JP2658566B2 - Spot welding gun - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spot welding gun used in a welding assembly process of an automobile body.

2. Description of the Related Art As shown in FIG. 5 to FIG. 8, for example, when welding a lower end portion of a pillar portion P of a rear fender F and a side sill outer panel S in a welding assembly process of a body side B of an automobile. Is performed by applying a copper back bar (back electrode) 31 to the outer surface side of the pillar portion P and then welding with a spot welding gun 32.

This is to prevent indentations due to spot welding from being generated on the outer surface of the rear fender F functioning as an outer plate, and the back bar 31 provided on the welding jig 33 supporting the body side B is connected to the pillar portion P. Electricity is supplied by applying pressure to the pair of chips (electrodes) 34 and 35 together with the side sill outer panel S, and the back bar 31 substantially functions as a part of the chip 34. Numeral 36 denotes an arm of a welding robot 37 supporting the spot welding gun 32.

Then, even if the vehicle type (vehicle type) is different even on the body side flowing on the same line, the side sill outer panel S
Since the shape and the welding position of the vehicle slightly change, as shown in FIG. 8, a plurality of back bars 31 and 38 corresponding to each vehicle type are prepared on the welding jig 33 side, and welding should be performed. The back bars 31, 38 are selectively erected according to the type of vehicle to perform welding. 39 is the back bar 31,3
This is a rotary actuator for rotating the support frame 8 together with the support frame 40.

However, in the method in which a plurality of back bars 31 and 38 are provided on the welding jig 33 side and selectively switched as described above, the number of back bars 31 and 38 that can be switched is naturally limited, so that the versatility is reduced. However, the back bar switching device is not sufficient, and the entire welding jig 33 is undesirably complicated and large.

On the other hand, as a chip having a function equivalent to the case where a back bar is used in combination, for example, Japanese Utility Model Laid-Open No. 60-28989 (Japanese
58-121455), there is a so-called swivel-type tip. In this method, an auxiliary tip having a flat pressing surface is connected to the tip of the tip via a spherical joint, and the auxiliary tip functions as a back bar.

This swivel-type tip is usually used for either one of a pair of tips of a spot welding gun from the viewpoint of current concentration. Subsequently, when welding is performed between the hit point position P1 and the hit point position P2 that is symmetrical with the line (here, it is assumed that a swivel-type tip is used for one tip 34), the pillar portion P is located at the hit point position P2. In order to position the swivel-type tip on the outer surface side, the position of the spot welding gun 32 needs to be inverted by 180 degrees.

As a result, the movement of the welding robot 37 becomes complicated and the loss time is lengthened by the amount required for changing the posture.In addition, the more complicated the movement of the welding robot 37 becomes, the more the power supply cable and the like attached to the spot welding gun 32 become. Wiring becomes troublesome.

The present invention has been made in view of the above-described problems, and its purpose is to equip the spot welding gun itself with a back electrode and at the same time add a mechanism for inverting the front and back of the back electrode. It is an object of the present invention to provide a spot welding gun that improves the versatility and simplification of welding equipment, and at the same time, makes the movement of a welding robot monotonous and reduces loss time.

Means for Solving the Problems The present invention is directed to a spot welding gun that is supported on the tip of an arm of a welding robot and performs a predetermined welding operation. A back electrode that is pressed together with the workpiece during the pressing operation is provided, and the back electrode is supported, and a rotation drive unit that rotates the back electrode to reverse the front and back of the back electrode is provided. .

According to this structure, since the back electrode is attached to the spot welding gun side, the spot welding gun is positioned at a predetermined hitting position, and then the pressing operation is performed. Welding is performed between the electrodes.

Also, as described above, in the case of welding a specific hitting point and another hitting point having a line-symmetrical relationship, the back electrode was rotated 180 degrees by the rotation driving means to reverse the front and back of the back electrode. Perform welding on above. Accordingly, welding can be performed with the spot welding gun in its original posture.

Embodiment FIGS. 1 to 4 show an embodiment of the present invention, and show an example of a spot welding gun for welding a body side B of an automobile similarly to a conventional example.

As shown in FIGS. 1 to 3, the spot welding gun 1 is connected to and supported by the tip of the arm 36 of the welding robot 37.

A pair of gun arms 3, 3 are connected to the cradle 2 of the spot welding gun 1 via hinge pins 4, and a tip 5 or 6 as an electrode is provided at the tip of the gun arms 3, 3.
Is attached to each. The gun arms 3, 3 are opened and closed by the operation of the actuator 7, and press the pillars P and the side sill outer panels S, which are to be welded, with the tips 5, 6.

A copper back bar 8 is provided as a back electrode in the opposing gap between the chips 5 and 6, while the cradle 2
Is mounted with a hydraulic or pneumatic rotary actuator 9 as rotary drive means. The back bar 8 is connected to the output shaft 10 of the rotary actuator 9 via the holder 11, and when the workpieces are pressurized by the chips 5, 6, the back bar 8 is pressed together with the workpieces. become.

Since the back bar 8 needs to use the surface 8a that contacts the workpiece and the surface 8b that contacts the chip 5 or 6 according to its function, the output shaft 10 of the rotary actuator 9 is rotated by 180 degrees. The front and back sides of the back bar 8 can be reversed by rotating forward or backward, respectively. Reference numeral 12 denotes a power supply cable connecting the chips 5 and 6 and a transformer (not shown).

In the spot welding gun configured as described above,
When welding the hitting position P1 of the joint between the pillar portion P and the side sill outer panel S, one surface 8a of the back bar 8 is connected to the pillar portion P and the other The attitude of the back bar 8 is set in advance so that the tips 8b come into contact with the chips 5, respectively. When the chips 5 and 6 are pressurized in this state, the back bar 8 is sandwiched between the chips 5 and 6 together with the pillar portion P and the side sill outer panel S, and spot welding is performed.

On the other hand, when the welding at the hit point P2 is performed after the welding at the hit point P1, the back bar 8 is moved 180 degrees as shown in FIG.
Welding is performed after turning it upside down and turning it upside down. As a result, one surface 8a of the back bar 8 comes into contact with the outer surface side of the pillar portion P and the other surface 8b comes into contact with the chip 6. Welding can be performed under exactly the same welding conditions.

In addition, when welding at the point P2, the point P1
It is only necessary to move the spot welding gun 1 from the point P2 to the hitting position P2, and it is not necessary to change the attitude of the spot welding gun 1 itself as in the related art.

Effect of the Invention As described above, according to the present invention, since the spot welding gun itself has the back electrode, if the spot welding gun is positioned at a predetermined hitting point, the back electrode is also positioned at the same time. Therefore, versatility is high as compared with the conventional case where a plurality of back electrodes are provided on the welding jig side and selectively switched according to the type of the workpiece to be welded, and the simplification of the welding jig itself is achieved. Miniaturization can be realized.

Further, when welding another spot position having a line symmetry relationship with a specific strike point position, it is only necessary to invert the attitude of the back electrode by 180 degrees, and it is not necessary to change the attitude of the spot welding gun itself. As a result, the movement required of the welding robot is monotonized or simplified, so that the time required for changing the position is shortened, thereby reducing the loss time and, consequently, the cycle time. By reducing the requirement, the routing of the power supply cable and the like attached to the spot welding gun can be simplified.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory view showing one embodiment of the present invention, FIG. 2 is an enlarged view of a main part of FIG. 1, FIG. 3 is a perspective view of a main part showing an attached state of a back bar shown in FIG. FIG. 4 is an explanatory view of the operation when welding at a different hitting point from the hitting point of FIG. 1, FIG. 5 is an explanatory view of the body side of the automobile, and FIG. 6 is A of FIG.
FIG. 7 is an explanatory sectional view of an essential part of FIG. 6, and FIG.
The figure is an explanatory view showing an example of a conventional spot welding gun. 1 ... Spot welding gun, 5,6 ... Tip (electrode), 8
... back bar (back electrode), 9 ... rotary actuator (rotation drive means), 36 ... arm, 37 ... welding robot, B ... body side, P ... pillar part as an object to be welded, P1 , P2 ... Striking position, S ... Side sill outer panel as work piece.

Claims (1)

(57) [Claims] In a spot welding gun supported on an end of an arm of a welding robot and performing a predetermined welding operation, a welding operation is performed in a gap between a pair of electrodes arranged opposite to each other when a pressure is applied to an object to be welded by the electrodes. A spot welding gun comprising: a back electrode that is pressed together with an object; and a rotation driving unit that supports the back electrode and rotates the back electrode so that the back electrode is reversed.