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Air-fuel ratio control apparatus for multicylinder internal combustion engine

  • US 6,327,850 B1
  • Filed: 10/06/2000
  • Issued: 12/11/2001
  • Est. Priority Date: 10/08/1999
  • Status: Expired due to Term
First Claim
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1. An apparatus for controlling the air-fuel ratio of a multicylinder internal combustion engine having all cylinders divided into a plurality of cylinder groups and an exhaust system including a plurality of auxiliary exhaust passages for discharging exhaust gases produced when an air-fuel mixture of air and fuel is combusted from said cylinder groups, respectively, a main exhaust passage joining said auxiliary exhaust passages together at downstream sides thereof, an exhaust gas sensor mounted in said main exhaust passage for detecting the concentration of a given component in the exhaust gases flowing through said main exhaust passage, and a catalytic converter connected to at least one of said auxiliary exhaust passages and said main exhaust passage upstream of said exhaust gas sensor, said apparatus comprising:

  • target air-fuel ratio data generating means for sequentially generating target air-fuel ratio data representing the air-fuel ratio of the air-fuel mixture combusted in each of said cylinder groups so as to converge an output from said exhaust gas sensor to a predetermined target value;

    air-fuel ratio manipulating means for manipulating the air-fuel ratio of the air-fuel mixture combusted in each of said cylinder groups depending on said target air-fuel ratio data;

    said exhaust system including a system which comprises an object exhaust system disposed upstream of said exhaust gas sensor and including said auxiliary exhaust passages and said catalytic converter, said air-fuel ratio manipulating means, and said multicylinder internal combustion engine, said system being equivalent to a system for generating an output of said exhaust gas sensor from a target combined air-fuel ratio determined by combining the values of target air-fuel ratios for all the cylinder groups, respectively, according to a filtering process of the mixed model type; and

    target combined air-fuel ratio data generating means for sequentially generating target combined air-fuel ratio data representing said target combined air-fuel ratio which is required to converge the output from said exhaust gas sensor to said predetermined target value with the equivalent system serving as an object system to be controlled;

    said target air-fuel ratio data generating means comprising means for sequentially generating said target air-fuel ratio data from the target combined air-fuel ratio data generated by said target combined air-fuel ratio data generating means according to a predetermined converting process determined based on characteristics of said filtering process of the mixed model type, said target air-fuel ratio of the air-fuel mixture combusted in each of said cylinder groups being shared by said cylinder groups.

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