Systems and methods for detecting exhaust air leak

Patent metadata

Field	Value
Publication number	US-10480368-B2
Application number	US-201715688627-A
Country	US
Kind code	B2
Filing date	Aug 28, 2017
Priority date	Aug 28, 2017
Publication date	Nov 19, 2019
Grant date	Nov 19, 2019

Abstract

Methods and systems are provided for differentiating an exhaust air leak from a catalyst monitor sensor degraded with a slow-response. In one example, a pressure proximate an exhaust system particulate filter less than a threshold pressure may indicate an exhaust air leak and responsive to the indication of the exhaust air leak, the thresholds for monitoring the catalyst monitor sensor response may be adjusted. In this way, the impact of an exhaust air leak on catalyst monitor output may be accounted for so that subsequent monitoring for threshold catalyst may continue to be performed accurately in the presence of an exhaust air leak.

First claim

The invention claimed is:

1. A method for an engine, comprising:
adjusting a diagnostic threshold of an oxygen sensor coupled downstream of an exhaust catalyst responsive to a measured pressure at a particulate filter coupled downstream of the oxygen sensor; and
responsive to an indication of degradation of the catalyst, which is responsive to a measured output of the oxygen sensor, reducing a peak-to-peak air-fuel ratio during an air-fuel ratio oscillation.

2. The method of claim 1 , wherein the measured pressure at the particulate filter includes one of a measured inlet pressure of the particulate filter and a differential pressure across the particulate filter.

3. The method of claim 1 , wherein the adjusting responsive to the measured pressure includes adjusting responsive to the measured pressure exceeding a first threshold, the first threshold calibrated based on a soot load at the particulate filter, the method further comprising, responsive to the measured pressure exceeding a second threshold, higher than the first threshold, indicating particulate filter degradation.

4. The method of claim 3 , wherein the adjusting includes increasing the diagnostic threshold responsive to the measured pressure exceeding the first threshold, the diagnostic threshold increased further as a difference between the measured pressure and the first threshold increases.

5. The method of claim 3 , further comprising indicating an exhaust air leak responsive to the measured pressure exceeding the first threshold.

6. The method of claim 1 , wherein the diagnostic threshold is a first diagnostic threshold for an oxygen sensor monitor routine, the method further comprising:
initiating the oxygen sensor monitor routine responsive to corresponding monitor entry conditions being met;
indicating degradation of the oxygen sensor responsive to a measured output of the oxygen sensor exceeding the first diagnostic threshold; and
responsive to the indication of degradation of the oxygen sensor, adjusting a second diagnostic threshold for a catalyst monitor routine.

7. The method of claim 6 , wherein indicating degradation of the oxygen sensor includes indicating slow sensor response.

8. The method of claim 6 , further comprising:
initiating the catalyst monitor routine responsive to corresponding monitor entry conditions being met.

9. The method of claim 8 , wherein indicating degradation of the catalyst includes indicating catalyst aging.

10. A method, comprising:
oscillating an air-fuel ratio of an engine;
indicating an air leak in an exhaust passage of the engine based on a measured pressure at a particulate filter coupled downstream of an exhaust catalyst;
adjusting a threshold for a monitor routine of an oxygen sensor responsive to the indication of the air leak, the oxygen sensor coupled downstream of the catalyst; and
indicating a degraded sensor response based on oxygen sensor output during the air-fuel ratio oscillation relative to the threshold.

11. The method of claim 10 , wherein the measured pressure includes one of a particulate filter inlet pressure and a differential pressure across the particulate filter.

12. The method of claim 10 , wherein the threshold is a first threshold and the air-fuel ratio oscillation is a first air-fuel ratio oscillation, the method further comprising:
adjusting a second threshold for a catalyst monitor routine responsive to the indication of degraded sensor response; and
indicating catalyst aging based on oxygen sensor output during a second air-fuel ratio oscillation relative to the second threshold.

13. The method of claim 12 , wherein the adjusting includes:
increasing the first threshold responsive to the indication of the air leak; and
increasing the second threshold responsive to the indication of degraded sensor response.

14. The method of claim 12 , further comprising:
indicating a state of the particulate filter based on the measured pressure; and
limiting an engine load based on the indicating.

15. The method of claim 14 , wherein the indicating includes:
indicating the air leak in the exhaust passage responsive to the measured pressure being higher than a first threshold pressure; and
indicating a degraded state of the particulate filter responsive to the measured pressure being higher than a second threshold pressure, higher than the first threshold pressure, the first threshold pressure calibrated as a function of filter soot load and engine speed.

16. An engine system, comprising:
an engine;
an exhaust passage including an exhaust catalyst;
an upstream oxygen sensor coupled upstream of the exhaust catalyst;
a downstream oxygen sensor coupled downstream of the exhaust catalyst;
a particulate filter coupled downstream of the downstream oxygen sensor;
a pressure sensor coupled to the particulate filter; and
a controller with computer readable instructions stored on non-transitory memory for:
responsive to entry conditions for a first monitor routine of the downstream oxygen sensor being met,
comparing an output of the pressure sensor to a threshold pressure; and
raising a threshold of the first monitor routine responsive to the output of the pressure sensor being higher than the threshold pressure;
executing the first monitor routine; and
indicating degradation of the downstream oxygen sensor responsive to an output of the downstream oxygen sensor exceeding the raised threshold following the executing of the first monitor routine.

17. The system of claim 16 , wherein the pressure sensor is one of an absolute pressure sensor coupled to an inlet of the particulate filter, and a differential pressure sensor coupled to each of the inlet and an outlet of the particulate filter.

18. The system of claim 16 , wherein the threshold pressure is a first threshold pressure, and wherein the controller includes further instructions for:
comparing the output of the pressure sensor to a second threshold pressure, higher than the first threshold pressure;
indicating degradation of the particulate filter responsive to the output of the pressure sensor exceeding the second threshold pressure; and
responsive to the indicating, limiting an engine load until an operator input indicating replacement of the particulate filter is received.

19. The system of claim 16 , where the controller includes further instructions for:
responsive to entry conditions for a second monitor routine of the catalyst being met,
raising a threshold of the first monitor routine responsive to the indication of degradation of the downstream oxygen sensor;
executing the second monitor routine; and
indicating degradation of the catalyst responsive to the output of the downstream oxygen sensor exceeding the raised threshold following the executing of the second monitor routine.

20. The system of claim 19 , wherein executing each of the first monitor routine and the second monitor routine includes oscillating an air-fuel ratio between a richer than stoichiometric air-fuel ratio and a leaner than stoichiometric air-fuel ratio, and wherein the controller includes further instructions for:
responsive to the indication of degradation of the catalyst, reducing an amplitude of the air-fuel ratio oscillation.

Assignees

• Ford Global Tech Llc

Inventors

• Santillo Mario Anthony
• Uhrich Michael James
• Ulrey Joseph Norman
• Bagnasco Andrew
• Casedy Michael

Classifications

• F01N2900/1406

  Exhaust gas pressure · CPC title

• F01N11/002

  the diagnostic devices measuring or estimating temperature or pressure in, or downstream of the exhaust apparatus · CPC title

• F01N2900/1606

  Particle filter loading or soot amount · CPC title

• F01N13/008

  Mounting or arrangement of exhaust sensors in or on exhaust apparatus (sensor arrangements for engine control F02D41/1439) · CPC title

• F01N2410/00

  By-passing, at least partially, exhaust from inlet to outlet of apparatus, to atmosphere or to other device · CPC title