Humidity sensor and engine system

• US 9,389,198 B2
• Filed: 04/18/2013
• Issued: 07/12/2016
• Est. Priority Date: 04/18/2013
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Pursifull, Ross Dykstra, Makki, Imad Hassan, Clark, Timothy Joseph, Uhrich, Michael James, Kumar, Pankaj
• Primary Examiner(s): Cronin, Stephen K
• Assistant Examiner(s): Scharpf, Susan E
• Application Number:
  US13/865,853
• Publication Number:
  US 20140316676A1
• Time in Patent Office: 1,181 Days
• Field of Search: 701/103, 701/102, 324/601, 123/406.11, 73/290.1, 73/290.2
• US Class Current: 1/1
• CPC Class Codes: F02D 2041/1472 the characteristics being a humidity or water content of the exhaust gases
• CPC Class Codes: F02D 2200/0418 Air humidity
• CPC Class Codes: F02D 41/0002 Controlling intake air
• 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: F02P 5/045 combined with electronic control of other engine functions, e.g. fuel injection in general F02D37/02
• CPC Class Codes: G01M 15/02 Details or accessories of testing apparatus
• CPC Class Codes: G01M 15/04 Testing internal-combustion engines
• CPC Class Codes: G01N 27/223 for determining moisture content, e.g. humidity rain detectors on vehicle windows B60S1/0825
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

Methods and systems are provided for an engine coupled capacitance-based humidity sensor. Degradation of the humidity sensor may be determined based on humidity readings while flowing gasses into an engine intake air downstream of the humidity sensor and upstream of a compressor change by less than a first threshold while pressure at the sensor changes greater then a second threshold. The variation in pressure can be changed by adjusting a throttle upstream and downstream of the compressor based on whether the humidity sensor is degraded or functional.

Claims

1. An engine method comprising,

responsive to ambient entry conditions, monitoring pressure and humidity sensor changes while flowing gasses into an engine air intake downstream of a humidity sensor and upstream of a compressor,

in response to said monitored pressure and humidity sensor changes being less than respective thresholds, intrusively adjusting intake pressure and indicating humidity sensor degradation when humidity readings change by less than a first threshold while pressure at the sensor changes greater than a second threshold.

2. The method of claim 1, wherein flowing gasses includes flowing low-pressure EGR, and wherein the entry conditions include ambient air humidity.

3. The method of claim 1, wherein flowing gasses includes flowing low-pressure EGR and crankcase gasses.

4. The method of claim 1, wherein flowing gasses includes flowing crankcase gasses.

5. The method of claim 1, wherein the humidity sensor is a capacitance-based humidity sensor, the method further comprising determining whether a gain between a change in pressure and a change in capacitance is as expected based on whether capacitance changes less than the first threshold in the presence of pressure changes at the sensor greater than the second threshold, and from the gain indicate sensor degradation.

6. The method of claim 5, further comprising generating the pressure changes by adjusting a throttle upstream of the compressor.

7. The method of claim 6, further comprising adjusting the throttle upstream of the compressor in response to compressor surge while flowing the gasses.

8. The method of claim 5, further comprising generating the pressure changes by adjusting a compressor bypass valve, the bypass valve adjustment being responsive to compressor surge, and adjusting engine operating in response to the indication of degradation.

9. The method of claim 6, further comprising adjusting a throttle downstream of the compressor to compensate for the upstream throttle adjustment while flowing the gasses.

10. The method of claim 6, further comprising selecting a degree of throttle adjustment, the throttle adjusted while flowing the gasses, the selected degree being responsive to boost level.

11. The method of claim 10, wherein the degree of throttle adjustment generates a pressure variation while flowing the gasses greater than a threshold, the threshold increasing with increasing boost levels.

12. The method of claim 11, wherein indicating degradation includes setting a diagnostic code and generating a diagnostic message.

13. The method of claim 11, further comprising implementing default action in response to the indication, the default action including setting measured humidity to a lower threshold value, and adjusting spark timing, fuel injection, and boost control responsive to the lower threshold value independent of the humidity sensor reading.

14. A diagnostic method for a humidity sensor, comprising:

responsive to ambient air having a sufficiently high humidity, monitoring pressure and humidity sensor changes while flowing gasses into an engine air intake downstream while varying pressure at the sensor over a non-zero range, the humidity sensor positioned upstream of a compressor in an engine intake system; and

in response to said sensor readings not varying greater than a threshold over operating conditions where natural throttle motion generated sufficient pressure variation, intrusively adjusting intake pressure and indicating degradation of the humidity sensor when the indication of humidity changes by less than a threshold amount with the intrusive variation in pressure.

15. The method of claim 14, wherein the compressor is coupled in a turbocharger boosting engine intake air.

16. The method of claim 15, further comprising adjusting engine operation in response to the indication, and wherein the indicating includes setting a diagnostic code stored in memory.

17. The method of claim 16, wherein the humidity sensor includes a pair of parallel capacitive plates.

18. The method of claim 16, further comprising adjusting an air intake throttle upstream of the compressor to generate the variation in pressure.

19. A system, comprising:

an engine having an intake system with a compressor therein;

a throttle positioned in an intake upstream of the compressor;

a humidity sensor positioned in the intake between the throttle and the compressor; and

a controller with memory having non-transitory instructions therein, including instructions to indicate humidity sensor degradation when humidity readings of the sensor change by less than a first threshold while pressure at the sensor changes greater than a second threshold, the pressure changes generated by intrusive throttle adjustments, the intrusive throttle adjustments generated in response to previous monitoring of humidity sensor readings not changing sufficiently where natural throttle motion generated sufficient pressure variation.