Fuel evaporative emission suppressing apparatus

A fuel evaporative emission suppressing apparatus for an internal combustion engine whose operation is controlled by fuel supply control means which uses an air-fuel ratio correction coefficient to set a quantity of fuel to be supplied from fuel supply means to the internal combustion engine during air-fuel ratio feedback control in which an air-fuel ratio of a mixture supplied to the internal combustion engine is controlled to a target air-fuel ratio, the apparatus having adsorbing means for adsorbing evaporative fuel gas introduced from a fuel supply system and purge adjusting means for controlling a quantity of introduction of purge air, which contains outside air and evaporative fuel gas separated from the adsorbing means, into an intake passage of the internal combustion engine, comprising:

• operating state detecting means for detecting an operating state of the internal combustion engine;
• target air-fuel ratio correction coefficient setting means for setting a target air-fuel ratio correction coefficient for purge air introduction period;
• purge correction variable setting means for comparing the target air-fuel ratio correction coefficient with an air-fuel ratio correction coefficient which is set by the fuel supply control means during introduction of purge air, and for setting a purge correction variable in accordance with a comparison result;
• purge correction variable modifying means for modifying the purge correction variable in accordance with a change in the engine operating state in such a manner that fluctuation of the air-fuel ratio is suppressed;
• basic purge control variable setting means for setting a basic purge control variable in accordance with the engine operating state detected by said operating state detecting means;
• and
• purge control means for obtaining a purge control variable based on the purge correction variable modified by said purge correction variable modifying means and the basic purge control variable, and for controlling operation of the purge adjusting means in accordance with the purge control variable.

A fuel evaporative emission suppressing apparatus for an internal combustion engine whose operation is controlled by fuel supply control means which uses an air-fuel ratio correction coefficient to set a quantity of fuel to be supplied from fuel supply means to the internal combustion engine during air-fuel ratio feedback control in which an air-fuel ratio of a mixture supplied to the internal combustion engine is controlled to a target air-fuel ratio, the apparatus having adsorbing means for adsorbing evaporative fuel gas introduced from a fuel supply system and purge adjusting means for controlling a quantity of introduction of purge air, which contains outside air and evaporative fuel gas separated from the adsorbing means, into an intake passage of the internal combustion engine, comprising:

• operating state detecting means for detecting an operating state of the internal combustion engine;
• target air-fuel ratio correction coefficient setting means for setting a target air-fuel ratio correction coefficient for purge air introduction period;
• purge correction coefficient setting means for comparing the target air-fuel ratio correction coefficient with an air-fuel ratio correction coefficient which is set by the fuel supply control means during introduction of purge air, and for setting a purge correction coefficient in accordance with a comparison result;
• basic purge control variable setting means for setting a basic purge control variable in accordance with the engine operating state detected by said operating state detecting means;
• and
• purge control means for obtaining a purge control variable by multiplying the basic purge control variable by the purge correction coefficient, and for controlling operation of the purge adjusting means in accordance with the purge control variable.

A fuel evaporative emission suppressing apparatus for an internal combustion engine whose operation is controlled by fuel supply control means which uses an air-fuel ratio correction coefficient to set a quantity of fuel to be supplied from fuel supply means to the internal combustion engine during air-fuel ratio feedback control in which an air-fuel ratio of a mixture supplied to the internal combustion engine is controlled to a target air-fuel ratio, the apparatus having adsorbing means for adsorbing evaporative fuel gas introduced from a fuel supply system and purge adjusting means for controlling a quantity of introduction of purge air, which contains outside air and evaporative fuel gas separated from the adsorbing means, into an intake passage of the internal combustion engine, comprising:

• operating state detecting means for detecting an operating state of the internal combustion engine;
• target air-fuel ratio correction coefficient setting means for setting a target air-fuel ratio correction coefficient for purge air introduction period;
• purge correction coefficient setting means for comparing the target air-fuel ratio correction coefficient with an air-fuel ratio correction coefficient which is set by the fuel supply control means during introduction of purge air, and for setting a purge correction coefficient in accordance with a comparison result;
• basic purge control variable setting means for setting a basic purge control variable in accordance with the engine operating state detected by said operating state detecting means;
• and
• purge control means for obtaining a purge control variable based on a purge correction variable, which is obtained by multiplying the basic purge control variable by the purge correction coefficient, and the basic purge control variable, and for controlling operation of the purge adjusting means in accordance with the purge control variable.

A fuel evaporative emission suppressing method for an internal combustion engine, comprising:

• detecting an operating condition of said internal combustion engine;
• setting an air-fuel ratio correction coefficient to determine an amount of fuel supplied to said internal combustion engine during an air-fuel ratio feedback control in which an air-fuel ratio of a mixture supplied to said internal combustion engine is controlled to a target air-fuel ratio;
• setting a target air-fuel ratio correction coefficient for purge air introduction period;
• comparing said air-fuel ratio correction coefficient and said target air-fuel ratio correction coefficient to determine a purge correction coefficient based on the compared result;
• determining a purge control variable based at least on said determined purge correction coefficient;
• and
• controlling a purge adjusting unit based on said determined purge control variable.