JPH0435007Y2 - - Google Patents

Description

[Detailed description of the invention] "Industrial application field" This invention is a DC arc welding machine that has a drooping characteristic in its external output characteristics by controlling the phase of the rectifier that converts AC power into DC power. In particular, the present invention relates to a DC arc welding machine that can be controlled to increase short-circuit current when a short-circuit such as welding between a coated welding rod and a base metal occurs.

"Prior Art" Conventionally, in this type of DC arc welding machine, as shown in FIG.
The arc current detection circuit 2 detects the arc current supplied to the coated welding rod and the base metal, and the detected value V ₁
After adjusting the detection level in the arc current setting circuit 4, the ignition circuit 3 compares it with the reference voltage _V3 of the reference voltage output circuit 5, and based on the comparison result, the ignition circuit 3 adjusts the control rectifier 1. It is now possible to control the phase of the That is, as shown in FIG. 5, the reference voltage output circuit 5 outputs a lamp voltage synchronized with the AC waveform of the AC power source 9 as the reference voltage _V3 . In the ignition circuit 3, the reference voltage _V3 is compared with the output voltage _V2 of the arc current setting circuit 4, which changes in proportion to the value of the arc current, and the reference voltage _V3 is determined as the output voltage _V2.
The ignition pulse V ₄ is output when the ignition pulse V 4 is exceeded, and the output voltage V 6 is output from the control rectifier 1 according to the change in the phase of the ignition pulse V ₄ with respect to the AC output of the AC power supply ₉ . This is for phase control. Due to this phase control, the external output characteristics of the welding output terminals 10, 10 exhibit a drooping characteristic as shown in _FIG . It can be set freely within the range of ₄ .

In addition, phase control has good followability against sudden changes in arc voltage that frequently occur during welding work, so even if there is a short circuit between the welding rod and the base metal, for example, the arc voltage will not increase rapidly. It is possible to instantly reduce the short-circuit current to a value close to the arc current value at the time of arc occurrence. As a result, the current at the time of re-arc generation is suppressed to the above-mentioned arc current value, resulting in a high-quality arc, usually called a soft arc, with low arc force and less spatter. Welding work is performed using an arc.
On the other hand, when a large current is used to generate a re-arc, it is called a strong arc, and the strong arc force causes the molten metal to scatter, resulting in many spatters and a rough appearance of the weld bead. Therefore, the current situation is that people are avoiding it. Therefore, conventional DC arc welding machines have been designed to perform welding using a soft arc in order to reduce spatter.

``Problems that the invention attempts to solve'' However, welding using only soft arc as described above is often unable to meet the diverse demands of on-site work.

For example, short circuits between the welding rod and the base metal often occur during welding work, but with soft arc, the short circuit current is suppressed to the same value as the arc current as described above, so the short circuit part is scattered. The welding rod and base metal may be welded together, and the arc may be interrupted.

In particular, vertical welding is usually performed in a low current range, and the molten metal tends to stay in the protective cylinder formed at the arc end of the welding rod, and it also tends to enlarge, so it can be scattered. In the case of a soft arc, which does not have sufficient arc force, the above-mentioned problems occur more frequently.

``Problem to be solved by the invention'' Therefore, in view of the above circumstances, the present invention has developed an arc current that matches the welding conditions of the welding rod and base metal, that is, a soft arc. When the welding rod and base metal are short-circuited, such as when performing welding work and generating a re-arc,
A short circuit current with a value higher than the arc current generates an arc force sufficient to scatter the short circuit,
It is an object of the present invention to provide a DC arc welding machine that can effectively prevent the occurrence of welding between a welding rod and a base metal, arc breakage, etc.

"Means to be Solved by the Invention" In order to achieve the above object, the present invention includes a controlled rectifier for obtaining DC welding power from an AC power source, and detects the arc current output from the controlled rectifier. an arc current detection circuit, an arc current setting circuit that adjusts the level of the detected value by the arc current detection circuit to enable variable adjustment of the arc current value, and a reference value for comparing the output value of the arc current setting circuit with the reference value. and an ignition circuit for comparing the reference value of the reference voltage output circuit with the output value of the arc current setting circuit and controlling the phase of the control rectifier based on this comparison value. A DC arc welding machine comprising: a short-circuit current setting circuit for setting a current value higher than the arc current; and a short-circuit current setting circuit, and the switching circuit is installed between the output terminals of the control rectifier, and when a short-circuit condition is detected based on the voltage value between the output terminals, the switching circuit switches between the arc current setting circuit and the short-circuit current setting circuit. The present invention is characterized by a DC arc welding machine connected to a short circuit detection circuit for switching control from the circuit to a short circuit current setting circuit.

"Function" In the above means, the present invention provides that, during normal arc generation, the control rectifier is phase-controlled by the ignition circuit so as to output an arc current of a value preset by the arc current setting circuit; When the welding rod and the base metal are short-circuited, the short-circuit detection circuit detects this, switches the switching circuit to the short-circuit current setting circuit side, and outputs the short-circuit current of the value set by the short-circuit current setting circuit. The ignition circuit controls the phase of the controlled rectifier.

"Embodiment" An embodiment of the DC arc welding machine according to the present invention will be described below with reference to the drawings. FIG. 1 shows one embodiment of the present invention, and the same parts as those of the conventional DC arc welding machine shown in FIG. 4 will be described with the same reference numerals. A switching circuit 8 is inserted between the ignition circuit 3 and the arc current setting circuit 4. That is, the arc current setting circuit 4 is connected to one switching terminal a of the switching circuit 8,
A short circuit current setting circuit 7 is connected to the other switching terminal b of the switching circuit 8. The short circuit current setting circuit 7
As shown in the figure, the short circuit current can be freely set within the range from the same value _I1 as the arc current to the higher value _I2 . A short circuit detection circuit 6 is connected to the switching circuit 8. The short circuit detection circuit 6 is interposed between the welding output terminals 10, 10, and detects a short circuit such as contact between the welding rod and the base metal, and the output voltage between the welding output terminals 10, 10 is predetermined as shown in FIG. It is designed to perform a detection operation when the voltage drops below a certain value _V0 , and also includes a drive circuit for switching the switching circuit 8.

In the above configuration, during normal arc generation, the output voltage between the welding output terminals 10, 10 is equal to or higher than a certain value _V0 , and the short circuit is not detected in the short circuit detection circuit 6 and the switch is switched. The arc current setting circuit 4 is connected to the ignition circuit 3 via the switching circuit 8 so that the circuit 8 does not perform a switching operation. Therefore, as in the conventional case, the value of the arc current is detected by the arc current detection circuit 2, and the detection signal _V1 is level-adjusted in the range preset by the arc current setting circuit 4, that is, by the adjustment rate, and then the output is The value V ₂ is applied to the ignition circuit 3 via the switching circuit 8 and the ignition circuit 3
Now, the above output value V ₂ is compared with the reference voltage V ₃ output from the reference voltage output circuit 5, and based on the comparison result, the phase of the control rectifier 1 is controlled, and the welding rod and motherboard are output from the welding output terminals 10, 10. The arc current supplied to the material is maintained at the value set by the arc current setting circuit 4.

On the other hand, as shown in FIGS. 2 and 3, a short circuit occurs due to contact between the welding rod and the base metal, and as a result, the output voltage between the welding output terminals 10 and 10 decreases to a constant value V ₀
When the current drops to below, the short circuit detection circuit 6 detects this and switches the switching circuit 8, and switches the ignition circuit 3 so that the short circuit current setting circuit 7 is newly connected to the ignition circuit 3 via the switching circuit 8. Change. Therefore, the ignition circuit 3 receives the set value V ₂ ' from the short circuit current setting circuit 7 via the switching circuit 8, and controls the rectifier based on the comparison result between the set value V ₂ ' and the reference voltage V ₃ . 1 is phase-controlled so that the short-circuit current supplied from the welding output terminals 10, 10 between the welding rod and the base metal becomes the value set by the short-circuit current setting circuit 7. The short-circuit current setting circuit 7 freely sets the short-circuit current within the range from a value _I1 that is approximately the same as the arc current to a value _I2 that is higher than the arc current, depending on various welding conditions such as the material of the base material. If the short circuit between the welding rod and the base metal is scattered due to the short circuit current and a normal arc occurs again, the short circuit detection circuit 6 will no longer detect a short circuit.
The switching circuit 8 performs a return operation, and the output value V ₂ from the arc current setting circuit 4 is provided to the ignition circuit 3 as described above, and control rectification is performed based on the comparison result between the output value V ₂ and the reference voltage V ₃ . The phase of the device 1 is controlled, and the arc current set by the arc current setting circuit 4 is supplied to the welding rod and the base metal.

"Effects of the Invention" As described above, according to the DC arc welding machine of the present invention, during normal welding work during arc generation, the welding work can be performed using an arc current that matches the welding conditions of the welding rod, base metal, etc. When the welding rod and the base metal are short-circuited, such as when re-arcing, a short-circuit current higher than the arc current generates enough arc force to scatter the short-circuited part, and the welding rod and base metal It can effectively prevent welding with materials and arc breakage.

In addition, when the current when re-arcing is large, the molten pool of the base metal is pushed down due to the sudden expansion of the arc column, and therefore, compared to a soft arc, even at the same arc current value, the penetration is lower. It is convenient because the necessary penetration depth can be obtained even if the rod movement speed, that is, the speed of the welding operation is increased.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the DC arc welding machine according to the present invention, Fig. 2 is a waveform diagram of the output current versus time of the DC arc welding machine of Fig. 1, and Fig. 3 is a diagram of the output current of the DC arc welding machine of Fig. Figure 4 is a block diagram of a conventional DC arc welding machine, Figure 5 is an output waveform diagram of each circuit of the DC arc welding machine shown in Figure 4, and Figure 6 is a diagram of the output waveforms of each circuit of the DC arc welding machine. FIG. 3 is an external output characteristic diagram of the DC arc welding machine shown in FIG. DESCRIPTION OF SYMBOLS 1... Control rectifier, 2... Arc current detection circuit, 3... Ignition circuit, 4... Arc current setting circuit, 5... Reference voltage output circuit, 6... Short circuit detection circuit, 7... Short circuit current Setting circuit, 8...Switching circuit,
9...AC power supply, 10...Welding output terminal.

Claims (1)

[Scope of utility model registration request] A control rectifier for obtaining DC welding power from an AC power supply, an arc current detection circuit for detecting the arc current output from the control rectifier, and a variable adjustment of the arc current value by the arc current detection circuit. an arc current setting circuit that performs level adjustment, a reference voltage output circuit that outputs a reference value to compare the output value of the arc current setting circuit with a reference value, and a reference value and arc current setting of the reference voltage output circuit. A short circuit current setting for setting a current value higher than the arc current in a DC arc welding machine comprising an ignition circuit for comparing the output value of the circuit and controlling the phase of the control rectifier based on this comparison value. A switching circuit for switching between the arc current setting circuit and the short circuit current setting circuit is provided between the arc current setting circuit and short circuit current setting circuit and the ignition circuit, and the switching circuit includes a control circuit. A short circuit detection circuit is connected between the output terminals of the rectifier and is configured to switch from the arc current setting circuit to the short circuit current setting circuit when a short circuit condition is detected based on the voltage value between the output terminals. Characteristic DC arc welding machine.