Sealed Capacitive Rain Sensor

• US 20080265913A1
• Filed: 09/06/2006
• Published: 10/30/2008
• Est. Priority Date: 09/06/2005
• Status: Abandoned Application

• Current Assignee: Tamar Sensors Ltd.
• Original Assignee: Tamar Sensors Ltd.
• Inventors: Netzer, Yishay
• Application Number:
  US12/065,617
• Publication Number:
  US 20080265913A1
• Time in Patent Office: Days
• US Class Current: 324/669
• CPC Class Codes: B60S 1/0822 characterized by the arrangement or type of detection means
• CPC Class Codes: B60S 1/0825 Capacitive rain sensor

Abstract

A capacitive rain sensor for activating automotive window wipers includes: capacitive plates, electronic circuitry for sensing the capacitance between said plates, processing the sensed capacitance signal, and generating wipe commands. The capacitive plates are protected from water adsorption and condensation by means of a hermetic enclosure. The interconnection between the inside and outside of the enclosure is optionally implemented by means of conductors printed on the window. Wiper-induced and other parasitic signals are rejected by means of an adaptive filter Optional radiation sensor is utilized to suppress solar induced fast temperature variations. An optional far-field cancellation plate is utilized to minimize false wipes due to nearby objects.

Claims

1. A vehicular capacitive rain sensor deployed on an internal surface of a window, the sensor having a sensing region for detecting moisture on the external surface of the window for generating wipe commands applied to a wiper deployed for wiping the external surface, the sensor comprising:

(a) at least two electrodes disposed on said internal surface and constituting a capacitance, said at least two electrodes defining a sensing region on the external surface of the window within which the presence of water detectably affects said capacitance;

(b) a housing arrangement cooperating with the internal surface of the window to enclose said electrodes, at least part of said housing arrangement being implemented as an electrostatic shield for shielding said electrodes; and

(c) electrical interconnections passing into said housing arrangement;

wherein said housing arrangement is configured to hermetically seal said electrodes so as to make said capacitance substantially insensitive to moisture adsorption.

2. A capacitive rain sensor as in claim 1, further comprising electronic circuitry associated with said electrodes and configured to generate an output signal indicative of said capacitance.

3. A capacitive rain sensor as in claim 2, further comprising a processing system for generating wipe commands derived from said output signal;

4. A capacitive rain sensor as in claim 3, wherein said processing system is configured to provide a filter with a dynamic behavior that varies depending on said output signal.

5. A capacitive rain sensor as in claim 3, wherein said processing system is

(a) when the Wiper is not activated, said processing system filters said output signal to discard variation with a frequency of less than a first cut-on frequency;

and

(b) when the wiper is activated, said processing system filters said output signal to discard variation with a frequency of less than a second cut-on frequency, said second cut-on frequency being higher than said first cut-on frequency.

6. The sensor as in claim 1, wherein said electrical interconnections are implemented as printed conductors on said internal surface.

7. The sensor as in claim 1, wherein said housing arrangement is implemented primarily from conductive material so as to provide said electrostatic shield.

8. The capacitive rain sensor as in claim 3, further comprising a detector for detecting solar radiation, said processing system being responsive to an output from said detector when the wiper is not activated to prevent generation of a wipe command within a given time period after an abrupt increase in solar radiation.

9. The capacitive rain sensor as in claim 1, wherein said at least two electrodes are deposited on a surface of a flexible non-conductive layer configured for attachment to the internal surface of the window.

10. The capacitive rain sensor as in claim 9, wherein said at least two electrodes and said flexible non-conductive layer are substantially transparent.

11. The capacitive rain sensor as in claim 9, wherein said flexible non-conductive layer is coated with an adhesive for attachment to the internal surface of the window.

12. The capacitive rain sensor as in claim 1, wherein said at least two electrodes are substantially transparent.

13. The cap active rain sensor as in claim 1, wherein a first of said at least two electrodes is driven with a signal so as to generate a near electrostatic field at least in the sensing region and a far electrostatic field, the capacitive rain sensor further comprising a third electrode which is driven with an opposite signal and configured so as to generate a second far electrostatic field which opposes at least pad of said far electrostatic field of said first electrode.

14. A vehicular capacitive rain sensor deployed on an internal surface of a window, the sensor having a sensing region for detecting moisture on the external surface of the window for generating wipe commands applied to a wiper deployed for wiping the external surface, the sensor comprising:

(a) at least two electrodes disposed on said internal surface and constituting a capacitance, said at least two electrodes defining a sensing region on the external surface of the window within which the presence of water detectably affects said capacitance;

(b) a housing arrangement cooperating with the internal surface of the window to enclose said electrodes, at least part of said housing arrangement being implemented as an electrostatic shield for shielding said electrodes;

(c) electronic circuitry associated with said electrodes and configured to generate an output signal indicative of said capacitance; and

(d) a processing system for generating wipe commands derived from said output signal, wherein said processing system being configured such that;

(i) when the wiper is not activated, said processing system filters said output signal to discard variation with a frequency of less than a

(ii) when the wiper is activated, said processing system filters said output signal to discard variation with a frequency of less than a second cut-on frequency, said second cut-on frequency being higher than said first cut-on frequency.

15. A vehicular capacitive rain sensor deployed on an internal surface of a window, the sensor having a sensing region for detecting moisture on the external surface of the window for generating wipe commands applied to a wiper deployed for wiping the external surface, the sensor comprising:

(a) at least two electrodes disposed on said internal surface and constituting a capacitance, said at least two electrodes defining a sensing region on the external surface of the window within which the presence of water detectably affects said capacitance;

(b) a housing arrangement cooperating with the internal surface of the window to enclose said electrodes, at least part of said housing arrangement being implemented as an electrostatic shield for shielding said electrodes; and

(c) electronic circuitry associated with said electrodes and configured to generate an output signal indicative of said capacitance;

(d) a processing system for generating wipe commands derived from said output signal; and

(e) a detector for detecting solar radiation, said processing system being responsive to an output from said detector when the wiper is not activated to prevent generation of a wipe command within a given time period after an abrupt increase in solar radiation.

16. A vehicular capacitive rain sensor deployed on an internal surface of a window, the sensor having a sensing region for detecting moisture on the external surface of the Window for generating wipe commands applied to a wiper deployed for wiping the external surface, the sensor comprising:

(a) at least two electrodes disposed on said internal surface and constituting a capacitance, said at least two electrodes defining a sensing region on the external surface of the window within which the presence of water detectably affects said capacitance;

(b) a housing arrangement cooperating with the internal surface of the window to enclose said electrodes, at least part of said housing arrangement being implemented as an electrostatic shield for shielding said electrodes; and

wherein said at least two electrodes are deposited on a surface of a flexible non-conductive layer configured for attachment to the internal surface of the window.

17. The capacitive rain sensor as in claim 16, wherein said at least two electrodes and said flexible non-conductive layer are substantially transparent.

18. The capacitive rain sensor as in claim 16, wherein said flexible non-conductive layer is coated with an adhesive for attachment to the internal surface of the window.

19. A vehicular capacitive rain sensor deployed on an internal surface of a window, the sensor having a sensing region for detecting moisture on the external surface of the window for generating wipe commands applied to a wiper deployed for wiping the external surface, the sensor comprising:

(a) at least two electrodes disposed on said internal surface and constituting a capacitance, said at least two electrodes defining a sensing region on the external surface of the window within which the presence of water detectably affects said capacitance;

(b) a housing arrangement cooperating with the internal surface of the window to enclose said electrodes, at least part of said housing arrangement being implemented as an electrostatic shield for shielding said electrodes; and

wherein said at least two electrodes are substantially transparent.

20. A vehicular capacitive rain sensor deployed on an internal surface of a window, the sensor having a sensing region for detecting moisture on the external surface of the window for generating wipe commands applied to a wiper deployed for wiping the external surface, the sensor comprising:

(a) at least two electrodes disposed on said internal surface and constituting a sensing capacitance, said at least two electrodes defining a near electrostatic field sensing region on the external surface of the window within which the presence of water detectably affects said capacitance, said electrodes further forming a far electrostatic field;

(b) at least one compensation electrode configured for forming a compensatory far electrostatic field for selectively opposing at least part of said far electrosatic field of said sensing capacitance;

(c) a housing arrangement cooperating with the internal surface of the window to enclose said electrodes, at least part of said housing arrangement being implemented as an electrostatic shield for shielding said electrodes; and

(d) electronic circuitry associated with said electrodes and configured to generate an output signal indicative of said sensing capacitance; and

(e) a processing system for generating wipe commands derived from said output signal,

wherein said electronic circuitry drives a first of said at least two electrodes with a sensing signal and said compensation electrode with an opposite signal such that at least part of the far electrostatic field of said first electrode is reduced.