The invention is provided with an ignition control section and an injection control section. When partial compression ignition combustion is carried out, the ignition control section causes an ignition plug to carry out: main ignition in which a spark is generated in a late period of a compression stroke or an initial period of an expansion stroke to initiate SI combustion; and preceding ignition in which the spark is generated at earlier timing than the main ignition. Also, when the partial compression ignition combustion is carried out, the injection control section causes an injector to inject fuel at such timing that the fuel exists in a cylinder at an earlier time point than the preceding ignition. Ignition timing of the preceding ignition is set to be more retarded when fuel concentration specified by a fuel concentration specification section is low than when the fuel concentration is high.

Provided is an ignition control section and an injection control section. When partial compression ignition combustion is carried out, the ignition control section causes an ignition plug to carry out: main ignition in which a spark is generated in a late period of a compression stroke or an initial period of an expansion stroke to initiate SI combustion; and preceding ignition in which the spark is generated at earlier timing than the main ignition. Also, when the partial compression ignition combustion is carried out, the injection control section causes an injector to inject fuel at such timing that the fuel exists in a cylinder at an earlier time point than the preceding ignition. Ignition timing of the preceding ignition is set to be more advanced when an in-cylinder temperature specified by an in-cylinder temperature specification section is high than when the in-cylinder temperature is low.

The invention is provided with an ignition control section and an injection control section. When partial compression ignition combustion is carried out, the ignition control section causes an ignition plug to carry out: main ignition in which a spark is generated in a late period of a compression stroke or an initial period of an expansion stroke to initiate SI combustion; and preceding ignition in which the spark is generated at earlier timing than the main ignition. Also, when the partial compression ignition combustion is carried out, the injection control section causes an injector to inject fuel at such timing that the fuel exists in a cylinder at an earlier time point than the preceding ignition. Ignition timing of the preceding ignition is set to be more retarded when fuel concentration specified by a fuel concentration specification section is low than when the fuel concentration is high.

A fuel injection control device for an engine is provided. A fuel injector with multiple nozzle holes forms a lean mixture gas inside a combustion chamber, a spark plug ignites to cause the mixture gas to start combustion accompanied by flame propagation, then combust by self-ignition. A first atomized fuel spray injected from a first nozzle hole and a second atomized fuel spray injected from a second nozzle hole separate from each other by a swirl flow, and a third atomized fuel spray injected from a third nozzle hole and a fourth atomized fuel spray from a fourth nozzle hole approach each other by the swirl flow so that a first area and a second area where mixture gas is richer are formed inside the combustion chamber. The fuel injector sequentially performs first, second, and third injections with an injection interval therebetween in an intake stroke.

The engine control method includes a fuel supply step and an ignition step. In the fuel supply step, the injector supplies fuel into a combustion chamber. In the ignition step, an spark plug arranged in the combustion chamber makes a flame after the supply of the fuel into the combustion chamber and at a timing when a flow strength in the combustion chamber is greater than a predetermined value in a compression stroke during or before a post-mid stage where the compression stroke is divided into four stages of a pre-stage, a pre-mid stage, a post-mid stage, and a post-stage.

The center injection engine is an engine equipped with the direct injector and an ignition apparatus at center of a ceiling part of the combustion chamber. The positive tumble flow flows from the intake port side to the exhaust port side on the ceiling part side of the combustion chamber, and also flows from the exhaust port side to the intake port side on the piston top part side. The ECU calculates the injection timing of the direct injector based on the engine load. In the first injection control, the higher the engine load becomes, the more the end crank angle is retarded.

A combustion chamber structure for an engine includes a combustion chamber where SI combustion by spark ignition and CI combustion by self-ignition are conducted. A crown surface includes a cavity recessed to have a bowl-shape; a pair of first raised portions having a mound-shape along a pent roof shape; and a second raised portion provided to protrude at a position orthogonal to a ridge extending direction of the pair of first raised portions. With a height of the first raised portion relative to a height position of a deepest portion of the cavity being represented as H1 and a height of the second raised portion being represented as H2, H1/H2 as a ratio of the height H1 of the first raised portion to the height H2 of the second raised portion is set to be in a range of 1.92 or more and 2.75 or less.

A method for determining the cylinder air-charge of an internal combustion engine in a non-fired operation, wherein a method for determining the cylinder air-charge in a fired operation is performed. According to the invention, provision is made that in the method for determining the cylinder air-charge in the fired operation, a correction factor is provided as a function of engine speed and engine load which adjusts the value of the cylinder air-charge determined by the method in the fired operation to the non-fired operation. Thus, the previously known methods can be improved and made more efficient, in particular in view of the deviations of up to 30% between the cylinder air-charge values in the non-fired operation and the modeled values of the fired operation.

A control strategy includes: after an engine is energized, the continuously variable valve lift mechanism self learning to determine a current position; if the self learning is successful, the continuously variable valve lift mechanism being located at a maximum lift position, preparing for starting the engine, and determining a regulating mode based on a starting temperature, wherein at the time of normal temperature start, regulation is performed from the maximum lift position to a minimum lift position, and at the time of low temperature start, regulation is performed from the maximum lift position to a position where the two valves for the same cylinder have a maximum lift difference; if the self learning fails, entering a preliminary start mode; entering a CVVL control mode based on an operation condition of the engine; and powering off the engine.

A control apparatus for an engine includes an engine, a state quantity setting device, a spark plug, and a controller. The spark plug ignites air-fuel mixture at predetermined ignition timing so that unburned air-fuel mixture combusts by autoignition after start of combustion of the air-fuel mixture by the ignition, and the controller adjusts a heat amount ratio in accordance with an operation state of the engine through change of the ignition timing, the heat amount ratio representing an index associated with a ratio of an amount of heat generated when the air-fuel mixture combusts by flame propagation with respect to a total amount of heat generated when the air-fuel mixture combusts in the combustion chamber.