Evaporative fuel-processing system for internal combustion engines

In an evaporative fuel-processing system for an internal combustion engine having an intake system, and a fuel tank, including evaporative emission control means having a canister for adsorbing evaporative fuel generated within said fuel tank, a charging passage extending between said canister and said fuel tank, a purging passage extending between said canister and said intake system of said engine, an open-to-atmosphere passage for communicating an interior of said canister with the atmosphere, a purge control valve arranged in said purging passage, for opening and closing said purging passage, an open-to-atmosphere valve arranged in said open-to-atmosphere passage, for selectively opening and closing said open-to-atmosphere passage, and pressure detecting means arranged in said evaporative emission control means, for detecting pressure within said evaporative emission control means,

• the improvement comprising:
• negative pressure-introducing means for introducing negative pressure from said intake system of said engine into said evaporative emission control means and said fuel tank by opening said purge control valve and closing said open-to-atmosphere valve;
• and
• purge control means operable when said negative pressure-introducing means is operating, for comparing a value of said pressure within said evaporative emission control means detected by said pressure detecting means with a predetermined negative pressure value, and for controlling said purge control valve so as to vary a flow rate of said evaporative fuel to be purged into said intake system, based on results of said comparison.

In an evaporative fuel-processing system for an internal combustion engine having an intake system, and a fuel tank, including evaporative emission control means having a canister for adsorbing evaporative fuel generated within said fuel tank, a charging passage extending between said canister and said fuel tank, a purging passage extending between said canister and said intake system of said engine, an open-to-atmosphere passage for communicating an interior of said canister with the atmosphere, a purge control valve arranged in said purging passage, for opening and closing said purging passage, said purge control valve having a valve opening amount thereof being controllable, an open-to-atmosphere valve arranged in said open-to-atmosphere passage, for selectively opening and closing said open-to-atmosphere passage, and pressure detecting means arranged in said evaporative emission control means, for detecting pressure within said evaporative emission control means,

• the improvement comprising:
• negative pressure-introducing means for introducing negative pressure from said intake system of said engine into said evaporative emission control means and said fuel tank by opening said purge control valve and closing said open-to-atmosphere valve;
• and
• purge control means operable when said negative pressure-introducing means is operating, for comparing a value of said pressure within said evaporative emission control means detected by said pressure detecting means with a predetermined negative pressure value, and for controlling said valve opening amount of said purge control valve, based on results of said comparison,
• wherein said purge control means compares said value of said pressure within said evaporative emission control means detected by said pressure detecting mean with a first predetermined negative pressure value and a second predetermined negative pressure value which is lower than said first predetermined negative pressure value, said purge control means progressively increasing said valve opening amount of said purge control valve when said value of said pressure within said evaporative emission control means detected by said pressure detecting means reaches said first predetermined negative pressure value, and progressively decreasing said valve opening amount of said purge control valve when said value of said pressure within said evaporative emission control means detected by said pressure detecting means reaches said second predetermined negative pressure value.

In an evaporative fuel-processing system for an internal combustion engine having an intake system, and a fuel tank, including evaporative emission control means having a canister for adsorbing evaporative fuel generated within said fuel tank, a charging passage extending between said canister and said fuel tank, a purging passage extending between said canister and said intake system of said engine, an open-to-atmosphere passage for communicating an interior of said canister with the atmosphere, a purge control valve arranged in said purging passage, for opening and closing said purging passage, said purge control valve having a valve opening amount thereof being controllable, an open-to-atmosphere valve arranged in said open-to-atmosphere passage, for selectively opening and closing said open-to-atmosphere passage, and pressure detecting means arranged in said evaporative emission control means, for detecting pressure within said evaporative emission control means,

• the improvement comprising:
• negative pressure-introducing means for introducing negative pressure from said intake system of said engine into said evaporative emission control means and said fuel tank by opening said purge control valve and closing said open-to-atmosphere valve;
• purge control means operable when said negative pressure-introducing means is operating, for comparing a value of said pressure within said evaporative emission control means detected by said pressure detecting means with a predetermined negative pressure value, and for controlling said valve opening amount of said purge control valve, based on results of said comparison;
• and
• open-loop purge control means operable when said negative pressure-introducing means is operating, for controlling said valve opening amount of said purge control valve, irrespective of said value of said pressure within said evaporative emission control means detected by said pressure detecting means,
• wherein said open-loop purge control means executes said control of said valve opening amount of said purge control valve, before said purge control means operates to control said valve opening amount, and
• wherein said open-loop purge control means terminates said control of said valve opening amount of said purge control valve when said pressure within said evaporative emission control means reaches a second predetermined negative pressure value.

In an evaporative fuel-processing system for an internal combustion engine having an intake system, and a fuel tank, including evaporative emission control means having a canister for adsorbing evaporative fuel generated within said fuel tank, a charging passage extending between said canister and said fuel tank, a purging passage extending between said canister and said intake system of said engine, an open-to-atmosphere passage for communicating an interior of said canister with the atmosphere, a purge control valve arranged in said purging passage, for opening and closing said purging passage, said purge control valve having a valve opening amount thereof being controllable, an open-to-atmosphere valve arranged in said open-to-atmosphere passage, for selectively opening and closing said open-to-atmosphere passage, and pressure detecting means arranged in said evaporative emission control means, for detecting pressure within said evaporative emission control means,

• the improvement comprising:
• negative pressure-introducing means for introducing negative pressure from said intake system of said engine into said evaporative emission control means and said fuel tank by opening said purge control valve and closing said open-to-atmosphere valve;
• purge control means operable when said negative pressure-introducing means is operating, for comparing a value of said pressure within said evaporative emission control means detected by said pressure detecting means with a predetermined negative pressure value, and for controlling said valve opening amount of said purge control valve, based on results of said comparison;
• and
• open-loop purge control means operable when said negative pressure-introducing means is operating, for controlling said valve opening amount of said purge control valve, irrespective of said value of said pressure within said evaporative emission control means detected by said pressure detecting means,
• wherein said open-loop purge control means executes said control of said valve opening amount of said purge control valve, before said purge control means operates to control said valve opening amount, and
• wherein said negative pressure-introducing means terminates said introduction of said negative pressure into said evaporative emission control means and said fuel tank if said pressure within said evaporative emission control means does not yet reach said second predetermined negative pressure value when a predetermined period to time elapses after the start of said introduction of said negative pressure into said evaporative emission control means and said fuel tank.