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Electric power tool with gear reduction unit

  • US 7,980,320 B2
  • Filed: 12/24/2008
  • Issued: 07/19/2011
  • Est. Priority Date: 12/25/2007
  • Status: Expired due to Fees
First Claim
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1. An electric power tool comprising:

  • a motor as a driving power source;

    a reduction mechanism for transferring the rotating power of the motor, the reduction mechanism having two or more gear stages;

    a driving unit for transferring the rotating power of the reduction mechanism to a tip end tool;

    a bearing unit for rotatably supporting the driving unit;

    a housing for accommodating the motor, the reduction mechanism, the driving unit and the bearing unit within a main body portion thereof, the housing provided with a handle portion;

    a speed changing unit for changing a reduction ratio of the reduction mechanism, the speed changing unit being arranged in such a position as to allow an operator to operate the same from the outside of the housing;

    a power switch for turning on and off an electric power source of the motor;

    an operation detecting unit for detecting a reduction ratio changing operation performed by the speed changing unit; and

    a control unit for controlling the electric power supplied to the motor depending on the detected speed changing operation, wherein when the detected speed changing operation is to shift a low load operation to a high load operation, the control unit changes the output of the motor from a high-speed low-torque state to a low-speed high-torque state,wherein at least a part of the gears of the reduction mechanism are capable of changing the rotational speed of the driving unit by shifting, andwherein in response to the detected speed changing operation, the control unit adjusts the electric power supplied to the motor before the gears are shifted.

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