Ignition system for an internal combustion engine

An ignition system for a multi-cylinder internal combustion engine, which comprises:

• (a) a crank angle sensor for detecting crank angles and generating a plurality of crank angle signals a, b and c corresponding thereto;
• (b) a load sensor detecting intake air flow rate of the engine and generating engine load signals Q corresponding thereto;
• (c) an engine speed sensor for detecting engine speed and generating engine speed signals N corresponding thereto;
• (d) an ignition advance-angle control unit including:
• (1) a memory unit for storing reference ignition advance-angle values A corresponding to engine load and engine speed;
• (2) a central processing unit connected to said load sensor, said speed sensor, and said memory unit for reading the detected engine load signal Q and engine speed N, determining appropriate reference ignition advance-angle values A corresponding to the detected engine load and engine speed in table look-up method, and executing calculations to obtain advance-angle control signals Nc;
• (3) a register connected to said central processing unit for temporarily storing the advance-angle control signals Nc;
• (4) a counter connected to said crank angle sensor for counting the crank angle signal c to determine crank angle positions and deriving a counted value d corresponding thereto, said counter being reset by the crank angle signal b;
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• (5) a comparator connected to said counter and said register for comparing the counted value d from said counter with the advance-angle control signal Nc from said register and generating ignition signals e when the counted value d matches the advance-angle control signal Nc;
• (e) a booster connected to a power supply for boosting a supply voltage of the power supply and deriving a boosted supply voltage corresponding thereto;
• (f) an ignition unit including:
• (1) a distributing unit connected to said crank angle sensor and said comparator for distributing the ignition signals e from said comparator on the basis of the crank angle signal a from said crank signal sensor and generating output signals f, g, h and i classified into the respective cylinders;
• (2) a plurality of switching control units connected to said distributing unit for generating switching control signals j, k, l, and m in response to the output signals f, g, h and i from said distributing unit;
• (3) a plurality of thyristors, each having gate and anode terminals respectively connected to said respective control units and said booster, said thyristors being sequentially fired in response to the switching control signals j, k, l, and m from said switching control unit in the ignition order of the cylinders;
• (4) a plurality of ignition energy condensers each having a terminal connected to the anode terminal of a separate one of said thyristors for directly charging ignition energy from said booster and discharging the charged ignition energy through said respective thyristors in response to the switching control signals j, k, l, and m from said switching control unit;
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• (5) an oscillation interrupting unit connected to said booster and said distributing unit for interrupting the oscillation of said booster for a predetermined period of time during which said condensers are being discharged in order to prevent current from flowing from said booster to said condenser whenever the ignition signals e are derived by said distributing unit;
• (g) a plurality of ignition coils, each having a first primary side terminal which is separately connected to a second of one of said ignition energy condensers and a second primary side terminal which is separately connected to the cathode of one of said thyristors for generating high-voltage on the respective secondary side thereof when ignition energy charged in said respective ignition energy condensers is discharged through said thyristors connected to it in response to the switching control signals j, k, l and m from said switching control unit;
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• (h) a plurality of ignition plugs, each of the plugs being separately connected to the secondary side of one of said ignition coils so a spark is generated between electrodes of each plug in response to the high-voltage generated by the ignition coil connected to the plug.