Temperature compensated windshield moisture detector

• US 20070044542A1
• Filed: 09/06/2006
• Published: 03/01/2007
• Est. Priority Date: 12/03/2002
• Status: Active Grant

• Current Assignee: Pittsburgh Glass Works LLC (LKQ Corporation)
• Original Assignee: PPG Industries Ohio Incorporated (Nouryon BV)
• Inventors: Voeltzel, Charles, Hawk, Allan, Chun, Shelby, Koram, Kwaku, Barguirdjian, Pascal, Haigron, Michel
• Granted Patent: US 7,296,461 B2
• Time in Patent Office: Days
• US Class Current: 73/73
• CPC Class Codes: B32B 17/10036 comprising two outer glass sheets
• CPC Class Codes: B32B 17/10174 Coatings of a metallic or dielectric material on a constituent layer of glass or polymer
• CPC Class Codes: B60S 1/0822 characterized by the arrangement or type of detection means
• CPC Class Codes: B60S 1/0829 Oscillator-resonator rain sensor
• CPC Class Codes: B60S 1/0877 at least part of the sensor being positioned between layers of the windshield
• CPC Class Codes: G01N 27/12 of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid , for detecting components in the fluid

Abstract

A moisture detection system includes an electrical conductor disposed on a surface of a substrate, an oscillator for outputting an oscillator signal at a predetermined amplitude and a predetermined frequency, and a resonator circuit coupled to the electrical conductor and responsive to the oscillator signal for outputting a resonator signal having an amplitude related to a resonant frequency of the electrical conductor. A filter circuit responsive to the resonator signal can output a rectified and filtered signal, and an analog-to-digital converter responsive to the rectified and filtered signal can output a digital signal related to the rectified and filtered signal. A sensor can be provided having a property that varies as a function of a temperature at or adjacent the electrical conductor. A controller can be responsive to the digital signal and the property of the sensor for causing another system to operate as a function thereof.

Claims

1. A moisture detection system comprising:

an electrical conductor disposed on a surface of a substrate and having a resonant frequency that varies as a function of an amount of moisture present adjacent the electrical conductor;

an oscillator which outputs an oscillator signal at a predetermined amplitude and a predetermined frequency;

a resonator circuit coupled to the electrical conductor and responsive to the oscillator signal for outputting a resonator signal having an amplitude related to the resonant frequency of the electrical conductor;

a filter circuit responsive to the resonator signal for outputting a rectified and filtered signal;

an analog-to-digital converter responsive to the rectified and filtered signal for outputting a digital signal related to the rectified and filtered signal;

a sensor having a property that varies as a function of a temperature at or adjacent the electrical conductor; and

a controller responsive to the digital signal and the property of the sensor for causing another system to operate as a function thereof.

2. The system of claim 1, wherein:

the other system is a wiper system that is responsive to the controller for adjusting a rate moisture is removed from adjacent the electrical conductor as a function of an amount of moisture present adjacent the electrical conductor and/or a rate moisture accumulates adjacent the electrical conductor.

3. The system of claim 1, wherein the substrate is a flexible substrate having either (i) a ground conductor disposed on the flexible substrate at least partially surrounding the electrical conductor or (ii) a conductive material disposed on a surface of the flexible substrate opposite the electrical conductor, said conductive material having a form that defines a faraday shield.

4. The system of claim 1, wherein:

the resonator circuit includes a capacitor connected between the electrical conductor and a reference voltage and a resistor connected between the oscillator and the electrical conductor side of the capacitor; and

/or

the filter circuit includes a diode connected to conduct current from the resonator toward the analog-to-digital converter and a capacitor connected between an end of the diode adjacent the analog-to-digital converter and the reference voltage.

5. A moisture detector system comprising:

means disposed on a substrate for conducting electrical current, the conducting means having a resonant frequency that changes as a function of moisture adjacent the conducting means;

an oscillator for outputting to the conducting means an oscillator signal having a predetermined frequency and a first amplitude;

means responsive to the oscillator signal for outputting a resonator signal having a second amplitude related to the resonant frequency of the conducting means, wherein the second amplitude is different than the first amplitude;

means having a property whose value varies as a function of a temperature at or adjacent the conducting means; and

means responsive to the resonator signal and the value of the property for outputting a control signal having a value related to the second amplitude of the resonator signal.

6. The moisture detector of claim 5, further including a wiper system responsive to the control signal for wiping moisture from adjacent the conducting means based on an amount of moisture adjacent the conducting means and/or a rate moisture accumulates adjacent the conducting means.

7. The moisture detector of claim 5, wherein:

the substrate is a flexible substrate that is coupled to a sheet; and

the conducting means has a resonant frequency that changes as a function of moisture on the sheet.

8. The moisture detector of claim 7, wherein the conducting means includes one or more lines of electrically conductive material disposed on the flexible substrate.

9. The moisture detector of claim 7, wherein the flexible substrate further includes (i) a ground conductor disposed on the flexible substrate at least partially surrounding the conducting means or (ii) a conductive material disposed on a surface of the flexible substrate opposite the conducting means, said conductive material having a form that defines a faraday shield.

10. A method of moisture detection comprising:

(a) providing a substrate having an electrical conductor disposed thereon;

(b) stimulating the electrical conductor with an oscillator signal in the absence of moisture adjacent the electrical conductor;

(c) detecting a value of a temperature dependent property acquired from a location at or adjacent the electrical conductor on or about the time step (b) is performed;

(d) determining a first amplitude of the electrical conductor to the stimulation in step (b) as a function of the value of the temperature dependent property detected in step (c);

(e) stimulating the electrical conductor with the oscillator signal when moisture is present adjacent the electrical conductor;

(f) detecting the value of the temperature dependent property on or about the time step (e) is performed;

(g) determining a second amplitude of the electrical conductor to the stimulation in step (e) as a function of the value of the temperature dependent property detected in step (f), wherein the second amplitude is different than the first amplitude due to a change in resonant frequency of the electrical conductor in response to the presence of moisture adjacent the electrical conductor; and

(h) determining a difference between the first amplitude and the second amplitude, wherein the difference is related to the amount of moisture present adjacent the electrical conductor.

11. The method of claim 10, wherein the detected temperature dependent property is physically or optically detected.

12. The method of claim 11, wherein the physically detected property is voltage, current or resistance.

13. The moisture detection system of claim 10, wherein the detected temperature dependent property is:

a potential output by a bimetallic junction acting as the temperature sensor;

a resistance of a thermistor or a conductor acting as the temperature sensor;

or

a signal output by an optical temperature sensor acting as the temperature sensor.

14. The method of claim 10, further including removing moisture from adjacent the electrical conductor at a rate related to the difference between the first amplitude and the second amplitude.

15. The method of claim 10, further including sandwiching the substrate between at least two sheets of glass.

16. The method of claim 15, further including providing shielding means on (i) the substrate and/or (ii) at least one of the sheets of glass.

17. A moisture detection system comprising:

a substrate;

an electrical conductor disposed on the substrate;

means for stimulating the electrical conductor with an oscillator signal;

means for determining a temperature at or adjacent the electrical conductor; and

means responsive to the oscillator signal, the electrical conductor and the determined temperature for determining temperature corrected changes in a resonant frequency of the electrical conductor in response to changes in an amount of moisture disposed adjacent the electrical conductor.

18. The system of claim 17, further including:

means for removing an accumulation of moisture on the sheet; and

means responsive to the determining means for controlling when the removing means removes the accumulation of moisture from the sheet.

19. A method of moisture detection comprising:

correcting a value of a signal generated in response to the presence of moisture on a substrate as a function of a temperature determined at or adjacent the substrate; and

controlling a system as a function of the corrected signal.

20. A method of moisture detection comprising:

generating a signal having a value related to an amount of moisture on a substrate;

combining the signal with a correction factor related to a temperature determined at or adjacent the substrate; and

controlling a system as a function of the combination.

21. A moisture detection system comprising:

a substrate;

a resistive conductor disposed on the substrate;

a source of DC power;

means for generating an AC oscillator signal;

means for applying the DC power and the AC oscillator signal one at a time to the resistive conductor; and

means responsive to the application of the oscillator signal to the resistive conductor for determining changes in a resonant frequency of the resistive conductor in response to changes in an amount of moisture disposed adjacent the resistive conductor.

22. The system of claim 21, further including:

means for removing an accumulation of moisture on the sheet; and

means responsive to the determining means for controlling when the removing means removes the accumulation of moisture from the sheet.

23. A method of moisture detection comprising:

(a) connecting a resistive conductor to a source of DC power;

(b) disconnecting the resistive conductor from the source of DC power;

(c) connecting the resistive conductor to an AC signal source;

(d) in response to the application of the AC signal source, determining a change in a resonant frequency of the resistive conductor related to a change in an amount of moisture adjacent the resistive conductor; and

(e) removing moisture from adjacent the resistive conductor as a function of the change in the resonant frequency thereof.

24. The method of claim 23, wherein step (e) includes removing moisture from adjacent the resistive conductor as a function of a temperature adjacent the resistive conductor.