(19)
(11) EP 0 810 368 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
18.08.1999 Bulletin 1999/33

(43) Date of publication A2:
03.12.1997 Bulletin 1997/49

(21) Application number: 97108519.6

(22) Date of filing: 27.05.1997
(51) International Patent Classification (IPC)6: F02P 17/12
(84) Designated Contracting States:
DE ES FR GB

(30) Priority: 28.05.1996 JP 133638/96

(71) Applicants:
  • TOYOTA JIDOSHA KABUSHIKI KAISHA
    Aichi-ken (JP)
  • DENSO CORPORATION
    Kariya-City Aichi-Pref. 448 (JP)

(72) Inventors:
  • Nakata, Koichi
    Toyota-shi, Aichi (JP)
  • Mogi, Kazuhisa
    Toyota-shi, Aichi (JP)
  • Kurebayashi, Youichi
    Kariya-City, Aichi-Pref. 448 (JP)

(74) Representative: Pellmann, Hans-Bernd, Dipl.-Ing. et al
Patentanwaltsbüro Tiedtke-Bühling-Kinne & Partner Bavariaring 4
80336 München
80336 München (DE)

   


(54) An apparatus for detecting misfiring of an internal combustion engine


(57) An object of the present invention is to provide an apparatus for detecting misfiring of internal combustion engines capable of detecting the misfiring reliably even though an ignition plug fouls.
When a mixture in a cylinder burns normally due to a discharge at an ignition plug 12, a voltage developed across a detection resistor 16 is fetched into a microcomputer 18 during a period other than a period where ions are generated. Thus, an insulation resistance due to fouling of the ignition plug 12 is measured. If the voltage developed across the detecting resistor 16 which is fetched into the microcomputer 18 during the period where ions are generated is equal to or larger than a threshold value, it is determined that mixture has burnt normally. If the voltage is smaller than the threshold value, it is determined that a misfire has occurred. The threshold value is corrected according to the decrease of insulation resistance. Consequently, though the ignition plug fouls, misfiring can be detected reliably.






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