US 5,347,974 AGranted

Air-to-fuel ratio control system for internal combustion engine

AssigneeMitsubishi Jidosha Kogyo Kabushi Kaisha

InventorsKazuhide Togai, Tetsurou Ishida, Katsunori Ueda

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Abstract

An air-to-fuel ratio control system optimally controls an air-to-fuel ratio of an internal combustion engine according to various engine operating conditions, and aims at assuring quick air-to-fuel ratio control and preventing erroneous operation of the engine. With this control system, a corrective amount of fuel to be supplied is determined according to a deviation .DELTA.(A/F) of a measured air-to-fuel ratio (A/F).sub.i and a target air-to-fuel ration (A/F).sub.OBJ. This corrective amount of the fuel is kept in an allowable range defined by limits K.sub.LMIN and K.sub.LMAX, or K.sub.RMIN and K.sub.RMAX. Therefore, the engine is supplied with the fuel which is controlled according to a target fuel amount LT.sub.INJ determined by the correct fuel amount. The control system is responsive to various engine operating conditions, and protects the engine against troubles, damage and interruption, and prevents deterioration of exhaust gases.

Claims22

Dependent claims

An air-to-fuel ratio control system for an internal combustion engine, comprising:

a wide-range air-to-fuel ratio sensor located in an exhaust passage of the internal combustion engine for measuring an air-to-fuel ratio;
target air-to-fuel ratio calculating means for calculating a target air-to-fuel ratio which is determined according to operating conditions of the internal combustion engine;
air-to-fuel ratio deviation calculating means, operatively communicative with said wide-range air-to-fuel ratio sensor and said target air-to-fuel ratio calculating means, for calculating a deviation between the measured air-to-fuel ratio by said wide-range air-to-fuel ratio sensor and said target air-to-fuel ratio for setting a deviation signal;
corrective fuel amount setting means, operatively communicative with said air-to-fuel ratio deviation calculating means for changing the amount of fuel to be supplied from said deviation signal calculated by said air-to-fuel ratio deviation calculating means;
corrective amount limit setting means for setting at least one maximum corrective limit value according to said target air-to-fuel ratio;
and
corrective amount optimizing means, operatively communicative with said corrective amount limit setting means and said corrective fuel amount setting means, for determining an optimum amount of fuel to be supplied within said corrective limit value based on the amount of fuel set by said corrective fuel amount setting means.

4 more elements

An air-to-fuel ratio control system for an internal combustion engine, comprising:

target air-to-fuel ratio calculating means for calculating a target air-to-fuel ratio according to operating conditions of the internal combustion engine;
a wide-range air-to-fuel ratio sensor located in an exhaust passage for measuring an actual air-to-fuel ratio;
deviation calculating means, operatively communicative with said wide-range air-to-fuel ratio sensor and said target air-to-fuel ratio calculating means, for calculating a deviation between said actual air-to-fuel ratio measured by said wide-range air-to-fuel ratio sensor and said target air-to-fuel ratio calculated by said target air-to-fuel ratio calculating means;
corrective fuel amount setting means, operatively communicative with said deviation calculating means, for changing the amount of fuel to be supplied based on said deviation of the air-to-fuel ratio calculated by said deviation calculating means;
corrective amount limit setting means for setting at least one corrective value according to the target air-to-fuel ratio;
corrective amount optimizing means, operatively communicative with said corrective amount limit setting means and said corrective fuel amount setting means, for determining an optimum amount of the fuel to be supplied within said corrective limit value based on the amount of fuel set by said corrective fuel amount setting means;
corrective ratio setting means, operatively communicative with said target air-to-fuel ratio calculating means and said corrective amount optimizing means, for determining a corrective air-to-fuel ratio based on said target air-to-fuel ratio and said optimum amount of the fuel to be supplied;
and
reference fuel amount setting means, operatively communicative with said corrective ratio setting means, for determining a reference amount of the fuel based on said corrective air-to-fuel ratio.

6 more elements

Dependencies are inferred from the claim text.