Methods and systems for an oxygen sensor

Patent metadata

Field	Value
Publication number	US-2016245212-A1
Application number	US-201615144584-A
Country	US
Kind code	A1
Filing date	May 2, 2016
Priority date	Oct 11, 2013
Publication date	Aug 25, 2016
Grant date	—

Abstract

Methods and systems are provided for accurately learning the zero point of an intake gas oxygen sensor during selected engine no-fueling 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 a DFSO adaptation relative to a zero point learned during an idle adaptation.

First claim

1 . A method for an engine system, comprising:
learning a reference point for an intake oxygen sensor at a reference intake pressure during non-fueling conditions; and adjusting EGR flow to the engine based on an intake oxygen concentration estimated by the sensor relative to the learned reference point, and further based on a change in intake pressure from the reference intake pressure, EGR flow adjusted via a low-pressure EGR valve actuated by an engine controller.

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

3 . The method of claim 1 , wherein the non-fueling conditions include an engine deceleration fuel shut-off condition (DFSO).

4 . The method of claim 1 , wherein the non-fueling conditions includes a first engine idle or DFSO since installation of one or more of the intake oxygen sensor and an intake pressure sensor configured to estimate the reference intake pressure.

5 . The method of claim 4 , wherein each of the intake oxygen sensor and the pressure sensor are positioned in an engine intake manifold, downstream of a charge air cooler and upstream of an intake throttle.

6 . The method of claim 1 , wherein learning the reference point includes correcting an output of the intake oxygen sensor estimated at the reference pressure with a correction factor based on ambient humidity.

7 . The method of claim 6 , wherein learning the reference point further includes performing a recursive least squares adaptation for pressure correction.

8 . The method of claim 1 , wherein adjusting EGR flow to the engine 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.

9 . The method of claim 8 , 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 idling conditions.

10 . The method of claim 9 , further comprising, indicating low-pressure EGR valve degradation based on a difference between the first learned reference point and the second learned reference point learned during DFSO being larger than a threshold amount.

11 . The method of claim 10 , wherein adjusting EGR flow to the engine includes feedback adjusting EGR flow to the engine based on the intake oxygen concentration estimated by the sensor relative to the learned reference point and further based on a change in intake pressure from the reference intake pressure, the EGR flow feed-forward adjusted based on engine speed-load conditions, and wherein in response to the indication of the low-pressure EGR valve degradation, the method further includes terminating feedback adjustment of EGR flow based on the intake oxygen concentration estimated by the sensor relative to the learned reference point and further based on a change in intake pressure from the reference intake pressure and only feed-forward adjusting the EGR flow.

12 . The method of claim 1 , wherein the estimated intake oxygen concentration is scaled to an 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.

13 . A method for an engine, comprising:
indicating EGR valve leakage by comparing a first reference point of an intake oxygen sensor learned during engine idling conditions relative to a second reference point of the oxygen sensor learned during engine non-fueling conditions; and adjusting EGR flow via the EGR valve actuated by an engine controller.

14 . The method of claim 13 , wherein the indicating includes indicating EGR valve leakage based on the comparison between the first reference point and the second reference point to generate a difference, and further based on the difference between the first reference point and the second reference point being larger than a threshold.

15 . The method of claim 14 , further comprising, in response to an indication of no EGR valve leakage, feed-forward adjusting the EGR valve based on engine speed-load conditions while feedback adjusting the EGR valve based on an output of the intake oxygen sensor relative to one of the first and second reference point; and
in response to an indication of EGR valve leakage, feed-forward adjusting the EGR valve based on engine speed-load conditions while terminating feedback adjusting of the EGR valve based on the output of the intake oxygen sensor relative to one of the first and second reference point.

16 . The method of claim 13 , wherein the EGR valve is coupled to a low pressure EGR passage configured to recirculate exhaust residuals from an exhaust manifold, downstream of a turbine to an intake manifold, upstream of a compressor.

17 . The method of claim 16 , wherein the intake oxygen sensor is coupled to an engine intake manifold, upstream of an intake throttle and either upstream or downstream of a charge air cooler, the cooler coupled downstream of the compressor.

18 . The method of claim 17 , wherein each of the first and second reference points are learned at a reference intake pressure, the reference intake pressure estimated by an intake pressure sensor coupled to the engine intake manifold, upstream of the intake throttle and downstream of the charge air cooler.

19 . 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 an engine deceleration fuel shut-off condition,
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.

20 . The system of claim 19 , 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.

Assignees

• Ford Global Tech Llc

Inventors

• Clark Timothy Joseph
• Surnilla Gopichandra
• Gerhart Matthew John
• Styles Daniel Joseph

Classifications

• F02D41/2445

  characterised by a plurality of learning conditions or ranges · CPC title

• F02D41/2474 Primary

  Characteristics of sensors · CPC title

• F02D41/0072

  Estimating, calculating or determining the EGR rate, amount or flow (sensors in EGR systems F02M26/45) · CPC title

• F02M26/08

  for engines having two or more intake charge compressors or exhaust gas turbines, e.g. a turbocharger combined with an additional compressor · CPC title

• F02D41/08

  for idling (F02D41/06, F02D41/16 take precedence) · CPC title