Fail-safe system of control based on the in-cylinder pressure in an internal combustion engine and a self-diagnostic system of the in-cylinder pressure sensor

摘要

PURPOSE: To enable a cylinder pressure sensor to be easily self-diagnosed at high precision by abnormality-diagnosing the cylinder pressure sensor through a process of comparing the cylinder pressure detected by the cylinder pressure sensor in non- combustion of an engine with the cylinder pressure detected in combustion. ;CONSTITUTION: While an internal combustion engine 1 is operated, the fuel injection amount Ti to the engine 1 is calculated in a control unit 12, and a driving pulse signal having the pulse width corresponding to the fuel injection amount Ti is outputted to a fuel injection valve 6 at the specific injection timing. When the difference between the integrated value Pis inn cranking of one combustion stroke at cylinder pressure P by a cylinder pressure sensor 16 and the integrated value Pi after the complete explosion is less than the set value ΔPil, and also when the difference between the integrated value Pif in fuel cut and the integrated value Pi in the normal operation is less than the specific value ΔPi2, it is judged that these states are respectively abnormal (NG), and in the discrimination of fuel property, whether the fuel is heavy or light, based on the cylinder pressure, the property is forcibly taken a heavy property, and the misfire diagnosis is canceled.;COPYRIGHT: (C)1996,JPO