| 摘要 |
PROBLEM TO BE SOLVED: To automatically re-drive a drill motor which has automatically stopped when overloaded. SOLUTION: In a short-length-type electric drill with rotation axes of a motor and the drill different in direction, when a switch SW<SB>ON</SB>is turned on, a transistor Q<SB>71</SB>is turned on to form a self-retention circuit of the transistor of photocouplers PH<SB>2IN</SB>and PH<SB>2OUT</SB>, and a triac BCR is turned on via photocouplers PH<SB>1IN</SB>and PH<SB>1OUT</SB>to drive the drill motor 12. When being in overload, since a voltage V<SB>L1</SB>proportional to a voltage across a resistor R<SB>0</SB>exceeds a reference voltage V<SB>ref1</SB>, a transistor Q<SB>75</SB>is turned on and a current in a photo diode PH<SB>1IN</SB>is bypassed to have the BCR turned off. Since, as a result, no current flows to the resistor R<SB>0</SB>, the voltage V<SB>L1</SB>drops to make the output of an overload determination circuit zero. After a predetermined time, a discharge current from a capacitor C<SB>75</SB>stops flowing, thereby turning off the transistor Q<SB>75</SB>and re-lighting the photo diode PH<SB>1IN</SB>, and in turn the BCR is turned on and the drill motor is re-driven. COPYRIGHT: (C)2005,JPO&NCIPI
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