In a piston of an internal combustion engine in which a recessed portion that holds an intake air swirling flow is formed on a crown surface of the piston, the crown surface includes a heat insulating film formation portion having a heat insulating film whose thermal conductivity is lower than a base material of the piston, the heat insulating film whose thermal capacity per volume is smaller than the base material of the piston, and a heat insulating film non-formation portion provided at a position on the more outside of a cylinder bore side of the internal combustion engine than the heat insulating film formation portion, the heat insulating film non-formation portion not having the heat insulating film.

An air intake apparatus of an internal combustion engine includes an intake passage, an intake air flow control valve, a housing portion configured to house the intake air flow control valve, a swirl opening arranged at a first side of the intake air flow control valve to generate swirl, and a tumble opening arranged at a second side of the intake air flow control valve to generate tumble. The swirl opening is provided at one of the intake air flow control valve and a portion between the intake passage and the intake air flow control valve, the tumble opening being provided at the other of the intake air flow control valve and the portion between the inner surface of the intake passage and the intake air flow control valve. The intake air flow control valve rotates to achieve a switching between a swirl state and a tumble state.

An air intake apparatus of an internal combustion engine includes an intake passage, an intake air flow control valve, a housing portion configured to house the intake air flow control valve, a swirl opening arranged at a first side of the intake air flow control valve to generate swirl, and a tumble opening arranged at a second side of the intake air flow control valve to generate tumble. The swirl opening is provided at one of the intake air flow control valve and a portion between the intake passage and the intake air flow control valve, the tumble opening being provided at the other of the intake air flow control valve and the portion between the inner surface of the intake passage and the intake air flow control valve. The intake air flow control valve rotates to achieve a switching between a swirl state and a tumble state.

In an internal combustion engine which performs a homogeneous lean combustion mode and a stratified lean combustion mode, there is provided a new internal combustion engine control device capable of obtaining a stable combustion state by decreasing influences of delay of an air flow and a degree of change of a transient state and smoothly performing switching between the homogeneous lean combustion mode and the stratified lean combustion mode. Accordingly, in the present invention, when switching between the stratified lean mode in which a compression stroke injection is performed by a direct injection injector 7 and the homogeneous lean combustion mode in which an intake stroke injection is performed by the direct injection injector 7 is performed, a predetermined delay time t is provided from at least a switching operation of a tumble control valve 6, a switching operation between the compression stroke injection and the intake stroke injection is performed, and the delay time t is set so as to correspond to a magnitude of the degree of change L of the transient state. A switching timing between the compression stroke injection and the intake stroke injection is controlled according to the flow delay of an air control system such as the tumble control valve 6 and the degree of change L of the transient state, and thus, it is possible to improve combustion stability in a combustion chamber.

In an internal combustion engine which performs a homogeneous lean combustion mode and a stratified lean combustion mode, there is provided a new internal combustion engine control device capable of obtaining a stable combustion state by decreasing influences of delay of an air flow and a degree of change of a transient state and smoothly performing switching between the homogeneous lean combustion mode and the stratified lean combustion mode. Accordingly, in the present invention, when switching between the stratified lean mode in which a compression stroke injection is performed by a direct injection injector 7 and the homogeneous lean combustion mode in which an intake stroke injection is performed by the direct injection injector 7 is performed, a predetermined delay time t is provided from at least a switching operation of a tumble control valve 6, a switching operation between the compression stroke injection and the intake stroke injection is performed, and the delay time t is set so as to correspond to a magnitude of the degree of change L of the transient state. A switching timing between the compression stroke injection and the intake stroke injection is controlled according to the flow delay of an air control system such as the tumble control valve 6 and the degree of change L of the transient state, and thus, it is possible to improve combustion stability in a combustion chamber.

A control system for a compression-ignition engine includes a combustion chamber, an injector, an ignition plug, a sensor device, and a controller having a circuitry. The ignition plug forcibly ignites mixture gas to start combustion accompanied by flame propagation of a part of the mixture gas, and again ignites remaining unburnt mixture gas at a timing at which the unburnt mixture gas combusts by self-ignition. The controller is configured to execute an ignition controlling module to output an ignition signal to the ignition plug before a target timing so that the unburnt mixture gas self-ignites at the target timing, an ignition timing estimating module to estimate an actual CI timing indicative of a timing at which the unburnt mixture gas actually self-ignited based on an in-cylinder pressure parameter, and an in-cylinder temperature determining module to determine the in-cylinder temperature at a given crank angle based on the estimated result.

A control system for a compression ignition engine includes a combustion chamber, a throttle valve, an injector, an ignition plug, an EGR system, a sensor device and a controller. The controller includes a first mode module, a second mode module and a changing module configured to change an engine mode from a first mode to a second mode in response to a change demand. The changing module outputs signals to the throttle valve and the injector in response to the demand so that an air-fuel ratio of mixture gas becomes a stoichiometric air-fuel ratio or a substantially stoichiometric air-fuel ratio, and outputs a signal to the EGR system so that an EGR gas amount decreases more than before the demand, and when the EGR gas amount is determined to be decreased to a given amount, the changing module permits that the second mode module starts the second mode.

A control system for a compression ignition engine is provided, which includes a sensor and a cylinder count control module which changes between all-cylinder and reduced-cylinder operations when the compression ignition combustion is performed at a given lean air-fuel ratio. The cylinder count control module executes a preparation control to change from the all-cylinder operation to the reduced-cylinder operation when the change is demanded. In the preparation control, the cylinder count control module outputs a signal to a throttle valve to execute an air amount increase processing, outputs a signal to a fuel injection valve to execute a fuel amount increase processing, and outputs a signal to an ignition plug to execute a retard processing. The cylinder count control module ends the fuel amount increase processing and the retard processing when it is determined that an air-fuel ratio is in a given air-fuel ratio state, and starts the reduced-cylinder operation.

A control system for a compression ignition engine is provided, which includes a sensor and a cylinder count control module which changes between all-cylinder and reduced-cylinder operations when the compression ignition combustion is performed at a given lean air-fuel ratio. The cylinder count control module executes a preparation control to change from the all-cylinder operation to the reduced-cylinder operation when the change is demanded. In the preparation control, the cylinder count control module outputs a signal to a throttle valve to execute an air amount increase processing, outputs a signal to a fuel injection valve to execute a fuel amount increase processing, and outputs a signal to an ignition plug to execute a retard processing. The cylinder count control module ends the fuel amount increase processing and the retard processing when it is determined that an air-fuel ratio is in a given air-fuel ratio state, and starts the reduced-cylinder operation.

An airflow control valve structure includes a metallic pivot shaft-and a valve body. The valve body includes a connection portion connected to the pivot shaft and a resin valve portion. The pivot shaft includes first and second pivot shaft side press-fit portions. The connection portion includes a first valve side press-fit portion formed integrally with the valve portion and a metallic fitting member including a second valve side press-fit portion. The first valve side press-fit portion is fitted to the first pivot shaft side press-fit portion at an angular position at which a phase of the valve portion is matched with a phase of the pivot shaft. The second valve side press-fit portion is fitted to the second pivot shaft side press-fit portion. The first pivot shaft side press-fit portion is longer than the second valve side press-fit portion.