METHODS AND SYSTEMS FOR AN OXYGEN SENSOR

• US 20150101328A1
• Filed: 10/11/2013
• Published: 04/16/2015
• 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, Clark, Timothy Joseph, Soltis, Richard E., Visser, Jacobus Hendrik, House, Christopher
• Granted Patent: US 9,273,621 B2
• Time in Patent Office: Days
• US Class Current: 60/599
• CPC Class Codes: F02B 29/0406 Layout of the intake air cooling or coolant circuit
• CPC Class Codes: F02B 37/001 using exhaust drives arranged in parallel
• CPC Class Codes: F02B 37/007 with exhaust-driven pumps arranged in parallel , e.g. at least one pump supplying alternatively
• CPC Class Codes: F02B 37/18 by bypassing exhaust from the inlet to the outlet of turbine or to the atmosphere
• CPC Class Codes: F02D 2200/0418 Air humidity
• CPC Class Codes: F02D 41/005 according to engine operating conditions
• 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 41/0235 in relation with the state of the exhaust gas treating apparatus control of exhaust gas treating apparatus per se F01N
• 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 41/2474 Characteristics of sensors
• 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 26/23 Layout, e.g. schematics
• CPC Class Codes: F02M 26/42 having two or more EGR passages; EGR systems specially adapted for engines having two or more cylinders
• CPC Class Codes: F02M 26/49 Detecting, diagnosing or indicating an abnormal function of the EGR system
• CPC Class Codes: F02M 35/10222 Exhaust gas recirculation [EGR]; Positive crankcase ventilation [PCV]; Additional air admission, lubricant or fuel vapour admission
• CPC Class Codes: F02M 35/10393 for characterising a multi-component mixture, e.g. for the composition such as humidity, density or viscosity
• 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 in varying ambient humidity conditions. The learned zero point is corrected based on an estimated ambient humidity to calibrate the reading for dry air conditions or standard humidity conditions. EGR control is performed by comparing the output of an intake oxygen sensor during EGR conditions relative to the humidity-corrected zero point.

Claims

1. A method for an engine, comprising:

estimating an ambient humidity while learning a reference point for an intake oxygen sensor at a reference intake pressure; and

correcting the learned reference point based on the estimated ambient humidity.

2. The method of claim 1, wherein the ambient humidity is estimated an intake humidity sensor, and wherein each of the humidity sensor and the oxygen sensor are positioned upstream of an intake throttle and downstream of a charge air cooler in an engine intake manifold.

3. The method of claim 1, wherein learning a reference point includes learning a nominal amount of oxygen based on an output of the intake oxygen sensor at the reference intake pressure during selected engine idling conditions or selected engine non-fueling conditions.

4. The method of claim 3, wherein correcting the learned reference point based on the estimated ambient humidity includes calculating an amount of oxygen displaced by the estimated ambient humidity, and adding the calculated amount of oxygen to the learned nominal amount of oxygen to correct the reference point to dry air.

5. The method of claim 4, wherein the correcting further includes, after correcting the reference point to dry air, calibrating the reference point to a standard humidity level.

6. The method of claim 5, further comprising, adjusting EGR flow to the engine based on an intake oxygen concentration estimated by the sensor relative to the corrected reference point, and further based on a change in intake pressure from the reference intake pressure.

7. The method of claim 5, wherein the reference intake pressure is one of a throttle inlet pressure and an intake manifold pressure.

8. The method of claim 3, wherein the selected engine idling conditions include a first engine idle since an engine start.

9. The method of claim 3, wherein the selected engine idling conditions include a first engine idle since installation of the intake oxygen sensor or installation of an intake pressure sensor configured to estimate the reference intake pressure.

10. The method of claim 3, wherein the selected non-fueling conditions include a deceleration fuel shut-off condition.

11. 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, via an EGR valve.

12. The method of claim 11, wherein each of the intake oxygen sensor and humidity sensor are positioned downstream of an output of the EGR passage.

13. A method for an engine, comprising:

correcting a first, nominal output of an intake oxygen sensor, learned during selected engine idling conditions at a reference intake pressure, based on an estimated ambient humidity; and

adjusting EGR flow to the engine based on a second output of the sensor, estimated at a second intake pressure, relative to the corrected first output.

14. The method of claim 13, wherein the EGR flow is further adjusted based on the second intake pressure relative to the reference intake pressure, and wherein the selected engine idling conditions include one of a first engine idle from engine start, a first engine idle following installation of the intake oxygen sensor, and a first engine idle following installation of an intake pressure sensor.

15. The method of claim 13, wherein the correcting includes,

calculating an amount of oxygen displaced by the estimated ambient humidity;

and

increasing the first output to include the amount of displaced oxygen, wherein the increased first output is indicative of a dry air oxygen content.

16. The method of claim 15, wherein the correcting further includes,

adjusting the increased first output based on an amount of oxygen displaceable by a calibrated humidity level, the adjusted output indicative of a calibrated humidity air oxygen content.

17. The method of claim 16, wherein adjusting the EGR flow includes estimating a delivered EGR flow based on a difference between the second output and the corrected first output, and adjusting a position of an EGR valve based on a difference between the delivered EGR flow and a target EGR flow, the target EGR flow based on engine speed-load conditions.

18. 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;

a humidity sensor coupled to the intake manifold downstream of the charge air cooler and upstream of an 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 an oxygen sensor output and a humidity sensor output at a reference intake pressure;

adjusting the oxygen sensor output based on the humidity sensor output; and

during subsequent engine non-idle conditions,

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

19. The system of claim 18, wherein increasing the oxygen sensor output based on the humidity sensor output includes,

during a first condition, estimating a first amount of oxygen displaced by total humidity based on the humidity sensor output and increasing the oxygen sensor output with the first amount of oxygen;

and

during a second condition, estimating a second amount of oxygen displaced by a calibrated humidity based on the humidity sensor output, decreasing the oxygen sensor output with the second amount of oxygen.

20. The system of claim 19, wherein the first condition includes ambient humidity higher than a threshold humidity level, and wherein the second condition includes ambient humidity lower than the threshold humidity level.