An internal combustion engine includes a crankshaft that is rotatably supported on a crankcase via a pair of bearings and has a crank housed in a crank chamber, a to-be-detected body that is housed in the crank chamber and is supported on the crankshaft, and a detection sensor that is made to face a trajectory of the to-be-detected body and detects movement of the to-be-detected body to generate a pulse signal. The to-be-detected body is disposed on an inner side of the bearing. Thus, an internal combustion engine is provided that enables a crank angle to be detected in a state in which vibration and flexure occurring in a crankshaft are suppressed.

An internal combustion engine includes a crankshaft that is rotatably supported on the crankcase, a cylinder block that is joined to the crankcase and defines a plurality of cylinders in a V-type arrangement in which the cylinders are disposed above a virtual horizontal plane including a rotational axis of the crankshaft and intersect each other at a bank angle, a to-be-detected body that rotates integrally with the crankshaft, and a detection sensor that is mounted from an outside at a position, lower than the virtual horizontal plane, of a front face of the crankcase that receives air flow, is made to face a trajectory of the to-be-detected body, and generates a pulse signal in response to movement of the to-be-detected body. Thereby provided is a structure for disposing a detection sensor that can detect the angular velocity of a crankshaft with high precision in a so-called V-type internal combustion engine.

A reciprocating internal combustion engine includes an in-cylinder pressure sensor and a crank angle sensor. Data of calculated heat release amount in synchronization with crank angle is calculated using in-cylinder pressure after absolute pressure correction. An amount of heat release amount variation is calculated as a difference between a first calculated heat release amount at a first crank angle on an advanced side of TDC and a second calculated heat release amount at a second crank angle symmetrical about TDC. An actual heat release amount is estimated based on the amount of heat release amount variation calculated using, as the first crank angle, a crank angle on an advanced side of a combustion start point and using, as the second crank angle, a crank angle on a retarded side of a combustion end point.

To provide sensing system layout structure of an internal combustion engine that enables increasing a degree of freedom in laying out a sensing system. In sensing system layout structure of an internal combustion engine provided with a sensing system for sensing rotation of a camshaft, the internal combustion engine is provided with a driving shaft rotated in synchronization with the camshaft, the sensing system is provided with a driving shaft rotation detecting sensor arranged opposite to a rotated portion on a side of the driving shaft, and rotation of the driving shaft is sensed by the driving shaft rotation detecting sensor.

A combustion speed, for example, is estimated or evaluated, with a required accuracy, more simply than the conventional art, while reducing man-hours to produce a heat generation rate waveform of an internal combustion engine. An increase rate of a heat generation rate relative to a change in a crank angle in a heat generation rate increasing period (e.g., a first-half combustion period a) in which the heat generation rate increases after ignition of an air-fuel mixture is defined as a heat generation rate gradient b/a that is one of characteristic values of the heat generation rate waveform. The heat generation rate gradient is estimated based on a fuel density (e.g., fuel density .sub.fuel@dQpeak at heat generation rate maximum time) at a predetermined time set in advance in the heat generation rate increasing period so as to produce the heat generation rate waveform using the estimated heat generation rate gradient.

A combustion speed, for example, is estimated or evaluated, with a required accuracy, more simply than the conventional art, while reducing man-hours to produce a heat generation rate waveform of an internal combustion engine. An increase rate of a heat generation rate relative to a change in a crank angle in a heat generation rate increasing period (e.g., a first-half combustion period a) in which the heat generation rate increases after ignition of an air-fuel mixture is defined as a heat generation rate gradient b/a that is one of characteristic values of the heat generation rate waveform. The heat generation rate gradient is estimated based on a fuel density (e.g., fuel density .sub.fuel@dQpeak at heat generation rate maximum time) at a predetermined time set in advance in the heat generation rate increasing period so as to produce the heat generation rate waveform using the estimated heat generation rate gradient.

A circuit configuration for a data processing system for predicting a coordinate for at least one operation to be carried out is provided, the prediction being connected to at least one input signal and being a function of a predefined first time value and at least one predefined first value which represents another physical variable. Upon each change of the at least one input signal, a second time value is calculated in each case from the first value, and to subtract the first time value from the second time value to form a third time value, and/or to calculate a second value from the first time value, and to subtract the first value from the second value to form a third value, in order to determine from the third time value and/or the third value a state in which the at least one operation is to be carried out.