Method and system for humidity sensor diagnostics

• US 8,881,713 B2
• Filed: 03/10/2011
• Issued: 11/11/2014
• Est. Priority Date: 03/10/2011
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Surnilla, Gopichandra, Makki, Imad Hassan, Uhrich, Michael James, Clark, Timothy Joseph, Kerns, James Michael, Jentz, Robert Roy
• Primary Examiner(s): Vo, Hieu T
• Assistant Examiner(s): Castro, Arnold
• Application Number:
  US13/045,123
• Publication Number:
  US 20120227719A1
• Time in Patent Office: 1,342 Days
• Field of Search: 123/568.22, 123/568.11, 731/143.7, 731/147.4, 731/147.7
• US Class Current: 123/568.22
• CPC Class Codes: F02D 2200/0414 Air temperature
• CPC Class Codes: F02D 2200/0418 Air humidity
• CPC Class Codes: F02D 41/005 according to engine operating conditions
• CPC Class Codes: F02D 41/0065 Specific aspects of external EGR control constructional details of EGR system F02M26/00
• CPC Class Codes: F02D 41/0245 by increasing temperature of the exhaust gas leaving the engine
• CPC Class Codes: F02D 41/064 at cold start F02D41/067 takes precedence
• CPC Class Codes: F02D 41/222 relating to the failure of sensors or parameter detection devices
• CPC Class Codes: F02M 26/07 Mixed pressure loops, i.e. wherein recirculated exhaust gas is either taken out upstream of the turbine and reintroduced upstream of the compressor, or is taken out downstream of the turbine and reintroduced downstream of the compressor
• CPC Class Codes: F02M 26/14 in relation to the exhaust system
• 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 26/45 Sensors specially adapted for EGR systems
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies

Abstract

Methods and systems are provided for an engine including a humidity sensor. Degradation of the humidity sensor may be determined based on a change in intake air relative humidity as compared to a change in intake air temperature or pressure, under selected conditions. An amount of exhaust gas recirculated to an engine intake is adjusted differently based on whether the humidity sensor is degraded or functional.

Claims

1. A method of operating an engine including a humidity sensor, comprising,

indicating humidity sensor degradation based on each of a change in an intake air relative humidity and temperature over a duration since an engine cold-start, the indication including indicating humidity sensor degradation responsive to a ratio of the change in humidity to the change in temperature, over the duration, being lower than a threshold.

2. The method of claim 1, wherein the relative humidity is estimated by the humidity sensor, and wherein the temperature is estimated by a temperature sensor, each of the humidity sensor and the temperature sensor positioned in an engine intake, downstream of a first throttle valve.

3. The method of claim 1, wherein the indication includes setting a diagnostic code.

4. The method of claim 1, wherein the duration is based on an exhaust catalyst temperature.

5. The method of claim 4, wherein the duration is increased as a difference between the exhaust catalyst temperature and a threshold temperature increases.

6. The method of claim 1, wherein the engine includes an engine intake, an engine exhaust, an EGR loop coupled between the engine intake and the engine exhaust, and wherein an EGR flow through the EGR loop is adjusted based on the indication of degradation.

7. The method of claim 1, wherein the adjustment includes adjusting EGR flow based on an output of the humidity sensor when the humidity sensor is not degraded, and adjusting the EGR flow based on a maximum humidity assumption when the humidity sensor is degraded.

8. A method of operating an engine including a humidity sensor and a temperature sensor in an engine intake, comprising,

during an engine cold-start condition,

estimating each of an intake air temperature and relative humidity over a duration since the cold-start;

indicating humidity sensor degradation based on a change in the humidity relative to a change in the temperature over the duration; and

adjusting an amount of exhaust gas recirculated from an engine exhaust to the engine intake based on the indication of humidity sensor degradation.

9. The method of claim 8, wherein the indication includes indicating degradation if a ratio of the change in humidity to the change in temperature is lower than a threshold and/or if a difference in the change in humidity to the change in pressure is higher than a threshold.

10. The method of claim 8, wherein the duration is based on an exhaust catalyst temperature, the duration increased as a difference between the exhaust catalyst temperature and a threshold temperature increases.

11. The method of claim 9, wherein the engine cold-start condition includes the exhaust catalyst temperature being below a light-off temperature.

12. The method of claim 10, wherein exhaust gas is recirculated from the engine exhaust to the engine intake via an EGR loop including an EGR valve, and wherein adjusting the amount of exhaust gas recirculated includes adjusting a position of the EGR valve.

13. The method of claim 12, wherein the adjustment includes,

adjusting the position of the EGR valve based on an output of the humidity sensor if the humidity sensor is not degraded;

and

adjusting the position of the EGR valve based on a maximum humidity if the humidity sensor is degraded, the maximum humidity calculated based on engine operating conditions.

14. An engine system, comprising:

first and second parallel intake passages, each including a turbocharger compressor;

first and second parallel exhaust passages, each including a turbocharger turbine;

a humidity sensor and a temperature sensor, each positioned only in the first passage; and

a controller configured with instructions for indicating humidity sensor degradation responsive to a humidity change relative to a temperature change over a duration since an engine cold-start.

15. The system of claim 14, further comprising,

a first low-pressure EGR loop for recirculating at least some exhaust gas from the first parallel exhaust passage, downstream of the turbine, to the first parallel intake passage, upstream of the compressor;

a second low-pressure EGR loop for recirculating at least some exhaust gas from the second parallel exhaust passage, downstream of the turbine, to the second parallel intake passage, upstream of the compressor;

a first high-pressure EGR loop for recirculating at least some exhaust gas from the first parallel exhaust passage, upstream of the turbine, to the first parallel intake passage, downstream of the compressor; and

a second high-pressure EGR loop for recirculating at least some exhaust gas from the second parallel exhaust passage, upstream of the turbine, to the second parallel intake passage, downstream of the compressor.

16. The system of claim 15, wherein the indication includes indicating sensor degradation responsive to the humidity change estimated by the humidity sensor being disproportionate to the temperature change estimated by the temperature sensor over the duration since the engine cold-start.

17. The system of claim 16, wherein the controller is further configured to,

recirculate a first amount of exhaust gas through the first and second low-pressure EGR loops in response to an indication of no humidity sensor degradation, the first amount based on a humidity output of the humidity sensor;

and

recirculate a second, different amount of exhaust gas through the first and second low-pressure EGR loops in response to the indication of humidity sensor degradation, the second amount based on a maximum humidity assumption.

18. The system of claim 16, further comprising an exhaust catalyst, wherein the duration is based on a temperature of the exhaust catalyst, the duration increased as a difference between the temperature of the exhaust catalyst and a threshold temperature increases.