Non-intrusive exhaust gas sensor monitoring

Patent metadata

Field	Value
Publication number	US-9541469-B2
Application number	US-201414572076-A
Country	US
Kind code	B2
Filing date	Dec 16, 2014
Priority date	Mar 1, 2012
Publication date	Jan 10, 2017
Grant date	Jan 10, 2017

Abstract

A method for monitoring an exhaust gas sensor coupled in an engine exhaust is provided. In one embodiment, the method comprises indicating exhaust gas sensor degradation based on a time delay and line length of each sample of a set of exhaust gas sensor responses collected during a commanded change in air-fuel ratio. In this way, the exhaust gas sensor may be monitored utilizing robust parameters in a non-intrusive manner.

First claim

The invention claimed is:

1. A method of monitoring an exhaust gas sensor coupled in an engine exhaust, comprising:
indicating exhaust gas sensor degradation based on a time delay and line length of each sample of a set of exhaust gas sensor responses collected during each of entry into and exit out of deceleration fuel shut-off (DFSO).

2. The method of claim 1 , wherein during entry into DFSO, an engine is commanded from stoichiometric operation to lean operation.

3. The method of claim 1 , wherein during exit out of DFSO, an engine is commanded from lean operation to stoichiometric operation.

4. The method of claim 1 , further comprising, for each sample of the set of exhaust gas sensor responses, determining if an air-fuel ratio disturbance is present prior to the entry into DFSO.

5. The method of claim 4 , wherein,
if an air-fuel ratio disturbance is present, then not including that exhaust sample in the set of exhaust gas sensor responses; and
if an air-fuel ratio disturbance is not present, then including that sample in the set of exhaust gas sensor responses.

6. The method of claim 4 , wherein the time delay is a duration from commanded entry into DFSO to a threshold change in lambda, and wherein the line length is based on a change of lambda over time during the exhaust gas sensor response.

7. The method of claim 6 , further comprising:
if an average time delay of exhaust gas sensor responses during DFSO entry exceeds an expected entry time delay, and an average time delay of exhaust gas sensor responses during DFSO exit does not exceed an expected exit time delay, indicating a rich-to-lean delay sensor degradation.

8. The method of claim 6 , further comprising:
if an average line length of exhaust gas sensor responses during DFSO entry exceeds an expected entry line length and an average line length of exhaust gas sensor responses during DFSO exit does not exceed an expected exit line length, indicating a rich-to-lean filter sensor degradation.

9. The method of claim 6 , further comprising:
if an average time delay of exhaust gas sensor responses during DFSO entry exceeds an expected entry time delay and an average time delay of exhaust gas sensor responses during DFSO exit exceeds an expected exit time delay, indicating a symmetric delay sensor degradation.

10. The method of claim 1 , further comprising, for each sample of the set of exhaust gas sensor responses, determining if an air-fuel ratio disturbance is present prior to exit out of DFSO.

11. The method of claim 10 , wherein,
if an air-fuel ratio disturbance is present, then not including that exhaust sample in the set of exhaust gas sensor responses; and
if an air-fuel ratio disturbance is not present, then including that sample in the set of exhaust gas sensor responses.

12. The method of claim 10 , wherein the time delay is a duration from a commanded exit out of DFSO to a threshold change in lambda, and wherein the line length is based on a change of lambda over time during the exhaust gas sensor response.

13. The method of claim 12 , further comprising:
if an average time delay of exhaust gas sensor responses during DFSO exit exceeds an expected exit time delay and an average time delay of exhaust gas sensor responses during DFSO entry does not exceed an expected entry time delay, indicating a lean-to-rich delay sensor degradation.

14. The method of claim 12 , further comprising if an average line length of exhaust gas sensor responses during DFSO exit exceeds an expected exit line length and an average line length of exhaust gas sensor responses during DFSO entry does not exceed an expected entry line length, indicating a lean-to-rich filter sensor degradation.

15. The method of claim 12 , further comprising if an average line length of exhaust gas sensor responses during DFSO exit exceeds an expected exit line length and an average line length of exhaust gas sensor responses during DFSO exit exceeds an expected entry line length, indicating a symmetric filter sensor degradation.

16. The method of claim 1 , further comprising adjusting a fuel injection amount based on the indicated degradation, where said degradation includes asymmetric sensor responses to air-fuel ratio excursions.

17. The method of claim 1 , further comprising adjusting a fuel injection timing based on the indicated degradation, where said degradation includes asymmetric sensor responses to air-fuel ratio excursions.

18. A system for a vehicle, comprising:
an engine including a fuel injection system;
an exhaust gas sensor coupled in an exhaust system of the engine; and
a controller including instructions executable to:
for each entry into and exit out of DFSO, if an air-fuel ratio disturbance is not present prior to the entry or exit, then add a collected change in lambda over time during the entry or exit to a set of exhaust gas sensor responses;
indicate exhaust gas sensor degradation based on a time delay and line length of each sample of the set of exhaust gas sensor responses; and
adjust a fuel injection amount and/or timing based on the indicated degradation.

19. The system of claim 18 , wherein the instructions are further executable to notify an operator of the vehicle if the indicated sensor degradation exceeds a threshold.

20. The system of claim 18 , wherein the instructions are further executable, for each exit and entry, to determine a time constant from the collected change in lambda and determine predicted threshold response time based on the time constant.

21. A method of monitoring an oxygen sensor coupled in an engine exhaust, comprising:
collecting a set of exhaust gas sensor responses during entry into and exit out of DFSO;
based on the set of exhaust gas sensor responses,
indicating an asymmetric delay sensor degradation if one of an average entry or exit time delay exceeds a respective expected entry or exit delay;
indicating an asymmetric filter sensor degradation if one of an average entry or exit line length exceeds a respective expected entry or exit line length; and
adjusting a fuel injection amount based on an indicated sensor degradation, wherein the indicating includes generating an indication light.

Assignees

• Ford Global Tech Llc

Inventors

• Uhrich Michael James
• Banker Adam Nathan
• Kerns James Michael
• Makki Imad Hassan

Classifications

• F01N2550/20

  Monitoring artificially aged exhaust systems · CPC title

• F01N11/007 Primary

  the diagnostic devices measuring oxygen or air concentration downstream of the exhaust apparatus · CPC title

• G01M15/104 Primary

  using oxygen or lambda-sensors (testing catalytic converters F01N3/18, F01N11/007) · CPC title

• F01N2560/025

  for measuring or detecting O2, e.g. lambda sensors · CPC title

• F02D41/123

  the fuel injection being cut-off · CPC title