JPH08281434A - Method and equipment for groove copying - Google Patents

Abstract

PURPOSE: To prevent the deterioration of the precision to detect the groove position by the fluctuation of the distance of an eddy current type displacement sensor to a base metal by fixing the center position of a welding torch at the middle point In the Z-direction between a first eddy current type displacement sensor and a third eddy current type displacement sensor. CONSTITUTION: A set of first and second sensors are simultaneously driven in the groove width direction (z) so that the difference signal of the detected signals from first and second eddy current type displacement sensors 23a, 23b agrees with the difference signal of the detected signals from third and fourth eddy current type displacement sensors 24a, 24b. The first, second, third and fourth sensors 23a, 23b, 24a, 24b are driven so that the distance from the upper surface of a first member 1a to be welded to the oblique side of the groove immediately below the first sensor 23a agrees with the distance from the upper surface of a second member 1b to be welded to the oblique side of the groove immediately below the third sensor 24a. The first to fourth sensors are positioned where the groove center line is at the middle point between the first and third sensor 23a, 24a. Thus, the welding center of the welding torch is positioned at the middle point in the (z) direction of the first sensor 23a and the third sensor 24a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to groove profile welding for detecting a groove width and automatically setting a welding center of a welding torch at the center thereof.

[0002]

2. Description of the Related Art TIG (Tungsten Inert Gas) arc welding, for example, is used for groove profile welding. Currently, in manufacturing structures such as shipbuilding, construction, bridges, and tanks using steel materials, there is a strong demand for fully automated welding processes and robotization. The most important task in carrying out these is the technology for detecting the groove position and the width in order to set the welding at the proper position, the proper width and the proper height.

In arc welding, the high heat generated by the arc is used to melt and solidify the filler metal and the base metal (the material to be welded that constitutes the groove) and join them, so that heat is applied before the start of welding and during welding. The groove is deformed due to the strain due to the change in the groove position, width, and height. Therefore, the groove position is detected and the welding
To perform groove tracking control that automatically sets the welding center of
It is necessary to detect the groove position, width, height, etc. as close to the arc as possible.

In the groove profile control disclosed in Japanese Patent Application Laid-Open No. 62-230476, as shown in FIG. 8 (a), the torch 4 is moved in the groove width direction between the base materials 1a and 1b. Swing (34)
Let it. Due to this swing, the lengths of the welding wire (the swing center position 3, the swing end positions 35, 36) and the arc 33 are swung by the torch 4 as shown in FIG. 8 (b). Right edge (35)
And near the left end (36). The groove contour control disclosed in Japanese Patent Laid-Open No. 62-230476 pays attention to the phenomenon that the welding current changes in the process of the swing of the torch 4 from the left end to the right end and from the right end to the left end.
Based on the welding current difference SR = IR1-IR2 on the inner side of m and the welding current difference SR = IL1-IL2 on the inner side of 1 mm from the left end, the groove (center) position is estimated and calculated from the value of SR-SL and moved to this position. SR + by shifting the moving center, that is, the welding center
The root interval (groove width) is estimated and calculated from the value of SL, and the swing width is adjusted to this interval. Since the groove position and width are detected based on the arc current value, the detection position is the arc position (torch position), and the gap between the groove width detection position and the torch position (groove). There is no misalignment in the direction of extension.

In Japanese Patent Laid-Open No. 55-30339, a slit light image having a rectangular cross section is projected at an intersection, that is, a corner of two intersecting base materials, and a slit light image on the two base materials is photographed. From the above slit optical image shape, there is disclosed a copying control for detecting a contact position of two base materials, that is, a welding line and positioning a welding torch there.

However, the groove detecting method for detecting the groove width based on the arc current value, which is disclosed in Japanese Patent Laid-Open No. 62-230476, increases the change in the arc current value. Therefore, the swing width of the torch must be increased. However, when the plate thickness is thin, it is necessary to stop the swing up to the shoulder portion 37 shown in FIG.
Since the change in the arc current value is small, it becomes difficult to detect the groove width based on the arc current value.

The optical groove detection disclosed in the above-mentioned Japanese Patent Laid-Open No. 55-30339 is not equipped with a television camera, a slit light source, and a protective plate for preventing their damage because they occupy a relatively large space. It's difficult. In addition, the image processing for cutting out the slit light image in the image and the shape recognition and the calculation processing for calculating the welding line from the shape of the slit light image are complicated, and the development and equipment thereof are expensive.

In order to solve this problem, the applicant of the present invention arranges a pair of eddy current type displacement sensors with a groove center line in between, and each sensor is opposed to a groove edge, and both sensors are arranged. A method has been presented in which both sensors are simultaneously driven in the same direction so as to match the detection distance (the distance from the sensor to the groove slope) and the groove center position is detected (JP-A-6-335773). According to this, since the eddy current displacement sensor suitable for measuring the distance is used, the groove can be accurately detected, the control system is simplified, and the scale is small and the cost is low. The system can be configured.

[0009]

By the way, as described above, the method using a pair of eddy current type displacement sensors has a pair of materials to be welded opposite to each other (base metal; a groove is present between them).
And the distance between the pair of sensors is constant. Therefore, the sensor pair is mounted on a carriage equipped with a magnet roller and made to follow the base material. However, since the magnet roller is in direct contact with the base material, if dust is floating on the surface of the base material or if the surface is uneven, the distance between the sensor pair and the base material fluctuates, which causes Position detection accuracy decreases.

An object of the present invention is to prevent a decrease in groove position detection accuracy due to a distance variation of an eddy current displacement sensor with respect to a base material.

[0011]

In the groove copying method of the present invention, a first sensor composed of first and second eddy current displacement sensors sandwiching a groove center line Lc extending in a groove extending direction y. A pair of sensors and a second sensor pair of a third and a fourth eddy current displacement sensor, and a first sensor and a second sensor that form the groove.
Of the welding target material, the first and third eddy current displacement sensors are close to the groove center line Lc, and the second and fourth eddy current displacement sensors are far from the groove center line Lc. , The first and second sensors so that the difference signal between the detection signals of the first and second eddy current displacement sensors and the difference signal between the detection signals of the third and fourth eddy current displacement sensors match. Both pairs are simultaneously driven in the groove width direction z, and the welding center position of the welding torch is determined at the midpoint between the z-direction positions of the first eddy current displacement sensor and the third eddy current displacement sensor.

[0012]

In the eddy current displacement sensor, when a high-frequency current is passed through the exciting coil, an eddy current is generated by the high-frequency magnetic field in the metal body facing the exciting coil. This eddy current corresponds to the distance between the exciting coil and the metal body. Is short, it is strong, long is weak, and energy consumption corresponding to the eddy current value occurs in the metal body. The impedance of the excitation coil (corresponding to the distance between the coil and the metal body) is measured. There is also a mode and a mode in which a magnetic field (magnetic field due to an eddy current) near the end face of the exciting coil is measured by a hall element, a sensor coil or the like. In both cases, the detection signal is calibrated to represent the distance between the sensor and the metal body.

FIG. 4 shows a distance detection mode of the eddy current displacement sensor in the impedance measurement mode. When the entire end surface of the eddy current displacement sensor 23a faces the metal body 1, most of the magnetic flux generated by the high-frequency magnetic field generated by the eddy current displacement sensor 23a is orthogonal to the metal body 1, and the eddy current 1i is applied to the metal body 1. appear. A gap detection circuit 31a is connected to the eddy current displacement sensor 23a, which applies a high frequency constant voltage to the exciting coil of the eddy current displacement sensor 23a and calibrates the current value of the exciting coil to a gap (distance). Output the measurement signal.

As shown in FIG. 5A, when the entire end surface of the eddy current displacement sensor 23a faces the metal body 1, the current 23s flowing through the exciting coil of the eddy current displacement sensor 23a is as shown in FIG. It is small as shown in FIG. As shown in (a) of FIG. 6, when about 1/3 of the end surface of the eddy current displacement sensor 23a is detached from the metal body 1, the current 23s flowing through the exciting coil of the eddy current displacement sensor 23a becomes (b) of FIG. ) It becomes a little bigger as shown in.

As shown in FIG. 7A, when about 1/2 of the end surface of the eddy current displacement sensor 23a is disengaged from the metal body 1, the current 23s flowing through the exciting coil of the eddy current displacement sensor 23a is as shown in FIG. As shown in (b) of FIG.

The phenomenon explained above is due to the relative displacement between the sensor and the metal body in the direction along the surface of the metal body 1 even though the distance between the eddy current displacement sensor 23a and the metal body 1 is constant. The distance detection signal fluctuates, which is not preferable as a displacement sensor, that is, a distance sensor, but the present invention focuses on such a phenomenon.

In the present invention, as shown in FIG. 3, a groove center line extending in the direction in which the groove 2 extends (the y direction perpendicular to the paper surface of FIG. 3) (perpendicular to the paper surface of FIG. 3 and orthogonal to the line Lv). Line L
c: a first sensor pair (23a + 23b) composed of a first eddy current displacement sensor 23a and a second eddy current displacement sensor 23b, and a third eddy current displacement sensor 24 sandwiching FIG. 1).
The second sensor pair (24a + 24b) including the a and the fourth eddy current displacement sensor 24b is opposed to the first and second welding target materials 1a and 1b forming the groove 2, respectively. As shown in FIG. 3, in a mode in which the sensor output voltage increases as the distance increases, the difference obtained by subtracting the output voltage level of the second sensor 23b from the output voltage level of the first sensor 23a is simplified. 1 represents the distance from the upper surface of the welding target material 1a to the groove hypotenuse just below the first sensor 23a. Similarly, the difference obtained by subtracting the output voltage level of the fourth sensor 24b from the output voltage level of the third sensor 24a is the difference from the upper surface of the second welding target material 1b to the third sensor 24a.
Shows the distance to the hypotenuse immediately below.

In the present invention, the difference signal between the detection signals of the first and second eddy current displacement sensors 23a and 23b, and the third and fourth eddy current displacement sensors 23a and 23b.
Both the first and second sensor pairs are simultaneously driven in the groove width direction z so that the difference signal of the detection signals of the eddy current displacement sensors 24a and 24b of (1) matches. That is, the distance from the upper surface of the first welding target material 1a to the groove hypotenuse immediately below the first sensor 23a and the distance from the upper surface of the second welding object material 1b to the groove hypotenuse immediately below the third sensor 24a. First to fourth sensors 23a, 23b, 24a, 24
drive b. Thereby, the first to fourth sensors 23a, 2
3b, 24a, 24b, the groove center line Lc is the first and the third.
It is set at a position which is an intermediate point between the sensors 23a and 24a.

In the present invention, the first eddy current type displacement sensor 2
Since the welding center position of the welding torch is set at an intermediate position between the positions of 3a and the third eddy current displacement sensor 24a in the z direction, the welding center position of the welding torch is set to the groove center line Lc.

In FIG. 3, the first sensor pair (23a + 23b) and the second sensor pair (2
4a + 24b) are both driven in the direction y perpendicular to the plane of FIG.
Also, as described above, the first and second eddy current displacement sensors 2
Both the first and second sensor pairs are provided so that the difference signal between the detection signals of 3a and 23b and the difference signal between the detection signals of the third and fourth eddy current displacement sensors 24a and 24b match. When driven in the width direction z at the same time, the midpoint between the first and third eddy current displacement sensors 23a and 24a is at the groove center (L
v) and the groove width is constant in the longitudinal direction of the groove (direction y perpendicular to the paper surface), the first sensor pair (23
a + 23b) and the sum of the levels of the sensor output signals (intra-pair difference signals) of the second sensor pair (24a + 24b) is constant, but if the groove width changes, the level sum changes,
If the groove width is wide, the level sum is large, and if it is narrow, the level sum is small. Therefore, the groove width can be known from the level sum.

In a preferred embodiment of the present invention, the swing width of the torch (the swing width in the z direction) is increased when the level sum is large (the groove width is wide), corresponding to the level sum. Driving speed of the torch in the groove longitudinal direction y (welding speed V
y) down. When the level sum becomes small (the groove width becomes narrow), the swing width of the torch is made small and the driving speed (welding speed Vy) of the torch in the groove longitudinal direction y is increased.

Since the eddy current displacement sensor has a high accuracy of detecting a minute gap variation, the groove position detection accuracy is high and therefore the groove tracking accuracy is high even when the welding target material (base material) is thin. Further, since the eddy current displacement sensor is small and robust and its signal processing is relatively easy, the equipment for detecting the groove position is relatively small, robust and low in cost. Within each sensor pair, the distance from the groove detected by one sensor is corrected by the distance between the base material detected by the other sensor and the sensor, so the groove profile is changed by the change in the distance between the sensor and the base material. There is virtually no error. Further, even if the plate thicknesses of the two base materials facing each other with the groove set are different, accurate copying is realized. That is, stable and highly accurate copying is realized without being affected by the unevenness of the surface of the base material or the difference between the two base material plate thicknesses. The copying roller may be omitted.

Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

[0024]

1 shows a mechanical portion of a TIG arc welding apparatus for carrying out the groove copying method of the present invention in one mode, and FIG. 2 shows an electric circuit configuration of a copying control system of the welding apparatus. Figure 1
A plan view (arc welding) of the upper base metal (plate) 1a and the lower base metal (plate) 1b forming the groove 2 and seeing the base metal 1a, 1b through the back side from the back side (arc welding). (Bottom view of mechanism)
Equivalent to. The base materials 1a and 1b are vertical, and the groove 2 between them extends in the horizontal direction y. Referring to FIG.
The chi 4 is mounted on a torch carriage 5 that moves in the groove width direction (vertical direction = height direction) z. The torch carriage 5 is connected to the torch swinging mechanism 6 to swing the swinging mechanism.
It is reciprocally driven in the z direction by the power of the motor Mw. The torch swinging mechanism 6 is connected to the centering carriage 8 via a manual adjusting mechanism 7 for adjusting the x, y, z positions of the torch 4, which is not shown in detail. .

A nut 9 is fixedly attached to the centering carriage 8, and the nut 9 is screwed to a screw rod 11 which is rotatably supported by a traveling table 10. A guide bar 12 is fixed to the traveling base 10 in parallel with the screw rod 11. The guide bar 12 guides the centering carriage 8 movably in parallel with the screw rod 11.
The screw rod 11 is rotationally driven by a centering motor Mf via a pulley and a belt. When the centering motor Mf is normally rotated, the screw rod 11 is normally rotated and the nut 9 is driven upward,
The centering carriage 8 moves upward in the z direction. That is, the torch 4 moves upward. The slider arm of the linear potentiometer 13 is mechanically coupled to the nut 9, so that the linear potentiometer 13 can be connected to the torch 4.
Generates an electrical signal representing the z-direction position of the.

Another screw rod 15 is rotatably supported on the traveling base 10, and the nut 1 is attached to the screw rod 15.
6 is screwed. The sensor carriage 17 is fixed to the nut 16.

The carriage 17 is equipped with first, second, third and fourth eddy current displacement sensors 23a, 23b, 24a and 24b. Thereafter, the combination of the first and second eddy current displacement sensors 23a and 23b is referred to as the first sensor pair (23a + 23b), and the combination of the third and fourth eddy current displacement sensors 24a and 24b is referred to as the second sensor pair (24a +).
24b).

The screw rod 15 is rotationally driven by a groove-following drive motor Ms via a pulley and a belt. When the groove-following drive motor Ms is normally rotated, the screw rod 15 is normally rotated, the nut 16 is driven upward, and the sensor carriage 17 is moved upward in the z direction. The slider arm of the linear potentiometer 14 is mechanically coupled to the nut 16, so that the linear potentiometer 14 is connected to the eddy current displacement sensor 23.
An electrical signal is generated that represents the z-direction position of a, 23b, 24a and 24b.

The sensor carriage 17 rotatably supports a threaded rod 19 having a right-hand thread on the upper side of the middle point and a left-hand thread on the lower side, and the eddy current displacement sensor 23 is attached to the right-hand thread.
The nut fixed to a is screwed to the left screw to the nut fixed to the eddy current displacement sensor 24a.
Guide bars-21 and 22 are fixed to the sensor carriage 17 in parallel with the screw rods 19. The guide bar-21 is an eddy current displacement sensor 23a, and the guide bar-22 is an eddy current displacement sensor 24a. It is movably guided in parallel with the rod 19. The second sensor 23b is the first sensor 23.
a is integrally fixed to a, and the fourth sensor 24b is the third sensor 2
It is integrally fixed to 4a. That is, the first sensor pair (23a + 23b) and the second sensor pair (24a + 24)
b) is symmetric with respect to the threaded rod 19 and is arranged symmetrically with respect to a line parallel to the y axis passing through the center of the groove 2, that is, a groove center line Lc. The eddy current displacement sensor 23b is located above the eddy current displacement sensor 23a in the z direction, and the eddy current displacement sensor 24b is located below the eddy current displacement sensor 24a in the z direction. A knob 2 is attached to one end of the screw rod 19.
0 is fixed, and when the knob 20 is normally rotated by fingers, the first sensor pair (23a + 23b) and the second sensor pair (2
The distance in the z direction between 4a + 24b) becomes longer. That is, the distance between the sensors 23a and 24a is increased. When the knob 20 is driven in the reverse rotation, the distance between the first sensor pair (23a + 23b) and the second sensor pair (24a + 24b) becomes narrow.

The traveling table 10 has four rollers 25a to 25a.
d is rotatably supported by these rollers 25a.
25d are fitted in guide grooves carved in the upper and lower end surfaces (thickness surfaces) of the traveling rail 26 installed parallel to the base material 1b and the groove 2, and are movable in the horizontal direction y. .
Wires 27 are stretched around the rollers 25a to 25d and the drive roller 28, and the drive roller 28 rotates in the forward and reverse directions, so that the traveling platform 10 moves along the traveling rail 26 in the y direction. Go back and forth. The drive roller 28 is a running motor Mc.
It is driven to rotate by the power of.

Referring to FIG. The first, second, third and fourth eddy current displacement sensors 23a, 23b, 24a and 24b respectively include gap detection circuits 31a, 31b,
The gap detection circuit 31a is connected to 31c and 31d, and applies a high-frequency constant voltage to the exciting coil of the eddy current displacement sensor 23a to detect the current value flowing in the exciting coil, and to detect this as a signal (voltage) indicating the distance. And linearize and output. The sensors 23a, 23b and 24a
And 24b and the circuits 31a and 31b, 31c and 31d have the same specifications, and the outputs are calibrated to be the same under the same measurement conditions.

The output signals of the gap detection circuits 31a and 31c are applied to the differential amplifier AdA1. The differential amplifier AdA1 supplies the differential signal representing the level obtained by subtracting the level of the output signal of the gap detection circuit 31c from the level of the output signal of the gap detection circuit 31a to the differential amplifier 32a and the adder 32b. The differential amplifier AdA2 gives a difference signal representing a level obtained by subtracting the level of the output signal of the gap detection circuit 31b from the level of the output signal of the gap detection circuit 31d to the differential amplifier 32a and the adder 32b.

The differential amplifier 32a is a differential amplifier AdA1.
The difference signal representing the level obtained by subtracting the level of the output signal of the differential amplifier AdA2 from the level of the output signal of the differential amplifier is given to the motor driver 33. The motor driver 33 generates a PID control output for setting the difference signal to the zero level, and drives and drives the groove-following drive motor Ms.

Here, for example, the eddy current displacement sensor 23
a, 23b, 24a and 24b and x of the base materials 1a and 1b
Along with the directional distance of 5 mm, the eddy current displacement sensor 2
Assuming that the center positions of 3a and 24a are on the groove center Lv in FIG. 3 (in FIG. 3, the position of each sensor pair in the z direction at this time is shown as a reference point 0 mm), the first and third vortices are formed. The gap detection circuits 31a and 31b connected to the current displacement sensors 23a and 24a output a voltage of 1.5V. Second
The gap detection circuits 31c and 31d connected to the fourth eddy current displacement sensors 23b and 24b output a voltage of 0.5V.

The differential amplifier AdA1 outputs 1.0V obtained by subtracting the output 0.5V of the gap detection circuit 31c from the output 1.5V of the gap detection circuit 31a, and similarly,
The differential amplifier AdA2 outputs 1.0V. Therefore, the output of the differential amplifier 32a is 0V, which means that the sensor 23a,
23b is aligned with the groove center Lv (sensors 23a,
The intermediate point of 23b is on Lv), and the motor driver 33 does not drive the motor Ms. At this time, the output of the adder 32b is 2.0V (representing the groove width).

However, the eddy current displacement sensors 23a, 23
b, 24a and 24b and the base materials 1a and 1b have a distance of 5 mm in the x direction, and the center positions of the eddy current displacement sensors 23a and 24a are lower in the z direction than the groove center Lv in FIG.
5 mm) to the right at the gap detection circuit 3 connected to the first and third eddy current displacement sensors 23a, 24a.
1a and 31b output voltages of 2.0V and 1.0V. Second and fourth eddy current displacement sensors 23b, 24b
The gap detection circuits 31c and 31d connected to
Output the voltage of V.

The differential amplifier AdA1 outputs 1.5V obtained by subtracting the output 0.5V of the gap detection circuit 31c from the output 2.0V of the gap detection circuit 31a, and the differential amplifier AdA2 outputs 1.0V. 5 = 0.5V is output. Therefore, the output of the differential amplifier 32a is +0.5 V, which means that the sensors 23a and 23b are deviated from the groove center Lv to the right in FIG. 3, and the motor driver 33 is driven by the motor driver 33.
Drive the motor Ms in the normal direction to move the carriage 17 (sensor 23a
Etc.) to the left in FIG. At this time, the adder 32b
Has an output of 2.0 V (representing groove width). When the output of the differential amplifier 32a becomes 0V, the driving of the motor Ms stops.

When the center positions of the eddy current displacement sensors 23a and 24a are displaced upward (to the left in FIG. 3) in the z direction from the groove center Lv in FIG. 3, the output of the differential amplifier 32a becomes negative. , This is because the sensors 23a and 23b are at the groove center L
This means that the motor driver 33 reversely drives the motor Ms in the reverse direction from the v in FIG. 3 to drive the carriage 17 (sensor 23a or the like) to the right in FIG. When the output of the differential amplifier 32a becomes 0V, the driving of the motor Ms stops.

By such a scanning control, the center position (the midpoint between 23a and 24a) of the first sensor pair (23a + 23b) and the second sensor pair (24a + 24b) is aligned with the center of the groove 2 in time series averaging. .

The adder 32b supplies the swing controller 35 with a sum signal (groove width) representing the level obtained by adding the level of the output signal of the differential amplifier AdA1 to the level of the output signal of the differential amplifier AdA2. The swing controller 35 is a rotary encoder Re connected to the traveling motor Mc.
However, the sum signal is input to the shift register in synchronization with the travel synchronization pulse generated by one pulse each time the traveling platform 10 moves by the predetermined short distance d in the y direction, and the swing width corresponding to the output of the shift register is set. When the swing position of the torch 4 matches the lower limit value of the swing width, the swing motor 36 is rotated in the reverse direction (the torch 4 moves z
Direction (moving downward in the direction) to normal rotation (the torch 4 moves upward in the z direction), and when the swing position of the torch 4 matches the upper limit value of the swing width, the swing motor 36 is moved. Forward rotation (torch 4
Switches upward in the z direction) to reverse rotation (torch 4 moves downward in the z direction). The shift stage number n of the shift register is n = Dy /, where Dy is the distance in the y direction from the midpoint of the eddy current displacement sensors 23a and 24a in the y direction (the position of the screw rod 19) to the welding wire 3 of the torch 4. Since it is set to d, it represents the level obtained by adding the level of the output signal of the differential amplifier AdA2 to the level of the output signal of the differential amplifier AdA1 input to the shift register at a certain time (for example, the position shown in FIG. 1). The sum signal is then output from the shift register when the traveling platform 10 advances by Dy, and based on this output, when it is large (wide groove width), the swing width of the torch 4 is set wide and updated. If the width is small (the groove width is narrow), the swing width is narrowed and updated. Thus, the shift register is welded to the eddy current displacement sensors 23a, 23b, 24a and 24b in the traveling direction y.
A delay corresponding to the position difference Dy from the switch 4 is given. As described above, the swing width of the welding torch 4 is the groove width (sum signal).
It is automatically adjusted to a value proportional to.

The sum signal output from the adder 32b is also given to the running controller 37. Running controller 3
7 has a shift register similar to the shift register of the oscillating controller 35 described above, and the input sum signal is read after traveling (delay) of Dy in the y direction, and it is large (wide groove width). ), The speed of the welding traveling motor Mc that drives the traveling platform 10 (torch 4) in the y direction is decreased, and when it is small (the groove width is narrow), the speed of the traveling motor Mc is increased. As a result, the moving speed of the welding torch 4 in the y direction (welding speed Vy) is automatically adjusted to a value inversely proportional to the groove width (sum signal). As already explained, the differential amplifier 3
Of the copying motor Ms using the difference signal output by 2a.
By the PID scanning control by the driver 33, the center position (the midpoint between 23a and 24a) of the first sensor pair (23a + 23b) and the second sensor pair (24a + 24b) is aligned with the center of the groove 2 in time series averaging. The linear potentiometer 14 generates a sensor position signal that represents the momentary z-direction position of the midpoint between the eddy current displacement sensors 23a and 24a. Further, the linear potentiometer 13 generates a torch position signal representing the z direction position of the torch swing mechanism 6 (centering carriage 8), that is, the z center position of the swing center of the torch 4. To do. These sensor position signal and torch position signal are supplied to the follow-up drive circuit 34. The follow-up drive circuit 34 internally generates a signal (error signal) representing the difference between the two signals by a differential amplifier, and the error signal is the same as the shift register of the oscillating controller 35 described above. After being delayed by the amount of Dy running in the y direction by the shift register, the PID control output is calculated as the input of the PID control and output to the centering motor Mf. With this PID control, the position represented by the sensor position signal of the linear potentiometer 14 is used as a target value, and the torch position signal of the linear potentiometer 13 is used as a feedback value. In addition, the linear potentiometer is used. Type 14
The sensor position signal of is subjected to a delay corresponding to traveling in the y direction Dy and then used as a target value for positioning control,
The swing center position of the torch 4 (position in the z direction) is D in the y direction.
Eddy current displacement sensors 23a, 24a before traveling for y minutes
Is positioned at the center position in the z direction. That is, the first sensor pair (23a + 23b) and the second sensor pair (24a + 24)
At the groove center (Lc: Fig. 1) detected by b),
The swing center of the chi 4 is positioned.

In the above-mentioned embodiment, the centering carriage 8 and the sensor carriage 17 are separate bodies, and they are driven along the z direction. This is because the weight of each carriage including the mounted object is reduced to reduce the motion inertial force to ensure high scanning accuracy. Further, in the above-described embodiment, the swing controller 35,
In the traveling controller 37 and the follow-up drive circuit 34, the input signal is delayed by the amount of traveling in the y direction Dy.
This is the direction of the groove (sensor position) and the
This is because there is a Dy misalignment with the toe position, and to prevent torch copying due to changes in the groove position, width, etc. during that time. In this way, since the centering carriage 8 and the sensor carriage 17 are separated and driven respectively, the traveling table 10 is also separated into two parts, one for mounting the centering carriage 8 and one for mounting the sensor carriage 17, and driven in the y direction. The mechanism (37, 38, Mc, Re) may be two sets. These examples and modifications show high accuracy when the centering carriage 8 and the sensor carriage 17 including the mounted object, particularly the centering carriage 8 on which the torch is mounted, have a relatively high weight. It is suitable for performing the copy control of.

On the contrary, the centering carriage 8 and the sensor carriage 17 may be integrated (one). In this case, the z-direction drive mechanism (9, 11, Mf / 15, 16, M
s) is a set, and potentiometers 13, 14
The follow-up drive circuit 34 is omitted. In this case, since the sensor and the torch (the swing center thereof) move in the z direction at the same time, in the y direction, a gap of Dy occurs between the groove detection position (sensor position) and the torch position. For example, Dy is 50m
It can be set to m or more and 300 mm or less, and the variation in the groove position or the like due to the positional deviation Dy is small, and thus can be put to practical use. This modification is suitable when the centering carriage 8 and the sensor carriage 17 including the mounted object, especially the centering carriage 8 for mounting the torch, are small in weight and have a relatively low weight.

In the present invention, an eddy current type displacement sensor is used. Since this sensor has a high detection accuracy for minute gap fluctuations, even if the material to be welded (base material) is thin, the groove position detection accuracy is high and therefore the groove profile is imitated. High accuracy. Further, since the eddy current displacement sensor is small and robust and its signal processing is relatively easy, the equipment for detecting the groove position is relatively small, robust and low in cost.

Moreover, the four sensors form two pairs of two, each of which is symmetrical with respect to the groove. Since each sensor pair corrects the distance to the groove detected by one sensor (23a, 24a) by the distance between the base material and the sensor detected by the other sensor (23b, 24b), The center position of the groove can be detected irrespective of the fluctuation and the plate thickness difference between the two base materials facing each other with the groove placed, and the copying roller can be omitted. That is, it is possible to perform the groove copying with stable and high accuracy without being affected by the unevenness of the surface of the base material or the thickness of the base material plate.

[Brief description of drawings]

FIG. 1 is a bottom view of a copying mechanism embodying the present invention in one aspect.

FIG. 2 is a block diagram showing an electric circuit system coupled to the copying mechanism shown in FIG.

3 is an eddy current displacement sensor 23a, 23 shown in FIG.
b, 24a, 24b and an enlarged cross-sectional view showing the positional relationship between the base materials 1a, 1b, and sensors 23a, 23b, 24.
gap detection circuits 31a to 31 connected to a and 24b
The output signal level of d is also shown.

4A is a cross-sectional view showing a relative positional relationship between a metal body and an eddy current displacement sensor, and FIG. 4B is a plan view showing a surface of the metal body.

5A is a cross-sectional view showing a relative positional relationship between a metal body and an eddy current displacement sensor, and FIG. 5B is a graph showing a level of a high frequency current flowing in an exciting coil of the current displacement sensor.

6A is a cross-sectional view showing a relative positional relationship between a metal body and an eddy current displacement sensor, and FIG. 6B is a graph showing a level of a high frequency current flowing in an exciting coil of the current displacement sensor.

7A is a cross-sectional view showing a relative positional relationship between a metal body and an eddy current displacement sensor, and FIG. 7B is a graph showing a level of a high frequency current flowing in an exciting coil of the current displacement sensor.

FIG. 8A is a TI for a base material forming a groove.
A transverse cross-sectional view showing a swinging mode of the G arc welding torch, (b)
[Fig. 4] is a graph showing changes in welding current in the swing mode.

[Explanation of symbols]

1: Metal body 1a, 1b: Base material (material to be welded) 2: Groove 3: Welding wire 4: Welding torch 5: Torch carriage 6: Torch swinging mechanism 7: Manual adjustment mechanism 8: Center Alignment carriage 9: Nut 10: Traveling platform 11: Screw rod 12: Guide bar 13, 14: Linear potentiometer 15: Screw rod 16: Nut 17: Sensor carriage 19: Screw rod 20: Knob 21, 22: Guide bar 23a, 23b, 24a, 24
b: Eddy current type displacement sensor 25a to 25d: Roller 26: Traveling rail 27: Wire 28: Drive roller Ms: Groove copying drive motor Mf: Centering motor Mc: Traveling motor -Mw: Swing motors 31a to 31d: Gap detection circuit 32a, AdA1, AdA2:
Differential amplifier 32b: Adder 33: Motor driver 34: Follow-up drive circuit 35: Swing controller 36: Motor driver 37: Traveling controller 38: Motor driver Re: Rotor encoder

Claims (2)

[Claims] 1. A groove center line L extending in a groove extending direction y.
A first sensor pair composed of a first and a second eddy current displacement sensor and a second sensor pair composed of a third and a fourth eddy current displacement sensor sandwiching c, forming a groove. The first and third eddy current displacement sensors are close to the groove center line Lc, and the second and fourth eddy current displacement sensors are groove center line Lc. It is assumed that the first and second eddy current displacement sensors and the difference signal between the detection signals of the third and fourth eddy current displacement sensors are aligned so that the first and second eddy current displacement sensors match each other. And the second
Both sensor pairs are simultaneously driven in the groove width direction z, and the welding center position of the welding torch is determined at the midpoint between the z-direction positions of the first eddy current displacement sensor and the third eddy current displacement sensor. How to copy the groove. 2. A first eddy current displacement sensor located near a groove center line Lc extending in the y direction between the first and second welding target materials and facing the first welding target material, and at a distance. A first sensor pair including a second eddy current displacement sensor that is positioned and faces the first welding target material; a second sensor pair that is located near the center line Lc
A second sensor pair consisting of a third eddy current displacement sensor facing the welding target material and a fourth eddy current displacement sensor located far away and facing the second welding target material; a first sensor pair and a second sensor A sensor carriage for supporting the pair; a carriage driving means for driving the sensor carriage in the groove width direction z;
The carriage drive means is moved forward and backward so that the difference signal between the detection signals of the first and second eddy current displacement sensors and the difference signal between the detection signals of the third and fourth eddy current displacement sensors match. Urging means for urging; and torch supporting means for supporting the welding torch;
A groove copying device in which a support unit is interlocked with the sensor carriage.