Methods and systems for diagnosing an intake oxygen sensor based on pressure

Patent metadata

Field	Value
Publication number	US-9528476-B2
Application number	US-201414573060-A
Country	US
Kind code	B2
Filing date	Dec 17, 2014
Priority date	Dec 17, 2014
Publication date	Dec 27, 2016
Grant date	Dec 27, 2016

Abstract

Methods and systems are provided for diagnosing an intake oxygen sensor. In one example, a method may include indicating degradation of an intake oxygen sensor based on a first time constant of an output of the intake oxygen sensor and a second time constant of an output of a throttle inlet pressure sensor. The method may further include adjusting EGR flow based on the output of the intake oxygen sensor and the output of the throttle inlet pressure sensor when the intake oxygen sensor is not degraded.

First claim

The invention claimed is:

1. A method comprising:
indicating degradation of an intake oxygen sensor based on a first time constant of an output of the intake oxygen sensor and a second time constant of an output of a throttle inlet pressure sensor.

2. The method of claim 1 , wherein the throttle inlet pressure sensor is disposed in an engine air intake system directly upstream of an intake throttle and wherein the intake oxygen sensor is positioned in the engine air intake system upstream of the throttle inlet pressure sensor.

3. The method of claim 1 , further comprising diagnosing the intake oxygen sensor in response to the output of the throttle inlet pressure sensor changing by a threshold amount over a duration, wherein the diagnosing includes indicating degradation of the intake oxygen sensor in response to a difference between the first time constant and the second time constant being greater than a threshold difference.

4. The method of claim 1 , wherein indicating degradation of the intake oxygen sensor includes one or more of setting a diagnostic flag and alerting a vehicle operator via a visual or audible signal that the intake oxygen sensor is degraded.

5. The method of claim 1 , further comprising, responsive to the indicating degradation of the intake oxygen sensor, not estimating an exhaust gas recirculation flow (EGR) based on the output of the intake oxygen sensor, and adjusting an EGR valve in response to the estimate of EGR flow that is not based on the output of the intake oxygen sensor.

6. The method of claim 1 , further comprising, responsive to the indicating degradation of the intake oxygen sensor, estimating the EGR flow based on a pressure difference across an EGR valve disposed in an EGR passage, the EGR passage positioned between an exhaust passage and an intake passage upstream of the intake oxygen sensor.

7. The method of claim 1 , further comprising in response to a difference between the first time constant and the second time constant being less than a threshold difference, adjusting the output of the intake oxygen sensor based on the output of the throttle inlet pressure sensor.

8. The method of claim 7 , further comprising adjusting an EGR valve based on the adjusted output of the intake oxygen sensor.

9. A method, comprising:
when a change in an inlet pressure at an intake throttle is greater than a threshold amount, diagnosing an intake oxygen sensor based on a difference between a first time constant of a signal output by the intake oxygen sensor and a second time constant of a signal output by a throttle inlet pressure sensor.

10. The method of claim 9 , wherein the diagnosing includes indicating degradation of the intake oxygen sensor in response to the difference between the first time constant and the second time constant being greater than a threshold difference, wherein indicating degradation includes one or more of setting a diagnostic code and alerting a vehicle operator.

11. The method of claim 10 , further comprising in response to the indicating degradation, adjusting a position of an EGR valve based on an output based on an alternate EGR flow estimate and not based on an output of the intake oxygen sensor, and in the absence of degradation, adjusting the position of the EGR valve based on the intake oxygen sensor.

12. The method of claim 9 , wherein the change in the inlet pressure of the intake throttle includes an average difference between a maximum and minimum value of a pressure waveform output by the throttle inlet pressure sensor over a duration.

13. The method of claim 9 , wherein the diagnosing includes not indicating degradation of the intake oxygen sensor in response to the difference between the first time constant and the second time constant being less than a threshold difference, subsequently correcting an output of the intake oxygen sensor based on an output of the throttle inlet pressure sensor, and adjusting an EGR valve based on the corrected output of the intake oxygen sensor.

14. The method of claim 13 , wherein correcting the output of the intake oxygen sensor includes correcting the output of the intake oxygen sensor based on a current output of the throttle inlet pressure sensor and a reference intake oxygen sensor output at a reference throttle inlet pressure.

15. The method of claim 9 , wherein the first time constant is a first time constant of a time-varying signal output by the intake oxygen sensor and wherein the second time constant is a second time constant of a time-varying signal output by the throttle inlet pressure sensor.

16. The method of claim 9 , wherein the diagnosing is performed in response to a difference between a maximum and minimum value of a time-varying signal of the throttle inlet pressure sensor being greater than a threshold difference.

17. A system, comprising:
an air intake system of an engine including an intake throttle;
a throttle inlet pressure sensor disposed in the air intake system upstream of the intake throttle;
an intake oxygen sensor disposed in the air intake system upstream of the throttle inlet pressure sensor; and
a controller with computer readable instructions for:
indicating degradation of the intake oxygen sensor in response to a difference between a first time constant of a signal output by the intake oxygen sensor and a second time constant of a signal output by the throttle inlet pressure sensor being greater than a threshold difference when the signal of the throttle inlet pressure is fluctuating by a threshold amount.

18. The system of claim 17 , wherein when the signal of the throttle inlet pressure is fluctuating by a threshold amount includes when an average change in the signal of throttle inlet pressure is greater than the threshold amount over a duration.

19. The system of claim 17 , further comprising an exhaust gas recirculation (EGR) passage coupled between an exhaust passage and an intake passage of the air intake system upstream of the intake oxygen sensor, the EGR passage including an EGR valve with a differential pressure over valve (DPOV) sensor and wherein the computer readable instructions further include instructions for adjusting a position of the EGR valve based on an output of the DPOV sensor and not the intake oxygen sensor in response to indicating degradation of the intake oxygen sensor.

20. The system of claim 17 , wherein indicating degradation includes one or more of alerting a vehicle operator that sensor is degraded and setting a diagnostic code.

Assignees

• Ford Global Tech Llc

Inventors

• Surnilla Gopichandra
• Kim Yong-Wha
• Uhrich Michael James
• Clark Timothy Joseph

Classifications

• F02M26/47

  the characteristics being temperatures, pressures or flow rates · CPC title

• F02M26/04

  with a single turbocharger · CPC title

• F02B37/18

  by bypassing exhaust {from the inlet to the outlet of turbine or to the atmosphere} · CPC title

• F02B37/007

  with exhaust-driven pumps arranged in parallel {, e.g. at least one pump supplying alternatively} · CPC title

• F02D2041/1431

  the system including an input-output delay · CPC title