Patent ID: 8708861

Claim:
An electric power tool, comprising: a motor as a drive power source; a speed reduction mechanism for transferring a rotational power of the motor at a reduced speed; and a reduction ratio changing unit for changing a reduction ratio of the speed reduction mechanism, wherein the speed reduction mechanism includes an axially slidable changeover member and a gear member, the changeover member being engaged with or disengaged from the gear member depending on an axial slide position thereof, wherein the reduction ratio changing unit includes a shift actuator for axially sliding the changeover member, a driving state detector unit for detecting a driving state of the motor, a slide position detector unit which detects a physical slide position of the changeover member and a control unit for starting up the shift actuator depending on a detection result of the driving state detector unit and for temporarily decreasing or increasing a rotational power of the motor depending on a detection result of the slide position detector unit, wherein the changeover member is allowed to slide to a target position when the changeover member is engaged with the gear member, and wherein the control unit changes at least one of a drive control of the motor and a drive control of the shift actuator when the detection result of the slide position detector unit indicates that the changeover member fails to slide to the target position when the shift actuator is driven.