An engine system is provided, including a controller which controls devices of an engine at a given engine speed so that, when a demanded engine load is a first load, a mass ratio (G/F) of intake air inside a cylinder (containing fresh air and burnt gas) to fuel is a first G/F and mixture gas inside the cylinder combusts by flame-propagation, when the demanded load is a second load (<the first load), the G/F is a second G/F (>the first G/F) and an injection center-of-gravity is at a timing such that the entire mixture gas combusts by CI combustion, and when the demanded load is between the first and second loads, the G/F is at a third G/F (between the first and second G/Fs) and the injection center-of-gravity is at a later timing such that at least part of the mixture gas combusts by the CI combustion.

An ignition control system performs discharge generation control, in which a discharge spark is generated, once or a plurality of times during a single combustion cycle. The ignition control system successively calculates an approximate energy density based on a secondary current and a discharge path length. During a predetermined period after blocking of a primary current is performed during a single combustion cycle, the ignition control system calculates an integrated value by integrating the discharge path length at this time, based on the approximate energy density being greater than a predetermined value. The ignition control system performs the discharge generation control again based on the calculated integrated value being less than a first threshold.

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.

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. Timing of the preceding ignition is more advanced when a swirl flow is gentle than when the swirl flow is strong.

An engine control apparatus includes an ignition control section and an injection control section. When the 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 a expansion stroke to initiate the 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 the injector to inject fuel at such timing that the fuel exists in a cylinder at an earlier time point than the preceding ignition. The energy of the preceding ignition is set to be higher when the in-cylinder pressure specified by the in-cylinder pressure specification section is high than when the in-cylinder pressure is low.

A method of controlling an engine is provided, the method including 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 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, injecting supplemental fuel by the fuel injector after the main fuel injection when the parameter is determined to be outside the range, and igniting the mixture gas by the ignition device using the spark plug after the supplemental fuel injection.

A method of controlling an engine is provided, the method including 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 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, injecting supplemental fuel by the fuel injector after the main fuel injection when the parameter is determined to be outside the range, and igniting the mixture gas by the ignition device using the spark plug after the supplemental fuel injection.

The internal-combustion-engine combustion state control apparatus includes an ignition control means that generates two or more ignition signals during a single compression stroke or a single combustion stroke of an internal combustion engine, a high voltage means that makes an ignition plug, provided in a combustion chamber of the internal combustion engine, perform an ignition discharge based on the ignition signal, an ignition-discharge parameter detection circuit that detects a parameter indicating a state of the ignition discharge, an ignition-discharge duration detection means that detects two or more ignition discharge durations, based on an output signal of the ignition-discharge parameter detection circuit, and an abnormal-combustion determination means that diagnoses a combustion state of the internal combustion engine, based on at least one of the two or more ignition discharge durations; an abnormal-combustion-suppression control means is made to operate based on the result of a determination by the abnormal-combustion determination means.

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. Timing of the preceding ignition is set to be more retarded when an engine speed is high than when the engine speed is low.

An engine system is provided, which includes a cylinder block, a cylinder head, a piston, a main combustion chamber, a subchamber, an injector that injects fuel into the main combustion chamber, a main spark plug that ignites a mixture gas inside the main combustion chamber, a subspark plug that ignites the mixture gas inside the subchamber, and a controller electrically connected to the injector and the main spark plug and the subspark plug. In a low-load range where an engine load is below a given reference load, the controller controls the main spark plug and the subspark plug so that the subignition is performed after performing the main ignition, and the controller retards the timing of the subignition in a high-speed range where an engine speed is above a given reference engine speed, compared with a low-speed range below the reference engine speed.