Vehicle windshield and wiper with rain sensor

• US 4,827,198 A
• Filed: 02/09/1988
• Issued: 05/02/1989
• Est. Priority Date: 02/09/1988
• Status: Expired due to Term

• Current Assignee: ITT Automotive Electrical Systems, Inc. (ITT, Inc.)
• Original Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Mueller, Donald L., Nyberg, Glen A.
• Primary Examiner(s): Ro, Bentsu
• Application Number:
  US07/159,533
• Time in Patent Office: 448 Days
• Field of Search: 318/443, 318/444, 318/483, 318/DIG. 2, 15/250 C, 15/250.12
• US Class Current: 318/483
• 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: B32B 17/10761 containing vinyl acetal
• 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 1/0829 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: Y10S 15/15 Moisture responsive
• CPC Class Codes: Y10S 318/02 Windshield wiper controls

Abstract

A pair of outer conducting members on the outside of a windshield are separated by a long common insulating border defining a border resistance in parallel with a first capacitance. Each of the outer conducting members is capacitively coupled through a layer of the windshield to an inner conducting member to form coupling capacitances in series with the combination of the border resistance and first capacitance. The preceding elements form a timing circuit for an oscillator, the timing circuit having an equivalent capacitance varying with the border resistance. When water droplets bridge the border of the outer conducting members, the border resistance decreases from infinity to change the equivalent capacitance of the timing circuit and thus the frequency of the oscillator circuit; and this change is detected to modify wiper operation.

Claims

1. A motor vehicle windshield and wiper system comprising:

a windshield having at least one glass layer;

a wiper system having a blade on the outside of the windshield and drive means activatable to drive the blade in a predetermined pattern across a designated area of the windshield;

first and second outer conducting members on the outside of the windshield within the designated area, said first and second outer conducting members being slightly separated along a long common border to define a border resistance in parallel with a first capacitance therebetween, the border resistance being essentially infinite when dry but decreasing with water bridging the border;

first and second inner conducting members adjacent the first and second outer conducting members, respectively, and separated therefrom by at least the glass layer of the windshield, the first inner and outer conducting members being effective to define a second capacitance therebetween and the second inner and outer conducting members being effective to define a third capacitance therebetween in electrical series with the first and second capacitances;

electrical oscillator circuit means including a timing circuit comprising the second, first and third capacitances in series, with the infinite resistance across the first capacitance, to form an equivalent capacitance, as determined by charging and discharging current therethrough, the equivalent capacitance varying with change in the border resistance, the electrical oscillator circuit means having a frequency of oscillation dependent on the equivalent capacitance of the timing circuit; and

additional circuit means responsive to the frequency of the electrical oscillator circuit means to produce a first mode of wiper operation when the common border is dry and a second mode of wiper operation when the common border is bridged by water.

2. The motor vehicle windshield and wiper system of claim 1 in which the first and second outer conducting members are formed of an at least partially transparent coating on the outer surface of the windshield.

3. The motor vehicle windshield and wiper system of claim 1 in which the first and second outer conducting members form a unique identifying logo defined by the long common border therebetween.

4. A motor vehicle windshield and wiper system comprising:

a windshield having at least one glass layer;

a wiper system having a blade on the outside of the windshield and drive means activatable to drive the blade in a predetermined pattern across a designated area of the windshield;

first and second outer conducting members on the outside of the windshield within the designated area, said first and second outer conducting members being made of semi-transparent tin oxide and being slightly separated along a long common border to define a border resistance in parallel with a first capacitance therebetween, the border resistance being essentially infinite when dry but decreasing with water bridging the border;

first and second inner conducting members adjacent the first and second outer conducting members, respectively, made of the same material and separated therefrom by at least the glass layer of the windshield, the first inner and outer conducting members being effective to define a second capacitance therebetween and the second inner and outer conducting members being effective to define a third capacitance therebetween in electrical series with the first and second capacitances;

electrical oscillator circuit means comprising a comparator having a fixed reference connected to one input, a timing circuit connected to the other input, the timing circuit comprising the second, first and third capacitances in series, with the infinite resistance across the first capacitance, to form an equivalent capacitance, as de by charging and discharging current therethrough, the electrical oscillator circuit means further comprising comparator switched current means effective to charge and discharge the equivalent capacitance at a frequency determined thereby and thus varying with change in the border resistance; and

additional circuit means responsive to the frequency of the electrical oscillator circuit means to produce a first mode of wiper operation when the common border is dry and a second mode of wiper operation when the common border is bridged by water.