Patent Document ID: 4800857
Application ID: 07146085
Patent Flag: 1

Claim One:
1. An apparatus for learn-controlling the air-fuel ratio for an internal combustion engine, comprising: engine running condition detecting means for detecting an engine running condition including at least a parameter concerning the quantity of air which is sucked into the engine; air-fuel ratio detecting means for detecting the air-fuel ratio of the air-fuel mixture which is sucked into the engine by detecting a component of exhaust gas from the engine; basic fuel injection quantity setting means for setting a basic fuel injection quantity on the basis of said parameter detected by said engine running condition detecting means; rewritable global learning correction coefficient storing means for storing a global learning correction coefficient employed for globally correcting said basic fuel injection quantity for all the engine running condition areas; rewritable area-wise learning correction coefficient storing means for storing an area-wise learning correction coefficient employed for correcting said basic fuel injection quantity for each of said engine running condition areas; area-wise learning correction coefficient retrieving means for retrieving on the basis of an actual engine running condition an area-wise learning correction coefficient in the corresponding engine running condition area stored in said area-wise learning correction coefficient storing means; feedback correction coefficient setting means for comparing the air-fuel ratio detected by said air-fuel ratio detecting means with a target air-fuel ratio and setting a feedback correction coefficient for correcting said basic fuel injection quantity by increasing or decreasing said feedback correction coefficient by a predetermined amount so that the actual air-fuel ratio is convergent on said target air-fuel ratio; fuel injection quantity calculating means for calculating a fuel injection quantity on the basis of the basic fuel injection quantity set by said basic fuel injection quantity setting means, the global learning correction coefficient stored in said global learning correction coefficient storing means, the area-wise learning correction coefficient retrieved by said area-wise learning correction coefficient retrieving means, and the feedback correction coefficient set by said feedback correction coefficient setting means; fuel injection means for injecting fuel into the engine in an ON/OFF manner in response to a driving pulse signal which is equivalent to the fuel injection quantity calculated by said fuel injection quantity calculating means; area-wise learning correction coefficient correcting means for learning a deviation of said feedback correction coefficient from a reference value for each of the engine running condition areas and correcting as well as rewriting the corresponding area-wise learning correction coefficient stored in said area-wise learning correction coefficient storing means so that said deviation is minimized; area-wise learning progress detecting means for issuing a first global learning command every time the area-wise learning correction coefficients for a predetermined number of different engine running condition areas are corrected by said area-wise learning correction coefficient correcting means; learning direction judging means for judging the direction of deviations of the present area-wise learning correction coefficients from a reference value for a predetermined number of different engine running condition areas when the first global learning command is issued from said area-wise learning progress detecting means, and issuing a second global learning command when all the deviations have the same direction; mean value calculating means for calculating a mean value of deviations of the present area-wise learning correction coefficients from the reference value for the predetermined number of different engine running condition areas when the second global learning command is issued from said learning direction judging means; global learning correction coefficient correcting means for correcting and rewriting the global learning correction coefficient stored in said global learning correction coefficient storing means by adding the mean value calculated by said mean value calculating means to the global learning correction coefficient stored in said global learning correction coefficient storing means; and second area-wise learning correction coefficient correcting means for correcting and rewriting the area-wise learning correction coefficients stored in said area-wise learning correction coefficient storing means and on the basis of which said mean value was calculated by subtracting the mean value calculated by said mean value calculating means from the area-wise learning correction coefficients.