Fuji Jukogyo Kabushiki Kaisha

Masaaki Aihara

Daisuke Takahashi

Yasushi Nakoji

The present invention provides a diagnostic apparatus for an evaporative emission control system which can accurately execute leak diagnosis under a stable condition. An ECU clocks a time tuntil the internal pressure value Pof the evaporative emission control system sealed at the negative pressure reaches the target internal pressure value P, sets the pressure change measuring time tbased on the clocking time t, and measures the pressure change amount Pwhich varies after the internal pressure value Pof the evaporative emission control system reaches the target internal pressure value Pfor a pressure change measuring time t. Then, the ECU sets the determination value Pbased at least on the spatial capacity of the evaporative emission control system, and determines whether the evaporative emission control system is normal or abnormal based on the pressure change amount P.

Diagnostic apparatus for evaporative emission control system

In order to achieve a correct and efficient diagnosis on an engine, it is important to search a steady state of engine operation correctly and frequently as far as possible. In this invention the steady state operation is judged by checking whether or not the average value of an engine parameter for a predetermined monitoring period is within a predetermined restriction width, whereby so many chances of monitoring for diagnosis can be provided.

Method of judging monitoring condition for diagnosis of engine

In a detecting method for deterioration of a catalyst inserted in an exhaust pipe, first, counting the number of times to cut the predetermined slice levels set in accordance with the engine operating conditions by O.sub.2 -sensors provided at the front and rear portions of the catalyst respectively. Then, a ratio of the counted numbers is calculated to judge a deterioration of a catalyst of a catalytic converter. Thus, influence of an output amplitude fluctuation of the RO.sub.2 sensor varying according to the operating condition is avoided to prevent a misjudgement of the deterioration of the catalyst.

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Tokyo, Japan

Masaaki Aihara