Control apparatus for internal combustion engine

An apparatus for controlling operation of an internal combustion engine including a plurality of cylinders, comprising:

• reference position signal generating means for generating a reference position signal indicating reference positions for the individual cylinders of said engine in synchronism with rotation of a crank shaft of said engine;
• cylinder identification signal generating means for generating a cylinder identification signal for identifying the engine cylinders in synchronism with rotation of a shaft interlocked to said crank shaft and having a rotation frequency (rpm) corresponding to a half of that of said crank shaft;
• and
• control means for controlling operation of said engine cylinders on the basis of the reference position signal and the cylinder identification signal;
• wherein said-reference position signal is comprised of equi-interval rectangular pulses each having a duty cycle of 1/2 and generated in the number of six during each rotation of said crank shaft, while said cylinder identification signal including different-interval rectangular pulses is generated a number of times during a single rotation of the interlocked shaft at a given one edge of said equi-interval rectangular pulse such that said different-interval rectangular pulse signal includes series each of four signal levels, said series differing from one another;
• and
• wherein said control means includes:
• signal level data storage means for storing the signal levels of said cylinder identification signal at every one edge of the equi-interval rectangular pulses of said cylinder reference position signals;
• reference position decision means for determining the reference positions for said individual cylinders on the basis of four successive values of said signal levels for thereby generating a decision signal;
• and
• timing control means for controlling operation of said individual cylinders on the basis of said decision signal.