Catalyst deterioration detection device for internal combustion engine

• US 5,737,916 A
• Filed: 10/24/1996
• Issued: 04/14/1998
• Est. Priority Date: 10/26/1995
• Status: Expired due to Term

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Mitsutani, Noritake
• Primary Examiner(s): ARGENBRIGHT, TONY MICHAEL
• Application Number:
  US08/736,548
• Time in Patent Office: 537 Days
• Field of Search: 60/274, 60/276, 60/277, 60/285, 73/118.1
• 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: F01N 2560/025 for measuring or detecting O2, e.g. lambda sensors
• CPC Class Codes: F01N 2560/14 having more than one sensor of one kind
• CPC Class Codes: F01N 2570/16 Oxygen
• CPC Class Codes: F01N 3/0864 Oxygen
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A catalyst deterioration detection device for an internal combustion engine, according to the present invention, includes a three-way catalyst mounted in an exhaust passage of the internal combustion engine and having an O₂ storage capability and an air-fuel ratio sensor, mounted upstream of the three-way catalyst, for linearly detecting an air-fuel ratio. An air-fuel ratio feedback control unit, based on the output of the air-fuel ratio sensor, calculates a feedback correction amount consisting of a proportional term for bringing the air-fuel ratio to stoichiometry and an integral term for bringing an integrated value of an error between the air-fuel ratio and stoichiometry to zero. An O₂ sensor, mounted downstream of the three-way catalyst, detects whether the air-fuel ratio is rich or lean. A catalyst deterioration determining unit determines deterioration of the three-way catalyst on the basis of the length of a response curve that the output of the O₂ sensor describes during the time that air-fuel ratio feedback control is being performed by the air-fuel ratio feedback control unit. A response curve length calculation interrupting unit interrupts the calculation of the response curve length being performed by the catalyst deterioration determining unit for a predetermined length of time when the output of the air-fuel ratio sensor or the amount of change of the output has exceeded a preset value.

Claims

1. A catalyst deterioration detection device for an internal combustion engine, comprising:

a three-way catalyst mounted in an exhaust passage of said internal combustion engine and having an O₂ storage capability;

an air-fuel ratio sensor, mounted upstream of said three-way catalyst, for linearly detecting air-fuel ratio;

air-fuel ratio feedback control means for, based on the output of said air-fuel ratio sensor, calculating a feedback correction amount consisting of a proportional term for bringing the air-fuel ratio to stoichiometry and an integral term for bringing an integrated value of an error between the air-fuel ratio and stoichiometry to zero;

an O₂ sensor, mounted downstream of said three-way catalyst, for detecting whether the air-fuel ratio is rich or lean;

catalyst deterioration determining means for determining deterioration of said three-way catalyst on the basis of the length of a response curve that the output of said O₂ sensor describes during the time that air-fuel ratio feedback control is being performed by said air-fuel ratio feedback control means; and

a response curve length calculation interrupting means for interrupting the calculation of the response curve length being performed by said catalyst deterioration determining means for a predetermined length of time when the output of said air-fuel ratio sensor or the amount of change of said output has exceeded a preset value.

2. A catalyst deterioration detection device for an internal combustion engine, comprising:

a three-way catalyst mounted in an exhaust passage of said internal combustion engine and having an O₂ storage capability;

an air-fuel ratio sensor, mounted upstream of said three-way catalyst, for linearly detecting air-fuel ratio;

air-fuel ratio feedback control means for, based on the output of said air-fuel ratio sensor, calculating a feedback correction amount consisting of a proportional term for bringing the air-fuel ratio to stoichiometry and an integral term for bringing an integrated value of an error between the air-fuel ratio and stoichiometry to zero;

an O₂ sensor, mounted downstream of said three-way catalyst, for detecting whether the air-fuel ratio is rich or lean;

catalyst deterioration determining means for determining deterioration of said three-way catalyst on the basis of the length of a response curve that the output of said O₂ sensor describes during the time that air-fuel ratio feedback control is being performed by said air-fuel ratio feedback control means; and

integral term limiting means for imposing an upper limit on an absolute value of said integral term or on a gain of said integral term when processing for determination is being performed by said catalyst deterioration determining means.

3. A catalyst deterioration detection device for an internal combustion engine, comprising:

a three-way catalyst mounted in an exhaust passage of said internal combustion engine and having an O₂ storage capability;

an air-fuel ratio sensor, mounted upstream of said three-way catalyst, for linearly detecting air-fuel ratio;

first air-fuel ratio feedback control means for, based on the output of said air-fuel ratio sensor, calculating a feedback correction amount consisting of a proportional term for bringing the air-fuel ratio to stoichiometry and an integral term for bringing an integrated value of an error between the air-fuel ratio and stoichiometry to zero;

an O₂ sensor, mounted downstream of said three-way catalyst, for detecting whether the air-fuel ratio is rich or lean;

second air-fuel ratio feedback control means for correcting the output of said air-fuel ratio sensor on the basis of the output of said O₂ sensor;

catalyst deterioration determining means for determining deterioration of said three-way catalyst on the basis of the length of a response curve that the output of said O₂ sensor describes during the time that air-fuel ratio feedback control is being performed by said first air-fuel ratio feedback control means; and

air-fuel ratio sensor output correction inhibiting means for inhibiting the correction of the output of said air-fuel ratio sensor by said second air-fuel ratio feedback control means when processing for determination is being performed by said catalyst deterioration determining means.

4. A catalyst deterioration detection device for an internal combustion engine, comprising:

a three-way catalyst mounted in an exhaust passage of said internal combustion engine and having an O₂ storage capability;

an air-fuel ratio sensor, mounted upstream of said three-way catalyst, for linearly detecting an air-fuel ratio;

air-fuel ratio feedback control means for feedback controlling the air-fuel ratio toward stoichiometry on the basis of the output of said air-fuel ratio sensor;

an O₂ sensor, mounted downstream of said three-way catalyst, for detecting whether the air-fuel ratio is rich or lean;

catalyst deterioration determining means for determining deterioration of said three-way catalyst by comparing the length of a response curve that the output of said O₂ sensor describes or the ratio of the response curve length of the output of said O₂ sensor to that of the output of said air-fuel ratio sensor with a deterioration determination reference value during the time that air-fuel ratio feedback control is being performed by said air-fuel ratio feedback control means; and

catalyst deterioration determination limiting means for imposing a limit so that the determination by said catalyst deterioration determining means is carried out only when the response curve length or variation amplitude of the output of said air-fuel ratio sensor is within a prescribed range.

5. A catalyst deterioration detection device for an internal combustion engine, comprising:

a three-way catalyst mounted in an exhaust passage of said internal combustion engine and having an O₂ storage capability;

an air-fuel ratio sensor, mounted upstream of said three-way catalyst, for linearly detecting an air-fuel ratio;

air-fuel ratio feedback control means for feedback controlling the air-fuel ratio toward stoichiometry on the basis of the output of said air-fuel ratio sensor;

an O₂ sensor, mounted downstream of said three-way catalyst, for detecting whether the air-fuel ratio is rich or lean;

catalyst deterioration determining means for determining deterioration of said three-way catalyst by comparing the length of a response curve that the output of said O₂ sensor describes or the ratio of the response curve length of the output of said O₂ sensor to that of the output of said air-fuel ratio sensor with a deterioration determination reference value during the time that air-fuel ratio feedback control is being performed by said air-fuel ratio feedback control means; and

reference value changing means for changing said deterioration determination reference value according to the response curve length or variation amplitude of the output of said air-fuel ratio sensor.