| 摘要 |
PROBLEM TO BE SOLVED: To surely prevent the damage of a tip of an annular cutter by surely detecting an overload state in an electric drill device. SOLUTION: An IC control circuit 71 stops the output of a control signal S1, when detecting that an overload current Id of a drill motor 30 reaches a first threshold value, and turns off an electronic switch 53 to temporarily stop the driving to a feed motor 40. When it detects that the current further rises and reaches a second threshold value, the control circuit outputs a stop signal S2, turns on a phototransistor PT, turns off a transistor T, de-energizes relays Ra and R2, and stops the driving to the drill motor and the feed motor. The IC control device monitors a load current If of the feed motor as a drop voltage of a resistance 41, outputs a stop signal when reaching a prescribed level, and stops the driving to the drill motor and the fed motor. The current If changes dependent on a thrust load so that monitoring of the current can prevent floating of the device and the damage of the tip.
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