustion engine, which has at least one cylinder having a combustion chamber, the combustion chamber being bounded by a cylinder roof, a cylinder wall and a movable cylinder piston, a multi-hole injection nozzle and a spark plug being arranged in a central position in the cylinder roof, the multi-hole injection nozzle injecting fuel into the combustion chamber at injection pressures of >/=300 bar by means of a plurality of injection jets. It is provided that at least one injection jet (i>/=1) injects fuel into a three-dimensional space within the combustion chamber on the intake side, which space lies below an opening of at least one intake valve (104A, 104B) with respect to the direction of the longitudinal central axis (Z) of the cylinder, and at least four injections jets (i>/=4) inject fuel into a three-dimensional space of the combustion chamber on the exhaust side, which space lies below an opening of at least one exhaust valve (105A, 105B).

A nozzle body has an injection hole configured to inject fuel and a fuel passage connecting to the injection hole. A needle is configured to open and close the fuel passage to switch between fuel injection from the injection hole and stop of the fuel injection. An injection hole axis is an imaginary line extending along a center of the injection hole. An injection hole perpendicular cross section is a cross section of the injection hole perpendicular to the injection hole axis. The injection hole perpendicular cross section has a flat shape. The injection hole perpendicular cross section has an area that gradually expands from an inlet of the injection hole to an outlet of the injection hole while maintaining a similar shape.

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 inclination angle of the exhaust-side inclined surface is smaller than an inclination angle of the intake-side inclined surface, and a difference in inclination angle between the intake-side inclined surface and the exhaust-side inclined surface is 4 degrees or larger.