JPH02280965A - Arc welding machine - Google Patents

Abstract

PURPOSE:To maintain a constant depth of penetration of base metal with respect to variation of the arc length in the case wherein the arc length is varied and current density of the base metal is being changed by detecting the arc length and regulating the current density according to its value. CONSTITUTION:During arc welding, a sampling period to measure the arc length is provided and during this period, an arc current is changed into a sampling current for measuring the arc length to measure the arc voltage at this time. The reference arc voltage of the reference arc length corresponding to this sampling current is compared with the measured arc voltage. When the arc length is longer than the reference arc length, the arc current is increased and when the arc length is shorter than the reference arc length on the contrary, the arc current is decreased. By this control, the current density to the base metal 3 can be maintained constant and the change of the depth of penetration due to arc length variation can be obviated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an arc welding machine control system when the arc length changes in an arc welding machine having current drooping characteristics.

(Prior Art) Generally, when performing arc welding using a non-consumable electrode, an arc welding machine with current drooping characteristics is used for reasons such as arc stability against arc length fluctuations and electrode life. The output characteristics of this type of welding machine are as shown in Figure 2, where the arc length changes and the arc load line becomes a.
The arc can be maintained stably even if the current changes from b to b.

(Problem to be solved by the invention) However, in the conventional arc welding machine described above, when the arc length changes, even if the arc current is constant, the arc itself spreads as shown in Figure 3. , even if the amount of heat input to the base metal does not change, the current density in the base metal changes and the weld penetration depth of the base metal changes greatly. For this reason, in conventional arc welding machines, fluctuations in the arc length must be prevented as much as possible, which has placed an excessive burden on the operator. Furthermore, even in automatic welding, it is unavoidable that the arc length will fluctuate due to deformation of the base metal, wear of the electrode, limits on tracing accuracy, etc., and this may cause defects in the welding result, especially insufficient penetration of the base metal. there were.

The purpose of the present invention is to eliminate the drawbacks of the conventional method, and when the arc length fluctuates and the current density of the base metal is about to change, it detects the arc length and adjusts the current density according to that value. An object of the present invention is to provide an arc welding machine that can eliminate variations in the penetration depth of a base metal due to variations in arc length.

(Means for solving problems) The arc welding machine of the present invention has one end as a welding electrode.

A power source whose other end is connected to the base metal and generates an arc between the welding electrode and the base metal, a current detection means inserted in series with the arc, and a first current setting means that sets the output current of the power source. and a second current setting means, a switching means for alternately switching the output current values set by the first current setting means and the second current setting means, and an output current set by the second current setting means. and function generating means for inputting the arc voltage and generating a signal as a function of the arc voltage. It also has means for adding the output signal of the function generation means to the output signal of the first current setting means, and further includes means for switching the output signal of the function generation means between the first current setting means and the second current setting means. It has means for changing the time ratio of the output current value inputted to the switching means and set by the first current setting means and the output current value set by the second current setting means.

(Function) Arc voltage and arc length have the relationship shown in Figure 4, and if the arc voltage is measured when a constant arc current is flowing, the arc length can be found as a function of the arc voltage. For this reason, a sampling period for arc length measurement is provided during arc welding, and during this period, the arc current is changed to a sampling current for arc length measurement, and the arc voltage at this time is measured. By comparing the reference arc voltage of the reference arc length corresponding to this sampling current with the measured arc voltage, if the arc length is longer than the reference arc length, increase the arc current, and conversely increase the arc length to the reference arc length. If it is shorter than the arc length, reduce the arc current.

With this control, the current density to the base metal can be kept constant, and changes in the penetration depth due to fluctuations in the arc length can be eliminated.

(Example) An embodiment of the present invention will be described based on FIG.

FIG. 1 is a schematic explanatory diagram of an arc welding machine according to the present invention. In the figure, numeral 1 denotes a main circuit section which is composed of semiconductor switching elements and the like and controls the output current, and includes a rectifier circuit, a smoothing circuit, and a switching circuit. One end of the output of the power source 1 is connected to the electrode 2, and the other end is connected to the base material 3, and an arc 4 is generated. The shunt 5 detects an arc current, which is input to one end of an error amplifier 7 via an arc current detector 6 including an amplifier circuit. The output current setting device 8 is used to determine the center value of a predetermined arc current, and is operated by an operator. The arc voltage detector 9 detects the voltage across the arc 4.

The signal is input to the sample hold circuit 10. The sample and hold circuit IO samples the arc voltage signal in response to the signal from the timing circuit 11, holds the value, and outputs 1
It operates to send to the next circuit. While the arc voltage is being sampled, the arc voltage signal is input to the function generator 12, but the arc current is also a reference current determined by the reference current setting device 13. If the sampled arc voltage is higher than the reference arc voltage when the reference current flows, the signal of the function generator 12 will be large, and the result of addition with the output signal of the output current setting device 8 performed by the adder 14 will be large. The 6-segment divider 15 switches between the output signal of the adder 14 and the output signal of the reference current setter 13 in response to the signal from the timing circuit 11, and switches between the output signal of the reference current setter 13 and the output signal of the reference current setter 13 while sampling the arc voltage.
signal appears at the output. Therefore, the signal from the reference current setter 13 is input to the other end of the error amplifier 7 during sampling of the arc voltage.

The output control circuit 16 controls the power supply 1, and the arc current becomes the reference current set by the reference current setting device 13.

Also, outside the sampling time, the output signal of the adder 14 is input to the error amplifier 7, but if the arc voltage is higher than the reference arc voltage, the output signal of the adder 14 is the output signal of the output current setting device 8. Since the arc current is larger, the arc current increases. Conversely, if the arc voltage is lower than the reference arc voltage, the arc current will decrease.

In FIG. 1, a configuration is shown in which the output of the adder 14 is changed as a means for changing the arc current, but by adding the output of the function generator 12 to the timing circuit, the sampling time is changed to the ratio of the non-sampling time, Alternatively, the sampling frequency may be changed while keeping the sampling time constant.

(Effect of the invention) According to the invention, when the distance between the base materials of the electrodes changes,
The arc current can be increased or decreased according to changes in distance, and the arc current density can be kept constant. Therefore, the penetration depth of the molten part of the base metal can be kept constant, and its practical effects are extremely large. It is.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram of an arc welding machine according to an embodiment of the present invention, FIG. 2 is a diagram showing an example of characteristics of an arc welding machine using a non-consumable electrode, and FIG. 3 is an electrode. FIG. 4 is a diagram illustrating the spread of an arc that occurs when the distance between base materials changes, and FIG. 4 is a diagram illustrating an example of a change in arc voltage corresponding to a change in arc length. l...power supply, 2...electrode, 3...base material. 4... Arc, 5... Shunt, 6
...Arc current detector, 7.Error amplifier, 8.
...output current setting device, 9 ...arc voltage detector,
DESCRIPTION OF SYMBOLS 10... Sample hold circuit, 11... Timing circuit, 12... Function generator, 13... Reference current setter, 14... Adder, 15... Divider, 16...
・Output control circuit. Patent applicant Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] (1) a power source having one end connected to the welding electrode and the other end connected to the base metal and generating an arc between the welding electrode and the base metal; a current detection means inserted in series with the arc; a first current setting means and a second current setting means for setting the output current of the power supply; the first current setting means;
a switching means for alternately switching the output current value set by the second current setting means; a means for detecting an arc voltage during the output period of the current set by the second current setting means; An arc welding machine characterized by having a function generating means for generating an input signal as a function of arc voltage. (2) The arc welding machine according to claim 1, further comprising means for adding the output signal of the function generating means to the output signal of the first current setting means. (3) The output signal of the function generating means is input to the switching means for switching between the first current setting means and the second current setting means, and the output current value set by the first current setting means and the second The arc welding machine according to claim 1, further comprising means for changing the time ratio of the output current value set by the current setting means.