Friction stir spot welding device and method for operating same

1. A friction stir spot welder adapted to weld workpieces through softening induced by friction heat, the workpieces including first and second workpieces stacked in the presence of a sealant applied to a region of contact between the first and second workpieces, the friction stir spot welder comprising:

a pin in the form of a solid circular cylinder;

a shoulder in the form of a hollow circular cylinder, the shoulder having an interior in which the pin is inserted;

a rotary actuator that rotates the pin and the shoulder about an axis coinciding with a central axis of the pin;

a clamp in the form of a hollow circular cylinder, the clamp having an interior in which the pin and the shoulder are inserted;

an advancement/withdrawal actuator that advances and withdraws the pin, the shoulder, and the clamp along the axis; and

a controller, the controller being configured to:

(B) drive the rotary actuator and the advancement/withdrawal actuator to cause the pin to press the workpieces for a first predetermined time while rotating;

(C) after performing the pressing (B), drive the rotary actuator and the advancement/withdrawal actuator to cause the pin and the shoulder to press the workpieces for a second predetermined time while rotating; and

(D) after performing the pressing (C), drive the rotary actuator and the advancement/withdrawal actuator to cause the pin and/or the shoulder to plunge into a weld region of the workpieces while rotating and stir the weld region to weld the workpieces together.

2. The friction stir spot welder according to claim 1 , wherein the controller is configured to, in the plunging (D):

(D 1 ) drive the rotary actuator and the advancement/withdrawal actuator to cause the pin to plunge into the weld region while rotating; and

(D 2 ) after the plunging (D 1 ), drive the rotary actuator and the advancement/withdrawal actuator to retract the pin out of the weld region and cause the shoulder to plunge into the weld region while rotating.

3. The friction stir spot welder according to claim 1 , wherein the controller is configured to, in the plunging (D):

(D 3 ) drive the rotary actuator and the advancement/withdrawal actuator to cause the shoulder to plunge into the weld region while rotating; and

(D 4 ) after the plunging (D 3 ), drive the rotary actuator and the advancement/withdrawal actuator to retract the shoulder out of the weld region and cause the pin to plunge into the weld region while rotating.

4. The friction stir spot welder according to claim 1 , wherein the controller is configured to, in the pressing (B), control the advancement/withdrawal actuator to place a distal end of the pin on an upper surface of the stack of the workpieces.

5. The friction stir spot welder according to claim 1 , wherein the controller is configured to, in the pressing (C), control the advancement/withdrawal actuator to place respective distal ends of the pin and the shoulder on an upper surface of the stack of the workpieces.

6. A method of operating a friction stir spot welder adapted to weld workpieces through softening induced by friction heat, the workpieces including first and second workpieces stacked in the presence of a sealant applied to a region of contact between the first and second workpieces, wherein the friction stir spot welder includes: a pin in the form of a solid circular cylinder; a shoulder in the form of a hollow circular cylinder, the shoulder having an interior in which the pin is inserted; a rotary actuator that rotates the pin and the shoulder about an axis coinciding with a central axis of the pin; a clamp in the form of a hollow circular cylinder, the clamp having an interior in which the pin and the shoulder are inserted; and an advancement/withdrawal actuator that advances and withdraws the pin, the shoulder, and the clamp along the axis, the method comprising:

(B) driving the rotary actuator and the advancement/withdrawal actuator to cause the pin to press the workpieces for a first predetermined time while rotating;

(C) after performing the pressing (B), driving the rotary actuator and the advancement/withdrawal actuator to cause the pin and the shoulder to press the workpieces for a second predetermined time while rotating; and

(D) after performing the pressing (C), driving the rotary actuator and the advancement/withdrawal actuator to cause the pin and/or the shoulder to plunge into a weld region of the workpieces while rotating and stir the weld region to weld the workpieces together.

7. The method according to claim 6 , wherein the plunging (D) includes:

(D 1 ) driving the rotary actuator and the advancement/withdrawal actuator to cause the pin to plunge into the weld region while rotating; and

(D 2 ) after the plunging (D 1 ), driving the rotary actuator and the advancement/withdrawal actuator to retract the pin out of the weld region and cause the shoulder to plunge into the weld region while rotating.

8. The method according to claim 6 , wherein the plunging (D) includes:

(D 3 ) driving the rotary actuator and the advancement/withdrawal actuator to cause the shoulder to plunge into the weld region while rotating; and

(D 4 ) after the plunging (D 3 ), driving the rotary actuator and the advancement/withdrawal actuator to retract the shoulder out of the weld region and cause the pin to plunge into the weld region while rotating.

9. The method according to claim 6 , wherein in the pressing (B), the advancement/withdrawal actuator is operated to place a distal end of the pin on an upper surface of the stack of the workpieces.

10. The method according to claim 6 , wherein in the pressing (C), the advancement/withdrawal actuator is operated to place respective distal ends of the pin and the shoulder on an upper surface of the stack of the workpieces.