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Exhaust system for internal combustion engine

  • US 5,228,287 A
  • Filed: 06/29/1992
  • Issued: 07/20/1993
  • Est. Priority Date: 06/28/1991
  • Status: Expired due to Term
First Claim
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1. An exhaust system for an internal combustion engine having a plurality of cylinders divided into two groups, which are independently connected to exhaust lines comprising an individual exhaust passage and a common exhaust passage, said exhaust system comprising:

  • air-fuel ratio detecting means, disposed in each individual exhaust passage, for detecting an air-fuel ratio based on an emission level of exhaust gas;

    catalytic convertor means, disposed in said common exhaust passage, for purifying exhaust gas;

    an oxygen sensor, disposed in said common exhaust passage downstream from said catalytic convertor means, for detecting an oxygen level of exhaust gas passed through said catalytic convertor means; and

    control means for feedback controlling air-fuel ratios for said cylinder groups independently based on emission levels detected by said air-fuel ratio detecting means, respectively, for detecting vehicle driving conditions, for feedback controlling an air-fuel ratio for said cylinder groups all together based on either one of the air-fuel ratios only when detecting a specific vehicle driving condition, and for detecting deterioration of said catalytic convertor means based on a signal representative of an oxygen level detected by said oxygen sensor while an air-fuel ratio is feedback controlled for said cylinder groups all together based on said one of said air-fuel ratios, thereby determining a critical deterioration of said catalytic convertor means.

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