| 摘要 |
PROBLEM TO BE SOLVED: To urgently stop a shutter by easily and surely detecting an obstacle. SOLUTION: A detection gear 24 is separated from the external gear 34 of an electric motor 10 and directly meshed with a drive gear wheel 20 to detect its rotation after increasing its speed. The rotating state of the detection gear 24 is converted into pulses by a magnet 56 and reed switches 48 and 48, and the pulses are fed to a pulse row change detection means 46. The pulse row change detection means 46 counts pulse rows by a pulse counter 62, measures the pulse interval of the pulse rows by a pulse width measuring circuit 64, and compares the result by a pulse width comparison circuit 66 whether it exceeds a specified value or not. When the result exceeds the specified value, it detects that the abnormality of the shutter occurs by the obstacle and urgently stops the electric motor 10 by a motor control circuit 70. COPYRIGHT: (C)2005,JPO&NCIPI
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