Moisture sensor and method of fabrication thereof

• US 4,797,605 A
• Filed: 08/21/1987
• Issued: 01/10/1989
• Est. Priority Date: 08/21/1987
• Status: Expired due to Fees

• Current Assignee: Delco Electronics Corporation Kokomo In
• Original Assignee: Delco Electronics Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Palanisamy, Ponnusamy
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): Regan, Maura K.
• Application Number:
  US07/087,826
• Time in Patent Office: 508 Days
• Field of Search: 324/65 R, 318/643, 318/483, 318/DIG. 2, 15/250 C, 65/60.5
• US Class Current: 324/689
• CPC Class Codes: B60S 1/0822 characterized by the arrangement or type of detection means
• CPC Class Codes: B60S 1/0825 Capacitive rain sensor
• CPC Class Codes: B60S 1/0851 Resistive rain sensor
• CPC Class Codes: B60S 1/0892 Testing and production of rain sensors
• CPC Class Codes: G01N 27/048 for determining moisture content of the material
• CPC Class Codes: Y10S 318/02 Windshield wiper controls

Abstract

A moisture sensor consists of an array of spaced apart, highly abrasion-resistant electrodes disposed on the outside surface of the windshield of a vehicle. When moisture is present, the spaces between the electrodes are bridged by the water and the output impedance of the sensor significantly decreases. This signals the presence of moisture. The electrodes have particles of a conductive metal oxide, e.g., ruthenium oxide, dispersed within a glass matrix which is fused to the windshield glass. The electrodes are formulated as an ink including particles of the metal oxide, a glass frit, and an organic binder. The ink is silk screened onto the windshield in the desired electrode pattern. After drying of the ink, the glass frit is fused to the windshield during normal heating of the windshield to shape it in a known windshield shaping (sagging) process. Novel two layer sensor arrangements, providing even greater resistance to abrasion, are also described.

Claims

1. A moisture sensor comprising:

a first layer of conductive material formed on a portion of a windshield to be wiped by windshield blades, said layer being patterned to provide a plurality of spaced apart electrodes; and

a second, continuous layer of a material having a higher resistivity than the material of said first layer overlying said first layer and the portions of said windshield exposed between the electrodes of said first layer wherein

said first and second layers each comprises a material including a powder of conductive metal oxide dispersed within a glass matrix bonding said layers to each other and to said windshield.

2. The sensor of claim 1 in which the material of the second layer is more highly resistant to abrasion than the material of said first layer.