Automotive engine control system with rotary encoder indexing

An automotive engine control system, comprising:

• an automobile having a variable rotation of speed engine having a plurality of cylinders served by respective spark plug means;
• an ignition system operatively connected with said spark plug means;
• an engine speed rotation sensor operatively connected with said engine for outputting the detected speed rotation to said ignition system;
• and
• an optical rotary encoder operatively connected between said engine speed rotation sensor and said ignition system for detecting a crank angle of the engine and outputting the detected crank angle to the ignition system for controlling ignition timing for said spark plug means in relation to engine speed rotation;
• in which
• both an angular signal and a reference position signal indicative of 0.degree. for an angle of interest are outputted as optical pulse signals in accordance with the angle of rotation of a rotatable pulse scale, and the angle of rotation of the pulse scale is detected based on the angular signal and the reference position signal, wherein the optical rotary encoder comprises:
• a rotatable pulse scale having a row of code pattern elements formed thereon so as to extend in the circumferential direction thereof and including in said row both a first light-transmitting or light-reflecting portion for outputting optical signals at a first, higher peak level containing both the optical angular signal and an optical reference position signal together, and a second, light-transmitting or light-reflecting portion for outputting optical signals at a second, lower peak level containing only the optical angular signal, each said element having a width in said circumferential direction, elements of said first portion being interested in elements of said second portion in said row,
• a signal processing section for discriminating between binary "1" and "0" for electric pulse signals obtained by optoelectronic conversion of said optical signals and waveform shaping of the resultant electric pulse signals based on a first threshold voltage for said angular signal, which is set lower than said lower peak level, and a second threshold voltage for said reference positional signal, which is set between said higher peak level and said lower peak level, and
• the circumferential width of each of said code pattern elements in one of said first and second portions being characteristically narrower than that of each of said code pattern elements in the other of said first and second portions, by a given amount such that the width of each pulse of the electric pulse signal at the higher peak level obtained by the waveform shaping is substantially equal to the width of each pulse of the electric pulse signal at the lower peak level obtained by the waveform shaping, each based on said first threshold voltage, so that electrical pulse signals resulting from sensing elements of said first and second portions are indicative of angular position and electrical pulse signals resulting from sensing elements of said first portion are additionally indicative of a reference position;
• wherein
• said ignition system comprising:
• a conversion table for the number of rotation and the ignition timing in which the engine rotation speed and the crank angle indicative of the ignition timing for each of the cylinders corresponding the engine rotation speed is previously set and
• a comparison means for comparing the crank angle indicative of the ignition timing and the crank angle detected by said rotary encoder;
• whereby
• the ignition timing for each of the cylinders corresponding to the rotation speed detected by said engine rotation speed sensor is outputted from the conversion table for the number of rotation and the ignition timing to the comparison means and, the comparison means outputs a signal for igniting each of the spark plugs of the corresponding cylinder when the crank angle indicative of the ignition timing and the crank angle detected by the optical rotary encoder agrees with each other.