System and methods for adjusting an exhaust gas recirculation valve based on multiple sensor outputs

Patent metadata

Field	Value
Publication number	US-9970348-B2
Application number	US-201514616354-A
Country	US
Kind code	B2
Filing date	Feb 6, 2015
Priority date	Feb 6, 2015
Publication date	May 15, 2018
Grant date	May 15, 2018

Abstract

Methods and systems are provided for adjusting an exhaust gas recirculation (EGR) valve based on a final EGR estimate. In one example, a method may include adjusting the EGR valve based on a final EGR flow estimate, the final EGR flow estimate based on a first EGR flow estimated with a differential pressure sensor across the EGR valve, a second EGR flow estimated with an intake oxygen sensor, and accuracy values of each of the first and second EGR flows. The accuracy value may be based on engine operating conditions during estimation of the first and second EGR flows.

First claim

The invention claimed is:

1. A method for an engine, comprising:
adjusting engine operation based on a final gas flow parameter estimate, the final gas flow parameter estimate based on each of a first gas flow parameter estimated with a first sensor, a second gas flow parameter estimated with a second sensor positioned away from the first sensor in a gas passage of the engine, and accuracy values of each of the first and second gas flow parameters, wherein the final gas flow parameter estimate is a final exhaust gas recirculation (EGR) flow estimate and wherein adjusting engine operation includes adjusting an EGR valve based on the final EGR flow estimate, the final EGR flow estimate based on each of a first EGR flow estimated with a differential pressure sensor across the EGR valve, a second EGR flow estimated with an intake oxygen sensor, and accuracy values of each of the first and second EGR flows.

2. The method of claim 1 , wherein the final EGR flow estimate is further based on an estimation tolerance of estimating the first EGR flow with the differential pressure sensor, the estimation tolerance based on one or more of a differential pressure measured with the differential pressure sensor and a valve lift of the EGR valve.

3. The method of claim 1 , wherein the accuracy values are based on engine operating conditions during estimation of the first EGR flow and the second EGR flow and wherein the accuracy values are integer values between zero and three.

4. The method of claim 1 , further comprising assigning a first accuracy value to the first EGR flow based on each of compressor surge, a position of a compressor bypass valve, and a differential pressure output by the differential pressure sensor.

5. The method of claim 1 , further comprising assigning a second base accuracy value to the second EGR flow based on whether an idle adaption and pressure adaption routine for correcting an output of the intake oxygen sensor has been performed.

6. The method of claim 5 , further comprising modifying the second base accuracy value to determine a final second accuracy value of the second EGR flow based on purge and positive crankcase ventilation (PCV) flow past the intake oxygen sensor.

7. The method of claim 1 , further comprising adjusting the first EGR flow and a first accuracy value of the first EGR flow by a time delay before determining the final EGR flow estimate, the time delay based on a spatial delay accounting for a flow rate and volume between the differential pressure sensor and the intake oxygen sensor.

8. The method of claim 2 , further comprising determining the final EGR flow estimate based on the second EGR flow bounded by the first EGR flow and the estimation tolerance when one of a second accuracy value of the second EGR flow is a first value, the secondary accuracy value is a second value, the second value greater than the first value, and water droplets on the intake oxygen sensor are possible, or when the second accuracy value is a third value, the third value lower than the first value, and a first accuracy value of the first EGR flow is less than the second value.

9. The method of claim 1 , further comprising determining the final EGR flow estimate based on the second EGR flow and not the first EGR flow when a second accuracy value of the second EGR flow is at an upper threshold value and water droplets on the intake oxygen sensor are not expected.

10. The method of claim 1 , further comprising determining the final EGR flow estimate based on one of the first EGR flow or the second EGR flow bounded by the first EGR flow when a first accuracy value of the first EGR flow is at an upper threshold value and a second accuracy value of the second EGR flow is a second value, the second value less than the upper threshold value.

11. A method, comprising:
estimating a first exhaust gas recirculation (EGR) flow with a differential pressure sensor across an EGR valve and a second EGR flow with an intake oxygen sensor;
assigning a first accuracy value to the first EGR flow and a second accuracy value to the second EGR flow based on engine operating conditions and sensor conditions; and
adjusting the EGR valve based on a final EGR flow estimate, the final EGR flow estimate based on the first EGR flow, the second EGR flow, the first accuracy value, and the second accuracy value.

12. The method of claim 11 , wherein the first accuracy value decreases when a differential pressure measured by the differential pressure sensor is less than a threshold, during a compressor surge event, when a compressor bypass valve is opening, and when a flag is set indicating a fault of the differential pressure sensor.

13. The method of claim 11 , wherein the second accuracy value decreases when adaption routines to correct an output of the intake oxygen sensor have not been run, as purge flow to the intake oxygen sensor increases, and as positive crankcase ventilation (PCV) flow to the intake oxygen sensor increases.

14. The method of claim 11 , further comprising determining a tolerance interval of the first EGR flow, the tolerance interval based on a differential pressure measured by the differential pressure sensor and a valve lift of the EGR valve.

15. The method of claim 14 , further comprising combining the first EGR flow and the second EGR flow into the final EGR flow estimate, where the combining is based on the first accuracy value, the second accuracy value, and an estimation tolerance.

16. The method of claim 11 , further comprising when one or more of the second accuracy value is less than a first value and the second accuracy value is the first value while water droplets on the intake oxygen sensor are possible, restricting the second EGR flow to be within the tolerance interval of the first EGR flow and determining the final EGR flow estimate based on the restricted second EGR flow and further comprising when the second accuracy value is the first value and water droplets on the intake oxygen sensor are not possible, determining the final EGR flow estimate to be the second EGR flow and not the first EGR flow.

17. A system, comprising:
a turbocharger with an intake compressor and an exhaust turbine;
a low-pressure exhaust gas recirculation (EGR) passage coupled between an exhaust passage downstream of the exhaust turbine and an intake passage upstream of the intake compressor, the low-pressure EGR passage including an EGR valve and a differential pressure (DP) sensor for measuring EGR flow;
an intake oxygen sensor disposed in an intake of an engine downstream from the low-pressure EGR passage; and
a controller with computer-readable instructions for:
determining a final EGR flow estimate based on a first EGR flow estimate based on an output of the DP sensor, a second EGR flow estimate based on an output of the intake oxygen sensor, a first accuracy value of the first EGR flow estimate, and a second accuracy value of the second EGR flow estimate.

18. The system of claim 17 , wherein the first accuracy value is an integer value based on one or more of compressor surge, a position of a compressor bypass valve, and a differential pressure output by the DP sensor.

19. The system of claim 17 , wherein the second accuracy value is an integer value base on one or more of whether an idle adaption and pressure adaption routine for correcting an output of the intake oxygen sensor has been performed, an amount of purge flow past the intake oxygen sensor, and an amount of PCV flow past the intake oxygen sensor.

Assignees

• Ford Global Tech Llc

Inventors

• Hagner David G
• Surnilla Gopichandra
• Hilditch James Alfred

Classifications

• F02B37/00 Primary

  Engines characterised by provision of pumps driven at least for part of the time by exhaust · CPC title

• F02D41/005

  according to engine operating conditions · CPC title

• F02D41/0007

  for control of turbo-charged or super-charged engines (control of the pumps per se F02B37/12) · CPC title

• F02M26/47

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

• F02D41/1454

  the characteristics being an oxygen content or concentration or the air-fuel ratio · CPC title