Friction stir spot joining device

A friction stir spot joining device for softening and stirring an object to be joined by spot joining through frictional heat generated by rotation of a pin, said friction stir spot joining device comprising:

• a fixed arm;
• a friction stir spot joining device body connected to the fixed arm and having incorporated therein a stirring shaft supported by bearings and having the pin at a tip end and a hole at the center thereof through which a screw shaft is housed from the rear, a stirring motor for rotating the stirring shaft, a power transmission mechanism disposed between the stirring shaft and the stirring motor and rails of a linear motion guide provided at a bottom plate thereof;
• and a pressure application motor fixed to a rear end of the friction stir spot joining device body;
• characterized in that the stirring motor, the stirring shaft and the power transmission mechanism are unitized to form a stirring unit, bearings of the linear motion guide are fixed to the stirring unit at a position immediately beneath the power transmission mechanism, a ball nut is fixed to a back face of the stirring unit, the friction stir spot joining device body is opened to form an opening at a rear upper portion thereof through which the stirring unit is caused to move inside thereof so that the stirring motor is exposed to the outside through the opening and the screw shaft connected to the pressure application motor is caused to screw with the ball nut fixed to the back face of the stirring unit so as to advance or retract the stirring unit by the pressure application motor.