JP3421939B2 - Automatic seam welding line copying machine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to an automatic seam welding line copying apparatus, and more particularly, to seam welding of a saddle-shaped fuel tank by sandwiching a peripheral portion thereof between a pair of upper and lower electrode wheels. At this time, while the fuel tank is supported in a no-load floating state in two directions perpendicular to the horizontal direction, the welding locus of the electrode wheel at the peripheral portion of the fuel tank is corrected by adjusting the fuel tank horizontally turning and using a saddle-shaped projection. The present invention relates to an automatic copying apparatus that supports a work so as to be swingable so that a portion can be welded. 2. Description of the Related Art As shown in FIG. 9, 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. 11 (A), the rail 32 has a trough-like shape having a rectangular cross-section with a closed rear end and an open front end. 3
4 and 36 are cut out so that the guided pin 26 enters the rail 32 from one of these two inlets 34 and 36. In the lower frame of entrances 34 and 36,
As shown in (C), a stopper pin 40 whose lower part is supported by a spring 38 and whose upper part is formed in a slope is provided so as to be able to move up and down, so that the guided pin 26 once inside the rail 32 does not go outside. It has become. A stopper block 42 is fixedly provided on one inner surface of the front end of the rail 32 as shown in FIG. 11B, and the guided pin 26 which has advanced in the rail 32 is brought into contact with the stopper block 42. When the small plate 24 is turned 90 ° in the direction of the arrow by the feeding action of the electrode wheel 46 in this state, the notch 27 of the guided pin 26 faces the stopper block 42 and the passage of the guided pin 26 is stopped. It is now acceptable. [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. 10, 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 straight 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 entrance 3
4, the straight portion L3 enters the rail 32 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. In order to effectively use the space around the fuel tank 2, the lower surface of the fuel tank 2 may be depressed like the lower surface of a saddle, and a differential may be inserted and arranged here. In the fuel tank, the peripheral flange portion 4 has a large upward convex portion, and therefore cannot be dealt with by the conventional seam welding technology only for a flat surface. In view of the above, the seam welding of the saddle type fuel tank is enabled by rotating the fuel tank around the rotation axis disposed at the center of curvature of the protrusion at the convex portion of the peripheral flange portion. Technology has been proposed (Japanese Patent Publication 7-7)
No. 5779). However, in this technique, a dedicated jig for supporting the fuel tank must be significantly modified in order to cope with convex portions having different curvatures. An object of the present invention is to completely abandon the conventional concept of a welding line copying mechanism using a copying jig and the concept of feed control of the fuel tank 2 relying on numerical control of a robot, and a completely new idea, that is, 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. An object of the present invention is to eliminate the need for work and the like, and to make it possible to easily cope with welding of a saddle type work. 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, the first and second linear guides 52, 52, respectively.
54 are provided. The first and second linear motion guides 52 and 54 enable the plates 48a to 48c to slide in a linear direction, and the lower first linear motion guide 52 and the upper second linear motion guide 54 are mutually connected. They are arranged orthogonally. That is, the first translation guide 52 is an X-direction translation guide, and the second translation guide 54 is a Y-direction translation 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 work 58 to be welded is supported, the periphery of the work (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 work periphery. . 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 slide supporting means having a function equivalent thereto is required. By arranging various known link mechanisms and universal joints between the plates 48a 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. is there. 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 is applied to a peripheral portion of a workpiece.
When seam welding is performed with the edge sandwiched between a pair of upper and lower electrode wheels
Correction of the welding locus of the electrode wheel at the periphery of the workpiece
In an automatic copying machine that performs horizontal turning adjustment,
1st linear guide and 2nd linear guide
Are arranged perpendicular to each other, and
Allow any horizontal movement while constraining the movement of
An XY table and a scanning control axis having a main axis in a direction perpendicular to the movement allowable direction of the XY table are vertically overlapped, and one of the XY table and the scanning control axis is moved to the XY table and the base floor surface. Arranged between X
A spring supporting the load above the Y table, and an XY table
The rocking direction of the
And a work piece having a portion to be seam-welded while supporting the work piece on a base floor surface through a swingable swing support means having a bendable leg portion that is restricted to a vertical plane included in the base. Attach the special jig and set the welding line of the work
Template with the same or similar contour as
Attach the work to the jig in alignment with the work
Vertical including the axis of the pair of upper and lower electrode wheels of the
Reference to a position in the plane that faces the contour of the template
The members are fixedly arranged, and the outline of the template and the reference members
A distance measuring sensor for detecting the gap distance between the
The gap distance becomes constant based on the output from the sensor.
Thus, the control means for controlling the rotation of the scanning control shaft is provided . An embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 4, a base plate 72 is provided on a base floor 70,
XY via four coil springs 74 in the front, rear, left and right directions above
A table 50 is provided. This XY table 50
Is the same as that described above, and the first plate 48 a from the bottom is fixed to the upper end of the coil spring 74. X
Between the lower four corners of the Y table 50 and the base plate 72, there are disposed legs 75, the middle of which can be bent in the left-right direction.
The swing direction of the XY plate 50 is regulated by the legs 75 in the horizontal direction in the drawing, that is, in the vertical direction (the direction of the arrow in FIG. 5) including the side surface of the electrode wheel 46 of the seam welding machine. On the upper surface of the XY table 50, a copying control shaft 8 is provided.
2 are provided. The scanning control shaft 82 is a rotation shaft such as a step motor or a servo motor capable of precisely controlling the rotation angle. The exclusive jig 6 is attached to the upper end of the scanning control shaft 82.
Are fixed, and the fuel tank 2 is positioned and fixed on the dedicated jig 6. The fuel tank 2 has a lower surface center recessed like a lower surface of a saddle, and a vehicle differential or the like is inserted and arranged in the recessed portion. 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. A universal joint 76 is provided between the upper and lower plates 48d and 48e, or a 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. A template 84 is fixed below the dedicated jig 6 as shown in FIG. The template 84 is formed of a plate having a contour similar to the contour of the expected welding line of the peripheral flange portion 4 of the fuel tank 2, and is aligned with the fuel tank 2, that is, the corresponding sides face in the same direction. It is arranged horizontally. On the other hand, as shown in FIG. 7, a fixed arm 90 extends from the main body of the seam welding machine 44, and a reference member 92 is attached to the tip of the fixed arm 90. The reference member 92 is located in a vertical plane including the axis of the pair of upper and lower electrode wheels 46 in common as shown in FIG. 8 and is opposed to the contour of the template 84 as shown in FIG. A distance measuring sensor 94 is provided near the reference member 92 at the tip of the fixed arm 90.
Is attached. The distance measuring sensor 94 measures a gap distance between the contour of the template 84 and the reference member 92. Next, the seam welding of the fuel tank 2 will be described together with the control of the scanning control shaft 82. When the peripheral flange portion 4 of the fuel tank 2 is seam-welded without rotating the scanning control shaft 82, the welding line is basically straight, but the welding line due to unevenness in the thickness of the peripheral flange portion 4 or unevenness as it is can be obtained. Error cannot be corrected. When the front end of the welding line deviates from the scheduled welding line, the distance between the reference member 92 and the contour of the template 84 changes to either wide or narrow. This is used as a distance measuring sensor 94
Is detected, and the rotation of the scanning control shaft 82 is controlled so that the change in the width of the interval is restored. Further, welding of the corner portion of the peripheral flange portion 4 of the fuel tank 2 is also performed by rotation of the copying control shaft 82. That is, at the same time when the electrode wheel 46 passes the welding start point of the corner portion, the distance between the contour of the template 84 and the reference member 92 is widened, and the distance measuring sensor 94 continuously detects the degree of the widening of the distance, The copying control shaft 82 is rotated by control means (not shown) so as to return the spread. When the electrode wheel 46 welds the upward convex portion 96 of the peripheral flange portion 4, the position of the electrode wheel 46 is unchanged, so that the fuel tank 2 is slightly lowered and the electrode wheel 46 is lowered.
The fuel tank 2 tilts in the left-right direction because the portion sandwiched between the holes always tries to be horizontal. Such vertical movement and tilting of the fuel tank 2 are permitted by the coil spring 74 and the leg 75, so that no excessive force acts on the electrode wheel 46 or the fuel tank 2. The scanning control shaft 82 can be controlled by means other than the template 84, the reference member 92 and the distance measuring sensor 94. Generally, the seam welding scheduled line of the fuel tank 2 and the actual welding It suffices if there is a sensor for detecting a deviation from the front end of the line, and control means for controlling the rotation of the scanning control shaft 82 based on the output from the sensor so as to make the deviation zero. The above-described distance measuring sensor 94 is used for the template 8
The distance between the reference line 92 and the reference member 92 is detected, which is synonymous with detecting the deviation between the scheduled seam welding line and the actual front end of the welding line. Therefore, it is also possible to use a sensor that directly detects the position of the front end of the welding line of the fuel tank 2 instead of the distance measuring sensor 94. 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, the swing supporting means by the coil spring 74 and the leg 75 can be replaced with another functionally equivalent swing supporting means. As an example, there is proposed a structure in which a floating body is floated on a liquid tank, the moving direction of the floating body is appropriately regulated by a guide member, and slide support means and a copying control shaft are provided on the floating body. In the above-described embodiment, the copying control shaft 82 is arranged on the upper side, and the XY table 50 is arranged on the lower side.
The dedicated jig 6 may be fixed to the upper surface of the XY table 50 by arranging the Y table 50 on the upper side and the scanning control shaft 82 on the lower side. As described above, according to the present invention, the direction in which the welding line is formed on the workpiece is controlled only by the rotation of the scanning control shaft, so that the conventional expensive copying jig or robot can be used. There is no need for complicated programs at all, and a significant rationalization effect can be achieved. In addition, since the slide support means and the scanning control shaft are employed, the swing support means can easily cope with seam welding of a saddle-type work. Basically, it can be handled without replacing the dedicated jig, so it is more advantageous in terms of equipment than the conventional method of seam welding the saddle type fuel tank by rotating the fuel tank around the rotation axis, and Also, a fuel tank having a unique shape having a peripheral flange portion whose curvature continuously changes can be easily manufactured.

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. 4 is a perspective view of the automatic seam welding line copying apparatus of the present invention. FIG. 5 is a front view of the automatic seam welding line copying apparatus of the present invention. FIG. 6A is a side view of another embodiment of the slide support means, and FIG. 6B is a perspective view of still another embodiment of the slide support means. FIG. 7 is a side view of a template and a distance measuring sensor. FIG. 8 is a front view of an electrode wheel and a distance measuring sensor. FIG. 9 is a side view of a conventional welding line scanning control device. FIG. 10 is a plan view of a fuel tank. 11A is a perspective view of a rail, FIG. 11B is a plan view of a front end of the rail, and FIG. 11C 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 Coil spring 82 Copying control shaft 84 Template 90 Fixed arm 92 Reference member 94 Distance measuring sensor 96 Upward projection

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-230488 (JP, A) JP-A-62-13274 (JP, A) Actually open 1987-155,972 (JP, U) Actually open 1- 135177 (JP, U) Japanese Utility Model Showa 54-108729 (JP, U) Japanese Patent Publication No. 3-33073 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 11/06 B23K 11 /twenty four

Claims (1)

(57) [Claims] [Claim 1] A peripheral portion of a work is sandwiched between a pair of upper and lower electrode wheels.
Of the electrode ring at the periphery of the workpiece during seam welding
Automatic profiling that corrects the tangent locus by adjusting the horizontal rotation of the work
In the apparatus, the first straight line is inserted into the upper and lower gaps of the three-layer plate.
Before the moving guide and the second linear guide are arranged orthogonal to each other.
Any water with the movement of the work in the horizontal
An XY table that allows movement in the horizontal direction;
In the direction perpendicular to the movement allowable direction Bull superposing the copying control shaft having a major axis in the vertical, one of the XY table or scanning control axis, the XY table and the base
It supports the upper load from the XY table
Seam welding machine to hold spring and swing direction of XY table
Of a pair of upper and lower electrode rings
A dedicated jig for supporting a work having a portion to be seam-welded is mounted on the other side while being supported on a foundation floor surface via a swingable swing supporting means having a bendable leg portion ,
Has the same or similar contour as the welding line of the work
Align the template with the work with the dedicated jig
And a pair of upper and lower electrode wheels of the seam welding machine.
Of the template in a vertical plane containing the axis of
The reference member is fixedly arranged at a position facing the
Distance measuring sensor that detects the gap distance between the contour of the rate and the reference member
And a sensor based on the output from the distance measuring sensor.
Rotation control of the scanning control axis so that the gap distance is constant
A seam welding line automatic copying apparatus, characterized in that control means for controlling the seam welding line is provided.