Methods and systems for an oxygen sensor

• US 9,181,887 B2
• Filed: 10/11/2013
• Issued: 11/10/2015
• Est. Priority Date: 10/11/2013
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Surnilla, Gopichandra, Soltis, Richard E., Hilditch, James Alfred, Clark, Timothy Joseph, Gerhart, Matthew John, Rumpsa, Todd Anthony
• Primary Examiner(s): Bradley, Audrey K
• Application Number:
  US14/052,635
• Publication Number:
  US 20150101326A1
• Time in Patent Office: 760 Days
• Field of Search: 602/78, 606/052, 123/568.11, 123/568.16
• US Class Current: 1/1
• CPC Class Codes: F02D 2041/141 using a feed-forward control element
• CPC Class Codes: F02D 2200/0418 Air humidity
• CPC Class Codes: F02D 41/0052 Feedback control of engine parameters, e.g. for control of air/fuel ratio or intake air amount
• CPC Class Codes: F02D 41/0072 Estimating, calculating or determining the EGR rate, amount or flow sensors in EGR systems F02M26/45
• CPC Class Codes: F02D 41/08 for idling F02D41/06, F02D41/16 take precedence
• CPC Class Codes: F02D 41/123 the fuel injection being cut-off
• CPC Class Codes: F02D 41/144 Sensor in intake manifold
• CPC Class Codes: F02D 41/2445 characterised by a plurality of learning conditions or ranges
• CPC Class Codes: F02D 41/2474 Characteristics of sensors
• CPC Class Codes: F02M 25/06 adding lubricant vapours
• CPC Class Codes: F02M 25/089 Layout of the fuel vapour installation
• CPC Class Codes: F02M 26/08 for engines having two or more intake charge compressors or exhaust gas turbines, e.g. a turbocharger combined with an additional compressor
• CPC Class Codes: F02M 26/49 Detecting, diagnosing or indicating an abnormal function of the EGR system
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

Methods and systems are provided for accurately learning the zero point of an intake gas oxygen sensor during selected idling conditions. The learned zero point is used to infer EGR flow and accordingly adjust EGR valve control. In addition, EGR valve leakage is diagnosed based on the zero point learned during an idle adaptation relative to a zero point learned during a DFSO adaptation.

Claims

1. An engine method, comprising:

learning a reference point for an intake oxygen sensor at a reference intake pressure during selected engine idling conditions, including correcting an output of the sensor estimated at the reference intake pressure with a correction factor based on ambient humidity; and

adjusting engine EGR flow, via an EGR valve, based on an intake oxygen concentration estimated by the sensor relative to the learned reference point and a change in intake pressure from the reference intake pressure.

2. The method of claim 1, wherein the reference intake pressure is a throttle inlet pressure.

3. The method of claim 1, wherein the reference intake pressure is an intake manifold pressure.

4. The method of claim 1, wherein the selected engine idling conditions include a first engine idle since an engine start.

5. The method of claim 1, wherein the selected engine idling conditions include a first engine idle since installation of the intake oxygen sensor.

6. The method of claim 1, wherein the selected engine idling conditions include a first engine idle since installation of an intake pressure sensor configured to estimate the reference intake pressure.

7. The method of claim 1, wherein learning the reference point further includes performing a recursive least squares adaptation for pressure correction.

8. The method of claim 1, wherein the estimated intake oxygen concentration is scaled to the output of the intake oxygen sensor at the reference intake pressure by dividing the estimated intake oxygen concentration with a pressure correction factor at a current pressure reading.

9. The method of claim 1, wherein adjusting engine EGR flow includes adjusting low-pressure EGR flow along an EGR passage from an exhaust manifold, downstream of an exhaust turbine, to an intake manifold, upstream of an intake compressor, via the EGR valve.

10. The method of claim 9, wherein the learned reference point is a first learned reference point, the method further comprising learning a second reference point for the intake oxygen sensor at the reference intake pressure during selected engine non-fueling conditions.

11. The method of claim 10, further comprising, indicating EGR valve degradation based on a difference between the first learned reference point and the second learned reference point being larger than a threshold amount.

12. A method for an engine, comprising:

estimating a first output of an intake oxygen sensor at a first intake pressure estimated by an intake pressure sensor during a first engine idle since engine start, the intake oxygen sensor and intake pressure sensor coupled upstream of an intake throttle and downstream of a charge air cooler;

learning a relationship between the first intake oxygen sensor output and the first intake pressure; and

adjusting EGR flow to the engine, via an EGR valve, at a second intake pressure estimated by the intake pressure sensor based on a second output of the intake oxygen sensor estimated at the second intake pressure and the learned relationship.

13. The method of claim 12, wherein the learning is performed at a first engine idle following installation of one or more of the intake oxygen sensor and the intake pressure sensor in the engine.

14. The method of claim 12, wherein the adjusting includes,

calculating a pressure correction factor based on a difference between the first intake pressure and the second intake pressure;

calculating a humidity correction factor based on a difference between ambient humidity at the second intake pressure and a reference humidity;

modifying the second intake oxygen sensor output based on each of the calculated pressure correction factor, humidity correction factor, and the learned relationship; and

adjusting a position of the EGR valve based on the modified second intake oxygen sensor output.

15. The method of claim 14, wherein the EGR valve is coupled in a low pressure EGR passage and wherein the learning is performed at a first engine idle following each engine restart.

16. The method of claim 14, further comprising, indicating degradation of the EGR valve based on the first intake oxygen sensor output estimated at the first intake pressure during the first engine idle since engine start relative to the second intake oxygen sensor output estimated at the first intake pressure during an engine deceleration fuel shut-off condition.

17. An engine system, comprising:

an engine including an intake manifold;

a turbocharger including an exhaust turbine and an intake compressor;

a charge air cooler coupled downstream of the compressor;

an intake oxygen sensor coupled to the intake manifold downstream of the charge air cooler and upstream of an intake throttle;

a pressure sensor coupled to the intake manifold downstream of the charge air cooler and upstream of the intake throttle;

an EGR system including an EGR passage and EGR valve for recirculating exhaust residuals from downstream of the turbine to upstream of the compressor; and

a controller with computer readable instructions for;

during a first engine idle since an engine start,

learning a reference point for the oxygen sensor at a reference intake pressure; and

adjusting an opening of the EGR valve based on an intake oxygen concentration estimated by the sensor relative to the learned reference point, and further based on an intake pressure relative to the reference intake pressure.

18. The system of claim 17, further comprising a humidity sensor for estimating an ambient humidity, the controller including further instructions for further adjusting the opening of the EGR valve based on an ambient humidity relative to a reference humidity.