Fuji Jukogyo Kabushiki Kaisha

Yasushi Nakoji

Daisuke Takahashi

Masaaki Aihara

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

An inside of an evaporated fuel processing system including a fuel tank is closed after changing an internal pressure of the evaporated fuel processing system to a target pressure value. After the closing, a diagnostic section variably sets a start timing for calculating a pressure change within the evaporated fuel processing system based on a timing when the internal pressure of the evaporated fuel processing system changes from the target pressure value to a peak pressure value. Then, a change amount between the respective internal pressure values detected by a detector at the set start timing and at a termination timing, which comes after the start timing, is calculated. The diagnostic section diagnose a leak within the evaporated fuel processing system based on the calculated change amount. Thus, the variably set start timing allows the diagnosis time to be shortened.

Diagnostic device of evaporated fuel processing system and the method thereof

In a diagnostic apparatus for an evaporative emission control system having a fuel tank is hermetically sealed under negative pressure on the basis of target inner pressure, and leak of the evaporative emission control system is judged when a diagnosis value based on a pressure variation amount after the hermetical sealing under at least negative pressure is larger than a judgment value, ECU estimates an evaporated fuel generated amount on the basis of a tank inner pressure value at the start time of a diagnosis. When the evaporated fuel generated amount thus estimated is large, target inner pressure Pteb is set to a high value, and when the evaporated fuel generated amount thus estimated is small, the target inner pressure Pteb is set to a low value.

A valve control section of a diagnostic device for an evaporated fuel processing system closes an evaporated fuel processing system at closing timing at which a value of the internal pressure detected by an internal pressure detection section reaches a preset target pressure value after a negative pressure is introduced from an inlet system to the evaporated fuel processing system. A diagnostic section of the device compares the internal pressure value at diagnostic timing which is set so as to come after the closing timing with a preset criterion threshold value so as to execute a leak diagnosis of the evaporated fuel processing system. A calculation section of the device variably sets the diagnostic timing based on the intake negative pressure value detected by the intake pressure detection section. Thus, a time period required for an early diagnosis of the leak can be optimized.

A state of an energization of a normal open type drain valve interposed between a fresh air introducing port of a canister and a drain filter is checked. And if the valve is not the energized state (open state), the tank internal pressure is checked. If the tank internal pressure is lower than a predetermined value and the state is maintained for a predetermined time, it is determined that the drain valve is close-stuck. If the drain valve is close-stuck, the pressure in the canister becomes negative, and the negative pressure is introduced in a fuel tank via a passage to an atmosphere and a pressure control valve. Closed sticking of the drain valve can be detected by checking the tank internal pressure.

Growing community of inventors

Tokyo, Japan

Yasushi Nakoji