The induction wiper can sense the size of raindrops through the rain sensor, automatically adjust the wiper speed, and provide a good vision for the driver, thus greatly improving the convenience and safety of driving in rainy days.
A seemingly uncomplicated rain sensing automaticWiperThe R&D process of the system has also experienced difficulties.Since the United StatesGeneral Motors(G M) Since the rain sensing automatic wiper system was first used in the concept car LeSabre in 1951, there have been hundreds of patented technologies and countless unremitting attempts to constantly improve the rain sensing automatic wiper system, so that it can detect rain more effectively and make more accurate responses.[1]
working process
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When the sensor detects rain water fallingwindshieldThe rain on the front windshield of the car is removed, ensuring the driver's vision is unobstructed.At the same time, the command to automatically close the power windows and power sunroof of the vehicle shall be sent to avoid the interior of the vehicle being wet by rain.
working principle
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At present, the two mainstream sensors that are widely used are optical sensors and capacitive sensors.
Optical sensor
schematic diagram
It works according to the principle of light refraction.In the optical sensor, there is a light-emitting diode, which emits a cone light through the front windshield.When there is no rain on the windshield and it is dry, almost all the light will be reflected to an optical sensor;When it rains, there will be rain on the windshield, and part of the light will deviate, which will cause the total amount of light received by the sensor to change, thus detecting the existence of rain.The larger the area where the optical sensor can receive the reflected light, the more detailed the information will be obtained.The optical sensor is very accurate, and it is even possible to accurately determine the number of raindrops falling on the sensing area.
Capacitive transducer
It is mainly designed by taking advantage of the huge difference in the dielectric constant between water and glass, in which the dielectric constant of water is 80 and that of glass is 2.Usually, two parallel finger shaped metal plates are placed between the inner and outer layers of the windshield, and one group of finger shaped metal plates intersect incorrectly, but do not touch other finger shaped metal plates.When the windshield is dry, a dielectric is formed between the outer surface of the windshield and each group of finger shaped metal plates.When the windshield becomes wet, the dielectric constant of the windshield will change differently according to the amount of water in contact with the windshield.If the sensor is installed on the surface of the windshield or close to the lower surface of the windshield, it is beneficial to the work of the sensor, because such installation can make the sensor play its best sensitivity.The disadvantage is that installing the capacitive sensor on the outer surface of the windshield will cause the same problem as the resistance sensor, and its metal coating will soon be scraped off the windshield under the long-term operation of the wiper.[2]
