Abstract: The internal combustion engine has a valve driving mechanism (VM) capable of changing the valve-opening characteristic of at least one of an intake valve (Vi) and an exhaust valve (Ve), an in-cylinder pressure sensor for detecting the in-cylinder pressure in a combustion chamber and ECU. ECU calculates the variation amount of the in-cylinder pressure caused by the valve-overlap of the intake valve (Vi) and the exhaust valve (Ve), and based on this variation amount of the in-cylinder pressure and the in-cylinder pressure detected at a predetermined timing in the compression stroke, calculates an amount of air sucked in the combustion chamber, as well as, based on this calculated intake air amount, determines the ignition timing. The amount of air sucked in the combustion chamber is accurately and costlessly calculated, and the ignition timing is optimally determined by using the calculated air amount.

Abstract: In this apparatus, maintaining control (time t1 to t2) which instructs fixing of the open timing VVT of an intake valve is executed in a predetermined low load state. Subsequently, there are executed changing control which instructs changing of the open timing VVT by a predetermined amount (time t2), and maintaining control which again instructs fixing of the open timing VVT of the intake valve (time t2 to t3). An intake-valve control apparatus is determined to be “anomalous” when an change amount ?ave (=ave2?ave1) between the average ave1 of a large number of sample values of ?MFB? (combustion percentage increase amount within a predetermined crank angle range in an expansion stroke) during the maintaining control before execution of the changing control and the average ave2 of a large number of sample values of ?MFB? during the maintaining control after execution of the changing control is less than a predetermined value C.

Abstract: A control device of an internal combustion engine that can accurately estimate an NOx concentration in exhaust gas by using a cylinder internal pressure as basic data. A cylinder internal pressure sensor provided to the internal combustion engine detects a cylinder internal pressure P?. An internal energy correlation value (?V·dP?/d?·??) having correlation with internal energy consumed in the cylinder is calculated based on the cylinder internal pressure P? and an in-cylinder volume V? (? represents a crank angle). The internal energy correlation value is standardized by a load ratio KL, then corrected by a function f(kl) as for a load factor KL so as to calculate an NOx concentration estimated value [NOx]={(?V·dP?/d?·??)/KL}×f(kl).

Abstract: This control apparatus estimates a full combustion correspondence period CP, which is the period from an ignition timing SA to a combustion completion time CAe, and controls a VVT advancement amount (burnt gas quantity, overlap period, intake valve open timing) such that the estimated full combustion correspondence period CP coincides with a constant target full combustion correspondence period CPtgt. The full combustion correspondence period CP substantially maintains a one-to-one relation with the VVT advancement amount at which HC, CO2, etc. start to increase, even when the ignition timing SA changes. Thus, even when the ignition timing changes, the burnt gas quantity (overlap period) can be properly controlled. As a result, without increasing the discharge quantities of HC and CO, the discharge quantity of NOX can be reduced. In addition, pumping loss can be reduced, whereby fuel consumption can be improved.

Abstract: A control system includes: a detecting device that detects the transition in the cumulative amount of heat generated in a combustion chamber based on the pressure in the combustion chamber in an expansion stroke; and a controller that controls the amount of exhaust gas contained in an air-fuel mixture in the combustion chamber such that the amount of change in the cumulative amount of heat generated in the combustion chamber through a predetermined crank angle range will become a predetermined value.

Abstract: The internal combustion engine has a valve driving mechanism (VM) capable of changing the valve-opening characteristic of at least one of an intake valve (Vi) and an exhaust valve (Ve), an in-cylinder pressure sensor for detecting the in-cylinder pressure in a combustion chamber and ECU. ECU calculates the variation amount of the in-cylinder pressure caused by the valve-overlap of the intake valve (Vi) and the exhaust valve (Ve), and based on this variation amount of the in-cylinder pressure and the in-cylinder pressure detected at a predetermined timing in the compression stroke, calculates an amount of air sucked in the combustion chambers, as well as, based on this calculated intake air amount, determines the ignition timing. The amount of air sucked in the combustion chamber is accurately and costlessly calculated, and the ignition timing is optimally determined by using the calculated air amount.