JPS5838672A - Detector for weld line - Google Patents

Abstract

PURPOSE:To detect a weld line easily without degrading workability by detecting the rate of displacement from the weld line by the detection signal from a magnetic field sensor which detects the leaking magnetic field generated by welding current. CONSTITUTION:A magnetic field detector 32 is oscillated at a specified amplitude in a y-axis direction with respect to a shielding gas nozzle 30 of a torch by a freely rotatable coupler 33. When a torch 30 is advanced in the direction of the straight line connecting the center of the amplitude and the nozzle 30 and if the center of the amplitude advances on the same weld line together with a wire electrode 31, the detection signal for the leaking magnetic field from the detector 32 is the pulse signal of a specified interval. When the electrode 31, hence the detector 32 deviate from the weld line 7 on advancing of the torch 30, the interval of the pulse signal changes. If the width of the deviation exceeds the amplitude of the detector 32, the pulse signal is no more produced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device 1c for detecting a welding line, that is, a welding gap (space Wl between parts to be welded) used in an arc welding robot.

First, we will introduce two examples of sensors that are generally being considered for use in arc welding robots.

FIG. 1 shows the schematic structure of a commercially available magnetic field sensor for welding lines. This magnetic field sensor is composed of a detection head (2) and a controller (violet). The detection head (2) has a structure in which three coils are lined up inside, and a low frequency magnetic field of +151 f is generated from the transmitting coil (3) in the middle to the receiving coils (41) on both sides. , the detected object (6) is between the transmitting coil (31) and the receiving coil (4).

If the left and right sides are uniform, the low frequency magnetic field can be the same on the left and right sides.)
, is in a balanced state, but if the welding wire (7) shifts from directly below the transmitting coil (31 to the left or right), the eddy current loss and magnetic resistance will change, causing the above-mentioned balanced state to collapse. The principle of this magnetic field sensor is to analyze the left and right difference signals of the frequency magnetic field (5) with the controller 5 (1) and detect the IW contact 171 (71). "Due to the self-magnetic field of the welding arc, the tracking accuracy of the sensor will be significantly reduced, and the weld line (7) will be located between the two receiving coils (4) due to the bottom surface of the detection head (2). If there is a deviation of more than about 1/2 of the distance, there will be drawbacks such as the position of weld line +71 not being able to be detected.

Next, Figure 2 attempts to visually detect lysis. This is a typical example of a so-called visual sensor.

Normally, the visual sensor αI is connected to the light source 04. lens ae.

Surface, running mirror a9. It consists of a detector n, etc.

It is stored in one container. The light emitted from light source No. 0 is focused by the collimating lens AS, and the light spot is focused by the traveling mirror 4 onto the object to be welded +6+
(Swipe D weld line (7) crosswise.

The trajectory of the spotted light beam (11 is the optical lens (
Through 2), we are trying to protect the company in the detector section.

Signal processing from the detector is generally performed outside the detector. Such visual sensors are extremely versatile in the sense that they are close to human work functions. In fact, it has been found that when applied to the joint shape of base metals in arc welding, it is possible to accurately detect weld lines such as center alignment 9 overlapping, fillets, and grooves. however,
When putting this type of visual sensor #i, which also includes pattern recognition of joint shapes, into practical use, the sensor was too large and
It has disadvantages such as high cost. For example, even if a small component such as a light emitting diode is used as the light source aΦ, the size of the visual sensor is box-shaped with sides of about 10 mm, which is much larger than an actual welding arc torch. However, when a visual sensor with such dimensions is attached to an arc welding robot, there is a drawback that work efficiency is impaired.

This invention was made with the aim of eliminating the above drawbacks of conventional sensors, and uses a magnetic field detection sensor to detect the phenomenon in which the magnetic field distribution caused by arc current changes greatly depending on the position of the welding line. It is designed to detect the position of the weld line.

First, we will explain the phenomenon of magnetic field generation in the welding arc.

As shown in FIG. 3, taking as an example the butt welding of two objects to be welded (6), the welding arc is in the X direction K.

Consider the state in which the welding bead has progressed to one point while forming a weld bead. In this state, the magnetic field distribution in the X direction on the weld line σ) is measured with a gakumeter. As a method for measuring the magnetic field distribution, for example, when the welding arc advances to point a4, immediately extinguish the welding arc, contact the electrode (not shown) at point 9, energize it, and place the probe as of the Gauss meter on the welding line (7).
), it is possible to obtain the magnetic field distribution in almost the same state as when the actual welding arc advances from a point.

In Figure 1g4, the workpiece (6) to be welded has a plate thickness of am
s steel material is used, and the gap at the weld line (7) is approximately 11IIB.
In the following, the welding current is about 350 μm, and the workpiece to be welded (6
) shows an example of the results of measuring the magnetic field strength in the y direction along the x-axis at a distance of about 3 meters above the top surface of the device. In the figure, the origin of the X-axis coordinate is at the point @. From Figure 4, we can see that the magnetic field is stronger on the unwelded side, and that the magnetic field strength is about 300 Gauss in the direction of travel of the welding arc (unwelded side) from the point. Recognize.

The appearance of a magnetic field above the weld line ()) is
Among the objects to be welded (6), S7 welding 1! This is thought to be due to the difference in magnetic resistance of the air gap (?).

A second question may arise here. That is,
In Figure 3, the flow is in two axial directions (welding chamber IN, so
As a result of Fig. 4, I measured the magnetic flux on the ijg axis 1, so I guess it's not possible, but I understand that there is a leakage magnetic field above it, even though a magnetic circuit is formed with the Fi weld bead. This is a question that may not be possible. In response to this, the nine inventors attempted the following experiment. In Fig. 3, the object to be welded (61t - welding 11
Similar experiments and measurements of the magnetic field strength were conducted using a single piece of steel material B (71) with no voids.The distribution of this magnetic field strength in the X direction is as shown by the broken line in Figure 5. ,
The solid line is the difference from FIG. 4, ie.

The distribution of the net leakage field strength in the y direction in the x direction.

It is expressed as an average value of many experimental data.

By the way, the welding current is about 350A.

Figure 5 fruit! However, as expected, the weld bead (
If the leakage magnetic field strength on the 2) side is approximately 0, and there is a constant leakage magnetic field on the unwelded side, the strength on the unwelded side is approximately 90~11.
The fact that there is a leakage magnetic field in the y direction of 0 Gauss is noteworthy in the sense that it presents a very powerful weapon for the current detection method of weld a (c).

Now, in a series of magnetic field measurements as described above.

The inventors also measured the unidirectional distribution of magnetic field strength in two directions in FIG. Figure 6 shows the results of actually measuring the distribution of the magnetic field strength in two directions in the vicinity of the top surface of the workpiece to be welded (61) under the condition that the welding current is approximately 35OA.
Although there are variations in the strength of the magnetic field fK near one point in the figure, detection is possible in all cases! It has been pointed out here that the magnetic field strength is such that the magnetic field generated on the unwelded side attempts to detect the weld line Cγ) of the workpiece to be welded (6). This is a phenomenon that can be seen in a narrow area directly above the gap. This phenomenon of magnetic field generation occurs when two workpieces (6) are welded as shown in Figure 3.
Other than the case of matching.

It has been confirmed that even when overlapping, filleting, or beveling, the magnetic field strength [K, although there may be some difference Fi, occurs in the same way.

As an example, Fig. 1 shows the case of two-lap welding,
- Let us show the distribution in the X direction of the leakage magnetic field strength in the direction 45 & with respect to the surface of the workpiece.

Next, a specific example of detecting a leakage magnetic field of a welding wire,
An example of a control system when this is applied to an arc welding robot will be explained in detail.

FIG. 8 shows a welding line (7
) is a perspective view of an embodiment of a detection device for a conventional consumable electrode welding machine. ) is added with * and 6. The magnetic field detector (to) is installed at position 11u,)
- It can be any part of the torch, in short, the torch c11K
On the other hand, it is necessary to be able to rotate freely, and in some cases, the distance between the torch and the torch can be expanded and contracted. Also.

In the embodiment shown in FIG. 8, an arc is generated between the wire electrode aυ and the welding object (6) over the weld a (7) at the butt part of the welding object (6), and the welding bead is At the same time, the nozzle (to) advances in the X direction while detecting the leakage magnetic field on weld a (to) with the magnetic field detector υ. Note that zero or fc is when the magnetic field detector (to) is displaced from above the welding line (71).

Two embodiments of effective leakage magnetic field detection sensors will now be described.

One example is as a leakage magnetic field detector.

It comes with a standard Gaussmeter probe that uses the Hall effect. As we all know.

A Gaussmeter detects the magnetic field that enters the plane of the Hall element at right angles. Therefore, when detecting leakage magnetic fields in two directions, the tip of the detector (support) was bent at right angles.

A second embodiment of the leakage magnetic field detection sensor is shown in FIG.

The figure shows a magnetic field sensor called a so-called magnet gate meter. It is constructed into two cylindrical probes for detecting the leakage magnetic flux of the tangent line (7). As shown in the enlarged view of Fig. 9(b), the magnetic field detection part of the probe +411 has a core (for example, cylindrical permalloy) (2).
It has a structure in which two coils, the primary coil 4 and the secondary coil, are placed almost coaxially with the core. The principle of operation is 9. For example, the primary coil 12
An alternating current of K frequency f is applied, and the winding of the primary coil is determined so that when there is no external magnetic field, the output of the secondary coil induced by changes in the magnetic flux of the core becomes zero. , if the external magnetic field - enters the core (goods), it will be approximately 2
The external magnetic field is detected by utilizing the fact that an output of R11l of f is generated in the secondary coil. In addition, this magnetic gate meter.

In addition to being able to detect minute magnetic fields such as the earth's magnetic field, it can be constructed compactly and robustly, so it has been found through practical implementation that the present invention is very effective in detecting leakage magnetic fields.

Next, the output signal from the above-mentioned magnetic field sensor is used for benevolent control of the torch of the arc welding robot, and an embodiment related to a processing method of this output signal will be described in section b.

In Figure 8, magnetic field detector a\? When swept across the welding line (7) in seven directions, the strength of the leakage magnetic field detected by the magnetic field detector (to) is as shown in Figure 10. That is, Figure 810 shows the leakage magnetic field distribution in the y direction near the weld line +71.

What is the strength of this leakage magnetic field?

Needless to say, it varies depending on the distance between the detection end of the magnetic field detection a (to) and the workpiece to be welded (6), the value of the welding current, etc.

Now, in one embodiment shown in FIG. 8, the magnetic field detector 0 is swung at a constant amplitude in the y-axis direction via a coupler C (1) which can rotate once with respect to the shield gas nozzle circle of the torch. At this time, the center of the swing width and the shield gas nozzle (towards),
(Yo) Strictly speaking, the wire electrode a that is emitting an arc
When the torch is advanced in the direction of the straight line connecting D), the center of the amplitude and the wire electrode tsn are both on the same welding line (2
), the leakage magnetic field detection signal from the magnetic field detector (to) is detected at regular intervals 1, 1, as shown in Fig. 11 (a) K.
) becomes a pulse signal.

However, as the welding torch advances, the wire electrode (2
), so when the magnetic field detector (to) deviates from the *tangent line (7), the interval of this pulse signal is.

) and (C) in Figure 11. Figure 11 (
C) is welding! ! In a state where the width of the deviation from (7) exactly matches the amplitude, the interval between the pulse signals becomes 92to, twice that in FIG. 11(a). If the width of the deviation becomes larger than the amplitude of the magnetic field detector (to), this pulse signal will no longer be output◎ The thing to note here is #! 45! Considering that there is a variation in the leakage field strength shown in Figure 1, the signal is processed using two values: one above a certain magnetic field strength and one below. That's true.

In one embodiment according to the present invention, tQ, which is the reference in FIG. 11(a), is set, and the same v! Create a circuit to detect to+'H of J(b), and when this exceeds t(1), swing the torch (to) to either the left or right, and tQ-1-t
A control method was adopted in which the increase or decrease in l was determined and the left and right swing of the torch was reversed or the torch was moved further. In this example, the one-line device of the torch, the left and right oscillation speed, the amplitude and frequency of the magnetic field detector (to), and the magnitude of tO-4-tl are determined. Depending on the conditions such as the direction of the torch I)Fi
Although there are cases in which the welding line progresses over the welding line while making slight vibrations in the y direction, it has been found that there is actually a range of conditions in which there is no effect on the 0 weld Kll and Z. That is.

It seems that there is enough copying precision KFi in practical aspects.

Furthermore, even if the welding line is a curved line, it is possible to trace the nine curves by numerically controlling the torch (1) and the magnetic field detector (b) which is rotatably coupled thereto. In this case, II! iK, the arc welding robot using the Teiching playback method, improves the accuracy of this welding pattern.

However, in the above embodiment, the torch (to) and the magnetic field detector (to) are rigidly coupled, and the torch (to) is rotated repeatedly, so that the magnetic field detector (to) is It should be added that a signal like that shown in FIG. 11 can be obtained even if the welding line is crossed.

In this method, the structure of the coupler is simple.

Furthermore, it is very effective because even if the torch rotates repeatedly, it does not have any adverse effect on welding. In addition, we applied a teaching play pack type nark welding robot (K) to confirm that it accurately follows a gently curved welding line with a radius of curvature of 50W or more.

Next, another embodiment of controlling the position of the torch of an arc welding robot will be described.

As shown in Fig. 12, two magnetic field detectors (52a) and (32b) are fixed to the torch (to) and power is distributed by straddling the welding 1i (71). i
This is an attempt to correct the deviation of the wire electrode a11 from the welding II (71) by the difference in the leakage magnetic field signals received by the two magnetic field detectors (52a) and (32b). , (32b) to the welding line (7
) It has been found that the welding arc @ can accurately follow the welding line a) by setting the width to be approximately twice that in the air gap.

This method depends on how the magnetic field detector is made, but it is difficult to copy the weld line of a general Ku fillet or other weld shape.
I can't believe anything. In addition, in a welding shape such as one overlapping, the distribution in the y direction of the leakage magnetic field from the weld line becomes symmetrical as shown in Fig. 10 (fkb), so two magnetic field detectors (32
a).

It is necessary to correct the signal from (52b) in advance.

In the above embodiments, a TIG welding machine was used as an example, but other welding machines that flow a large welding current may be used.

For example, it goes without saying that it can be similarly applied to M/G welding machines, arc welding machines using welding rods, and even resistance welding machines.

As explained above, the present invention is a magnetic field sensor that is distributed to a predetermined position preceding a welding point and detects a leakage magnetic field generated by a welding current.

and a detection device that detects the amount of displacement from the welding line from a change in the detection signal of the magnetic field sensor, and a simple (
Since it is possible to use a magnetic field sensor that is small, robust, and easy to handle and process signals, it has a great practical effect in that workability is not impaired even when it is attached to a welding torch.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a conventional magnetic sensor. FIG. 2 is a diagram showing an example of a conventional visual sensor. Fig. 3 is a diagram for explaining the operating principle of the present invention, Fig. 4 is a distribution diagram of the leakage magnetic flux in the y direction due to the arc current in the X-axis direction, and Fig. 5 is a diagram showing the leakage flux in the y direction due to the arc current. A distribution diagram for explaining the difference in the magnetic field distribution depending on the presence or absence of a weld bead in the distribution of magnetic flux in the X-axis direction. The figure is a distribution diagram of the strength of the leakage magnetic field in the 45° direction in the overlapping joint in the X-axis direction, sth! l! O is a perspective view of one embodiment of this invention, No. 9
Figure (a) is a diagram showing a magnet gate meter which is an example of the magnetic sensor used in the present invention, Figure (b) is a partially enlarged cutaway diagram, and Figure 10 is a distribution diagram of the leakage magnetic field in the y-axis direction. Fig. 11 (a) - ((ri #i Detection signal waveform diagram depending on the position of the magnetic field sensor and the welding line. Fig. 12 is a perspective view of another embodiment of the present invention. 61/fi workpiece, IA1 Fi welding line, aFi welding bead, ast'i Gauss meter probe, ■ is arc welding torch, a2 is field detector, oll is wire electrode, (to) is feeder, (!9 is an arc. The same symbols in the figures indicate the same or corresponding parts. Agent Shin Kuzuno - Figure 8 4t? and b) varovn I! Figure 12 ψ Procedural amendment (2 patents in white) Mr. Commissioner of the Agency 1. Indication of the case: Japanese Patent Application No. 11-181121 2. Title of the invention: S* ray detection device 3. To the representative of the person making the amendment: Katayuni Kata 4. Address of the agent: ↑; Oath ↓ F Marunouchi 2 Chome 2-3 In-house + xtaaqc + s id + q child t-t -4Ai Subject of amendment A41F Claims 1 Detailed description of the invention and brief description of drawings column 1 Contents of amendment 1) Patent claims in the specification 2) The specification is amended as follows. (1) Claims after the above amendment (1) Arranged at a predetermined position preceding the welding point. 2) The specification is amended as follows. 9. A welding line detection device comprising: a magnetic field sensor that detects a leakage magnetic field generated by an electric current; and a detection device that detects the amount of displacement from the welding line based on a detection signal from the magnetic field sensor. The welding line detection device according to claim 1, comprising a mechanism for oscillating. (3) A mechanism for coupling a magnetic field sensor and an arc welding torch to repeatedly rotate the arc welding torch,
The welding line detection device according to claim 2, wherein the magnetic field sensor oscillates across the welding line. (4) %i claim 1, which comprises a plurality of magnetic field sensors arranged so as to sandwich the bath contact*, and a detection device that detects the number of displacements from the welding line based on the difference in detection signals of these magnetic field sensors. Welding line detection device described in Section 1. (5) The weld line detection device according to any one of claims 1 to 4, wherein the magnetic field sensor is a Hall element. (6) Claims 1 to 4, wherein the magnetic field sensor is a magnet gate meter. The welding line detection device according to any one of Item 4.

Claims (1)

[Claims] (1) Arranged at a predetermined position preceding the welding point. A welding line detection attachment comprising a magnetic field sensor that detects a leakage magnetic field generated by a welding current, and a detection device that detects an amount of displacement from the welding line based on a detection signal of the magnetic field sensor. (21) The welding line detection device according to claim 1, which includes a mechanism for oscillating the magnetic field sensor across the welding line. (3) A magnetic field sensor and an arc welding torch are combined, and the arc welding torch is repeatedly operated. Equipped with a mechanism to rotate,
The weld line detection device according to claim 2, wherein the magnetic field sensor oscillates across the weld line. (4) An fc comprising a plurality of magnetic field sensors arranged so as to sandwich the welding line, and a detection device that detects the amount of displacement from the welding line based on the difference in detection signals of these magnetic field sensors.
% Welding line detection device according to claim 1. (6) The welding line detection device according to any one of claims 1 to 4, wherein the magnetic field sensor is a Hall element. (6) The welding line detection device according to any one of claims 1 to 4, b, wherein the magnetic field sensor is a magnet meter.