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

• Current Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Original Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Inventors: Kaneko, Tetsuya, Ito, Hiroshi, Iwata, Yoichi, Teshirogi, Tetsu, Hatcho, Seiji
• Primary Examiner(s): KWON, JOHN
• Application Number:
  US08/562,367
• Time in Patent Office: 629 Days
• Field of Search: 60/276, 60/277
• 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 2550/02 Catalytic activity of catalytic converters
• CPC Class Codes: F02D 2200/0816 Oxygen storage capacity
• CPC Class Codes: F02D 41/0047 Controlling exhaust gas recirculation [EGR] temperature control with cooler in recirculation circuit F02M26/33
• CPC Class Codes: F02D 41/0235 in relation with the state of the exhaust gas treating apparatus control of exhaust gas treating apparatus per se F01N
• CPC Class Codes: F02D 41/1441 Plural sensors
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

An air-fuel ratio control system for an internal combustion engine having a catalyst arranged in the exhaust system, for purifying exhaust gases emitted from the engine. Upstream and downstream air-fuel ratio sensors arranged in the exhaust system at respective locations upstream and downstream of the catalyst detect the concentration of a specific component present in the exhaust gases. An ECU controls the air-fuel ratio of an air-fuel mixture supplied to the engine, in response to the outputs from the upstream and downstream air-fuel ratio sensors. The ECU detects deterioration of the catalyst caused by sulfur poisoning, based on at least the output from the downstream air-fuel ratio sensor.

Claims

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.

2. An air-fuel ratio control system as claimed in claim 1, wherein said sulfur poisoning-detecting means determines that said catalyst is sulfur-poisoned when a rich-side maximum value of said output from said downstream air-fuel ratio-detecting means is below a predetermined value.

3. An air-fuel ratio control system as claimed in claim 1, wherein said sulfur poisoning-detecting means determines that said catalyst is sulfur-poisoned when an area obtained by values of Said output from said downstream air-fuel ratio-detecting means which show richer values of said air-fuel ratio of said air-fuel mixture than a predetermined air-fuel ratio is below a predetermined value.

4. An air-fuel ratio control system as claimed in claim 1, wherein said sulfur poisoning-detecting means determines that said catalyst is sulfur-poisoned when a rate of change in said output from said downstream air-fuel ratio-detecting means from a richer value to a leaner value with respect to a predetermined air-fuel ratio exceeds a predetermined value.

5. An air-fuel ratio control system as claimed in claim 1, wherein said sulfur poisoning-detecting means determines that said catalyst is sulfur-poisoned when amplitude of said output from said downstream air-fuel ratio-detecting means is below a predetermined value.

6. An air-fuel ratio control system as claimed in claim 1, wherein said sulfur poisoning-detecting means determines that said catalyst is sulfur-poisoned when a difference between a rich-side maximum value of said output from said upstream air-fuel ratio-detecting means and a rich-side maximum value of said output from said downstream air-fuel ratio-detecting means exceeds a predetermined value.

7. An air-fuel ratio control system as claimed in claim 1, wherein said sulfur poisoning-detecting means determines that said catalyst is sulfur-poisoned when a difference between amplitude of said output from said upstream air-fuel ratio-detecting means and amplitude of said output from said downstream air-fuel ratio-detecting means exceeds a predetermined value.