JP2005111494A - Spot welding gun and spot welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an increase in the size of a spot welding gun having a structure in which a distance between electrodes is greatly increased.
An arc-shaped guide rail 17 is provided on a movable electrode side gun arm 5 formed in an arc shape, and an arc-shaped rack 23 that moves along the guide rail 17 is provided. The movable electrode 9 is provided at the tip of an arc-shaped electrode holder 27 provided so as to move integrally with the rank 23. A servo motor is connected to the rack 23 via a pinion 15, and the movable electrode 9 is moved in an arc shape in a direction approaching and separating from the fixed electrode 7 by driving the servo motor.
[Selection] Figure 1

Description

  The present invention relates to a spot welding gun and a spot welding method for performing welding in a state where a pair of electrodes are moved close to each other and a workpiece is sandwiched therebetween.

In a conventional automobile body assembly process, when joining body panels, a spot welding gun as described in Patent Document 1 below, for example, is used.
JP, 2001-87864, A This spot welding gun performs welding by pressing and holding a work with a pair of electrodes, and each electrode is provided at the tip of a gun arm and can move in a direction approaching and separating from each other. It has become.

  By the way, in the above-described vehicle body assembly process, as a spot welding gun used when the floor panel constituting the vehicle body floor portion and the side panel constituting the vehicle body side portion are combined, one that opens a large gap between the electrodes. Necessary.

  However, in this case, since the approaching movement of the pair of electrodes is linear, there is a problem that the size of the welding gun is increased when the gap between the electrodes is widened.

  In view of this, an object of the present invention is to prevent an increase in the size of a spot welding gun having a structure in which the distance between electrodes is greatly increased.

  In order to achieve the above object, the present invention provides a spot welding gun in which a pair of electrodes held by a gun arm is provided so as to be able to move toward and away from each other, and a workpiece is pressed and clamped by the pair of electrodes. The movement trajectory of the pair of electrodes has a circular arc shape.

  According to the present invention, since the movement trajectory when the pair of electrodes move toward and away from each other is formed in an arc shape, it is possible to prevent the welding gun from being enlarged even when the gap between the electrodes is widened.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a side view of a spot welding gun showing an embodiment of the present invention. This spot welding gun includes a bracket 1 attached to an arm of a welding robot (not shown), and a fixed electrode side gun arm 3 and a movable electrode side gun arm 5 are provided on the bracket 1, respectively.

  The fixed electrode-side gun arm 3 includes an arc portion 3a that has an arc shape from one end to the other end connected to the bracket 1, and a straight portion 3b that extends to the right in FIG. And a bent end portion 3c which is bent in two stages from the other end of the straight portion 3b and whose tip protrudes downward in FIG. And the fixed electrode 7 is provided through the electrode holder 6 in the front-end | tip (lower end) of this front-end | tip bending part 3c.

  On the other hand, the movable electrode-side gun arm 5 is separated from the end of the arc portion 3a on the bracket 1 side by an angle θ with respect to the tip of the fixed electrode 7 around the center O of the circle including the arc shape of the arc portion 3a. Up to the position, an arc portion 5a continuing to the arc portion 3a is provided. The movable electrode 9 moves in an arc shape along the arc portion 5a, and the workpiece is pressed and clamped with the fixed electrode 7 to perform spot welding. That is, the movement locus when the pair of electrodes move toward and away from each other has an arc shape.

  As shown in FIG. 2, which is a cross-sectional view taken along the line AA of FIG. 1, the inner surface of the arc portion 5a of the movable electrode side gun arm 5 is provided with an encoder 11 as a drive source. A servo motor 13 is attached, and a pinion 15 is interlocked to the servo motor 13.

  Further, an arcuate guide rail 17 protruding downward from the arc portion 5a is provided along the arc portion 5a at the lower portion of the left side surface of the arc portion 5a in FIG. A rear guide block 19 is movably attached along the guide rail 17 to a portion of the guide rail 17 protruding downward from the arc portion 5 a.

  Further, an arc-shaped connecting arm 21 is fixed to the left side surface of the rear guide block 19 in FIG. The connecting arm 21 extends along the guide rail 17 and from the rear end (the left end in FIG. 1) to which the rear guide block 19 is fixed to the front end of the movable electrode side gun arm 5 in the state of FIG. Has reached.

  An arc-shaped rack 23 having the same length as that of the connecting arm 21 is fixed to the inner surface (upper surface in FIG. 2) of the connecting arm 21. The above-described pinion 15 is engaged with the tooth portion 23 a formed inside the rack 23.

  Further, as shown in FIG. 3 which is a BB sectional view of FIG. 1, a front guide block 25 is fixed to the guide rail 17 side of the front end portion (right end portion in FIG. 1) of the connecting arm 21. The front guide block 25 is also movable along the guide rail 17 described above.

  A base end portion of the electrode holder 27 is fixed to the lower portion of the front guide block 25. The electrode holder 27 is formed in an arc shape from a fixed portion to the front guide block 25 to a tip portion holding the movable electrode 9.

  That is, the electrode holder 27 including the movable electrode 9 is integral with the connecting arm 21 via the front guide block 25, and further along the guide rail 17 together with the rack 23 integral with the connecting arm 21 and the rear guide block 19. 1 is movable between a forward position indicated by a solid line in FIG. 1 and a backward position indicated by a two-dot chain line.

  According to the spot welding gun having the structure described above, the work electrode (not shown) is pressed and clamped between the fixed electrode 7 and the movable electrode 9 by setting the movable electrode 9 to the solid line position in FIG. Weld. The pressurizing operation at this time is performed by the servo motor 13 shown in FIG.

  When the servo motor 13 is rotationally driven in the direction opposite to that during the pressurizing operation described above, the movable electrode 9 moves away from the fixed electrode 7 and moves to the retracted position indicated by the two-dot chain line in FIG. The distance between the electrodes 7 and 9 is greatly increased.

  In this way, by setting the distance between the electrodes 7 and 9 to be largely open, for example, in a vehicle body assembly process in an automobile, a floor panel constituting a vehicle body floor portion and a side panel constituting a vehicle body side portion are provided. It is possible to cope with the combination.

  According to the above-described embodiment of the present invention, since the moving locus of the movable electrode 9 has an arc shape, the outer dimension of the welding gun does not increase even when the gap between the electrodes is widened. An increase in size can be prevented. By using a welding gun that prevents the increase in size, it is possible to reduce the size of a welding robot (not shown) that holds the welding gun.

  In addition, by using the servo motor 13 as a drive source, it is possible to set optimum pressure conditions corresponding to various workpieces, and to improve the welding quality and shorten the working time.

  Furthermore, according to the present embodiment, the movable electrode 9 may be moved in an arc along the arc-shaped movable electrode side gun arm 5, so that the servo as a drive source can be used even if the gap between the electrodes is widened. The motor 13 does not need to be particularly large, and can contribute to weight reduction.

  Further, since the operation of pressing and clamping the workpiece and the operation of moving the movable electrode 9 toward and away from the fixed electrode 7 are performed by one servomotor 13, two power sources are provided separately. Compared to, the weight of the entire welding gun can be reduced.

  Furthermore, since the movable electrode 9 is moved by meshing the pinion 15 provided in the servo motor 13 with the rack 23 on the movable electrode 9 side, the movable electrode 9 can be moved reliably.

  Furthermore, since the movable electrode 9 is moved by moving the guide blocks 19 and 25 on the movable electrode 9 side to the guide rail 17 provided on the movable electrode side gun arm 5, the fixed electrode 7 of the movable electrode 9 is moved. Can be accurately moved, and misalignment between the electrode tips can be prevented.

It is a front view of the spot welding gun which shows one Embodiment of this invention. It is AA sectional drawing of FIG. It is BB sectional drawing of FIG.

Explanation of symbols

3 Fixed electrode side gun arm 5 Movable electrode side gun arm (arc-shaped gun arm)
7 Fixed electrode 9 Movable electrode (one electrode)
13 Servo motor (drive source)
15 Pinion 17 Guide rail 19, 25 Guide block

Claims (5)

  A pair of electrodes held by a gun arm are provided so as to be able to move toward and away from each other, and in a spot welding gun that performs welding while pressing and holding a workpiece by the pair of electrodes, the movement when the pair of electrodes move toward and away from each other Spot welding gun characterized by a circular arc trajectory.   The spot welding gun according to claim 1, wherein a single drive source for moving the pair of electrodes in an arc shape is provided.   A gun arm that holds one of the pair of electrodes is formed in an arc shape, a drive source and a pinion that is rotated by the drive source are provided in the arc-shaped gun arm, and an arc-shaped rack that meshes with the pinion The spot welding gun according to claim 1 or 2, wherein the spot welding gun is integrated with an electrode so as to be movable with respect to the arc-shaped gun arm.   4. The spot welding gun according to claim 3, wherein a guide rail is provided along the arc-shaped gun arm, and a guide block guided and moved by the guide rail is provided in the arc-shaped rack. In a spot welding method using a spot welding gun that performs welding in a state in which a pair of electrodes are moved closer to each other and a workpiece is pressed and clamped, a movement trajectory when the pair of electrodes move closer to and away from each other is an arc shape. A spot welding method characterized in that the pair of electrodes are brought close to each other along an arcuate movement trajectory and the workpiece is pressed and clamped, and spot welding is performed on the workpiece in this state.

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