Method and System for Humidity Sensor Diagnostics

• US 20120227714A1
• Filed: 03/10/2011
• Published: 09/13/2012
• 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, Kerns, James Michael, Jentz, Robert Roy, Clark, Timothy Joseph, Uhrich, Michael James, Soltis, Richard E.
• Granted Patent: US 9,163,588 B2
• Time in Patent Office: Days
• US Class Current: 123/568.19
• CPC Class Codes: F02D 2200/0418 Air humidity
• CPC Class Codes: F02D 41/0002 Controlling intake air
• CPC Class Codes: F02D 41/005 according to engine operating conditions
• CPC Class Codes: F02D 41/0077 Control of the EGR valve or actuator, e.g. duty cycle, closed loop control of position EGR valve position sensor F02M26/48
• CPC Class Codes: F02D 41/222 relating to the failure of sensors or parameter detection devices
• 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 26/14 in relation to the exhaust system
• CPC Class Codes: F02M 26/17 in relation to the intake system
• CPC Class Codes: F02M 26/24 with two or more coolers
• CPC Class Codes: F02M 26/38 with two or more EGR valves disposed in parallel
• CPC Class Codes: F02M 26/45 Sensors specially adapted for EGR systems
• CPC Class Codes: F02M 26/47 the characteristics being temperatures, pressures or flow rates
• CPC Class Codes: Y02T 10/40 Engine management systems

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 positioned downstream of an EGR throttle valve, comprising,

closing the EGR throttle valve;

and

indicating humidity sensor degradation based on each of a change in intake air relative humidity and pressure responsive to the EGR throttle valve closing.

2. The method of claim 1, further comprising, opening an air intake throttle valve concurrent to the EGR throttle valve closing to compensate for torque disturbances, the air intake throttle valve positioned downstream of the EGR throttle valve.

3. The method of claim 1, wherein the relative humidity is estimated by the humidity sensor, and wherein the pressure is estimated by a pressure sensor coupled downstream of the EGR throttle valve.

4. The method of claim 1, wherein the indication includes indicating humidity sensor degradation responsive to a ratio of the change in humidity to the change in pressure being lower than a threshold.

5. The method of claim 1, wherein the indication includes indicating humidity sensor degradation responsive to a difference between the change in humidity and the change in pressure being higher than a threshold.

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

7. The method of claim 1, wherein closing the EGR throttle valve includes partially closing the EGR throttle valve.

8. The method of claim 1, further comprising, in response to the indication of degradation, adjusting an EGR flow to the engine based on a maximum humidity assumption.

9. A method of operating an engine including a humidity sensor in an engine intake, comprising,

closing a first throttle valve while concurrently opening a second throttle valve, the first throttle valve positioned upstream of the humidity sensor, the second throttle valve positioned downstream of the humidity sensor;

indicating humidity sensor degradation responsive to a resulting change in relative humidity; and

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

10. The method of claim 9, wherein the indication includes indicating humidity sensor degradation based on a comparison of the resulting change in relative humidity and a change in intake air pressure responsive to the EGR throttle valve closing, the change in intake air pressure estimated by a pressure sensor positioned downstream of the first throttle valve.

11. The method of claim 10, wherein indicating humidity sensor degradation based on the comparison includes indicating humidity sensor degradation if a ratio of the change in humidity to the change in pressure 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.

12. The method of claim 9, wherein the adjustment includes adjusting the amount of exhaust gas recirculated based on an output of the humidity sensor if the humidity sensor is not degraded, and adjusting the amount of exhaust gas recirculated based on a maximum humidity if the humidity sensor is degraded, the maximum humidity calculated based on engine operating conditions.

13. The method of claim 12, 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.

14. The method of claim 9, wherein the engine includes first and second parallel intake passages, and wherein the humidity sensor is positioned in only one of the first and second parallel intake passages.

15. An engine system, comprising:

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

a first throttle valve positioned upstream of the first and second passages;

a second throttle valve positioned downstream of the first and second passage;

a humidity sensor positioned only in the first passage; and

a controller with instructions for concurrently closing the first throttle valve, opening the second throttle valve, and indicating sensor degradation responsive to a resulting humidity change.

16. The system of claim 15, further comprising first and second parallel exhaust passages, each including a turbine, wherein the turbine in each of the first and second parallel exhaust passages drives the compressor in each of the first and second parallel intake passages, respectively.

17. The system of claim 16, 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.

18. The system of claim 17, further comprising, a pressure sensor positioned only in the first intake passage, each of the pressure sensor and the humidity sensor positioned downstream of the first throttle valve.

19. The system of claim 18, wherein indicating sensor degradation responsive to a resulting humidity change includes indicating sensor degradation responsive to, following the first throttle valve closing, the humidity change estimated by the humidity sensor being disproportionate to a pressure change estimated by the pressure sensor.

20. The system of claim 19, 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 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 sensor degradation, the second amount based on a maximum humidity assumption.