Preignition detecting system

A preignition detecting system comprising:

• ignition timing control means for determining an ignition timing depending upon the conditions in which an internal combustion engine is operating;
• abnormal vibration determining means for so determining that abnormal vibration is occurring when a vibration component within a predetermined frequency range, as a result of detecting vibration of the internal combustion engine, is larger than a predetermined level or when vibration within a predetermined frequency range occurs more often than a predetermined frequency after the ignition is effected by said ignition timing control means;
• delay angle correction means for delaying the ignition timing determined by said ignition timing control means when it is determined by said abnormal vibration determining means that abnormal vibration is occurring;
• continuation-of-delay determining means for determining whether or not the ignition timing is being continuously delayed by said delay angle correction means;
• abnormal vibration increment determining means for determining whether or not abnormal vibration is increasing based upon a vibration component within a predetermined frequency range when it is determined by said abnormal vibration determining means that abnormal vibration is occurring;
• and
• preignition determining means for so determining that preignition is occurring when it is determined by said continuation-of-delay determining means that the ignition timing is being continuously delayed and when it is determined by said abnormal vibration increment determining means that abnormal vibration is increasing.

A preignition detecting method comprising steps of:

• ignition timing control step for determining an ignition timing depending upon the conditions in which an internal combustion engine is operating;
• abnormal vibration determining step for determining that abnormal vibration is occurring when a vibration component within a predetermined frequency range as a result of detecting vibration of the internal combustion engine is larger than a predetermined level or when vibration within a predetermined frequency range occurs more often than a predetermined frequency after the ignition is effected at said ignition timing control step;
• abnormal vibration timing detecting step for detecting a timing at which it is determined at said abnormal vibration determining step that abnormal vibration is occurring;
• and
• a preignition determining step for so determining that preignition is occurring depending upon a time difference between the ignition timing determined at said ignition timing control step and the timing of abnormal vibration detected at said abnormal vibration timing detecting step.

A preignition detecting method comprising steps of:

• ignition timing control step for determining an ignition timing depending upon the conditions in which an internal combustion engine is operating;
• abnormal vibration determining step for so determining that abnormal vibration is occurring when a vibration component within a predetermined frequency range, as a result of detecting vibration of the internal combustion engine, is larger than a predetermined level or when vibration within a predetermined frequency range occurs more often than a predetermined frequency after the ignition is effected at said ignition timing control step;
• delay angle correction means for delaying the ignition timing determined said ignition timing control step when it is determined at said abnormal vibration determining step that abnormal vibration is occurring;
• continuation-of-delay determining step for determining whether or not the ignition timing is being continuously delayed at said delay angle correction step;
• abnormal vibration increment determining step for determining whether or not abnormal vibration is increasing based upon a vibration component within a predetermined frequency range when it is determined at said abnormal vibration determining step that abnormal vibration is occurring;
• and
• preignition determining step for so determining that preignition is occurring when it is determined at said continuation-of-delay determining step that the ignition timing is being continuously delayed and when it is determined at said abnormal vibration increment determining step that abnormal vibration is increasing.