Moisture sensor device and self-diagnosing method therefor

• US 20060186901A1
• Filed: 02/14/2006
• Published: 08/24/2006
• Est. Priority Date: 02/24/2005
• Status: Active Grant

• Current Assignee: DENSO Corporation, Nippon Soken, Inc.
• Original Assignee: DENSO Corporation, Nippon Soken, Inc.
• Inventors: Itakura, Toshikazu, Isogai, Toshiki
• Granted Patent: US 7,176,700 B2
• Time in Patent Office: Days
• US Class Current: 324/689
• CPC Class Codes: G01N 27/223 for determining moisture content, e.g. humidity rain detectors on vehicle windows B60S1/0825

Abstract

A moisture sensor device includes a sensor portion having a capacitance that is varied in accordance with surrounding humidity, a signal processor for processing a detection signal of the sensor portion and outputting the signal corresponding to the humidity, a heating portion for heating the sensor portion, and a controller for controlling heating of the heating portion so that the capacitance of the sensor portion is substantially equal to a value under predetermined humidity at least during a self-diagnosis period.

Claims

1. A moisture sensor device comprising:

a sensor portion having a capacitance that is varied in accordance with surrounding humidity;

a signal processor for processing a detection signal of the sensor portion and outputting the signal corresponding to the humidity;

a heating portion for heating the sensor portion; and

a controller for controlling heating of the heating portion so that the capacitance of the sensor portion is substantially equal to a value under predetermined humidity at least during a self-diagnosis period.

2. The moisture sensor device according to claim 1, wherein the predetermined humidity is substantially equal to 0%RH.

3. The moisture sensor device according to claim 1, wherein:

the sensor portion comprises a substrate, a pair of detection electrodes disposed on the surface of the substrate so as to be spaced from each other and face each other, a detector that is provided on the substrate so as to cover the gap between the detection electrodes and whose relative permittivity is varied in accordance with moisture, and a reference capacitance portion that is provided on the same plane as the detection electrodes and has a pair of reference electrodes having substantially the same construction as the detection electrodes;

the signal processor is equipped with a switched capacitor type C-V converter for converting the capacitance difference between the capacitance value of the detector and the capacitance value of the reference capacitance portion to the corresponding voltage; and

the heating portion comprises a heating element provided on the substrate.

4. The moisture sensor device according to claim 3, wherein the substrate comprises a semiconductor substrate, the signal processor is provided on the semiconductor substrate, and the heating element is constructed as a part of the signal processor.

5. The moisture sensor device according to claim 3, wherein the heating element comprises a resistor as a heater electrode that is supplied with current to generate heat.

6. The moisture sensor device according to claim 5, wherein the resistor is provided below the detection electrodes and the reference electrodes through an insulating layer.

7. The moisture sensor device according to claim 5, wherein the resistor is provided on the moisture sensitive film.

8. The moisture sensor device according to claim 7, wherein the resistor has moisture permeability.

9. The moisture sensor device according to claim 6, wherein the resistor has substantially the same width as facing portions of the detection electrodes and the reference electrodes, and are provided in connection with the facing portions.

10. The moisture sensor device according to claim 5, the resistor is provided on the same plane as the detection electrodes and the reference electrodes.

11. The moisture sensor device according to claim 10, wherein the resistor is provided between the pair of detection electrodes and between the pair of reference electrodes.

12. The moisture sensor device according to claim 4, wherein the heating element comprises at least one of a transistor and a diode.

13. The moisture sensor device according to claim 3, further comprising protection film formed on the substrate so as to cover the detection electrodes and the reference electrodes, wherein the moisture sensitive film is provided on the protection film.

14. The moisture sensor device according to claim 4, wherein the heating element comprises a resistor as a heater electrode that is supplied with current to generate heat.

15. A self-diagnosing method for a moisture sensor device comprising:

varying a capacitance of a sensor portion in accordance with surrounding humidity; and

processing a detection signal of the sensor portion by a signal processor and outputting the signal corresponding to the humidity,

wherein the varying of the capacitance of the sensor portion further comprises heating the sensor portion so that the capacitance of the sensor portion is substantially equal to a value under predetermined humidity, to thereby carrying out the self-diagnosis.

16. The self-diagnosing method according to claim 15, wherein the predetermined humidity is substantially equal to 0%RH.

17. A moisture sensor device comprising:

a sensor portion having a capacitance that varies in accordance with surrounding humidity;

a signal processor for processing a detection signal of the sensor portion and outputting the signal corresponding to the humidity; and

a heating portion for heating the sensor portion so that the capacitance of the sensor portion is substantially equal to a value under predetermined humidity at least during a self-diagnosis period.