JP3421938B2 - Automatic seam welding line copying machine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic seam welding line copying apparatus, and more particularly to a seam welding method in which a peripheral portion of a fuel tank is sandwiched between a pair of upper and lower electrode wheels to perform seam welding. The present invention relates to an automatic copying apparatus that corrects a welding trajectory of an electrode wheel at a peripheral portion of a fuel tank by horizontally turning the fuel tank while supporting the fuel tank in a no-load floating state in two orthogonal horizontal directions. . [0002] As shown in FIG. 7, a fuel tank 2 comprises an upper half 2a and a lower half 2b formed by a sheet metal press. To manufacture the fuel tank 2, these upper halves 2a
And the lower half 2b are overlapped with each other, and the mutually overlapping peripheral flange portions 4 are temporarily fixed by spot welding at a plurality of positions, and the thus-formed integral fuel tank 2 is set on a special jig 6, and the fuel tank 2 Press the upper surface of the
It is supported on the mold arm 10. The C-shaped arm 10 includes the fixed wall 1
It is supported by the tip of a horizontally bendable arm called an iron man 14 extending in the horizontal direction from 2. The iron man 14 has at least two arm members 1
Reference numerals 4a and 14b extend horizontally via a hinge 16 having a vertical axis, and support the fuel tank 2 movably in a horizontal arbitrary direction with a light force. Exclusive jig 6 and clamp 8
Are C-arms 10 at free rotation axes 18 and 20, respectively.
The copying jig 22 is attached to the lower free rotation shaft 18. The copying jig 22 has a plurality of guided pins 26 protruding from the lower surface of a small plate 24 having a shape similar to a reduced and similar planar shape of the fuel tank 2, and one of the guided pins 26 supports the support arm 28. The guide is linearly guided by a rail 32 fixed to the fixed wall 30 through the intermediary. Each guided pin 26 is arranged in alignment with a vertical line passing through the center of curvature of the corner of the fuel tank 2 as shown in FIG. The illustrated fuel tank 2 has four corner portions R1 to R4, and a total of four guided pins 26 (26a to 26d) protrude from the lower surface of the small plate 24 corresponding to these corner portions R1 to R4. I have. As shown in FIG. 9 (A), the rail 32 has a trough-like shape having a rectangular cross-section with a rear end closed and a front end open. 34,
36 is cut out so that the guided pin 26 enters the rail 32 from one of the two inlets 34 and 36. As shown in FIG. 9 (C), the lower frames of the entrances 34 and 36 are provided with stopper pins 40 each having a lower part supported by a spring 38 and an upper part formed in an inclined shape and capable of moving up and down. The guided pins 26 do not come out. 9B, a stopper block 42 is fixedly provided on the inner surface on one side of the front end of the rail 32, and the guided pin 26 which has advanced in the rail 32 is brought into contact with the stopper block 42. Once stopped, in this state, the small plate 2
When 4 rotates 90 ° in the direction of the arrow, the notch 27 of the guided pin 26 faces the stopper block 42 so that the guided pin 26 can pass through. [0005] A conventional seam welding method for the fuel tank 2 is as follows.
With the fuel tank 2 supported as described above, the peripheral flange portion 4 of the fuel tank 2 is sandwiched between a pair of upper and lower electrode wheels 46 of the seam welding machine, and the two electrode wheels 46 are rotated while rotating the electrode wheel 46. The peripheral flange portions 4 that have been in contact with each other by being energized in between have been resistance-welded. When the straight portion L1 of the peripheral flange portion 4 is seam-welded as shown in FIG. 8, the fuel tank 2 moves forward without changing its posture. At this time, the guided pin 26a moves inside the rail 32 toward the front end. However, when the electrode wheel 46 reaches the corner portion R1 of the peripheral flange portion 4, the movement of the guided pin 26 is prevented by the stopper block 42, and therefore, the fuel tank 2 is moved around the electrode pin 46 around the guided pin 26. It rotates in the direction of the arrow due to the horizontal rotational moment generated by the feed action. When the electrode wheel 46 has finished turning around the corner portion R1, that is, when the fuel tank 2 has been rotated by 90 °, another guided pin 26b enters the rail 32 from the inlet 36 and the peripheral flange portion 4 of the fuel tank 2 Is seam-welded by the electrode wheel 46 in the same manner as described above. When the linear portion L2 is welded, the corner portion R2 is subsequently seam-welded by the electrode wheel 46, and then the guided pin 26c is connected to the inlet 34.
The linear portion L3 enters the rail 32 from above and is seam-welded by the electrode wheel 46. In a conventional automatic seam welding line copying apparatus, a dedicated jig 6 is provided for each type of the fuel tank 2.
Since the profiling jig 22 is required, the dedicated jig 6 and the profiling jig 22 must be newly manufactured every time the shape of the fuel tank 2 is changed. Long production time was required. Therefore, the fuel tank 2 is supported by a robot without using the copying jig 22, and the fuel tank 2 is controlled to be fed in accordance with the progress of the seam welding by the electrode wheel 46, so that the peripheral flange 4 of the fuel tank 2 is controlled. A study has been made to obtain the desired welding line (see Japanese Patent Application Laid-Open No. Hei 7-241684). However, it is extremely difficult to accurately grasp the progress of seam welding by the electrode wheel 46 in real time. This corresponds to the peripheral flange portion 4 of the fuel tank 2.
The thickness of the electrode ring 46 is varied, the peripheral flange portion 4 is softened by energization between the electrode wheels 46, and
6, the rotation speed of the electrode wheel 46 running on the peripheral flange 4 does not match the actual feed distance of the peripheral flange 4, and the feed distance fluctuates minutely and momentarily. is there. The feed control of the fuel tank 2 by the robot may be performed by a teaching method or a feedback control method in which the feed speed or the feed distance of the peripheral flange portion of the fuel tank 2 by the electrode wheel 46 is accurately and real time grasped. As described above, under the situation where the feed speed of the peripheral flange portion 4 fluctuates every moment, control of the robot cannot be performed in time. Also, once the welding line deviates from the regular trajectory, it is not easy to quickly restore it to its original position, and errors due to control delay tend to accumulate, which tends to cause poor welding. There was a problem. An object of the present invention is to completely abandon the concept of the conventional welding jig copying mechanism using the welding jig and the concept of the feed control of the fuel tank 2 depending on the numerical control of the robot. The operator of the seam welding visually checks the welding line and mechanically replaces the work of sending the fuel tank 2, thereby creating expensive copying jigs and complex programs for robots, and troublesome teaching of robots. The object is to eliminate work and the like. [0010] The copying apparatus of the present invention focuses on the fact that the welding line formed by the electrode wheels can be controlled by adjusting the rotation of the fuel tank in the horizontal direction. This will be described with reference to FIGS. FIG. 1 shows an XY table 50 in which three horizontal plates 48a to 48c are vertically stacked, and the first and second plates 48a and 48 from the bottom.
b, the second and third plates 48b, 4 from the bottom
8c, linear motion guides 52 and 54 are provided, respectively. These linear guides 52 and 54 are
a to 48c are slidable in a linear direction, and the lower linear guide 52 and the upper linear guide 54 are arranged orthogonal to each other. That is, the lower linear guide 52 is an X-directional linear guide, and the upper linear guide 54 is a Y-directional linear guide. A copying control shaft 56 is provided on the upper or lower surface of the XY table 50. In FIG. 2, the XY table 5
It is assumed that the scanning control shaft 56 is provided on the lower surface of the zero.
The scanning control shaft 56 is a rotation shaft of a motor capable of precisely controlling a rotation angle, for example, a rotation shaft of a step motor or a servo motor. Then, it is considered that a work 58 to be welded in which two metal sheets are stacked is supported at the lower end of the copying control shaft 56. In such a state that the workpiece to be welded 58 is supported, the peripheral edge of the workpiece (corresponding to the peripheral flange 4 of the fuel tank) is sandwiched between the electrode wheels 46, and the electrode wheel 46 is rotated to seam weld the peripheral edge of the workpiece. . At this time, when the scanning control shaft 56 is rotated in either the forward or reverse direction, the direction of the workpiece 58 with respect to the electrode wheel 46 changes. When this is viewed from the electrode wheel 46 side, the traveling direction of the electrode wheel 46 has changed. FIG. 3 shows an example of the relationship between the rotation direction of the scanning control shaft 56 and the traveling direction of the electrode wheel 46. When the electrode wheel 46 is traveling along the linear portion of the peripheral portion of the workpiece 58 to be welded (see FIG. When the control axis is rotated clockwise in accordance with the point A), the electrode wheel 46 is shifted inside the workpiece 58 to be advanced. When the electrode wheel 46 approaches the corner (point B in FIG. 3), and the scanning control shaft 56 is rotated clockwise by 90 °, the electrode wheel 46 makes a curve at 90 ° to the left in the traveling direction. . This is the control principle of the welding line of the present invention. Although the conventional fuel tank 2 is supported by the iron man 14, the iron man 14 cannot support the rotational reaction force of the scanning control shaft 56, so that the XY table 50 as shown in FIG. Or a supporting means having a function equivalent to this is required. Plate 4
By arranging various known link mechanisms and universal joints between 8a to 48c, it is possible to realize a configuration that supports the work movably in the horizontal direction while supporting the rotational reaction force as in the XY table 50. . The above-described control of the welding line can be easily understood by imagining a cloth feeding operation by a sewing machine. The feed direction of the sewing machine is always straight, but the stitch direction is changed by turning the fabric horizontally and changing the angle of the fabric fed to the needle. The XY table according to the present invention provides a slip between the sewing machine table and the cloth at this time. Further, the function of the hand for turning the fabric corresponds to the copying control axis of the present invention. The welding line automatic copying apparatus according to the present invention is an application of the above-described welding line control principle, and includes a straight line portion and a circular portion.
The periphery of the workpiece composed of the arc is formed by a pair of upper and lower electrode wheels.
Electrode ring at the periphery of workpiece when seam welding by sandwiching
Automatic correction of the welding locus by adjusting the horizontal rotation of the workpiece
In the copying apparatus, the gap between the upper and lower two
The first linear guide and the second linear guide are arranged orthogonal to each other.
Allows any horizontal movement but movement in horizontal turning direction
It is an XY table for constraining said superposing the copying control shaft having a major axis in the direction perpendicular to the movement allowable direction of the XY table vertically, to support one of the XY table or scanning control shaft in the base floor surface With, on the other hand, before
Attaching a special jig for supporting the serial work, seam welding machine
Limit switch fixedly installed near the electrode wheel
And the pin fixed to the dedicated jig,
A sensor that detects when seam welding is started
The electrode ring is moved from a linear portion on the periphery of the workpiece to an arc portion.
When it reaches, the detector of the limit switch
To detect the start of seam welding at the arc.
To make it in, in response to the output of the sensor, in the copying control shaft a predetermined speed, and arranged to control means for driving a predetermined angle, at which the weld line is formed linearly by said XY table While allowing the movement of the work, when the sensor detects the start of seam welding of the arc portion,
The control means rotates the scanning control axis at a predetermined speed and by the central angle of the arc portion. An embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 4, a copying control shaft 74 is provided on a base floor 70 via a base 72.
The scanning control shaft 74 is a rotation shaft such as a step motor or a servo motor capable of precisely controlling a rotation angle. An XY table 50 is supported on the upper end of the scanning control shaft 74.
This XY table 50 is the same as that described above,
The first plate 48 a from the bottom is fixed to the upper end of the scanning control shaft 74. An exclusive jig 6 is fixed on the upper surface of the XY table 50, and the fuel tank 2 is positioned and fixed on the exclusive jig 6. The XY table 50 can be replaced with another mechanism as long as it can move in any horizontal direction but restricts the movement in the horizontal turning direction. For example, as shown in FIG. The universal joint 76 is provided between the upper and lower plates 48d and 48e, or the parallel link mechanism 7 is provided between the upper and lower plates 48f and 48g as shown in FIG.
8 is disposed horizontally, one end 78a of the parallel link 78 is connected to the lower plate 48f, and the other end 78b is slidably engaged with the groove 80 formed on the lower surface of the upper plate 48g. It can be replaced. As shown in FIGS. 4A and 5, four pins 81 are planted below the dedicated jig 6. In FIG. 5, the exclusive jig 6 is omitted for convenience of illustration, and the fuel tank 2 is drawn by a solid line and a two-dot chain line instead. Each pin 8
Reference numeral 1 is provided at a position corresponding to a welding start side contact among contacts between the arc portion R of the fuel tank 2 and the straight portion. A fixed arm 82 extending in the horizontal direction is fixed to the main body of the seam welding machine 44, and the tip of the fixed arm 82 extends downward of the dedicated jig 6. A limit switch 84 is attached to the distal end of the fixed arm 82, and a needle-like detection unit 86 of the limit switch 84 protrudes into the locus of the pin 81. The limit switch 84 is connected to a control circuit (not shown), and when the electrode wheel 46 reaches one end of the arc portion R from the linear portion L while forming the welding line S as shown in FIG. 86, the limit switch 84 is turned on, and the control circuit moves the scanning control shaft 74 to the position shown in FIG.
For example, it is rotated by 90 degrees clockwise. Next, control of the scanning control shaft 74 will be described.
In the welding of the linear portion L of the peripheral portion 4 of the fuel tank 2, the fuel tank 2 is fed in the direction of arrow A in FIG. 5 due to the progress of welding, but the limit switch 84 is turned on in step S1 of FIG.
Until it is determined that the scanning control shaft 74 is stopped. The linear movement of the fuel tank 2 at this time is smoothly performed by the XY table 50. Limit switch 8
When 4 is turned on, the scanning control shaft 74 is rotated at a constant speed V, for example, clockwise in step S2. This rotation is continued until it is determined in step S3 that the rotation angle of the scanning control shaft 74 has become 90 °. When the rotation angle of the scanning control shaft 74 becomes 90 °, in step S4, the scanning control shaft 7
4 is stopped. While the scanning control shaft 74 is rotating, the fuel tank 2 turns with respect to the electrode wheel 46, but the XY table 50 makes the turning movement at this time smooth. In this case, the position of the scanning control shaft 74 remains unchanged. The above is a description of the scanning control shaft 74 in one arc portion R.
In actual control, the above control is repeated by the number of arc portions R, that is, until the fuel tank 2 shown in FIG. 5 passes step S1 four times. Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made. For example, in the above embodiment, the scanning control axis 7
4 is arranged on the lower side, and the XY table 50 is arranged on the upper side. Conversely, the XY table 50 is arranged on the lower side, the copying control shaft 74 is arranged on the upper side, and the exclusive jig 6 is fixed to the upper end of the copying control shaft 74. May be. In this case, the position of the scanning control shaft 74 moves due to its rotation (rotation). Further, by changing the program setting of the scanning control shaft 74, welding of the peripheral flange portion 4 of the fuel tank 2 having an arc of an arbitrary angle is also possible. As described above, according to the present invention, the forming direction of the welding line with respect to the work is controlled only by the rotation of the scanning control shaft, so that a conventional expensive copying jig is not required. Also, since it is only necessary to control ON / OFF the scanning control axis by the sensor, no complicated program is required at all.
Although it has a simple structure, it can exert a great rationalization effect.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of an XY table. FIG. 2 is a perspective view showing a relationship between a welding wheel and a scanning control shaft. FIG. 3 is a plan view of a workpiece showing welding line copying control. FIG. 4A is a side view of an automatic seam welding line copying apparatus,
(B) is a side view of the support means using a universal joint, (C)
FIG. 4 is a perspective view of a support unit using a link mechanism. FIG. 5 is a plan view of a fuel tank. FIG. 6 is a control flowchart of a scanning control axis. FIG. 7 is a side view of a conventional welding line scanning control device. FIG. 8 is a plan view of a fuel tank. 9A is a perspective view of a rail, FIG. 9B is a plan view of a front end of the rail, and FIG. 9C is a longitudinal sectional view of a rear end of the rail. [Description of Signs] 2 Fuel tank 6 Special jig 44 Seam welder 46 Electrode wheel 50 XY table 70 Base floor 74 Copying control shaft 81 Pin 82 Fixed arm 84 Limit switch (sensor) 86 Detecting unit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B23K 11/06 B23K 11/24

Claims (1)

(57) [Claim 1] The periphery of a work composed of a straight portion and an arc portion
When welding the seam between the pair of upper and lower electrode wheels
Correct the welding trajectory of the electrode wheel at the periphery of the
Three-layer play in an automatic copying machine with flat turning adjustment
1st linear guide and 2nd linear guide
Are arranged at right angles to each other to move the workpiece in the horizontal
X and Y that allow any horizontal movement with the
Table and a scanning control axis having a main axis in a direction orthogonal to the movement allowable direction of the XY table ,
While supporting on one foundation floor either the XY table or scanning control shaft, on the other, fitted with a special tool for supporting the workpiece in the vicinity of the electrode wheels of the seam welding machine
Fixed switch and fixed jig
Seam welding is opened with the fixed pin to the arc.
Constituting a sensor for detecting the time when the
When it reaches the arc from the straight part on the periphery of the work,
When the detection part of the limit switch is pressed by the pin,
A control means for detecting the start time of seam welding of the circular arc portion, receiving the output of the sensor, and driving the scanning control axis at a predetermined speed and at a predetermined angle is provided. When the sensor detects the start of seam welding of the circular arc portion, the control means is allowed to move the workpiece when the welding line is formed linearly by the XY table .
A seam welding line automatic copying apparatus configured to further rotate the copying control axis at a predetermined speed and by a central angle of the circular arc portion.