Air-fuel ratio control system for internal combustion engines, having catalytic converter deterioration-detecting function

• US 5,386,695 A
• Filed: 01/21/1994
• Issued: 02/07/1995
• Est. Priority Date: 01/21/1993
• Status: Expired due to Term

• Current Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Original Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Inventors: Sato, Toshihiko, Iwata, Yoichi, Takizawa, Tsuyoshi, Seki, Yasunari, Nakayama, Takayoshi
• Primary Examiner(s): Lazarus, Ira S.
• Assistant Examiner(s): O'CONNOR, DANIEL
• Application Number:
  US08/183,750
• Time in Patent Office: 382 Days
• Field of Search: 60/274, 60/276, 60/277, 60/285, 123/672, 123/674, 123/703
• US Class Current: 60/276
• CPC Class Codes: F01N 11/007 the diagnostic devices measuring oxygen or air concentration downstream of the exhaust apparatus
• CPC Class Codes: F01N 2900/0422 measuring the elapsed time
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

An air-fuel ratio control system for an internal combustion engine having a catalytic converter arranged in the exhaust system, and first and second air-fuel ratio sensors arranged upstream and downstream of the catalytic converter respectively has an ECU which calculates an air-fuel ratio correction amount, based at least on an output from the first air-fuel ratio sensor, and detects deterioration of the catalytic converter, based on an output from the second air-fuel ratio sensor when the engine is in a predetermined operating condition. The ECU inhibits detection of deterioration of the catalytic converter when the air-fuel ratio correction amount falls outside a predetermined range.

Claims

1. An air-fuel ratio control system for an internal combustion engine having an exhaust system, and catalytic converter means arranged in said exhaust system, comprising:

first and second air-fuel ratio sensor means arranged in said exhaust system upstream and downstream of said catalytic converter means, respectively;

air-fuel ratio correction amount-calculating means for calculating an air-fuel ratio correction amount, based at least on an output from said first air-fuel ratio sensor means,

catalytic converter deterioration-detecting means for detecting deterioration of said catalytic converter means, based on an output from said second air-fuel ratio sensor means when the engine is in a predetermined operating condition; and

deterioration detection-inhibiting means for inhibiting operation of said catalytic converter deterioration-detecting means when said air-fuel ratio correction amount falls outside a predetermined range.

2. An air-fuel ratio control system as claimed in claim 1, including deterioration detection-permitting means for permitting the operation of said catalyst deterioration-detecting means after a predetermined time period elapses from a time said air-fuel ratio correction amount returns into said predetermined range.

3. An air-fuel ratio control system as claimed in claim 1, including limiting means for limiting said air-fuel ratio correction amount within a first predetermined range when said air-fuel ratio correction amount falls outside said first predetermined range, and wherein said deterioration detection-inhibiting means inhibits the operation of said catalytic converter deterioration-detecting means when said air-fuel ratio correction amount falls outside a second predetermined range included within said first predetermined range.

4. An air-fuel ratio control system as claimed in claim 1, including correcting means for correcting said air-fuel ratio correction amount, based on said output from said second air-fuel ratio sensor means.

5. An air-fuel ratio control system as claimed in claim 1, including inversion period-measuring means for measuring an inversion period with which said output from said second air-fuel ratio sensor means is inverted, and wherein said catalytic converter deterioration-detecting means detects deterioration of said catalytic converter means, based on the measured inversion period.

6. An air-fuel ratio control system for an internal combustion engine having an exhaust system, and catalytic converter means arranged in said exhaust system, comprising:

air-fuel ratio sensor means arranged in said exhaust system downstream of said catalytic converter means;

air-fuel ratio correction amount-calculating means for calculating an air-fuel ratio correction amount, based at least on an output from said air-fuel ratio sensor means;

catalytic converter deterioration-detecting means for detecting deterioration of said catalytic converter means, based on said output from said air-fuel ratio sensor means when the engine is in a predetermined operating condition; and

deterioration detection-inhibiting means for inhibiting operation of said catalytic converter deterioration-detecting means when said air-fuel ratio correction amount falls outside a predetermined range.