Method and device for detecting rain on a windshield

Abstract

In a method for detecting rain on a windshield, whose degree of wetting is determined with at least one sensor value, it is provided that the sensor value is determined piezoelectrically, wherein vibrations on the windshield are detected, which change depending on the degree of wetting or raindrops hitting the windshield. As a result, the entire windshield serves as a detection surface, thereby yielding a high accuracy.

1 . A method for detecting rain on a windshield, comprising
 detecting vibrations on the windshield, caused by rain, with a piezoelectric sensor, the vibrations being detected via at least one wiper blade of a windshield wiper system, and via a coupling between the at least one wiper blade and the windshield,   determining a sensor value from the output of the piezoelectric sensor, which depends on the degree of wetting or raindrops hitting the windshield,   comparing the sensor value with known vibration profiles, and   determining the environmental condition on the windshield, caused by the rain, from said comparing.   
     
     
         2 . The method according to  claim 1 , wherein a distribution profile is established for the degree of wetting given at least two sensor values detected at locations spaced apart from each other. 
     
     
         3 . A device for detecting rain on a windshield, comprising:
 a windshield wiper system of the windshield,   at least one wiper blade included in said windshield wiper system,   at least one rain sensor included in the windshield wiper system includes at least one piezo element,   the at least one wiper blade includes one of the at least one rain sensors having the at least one piezo element, with the piezo element being coupled to the windshield through the wiper blade, and   an output of the piezo element is compared to stored vibration profiles to determine the environmental condition on the windshield caused by rain.   
     
     
         4 . The device according to  claim 3 , wherein the piezo element is designed as a piezoelectric line, which is attached along a length of the wiper blade, making the length of the wiper blade a rain sensor. 
     
     
         5 . A motor vehicle, including a device according to  claim 3 . 
     
     
         6 . The device according to  claim 3 , wherein the piezo element is heatable in cold weather. 
     
     
         7 . The device according to  claim 3 , wherein the determination of the environmental condition controls a headlight system. 
     
     
         8 . The device according to  claim 3 , wherein wear on the wiper blade is determined by the piezo element. 
     
     
         9 . The device according to  claim 3 , wherein movement of the wiper blade causes the at least one sensor to cover a large portion of the windshield.