JP3761385B2 - Arc welding method and arc welding machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for arc welding a fillet portion of a lap joint, and an arc welder .
[0002]
[Prior art]
When arc welding is performed on a lap joint in which two members are overlapped using a robot, it is necessary to accurately determine the welding position. FIG. 6 shows an example of a general welding position indexing method. First, the torch 3 is moved from the A position to the B position, the tip of the welding wire 9 is brought into contact with _one member P1, and then the torch 3 is moved to the A position. returned to the position, in which further moved from the position a to the position C to the distal end of the welding wire 9 is brought into contact with the other member P _2, the index the welding position D from the detection result of the B and C positions.
[0003]
[Problems to be solved by the invention]
By the way, as shown in FIG. 7, in the assembly line etc. of a motor vehicle body, many processes of overlapping and welding the thin plates P ₁ and P ₂ having a thickness of about 0.5 to 2 mm are included. In this case, welding is generally performed by spot welding. However, in spot welding, electrodes must be arranged on both sides of the welded part. There is an increasing demand for replacement with arc welding, which requires only this electrode. In arc welding, the fillet portion C in FIG. 7 is welded. In this case, when the indexing method similar to FIG. 6 is used, the end face accuracy of the thin plate P ₁ varies at the B position. It becomes difficult to reliably bring the tip of the welding wire into contact with the end face, and it becomes difficult to index the welding position.
[0004]
Therefore, an object of the present invention is to enable arc welding of a lap joint including a thin plate with high accuracy and low cost.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, an arc welding method according to the present invention is a method of arc welding a fillet portion of a lap joint, and after protruding the tip of a welding wire with an elastic force and contacting one member, The welding wire is locked, and in this state, the welding wire is moved to a position exceeding the fillet portion so as not to come into contact with both base metals, and then the welding wire is moved to the fillet portion side, A welding wire is brought into contact with the end face to start welding.
The arc welding machine according to the present invention includes a torch and a protruding amount management mechanism for managing the protruding amount of the welding wire from the torch, and arc welds the fillet portion of the lap joint, and is elastic. And a wire locking device that locks and unlocks the welding wire, and projects the welding wire tip by the protruding means. After contacting with the base material, the welding wire is locked by a wire lock device.
[0006]
In this welding method, when the tip of the welding wire is brought into contact with one of the base materials, the tip of the welding wire is brought close to the surface of the thin plate, and then the tip of the welding wire is protruded using elastic force. It is desirable to lock the welding wire when the tip contacts the thin plate.
[0007]
In carrying out the above welding method, it is desirable to manage the protruding amount of the wire from the tip of the torch by the protruding amount management mechanism. This wire protrusion amount management mechanism is a mechanism for managing the amount of protrusion of the welding wire from the torch when arc welding the fillet portion of the lap joint, and the welding wire is displaced while accumulating elastic force. After that, the welding wire is returned and moved by the accumulated elastic force, so that the tip of the welding wire protrudes toward the base material side and contacts the base material, and the welding wire is locked at the tip side of the welding wire from the protruding means. And a wire lock device for unlocking, and after the tip of the welding wire comes into contact with the base material by the protrusion of the wire by the protruding means, the wire is locked by the wire lock device.
[0008]
In this case, the elastic force can be applied by the elastic force of the welding wire itself and the elastic deformation of the elastic member.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an embodiment of an arc welding method according to the present invention. As shown in the figure, the application object of this arc welding method is a lap joint for welding a fillet portion C formed by superposing _two thin plate-like base materials P ₁ and P ₂ . In the drawing, both the base materials P ₁ and P ₂ are thin plates. However, as an application target of the present invention, it is sufficient that at least the base material P ₁ on the torch 3 side is a thin plate (about 0.5 to 2 mm). The shape of the base material P ₂ on the side opposite to the torch 3 is arbitrary, and may be, for example, a thick wall shape or a block shape.
[0010]
The broken lines in FIG. 1 represent the movement trajectories {circle around (1)} to {circle around (4)} of the welding wire 9 tip, and the welding start position is determined by operating the torch 3 with the robot along the trajectory. Hereinafter, this indexing procedure will be specifically described.
[0011]
First, the torch 3 is operated to bring the tip of the welding wire 9 into contact with the surface of the base material P ₁ on the torch 3 side. Next, the torch 3 is moved in the direction away from the base material P ₁ (upward in the drawing) to lift the tip of the wire from the surface of the base material P ₁ (1), and then the torch 3 is moved to the surface of the base material P _1. The wire tip is moved to a position beyond the fillet portion C by moving in the parallel direction, and the welding wire 9 is brought into non-contact with both base materials P ₁ and P ₂ ((2)). Next, the torch 3 is moved in a direction (downward in the drawing) approaching the other base material P ₂ (member opposite to the torch 3) ((3)), and then the torch 3 is moved to the fillet portion C side. The welding wire 9 is brought into contact with the end face of the base material P ₁ on the torch 3 side (4). This completes the indexing of the welding position, so that an arc is generated while this state is maintained, and welding is started. The orientation of the torch 3 during welding is preferably in a direction (vertical direction in the drawing) perpendicular to the surfaces of the base materials P ₁ and P ₂ as shown in the figure, but the torch 3 is centered on the tip of the wire. it may have been slightly inclined to the base material P ₂ side.
[0012]
This welding position indexing step, so that the wire tip is not in contact with the other base material P _2, in particular a in FIG, b, for each value of t, it satisfies at least a <b <a + t However, it is possible to achieve such a level of accuracy even in the current robot system. Therefore, even in a lap joint including a thin plate, the welding position can be accurately determined, and high-precision arc welding is possible.
[0013]
In this step, a detecting means for detecting whether or not the welding wire 9 is in contact with the base materials P ₁ and P ₂ is required. The type of the detection means is not particularly limited, but a touch sensor that detects the presence or absence of an electrically conductive state is desirable because it is low-cost and highly reliable.
[0014]
By the way, in this welding position indexing step, when the tip of the welding wire 9 is brought into contact with the surface of the base material P ₁ on the torch 3 side in the previous step ( ₁₎ , the protruding amount φ of the welding wire 9 from the torch 3 is set. The problem is how to stabilize. That is, if there is a variation in the protruding amount φ, the tip of the wire cannot be brought into contact with the surface of the base material P ₁ , and a value A is formed, making it difficult to accurately determine the welding position.
[0015]
On the other hand, since the welding wire 9 is arranged with some margin (play) in the torch 3, the amount of protrusion from the torch 3 tends to become unstable due to the expansion and contraction of the play, and the amount of protrusion φ It is difficult to manage with high accuracy. As a means for managing the protrusion amount, for example, a configuration in which play is taken up at any time by a servo motor or the like is conceivable. However, since motor control generally has a large inertia, it is difficult to take up the welding wire without excess or deficiency.
[0016]
In view of the above problems, the arc welder according to the present invention has the following structure as a management mechanism for stabilizing the wire protrusion amount φ.
[0017]
FIG. 2 illustrates a schematic structure of the torch 3 attached to the tip of the robot arm 1. In the drawing, the torch 3 has a structure in which a cylindrical portion 7 thinner than the cylindrical housing 5 is attached to the tip of the cylindrical housing 5, and the housing 5 and the cylindrical portion 7 are welded from a winding device (not shown). A wire 9 is inserted. The tip of the welding wire 9 protrudes from the end of the cylindrical portion 7.
[0018]
The protrusion amount management mechanism according to the present invention is mainly composed of the wire lock device 11, the protrusion means 12, and these drive devices 13, all of which are attached to the torch 3. The wire lock device 11 is disposed on the distal end side of the welding wire 9 with respect to the protruding means 12, and the illustrated example illustrates the case where the wire lock device 11 is attached to the tubular portion 7.
[0019]
The wire lock device 11 can switch between locking and unlocking of the welding wire 9. In FIG. 1, the lock member 15 accommodated in the hole of the cylindrical portion 7 so as to be reciprocally movable and the cylindrical portion 7 side. The structure which let the welding wire 9 pass between the receiving surfaces 17 is illustrated. In this case, by pressing the locking member 15 against the receiving surface 17, the welding wire 9 sandwiched between the receiving surface 17 is locked, and by moving the locking member 15 away from the receiving surface 17, the welding wire 9 is It will be in the unlocked state with free payout.
[0020]
The protruding means 12 softly protrudes the welding wire 9 using an elastic force. The protruding means 12 in the illustrated example has a pressing member 19 and a receiving member 21 that face each other, and the welding wire 9 passes between the pressing member 19 and the receiving member 21 while drawing a gentle arc. . In this embodiment, the opposing surface 19a of the pressing member 19 facing the receiving member 21 has a convex curved surface shape, the opposing surface 21a of the receiving member 21 facing the pressing member 19 has a concave curved surface shape, and the curvature of the convex curved surface 19a is a concave curved surface 21a. Is slightly smaller than the curvature. A guide member 23 is attached to the pressing member 19, and the guide member 23 is moved back and forth in a direction substantially orthogonal to the feeding direction of the welding wire 9 by the driving device 13, so that the pressing member 19 is moved to the receiving member 21 side. Approach / separate. The receiving member 21 is elastically supported by the housing 5 via one or more elastic members 25 (for example, springs).
[0021]
The drive device 13 drives the wire lock device 11 and the protruding means 12, and in the present embodiment, the case where both are driven by a common drive source (cylinder 27) is illustrated. The illustrated cylinder 27 is a double-sided double acting type air cylinder, for example, and a cam member 29 is mounted on one piston rod 27a. The cam member 29 guides, for example, a spherical guide portion 15a provided on the lock member 15, and includes a flat portion 29a parallel to the operation direction of the cylinder 27 and a tapered portion 29b inclined with respect to the flat portion 29a. ing. The end of the other piston rod 27b is formed in, for example, a spherical shape that can move on the tapered surface 23a formed in the guide member 23.
[0022]
Hereinafter, a procedure for managing the protrusion amount φ by the protrusion amount management mechanism will be described.
[0023]
First, the robot is activated to bring the tip of the welding wire 9 closer to the base material P ₁ on the torch 3 side. When the cylinder 27 is started in this state and the other piston rod 27b is advanced (one piston rod 27a is retracted), the tip spherical surface portion of the piston rod 27b comes into contact with the tapered surface 23a of the guide member 23. When the piston rod 27b is further advanced, the pressing member 19 is moved to the receiving member 21 side and pressed against the receiving member 21 by the guide action of the tapered surface 23a. Therefore, the welding wire is pressed between the pressing member 19 and the receiving member 21. 9 is restrained. At this time, the elastic member 25 is compressed by the pressing force of the pressing member 19, and the receiving member 21 is displaced to the outer diameter side (the outer diameter side of the arcuate wire 9), and at the same time, between the pressing member 19 and the receiving member 21. The welding wire 9 restrained by is displaced toward the outer diameter side while reducing its radius of curvature. On the other hand, on the wire lock device 11 side, since the guide portion 15a of the lock member 15 slides on the flat surface portion 29a of the cam member 29, the lock member 15 is held at a position away from the receiving surface 17, and accordingly, the wire lock The device 11 is unlocked. FIG. 2 shows a state where the wire lock device 11 is in the unlocked state as described above, and the wire 9 protrudes and is displaced to the outer diameter side by the means 12. In addition, after displacing the welding wire 9 in this manner, the robot may be activated to bring the tip of the welding wire 9 closer to the base material P ₁ on the torch 3 side.
[0024]
Next, when the cylinder 27 is reversely driven and the other piston rod 27b is retracted (when one piston rod 27a is advanced), the shaft end of the piston rod 27b is separated from the taper surface 23a, so that the elastic member 25 is stored. The receiving member 21, the welding wire 9, and the pressing member 19 are elastically returned to the initial positions by the urged elastic force, and further by the elastic force of the welding wire 9 itself (at this time, the pressing member 19 and the receiving member 21 In the meantime, no restraining force is applied to the welding wire 9, and the welding wire 9 is unlocked). When the welding wire 9 is elastically restored in this way, as shown in FIG. 3, the length of the arc portion of the welding wire 9 becomes shorter than that before the restoration (indicated by a broken line). Moves to the wire tip side, the tip of the welding wire 9 slowly protrudes, and soft-touches the base material P ₁ on the torch 3 side (the protrusion width is represented by δ). In order to smoothly project the welding wire 9, the wire lock device 11 is held in the unlocked state.
[0025]
Thereafter, when the reverse activation of the cylinder 27 is continued, the guide portion 15a of the lock member 15 is guided by the tapered surface 29b of the cam member 29, the lock member 15 moves to the receiving surface 17 side, and the lock member 15 and the receiving surface 17 In the meantime, the welding wire 9 is restrained and the wire lock device 11 is switched to the locked state. In this way, the wire lock device 11 locks the wire tip in contact with the base material P ₁ , so that the protruding amount φ of the wire 9 is kept at a constant value. Thereafter, even if the robot arm 1 is operated, the welding wire The protruding amount φ of 9 is stably maintained.
[0026]
After the above steps are completed, welding of the fillet portion C is started through the welding position indexing steps (1) to (4) shown in FIG.
[0027]
According to the wire protrusion amount management mechanism, as long as the stop position of the torch 3 is constant, the protrusion amount φ of the welding wire 9 is stably held at a constant value. Therefore, the welding start position does not shift even in the subsequent welding operation, and accurate welding can be performed. In particular, in this invention, is performed slowly by utilizing the elastic force of the elastic member 25 provided with protrusion of the welding wire 9 to the elastic force or another wire itself, the wire tip can be soft touch the base material P _1, It is possible to prevent the wire from buckling due to a sudden protrusion and to secure an appropriate protruding amount φ without excess or deficiency. The means for giving the elastic force may be only the elastic force due to the elastic deformation of the welding wire 9. However, in this embodiment, in order to improve the operation stability, a separate elastic member 25 is further added. Is used together with the elastic force of the welding wire 9. Of course, depending on welding conditions and the like, only the elastic force of the welding wire 9 may be used.
[0028]
FIG. 4A shows a wire accommodating groove 31 formed in the protruding surface 12 of the pressing member 19 along the wire feeding direction in order to stabilize the feeding direction of the welding wire 9 in the protruding means 12. . In this case, it is desirable that the distance between the convex curved surface 19a and the concave curved surface 21a can be managed to an appropriate value by an adjuster 30 made of a bolt or the like so that the wire 9 can be smoothly fed. In FIG. 5B, the groove 31 is similarly formed on the convex curved surface 19a. Even when the convex curved surface 19a and the concave curved surface 21a come into close contact with each other, the wire 9 and the groove 31 are drawn out smoothly. The play between is big. 4 (a) and 4 (b) may be formed on both the convex curved surface 19a and the concave curved surface 21a of the receiving member 21, and the similar groove 31 is formed on the locking member 15 of the wire lock device 11. Alternatively, it can be formed on either one or both of the receiving surfaces 17.
[0029]
In the structure of FIG. 4, when the welding wire 9 returns from the displacement position (FIG. 2) to the initial position (FIG. 3), the welding wire 9 may come off from the groove 31 provided on the convex curved surface 19 a of the pressing member 19. FIG. 5 prevents this. In this embodiment, the pressing member 19 is divided into a central portion 191 and end portions 192 and 193 on both sides in the feeding direction, and grooves 31 are formed on the respective convex curved surfaces 191a to 193a. Provided. Both end portions 192 and 193 are elastically supported by the central portion 191 via an elastic member 33 such as a spring. In this case, when the welding wire 9 is displaced to the outer diameter side, the elastic member 33 is elastically pressed as the pressing member 19 advances, and an elastic force is accumulated. On the other hand, since the end portions 192 and 193 are relatively displaced toward the receiving member 21 by the elastic force of the elastic member 33 when returning to the initial position (shown by a broken line), the welding wire 9 does not come off the groove 31.
[0030]
Note that the above structure is merely an example, and for example, the wire lock device 11 can adopt any structure as long as the lock and unlock of the welding wire 9 can be arbitrarily switched. Further, the structure of the protruding means 12 is not limited to that shown in FIG. 2 as long as it elastically protrudes the welding wire. Further, the drive device 13 can adopt any structure as long as the lock device 11 and the protruding means 12 can be individually driven. In addition to being driven by a common drive source 27 as shown, both the devices 11 and 12 are independent. You may drive with the drive source (cylinder etc.).
[0031]
Further, in the present embodiment, the welding wire 9 is curved between the pressing member 19 and the receiving member 21, but this may be made straight.
[0032]
【The invention's effect】
As described above, according to the arc welding method according to the present invention, even when there is variation in the end face accuracy of the thin plate-like base material in the fillet portion, the welding position can be accurately determined, and accordingly, the lap joint (particularly, When one of the base materials is a thin plate, the arc welding can be reliably performed with high accuracy.
[0033]
In this case, since the protruding amount is stabilized by using the above-described wire protruding amount management mechanism, the welding position can be indexed with high accuracy and the welding quality is improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically illustrating an arc welding method according to the present invention.
FIG. 2 is a cross-sectional view of a protrusion amount management mechanism according to the present invention.
FIG. 3 is a cross-sectional view showing the operation of the protrusion amount management mechanism.
FIG. 4 is a cross-sectional view of the protruding means (direction orthogonal to the wire feed direction).
FIG. 5 is a cross-sectional view of the protruding means (parallel to the wire feed direction).
FIG. 6 is a cross-sectional view showing a conventional arc welding method.
FIG. 7 is a cross-sectional view of a lap joint.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Robot arm 3 Torch 9 Welding wire 11 Wire lock apparatus 12 Protruding means 13 Drive apparatus 19 Press member 21 Receiving member 25 Elastic member

Claims (2)

A method of arc welding a fillet portion of a lap joint,
After protruding the tip of the welding wire with elastic force and making it contact with one member, the welding wire is locked, and in this state, the welding wire is moved to a position beyond the fillet portion so as not to contact with both base materials. Then, the welding wire is moved to the fillet portion side, the welding wire is brought into contact with the end surface of the one base material, and welding is started. An arc welding machine comprising a torch and a protruding amount management mechanism for managing a protruding amount of a welding wire from the torch, and arc welding a fillet portion of a lap joint;
The protruding amount management mechanism includes a protruding means that protrudes the tip of the welding wire by elastic force to contact the base material, and a wire lock device that locks and unlocks the welding wire, and the welding wire is protruded by the protruding means by the protruding means. An arc welding machine characterized in that a welding wire is locked by a wire lock device after contacting the tip of the wire with a base material.

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