Humidity sensor and engine system

Patent metadata

Field	Value
Publication number	US-9618470-B2
Application number	US-201313865877-A
Country	US
Kind code	B2
Filing date	Apr 18, 2013
Priority date	Apr 18, 2013
Publication date	Apr 11, 2017
Grant date	Apr 11, 2017

Abstract

Methods and systems are provided for an engine coupled temperature-based humidity sensor. Degradation of the humidity sensor may be determined while flowing gasses into an engine intake air downstream of a humidity sensor and upstream of a compressor, indicating humidity sensor degradation when relative humidity readings change by less than a threshold while temperature at the sensor changes greater than a second threshold.

First claim

The invention claimed is:

1. An engine method comprising,
while flowing gasses into an engine intake air downstream of a humidity sensor and upstream of a compressor, indicating humidity sensor degradation when relative humidity readings increase by less than a first threshold while air temperature at the humidity sensor increases greater than a second threshold.

2. The method of claim 1 , wherein flowing gasses includes flowing low-pressure EGR.

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

4. The method of claim 1 , further comprising flowing crankcase gasses into the engine intake air upstream of the humidity sensor.

5. The method of claim 1 , wherein relative and specific humidity are lower than a third threshold.

6. The method of claim 1 , wherein the humidity sensor is a temperature-based humidity sensor.

7. The method of claim 6 , further comprising generating an air temperature change during a cold engine start.

8. The method of claim 7 , wherein an increase in underhood temperature generates an increase in intake air temperature from below to above ambient air.

9. The method of claim 6 , further comprising generating an air temperature change by adjusting a heater contained in the humidity sensor, the heater being located upstream of a capacitance sensor contained in the humidity sensor.

10. The method of claim 9 , wherein the heater adjustment generates an increase in air temperature greater than a threshold, the air temperature being measured by an air temperature sensor contained in the humidity sensor and located downstream of the capacitance sensor.

11. The method of claim 10 , wherein indicating degradation includes setting a diagnostic code and generating a diagnostic message, and wherein the heater is spaced away from the capacitance sensor.

12. The method of claim 11 , further comprising implementing default action in response to the indication, the default action including setting measured relative 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.

13. A diagnostic method for a humidity sensor, comprising:
generating an indication of humidity from the humidity sensor while varying air temperature at the sensor, the humidity sensor positioned upstream of a compressor in an engine intake system; and indicating degradation of the humidity sensor when the indication of humidity changes by less than a threshold amount with the variation in air temperature;
where the humidity sensor comprises a capacitance sensor and a heater, the heater positioned upstream of the capacitance sensor.

14. The method of claim 13 , wherein the compressor is coupled in a turbocharger boosting engine intake air, wherein the engine intake system includes an upstream throttle located in the intake system upstream of the compressor and a downstream throttle located in the intake system downstream of the compressor.

15. The method of claim 14 , further comprising adjusting engine operation in response to the indication, and wherein the indicating includes setting a diagnostic code stored in memory.

16. The method of claim 15 , wherein the humidity sensor includes a temperature sensor located downstream of the capacitance sensor, and the humidity sensor indicates relative humidity.

17. The method of claim 15 , further comprising adjusting the heater in the humidity sensor to generate the variation in air temperature, the variation in air temperature being generated upstream of the capacitance sensor.

18. A system, comprising:
an engine having an intake system with a compressor therein;
a first throttle positioned in an intake upstream of the compressor;
a second throttle positioned in the intake downstream of the compressor;
a humidity sensor positioned in the intake between the first throttle and the compressor, the humidity sensor comprising a heater, a pair of capacitive plates, and a temperature sensor, the heater being located upstream of the capacitive plates; and
a controller with memory having non-transitory instructions therein, including instructions to indicate humidity sensor degradation when relative humidity readings of the humidity sensor increase by less than a first threshold while air temperature at the temperature sensor increases greater than a second threshold.

19. The method of claim 14 , further comprising adjusting the upstream throttle and the downstream throttle while the variation in air temperature is generated.

20. The system of claim 18 , wherein the heater is spaced away upstream from the pair of capacitive plates.

Assignees

• Ford Global Tech Llc

Inventors

• Uhrich Michael James
• Kim Yong-Wha
• Pursifull Ross Dykstra

Classifications

• G01N27/223 Primary

  for determining moisture content, e.g. humidity (rain detectors on vehicle windows B60S1/0825) · CPC title

• G01N27/14

  of an electrically-heated body in dependence upon change of temperature · CPC title

• F02P5/045

  combined with electronic control of other engine functions, e.g. fuel injection (in general F02D37/02) · CPC title

• F02P5/152

  dependent on pinking (detecting or indicating knocks in internal-combustion engines G01L23/22) · CPC title