JPS5834226B2 - How to get started - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides that in TIG welding involving an arc welding device that can be used for both AC and DC, the welding characteristics differ depending on the polarity, and deep penetration cannot be obtained with positive polarity where the electrode is the cathode and the base material is the anode. ,
On the other hand, in the case of reverse polarity where the electrode is an anode and the base material is a cathode, the penetration is shallow, but there is a cleaning effect for removing the oxide film on the base material.

Generally, when performing TIG welding of a material such as aluminum whose surface is covered with an oxide film having a high melting temperature, AC arc welding is employed because a cleaning effect is required.

Therefore, it would be convenient if one welding machine could produce two types of arc vinegar solutions, alternating and direct, but such welding machines have already been commercialized as arc welding machines that can be used for both alternating and direct uses.

As this known AC/DC arc welding machine, for example, there is one introduced in Japanese Patent Publication No. 21763/1983.

This welding machine is configured so that alternating current and direct current outputs can be extracted by changing the current extraction points in the welding current circuit.

However, with this configuration, it is necessary to perform AC/DC switching using a knife switch, an electromagnetic contactor, etc. provided in the welding current circuit, that is, a large current circuit, and switching during welding is not easy.

In addition, the alternating current of conventional AC/DC arc welding machines uses a sine wave or rectangular waveform K, but in this case, the ratio of positive and negative alternating current is approximately 1, and this ratio cannot be changed. Ta.

The present invention eliminates the above-mentioned drawbacks of the prior art and provides an AC/DC arc welding machine that can alternately switch between AC and DC arc welding during welding to obtain good welding results. The purpose is to

The present invention employs a configuration in which an AC arc welding machine 2 that receives DC as input and generates AC as output has a configuration in which the DC power is converted to AC using an inverter, and one of the switching elements of the inverter is The present invention is characterized in that a switching means is provided to make only the switching element conductive, so that arc acid liquid for both AC and DC use can be produced during welding work.

FIG. 1 is a block diagram showing an embodiment of the present invention in TIG welding.

1 is a DC power supply with a drooping characteristic that inputs three-phase AC, 2 is an electrode, 3 is a nozzle, 4 is a shielding gas, 5 is a welding arc,
6 is a base material, 7 to 10 are main thyristors constituting the inverter device, 11 to 14 are commutation circuits of each main thyristor, 15
-18 is the ignition circuit for each main thyristor.

FIG. 2 shows an embodiment of the *1 leg circuit of the inverter according to the present invention.

19 is a rectangular wave alternating current oscillation circuit whose polarity is reversed at an electrical angle of 180 degrees, 20 is a positive/negative discrimination circuit that discriminates between a positive half wave and a negative half wave, and 21 and 22 are pulse circuits that convert negative and positive signals into panels, respectively. , 23.24 is a pulse signal amplification circuit,
25 is a delay circuit that delays the pulsed signal based on the set value of the delay time setting circuit 26; 11 to 14 are commutation circuits shown in FIG. 1; 15 to 18 are ignition circuits shown in FIG. 1;
29 is a delay circuit that delays the pulse as in 5, which operates the ignition circuit 15.18 after the commutation circuits 12 and 13 are activated and the main thyristors 8 and 9 are extinguished.
．． A delay circuit 27.30 delays the pulse to the ignition circuit 16 and 17 from the pulse applied to 14, and 27.30 is an interlocking switch that is closed in the case of AC welding and opened in the case of DC welding.

In this configuration, when switch 27.30 is closed, pulse circuits 21.22 are alternately applied with equal width square wave voltages, each pulse circuit generating a pulse at the beginning of its square wave voltage.

When a pulse is generated by the pulse circuit 21, this pulse is amplified by the amplification circuit 23 and sent to the commutation circuit 12, 13.
is driven to extinguish the main thyristor 8.9.

On the other hand, the pulse delayed by the delay circuit 28 is sent to the ignition circuit i.
s and is, the main thyristor 7°10 is ignited, and a current of positive polarity (sp) flows, with the electrode 2 serving as a cathode and the base material 6 serving as an anode.

Next, when a pulse is generated by the pulse circuit 22, this pulse is delayed by the delay circuit 25 by the time set by the delay time setting circuit 26, and is amplified by the amplification circuit 24, and first the commutation circuits 11 and 14 are driven. be done.

The ignition circuits 16, 17 are then driven by the pulses delayed by the delay circuit 29.

As a result, after the main thyristors I and 10 are extinguished, a welding current of reverse polarity (RP) flows, in which the base material in which the main thyristors 8 and 9 are ignited becomes the cathode and the electrode becomes the anode.

As can be seen from the above description, by lengthening the set time of the delay time setting circuit 26, the time for positive polarity can be lengthened and the time for reverse polarity can be shortened.

Figure 3 shows how to lengthen the period of positive polarity SP,
It shows the relationship between welding voltage Va and welding current Ia when the period of reverse polarity is shortened.

Then, if switch 27 is opened, ignition circuit 15.1
No pulse is applied to 8 and commutation circuits 11 to 14,
Since the voltage is applied only to the ignition circuits 16 and 17, the main thyristors 8 and 9 continue to conduct, allowing reverse polarity DC welding to be performed.

The welding voltage vase and contact current Ia in this case are shown in FIG.

In addition, by using a relay as the AC/DC changeover switch and turning it on and off for a certain period of time, periodic switching can be performed during welding.

In FIG. 5, with the switch 27 in FIG. 2 closed,
Waveforms are shown in which positive polarity DC welding is performed for a certain period t2 and AC welding is performed for the other period t1 by opening and closing another switch 30 using an operating device (for example, a relay).

By performing welding in this manner, the good directivity of the direct current positive polarity heat concentrating arc can be utilized.

In the welding of aluminum and its alloys, by frequently repeating DC welding and AC welding, it is possible to obtain sufficiently deep penetration and at the same time to apply a cleaning action.

Further, this switching between direct current and alternating current does not need to be performed periodically, and can be switched appropriately by taking advantage of the advantages of direct current welding and alternating current welding.

Further, the present invention can also be applied to plasma welding.

FIG. 6 is a diagram showing its configuration, in which 31 is a DC power supply;
32 is the inverter shown in FIGS. 1 and 2, 33 is a plasma torch electrode, and 38 is a nozzle electrode.
Light the positive pilot arc from 9 onwards.

Plasma gas 34 is supplied into the nozzle electrode 38, and shielding gas 35 is supplied between the nozzle electrode 38 and the shield nozzle 37 outside thereof.

The output of the inverter 32 is connected between the torch electrode 33 and the base material 6, and generates a plasma arc 36 by guiding the pilot arc.

In this case, by controlling the inverter 32 during welding to alternating current or direct current, the plasma arc can also be turned into direct current or alternating current.

As explained above, in the present invention, a switch is provided in the inverter control circuit, and the output of the inverter during vinegar solution application is switched between DC and AC by turning on and off the switch. When welding alloys, by alternately repeating DC welding and AC welding, it is possible to obtain sufficiently deep penetration and at the same time to perform a cleaning action, so that beautiful and good welding results can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of a welding device according to the present invention, FIG. 2 is a circuit diagram showing an embodiment of an inverter control circuit according to the present invention, and FIGS. 2
FIG. 6 is a time chart explaining the operation of the circuit shown in the figure, and FIG. 6 is a diagram showing an example of application of the present invention. Explanation of symbols, 1...DC power supply, 2...
Electrode, 6... Base material, 7-10... Main thyristor, 11-14... Commutation path, 15-18
...Ignition circuit, 19...Princess wave AC oscillation circuit, 20...Positive/negative discrimination circuit, 21.22...
...Pulse circuit, 23, 24... Amplification circuit, 25.28.29... Song delay circuit, 26...
・Delay time setting circuit, 27.30...Switch for switching between music alternating current and direct switching.

Claims (1)

[Claims] 1 A first point comprising a DC power supply and an inverter that converts the DC output into AC, and extinguishing one pair of switching elements of the inverter and then igniting the other pair of switching elements. an arc circuit, a second ignition circuit that extinguishes the other pair of switching elements and then ignites one of the pair of switching elements, and sends an ignition signal to the first ignition circuit. A first switch that opens and closes, and a second switch that opens and closes the ignition signal to the second ignition circuit are provided, and when one of the first and second switches is closed, the other switch is closed. A dual-use arc welding device characterized by having an operating device that repeatedly opens and closes.