JPS61154773A - Weld line detector - Google Patents

Abstract

PURPOSE:To improve the accuracy of detecting a weld line by disposing a magnetic sensor head provided with >=3 pieces of magnetic sensors to the periphery of a welding torch and setting the target position to be attained in accordance with the measured magnetic flux density value. CONSTITUTION:The magnetic sensor head 8 is attached to a ring 10 which is rotated in a supporting device 8 and >=3 pieces of the magnetic sensors 13 are disposed to the top end thereof. The sensors 13 are disposed with the magnetic flux measuring surfaces perpendicularly to the surface of objects 1 to be welded and perpendicularly to the tangential direction of the ring 10 at 1mm above said surface. The welding torch 3 is inclined by a prescribed angle phiby a pulse motor 7 coupled directly to a revolving shaft 6 of the torch. The aiming angle at the top end of the torch 3 is exactly detected by comparing the magnetic flux density value inclined by the angle phi with the density value at the reference point, storing the same and making calculation to predict said position even if the measuring magnetic flux density is asymmetrical. The accuracy of detecting the weld line is thus improved.

Description

[Detailed Description of the Invention] (Technical Field of the Invention) The present invention relates to a welding line detection device, and particularly to a phenomenon in which magnetic flux generated by welding current leaks from a welding line of a joint when arc welding magnetic materials such as steel. The present invention focuses on a welding line detection device that can measure this leakage magnetic flux and trace it with a welding torch online.

[Technical background of the invention and its problems]

Since leakage magnetic flux generated by welding current during arc welding crosses and passes through the weld line, the weld line can be detected by measuring this leakage magnetic flux near the weld line. Based on this principle, conventional welding line detection devices install one magnetic sensor such as a Hall element with a surface receiving magnetic flux perpendicular to the welding line and parallel to the welding line at a certain distance left and right from the center. The welding line was detected by rotating this head to find a position where the outputs of the left and right magnetic sensors were equal, and by driving the magnetic sensor head in that direction. This is based on the premise that when the groove shape is symmetrical with respect to the opening center, the leakage flux density is maximum at the groove center, and the leakage flux distribution is also symmetrical with respect to the groove center. This is because if you find a position where the output of the magnetic sensor is equal on both sides of the line, the center of the magnetic sensor head will coincide with the weld line.

Therefore, if the joint is not symmetrical with respect to the root position of the welded joint, such as an overlap joint, the leakage magnetic flux distribution will also be asymmetrical, so the magnetic flux density should be adjusted so that the center of the magnetic sensor head is on the weld line. need to be corrected. In this case, measure the magnetic flux density in advance to calculate the magnetic flux density to be corrected, and if the detection device is an analog type, store the correction value of the analog amount equivalent to the magnetic flux density, or if the detection device is an analog type, store it in the memory of the microcomputer system. It was necessary to memorize correction values.

In this way, conventional welding line detection devices mainly target cases where the magnetic flux distribution is symmetrical, so handling is troublesome in the case of an asymmetrical magnetic flux distribution. , and the setting of correction means, making it difficult to easily obtain high accuracy.

On the other hand, there are many butt joints where the groove shape is not symmetrical, such as Moshi-shape, K-shape, J-shape, double-sided J-shape, and materials with different magnetic properties are used due to the environment in which the welded product is used. Since welding may occur, there has been a strong demand for a weld line detection device that can be easily used even when the magnetic flux density distribution is asymmetric.

[Purpose of the invention]

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, and to solve the problem that the magnetic flux density distribution is geometrically asymmetric due to the type of welded joints such as lap joints and padded joints, and the groove shape of butt joints. To provide a weld line detection device that can easily and reliably detect the position of the weld line even when the leakage magnetic flux distribution becomes asymmetric due to welding of materials with different magnetic properties or when materials with different magnetic properties are welded. be.

(Summary of the Invention) In order to achieve the above object, the present invention includes a magnetic sensor head in which three or more magnetic sensors for detecting magnetic flux density values around a welding torch are arranged equidistantly from the center to the left and right. ,
Means for calculating and storing the relationship between the magnetic flux density value at a representative point serving as a reference and the magnetic flux density value at other positions based on the measured value of the magnetic sensor, and comparing the measured value of the magnetic sensor with the output value of the calculation storage means. The present invention provides a welding line detection device comprising a prediction means for calculating and predicting a position where the difference becomes small, and a means for setting a target position to be reached based on the output of the prediction means and moving a welding torch. be.

[Embodiments of the invention]

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIGS. 1(a) and 1(b) are a front view and a side view showing the arrangement of main parts of a weld line detection device according to an embodiment of the present invention. As shown in the figure, a case is illustrated in which the grooves 2 of the objects to be welded 1 to be welded together are formed in an annular shape. Welding progresses along the groove 2 with a welding torch 3 placed on a cart (not shown) and a welding electrode in a designated direction, for example, since the welding torch 3 is tilted by an angle φ with respect to the vertical direction, welding is carried out in a direction tilted by an angle φ. Welding is carried out while forming a welding part 5 on the workpiece 1 by the welding electrode 4 fed by a predetermined distance of m, and progresses in the direction of arrow A. The welding torch 3 is tilted by an angle φ by a pulse motor 7 directly connected to the torch rotating shaft 6 on one side.

A magnetic sensor head 8 for detecting a welding line is attached to a ring 10 that rotates within a ring-shaped head supporter 9 on which a torch rotation shaft 6 and a pulse motor 7 are mounted. A DC motor 11 with a fast startup speed and an absolute encoder 12 directly connected to the DC motor 11 are disposed at one end of the supporter 9. The DC motor 11 rotates the welding torch 3 concentrically around the support position near the lower end. As the ring 10 rotates, the magnetic sensor head 8 and the magnetic sensor 13 attached to its tip rotate in the direction of the arrow.

The magnetic sensor 13 has its magnetic flux measuring surface placed about 1M above the surface of the workpiece 1 and perpendicular to the surface and perpendicular to the tangential direction of the concentric circle of the rotary ring 10, and from the center of the magnetic sensor head 8. A total of four magnets are arranged at equal distances, two on each side, and the magnetic flux densities at four points on the tangent to the concentric circle of the rotating ring 10 are measured across the weld line.

FIG. 2 is a block circuit diagram for processing signals related to measurement and control applied to the configuration of FIG. 1.

As shown in the figure, signals measured by the magnetic sensor 13 are collected in a data collection unit 14. The data acquisition unit 14 includes a multiplexer circuit, a sample-and-hold circuit, an analog-to-digital converter circuit, a 3-state buffer circuit, etc., and the digitized signal is passed through the 3-state output buffer of the data acquisition unit 14 to a one-chip microcomputer, etc. The data is transmitted to the microb0 setter circuit 15 (hereinafter referred to as the MPU circuit). A memory 16 is connected to the MPU circuit 15 via a bidirectional bus capable of both input and output so that data can be exchanged.

When a command value is issued from the MPU circuit 15 to the DC motor 11, the digital-to-analog converter 17 (hereinafter referred to as
The signal is converted into an analog signal via a DAC (referred to as a DAC) and provided to the DC motor drive unit 18. This DC motor drive unit 18 generates the power necessary to drive the DC motor 11 and supplies this to the DC motor 11.

Now, if the magnetic flux distribution on the welding line is asymmetrical as shown in the magnetic flux density distribution diagram of FIG. 3, the leakage magnetic flux does not necessarily reach its maximum value at the target position of the torch tip in the welding line gap. Therefore, prior to starting, the inclination angle φ of the welding torch determined from the groove shape and dimensions is input into the keyboard of the input/output crab knit 19 consisting of an LED display and a keyboard.

As a result, this information is transmitted to the microcomputer unit 20 (hereinafter referred to as microcomputer unit), which is connected to the input/output unit 19 and includes peripheral elements such as a CPtJ, memory, and an interface. When the microcomputer unit 20 calculates the number of pulses required to obtain the tilt angle φ, this information is stored in the memory within the microcomputer unit 20 and simultaneously transmitted to the motor control unit 21 where it is converted into pulses and is used to control the motor. The pulses are converted by the drive unit 22 into pulses having the power to drive the pulse motor 7, and are input to the pulse motor 7.

In this way, after tilting the welding torch 3 by φ at the origin position, and aligning the center of the magnetic sensor head 8 with the target position of the torch tip, press the keyboard of the input/output crab knit 19 to read from the past results. 1 each on the left and right
The magnetic flux density of each representative point is then inputted with instructions for sensor position indexing. Data on magnetic flux density is transmitted to the MPtJ circuit 15 through a buffer RAM (random access memory) 23 connected to the microcomputer unit 20. When a buffer RAM is used, there is no need to synchronize the operations of individual microprocessors by handshaking or the like, so high-speed data transfer is possible even in an asynchronous state. The magnetic flux density data that has arrived at the MPU circuit 15 is stored in the memory 16 and used as a reference value for welding line detection. On the other hand, when the absolute encoder 120 rotation angle θ is read by the microcomputer unit 20 according to the sensor position indexing instruction, the X, Y of the magnetic sensor head 8 is determined from the angles φ and θ.
The position (x, yl) on the plane is screened out.

If there is no past track record, store the measured value near the starting position in the memory 16 after starting and use it as the reference magnetic flux density for the time being. The measured value at that position is once again stored in the memory 16 and used as the final reference value. For this purpose, the magnetic flux density measured by the magnetic sensor 3 is transmitted to the data acquisition unit 14.
After converting it into a digital quantity, it is transmitted to the MPtJ circuit 15. As a result, this MPLJ circuit 15 causes the DC motor 1
The command value is output for 1, and the buffer RA
It is transmitted from the input/output crab unit 19 to the worker through the M23 and the microcomputer unit 20.

Now, at the starting point of welding, the center of the magnetic sensor head 8 is at the future target position ff (X, Vl) of the torch tip, so
When the operator inputs a departure instruction from the keyboard of the entry/exit crab unit 19, the microcomputer unit 20 causes the motor control unit 21 to move a cart (not shown) so that the target position of the tip of the torch 3 moves to the position (Xl, '/1).
At the same time, the command is transmitted to the MPU circuit 15 through the buffer RAM 23. the result,
The motor control unit 21 converts the digital quantity command value into an analog quantity, and then transfers this to the motor drive unit 22.
is converted into the power necessary to move each DC motor 24.25 of the X-axis and Y-axis by a predetermined amount.
Give to 5. Rotary encoders 26, 27 are directly connected to the shafts of these two DC motors 24, 25, respectively, and generate pulses proportional to the number of rotations. These pulses are input to the pulse count direction determination unit 28, which quadruples the number of pulses, counts the pulses, determines the direction from the phase relationship between the two pulse trains, and inputs the pulses to the microcomputer unit 20. The microcomputer unit 20 calculates X by integrating the number of pulses.
Calculate the position on the Y coordinate axis and at the same time calculate the sampling period τ
The moving speeds of the X-axis and Y-axis are calculated from the magnitude of the number of pulses for each pulse. The path from the rotary encoders 26 and 27 to the microcomputer unit 20 via the pulse count direction discrimination unit 28 forms a feedback path, so the target position, here the position! As soon as (x, yl) is about to deviate, control can be performed to suppress this movement. Furthermore, even if the movement speed of the torch 3 deviates from the speed specified before departure, it can be controlled to maintain this speed.

On the other hand, the MPtJ circuit 15, which has received the measurement start command from the microcomputer unit 20, outputs an operation command to the data collection unit 14. As a result, the data acquisition unit 14 acquires the signals of the four magnetic sensors 3 when the center of the magnetic sensor head 8 is at the position (xl, yl) one by one by switching channels using a multiplexer, sequentially samples them, and converts them into analog and digital signals. By holding it for a period until the conversion is completed, it is converted into a digital quantity and sent to the MPL1 circuit 15 through a 3-state output buffer.

The detected digital signals at these four points are shown in Fig. 3 (a) and (b).
), when the center of the magnetic sensor head 8 is at a distance lio, the magnetic flux density B1 . Magnetic flux densities B-1, 8-2 at positions separated from B2 by the same distance S-1, 5-2 in the negative direction (the absolute value is S, the hanger is equal to B2 and in the opposite direction)
corresponds to In the case of the L-shaped groove 2 as shown in Fig. 3, the magnetic flux distribution is not symmetrical near the surface of the workpiece 1, so B1
=FB-1°B-νB-. Therefore, position S1.
With S-1 as a representative, this magnetic flux density B, B- and the magnetic flux density ratio between the two points 82 B-2 □ and □ (or the magnetic flux density difference may be used) B,
Create data for B-1, compare these with reference values before starting welding, and repeat prediction of the position where the difference between them will be reduced and movement measurement to find a place where all the data match. If the location cannot be found, there is a certain tendency that B-1, 8-1 B-, 2[32 and the magnitude relationship of □>□ is maintained, and on top of that, 81 degrees, for example, within ±5%, is searched for while moving the torch 3 and rotating the rotary ring 10. As a result, even if there are places where the groove 2 is slightly different from the designed value due to deviations that occur during assembly, it is possible to prevent the target position of the torch tip from deviating along the welding line. Of course, if the magnetic flux distribution is symmetrical,
Thus, the target position of the tip of the welding torch 3 can be easily found.

Thereafter, as the welding torch 3 moves forward, the future target position of the torch tip (X·, Vi)i=1.2.3. is searched by the magnetic sensor 13 at a sampling period of several ms or less.
. . . are sequentially stored in the memory of the microcomputer 20, and on the other hand, this position information is sequentially retrieved from the memory and advances to the position (xj"1yj)j=1.2, 3... The welding torch 3 is traced so that the target position of the torch tip is the desired target.

In addition, if the DC motor 11 does not need to start up so quickly and the angle accuracy can be maintained sufficiently by resetting the rotation angle each time the magnetic sensor head 8 passes a reference point (not shown), If the DC motor 911 is replaced with a pulse motor, the rotation angle can be set without using the absolute encoder 12. In addition, in the explanation so far, we have explained the case of measuring magnetic flux density B as an example, but since magnetic sensors are made with the same area through which magnetic flux passes, the same effect can be obtained even if we think of measuring inside magnetic flux. Obtainable. Furthermore, although the above embodiment illustrated the welding torch 3 and the magnetic sensor head 8 mounted on a trolley, this device can be attached to the tip of a robot arm, etc., and the welding torch 3 can be moved in a tracing manner while performing a similar detection operation. Of course, the same effect can be obtained by using both methods.

FIGS. 4(a) and 4(b) are a partial side view and a magnetic flux density distribution diagram of a weld line detection device according to another embodiment of the present invention. As shown in the figure, three magnetic sensors 13 are arranged alternately on the magnetic sensor head 8 so as to straddle the weld line. In such a configuration, when searching for the target position of the tip of the welding torch 3, the magnetic flux densities at three points B, Bo, and B are compared with reference values B, 1.88°, and "S-1." The sensor 13 has a magnetic flux measurement surface placed perpendicular to the surface of the workpiece 1 and perpendicular to the tangential direction of the concentric circle of the rotating ring 10, and one sensor 13 is placed at the center of the magnetic sensor head 8, and the other two are placed from the center. One on each side is placed equidistantly apart.

Therefore, the number of magnetic sensors is reduced by one compared to the configuration shown in FIG. 1, and the measurement portion is made smaller accordingly. Furthermore, since the analog-to-digital conversion time is also reduced, the sampling period τ can be shortened. Also, regarding the measurement of magnetic flux density, B1 and B-1 in the previous example are B. , B2 and 8-2
If it is assumed that has changed to 81 and 8-1, the processing of magnetic flux density and the subsequent operation of - can be done in exactly the same way. Therefore, it is possible to realize an apparatus that is inexpensive and can further improve the quality of welding by shortening the sampling period τ.

FIG. 5 shows a partial side view of a weld line detection device according to still another embodiment of the present invention. In the configuration shown in the figure, a magnetic sensor array 29 is used in which a large number of magnetic sensor elements are arranged in close contact with each other in an array shape, and each magnetic sensor element has a magnetic flux measurement surface placed perpendicularly and perpendicularly to the tangential direction of the concentric circles of the rotating ring 10. This magnetic sensor array 29 can be picked up by a non-magnetic movable bar 30 attached to the end on the groove 2 side. Movable bar 30
is connected to a movable part of a small linear pulse motor 31 having a moving distance of 3 to 5 m, and is moved in the vertical direction shown by arrow C, and the vertical position is calculated by the number of pulses. This linear pulse motor 31 is attached to the back side of the rotating ring 10.

FIG. 6 is a block circuit diagram for processing signals related to measurement and control when a magnetic sensor array 29 consisting of 10 q magnetic sensor elements is used. As shown in the figure, the output end of the magnetic sensor array 29 is connected to the data acquisition unit 14, and the detected values are converted into digital values and converted into M
It is input to the PU circuit 15. The MPU circuit 15 calculates a command value and sends this command value to the linear pulse motor control unit 32. The command value is converted into the number of pulses necessary to drive the linear pulse motor in the linear pulse motor control unit 32, and then converted into pulses with the power necessary to drive the motor in the next linear pulse motor drive unit 33, and the command value is converted into the number of pulses necessary to drive the linear pulse motor. 31.

As a result, as in the embodiment shown in FIG. 1, since the magnetic sensor array 29 is initially located at a distance of about 1 to 2 M from the surface of the workpiece 1, the maximum magnetic flux density B input before starting, By checking the magnetic flux distribution before and after the position of the maximum magnetic flux density BIIl as a mark based on the correlation between the position of the welding torch 3 and the target position of the tip of the welding torch 3,
You can get an idea of the target position. In this case, since the magnetic flux densities at 10 points are measured simultaneously, it is possible to obtain a highly accurate magnetic flux distribution. Next, MPU circuit 1
5, the control unit 32 generates as many pulses as instructed, and the linear pulse motor 31 is driven downward by 11nIR# through the drive unit 33. As a result, the movable bar 30 moves to the magnetic sensor array 29.
Not only can the magnetic sensor array 29 brush against the surface of the workpiece 1, but also the magnetic sensor array 29 can be inserted into the groove 2. This is because the magnetic sensor array 29 can be made to have a length of around 10M or less in the direction of the arrow O, so in many cases the magnetic sensor array 29 can be made smaller than the groove 2.

Therefore, it is possible to perform measurements at locations with high magnetic flux density.
Since the magnetic flux distribution is coordinated, the target position of the tip of the welding torch 3 can be precisely known, and high-quality welding can be performed.

〔Effect of the invention〕

As described above, according to the present invention, when magnetic materials are welded, even if the magnetic flux distribution of leakage flux generated by the welding current around the weld line is asymmetrical due to the magnetic materials used, Welding lines can be detected accurately with simple keyboard input without any special preparation. First, the aiming position of the welding torch can be determined accurately, so high-quality welding can be performed. Moreover, since the equipment related to measurement can be configured with micro compressors and digital circuits, it is possible to achieve higher functionality and lower costs.Furthermore, the equipment including the magnetic sensor can be stored compactly, so it does not take up much space. There are also advantages.

[Brief explanation of the drawing]

1(a) and 1(b) are a front view and a side view, respectively, showing the arrangement of the main parts of a weld line detection device according to an embodiment of the present invention, and FIG. 2 is a measurement control signal of the device shown in FIG. 1. 3(a) and 3(b) are magnetic flux density distribution diagrams showing an example of the magnetic flux distribution around the groove in FIG. 1, and a sectional view of the main parts; FIG. FIG. 5 is a partial side view and magnetic flux density distribution diagram of a welding line detection device according to another embodiment of the present invention, FIG. FIG. 3 is a block circuit diagram regarding measurement control signals of the device shown in the figure. DESCRIPTION OF SYMBOLS 1... Workpiece to be welded, 2... Bevel, 3... Welding torch, 8... Magnetic sensor head, 10... Rotating ring,
DESCRIPTION OF SYMBOLS 11... DC motor, 12... Absolute encoder, 13... Magnetic sensor, 14... Data collection unit, 15... Microprocessor circuit, 29...
...Magnetic sensor array, 31...Linear pulse motor. Applicant's agent Kiyoshi Inomata Figure 5 Figure 6

Claims (1)

[Claims] 1. A magnetic sensor head in which three or more magnetic sensors for detecting magnetic flux density values around the welding torch are arranged equidistantly to the left and right from the center, and based on the measured values of the magnetic sensors. means for calculating and storing the relationship between the magnetic flux density value at a representative point serving as a reference and the magnetic flux density value at other positions, and comparing and calculating the measured value of the magnetic sensor with the output value of the calculation storage means to reduce the difference. A welding line detection device characterized by comprising a prediction means for predicting a position, and a means for setting a target position to be reached based on the output of the prediction means and moving a welding torch. 2. The weld line detection device according to claim 1, wherein the magnetic sensor head has magnetic sensors arranged in an array in a narrow range and attached to the end of a non-magnetic movable member.