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Air-fuel ratio control system for internal combustion engines

  • US 5,655,363 A
  • Filed: 11/22/1995
  • Issued: 08/12/1997
  • Est. Priority Date: 11/25/1994
  • Status: Expired due to Term
First Claim
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1. An air-fuel ratio control system for an internal combustion engine having an exhaust system, and a catalyst arranged in said exhaust system, for purifying exhaust gases emitted from said engine, comprising:

  • upstream air-fuel ratio-detecting means arranged in said exhaust system at a location upstream of said catalyst, for detecting concentration of a specific component present in said exhaust gases;

    downstream air-fuel ratio-detecting means arranged in said exhaust system at a location downstream of said catalyst, for detecting concentration of said specific component present in said exhaust gases;

    air-fuel ratio control means for controlling an air-fuel ratio of an air-fuel mixture supplied to said engine, in response to outputs from said upstream and downstream air-fuel ratio-detecting means; and

    sulfur poisoning-detecting means for detecting deterioration of said catalyst caused by sulfur poisoning, based on at least said output from said downstream air-fuel ratio-detecting means.

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