An internal combustion engine includes two intake openings, opened and closed by intake valves; exhaust openings opened and closed by exhaust valves; a fuel injector having a plurality of nozzle holes; and mask parts having wall surfaces extending along outer edges of the intake openings toward the inside of the combustion chamber. The fuel injector arranged wherein the nozzle holes are positioned at the opposite exhaust opening sides from the intake openings, and the plurality of nozzle holes include a first nozzle hole, injecting in a direction with the smallest angle from a plane perpendicular to the axial direction of the cylinder. The wall surface formed wherein a height in a first nozzle hole ejection region positioned in a range of injection of a fuel spray from the first nozzle hole, when viewed in the axial direction, is lower than a height in the first nozzle hole ejection region.

When it is determined that the initial combustion is unstable, the engine speed is forcibly increased. When the engine speed is forcibly increased, fluidity in the cylinder increases. When the fluidity in the cylinder rises, homogeneity of the homogeneous air-fuel mixture is improved. Therefore, it is possible to enlarge the flame kernel. When the flame kernel is enlarged, the initial flame resulting from the flame kernel is also enlarged. Then, the initial flame becomes easy to involve the closest fuel spray thereby the initial combustion can be stabilized.

An object of the present invention is to, while forming a heat insulating layer on a squish area surface of a top surface of a piston main body, prevent generation of large cracks on the heat insulating layer and suppress damages and peeling of the heat insulating layer. To achieve this object, in the present invention, a heat insulating layer on a squish area surface of a top surface of a piston main body is made thinner than a heat insulating layer on a cavity surface of the top surface of the piston main body.

In order to achieve stable combustion in an internal combustion engine, the engine includes a fuel injection valve having a first nozzle hole and a second nozzle hole, and an spark plug disposed at a position through which the swirling flow flows, and which is at the downstream side of the flow of the swirling flow from an extension line of the first nozzle hole and at the upstream side of the flow of the swirling flow from an extension line of the second nozzle hole, for igniting a spray of fuel injected from the fuel injection valve, wherein the first nozzle hole and the second nozzle hole are formed in such a manner that the shortest distance from the extension line of the first nozzle hole to the spark plug becomes longer than the shortest distance from the extension line of the second nozzle hole to the spark plug.

A fuel injection valve capable of forming a homogeneous air-fuel mixture in homogeneous combustion at a low engine speed and a control device thereof are provided. According to the present invention, a fluid injection valve that is configured separately from a fuel injection valve and has a function of injecting a fluid is provided and a control device of the fuel injection valve includes a control unit that performs control such that fuel is injected from the fuel injection valve and then controls the fluid injection valve such that the fluid is injected from the fluid injection valve and the fuel injected from the fuel injection valve is stirred.

When it is determined that the combustion state during the catalyst warm-up control is unstable, an additional ignition is performed on the TDC side relative to the discharge period CP. In a first countermeasure example, an additional ignition period CP.sub.2 is provided on the TDC side relative to the ignition period CP.sub.1 at the normal time while performing normal ignition and injection. A second countermeasure example is carried out when it is determined that the combustion state is still unstable despite the first countermeasure example. In the second countermeasure example, an additional ignition period CP.sub.3 which is a longer period than the additional ignition period CP.sub.2 is provided instead of the additional ignition period CP.sub.2.

When it is determined that the initial combustion is unstable, the engine speed is forcibly increased. When the engine speed is forcibly increased, fluidity in the cylinder increases. When the fluidity in the cylinder rises, homogeneity of the homogeneous air-fuel mixture is improved. Therefore, it is possible to enlarge the flame kernel. When the flame kernel is enlarged, the initial flame resulting from the flame kernel is also enlarged. Then, the initial flame becomes easy to involve the closest fuel spray thereby the initial combustion can be stabilized.

A PCM (100) selects one of a CI mode or an SI mode based on the operating conditions of the engine (1). In the CI mode, the engine (1) is operated by compression ignition combustion. In the SI mode, the engine (1) is operated by spark ignition combustion. if, while the engine (1) is being operated in the CI mode, a determination is made that an estimated value (Tc) of the catalyst temperature is lower than or equal to a warming start temperature (Ts), the PCM (100) further performs first warming control to assign four cylinders (18) as CI and SI cylinders, which perform the compression ignition combustion and the spark ignition combustion, respectively, such that the four cylinders (18) alternately perform the compression ignition combustion and the spark ignition combustion in accordance with the order of combustion of the cylinders.

A combustion system is provided for an internal combustion engine including a cylinder head and a piston. In one example, a combustion system may include a cylinder head with a second cylinder surface angled relative to a first cylinder surface, an intake port coupled to the first cylinder surface, an exhaust port coupled to the second cylinder surface, and a piston with a first piston surface parallel to the first cylinder surface and a second piston surface parallel to the second cylinder surface.

An engine is configured to ignite an air-fuel mixture with an electric spark to ignite an air-fuel mixture. The engine includes: a cylinder head including a chamber partition wall having through holes and defining a main combustion chamber and a sub-combustion chamber; a fuel injector that injects fuel into the main combustion chamber; an air injector that injects air into the sub-combustion chamber; an ignition device causes an electric discharge between an ignition electrode and the chamber partition wall; and a control system that controls the fuel and air injectors, and the ignition device. At a compression stroke during a warm-up operation, the fuel is injected throughout a first period, and the air is injected throughout a second period at least partially overlapping the first period. At a power stroke during the warm-up operation, the electric discharge is caused after the fuel is injected.