Precipitation detector for arrangements which control windshield wipers and/or washers, and the like

• US 4,010,383 A
• Filed: 08/15/1975
• Issued: 03/01/1977
• Est. Priority Date: 08/17/1974
• Status: Expired due to Term

• Current Assignee: Gunter Grassmann
• Original Assignee: Gunter Grassmann
• Inventors: Grassmann, Gunter
• Primary Examiner(s): Hohauser, Herman J.
• Application Number:
  US05/605,176
• Time in Patent Office: 564 Days
• Field of Search: 307/118, 307/10 R, 307/116, 318/483, 318/443, 318/444 WW, 15/250.02, 15/250.12
• US Class Current: 307/118
• CPC Class Codes: B60S 1/0822 characterized by the arrangement or type of detection means
• CPC Class Codes: B60S 1/0851 Resistive rain sensor
• CPC Class Codes: G01N 27/048 for determining moisture content of the material

Abstract

The arrangement includes at least one upper and one lower cooperating sensor element, each comprised of a naked electrically conductive portion adjoining the corresponding portion of the other and together defining an interelectrode gap. The naked portions are exposed to precipitation. The naked conductive portion of the lower sensor element is comprised of upwardly projecting teeth having pointed ends closely adjoining the naked conductive portion of the upper sensor element. Water droplets occupying the interelectrode gap will tend not to cling to the electrically conductive portion of the lower sensor element because of the pointed configuration of the ends of the upwardly projecting teeth. A circuit is connected to the sensor elements and detects the existence of precipitation by detecting the interelectrode gap resistance changes which result when the interelectrode gap is occupied by water droplets, and the like, and in response to such detection generates a control signal for the windshield wiper motor and/or the windshield washer motor.

Claims

1. In an arrangement for controlling the operation of a windshield wiper motor on a vehicle, in combination, at least one upper and one cooperating lower sensor element, each sensor element being comprised of a naked electrically conductive portion which adjoins the naked electrically conductive portion of the other sensor element of the pair of sensor elements to define an interelectrode gap, the naked electrically conductive portions being exposed to precipitation, the space between the electrically conductive portion of the upper sensor element and that of the lower sensor element being empty both between such conductive portions and also rearwardly of the interelectrode gap, so that precipitation bridging the interelectrode gap will not be supported from behind against the force of oncoming wind and thus not tend to become protractedly caught in the gap, the lower sensor element being of comb-like configuration and the naked electrically conductive portion of the lower sensor element comprising upwardly projecting comb teeth having pointed ends closely adjoining the naked electrically conductive portion of the upper sensor element, whereby water droplets bridging the interelectrode gap will tend not to cling to the electrically conductive portion of the lower sensor element because of the pointed configuration of the ends of the upwardly projecting comb teeth thereof;

and circuit means operative for detecting the existence of precipitation by detecting the interelectrode gap resistance changes resulting from the bridging of the interelectrode gap by precipitation and in response to such detection generating a control signal for the windshield wiper motor.

2. The arrangement defined in claim 1, wherein the upper sensor element is of generally bar-shaped configuration.

3. The arrangement defined in claim 2, wherein the upper sensor element is tapered knife-like in rearwards and downwards direction along the longitudinal edge thereof which adjoins the teeth of the lower sensor element.

4. The arrangement defined in claim 3, wherein the upper sensor element is tapered in rearwards and upwards direction along the upper longitudinal edge thereof.

5. The arrangement defined in claim 1, wherein the naked electrically conductive portion of the upper sensor element is comprised of downwardly projecting teeth having pointed ends located opposite respective ones of the upwardly projecting teeth of the lower sensor element.

6. The arrangement defined in claim 5, wherein each of the downwardly projecting teeth of the upper sensor element has a downwardly and rearwardly extending front catching surface extending to its pointed end.

7. The arrangement defined in claim 6, wherein each of the downwardly projecting teeth of the upper sensor element has a back taper located opposite to the respective front catching surface.

8. The arrangement defined in claim 1, wherein the lower sensor element is rearwardly offset relative to the upper sensor element by a distance corresponding at least approximately to the thickness of the teeth.

9. The arrangement defined in claim 1, wherein each upwardly projecting tooth of the lower sensor element at the rear side thereof has a knife-like taper.

10. The arrangement defined in claim 1, wherein each upwardly projecting tooth of the lower sensor element has a lateral chamfer extending downwards and rearwards from the pointed end of the tooth.

11. The arrangement defined in claim 1, the lower sensor element occupying a general plane, and the upwardly projecting teeth of the lower sensor element being inclined relative to the vertical and lying in the general plane.

12. The arrangement defined in claim 1, the sensor elements being mounted for pivotal movement.

13. The arrangement defined in claim 1, the upper and lower sensor elements forming a first sensor unit, and further including a second sensor unit comprised of at least one pair of sensor elements having naked electrically conductive portions together defining an interelectrode gap, the interelectrode gap of the second sensor unit being of different size from that of the first sensor unit, whereby to make possible differentiation between different forms of precipitation, said circuit means being connected to the electrically conductive portions of the second sensor unit and operative for detecting interelectrode gap resistance changes of the second sensor unit.

14. The arrangement defined in claim 13, wherein the interelectrode gap of one of the sensor units is a horizontal interelectrode gap whereas the interelectrode gap of the other of the sensor units is a vertical interelectrode gap.

15. The arrangement defined in claim 1, further including means for heating the naked electrically conductive portions to prevent the formation of ice thereon.

16. The arrangement defined in claim 1, the control signal constituting a first control signal, wherein the circuit meansincludes time-delay means for generating a second control signal subsequent to the first control signal after the elapse of a predetermined time interval corresponding to a plurality of operating cycles of the windshield wiper motor.

17. The arrangement defined in claim 1, the circuit means further including means for generating a windshield washer activating signal in response to the detection of an interelectrode gap resistance change indicative of precipitation prior to the generation of the control signal, whereby to assure that the windshield is sufficiently wet prior to commencement of wiping to prevent dry wiping or smearing of the windshield in the event of light drizzle.

18. The arrangement defined in claim 1, the upper and lower sensor elements together forming a first sensor unit, further including an additional sensor unit configurated and dimensioned in correspondence to the first sensor unit, heating means for heating only the first sensor unit so as to permit the formation of ice on the additional sensor unit, and wherein the circuit means includes means for detecting the formation of ice by detecting the difference in the interelectrode gap resistances of the first and additional sensor units.

19. The arrangement defined in claim 1, wherein each of the upwardly projecting teeth of the lower sensor element is provided with a suction conduit.