Misfire detector device for use in an internal combustion engine

A misfire detector device for use in an internal combustion engine comprising:

• an ignition coil including a primary coil and a second coil;
• an electrical interrupter circuit which on-off actuates a primary current flowing through a primary circuit of the ignition coil to induce a sparkplug voltage;
• means provided in a secondary circuit of the ignition coil for preventing a current flowing back to the ignition coil;
• a multi-electrode type spark plug which is to be energized from the ignition coil;
• a voltage divider circuit which detects a divided voltage of the sparkplug voltage applied across electrode of the spark plug;
• a sparkplug voltage detector circuit which detects an attenuation time period length of an attenuation characteristic of a sparkplug voltage waveform presented subsequent to a time period predetermined after an end of a spark action of the spark plug;
• and
• a distinction circuit which determines on the basis of the attenuation time period length of the attenuation characteristic whether or not the spark ignites an air-fuel mixture injected in a cylinder of an internal combustion engine.

A misfire detector device for use in an internal combustion engine comprising:

• an ignition coil including a primary coil and a secondary coil;
• an interrupter circuit which on-off actuates a primary current flowing through a primary circuit of the ignition coil to induce a sparkplug voltage;
• means provided in a secondary circuit of the ignition coil for preventing a current flowing back to the ignition coil;
• a multi-electrode type spark plug which is to be energized from the ignition coil;
• a voltage charging circuit which induces a sparkplug voltage in the secondary circuit of the ignition coil so as to electrically charge a stray capacity inherent in the spark plug at a time predetermined after an end of a spark action of the spark plug when the engine runs at a low revolution with a low load;
• a voltage divider circuit which detects a divided voltage of the sparkplug voltage applied across electrodes of the spark plug;
• a sparkplug voltage detector circuit which detects an attenuation characteristic of a divided sparkplug voltage waveform presented subsequent to a time period predetermined after an end of the spark action when the engine runs at a high revolution, and detecting an attenuation characteristic of a divided sparkplug voltage waveform derived from the voltage charging circuit when the engine runs at a low revolution with a low load;
• and
• a distinction circuit which determines on the basis of the attenuation characteristic whether or not the spark ignites an air-fuel mixture injected in a cylinder of an internal combustion engine.