Preignition detection apparatus

A preignition detecting apparatus comprising:

• a vibration detecting means for detecting vibration of an internal combustion engine;
• an abnormal vibration frequency calculating means for calculating a frequency of occurrence of abnormal vibration, wherein abnormal vibration is determined to occur when the vibration detected by the vibration detecting means is higher than a predetermined level;
• an accumulating means for accumulating the frequency calculated by the abnormal vibration frequency calculating means;
• and
• a preignition determining means for determining that preignition has occurred when the accumulated frequency becomes larger than a predetermined preignition determining value.

A preignition detecting method comprising the steps of:

• a vibration detecting step for detecting vibration of an internal combustion engine;
• an abnormal vibration occurrence interval measuring step for measuring a time interval while abnormal vibration higher than a predetermined level is being detected at the vibration detecting step;
• a frequent vibration continuing interval measuring step for measuring a time interval while the abnormal vibration occurrence interval measured at the abnormal vibration occurrence interval measuring step is shorter than a predetermined non-abnormal vibration continuing interval;
• and
• a preignition determining step for determining that preignition has occurred when the frequent vibration continuing interval measured at the frequent vibration continuing interval measuring step becomes longer than a predetermined preignition determining interval.

A preignition detecting method comprising the steps of:

• a vibration detecting step for detecting vibration of an internal combustion engine;
• an abnormal vibration frequency calculating step for calculating a frequency of occurrence of abnormal vibration, wherein abnormal vibration is determined to occur when the vibration detected at the vibration detecting step is higher than a predetermined level;
• an accumulating step for accumulating the frequency calculated at the abnormal vibration frequency calculating step;
• and
• a preignition determining step for determining that preignition has occurred when the accumulated frequency becomes larger than a predetermined preignition determining value.