JPS5890376A - Arc welding device - Google Patents

Abstract

PURPOSE:To start arcs without using any high frequency generator by starting the arcs with the starting current determined by the signal from a generating means for starting signal and shifting the arc firing to the sequence of welding current by the operation of the starting signal. CONSTITUTION:A torch switch is closed to obtain an arc starting signal from a generating circuit 14 for starting signal and the signal is stored temporarily in a logical circuit 13. The electrode of the welding torch is short circuited with base metal and is detached immediately therefrom, by which an arc is generated. The output signals when the torch switch is opened and the digital output signal (output of a signal converter 12) detected with a current detecting circuit 10 are ANDed with the circuit 13 and a switch 15 is changed over by the output signal thereof, by which the current is changed over to the ordinary welding current value set with a setter 17 for welding current.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an arc welding device that performs welding using a non-consumable electrode, and more particularly to an arc welding device that can easily start an arc without using a high frequency generator. It is.

In tungsten/inert fist gas arc welding equipment that performs arc welding using non-consumable electrodes, high frequency and high voltage is applied only at the time of starting to start the arc in order to facilitate arc starting. Figure 1 is a circuit diagram of an employee with such a circuit function, where: 3-phase Takaishi AC power supply, 2 a transformer, 3 a rectifier consisting of 6 square meters for controlling the welding current, 4 is a smoothing reactor,
5 is a high frequency generator including a coupling coil, and 6 is a load, which is composed of a TIG torch and a base material.

In such a device, a high-frequency discharge is caused at the time of arc start and then the welding arc is started, so that the noise generated from the high-frequency generator 5 has an adverse effect on the busyness of other equipment. Furthermore, if a cable-connected welding torch is extended from the welding device main body, the high-frequency voltage will attenuate along the way, making it difficult to start the arc. Furthermore, since it includes a high-frequency generator, there are limits to the structure of the shed, and it is also expensive.

In order to solve this problem, we did not install a high-frequency generator, but instead brought the torch electrode into contact with the base metal at the time of arc start to flow a short-circuit current, and the phosphorus then pulled the torch electrode away from the base metal to form a gap. However, a so-called touch start method, in which an arc is started, is sometimes adopted. However, with this method, arc ignition tends to become unstable,
In order to stabilize this, K had to pass more current than necessary at the start, which had the disadvantage that the electrodes melted and were consumed. In addition, it is difficult to time the arc to ignite, and as a result, the arc has to be started many times during ignition, which may damage the base material.

SUMMARY OF THE INVENTION An object of the present invention is to provide a non-consumable electrode arc welding apparatus which eliminates the drawbacks of the prior art described above and which enables a good arc start without the need for a high frequency generator.

The present invention provides a current detection means for detecting a current outputted through a switching circuit and flowing through a load, a multi-junction current setting means for obtaining an output signal for setting a plurality of types of load currents, and a current setting means for obtaining an output signal for setting a plurality of types of load currents; Comparing the feedback signal obtained through the changeover switch means for switching the setting means and the current detection means with the current setting output signal obtained through the changeover switch means;
control means for controlling the switching circuit at a frequency P shorter than A of the commercial power supply frequency so that the output current is always the set current; and start signal generation means for generating an arc start control signal and a welding control signal; It is characterized by comprising logic circuit means for comparing the activation signal and the feedback signal and controlling switching of the changeover switch means.

The present invention will be described in detail below with reference to FIGS. 2 and 3.

First, the present invention will be explained in detail with reference to FIG.

Figure 2 shows the experimental results when the control period for controlling the switching circuit provided at the output of the rectifier circuit was set to be less than or equal to the period A of the three-phase AC power frequency in order to improve the responsiveness of the circuit. It shows the relationship between electrode diameter and starting current. Here, the reason why the period is less than A is that the control period of the conventional device is that the commercial power supply (50H, →X1m5) is controlled by a 64m thyristor, and the control period is! OAms
= 3.3 ms (approximately 3001), the arc tracking is poor, and arc breakage occurs.
As shown in the data results in the figure, in order to speed up the responsiveness of the circuit, the control period is set to s, am, or less (at least 6 times the commercial frequency) or less (at least 6 times the commercial frequency). , i.e. special X 10"
W O,05mm This is a case of Te control. Although the period of this experimental data is different from the commercial power frequency period A or less in the present invention, the response to arc is 500
H, (control period 2 m5) is sufficient.

Therefore, in FIG. 2, region A is a region in which arc starting is impossible, and arc starting is possible when the electrode diameter is smaller. On the other hand, in region C, the arc starts, but the electrode and the base metal are short-circuited, and a large current is required to generate the arc when the electrode is subsequently opened, so the torch electrode is consumed and spatter is generated, making it difficult to obtain good welding. This is an area where there is no such thing.

Then, the B region between the A and C regions (depending on the electrode diameter, lO ~
60A region) is a stable touch start region where almost no spatter occurs. This wide stability region means that the control cycle can be shortened to achieve faster response.
This has the effect of quickly following load fluctuations.

In addition, as a result of conducting similar experiments using nine conventional devices equipped with a high current supply circuit, there was almost no k in the B region, and there was no difference between the A region and the C region.
This was impractical because the arc was difficult to sustain or the current was high, causing the electrodes to melt.

Next, a different circuit configuration for realizing the experimental results shown in FIG. 2 is shown in FIG. 3 and will be explained. In the aS diagram, the same reference numerals as in FIG. 1 indicate the same components.

As shown in FIG. 3, a rectifier is provided at the output stage of the transformer 2, and a switching circuit 8 consisting of a transistor for obtaining a high-frequency pulse output (switching frequency) is provided at the output stage. It is. 9 is a relatively small reactor; 10 is a current detection circuit that detects the current flowing through the load 6; 11 is a switching control circuit that controls the switching circuit 8 to turn on and off at a control period equal to or less than each commercial power supply period; Feedback signal from circuit 10 and switch 15
The switching circuit 8 is controlled so that the set current is always obtained. Here, the control cycle is set to be less than or equal to the commercial power supply cycle A, which is rounded to ensure fast response and to quickly follow load fluctuations.
It is.

12 is a signal converter that converts the current detection signal from the current detection circuit 10 into a digital signal; 14 is a starting signal generation circuit that is attached to the welding torch and obtains a starting signal by switching operated at the time of arc start; 13, It is a logic circuit having a temporary memory function that calculates the logical product of the outputs of the signal converter 12 and the starting signal generating circuit 14, and its output controls switching of the changeover switch 16 that selects the set current. In addition, the arc start current setting device 16 is configured to set the arc start current setting device 16 to 3, which is included in the touch start stable region, for example, as shown in FIG.
Although the welding current setting device 17 is set to 0A, the welding current setting device 17 is set to output a higher current value. Further, switching to the crater current setting device 18, which is installed as necessary, is used when the welding current setting device 17 is switched to and then the current is supplied as the crater current when starting again.

Next, FIG. 4 shows the operation of the circuit shown in FIG. 3.

This will be explained according to FIG.

First, a torch switch attached to a welding torch (not shown) is closed, a shear start signal is obtained from the start signal generation circuit 14, and the logic circuit 13 is busy. Then, when the welding torch electrode is short-circuited to the base metal and immediately pulled apart, an arc is generated from K (touch start stable region B), and a start current waveform as shown in FIG. 4 is obtained. Then, logic circuit 1 calculates the logical product of the output signal when the torch switch is opened (OFF), 8, and the digital output signal (output of signal converter U) output from current detection circuit 10.
3, and the switch is switched according to the output signal, and the welding current value is changed to the normal welding current value set by the welding current setting device 17K. Further, the subsequent output voltage waveform is as shown in Figure 1IE4.

In this way, when starting an arc, the welding torch electrode and base metal are short-circuited to supply a starting short-circuit current determined by the start signal, and then the electrode and base metal are opened. Since the arc is ignited and then the starting signal is manipulated to shift to the sequence of welding current that produces a normal arc, it is possible to stably start the arc without installing a high-frequency generator. became possible.

In addition, as shown by the broken line in Fig. 3, the crater current setting device 1
8 will be described with reference to the time chart in FIG. That is, as shown in the voltage waveform, FIG. 5 shows the case where the welding torch electrode and the base material are first short-circuited, and then the current is turned on. And a start signal K from the start signal generation circuit 14- obtained by the torch switch.

This is the addition of the crater signal. Therefore, this K
The circuit operation is as follows: First, by turning on the torch switch (not shown), the torch switch is connected to the arc start current setting device 16, and a start current is supplied.Then, by turning off the torch switch, the changeover switch "is connected to the welding current setting device 17K". The connection is switched and the welding current is output.Furthermore, by turning on the torch switch again, the changeover switch 15 is switched to the crater current setting device 18K, and the crater current as shown in FIG. 5 is supplied.And By turning off the arc again, the arc stop control is performed. According to the same circuit configuration, problems caused by the crenitter during arc generation can be solved.

Although the above-described embodiments have been described using DC TIG welding as an example, the present invention is not limited thereto and can also be applied to AC TIG welding. Furthermore, the purpose can be achieved by adding a similar circuit function to an inverter system that controls the switching circuit on the primary side of the transformer. play.

As explained above, according to the arc welding apparatus of the present invention, a good arc start can be performed stably and with little electrode wear even without installing a high frequency generator. In addition, since a high frequency generator is not required, radio interference caused by high frequency generation can be eliminated, and the weight of the shed can be reduced. Furthermore, the one-touch start is reliable and the arc start position is easy to determine. Furthermore, the arc starting current and the welding current can be controlled by switching using a starting signal such as a torch switch, which has advantages and effects such as very simple operation.

[Brief explanation of the drawing]

FIG. 1 is an overall circuit configuration diagram of a conventional arc welding device, and FIG. 2 is a diagram for explaining the principle of the present invention, and is a characteristic diagram showing the relationship between torch electrode diameter and starting current. FIG. 3 is an overall circuit configuration diagram of an arc welding apparatus showing one embodiment of the present invention, and FIGS. 4 and 5 are time charts for explaining the circuit operation of FIG. 3. 1... AC power supply, 2... Transformer, 6... Load, 7
... Rectifier circuit", 8... Switching circuit, 9...
・Reactor. 10... Current detection circuit, 11... Switching control circuit, 12... Signal conversion circuit, 13... Logic circuit,
14... Starting signal generation circuit %15... Changeover switch, 16... Arc start current setting device, 17...
Welding current setting device, 18...crater current setting device. Patent Applicant Hitachi Seiko Co., Ltd. Agent Patent Attorney Tadashi Akimoto Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. When an arc occurs, a non-consumable torch electrode and a base metal are short-circuited to supply a short-circuit current, and then the torch electrode and the base metal are opened to ignite the arc. This is an arc welding device using a touch start method, which includes a current detection means for detecting the current outputted through a switching circuit and flowing through the load, and multiple current settings for obtaining output signals for setting multiple types of load current. means, a changeover switch means for switching between the plurality of current setting means, and a feedback signal obtained through the current detection means and a current setting output signal obtained through the changeover switch means, and the output current is always at the set value. a control means for controlling the switching circuit at a cycle shorter than A of the commercial power supply frequency so as to generate a current; a starting signal generating means for generating an arc start control signal and a welding control signal; a cough starting signal and the feedback signal; and logic circuit means for switching and controlling the changeover switch means, and when starting the arc, the starting current is determined by the starting signal from the starting signal generating means, and the arc ignition is started. An arc welding device characterized by a configuration that allows the sequence of welding current to be changed by manipulating signals. 2. The arc welding apparatus according to claim 1, wherein the start signal generating means is controlled by a switch signal of a welding torch.