| 摘要 |
PURPOSE:To prevent the damage and such of a wiper blade by starting only the operation of the first wiper motor after fixed delay time when the adhesion of a raindrop exceeds a preset threshold value. CONSTITUTION:The light of a light emitting diode 1 connected to a light emitting circuit 20 in a detection unit 10 repeats its total reflection on a glass surface 2 and is received by a photodiode 5, but if a raindrop adheres to the glass surface 2, the quantity of light reception is decreased. The light receiving current of the photodiode 5 cuts, amplifies, and rectifies noise components. Then the current is integrated, amplified, and input to the A/D converter circuit 50 of a microcomputer 40. Then a signal S that is digitally converted is compared with a preset threshold value S0 and a wiper operation signal OP is generated when S>S0. In this case, if the same signal OP is generated first, the signal OP is supplied to a wiper motor 80 after fixed delay time elapses. |
