JPS58159977A - Dc arc welding machine - Google Patents

Abstract

PURPOSE:To obtain a titled welding machine that reduces generation of sputter and eliminates influences from outside, by making the wire feeding speed nearly constant and controlling by feeding back the output current when the wire is short-circuited and controlling by feeding back the output voltage when an arc is generated. CONSTITUTION:In a DC are welding machine that performs welding by Joule heat at the time of short-circuiting between the wire and base metal and arc heat at the time of opening, the output of a rectifier circuit 1 is supplied to a welding load 3 through an output regulator 2. Short-circuit arc discrimination circuits 6, 7 are provided in the circuit, and short-circuiting between the wire and base metal is detected by inputting signals of an output current proportion signal generator 4, an output voltage proportion signal generator 5 etc. This is compared with a reference signal by a comparator circuit 8, and an adjusting signal is sent to the output regulator 2 through a drive circuit 11. By this way, generation of sputter is prevented by suppressing change of output power when the wire is short-circuited, and voltage is kept constant by eliminating change of arc voltage due to external influences at the time of opening.

Description

Detailed Description of the Invention The present invention uses Joule heat when a welding wire (hereinafter simply referred to as a wire) as a consumable electrode and the base metal is short-circuited, and arc heat when the wire short-circuits are opened to connect the wire and the base metal. This relates to a DC arc welding machine that performs welding while melting.

There is a strong demand for this type of DC arc welding machine to reduce vines.

It is well known that the cause of this spatter is a short circuit when the output is shorted. Therefore, in order to reduce spatter, the peak current should be reduced as shown by the dotted lines in Figure 1 a and b. Methods of suppressing the growth of the short-circuit current, as shown in Figure 2 (a) and (l), are being considered.

However, in the case of such a conventional method, a problem arises in that the heat input to the wire during a short circuit is reduced, making it difficult to regenerate the arc.

Therefore, it is conceivable to increase the arc voltage to input heat into the wire during the arc so that arc regeneration can be easily performed. In fact, when the arc voltage is increased, even if the short circuit current is suppressed, arc regeneration becomes easier and spatter generation is significantly reduced.

In addition, as a means of performing such control, there is limiter control that uses power transistors to keep the short-circuit current constant. In this case, output waveforms as shown in Figure 2 a and b are obtained. For example, at an output current of 20 OA, Compared to the conventional method and fully automatic welding, the amount of spatter generated was approximately 1/4.

However, in the case of this method, the output voltage of the welding machine using the conventional method is 24V, but the output voltage is 3 parts - 25 V, which is 4 parts, and therefore the number of short circuits between the wire and the base metal is small, and the external It becomes very susceptible to the influence of conditions.

This is because the arc voltage changes due to the welding posture, the shape of the workpiece, changes in wire protrusion length due to hand shake during semi-automatic welding, and changes in wire feed. Therefore, in the case of a method of increasing the arc voltage, it is necessary to always keep the arc voltage constant in order to eliminate the influence of disturbances.

The present invention was made in view of the current situation, and aims to reduce the occurrence of spatter and eliminate the influence of external conditions.

In order to achieve this objective, the present invention is configured to keep the wire feeding speed substantially constant, perform feedback control of the output current when the wire is short-circuited, and perform feedback control of the output voltage when an arc occurs. This is what I did.

Hereinafter, an embodiment of the present invention will be explained using the drawing of FIG. 3.

In Fig. 3, 1 is a rectifier circuit, and the output of this rectifier circuit 1 is adjusted by a power transistor (JP-A-58-1).
59977 (supplied to the welding load 3 via the 2-volt regulator 2.

4 is an output current proportional signal generator that generates a signal proportional to the output current supplied from the output regulator 2 to the welding load 3; 5 is also proportional to the output voltage supplied from the output regulator 2 to the welding load 3; 6 and 7 are short circuit arc discrimination circuits that detect short circuits of the wire to the base metal based on the welding output. It uses a responsive analog switch.

Reference numeral 8 denotes a comparator circuit, which, when a wire is short-circuited, receives a short-circuit current reference signal from the short-circuit current reference signal generator 9 and a signal proportional to the actual short-circuit current from the output current proportional signal generator 4. Also, when an arc occurs, the arc voltage reference signal from the arc voltage reference signal generator 10 and the signal proportional to the actual output voltage from the output voltage proportional signal generator 5 are compared.・
11 is a drive circuit that controls the output regulator 2 using the output signal from the comparison circuit 8, and adjusts the output according to the signal from the comparison circuit 8 so that the output current and output voltage are always the same as the reference signal. control device 2.

Here, the reference signals in the short circuit current reference signal generator 9 and the arc voltage reference signal generator 1o are as shown in FIG.
This is a signal with a waveform as shown in the dotted line in b or as shown in FIGS. 2a and b.

That is, according to the present invention, when a wire is short-circuited, changes in the output current due to variations in contact resistance between the wire and the base metal are suppressed, and the generation of spatter is constantly reduced by a current (1.5 times or less of the arc current). In addition, when an arc occurs, the arc voltage is always kept constant by eliminating the influence of changes in arc pressure due to changes in wire protrusion length, base metal shape, welding posture, etc. be able to.

As described above, according to the DC arc welding machine of the present invention, a weld bead with less spatter can be obtained without being affected by external conditions.

[Brief explanation of drawings]

Figures 1a and 1b are waveform diagrams showing the output voltage and output current in a conventional DC arc welding machine, and Figure 2a is a waveform diagram showing the output voltage and output current of a conventional DC arc welding machine. b is a waveform diagram showing output voltage and output current in another conventional DC arc welding machine, and FIG. 3 is a block circuit diagram of a DC arc welding machine according to an embodiment of the present invention. 1... Rectifier circuit, 2... Output regulator,
3... Welding load, 4... Output current proportional signal generator, 5... Output voltage proportional signal generator,
6, 7... Short circuit arc discrimination circuit, 8...
・Comparison circuit, 9...- Short circuit current reference signal generator,
10... Arc voltage reference signal generator, 11...
...Drive circuit.

Claims (1)

[Claims] A DC arc welding machine equipped with a short-circuit arc discrimination circuit that detects short-circuits of welding wire to the base metal, and configured to perform feedback control of output current when a wire short-circuits, and perform feedback control of output voltage when an arc occurs. .