JPS61182884A - Control device of molten pool width - Google Patents

Abstract

PURPOSE:To control the molten pool width constant and to perform the welding of high quality by comparing the measuring signal transmitted from molten pool width measuring circuit and the set signal from molten pool width setting circuit and by controlling the welding current so as to reduce the difference in both signals. CONSTITUTION:The image of molten pool picked up by the optical fiber 2 which is set up on welding part 3 is made incident on linear image sensor 5. The photodiode train 6 of the sensor 5 can take off the video signal of linear shape to pass the maximum width of the molten pool 9 due to it being set up so as to intersect at right angles the welding direction of the molten pool 9. The video signal is fed to binarizing processing circuit 7, the binarized signal is fed to molten pool width measuring circuit 11 and is outputted to comparing circuit 13 as the molten pool width setting signal. The set signal set up by the molten pool with measuring signal and molten pool width setting circuit 14 is compared by the comparison circuit 13, the deviation is fed to welding current control circuit 15 and the peak current is varied in proportion to the deviation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a device for controlling the molten pool width to a constant value in visible arc welding such as TIG or MIG.

[Conventional technology]

Regarding the measurement and control method of the molten pool width in TIG welding, please refer to BuO? 7 (Vroman) et al.
d.

J, vol. 55, p. 742, 1976) is publicly known.

[Problem that the invention seeks to solve]

However, in this conventional control method, the response of the control system is 10
It is too slow at ~20 seconds to be practical.

Furthermore, since there is no online measurement and control technology for the molten pool width, the molten pool width is affected by disturbances during welding, leading to quality deterioration and becoming an obstacle to automatic welding.

[Means for solving problems]

In order to solve the above-mentioned problem of the conventional joint point, the present invention includes an optical fiber that is placed near the welding torch and receives light from the welding part;
an optical filter that adjusts the amount of received light and a received light wavelength range; and a photodiode row in which photoelectric elements are arranged in a line; a molten pool width measuring circuit that detects the brightness of the molten pool in the welding zone using a photodiode array, and defines the molten pool width as the range in which the brightness is above a certain level during low current during pulse welding; , a molten pool width setting circuit for setting the width of the molten pool to a predetermined value, and a comparison circuit for inputting and comparing the measurement signal from the molten pool width measuring circuit and the setting signal from the molten pool width setting circuit. and a welding current control circuit that receives the signal from the comparison circuit and controls the welding current so that the difference between the measurement signal and the setting signal becomes small.

[For production]

Light is received by an optical fiber from a welded part that is pulse-welded by a welding torch, and the received light amount and wavelength range are adjusted by an optical filter before being sent to a linear image sensor. The optical image of the weld zone sent to the linear image sensor is projected so that the molten pool intersects with the photodiode array of the linear image sensor, and the photodiode array detects the brightness of the molten pool in the direction perpendicular to the weld bead. . The brightness detected by the photodiode array is determined by a molten pool width measurement circuit as the range in which the brightness is above a certain level during pulse welding at low current, and a measurement signal of the molten pool width is output to a comparison circuit. The comparator circuit compares the molten pool width with a setting signal preset by the molten pool width setting circuit.

The comparison signal is sent to the welding current control circuit, and if the measurement signal is larger than the setting signal, the average welding current is reduced to reduce the difference between the two signals, and conversely, if the measurement signal is smaller than the setting signal, the difference between the two signals is reduced. The average current is increased to reduce the difference between both signals.

In addition to this, the molten pool width is always controlled to be constant within a small error range of the set value by rapid feedback control.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 to 4 show an embodiment of the present invention, and T
Behind the welding torch (1) for IG welding, the end of an optical fiber (2) made of a bundle of fine-diameter glass fibers is installed at a distance of 951111 at an angle of 52' to the welding part (3), for example. , a filter (4) is attached to the other end of the optical fiber (2).
) is provided with a linear image sensor (5).

The linear image sensor (5) includes, for example, a photodiode array (6) in which 512 photodiodes are arranged in a straight line.
), the photodiode array (6) intersects the molten pool (9) directly below the electrode of the welding part optical image (8) incident on the linear image sensor (5) from the optical fiber (2), and The position is set to be located in a direction perpendicular to the direction of the weld bead (g) (welding direction).

The photodiode array (
The luminance signal obtained in step 6) is sent to a binarization processing circuit (7)), and the portion exceeding a certain luminance signal determined as a threshold value is extracted in the binarization processing circuit (7). Value.

The binarized signal obtained by the binarization processing circuit (7) is sent to the molten pool width measuring circuit αρ, a timer circuit (6) is connected to the molten pool width measuring circuit αη, and the timer circuit (2 ), the binarized signal is extracted in synchronization with the low pulse welding current of the welding torch (1) and the molten pool width is measured.

The molten pool width measurement signal measured by the molten pool width measurement circuit αυ is sent to the comparison circuit (to), and the comparison circuit (to) compares it with the molten pool width setting signal set in advance by the molten pool width setting circuit α→. , a comparison signal is sent to the welding current control circuit (g) to control the welding current of the welding power source (to) of the welding torch (1).

With the above configuration, for example, using 8M41 as a test piece and using a downward bead-on plate without a filler wire,
Peak current time is 100mt.

When pulse welding is performed with a pace current time of 26 m5 and a pace current of 2OA, the above-mentioned pulse welding current is supplied to the welding torch (1) from the welding power source (g), and a molten pool (9) is formed by the arc. be done.

The molten pool image captured by the optical fiber (2) installed in the welding part (3) is incident on the IJ near image sensor (5) via the filter (4). The photodiode array (6) of the linear image sensor (5) is installed so as to cross the molten pool (9) directly below the electrode at right angles to the welding direction, so that it is arranged in a straight line passing through the maximum width of the molten pool (9). video signals can be extracted.

The video signal is sent to a binarization processing circuit (7), and in the binarization processing circuit (7), a signal exhibiting a luminance equal to or higher than an appropriately selected threshold value is selected and binarized. . Part 2
The value signal is sent to the molten pool width measurement circuit αη and outputted to the comparison circuit a [present] as a molten pool width measurement signal. At this time,
In order to measure the molten pool width while avoiding the influence of the arc light, the welding current is pulsed by the timer circuit as described above, and the molten pool width measurement signal is taken out when the arc light is weak and the current is low.

In addition, in preliminary experiments, the peak current and welding speed were each set to 1.
The output of the molten pool width measurement circuit αυ when varied between 50 and 250A and 2 and 10c1n/rrLtn is within an error of ±0.2 min from the bead width measured from the actual bead after welding is completed. I was doing it.

The molten pool width measurement signal and the setting name preset by the molten pool width setting circuit αa are compared in the comparison circuit αa, the deviation between the set value and the measured value is determined, and the deviation signal is sent to the welding current control circuit. θG, and the peak current is changed in proportion to the deviation. In other words, if the measured value is larger than the set value, the peak current is proportionally reduced, and if the measured value is smaller than the set value, the peak current is proportionally increased, so that the deviation is (within the error range) through feedback control.

It should be noted that the molten pool width control device of the present invention is not limited to the above-described embodiments, and it goes without saying that various changes can be made without departing from the gist of the present invention.

〔Effect of the invention〕

As described above, according to the molten pool width control device of the present invention, the molten pool width can be controlled by ±0.2 m using a linear image sensor.
It is possible to measure within an error range of s, and by feeding back the obtained molten pool signal to the welding current, the molten pool width can be controlled to a constant level, enabling high-quality welding and automatic welding. It exhibits various excellent effects such as:

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the apparatus of the present invention, FIG. 2 is an explanatory diagram of the part (■) in FIG. 1, and FIG. 3 is an explanatory diagram showing the operating state of the binarization processing circuit in FIG. 1. FIG. 4 is a diagram showing the operating state of the timer circuit of the device in FIG. 1. (1) is a welding torch, (2) is an optical fiber, (3) is a welded part, (5) is a linear image sensor, (6) is a photodiode array, (7) is a binarization processing circuit, (9) is the molten pool, Q() is the weld bead, αη is the molten pool width measurement circuit, (
2) is a timer circuit, α-is a comparison circuit, α→ is a molten pool width setting circuit, and (c) is a welding current control circuit.

Claims (1)

[Claims] 1) An optical fiber arranged near the welding torch receives light from the welding part, an optical filter that adjusts the amount of received light and the wavelength range of the received light, and a photodiode row in which photoelectric elements are arranged in a row, and the optical fiber receives light by the optical fiber. The linear image sensor has the photodiode array oriented in a direction perpendicular to the direction of the weld bead in the optical image of the weld zone, and the photodiode array detects the brightness of the molten pool in the weld zone, which is constant during low current during pulse welding. A molten pool width measuring circuit that sets the molten pool width to the range showing the above brightness, a molten pool width setting circuit for setting the molten pool width to a predetermined value, and a measurement signal from the molten pool width measuring circuit. a comparison circuit that inputs and compares a setting signal from a molten pool width setting circuit; and a welding current control that receives the signal from the comparison circuit and controls the welding current so that the difference between the measurement signal and the setting signal becomes small. A molten pool width control device characterized by comprising a circuit.