JPH0780640A - Method and device for circumferential welding of cylindrical body - Google Patents

Abstract

PURPOSE:To precisely make welding start point and welding stop point coincide when circumferential welding is executed with rotating a cylindrical body. CONSTITUTION:A cylindrical body 11 is placed/supported on a pair of rotatable turning rollers 3, 4 and is turned by one of the turning roller 3. An encoder 12 is placed between turning rollers 3, 4, a position of one point on the circumference of the cylindrical body 11 is detected by the encoder 12. Also, a position of the turning rollers 3, 4 are detected by encoders 9, 10. And a diameter of the cylindrical body 11 is calculated by these position and the diameter of the turning rollers 3, 4, and a circumferential length of the cylindrical body 11 is calculated from the diameter. Further, from the circumferential length a number of revolution of a turning roller drive motor 7 required for one revolution of the cylindrical body 11 is calculated. At circumferential welding, a number of revolution of the motor 7 is counted from start of welding, when its accumulated number of revolution reaches the required the number of revolution calculated, it is judged the cylindrical body is turned one revolution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a peripheral welding method and apparatus used for joining welded cylindrical pipes or overlay welding on the outer peripheral surface of a thin-walled cylindrical body, and more particularly to fixing a welding torch. The present invention relates to a method and apparatus for circumferentially welding a cylindrical body in which the entire circumference is welded by rotating the cylindrical body.

[0002]

2. Description of the Related Art Generally, when joining cylindrical bodies such as pipes, the cylindrical bodies are butted to each other and the outer circumference of the butted portion is welded over the entire circumference. Further, when the thickness of the cylindrical body is insufficient, overlay welding is applied to the entire outer peripheral surface thereof. Even in that case, circumferential welding is performed on the cylindrical body.
As such a method of circumferentially welding the entire circumference of the cylindrical body, there are a method of moving the welding torch along the outer circumference of the cylindrical body, and a method of fixing the welding torch and rotating the cylindrical body instead. However, when the cylindrical body has a large diameter, a method of rotating the cylindrical body is often adopted.
In that case, the cylindrical body is usually placed on a pair of parallel turning rollers, and is rotated by rotationally driving one of the turning rollers by a motor.

When performing such circumferential welding, it is required that the welding start point and the stop point on the outer peripheral surface of the cylindrical body be exactly aligned. That is, if welding is stopped before the starting point of welding, a part of the entire circumference will remain unwelded. On the contrary, if the welding is continued even after the welding start point is exceeded, a part of the entire circumference will be doubly welded. Then, when such a welding residual portion or a welding overlapping portion occurs, a difference occurs in strength or outer diameter of the entire circumference of the cylindrical body, and the quality thereof deteriorates. Therefore, in order to perform high-quality circumferential welding, it is necessary to accurately stop the welding when the welding start point is reached during the rotation of the cylindrical body. However, when rotating the cylinder with the turning roller as described above, it is not possible to directly measure the rotation angle of the cylinder, so it is necessary to know where the welding start point is located during the rotation. Is difficult.

Therefore, when circumferential welding is performed while rotating the cylindrical body by the turning roller as described above, conventionally, the circumferential length is obtained from the diameter of the cylindrical body to be welded, and further, it is incorporated in the drive motor. The speed of the motor required to make one revolution of the cylinder is calculated from the reduction ratio of the speed reducer and the diameter of the turning roller, and is input to the control system of the motor. When the motor rotates until it is judged that the body has just made one or several rotations, the motor is stopped and welding is stopped.

[0005]

However, in such a method, it is necessary to actually measure the diameter of the cylindrical body to be circumferentially welded. The diameter of a cylindrical pipe such as a pipe is often shown as a nominal diameter, but the nominal diameter is often different from the actual diameter due to manufacturing errors or the like. Therefore, in order to accurately perform circumferential welding of the cylindrical body, it is absolutely necessary to measure the diameter of the cylindrical body each time. Therefore, it is difficult to automate the circumferential welding of the cylindrical body. Moreover,
Ordinary cylinders rarely have an exact circular cross section, and often have a slightly elliptical shape. In such a case, even if the diameter of the cylinder is actually measured, it is extremely difficult to accurately determine the length of the circumference.
In addition, it is inevitable that such an actual measurement involves an error. Even if the error itself is small, the error will be accumulated especially when performing multi-layer circumferential welding.
Therefore, if the welding stop point is determined based on the measured value, the position may deviate significantly from the welding start point. Furthermore, each time the cylinder to be welded around changes, its diameter is measured, and the required number of rotations of the motor is calculated from that diameter.
It is troublesome to input it into the circumference welding device.

The present invention has been made in view of the above circumstances, and an object thereof is to perform circumferential welding while rotating a cylindrical body by a turning roller.
The object is to provide a method and apparatus for circumferential welding of a cylindrical body, by which the diameter of the cylindrical body can be obtained only by setting the cylindrical body on the circumferential welding apparatus, and thereby easily automating. Another object of the present invention is to provide a circumferential welding method and apparatus capable of matching the welding start point and the welding stop point even when the cylindrical body is deformed.

[0007]

In order to achieve this object, in the present invention, attention is paid to the fact that two positions on the outer circumference of the cylindrical body are obtained from a pair of turning rollers supporting the cylindrical body, By utilizing this, the diameter of the cylinder is calculated. That is, the method for circumferentially welding a cylindrical body according to the present invention is a position scale for detecting the contact position by contacting the outer peripheral surface of the cylindrical body at a predetermined position apart from both of the pair of turning rollers supporting the cylindrical body. Is placed, and while the position scale is in contact with the outer peripheral surface of the cylindrical body, one turning roller is rotationally driven by the motor to rotate the cylindrical body, and the position scale is arranged near the outer peripheral surface of the cylindrical body. The welding torch is started to start welding, and the diameter of the cylindrical body is calculated based on the detection value by the above-mentioned position scale, the center position of the pair of turning rollers and the diameter thereof, and further in that manner. The required number of rotations of the motor required to rotate the cylinder once is calculated from the calculated diameter, and the cumulative number of rotations of the motor counted from the start of welding to that time is calculated. Is characterized in that so as to stop the welding when it reaches the required rotational speed value obtained by multiplying a predetermined circumferential welding times. In that case, one of the cylinders
It is desirable to calculate the diameter of the motor a plurality of times during rotation, and use the average value as the correct diameter of the cylinder to determine the required number of rotations of the motor. In that case, the next diameter is calculated at time intervals according to the diameter calculated at that time. When performing multi-layer overlay welding,
At the first rotation of the cylindrical body, that is, during the circumferential welding of the first layer, the diameter of the cylindrical body is obtained as described above, and the subsequent circumferential welding is performed using the result. In that case, the welding torch is moved by an amount corresponding to the welding thickness or the welding width when it is determined that the cylinder has just made one revolution. Further, the circumferential welding apparatus for a cylindrical body according to the present invention includes a position scale as described above, a calculator for performing necessary calculations from the detected value by the position scale, the center position and diameter of the turning roller, and the like from the start of welding. It is characterized by comprising a tachometer that measures the cumulative number of revolutions of the motor, and a controller that outputs a control signal for the welding torch by comparing the value measured by the tachometer with the value calculated by the calculator. There is. It is desirable that at least one of the pair of turning rollers be positionally adjustable. In that case, a second position scale for detecting the position of the turning roller is provided, and the detected value by the position scale is input to the arithmetic unit.

[0008]

In the circumferential welding apparatus in which the cylindrical body is placed and rotated on the pair of turning rollers as described above, generally,
The center position of each turning roller and its diameter are known. Since the cylindrical body is in line contact with those turning rollers at the same time, the contact position, that is, two points on the outer circumference of the cylindrical body are determined. Therefore, if a position scale is arranged at a position distant from those turning rollers and the position of another one point on the outer circumference of the cylinder is measured by the position scale, three points on the outer circumference of the cylinder will be measured. It will be required and the diameter can be calculated. Then, from the diameter, the length of the outer circumference of the cylinder is obtained, and from the circumference, the number of rotations of the turning roller required to rotate the cylinder once, that is, the required number of rotations of the motor is obtained. Therefore, while rotating the cylinder, welding is started from a certain position, the number of rotations of the motor from the start of welding is counted, and the cumulative number of rotations is calculated as described above. If the welding is stopped when the number reaches an integral multiple of the number, the starting point and the stopping point of the welding will be exactly coincident with each other, and it is possible to prevent a welding residual portion and a welding overlapping portion from occurring. In that case,
The diameter is calculated multiple times during the rotation of the cylinder,
If the required number of rotations of the motor is determined from the average value, welding can be accurately stopped after one or several revolutions of the cylinder even when the cross section of the cylinder is slightly elliptical. Become so. Further, if the spacing between the pair of turning rollers is adjustable, it becomes possible to stably support even cylindrical bodies having significantly different diameters. Also in this case, the position of the turning roller is detected by the second position scale, and the detected value is input to the arithmetic unit, so that the same accurate control can be performed.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. In the drawings, FIGS. 1 and 2 show an embodiment of the method for circumferentially welding a cylindrical body according to the present invention, FIG. 1 is a side view thereof, and FIG. 2 is a front view thereof. 3 and 4 are flowcharts of the control performed in the circumferential welding method. As is apparent from FIGS. 1 and 2, the pedestal 2 of the circumference welding apparatus 1 is
A plurality of driving turning rollers 3, 3, ... And a plurality of driven turning rollers 4, 4 ,. The turning rollers 3, 3, ... And 4, 4, ... Have the same diameter and are integrally connected by connecting shafts 5, 6 which are parallel to each other. The connecting shafts 5 and 6 are attached to the brackets 5a and 6a.
Are rotatably supported at the same height. The connecting shaft 5 of the drive turning rollers 3, 3, ... Is rotatably driven by a motor 7 incorporating a speed reducer. A rotary encoder 8 is connected to the motor 7 as a tachometer for detecting the rotation speed. Also,
Each of the turning rollers 3, 3, ... And 4, 4, ... Brackets 5a, 6 for rotatably supporting the connecting shafts 5, 6 thereof.
Along with a, it can be moved along the upper surface of the gantry 2 in a direction orthogonal to the rotation axis (left-right direction in FIG. 2), and the interval between them can be adjusted. The amount of movement from the initial position is detected by the linear encoders 9 and 10 connected to the brackets 5a and 6a, respectively. The brackets 5a and 6a are adapted to move in the opposite directions by interlocking with each other by a feed screw mechanism or the like. Therefore, one bracket 5
For example, when a is moved rightward in FIG. 2 by a certain amount, the other bracket 6a is moved leftward in the opposite direction by the same amount.

The cylindrical body 11 to be circumferentially welded is mounted and supported on turning rollers 3, 3, ... And 4, 4 ,.
And 4, 4, ... Then, the motor 7 drives the turning rollers 3, 3, ...
By rotating the motor, it is rotated in the direction of arrow Z in FIG. Further, a linear encoder 12 as a first position scale is vertically installed on the gantry 2 at an intermediate position equidistant from the turning rollers 3 and 4. A small-diameter detection roller 13 is attached to the upper end of the encoder 12, and the roller 13
However, a spring provided inside the encoder 12 is always biased in a direction projecting upward. Therefore, when the cylindrical body 11 is placed on the turning rollers 3 and 4, the detecting roller 13 is pushed down by the cylindrical body 11, and the roller 13 is held in contact with the lower surface of the cylindrical body 11. The linear encoder 12 is adapted to detect the amount of depression of the detection roller 13 when it is pushed down in this way.

On the other hand, above the cylindrical body 11, a welding torch 14 for welding the outer peripheral surface of the cylindrical body 11 is provided near the position facing the linear encoder 12. The welding torch 14 is supported by a jig (not shown) and is movable between a position close to the outer peripheral surface of the cylindrical body 11 and a position sufficiently distant therefrom. Further, even at a position close to the outer peripheral surface of the cylindrical body 11, the position of the welding torch 14 is in the vertical direction and in the cylindrical body 11
It can be adjusted in the axial direction. The welding torch 1
The operation of No. 4 is controlled by a command signal output from the controller 15, and welding is started and stopped and the position of the welding torch 14 is adjusted according to the instruction.
Further, the motor 7 that rotationally drives the turning roller 3 also
It is designed to be controlled by a signal from the controller 15. The signal output from the calculator 16 is input to the controller 15. The calculator 16 includes a reduction ratio of a reduction gear installed in the motor 7,
Diameter of turning rollers 3 and 4, initial position of its center,
That is, the distance and the height of the center of the turning rollers 3 and 4 from the linear encoder 12 before moving, the initial height of the linear encoder 12 before contacting the cylindrical body 11, and the like are set in advance, and It is possible to set the welding speed and the number of times of circumferential welding,
Further, output signals from the encoders 8, 9, 10, 12 are input. The arithmetic unit 16 performs a predetermined arithmetic operation based on those set values or input values. The arithmetic unit 16 is composed of a microcomputer.

Next, with reference to the flow charts of FIGS. 3 and 4, the control procedure performed in the circumferential welding apparatus 1 thus configured will be described together with the operation of the circumferential welding apparatus 1. When circumferential welding of the cylindrical body 11 is to be performed, first, the turning rollers 3, 3, ... And 4, 4, ... Are appropriately moved according to the approximate diameter of the cylindrical body 11, and the interval therebetween is set to an appropriate size. Set to Then, the cylindrical body 11 is adjusted and placed on the turning rollers 3, 3, ... And 4, 4, ... so that the welded portion 11 a thereof is located at a position facing the welding torch 14. When the cylindrical body 11 is placed in this way, the detection roller 13 at the upper end of the linear encoder 12 comes into contact with the lower surface of the cylindrical body 11,
The roller 13 is pushed down. In this state, it may be replaced with another cylindrical body due to the work, so
Control has not started yet. When it is decided to perform circumferential welding on the cylindrical body 11, the optimum welding speed v determined by the material of the cylindrical body 11 and the groove shape of the welded portion 11a is set in the calculator 16. Further, the number of times Y of measuring the diameter to be performed during one rotation of the cylindrical body 11 and the number of times P of circumferential welding are set. The initial position of the center of each turning roller 3, 4 and its diameter, the installation position of the linear encoder 12, and the initial height of the detection roller 13 before coming into contact with the cylindrical body 11 are preset in the calculator 16. Has been done. Then, control is started in that state.

When the control is started, first, step s1
At, various data set in the arithmetic unit 16 are read. Next, in step s2, the outer peripheral length m of the drive turning roller 3 that rotates while the motor 7 rotates once is obtained, and the rotational speed (= v / m) of the motor 7 is calculated from the length m and the welding speed v. Is determined. Then, a command signal for operating the motor 7 at the rotation speed is output. Thus, the motor 7 starts rotating at a constant speed. When the motor 7 operates, the driving turning roller 3 is rotationally driven via the connecting shaft 5, and the cylindrical body 11 frictionally contacting with the driving turning roller 3 rotates in the direction of arrow Z in FIG. The peripheral speed is equal to the peripheral speed of the driving turning roller 3, and the length is m per one rotation of the motor 7. Next, in step s3, a command signal for moving the welding torch 14 to a position close to the outer peripheral surface of the cylindrical body 11 and starting its operation is output. Thereby, the circumferential welding of the cylindrical body 11 is started.

At the same time when the circumferential welding is started in this way, at step s4, the linear encoders 9 and 10 are connected.
The output value of is read. The initial positions of the centers of the turning rollers 3 and 4 are known. Further, even if the turning rollers 3 and 4 are moved, the height of the center does not change. Then, as described above, those values are set in the calculator 16. Therefore, the linear encoder 9,
By reading the output value of 10, the center position of the turning rollers 3 and 4 can be obtained. That is,
The center position of each turning roller 3, 4 at that time is obtained by the pair of linear encoders 9, 10 as a second position scale that detects the amount of movement of each turning roller 3, 4 from the initial position. In step s5, the turning rollers 3 and 4 thus obtained are obtained.
Distances A, A between the respective center positions and the centers of the detection rollers 13 of the linear encoder 12 (see FIG. 5).
Is calculated. Next, in step s6, the integer flag F is set to 1. Furthermore, in step s7, the output value of the linear encoder 12, which is the first position scale, is read, and based on that value, step s8
At the distance C from the upper surface of the gantry 2 to the contact position between the detection roller 13 of the encoder 12 and the cylindrical body 11 in FIG.
(See) is calculated. In this way, the distance between each of the turning rollers 3 and 4 and the linear encoder 12 and the contact position between the cylindrical body 11 and the detection roller 13 are obtained. The height and diameter of each turning roller 3 and 4 are known. Therefore, in step s9, the diameter D of the cylindrical body 11 is calculated from these values. The calculation method will be described later.

When the diameter D of the cylindrical body 11 is calculated, in step s10, the virtual outer peripheral length πD (π is the circular constant) of the cylindrical body 11 is calculated from the diameter D obtained at that time, and in step s11. , The time t (= πD / v) required to weld the outer circumference is calculated. Then, in step s12, a measurement time interval S (= t / Y) for performing position detection by the linear encoder 12 and calculation of the diameter D based on the welding time t and the number of times of measurement Y set in the calculator 16. ) Is determined. Further, in step s13, the average value D ₀ of the diameters D obtained up to that time is calculated, and in step s14, the required rotation of the motor 7 required to rotate the cylindrical body 11 once from the average diameter D _0. Number N (= πD ₀ / m)
Is calculated. In step s15, the rotation speed of the motor 7 output from the rotary encoder 8 is counted, and the cumulative rotation speed Σn of the motor 7 from the start of welding to that time is obtained.

Next, in step s16, the cumulative rotation speed Σn of the motor 7 is compared with the required rotation speed N calculated in step s14. When the cumulative rotation speed Σn has not reached the required rotation speed N, the routine proceeds to step s17. move on. In step s17, the state is maintained for the time interval S calculated in step s12, and after the time S has elapsed, the process returns to step s7. Thus
After the welding is started, until the cylindrical body 11 makes one rotation,
The flow from step s7 to step s17 is repeated. Therefore, the position detection and the calculation of the diameter D of the cylindrical body 11 are performed again by the linear encoder 12 after the lapse of the time S determined based on the diameter D of the cylindrical body 11 measured last time, and the next The time interval S until the measurement is determined. And the time interval S
The average value is calculated by summing up the diameters D measured in 1. and dividing the sum by the number of measurements performed so far. In this way, the diameter D is measured Y times while the cylindrical body 11 makes one rotation, and the average value D ₀ is obtained.
The average value D ₀ is, when the cylindrical body 11 makes one rotation,
It becomes the average diameter of the cylindrical body 11. Therefore, even when the cross section of the cylindrical body 11 is distorted in an elliptical shape, the outer peripheral length thereof is accurately obtained, and the necessary rotation speed N of the motor 7 determined based on it is accurate.

When the cylindrical body 11 rotates exactly once from the start of welding, the cumulative rotation speed Σn of the motor 7 becomes equal to the required rotation speed N. At that time, the process proceeds from step s16 to the next step s18. In step s18, it is determined whether the cumulative rotation speed Σn at that time is equal to the required rotation speed N multiplied by an integer F. The integer F is set to 1 in step s6 as described above.
Therefore, when the cumulative rotation speed Σn is equal to the required rotation speed N, it is determined in step s18 that the condition is satisfied. Then, the process proceeds to step s19. In step s19, the integer F and the welding number P set in the calculator 16 are compared. When the number of welding times P is set to 2 or more, the number of welding times P is different from the integer F, and thus the process proceeds to step s20. In this way
It is determined that the cylindrical body 11 has made exactly one rotation from the start of welding. At that time, the first circumference welding of the cylindrical body 11 is completed, and the welding starting point on the cylindrical body 11 is the welding torch 14.
The position is opposite to. Therefore, in step s20, a signal for moving the welding torch 14 in the axial direction of the cylindrical body 11 by the welding width of the welding torch 14 is output. As a result, the welding torch 14 moves to a position adjacent to the welding portion on the first turn. During that time, the rotation of the cylindrical body 11 is continued. Therefore, the circumferential welding of the second round is started so as to be adjacent to the welded portion of the first round.

The welding torch 14 is completed after the first circumference welding is completed.
When a signal for moving the
At 1, the integer flag F is incremented by 1. Therefore, the integer F is the number 2 representing the number of times of circumferential welding. Then, the process returns to step s15, and the measurement of the cumulative motor rotational speed Σn is continued. At this time, the cylindrical body 11
Has passed one rotation since the start of welding and has entered the second rotation, the cumulative rotation speed Σn of the motor 7 is larger than the rotation speed N required to rotate the cylindrical body 11 once. Therefore, step s16 is passed, and the process proceeds to step s18. Then, in step s18, the cumulative rotation speed Σn and the required rotation speed N
Is multiplied by an integer F, that is, doubled, and the cumulative rotational speed Σ
When n has not reached twice the required rotation speed N, the process returns to step s15. In this way, the cylindrical body 11
In the second rotation of, the rotation state of the cylindrical body 11 is monitored by using the required rotation speed N of the motor 7 obtained in the first rotation. When the cumulative number of revolutions Σn of the motor 7 becomes equal to twice the required number of revolutions N, it is judged that the cylindrical body 11 has just made two revolutions from the start of welding, and the welding torch 14 has come to face the welding start point of the second lap. Step s
At 19, the integer F of 2 at that time is compared with the set circumference welding number P. If they do not match, the process proceeds to step s20, and a signal for further moving the welding torch 14 is output. In addition, 1 is added to the integer F in step s21. Thus, the cylindrical body 11
Circumferential welding of the third lap is started.

In this manner, the circumferential welding of the cylindrical body 11 is repeated until the integer F, which increases by 1 each time the cylindrical body 11 makes one revolution, becomes equal to the set number of circumferential welding P. When the cylindrical body 11 is circumferentially welded the set number of times P and the welding torch 14 reaches a state where it faces the circumferential welding start point on the circumference of the cylindrical body 11, the cumulative number of revolutions Σn of the motor 7 is required. The number of revolutions N becomes an integer F times, and the integer F becomes equal to the set number of times of circumferential welding P. Therefore, step s
It is identified at 18 and step s19. Then, at that time, the process proceeds to step s22. Step s
At 22, a welding stop signal is output. As a result, a command signal for stopping the operation is sent from the controller 15 to the welding torch 14, and the circumferential welding is stopped. Further, in step s23, the motor stop signal is output and the motor 7 is stopped. Thus, the circumferential welding of the cylindrical body 11 by the circumferential welding device 1 is completed. The circumferential welding stop point in that case exactly coincides with the welding start point. Therefore, no welding residue or weld overlap is formed on the cylindrical body 11.

As described above, in this circumferential welding method,
While rotating the cylindrical body 11, the diameter measurement is performed Y times during the one rotation, and the necessary rotation speed N of the motor 7 is determined assuming that the average value is the correct diameter D of the cylindrical body 11. Therefore, even when the cross section of the cylindrical body 11 is elliptical, the welding start point and the welding stop point can be accurately matched. Further, if the cylindrical body 11 is distorted in this way, the position of the lower surface of the cylindrical body 11 will fluctuate up and down during its rotation, but the detection roller 13 of the linear encoder 12 is attached upward by a spring. Since it is biased, it is always kept in contact with the lower surface of the cylindrical body 11. Therefore, the diameter of the cylindrical body 11 is reliably measured.

The diameter of the cylindrical body 11 is calculated, for example, as follows. Since the driving turning roller 3 and the driven turning roller 4 are moved in the opposite directions by the same amount, the distance from the driving turning roller 3 to the encoder 12 is always equal to the distance from the driven turning roller 4 to the encoder 12. Therefore, the distance is set to A as shown in FIG. The radius of each of the turning rollers 3 and 4 is r, and the radius of the cylindrical body 11 is R.
Further, the height difference between the contact point between the cylindrical body 11 and the encoder 12 and the straight line connecting the centers of the turning rollers 3 and 4 is H. When the cylinders 11 are placed on the turning rollers 3, 4, they come into line contact with each other. Then, the contact line is located on the straight line connecting the centers thereof. Therefore, the following equation holds. (R + r) ² = (R + H) ² + A ^{2 From} this equation, 2R = (H ² + A ² −r ² ) / (r−H) And since the diameter D of the cylindrical body 11 is 2R, The diameter D can be determined.

As described above, the diameters of the driving turning roller 3 and the driven turning roller 4 are equal to each other, and they are arranged at the equal height position, and the linear encoder 12 is at a position equidistant from the turning rollers 3 and 4. The diameter D of the cylindrical body 11 when it is positioned at
Is very easy to find. Therefore, when carrying out this circumferential welding method, it is desirable to make such setting. However, even when the driving turning roller 3 and the driven turning roller 4 have different diameters and are arranged at arbitrary positions, by using the linear encoders 9, 10, 12 as described above, Similarly, the diameter D of the cylindrical body 11 can be obtained. In that case, as shown in FIG. 6, the radius of the driving turning roller 3 is r ₁ , the coordinates of its center are (x ₁ , y ₁ ), the radius of the driven turning roller 4 is r ₂ , and its center is Is (x ₂ , y ₂ ), the radius of the detection roller 13 of the linear encoder 12 is r ₃ , and the center coordinate is (x ₃ , y ₃ ). The radius of the cylindrical body 11 is R, and the coordinates of its center are (X, Y). Then, the following equation holds. ^{_{(X-x 1) 2 +}} (Y-y 1) 2 = (R + r 1) 2 (X-x 2) 2 + (Y-y 2) 2 = (R + r 2) 2 (X-x 3) 2 + (Y−y ₃ ) ² = (R + r ₃ ) ² Here, the coordinates (x ₁ , y ₁ ), (x ₂ , y ₂ ), (x ₃ ,
y ₃ ) can be obtained by detecting the amount of movement from the initial position by the position scale of the linear encoders 9, 10, 12, etc. Further, the radii r ₁ , r ₂ , r ₃ of the rollers ₃ , ₄ , ₁₃ are known. Therefore, the unknowns R, X, and Y are obtained by the above-described three equations, and the diameter D of the cylindrical body 11 can be obtained from the obtained radius R.

In this way, the turning rollers 3, 4
The diameter D of the cylindrical body 11 can be obtained by measuring the position of one point on the cylindrical body 11 distant from any of the above. Moreover, the diameter measurement can be performed even while the cylindrical body 11 is rotating. Therefore, it is possible to accurately match the starting point and the stopping point of the circumferential welding. Then, in the circumferential welding, the cylindrical body 11 is turned to the turning roller 3,
It can be done automatically just by installing it on the 4. Therefore, even in the circumferential welding of various cylindrical bodies having different diameters, the circumferential welding can be performed extremely efficiently.

In the above embodiment, the cylindrical body 11
Although the multi-layer circumferential welding method in which the welded portion is displaced in the axial direction of the cylindrical body 11 every one rotation of the above, the circumferential welding method according to the present invention is applicable to the multi-layer overlay welding in which the welded portions are overlapped and welded. Can be applied. In that case, the measured rotation diameter N of the motor 7 is determined by correcting the measured diameter D of the cylindrical body 11 according to the welding thickness, and the welding torch 14 is provided with the welding thickness for each rotation of the cylindrical body 11. Just move it upwards. Further, in the above embodiment, the control signal of the welding torch 14 is output when it is determined that the cylindrical body 11 has just made one revolution. However, when there is a response delay in the operation of the welding torch 14, It goes without saying that the control signal is output immediately before the cylinder 11 makes one complete rotation in consideration of the response delay.

[0025]

As is apparent from the above description, according to the present invention, the position of one point on the outer circumference of the cylindrical body placed on the pair of turning rollers is detected, and the position and each turning are detected. Since the diameter of the cylindrical body is calculated from the position and the diameter of the roller, the diameter can be measured during the circumferential welding of the cylindrical body, and one rotation of the cylindrical body can be accurately detected. be able to. Therefore, even when circumferential welding is performed on various cylindrical bodies having different diameters, the start position and the stop position of the welding can be accurately matched, and the occurrence of a weld residual portion or a weld overlapping portion is prevented. High quality circumferential welding can be performed. Further, in this way, it becomes possible to automatically perform circumferential welding on various cylindrical bodies, so that the efficiency is remarkably improved. And
By measuring the diameter of the cylinder several times during one rotation of the cylinder and processing the average value as the correct diameter, even when the cylinder is deformed into an ellipse or the like, One rotation can be accurately detected. Therefore, accurate circumferential welding can be performed on such a cylindrical body.

[Brief description of drawings]

FIG. 1 is a side view showing an implementation state of a method for circumferentially welding a cylindrical body according to the present invention.

FIG. 2 is a cutaway front view of the embodiment as viewed in the direction of arrow X in FIG.

FIG. 3 is a first flowchart of control performed in the circumferential welding method.

FIG. 4 is a second flowchart of control performed in the circumferential welding method.

FIG. 5 is an explanatory diagram for explaining a method of calculating a diameter of a cylindrical body, which is performed in the circumferential welding method.

FIG. 6 is an explanatory diagram illustrating a method of calculating the diameter of a cylindrical body, which is performed in a general case of the circumferential welding method according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 circumference welding device 2 mount 3 drive turning roller 4 driven turning roller 7 drive motor 8 rotary encoder (tachometer) 9 linear encoder (second position scale) 10 linear encoder (second position scale) 11 cylindrical body 12 linear encoder (First position scale) 14 Welding torch 15 Controller 16 Computing unit

Claims (7)

[Claims] 1. A cylindrical body is placed on a pair of turning rollers arranged in parallel at appropriate intervals, and one of the turning rollers is rotated by a motor to rotate the cylindrical body. A method of welding a cylinder around its entire circumference by activating a welding torch disposed near the outer peripheral surface of the cylinder; separating from any of the turning rollers. A position scale that contacts the outer peripheral surface of the cylindrical body and detects the contact position is placed at a predetermined position, and the cylindrical body is rotated with the position scale contacting the outer peripheral surface of the cylindrical body. And start welding, and when calculating the diameter of the cylindrical body based on the detected value by the position scale, the center position of each of the turning rollers and the diameter thereof. In essence, the required number of rotations of the motor required to rotate the cylinder once is calculated from the calculated diameter, and the number of rotations of the motor from the start of welding to that time is counted to calculate the cumulative number of rotations. A method for circumferentially welding a cylindrical body, comprising: stopping the welding when a value obtained by multiplying the required number of revolutions by a predetermined number of times of circumferential welding is reached. 2. During one revolution of the cylinder, the detection of the contact position by the position scale and the calculation of the diameter of the cylinder based on the detection are performed a plurality of times at time intervals corresponding to the diameter calculated at that time, The circumferential welding method according to claim 1, wherein the required number of rotations of the motor is determined based on an average value of the diameters. 3. The rotation state of the cylinder after the second rotation is monitored based on the diameter obtained at the first rotation of the cylinder, and it is determined that the cylinder has just rotated once. When the welding is performed, the welding torch is moved in accordance with the welding thickness or the welding width to perform the multi-layer circumferential welding of the cylindrical body, the circumferential welding method according to claim 1 or 2. 4. A driving turning roller that makes frictional contact with the outer peripheral surface of the cylindrical body and is rotated by a motor to rotate the cylindrical body, and is arranged in parallel with the driving turning roller at an appropriate interval. And a driven turning roller that supports the cylindrical body together with the driving turning roller, and a welding torch that is disposed near the outer peripheral surface of the cylindrical body and that welds the outer peripheral surface of the cylindrical body. In the circumferential welding apparatus, a position scale arranged at a predetermined position apart from each of the turning rollers and for detecting the contact position by contacting the outer peripheral surface of the cylindrical body, and a detection value by the position scale. , The diameter of the cylindrical body was calculated based on the center position and the diameter of each of the turning rollers, and was further calculated in this way. An arithmetic unit that calculates the required number of rotations of the motor required to rotate the cylindrical body once from the diameter, a tachometer that counts the number of rotations of the motor from the start of welding to that time, and welding by the welding torch. While instructing to start,
When the cumulative number of revolutions of the motor measured by the tachometer reaches a value obtained by multiplying the required number of revolutions calculated by the calculator by a predetermined number of times of circumferential welding, a controller that instructs the stop of the welding, A peripheral welding device for a cylindrical body. 5. The driving turning roller and the driven turning roller have the same diameter and are arranged at the same height position, and the position scale is arranged at an intermediate position equidistant from the turning rollers. The peripheral welding device according to claim 4, wherein: 6. At least one of the drive turning roller and the driven turning roller is positionally adjustable, and a second position scale for detecting the position of the turning roller is provided, and the second position scale is provided. The peripheral welding apparatus according to claim 4 or 5, characterized in that the detected value according to (4) is input to the arithmetic unit. 7. The welding torch is movable by an amount corresponding to a welding thickness or a welding width by the welding torch, and the controller determines that the cylindrical body has just rotated an integral number of times from the start of welding. 7. The peripheral welding apparatus according to claim 4, wherein a signal for moving the welding torch is generated when the circumferential welding apparatus is operated.