Control of purge rate of evaporated fuel purging unit for internal combustion engine

A method of purging a canister containing an absorbent, the canister being connected to a fuel tank to permit therein to evaporated fuel from the fuel tank to be absorbed by the absorbent, the canister having a purge air inlet and a purge air outlet connected to one end of a purge passage having therein a flow control valve, the purge passage having an opposite end connected to an induction passage of an internal combustion engine at a portion downstream of a throttle valve disposed in the induction passage, the method comprising the steps of:

• detecting flow of intake air passing through the induction passage at a portion upstream of the throttle valve and generating an intake air flow indicative signal indicative of the detected flow of intake air;
• deriving an intake air flow rate from said intake air flow indicative signal;
• calculating a product of said derived intake air flow rate and a purge rate;
• incrementing a counter by a value proportional to said calculated produce;
• determining a target value of said purge rate out of various values of said purge rate contained in a table in response to said counter, the arrangement being such that, with a predetermined target value of deviation from the stoichiometry, said various values of said purge rate contained in said table are dependent on various values of said counter;
• and
• adjusting the flow control valve in response to said determined target value of said purge rate.

A method of purging a canister containing an absorbent, the canister being connected to a fuel tank to permit thereinto evaporated fuel from the fuel tank to be absorbed by the absorbent, the canister having a purge air inlet and a purge air outlet connected to one end of a purge passage having therein a flow control valve, the purge passage having an opposite end connected to an induction passage of an internal combustion engine at a portion downstream of a throttle valve disposed in the induction passage, the method comprising the steps of:

• accumulating an amount of fuel vapor purged from the canister after the engine starts;
• storing the accumulated purge fuel vapor amount at least for a predetermined time after the engine stops;
• detecting a time interval between a time at which the engine stops and a time at which the engine restarts;
• setting a purge rate characteristic based on the accumulated purge fuel vapor amount stored when the engine starts and the detected time interval, the purge rate characteristic defining purge rate as a function of accumulated purge fuel vapor amount after the engine starts;
• calculating a purge rate according to the set purge rate characteristic;
• and
• adjusting the flow control valve to provide the calculated purge rate.

A method of purging a canister containing an absorbent, the canister being connected to a fuel tank to permit thereinto evaporated fuel from the fuel tank to be absorbed by the absorbent, the canister having a purge air inlet and a purge air outlet connected to one end of a purge passage having therein a flow control valve, the purge passage having an opposite end connected to an induction passage of an internal combustion engine at a portion downstream of a throttle valve disposed in the induction passage, the method comprising the steps of:

• detecting engine operating conditions;
• calculating a required purge flow rate based on the detected engine operating conditions;
• controlling the flow control valve based on the detected engine operating conditions and the calculated required purge flow rate;
• calculating a maximum possible purge flow rate based on the detected engine operating conditions;
• selected a lower one of the required purge flow rate and the maximum possible purge flow rate after the engine starts;
• and
• correcting the required purge flow rate based on the selected purge flow rate.

A system for purging a canister containing an absorbent, the canister being connected to a fuel tank to permit thereunto evaporated fuel from the fuel tank to be absorbed by the absorbent, the canister having a purge air inlet and a purge air outlet connected to one end of a purge passage, the purge passage having an opposite end connected to an induction passage of an internal combustion engine at a portion downstream of a throttle valve disposed in the induction passage, the system comprising:

• means for detecting flow of intake air passing through the induction passage at a portion upstream of the throttle valve and generating an intake air flow indicative signal indicative of the detected flow of intake air;
• a control unit which derives an intake air flow rate from said intake air flow indicative signal;
• calculates a product of said derived intake air flow rate and a purge rate;
• increments a counter by a value proportional to said calculated produce;
• determines target value of said purge rate in response to said counter;
• and produces an output signal in response to said determined target value of said purge rate;
• and
• means for controlling the purge passage in response to said control signal.

A system for purging a canister containing an absorbent, the canister being connected to a fuel tank to permit thereinto evaporated fuel from the fuel tank to be absorbed by the absorbent, the canister having a purge air inlet and a purge air outlet connected to one end of a purge passage, the purge passage having an opposite end connected to an induction passage of an internal combustion engine at a portion downstream of a throttle valve disposed in the induction passage, the system comprising:

• means for detecting flow of intake air passing through the induction passage at a portion upstream of the throttle valve and generating an intake air flow indicative signal indicative of the detected flow of intake air;
• a control unit which derives an intake air flow rate from said intake air flow indicative signal;
• calculates a product of said derived intake air flow rate and a purge rate;
• increments a counter by a value proportional to said calculated produce;
• determines a target value of said purge rate out of various values of said purge rate contained in a table in response to said counter, the arrangement having such that, with a predetermined target value of deviation from the stoichiometry, said various values of said purge rate contained in said table are dependent on various values of said counter;
• and produces a control signal in response to said determined target value;
• and
• means for controlling the purge passage in response to said control signal.

A system for purging a canister containing an absorbent, the canister being connected to a fuel tank to permit thereinto evaporated fuel from the fuel tank to be absorbed by the absorbent, the canister having a purge air inlet and a purge air outlet connected to one end of a purge passage having therein a flow control valve, the purge passage having an opposite end connected to an induction passage of an internal combustion engine at a portion downstream of a throttle valve disposed in the induction passage, the system comprising:

• means for accumulating an amount of fuel vapor purged from the canister after the engine starts;
• means for storing the accumulated purge fuel vapor amount at least for a predetermined time after the engine stops;
• means for detecting a time interval between a time at which the engine stops and a time at which the engine restarts;
• means for setting a purge rate characteristic based on the accumulated purge fuel vapor amount stored when the engine starts and the detected time interval, the purge rate characteristic defining purge rate as a function of accumulated purge fuel vapor amount after the engine starts;
• means for calculating a purge rate according to the set purge rate characteristic;
• and
• means for adjusting the flow control valve to provide the calculated purge rate.

A system for purging a canister containing an absorbent, the canister being connected to a fuel tank to permit thereinto evaporated fuel from the fuel tank to be absorbed by the absorbent, the canister having a purge air inlet and a purge air outlet connected to one end of a purge passage having therein a flow control valve, the purge passage having an opposite end connected to an induction passage of an internal combustion engine at a portion downstream of a throttle valve disposed in the induction passage, the system comprising:

• means for detecting engine operating conditions;
• means for calculating a required purge flow rate based on the detected engine operating conditions;
• means for controlling the flow control valve based on the detected engine operating conditions and the calculated required purge flow rate;
• means for calculating a maximum possible purge flow rate based on the detected engine operating conditions;
• means for selecting a lower one of the required purge flow rate and the maximum possible purge flow rate after the engine starts;
• and
• means for correcting the required purge flow rate based on the selected purge flow rate.