Spot welding apparatus

1. A spot welding apparatus comprising:

a first welding electrode;

a pressing force actuator for causing a second welding electrode facing the first welding electrode to move between a pressing force applying position, where the second welding electrode holds a workpiece together with the first welding electrode such that the first welding electrode and the second welding electrode apply pressing forces to the workpiece, and a retracted position away from the workpiece;

a control pressing force applying actuator for causing a control pressing force applying unit to move between a control pressing force applying position, where the control pressing force applying unit is located adjacent to the first welding electrode or the second welding electrode and comes into contact with the workpiece so as to apply a control pressing force to the workpiece, and a retracted position away from the workpiece;

a welding transformer serving as a power source to apply a current between the first welding electrode and the second welding electrode; and

a support bracket supported by a welding robot;

wherein the pressing force actuator is arranged at a front side of the support bracket, while the control pressing force applying actuator and the welding transformer are linearly arranged at a rear side of the pressing force actuator.

2. The spot welding apparatus according to claim 1 ,

wherein the control pressing force applying actuator includes a servomotor comprising a hollow motor, and a linear motion unit having a ball screw attached to an end of a hollow rotor and a rod screwed onto the ball screw,

wherein a control pressing force applying arm is attached to the rod, the control pressing force applying arm including:

a distal end portion bent toward the first welding electrode and the second welding electrode; and

a movable receiving unit connected to the distal end portion and extending toward the first welding electrode and the second welding electrode,

wherein the control pressing force applying unit is connected to a distal end of the movable receiving unit.

3. The spot welding apparatus according to claim 1 , wherein the control pressing force applying unit applies the control pressing force at the front side of the support bracket.

4. The spot welding apparatus according to claim 1 , wherein the welding transformer, the control pressing force applying actuator, and the pressing force actuator are sequentially arranged from the rear side of the pressing force actuator to the front side of the support bracket.

5. The spot welding apparatus according to claim 1 ,

wherein the control pressing force applying actuator includes a servomotor comprising a hollow motor, and a linear motion unit having a ball screw attached to an end of a hollow rotor and a rod screwed onto the ball screw; and

wherein a control pressing force applying arm having the control pressing force applying unit is connected to the rod.

6. The spot welding apparatus according to claim 5 , wherein the servomotor and the linear motion unit are coaxially aligned with each other.

7. The spot welding apparatus according to claim 5 , wherein the control pressing force applying arm includes:

a distal end portion bent toward the first welding electrode and the second welding electrode; and

a movable receiving unit connected to the distal end portion and extending toward the first welding electrode and the second welding electrode.

8. The spot welding apparatus according to claim 1 ,

wherein the support bracket includes a base supported by the welding robot, and a pair of sides facing each other and extending from the base;

wherein the pressing force actuator is disposed on distal ends of the sides with a bracket interposed therebetween; and

wherein the control pressing force applying actuator and the welding transformer are disposed between the sides.

9. The spot welding apparatus according to claim 8 ,

wherein the control pressing force applying actuator includes a servomotor comprising a hollow motor, and a linear motion unit having a ball screw attached to an end of a hollow rotor and a rod screwed onto the ball screw,

wherein a control pressing force applying arm is attached to the rod, the control pressing force applying arm including:

a distal end portion bent toward the first welding electrode and the second welding electrode; and

a movable receiving unit connected to the distal end portion and extending toward the first welding electrode and the second welding electrode,

wherein the control pressing force applying unit is connected to a distal end of the movable receiving unit.

10. The spot welding apparatus according to claim 8 , wherein the welding transformer is disposed between a center of the pair of sides.

11. The spot welding apparatus according to claim 8 ,

wherein the control pressing force applying actuator includes a servomotor having a hollow motor, and a linear motion unit having a ball screw attached to an end of a hollow rotor and a rod screwed onto the ball screw; and

wherein a control pressing force applying arm having the control pressing force applying unit is connected to the rod.

12. The spot welding apparatus according to claim 11 , wherein the servomotor and the linear motion unit are coaxially aligned with each other.

13. The spot welding apparatus according to claim 11 , wherein the control pressing force applying arm includes:

a distal end portion bent toward the first welding electrode and the second welding electrode; and

a movable receiving unit connected to the distal end portion and extending toward the first welding electrode and the second welding electrode.