| 摘要 |
An electrical power tool may include an electric motor, a speed change device, and a battery pack. The speed change device is capable of changing a reduction ratio thereof and capable of automatically switching between a high speed low torque mode in which a high speed low torque is output and a low speed high torque mode in which a low speed high torque is output, based on an external torque applied to a spindle. A distance from the axis to a center of gravity of the battery pack and a mass of the battery pack are set such that an inertia moment around the axis is greater than a reaction around the axis that is produced when the high speed low torque mode is changed to the low speed high torque mode in the speed change device.
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