Percussion driver drill, and a changeover mechanism for changing over a plurality of operating modes of an apparatus

A percussion driver drill, comprising:

• a main body housing to which a motor is attached;
• a planetary gear reduction mechanism assembled to the main body housing, the planetary gear reduction mechanism having an internal gear rotatably disposed therein, an input end capable of being mounted on the motor, and an output end from which a rotational force is transmissible to a spindle;
• a cam mechanism capable of applying percussing motion to the spindle in an axial direction thereof in interlocking relation to the spindle;
• a pressing mechanism capable of pressing the internal gear to fix the internal gear;
• a first changeover member capable of changing over an interlocked state of the cam mechanism with respect to the spindle, the first changeover member having a first changeover position and a second changeover position, wherein rotation and percussion are applied to the spindle in the first changeover position of the first changeover member, and only rotation is applied to the spindle in the second changeover position thereof;
• a second changeover member for torque adjustment, capable of adjusting a pressing force of the pressing mechanism to the internal gear, and adapted to be operated to allow the internal gear to idle so as to cut off the transmission of rotation to the spindle;
• and
• a restricting member capable of fixing the internal gear, the restricting member being provided so as to be movable between a fixing position for fixing the internal gear and a canceling position for canceling fixation of the internal gear,
• wherein the first changeover member has a third changeover position for causing the spindle to perform only rotation, and
• wherein, when the first changeover member is set in the first changeover position and the second changeover position, the restricting member is moved to the fixing position, and when the first changeover member is set in the third changeover position, the restricting member is moved to the canceling position.