Method and device for diagnosing an exhaust gas catalytic converter

• US 8,190,352 B2
• Filed: 08/10/2009
• Issued: 05/29/2012
• Est. Priority Date: 08/12/2008
• Status: Active Grant

• Current Assignee: Vitesco Technologies GmbH (INA-Holding Schaeffler GmbH & Co. KG)
• Original Assignee: Continental Automotive GmbH (Continental AG)
• Inventors: Brandt, Martin, Rösel, Gerd
• Primary Examiner(s): Wolfe, Jr., Willis
• Assistant Examiner(s): Hoang, Johnny
• Application Number:
  US12/538,306
• Publication Number:
  US 20100037592A1
• Time in Patent Office: 1,023 Days
• Field of Search: 701102-105, 701/109, 701/114, 123/672, 123/673, 123/690, 123/694, 123/696, 702/182, 702/183, 702/185, 702/187, 60274-278, 602/85, 73/233.1, 731/147.5, 703/8
• US Class Current: 701/114
• CPC Class Codes: F01N 11/00 Monitoring or diagnostic devices for exhaust-gas treatment apparatus , e.g. for catalytic activity safety, indicating or supervising devices for internal combustion engines F02B77/08; testing of machines G01M13/00
• CPC Class Codes: F01N 9/00 Electrical control of exhaust gas treating apparatus monitoring or diagnostic devices for exhaust-gas treatment apparatus F01N11/00; conjoint electrical control of two or more combustion engine functions F02D43/00
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A first exhaust gas sensor signal (vls_up) of a first exhaust gas sensor (AS1) is detected. In addition, a second exhaust gas sensor signal (vls_down) of a second exhaust gas sensor (AS2) is detected. A relevant first estimated value of an emission of at least one exhaust gas component is determined in relation to a position of the first exhaust gas sensor (AS1) in the exhaust gas tract as a function of the first exhaust gas sensor signal (vls_up) and a relevant second estimated value of an emission of the at least one exhaust gas component is determined in relation to a position of the second exhaust gas sensor (AS2) in the exhaust gas tract as a function of the second exhaust gas sensor signal (vls_down). A conversion rate (K) of the at least one exhaust gas component is estimated as a function of a ratio of the second estimated value and the first estimated value of the determined emission. The exhaust gas catalytic converter is diagnosed as a function of the determined conversion rate (K).

Claims

1. A method for diagnosing an exhaust gas catalytic converter, comprising the steps of:

detecting a first exhaust gas sensor signal of a first exhaust gas sensor which is arranged in an exhaust gas tract upstream of the exhaust gas catalytic converter,

detecting a second exhaust gas sensor signal of a second exhaust gas sensor which is arranged in the exhaust gas tract downstream of the exhaust gas catalytic converter,

determining a relevant first estimated value of an emission of at least one exhaust gas component in relation to a position of the first exhaust gas sensor in the exhaust gas tract as a function of the first exhaust gas sensor signal,

determining a relevant second estimated value of an emission of the at least one gas component in relation to a position of the second exhaust gas sensor in the exhaust gas tract as a relation to the second exhaust gas sensor signal,

estimating a conversion rate of the at least one exhaust gas component as a function of a relation between the second estimated value and the first estimated value of the determined emission, and

diagnosing the exhaust gas catalytic converter as a function of the determined conversion rate.

2. The method according to claim 1, wherein

the first estimated value and the second estimated value are in each case integrated over a predetermined period in time or over a predetermined length of route covered by a motor vehicle and

the conversion rate of the at least one exhaust gas component is estimated as a function of a relation between the integrated second and the integrated first estimated value of the emission.

3. The method according to claim 2, wherein

at least one value, which is representative of a driving profile with which the motor vehicle is currently being driven is each time integrated over the predetermined period of time or over the predetermined distance covered by a motor vehicle,

a correspondence of the driving profile with at least one part of a predetermined test cycle is determined as a function of the at least one integrated value,

the estimated conversion rate is compared with a predetermined conversion rate for the—

at least one—

part of the predetermined test cycle in each case once the correspondence has been determined, and

a first error is detected as a function of the estimated conversion rate and the predetermined conversion rate.

4. The method according to claim 1, wherein

a temperature of the exhaust gas catalytic converter is detected or determined and the relevant estimated conversion rate is allocated,

a chronological sequence of the detected or the determined temperatures of the exhaust gas catalytic converter is checked for the presence of a predetermined temperature curve and

if the predetermined temperature curve is present, a chronological sequence that belongs to a chronological sequence of the detected or the determined temperatures of the exhaust gas catalytic converter of the estimated conversion rates is in each case checked for the presence of a conversion rate curve that is characteristic of a second error.

5. The method according to claim 4, wherein as a function of the chronological sequence of the conversion rates estimated in each case, at least one of a local damage to the exhaust gas catalytic converter in a front part and a local damage to the exhaust gas catalytic converter in a rear part of the exhaust gas catalytic converter is detected as the second error.

6. The method according to claim 4, wherein the predetermined temperature curve represents a monotonously rising or a monotonously falling temperature of the exhaust gas catalytic converter.

7. The method according to claim 4, wherein the predetermined temperature curve includes a rise in the temperature above or a fall in the temperature below a predetermined minimum operating temperature of the exhaust gas catalytic converter.

8. The method according to claim 1, wherein the relevant estimated value of the emission of the at least one exhaust gas component is estimated as a function of an emission model as a function of the first exhaust gas sensor signal or the second exhaust gas sensor signal, a gradient signal, which is determined as a time derivation of the first or the second exhaust gas sensor signals and an mass air flow signal.

9. A device for diagnosing an exhaust gas catalytic converter, the device being operable to

detect a first exhaust gas sensor signal of a first exhaust gas sensor, which is arranged in an exhaust gas tract upstream of the exhaust gas catalytic converter,

detect a second exhaust gas sensor signal of a second exhaust gas sensor, which is arranged in the exhaust gas tract downstream of the exhaust gas catalytic converter,

determine a relevant first estimated value of an emission of at least one exhaust gas component in relation to a position of the first exhaust gas sensor in the exhaust gas tract as a function of the first exhaust gas sensor signal,

determine a relevant second estimated value of an emission of the at least one exhaust gas component in relation to a position of the second exhaust gas sensor in the exhaust gas tract as a function of the second exhaust gas sensor signal,

estimate a conversion rate of the—

at least one—

exhaust gas component as a function of a ratio of the second estimated value and the first estimated value of the emission determined and to

diagnose the exhaust gas catalytic converter as a function of the determined conversion rate.

10. The device according to claim 9, wherein the device is further operable to

integrate the first estimated value and the second estimated value are in each case over a predetermined period in time or over a predetermined length of route covered by a motor vehicle, and to

estimate the conversion rate of the at least one exhaust gas component as a function of a relation between the integrated second and the integrated first estimated value of the emission.

11. The device according to claim 10, wherein

at least one value, which is representative of a driving profile with which the motor vehicle is currently being driven is each time integrated over the predetermined period of time or over the predetermined distance covered by a motor vehicle,

a correspondence of the driving profile with at least one part of a predetermined test cycle is determined as a function of the at least one integrated value,

the estimated conversion rate is compared with a predetermined conversion rate for the—

at least one—

part of the predetermined test cycle in each case once the correspondence has been determined, and

a first error is detected as a function of the estimated conversion rate and the predetermined conversion rate.

12. The device according to claim 9, wherein the device is further operable to

detect or determine a temperature of the exhaust gas catalytic converter and to allocate the relevant estimated conversion rate,

check a chronological sequence of the detected or the determined temperatures of the exhaust gas catalytic converter for the presence of a predetermined temperature curve and

if the predetermined temperature curve is present, to check a chronological sequence that belongs to a chronological sequence of the detected or the determined temperatures of the exhaust gas catalytic converter of the estimated conversion rates in each case for the presence of a conversion rate curve that is characteristic of a second error.

13. The device according to claim 12, wherein as a function of the chronological sequence of the conversion rates estimated in each case, at least one of a local damage to the exhaust gas catalytic converter in a front part and a local damage to the exhaust gas catalytic converter in a rear part of the exhaust gas catalytic converter is detected as the second error.

14. The device according to claim 12, wherein the predetermined temperature curve represents a monotonously rising or a monotonously falling temperature of the exhaust gas catalytic converter.

15. The device according to claim 12, wherein the predetermined temperature curve includes a rise in the temperature above or a fall in the temperature below a predetermined minimum operating temperature of the exhaust gas catalytic converter.

16. The device according to claim 9, wherein the device is further operable to estimate the relevant estimated value of the emission of the at least one exhaust gas component as a function of an emission model as a function of the first exhaust gas sensor signal or the second exhaust gas sensor signal, a gradient signal, which is determined as a time derivation of the first or the second exhaust gas sensor signals and an mass air flow signal.

17. A system for diagnosing an exhaust gas catalytic converter, comprising:

a first exhaust gas sensor which is arranged in an exhaust gas tract upstream of the exhaust gas catalytic converter and provides a first exhaust gas sensor signal,

a second exhaust gas sensor which is arranged in the exhaust gas tract downstream of the exhaust gas catalytic converter and provides a second exhaust gas sensor signal,

means for determining a relevant first estimated value of an emission of at least one exhaust gas component in relation to a position of the first exhaust gas sensor in the exhaust gas tract as a function of the first exhaust gas sensor signal,

means for determining a relevant second estimated value of an emission of the at least one gas component in relation to a position of the second exhaust gas sensor in the exhaust gas tract as a relation to the second exhaust gas sensor signal,

means for estimating a conversion rate of the at least one exhaust gas component as a function of a relation between the second estimated value and the first estimated value of the determined emission, and

means for diagnosing the exhaust gas catalytic converter as a function of the determined conversion rate.

18. The system according to claim 17, wherein

the first estimated value and the second estimated value are in each case integrated over a predetermined period in time or over a predetermined length of route covered by a motor vehicle and

the conversion rate of the at least one exhaust gas component is estimated as a function of a relation between the integrated second and the integrated first estimated value of the emission.

19. The system according to claim 18, wherein

at least one value, which is representative of a driving profile with which the motor vehicle is currently being driven is each time integrated over the predetermined period of time or over the predetermined distance covered by a motor vehicle,

a correspondence of the driving profile with at least one part of a predetermined test cycle is determined as a function of the at least one integrated value,

the estimated conversion rate is compared with a predetermined conversion rate for the—

at least one—

part of the predetermined test cycle in each case once the correspondence has been determined, and

a first error is detected as a function of the estimated conversion rate and the predetermined conversion rate.

20. The system according to claim 17, wherein

a temperature of the exhaust gas catalytic converter is detected or determined and the relevant estimated conversion rate is allocated,

a chronological sequence of the detected or the determined temperatures of the exhaust gas catalytic converter is checked for the presence of a predetermined temperature curve and

if the predetermined temperature curve is present, a chronological sequence that belongs to a chronological sequence of the detected or the determined temperatures of the exhaust gas catalytic converter of the estimated conversion rates is in each case checked for the presence of a conversion rate curve that is characteristic of a second error.