JPH09314349A - Seam weld line automatic copying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a high cost copying jig required for seam welding and complicated program, etc., for a robot to support a work. SOLUTION: An XY table 50 as a support means of a fuel tank 2, which allows movement in arbitrary horizontal direction and restricts movement in horizontal turning direction, and a copying control shaft 84 having a spindle in the direction orthogonal to the moving allowable direction of XY table 50 are stacked up/down. Either one of the XY table 50 or copying control shaft 84 is supported with the tip of a robot arm 82, on the other, a special jig 6 to support the fuel tank 2 having a part to be seam welded is mounted. A forming direction of the weld line in fuel tank 2 is changed/controlled by rotation of the copying control shaft 84. Control of the copying control shaft 84 is executed based on the output of a range sensor 98 to detect the interval between a template 92 mounted to the special jig 6 and a reference member 96.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seam welding line automatic copying apparatus, and more particularly, when performing seam welding by sandwiching a peripheral portion of a fuel tank with a pair of upper and lower electrode wheels, the fuel tank is arranged in two horizontal directions. The present invention relates to an automatic copying apparatus in which a welding locus of an electrode wheel on a peripheral portion of a fuel tank is corrected by horizontally swinging and adjusting the fuel tank while supporting the fuel tank in an unloaded floating state.

[0002]

2. Description of the Related Art As shown in FIG. 8, 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 peripheral flange portions 4 that are overlapped with each other are temporarily fixed by spot welding at a plurality of points, and the integrated fuel tank 2 thus formed is set on the dedicated jig 6, and the fuel tank 2 Press the upper surface of the with the clamp 8 to C
It is supported by the mold arm 10. The C-shaped arm 10 has a fixed wall 1
It is supported at the tip of a horizontally bendable arm called an iron man 14 which extends horizontally from 2. This iron man 14 has at least two arm members 1
4a and 14b are horizontally extended via a hinge 16 having a vertical axis, and support the fuel tank 2 movably in an arbitrary horizontal direction with a light force. Dedicated jig 6 and clamp 8
Is a C-shaped arm 10 with free rotating shafts 18 and 20, respectively.
A copying jig 22 is attached to the lower free rotating shaft 18. The copying jig 22 is formed by projecting a plurality of guided pins 26 on the lower surface of a small plate 24 that is close to a reduction-like shape in plan view of the fuel tank 2, and one of the guided pins 26 has a support arm 28. The rail 32 is linearly guided by a rail 32 fixed to the fixed wall 30.

As shown in FIG. 9, each guided pin 26 is arranged in alignment with a vertical line passing through the center of curvature of the corner portion of the fuel tank 2. The illustrated fuel tank 2 has four corners R1 to R4, and a total of four guided pins 26 (26a to 26d) are projectingly provided on the lower surface position of the small plate 24 corresponding to these corners R1 to R4. There is.

As shown in FIG. 10 (A), the rail 32 has a gutter shape with a rear end closed and a front end open having a groove having a rectangular cross section. Two entrances are provided on one side surface of the rear end of the rail 32 and an intermediate part. Three
4 and 36 are cut out so that the guided pin 26 can enter the rail 32 from either of these two inlets 34 and 36. The lower frame of the entrances 34 and 36 is shown in FIG.
As shown in (C), a stopper pin 40, which has a lower portion supported by a spring 38 and an upper portion formed in a slanting shape, is provided so that the stopper pin 40 can move up and down so that the guided pin 26 once inside the rail 32 does not come out. It has become. Further, as shown in FIG. 10B, a stopper block 42 is fixedly provided on the inner surface on one side of the front end portion of the rail 32, and the guided pin 26 moving forward in the rail 32 is brought into contact with the stopper block 42. Once stopped, in this state, when the small plate 24 is turned 90 ° in the direction of the arrow by the feeding action of the electrode wheel 46, the notch 27 of the guided pin 26 faces the stopper block 42 and the guided pin 26 does not pass. It has become acceptable.

The 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, 46 of the seam welding machine, and the electrode wheels 46 are rotated while rotating the electrode wheels 46. The peripheral flange portions 4, which were energized and abutted against each other, were resistance-welded. The fuel tank 2 advances without changing its posture when the straight line portion L1 of the peripheral flange portion 4 is seam welded as shown in FIG. At this time, the guided pin 26a moves in 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 blocked by the stopper block 42, so that the fuel tank 2 moves the electrode wheel 46 around the guided pin 26. It rotates in the direction of the arrow due to the horizontal rotation moment generated by the feeding action. When the electrode wheel 46 has finished turning around the corner R1, that is, when the fuel tank 2 has finished rotating by 90 °, another guided pin 26b enters the rail 32 through the inlet 36, and the peripheral flange portion 4 of the fuel tank 2 is inserted. The straight line portion L2 is seam welded by the electrode wheel 46 in the same manner as described above. When the straight line portion L2 is welded, the corner portion R2 is subsequently seam welded by the electrode wheel 46, and then the guided pin 26c is inserted into the inlet 34.
From inside the rail 32, the straight portion L3 is seam welded by the electrode wheel 46.

[0006]

In the conventional seam welding line automatic copying apparatus, a dedicated jig 6 is provided for each type of fuel tank 2.
Since the copying jig 22 is required, the dedicated jig 6 and the copying jig 22 must be newly manufactured every time the shape of the fuel tank 2 is changed, and in particular, the manufacturing of the copying jig 22 is expensive. Needed a long production period.

Therefore, the fuel tank 2 is supported by a robot without using the copying jig 22, and the fuel tank 2 is fed and controlled in accordance with the progress of the seam welding by the electrode wheels 46 to control the peripheral flange portion 4 of the fuel tank 2. A study has been made to obtain a desired welding line (see Japanese Patent Application Laid-Open No. 7-241684).

However, it is extremely difficult to accurately grasp the progress of seam welding by the electrode wheel 46 in real time. This is the peripheral flange portion 4 of the fuel tank 2.
Unevenness in the plate thickness, softening of the peripheral flange portion 4 due to energization between the electrode wheels 46, and further the electrode wheel 4
Since abrasion of 6 occurs, the rotation speed of the electrode wheel 46 running on the peripheral flange portion 4 does not match the actual feed distance of the peripheral flange portion 4, and the feed distance fluctuates minute by minute. is there. For the feed control of the fuel tank 2 by the robot, a method by teaching, a method of feedback control by grasping the feed speed or feed distance of the peripheral flange portion of the fuel tank 2 by the electrode wheel 46 accurately and in real time are conceivable. As described above, under the situation where the feed rate of the peripheral flange portion 4 fluctuates from moment to moment, the control of the robot is too late. In addition, if the welding line once deviates from the normal trajectory, it is not easy to quickly restore it to the original position, and errors due to control delays tend to accumulate, resulting in poor welding. There was a problem.

The 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 depending on the numerical control of the robot, and to bring about a completely new idea, namely, , The seam welding operator mechanically replaces the work contents of sending the fuel tank 2 while visually confirming the welding line, thereby creating an expensive copying jig and a complicated program for the robot, and the troublesome teaching of the robot. There is no need for work.

[0010]

The copying apparatus of the present invention focuses on the fact that the welding line by the electrode wheels can be controlled by rotationally adjusting the fuel tank in the horizontal direction. 3 will be described. 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, 48 from the bottom are shown.
The second and third plates 48b, 4 between the b and the bottom
8c, the first and second linear motion guides 52,
54 is provided. The first and second linear motion guides 52 and 54 are capable of sliding the plates 48a to 48c in a linear direction, and the lower first linear motion guide 52 and the upper second linear motion guide 54 are mutually arranged. They are arranged orthogonally. That is, the first linear motion guide 52 is an X-direction linear motion guide, and the second linear motion guide 54 is a Y-direction linear motion 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 considered that the copying control shaft 56 is arranged on the lower surface of 0.
The copying control shaft 56 is a rotation shaft of a motor whose rotation angle can be precisely controlled, and is, for example, a rotation shaft of a step motor or a servo motor. Then, it is considered that the work piece 58 to be welded, which is formed by stacking two sheet metals, is supported on the lower end of the copying control shaft 56.

While the work 58 to be welded is supported, the work peripheral portion (corresponding to the peripheral flange portion 4 of the fuel tank) is sandwiched by the electrode wheels 46, and the electrode wheels 46 are rotated to seam weld the work peripheral portions. . At this time, if the scanning control shaft 56 is rotated in either forward or reverse directions, the orientation of the workpiece 58 to be welded with respect to the electrode wheel 46 changes. When viewed from the side of the electrode wheel 46, this means that the traveling direction of the electrode wheel 46 has changed. FIG. 3 exemplifies the relationship between the rotating 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 straight line portion of the peripheral edge of the workpiece 58 to be welded (see FIG. 3). When the control axis is rotationally adjusted in the clockwise direction following the point A), the electrode wheel 46 shifts inside the workpiece 58 to be welded. Further, when the electrode wheel 46 approaches the corner, the copy control shaft 56
When 90 ° is adjusted to be rotated clockwise by 90 °, the electrode wheel 46 cuts a curve to the left at 90 ° in the traveling direction. This is the control principle of the welding line of the present invention.

Although the conventional fuel tank 2 was supported by the iron man 14, since the iron man 14 cannot support the rotational reaction force of the copying control shaft 56, 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 in which the work is supported movably in the horizontal direction while supporting the rotational reaction force as in the XY table 50. .

The above 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 of the present invention provides the sliding between the sewing machine table and the cloth at this time. The function of the hand that turns the fabric corresponds to the copying control shaft of the present invention.

The welding line automatic copying apparatus according to the present invention is an application of the above-mentioned welding line control principle, and includes support means for allowing movement in an arbitrary horizontal direction but restraining movement in a horizontal turning direction, A copying control axis having a main axis in a direction orthogonal to the movement permitting direction of the supporting means is vertically overlapped, and either one of the supporting means or the copying control axis is supported by the tip of the robot arm, and the other side is seam welded. Attach a dedicated jig that supports the workpiece that has
A sensor for detecting a deviation between the seam welding planned line of the work and the actual front end of the welding line is provided, and a control means for controlling the rotation of the copying control shaft so as to make the deviation zero based on the output from the sensor. Arranged.

The supporting means may be an XY table in which a first linear motion guide and a second linear motion guide are arranged in a space between two upper and lower portions of a three-layer plate so as to intersect each other.

In order to detect the deviation between the planned seam welding line and the actual front end of the welding line, a template having the same or similar contour as the planned welding line of the work is attached to a dedicated jig in alignment with the work and the seam welding is performed. A reference member is fixedly arranged at a position facing the contour of the template in a vertical plane that commonly includes the axis lines of a pair of upper and lower electrode wheels of the machine, and the gap distance between the contour of the template and the reference member is detected. A distance measuring sensor is provided. Then, based on the output from the distance measuring sensor, the copying control shaft is rotationally controlled so that the gap distance becomes constant during seam welding.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 4 (A), the foundation 70
Arm 8 of articulated robot 74 fixed to floor 72
A C-shaped frame 86 is attached to the tip of the No. 2 via the copying control shaft 84 and the XY table 50 as a supporting means. The copying control shaft 84 is a rotation shaft such as a step motor or a servo motor whose rotation angle can be precisely controlled, and the end rotation shaft of the robot can be used as it is.
An XY table 50 is supported on the lower end of the scanning control shaft 84. This XY table 50 is the same as that described above, and the first plate 48c from the top is the scanning control shaft 8
It is fixed to the lower end of 4. A dedicated jig 6 is fixed to the lower surface of the XY table 50, and the fuel tank 2 is positioned and fixed under the dedicated jig 6. A clamp 90 that can be moved up and down by a cylinder 88 is provided at the lower end of the C-shaped frame 80.
The clamp 84 can press and fix the lower surface of the fuel tank 2.

The XY table 50 can be replaced with another mechanism as long as it allows movement in an arbitrary horizontal direction but restrains movement in the horizontal turning direction. For example, as shown in FIG. 6 (A). The universal joint 76 is disposed 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. 6B.
8 is arranged 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 92 is fixed to the upper portion of the dedicated jig 6 as shown in FIGS. 4B and 5A and 5B. This template 92 is composed of a plate having a substantially rectangular contour of the planned welding line of the peripheral flange portion 4 of the fuel tank 2 and a contour of a similar reduced shape, and is aligned with the fuel tank 2, that is, the corresponding sides have the same direction. It is arranged horizontally so as to face.

On the other hand, a fixed arm 94 extends downward from the main body of the seam welder 44, and a reference member 96 is attached to the lower end of the fixed arm 94. This reference member 96
Are located in a vertical plane that commonly includes the axes of the pair of upper and lower electrode wheels 46, and as shown in FIG.
Is opposed to the contour of. A distance measuring sensor 98 is attached near the reference member 96 at the tip of the fixed arm 94. The distance measuring sensor 98 measures a gap distance between the contour of the template 92 and the reference member 96.

Next, the control of the scanning control shaft 84 will be described.
If the peripheral flange portion 4 of the fuel tank 2 is seam welded without rotating the copying control shaft 84, the welding line is basically a straight line. However, if it is left as it is, the welding line due to variations in the thickness of the peripheral flange portion 4, unevenness, etc. The error cannot be corrected. When the front end of the welding line deviates from the planned welding line, the interval between the reference member 96 and the contour of the template 92 changes to either wide or narrow.
This is detected by the distance measuring sensor 98, and the scanning control shaft 84 is rotationally controlled so as to restore the change in the width of the interval. Further, the welding of the corner portion of the peripheral flange portion 4 of the fuel tank 2 is also performed by the rotation of the copying control shaft 84. That is, the electrode wheel 4
At the same time that 6 passes the welding start point of the corner portion, the interval between the contour of the template 92 and the reference member 96 widens,
The distance measuring sensor 98 continuously detects the extent of the spread of the distance, and the scanning control shaft 84 is rotationally controlled by the control means (not shown) so as to restore the spread.

The scanning control shaft 84 can be controlled by means other than the template 92, the reference member 96 and the distance measuring sensor 98 described above. Generally, the seam welding planned line of the fuel tank 2 and the actual welding are performed. It suffices to have a sensor for detecting a deviation from the front end of the line and a control means for controlling the rotation of the copying control shaft 84 so as to make the deviation zero based on the output from the sensor. The distance measuring sensor 98 detects the distance between the template 92 and the reference member 96, which is synonymous with detecting the deviation between the planned seam welding line and the actual front end of the welding line. Therefore, instead of the distance measuring sensor 98, it is possible to use a sensor that directly detects the position of the front end of the welding line of the fuel tank 2.

Next, another embodiment of the present invention will be described with reference to FIG. The seam welding line automatic copying apparatus shown in FIG. 7 also uses the robot arm 82 and is basically the same as the above-described embodiment, but between the XY table 50 and the dedicated jig 6 or the template 92. The difference is that the tool changer 100 is equipped. As shown in the enlarged cross-sectional view, this tool changer 100 has a shaft 102 protruding from the dedicated jig 6 side that is detachably locked by a spring 103 and a steel ball 104. When the tool 6 is to be replaced, the steel ball 104 is retracted by vacuum so that the shaft 102 can be easily removed. By using this tool changer 100, it is possible to provide versatility from the robot arm 82 to the XY table 50, and it is effective in reducing the equipment cost and the changeover cycle time when there are many types of fuel tanks 2. Target.
In FIG. 7, 106 is a knurl roller and 108 is a cutting tool. The other parts that are substantially the same as those shown in FIGS. 4 and 5 are designated by the same reference numerals.

Although one 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 copy control shaft 8
4 is arranged on the upper side and the XY table 50 is arranged on the lower side. On the contrary, the XY table 50 is arranged on the upper side and the copying control shaft 84 is arranged on the lower side, and the dedicated jig 6 is fixed to the lower end of the copying control shaft 84. You may.

[0026]

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 copying control axis, so that the complicated program for the conventional expensive copying jig or robot is used. It becomes unnecessary, and a big rationalization effect can be exhibited. Further, since the supporting means is supported by the tip of the robot arm, the supporting means can be downsized by covering the majority of the movement range of the work with the movement of the robot arm. This is particularly large in seam welding of a large work. It will be an advantage.

[Brief description of 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 copy control shaft.

FIG. 3 is a plan view of a workpiece showing welding line copying control.

4A is a perspective view of a robot and a seam welding line automatic copying apparatus, FIG. 4B is an enlarged perspective view of the seam welding line automatic copying apparatus, and FIG. 4C is a side view of a template and a distance measuring sensor.

FIG. 5A is a side view of the seam welding line automatic copying apparatus,
(B) is a plan view of the seam welding line automatic copying apparatus.

FIG. 6A is a side view showing a modified example of the supporting means,
FIG. 9B is a perspective view showing still another modified example of the supporting means.

FIG. 7 is a perspective view of a seam welding line automatic copying apparatus according to another embodiment of the present invention.

FIG. 8 is a side view of a conventional welding line copying control device.

FIG. 9 is a plan view of a fuel tank.

10A is a perspective view of a rail, FIG. 10B is a plan view of a front end of the rail, and FIG. 10C is a vertical cross-sectional view of a rear end of the rail.

[Explanation of symbols]

 2 Fuel tank 6 Dedicated jig 44 Seam welder 46 Electrode wheel 50 XY table 74 Articulated robot 82 Arm 84 Copy control axis 90 Clamp 92 Template 96 Reference member 98 Distance measuring sensor ^ L

Claims (3)

[Claims] 1. A support means for allowing movement in an arbitrary horizontal direction, but restraining movement in a horizontal turning direction, and a copying control shaft having a main shaft in a direction orthogonal to the movement allowance direction of the support means are vertically stacked. While supporting either one of the supporting means or the copy control shaft at the tip of the robot arm, a dedicated jig for supporting a work having a portion to be seam welded is attached to the other end, and the seam welding planned line of the work is A sensor for detecting a deviation from an actual front end of the welding line is provided, and a control means is provided for controlling rotation of the copying control shaft so as to reduce the deviation to zero based on an output from the sensor. Seam welding line automatic copying device. 2. The supporting means comprises two layers above and below the three-layer plate.
The seam welding line automatic copying apparatus according to claim 1, wherein the first linear motion guide and the second linear motion guide are arranged in one gap so as to intersect each other. 3. A template having a contour that is the same as or similar to the planned welding line of the work is attached to the dedicated jig so as to be aligned with the work, and the axes of a pair of upper and lower electrode wheels of a seam welder are commonly included. A reference member is fixedly arranged at a position facing the contour of the template in a vertical plane, and a distance measuring sensor for detecting a gap distance between the contour of the template and the reference member is arranged to perform seam welding. The automatic seam welding line copying apparatus according to claim 1, wherein the copying control shaft is rotationally controlled so that the gap distance becomes constant during the operation.