System for determining deterioration of catalysts of internal combustion engines

• US 5,325,664 A
• Filed: 10/16/1992
• Issued: 07/05/1994
• Est. Priority Date: 10/18/1991
• 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: Kumagai, Katuhiro, Kobayashi, Makoto, Maruyama, Hiroshi, Sato, Toshihiko, Maeda, Kenichi, Iwata, Yoichi, Aoki, Takuya, Takizawa, Tsuyoshi, Terata, Shukoh, Kuroda, Shigetaka, Sawamura, Kazutomo, Chikamatsu, Masataka, Seki, Yasunari, Uto, Hajime
• Primary Examiner(s): Kamen, Noah P.
• Application Number:
  US07/961,794
• Time in Patent Office: 627 Days
• Field of Search: 60/277, 60/285, 60/276
• US Class Current: 60/276
• CPC Class Codes: F01N 11/002 the diagnostic devices measuring or estimating temperature or pressure in, or downstream of the exhaust apparatus
• CPC Class Codes: F01N 11/007 the diagnostic devices measuring oxygen or air concentration downstream of the exhaust apparatus
• CPC Class Codes: F01N 13/009 having two or more separate purifying devices arranged in series
• CPC Class Codes: F01N 2550/02 Catalytic activity of catalytic converters
• CPC Class Codes: F01N 2900/0422 measuring the elapsed time
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A catalyst deterioration-determining system determines deterioration of a catalyst arranged in the exhaust passage of an internal combustion engine. An ECU is responsive to an output from an O₂ sensor arranged upstream of the catalyst or outputs from O₂ sensors arranged upstream and downstream of the catalyst for controlling the air-fuel ratio of a mixture supplied to the engine by means of an air-fuel ratio correction value (first air-fuel ratio control). When the engine is in a predetermined operating condition, the system effects changeover from the first air-fuel ratio control to a second air-fuel ratio control which is responsive to the output from the downstream O₂ sensor for controlling the air-fuel ratio of the mixture by means of the air-fuel ratio correction value. After the changeover has been effected, a time period is measured which elapses from the time the second air-fuel ratio control causes a change in the air-fuel ratio correction value from a richer side to a leaner side or vice versa with respect to a stoichiometric air-fuel ratio to the time the output from the downstream O₂ sensor is inverted from the richer side to the leaner side or vice versa with respect to the stoichiometric air-fuel ratio. It is determined that the catalyst is deteriorated, when the measured time period is shorter than the predetermined time period.

Claims

1. A catalyst deterioration-determining system for determining deterioration of catalyst means of an internal combustion engine having:

an exhaust passage;

catalyst means arranged in said exhaust passage;

an oxygen concentration sensor arranged in said exhaust passage downstream of said catalyst means for sensing concentration of oxygen contained in said exhaust gases;

determining means for comparing an output from said oxygen concentration sensor with a predetermined reference value and determining, from a result of said comparison, whether the air-fuel ratio of a mixture supplied to said engine is richer or leaner than a stoichiometric air-fuel ratio;

air-fuel ratio control means responsive solely to an output from said determining means for calculating an air-fuel ratio correction value and controlling the air-fuel ratio of said mixture by means of the calculated air-fuel ratio correction value; and

operating condition detecting means for detecting operating conditions of said engine,

said catalyst deterioration-determining system comprising;

inversion time period measuring means for measuring a time period elapsed from the time said air-fuel ratio control means causes an inversion in the value of said air-fuel ratio of said mixture with respect to said stoichiometric air-fuel ratio in response to said output from said determining means to the time an inversion occurs in said output from said determining means, when it is detected by said operating condition detecting means that said engine is in a predetermined operating condition; and

deterioration determining means for comparing said time period measured by said inversion time period measuring means with a predetermined time period and determining that said catalyst means is deteriorated, when said measured time period is shorter than said predetermined time period.

2. A catalyst deterioration-determining system as claimed in claim 1, wherein said operating condition detecting means includes catalyst temperature detecting means for detecting temperature of said catalyst means.

3. A catalyst deterioration-determining system as claimed in claim 2, including determination inhibiting means for inhibiting said determination of deterioration of said catalyst means, when the detected temperature of said catalyst means falls outside a predetermined range.

4. A catalyst deterioration-determining system as claimed in claim 2, wherein said catalyst temperature detecting means is mounted in said catalyst means for detecting temperature at a central portion of said catalyst means.

5. A catalyst deterioration-determining system as claimed in claim 1, wherein said operating condition detecting means includes catalyst temperature estimating means for estimating temperature of said catalyst means, based upon operating parmeters of said engine.

6. A catalyst deterioration-determining system as claimed in claim 5, wherein said catalyst temperature estimating means estimates the temperature of said catalyst means, based upon rotational speed of said engine and load on said engine.

7. A catalyst deterioration-determining system as claimed in claim 5, wherein said catalyst temperature estimating means estimates the temperature of said catalyst means, based upon an amount of intake air supplied to said engine.

8. A catalyst deterioration-determining system as claimed in claim 5, including determination inhibiting means for inhibiting said determination of deterioration of said catalyst means, when the estimated temperature of said catalyst means falls outside a predetermined range.

9. A catalyst deterioration-determining system as claimed in claim 1, wherein said inversion time period measuring means comprises:

first time period measuring means for measuring a first time period elapsed from the time said air-fuel ratio control means causes a change in the value of said air-fuel ratio correction value from a richer side to a leaner side with respect to said stoichiometric air-fuel ratio to the time said output from said oxygen concentration sensor is inverted from said richer side to said leaner side with respect to said stoichiometric air-fuel ratio;

second time period measuring means for measuring a second time period elapsed from the time said air-fuel ratio control means causes a change in the value of said air-fuel ratio correction value from said leaner side to said richer side with respect to said stoichiometric air-fuel ratio to the time said output from said second oxygen concentration sensor is inverted from said leaner side to said richer side with respect to said stoichiometric air-fuel ratio;

said deterioration determining means comparing the sum of first and second time periods measured by said first and second time period measuring means or an average value thereof with a predetermined time period and determining that said catalyst means is deteriorated, when the sum or said average value is less than said predetermined time period;

wherein said deterioration determining means calculates the sum or said average value of said first time period measured by said first time period measuring means and said second time period successively measured following said measurement of said first time period, by said second time period measuring means, and determines that said catalyst means is deteriorated when the calculated sum or average value is less than said predetermined time period.

10. A catalyst deterioration-determining system for determining deterioration of catalyst means of an internal combustion engine having:

an exhaust passage;

catalyst means arranged in said exhaust passage;

a first oxygen concentration sensor arranged in said exhaust passage upstream of said catalyst means, for sensing concentration of oxygen contained in exhaust gases emitted from said engine;

first determining means for comparing an output from said first oxygen concentration sensor with a first predetermined reference value and determining, from a result of said comparison, whether the air-fuel ratio of a mixture supplied to said engine is richer or leaner than a stoichiometric air-fuel ratio;

a second oxygen concentration sensor arranged in said exhaust passage downstream of said catalyst means for sensing concentration of oxygen contained in said exhaust gases;

second determining means for comparing an output from said second oxygen concentration sensor with a second predetermined reference value and determining, from a result of said comparison, whether the air-fuel ratio of said mixture supplied to said engine is richer or leaner than said stoichiometric air-fuel ratio;

air-fuel ratio control means responsive to an output from said second determining means for calculating an air-fuel ratio correction value and controlling the air-fuel ratio of said mixture by means of the calculated air-fuel ratio correction value; and

operating condition detecting means for detecting operating conditions of said engine,

said catalyst deterioration-determining system comprising;

inversion time period measuring means for calculating a time period based upon the time an inversion occurs in an output from said first determining means to the time an inversion occurs in said output from said second determining means, after said air-fuel ratio control means causes an inversion in the value of the air-fuel ratio of said mixture with respect to said stoichiometric air-fuel ratio in response to said output from said second determining means, when it is detected by said operating condition detecting means that said engine is in a predetermined operating condition; and

deterioration determining means for comparing said time period calculated by said inversion time period measuring means with a predetermined time period and determining that said catalyst means is deteriorated, when said calculated time period is shorter than said predetermined time period.

11. A catalyst deterioration-determining system as claimed in claim 10, wherein said inversion time period measuring means comprises:

first time difference measuring means for measuring a first time difference between the time said output from said first oxygen concentration sensor is inverted from a richer side to a leaner side with respect to said stoichiometric air-fuel ratio after said air-fuel ratio control means causes a change in the value of said air-fuel ratio correction value from said richer side to said leaner side with respect to said stoichiometric air-fuel ratio and the time said output from said second oxygen concentration sensor is subsequently inverted from said richer side to said leaner side with respect to said stoichiometric air-fuel ratio;

second time difference measuring means for measuring a second time difference between the time said output from said first oxygen concentration sensor is inverted from said leaner side to said richer side with respect to said stoichiometric air-fuel ratio after said air-fuel ratio control means causes a change in the value of said air-fuel ratio correction value from said leaner side to said richer side with respect to said stoichiometric air-fuel ratio and the time said output from said second oxygen concentration sensor is subsequently inverted from said leaner side to said richer side with respect to said stoichiometric air-fuel ratio; and

said deterioration determining means comparing the sum of first and second time differences measured by said first and second time difference measuring means or an average value thereof with a predetermined time period and determining that said catalyst means is deteriorated, when the sum or said average value is less than said predetermined time period;

wherein said deterioration determining means calculates the sum or said average value of said first time difference measured by said first time difference measuring means and said second time difference successively measured following said measurement of said first time period, by said second time difference measuring means, and determines that said catalyst means is deteriorated when the calculated sum or average value is less than said predetermined time period.

12. A catalyst deterioration-determining system for determining deterioration of catalyst means of an internal combustion engine having:

an exhaust passage;

catalyst means arranged in said exhaust passage;

a first oxygen concentration sensor arranged in said exhaust passage upstream of said catalyst means, for sensing concentration of oxygen contained in exhaust gases emitted from said engine;

a second oxygen concentration sensor arranged in said exhaust passage downstream of said catalyst means for sensing concentration of oxygen contained in said exhaust gases; and

first air-fuel ratio control means responsive to an output from said first oxygen concentration sensor and an output from said second oxygen concentration sensor for controlling the air-fuel ratio of a mixture supplied to said engine by means of an air-fuel ratio correction value;

said catalyst deterioration-determining system comprising;

second air-fuel ratio control means responsive to said output from said second oxygen concentration sensor for controlling the air-fuel ratio of said mixture by means of said air-fuel ratio correction value;

operating condition determining means for determining whether said engine is in a predetermined operating condition;

changeover means for effecting changeover from said first air-fuel ratio control means to said second air-fuel ratio control means for controlling the air-fuel ratio of said mixture, when said engine is determined to be in said predetermined operating condition;

inversion determining means for determining whether said output from said second oxygen concentration sensor has been inverted from a leaner side to a richer side or vice versa with respect to a stoichiometric air-fuel ratio;

first time period measuring means for measuring a first time period elapsed from the time said second air-fuel ratio control means causes a change in the value of said air-fuel ratio correction value from said richer side to said leaner side with respect to said stoichiometric air-fuel ratio to the time said output from said second oxygen concentration sensor is inverted from said richer side to said leaner side with respect to said stoichiometric air-fuel ratio, after said changeover has been effected;

second time period measuring means for measuring a second time period elapsed from the time said second air-fuel ratio control means causes a change in the value of said air-fuel ratio correction value from said leaner side to said richer side with respect to said stoichiometric air-fuel ratio to the time said output from said second oxygen concentration sensor is inverted from said leaner side to said richer side with respect to said stoichiometric air-fuel ratio, after said changeover has been effected;

deterioration determining means for comparing the sum of said first and second time periods measured by said first and second time period measuring means or an average value thereof with a predetermined time period and determining that said catalyst means is deteriorated, when the sum or said average value is shorter than said predetermined time period.

13. A catalyst deterioration-determining system as claimed in claim 12, wherein said deterioration-determining means calculates the sum or said average value of said first time period measured while said second air-fuel ratio control means is controlling the air-fuel ratio of said mixture in response to said output from said second oxygen concentration sensor and said second time period successively measured following said measurement of said first time period, and determines that said catalyst means is deteriorated when the calculated sum or average value is less than said predetermined time period.

14. A catalyst deterioration-determining system for determining deterioration of catalyst of an internal combustion engine having:

an exhaust passage;

catalyst means arranged in said exhaust passage;

a first oxygen concentration sensor arranged in said exhaust passage upstream of said catalyst means, for sensing concentration of oxygen contained in exhaust gases emitted from said engine;

a second oxygen concentration sensor arranged in said exhaust passage downstream of said catalyst means, for sensing concentration of oxygen contained in said exhaust gases; and

first air-fuel ratio control means responsive to an output from said first oxygen concentration sensor and an output from said second oxygen concentration sensor, for controlling the air-fuel ratio of a mixture supplied to said engine by means of a first air-fuel ratio correction value;

said catalyst deterioration determining system comprising;

second air-fuel ratio control means responsive to said output from said second oxygen concentration sensor, for controlling the air-fuel ratio of said mixture by means of a second air-fuel ratio correction value;

operating condition determining means for determining whether said engine is in a predetermined operating condition;

changeover means for effecting changeover from said first air-fuel ratio control means to said second air-fuel ratio controlling means for controlling the air-fuel ratio of said mixture, when said engine is determined to be in said predetermined operating condition;

deterioration determining means for determining whether said catalyst means is deteriorated, based on said output from said second oxygen concentration sensor which is output when the air-fuel ratio of said mixture is controlled by said second air-fuel ratio control means.