JPS6348638B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention monitors the welding arc portion with a television camera, processes the video signal of the camera, detects the welding arc length, weld core protrusion dimension, etc., and detects the detected value. The present invention relates to a welding condition detection method that enables high-quality welding to be performed by controlling the welding condition.

Generally, in consumable electrode type automatic welding, there is a close relationship between the welding arc length and the arc condition, so it is desirable to control the arc length when performing high quality welding.

However, it is difficult to directly detect the arc length, and therefore, in conventional welding, other factors related to the arc condition, such as welding voltage and welding current, are currently controlled or manipulated.

On the other hand, when multilayer welding is performed using a consumable electrode type automatic welder, the weld layer increases as welding progresses, and the groove bottom rises, so the distance between the power supply tip and the base metal (hereinafter referred to as extension) becomes smaller. ,
In order to perform good welding, it is necessary to raise the power supply tip and keep the extension constant. In narrow gap welding of thick plates, the vertical movement of the power supply tip is especially important. For example, if the extension becomes too small, welding arc will be generated from the power supply tip and the power supply tip will melt into the base metal, resulting in weld cracking. Welding defects such as
This repair will require a great deal of effort and time.

Conventionally, therefore, control based on welding current and voltage has been used to control extension by moving the power supply chip up and down. In other words, when a constant voltage power source is used, there is a relationship between welding current and the size of the extension as shown in Figure 1.
Utilizing this, the welding current value is controlled by vertically moving the power supply chip, thereby controlling the extension to a constant value.

However, the welding current value and welding voltage value do not depend only on the size of the extension;
It changes depending on the welding core supply speed, groove shape, base metal temperature, etc., so if the influence of changes in these welding conditions during welding cannot be ignored, controlling using welding current and voltage may not be effective. Otherwise, the extension may be too small, and a detection method that does not depend on welding conditions is required.

By the way, as mentioned above, when a constant voltage power source is used, the welding arc length is almost constant as the extension changes, and the length of the core wire protruding from the power supply chip changes depending on the extension. The melting speed of the weld core depends on the core protrusion dimension, and this core melting speed is an important factor in the welding conditions. Therefore, when performing multilayer welding by consumable electrode automatic welding, the core wire It is desirable to detect the protrusion size and control the vertical movement of the power supply chip so that the protrusion size remains constant.

Taking the above points into consideration, the present invention monitors the welding arc portion with a television camera, integrates the video signal of the scanning line of the camera within one scanning period, and converts it into an integral value series related to the scanning line number. , this integral value series is processed to detect the welding arc length, weld core protrusion dimension, etc. Next, this invention will be described in detail with reference to the drawings from FIG. 2 showing one embodiment of the invention. Explain.

First, in FIG. 2 showing a schematic configuration, 1 is a welding base material, 2 is an I-type narrow gap, 3 is a welding torch of a consumable electrode type automatic welding machine, 4 is a power supply tip, 5 is a welding core wire, 6 7 is an arc portion, and 7 is a television camera (hereinafter referred to as TV camera) attached to the shaft of the welding torch 3 so that the direction of the horizontal scanning line is perpendicular to the groove line of the groove 2. The welding arc part within the groove is monitored along the weld line from an obliquely upper direction of the groove. 8 is a detection device, and 9 is a monitor.

As shown in FIG. 3, if the TV camera 7 monitors the welding arc section at an inclination angle of θ and a monitor image as shown in FIG. 4 is obtained, the apparent welding arc length L in the monitor image is ₁ , that is, the distance from the center end of the weld core 5 to the boundary of the arc portion 6, and the apparent weld core protrusion dimension _L2 ,
That is, the distance from the lower end of the power supply chip 4 to the center end of the welding core 5 is the true welding arc length l ₁ and the true welding core protrusion dimension l ₂ shown in FIG. 3, respectively.
Corresponding to this, there is a relationship of l ₁ =L ₁ cos/cos(θ−) l ₂ =L ₂ cosθ. Here, as shown in FIG. 3, represents the spread angle in the vertical cross section of the arc portion 6. Therefore, by determining L ₁ and L ₂ from the monitor image in FIG. 4, l ₁ and l ₂ can be easily determined. In addition, in FIGS. 3 and 4, 10 and 11 are a high brightness arc part and a low brightness arc part of the arc part 6.

Next, a method of detecting the apparent welding arc length L ₁ and the apparent weld core protrusion dimension L ₂ using the monitor image obtained by the TV camera 7 will be described.

FIG. 5 shows the arc portion 6 of the monitor image in FIG.
12 is the molten pool, which cannot be seen in the image if the direction in which the TV camera 7 is attached to the welding torch 3 and the welding progress direction are the same, and even if both directions are reversed. For example, it may look like the same figure. In addition, a to f are scanning lines corresponding to each part of the monitor image, a is the upper end of the arc portion 6, b is the upper end of the high brightness arc portion 10, c is the center end of the weld core line 5, and d is the high brightness the lower end of the arc portion 10;
e indicates the scanning line at the lower end of the arc portion 6, and f indicates the scanning line at the lower end of the molten pool portion 12, respectively. Therefore, the apparent welding arc length L ₁ is given by the number of scanning lines between c and e, and by finding the scanning line numbers of c and e and subtracting the scanning line number of c from the scanning line number of e. The number of scanning lines between c and e is obtained. By the way, the TV camera 7 is attached to the shaft of the welding torch 3, and the lower end of the power supply chip 4 is always at a fixed position on the monitor image, so the apparent weld core protrusion dimension _L2 is equal to the weld core 5. c at the center edge of
If you extract the scan number of , it will be given.
In other words, the dimension L ₂ ′ from the upper end of the monitor image to the lower end of the weld core 5 has a constant deviation L _{2 ′} −L ₂ from the weld core protrusion dimension L 2 , which affects the purpose of detection. Instead, the weld core protrusion dimension L ₂ is indirectly determined.

FIG. 5 shows that the video signals of each horizontal scanning line of the TV camera 7 are integrated within one horizontal scanning period, and
The corresponding scanning line number is shown on the vertical axis and the integral value is shown on the horizontal axis, and the monitor image, which is a function of two-dimensional coordinates, is compressed and transformed into a function of the one-dimensional coordinate of the scanning line number, This is converted into an integral value series regarding scanning line numbers. At this time, the correspondence between Fig. 5 and the same figure can be explained by the difference in brightness of each part inside the groove and the change in its area. The brightness changes in the order of the pool part 12, the base material 1, and the weld core 5, and the integral values of each part show large differences.
For each scanning line of f, the change in the integral value becomes large, while for other scanning lines, the change in the integral value is due to a change in the area of the corresponding portion, and shows a gentle change. Therefore, the boundaries of each part of the monitor image can be determined based on the integral value series, and the scanning line numbers of c and e can be determined. Here, as shown in FIG. 5, when the difference value series is calculated from the obtained integral value series, the absolute value of the difference value series becomes large in the scanning lines a to f, and
The difference value between c shows a positive value, the difference value between d and f shows a negative value, and a maximum value exists in the integral value series between c and d. Therefore, candidates a to f can be found from the size of the difference value series, and furthermore, both ends of the interval having the maximum value of the integral value are c and d, and the scanning line number of c is smaller than d. From this, the scanning line number of c can be found, and on the other hand, e can be found by utilizing the fact that it is the second scanning line number from c among the candidates found from the difference value series.

Then, if the integral value series is {Si} and the difference value series is {Di}, the scanning line number of c can be determined by the flowchart shown in FIG. That is, while sequentially updating the scanning line number, a difference value larger than a predetermined value δ is detected from the difference value series, the scanning line number i of the detected difference value is stored, and the maximum value is detected from the integral value series. However, when a local maximum value is detected, the scanning line number i stored immediately before that value is set as the scanning line number c.

In addition, the welding arc length shown in Figure 7 is
L ₁ is a block circuit diagram for detecting the weld core protrusion dimension L ₂ , in which the video signal of the monitor image obtained from the TV camera 7 is converted into an integral value series related to the scanning line number in the integrating circuit 13. death,
The integral value series is converted into a difference value series in the difference circuit 14, and the output signals from both circuits 13 and 14,
In the logic circuit 15, the scanning line numbers of c and e are determined by logical determination as shown in the flowchart described above. Note that 16 indicates each circuit 13, 14, 1
This is a control circuit that controls the operation timing, etc. of 5.

Therefore, according to the embodiment, the video signal of each horizontal scanning line of the TV camera 7 monitoring the welding arc portion is integrated within one horizontal scanning period and converted into an integral value series related to the scanning line number, By processing the integral value series to obtain the scanning line numbers corresponding to the lower end of the weld core line 5 and the lower end of the arc portion 6, respectively, and calculating both scanning line numbers, the welding arc length,
It is possible to accurately detect the protruding dimensions of weld core wires,
It is possible to control the arc length with high precision and perform commercial quality welding.Furthermore, even in multi-layer welding, the vertical movement of the power supply chip 4 can be controlled with high precision to keep the extension constant. It is possible to perform good welding.

In the above embodiments, an I-type narrow groove was used, but other groove shapes can be used without much difference.

As described above, according to the welding state detection method of the present invention, the welding line is detected by the television camera attached to the welding torch shaft of the consumable electrode type automatic welding machine so that the direction of the horizontal scanning line is perpendicular to the groove line. The arc portion within the groove is monitored from the diagonally upper direction of the groove along the groove, and the video signal of each horizontal scanning line of the camera is integrated within one horizontal scanning period to obtain an integral value series regarding the scanning line number. The scan line numbers corresponding to the lower end of the arc portion and the weld core end are determined from the integral value series, and the arc length and weld core protrusion dimension are detected by calculating the two scan line numbers. As a result, welding conditions such as arc length and welding core protrusion dimensions can be accurately detected, and welding conditions such as arc length control and vertical movement control of the power supply chip can be controlled with high precision, resulting in high quality. can be welded.

[Brief explanation of the drawing]

Fig. 1 is a diagram of the relationship between the power supply chip, the distance between base materials (extension), and welding current in consumable electrode automatic welding, Fig. 2 and the following drawings show an embodiment of the welding state detection method of the present invention, Figure 2 is a schematic configuration diagram, Figure 3 is a partial side view, Figure 4 is a monitor image of the welding arc, Figure 5 is an enlarged view of Figure 4,
The same figure is a relationship diagram between the scanning line number and the integral value in the same figure, the same figure is a relationship diagram between the scanning line number and the difference value in the same figure, Figure 6 is a flowchart, and Figure 7 is a block circuit diagram. . 2... I-type narrow gap, 3... Welding torch, 5... Welding core wire, 6... Arc portion, 7... Television camera.

Claims (1)

[Claims] 1 Using a television vision camera attached to the welding torch shaft of a consumable electrode automatic welding machine so that the direction of the horizontal scanning line is perpendicular to the groove line, the inside of the groove is scanned from diagonally above the groove along the weld line. At the same time, the video numbers of each horizontal scanning line of the camera are integrated within one horizontal scanning period to convert into an integral value series regarding the scanning line number, and from this integral value series, the lower end of the arc part is monitored. . A welding state detection method, characterized in that scanning line numbers corresponding to the ends of the welding core are obtained, and arc length and protrusion dimension of the welding core are detected by calculating the scanning line numbers.