JPS59166373A - Dc arc welding machine - Google Patents

Abstract

PURPOSE:To reduce generation of spatter and generate arc surely by providing a short-circuit detecting circuit and an arithmetic circuit and controlling welding current basing on differential voltage between set voltage and welding voltage. CONSTITUTION:In the case where welding current exceeds the set value when short-circuiting, welding current is controlled by a controlling circuit 34, and peak value is limited. During the period of arc generation, a Q output signal L is outputted from the short-circuit detecting circuit 38. At the same time, a current detecting signal H is outputted from a welding current detecting circuit 36, and a transistor 44 makes off operation and compensating voltage V2 is generated from a pre-amplifier 42. Accordingly, a pre-amplifier 20 adds compensating voltage V2 to set voltage Vs and compares with welding voltage Vf, and outputs large controlling voltage Vo to a driving circuit 30, and controlling voltage corresponding to the controlling voltage Vo is outputted to a controlling circuit 34. Accordingly, welding current is controlled by the controlling circuit 34 until welding current becomes below a specified value at the time of arc generation and decrease of current becomes gentle.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a DC arc welding machine, and more particularly to a DC arc welding machine that controls welding current based on a voltage difference between a set voltage and a welding voltage.

Conventionally, a welding machine as shown in FIG. 1 has been used as a DC arc welding machine for this glaze.

In FIG. 1, a wire electrode 10 wound around a reel is fed by a feeding device toward a workpiece 12 to be welded, and in order to generate an arc in the gap between the wire electrode 10 and the workpiece 12, a power supply circuit is provided. 14 are provided. Power supply circuit 14
is composed of a welding transformer, a rectifier, etc., and applies a DC voltage between the wire electrode lO and the object to be welded 12 via the contact tick 16. In this embodiment,
The wire electrode 10 is connected as a positive electrode, and the object to be welded 12 is connected as a negative electrode.

An arithmetic circuit 18 is provided to calculate a control voltage vo based on the voltage difference between the set voltage V8 and the welding voltage f.
4.26 and a capacitor 28. The preamplifier 20 of the arithmetic circuit 18 generates a control voltage v for controlling the welding current based on the voltage difference between the set voltage Vs and the welding voltage vf.

and calculate the control voltage V. is supplied to the drive circuit 30, and the control voltage V is supplied from the drive circuit 30. A voltage corresponding to the voltage is output. Note that the set voltage s can be adjusted by varying the resistance value of the variable resistor 32.

Further, a control circuit 34 is provided to control the welding current according to the control voltage level calculated by the arithmetic circuit 18, and this control circuit 34 has a configuration including a thyristor or a transistor 2, and The control circuit 34 controls the welding current in accordance with the control voltage level calculated by the calculation circuit 18 so that the voltage difference between the set voltage Vs and the welding voltage f is reduced.

FIG. 2 shows the control operation of the control circuit 34, in which the set voltage vs is set to a predetermined negative value, and the arc voltage (welding voltage) is configured to be a positive voltage.

Then, at time T, when the tip of the wire electrode comes into contact with the workpiece 12 and a short circuit occurs, the arc voltage rapidly decreases. The arithmetic circuit 18 calculates the set voltage ■s and the welding voltage ■f.
A control voltage that is larger than the control voltage at time T1 is calculated based on the voltage difference between the control voltage and the control voltage at time T1. However, this calculation is performed slowly due to the action of the capacitor 28. Therefore, the wire electrode 10 and the workpiece 12 are connected during the short circuit period ('P1~'r
During '3), the control voltage v0 continues to increase.

Then, the control circuit 34 controls the welding current to increase based on the control voltage Vo calculated by the calculation circuit 18. The wire electrode 10 is heated by resistance heat generation, and the tip portion is melted. Immediately before time T, a constriction occurs in the melted portion. Then, when time T3 is reached, the constriction of the molten part is separated, a gap is created between the tip of the wire electrode 10 and the workpiece 12, and an arc is generated in the gap.

The object to be welded 12 is melted by the generated arc, and the tip of the 4W wire pole 10 is melted by the generated arc, producing droplets as described above. Accordingly, the arc voltage becomes higher than that during the short circuit period. and,
The arithmetic circuit 18 determines the control voltage V based on the difference voltage between the set voltage vs and the welding voltage vf, which is higher than that during the short circuit period. Calculate.

In this case too, the control voltage ■. changes not suddenly but gradually due to the action of the capacitor 28. The control circuit 34 controls the welding current according to the calculated fljl control voltage vo. Then, when time T4 is reached, the enlarged droplets come into contact with the workpiece 12 to be welded, resulting in a short circuit again. Thereafter, desired welding is performed by alternately repeating the short-circuit state and the arc generation state as described above.

However, in conventional DC arc welding machines, the welding current is controlled so that an excessive welding current flows between time T and time T3 with a predetermined margin in order to generate an arc reliably. There is a drawback that when an arc occurs between the tip of the weld 10 and the workpiece 12, large grains of slitter may be generated due to the fuse action.

The present invention has been made in view of the above-mentioned conventional problems, and its object is to provide a DC arc welding machine that can extremely reduce the occurrence of spatter and can reliably generate an arc.

In order to achieve the above object, the present invention includes an arithmetic circuit that calculates a control voltage based on a voltage difference between a set voltage and a welding voltage;
A DC arc welding machine equipped with a control circuit that controls a welding current according to a calculated control voltage level, a welding current detection circuit that detects a welding current, a short circuit detection circuit that detects a short circuit state of an electrode, If the welding current exceeds the set value during a short circuit, a predetermined compensation voltage is added to the welding voltage to reduce the control voltage, and when an arc occurs, the welding current is adjusted to the set voltage so that it is below the predetermined value. and an arithmetic circuit that increases the control voltage by adding a compensation voltage to the control voltage.

Preferred embodiments of the present invention will be described below based on the drawings.

FIG. 3 shows a preferred embodiment of a DC arc welding machine according to the present invention, and in the figure, the same parts as those of the conventional example shown in FIG.

In FIG. 3, a welding current detection circuit 36 is provided to detect the welding current, and this welding current detection circuit 36 is composed of a Hall element, etc., and the current becomes "H" when the welding current exceeds a predetermined value. Outputs a detection signal. Further, a short circuit detection circuit 38 is provided to detect a short circuit state between the electrode, that is, the wire electrode 10 and the workpiece 12, and this short circuit detection circuit 38 outputs an "H" signal when the wire electrode 10 and the workpiece 12 are short-circuited. When an arc occurs, a Q output signal rLJ is output. Further, the direction output signal outputs a signal opposite to the Q output signal.

In this embodiment, the arithmetic circuit 40 includes a preamplifier 42, a transistor 4, in addition to the components shown in FIG.
4.46, has a resistor of 48 to 60, and if the welding current exceeds the set value during a short circuit, a predetermined compensation voltage V is added to the welding voltage Vf to control the voltage (■).

When an arc occurs, a predetermined compensation voltage v2 is added to the set voltage Vs until the welding current becomes less than a predetermined value to obtain a control voltage (■). That is, during the short-circuit period, the short-circuit detection circuit 38 outputs a hundred output signal rLJ, and the transistor 46 is turned off. At this time, when the welding current increases and a current detection signal rHJ is output from the welding current detection circuit 36, the transistor 46 is in the OFF state, so the collector terminal of the transistor 46 has the signal shown in FIG. A compensation voltage (1) having the same polarity as the welding voltage is generated. Therefore, the preamplifier 20 adds the compensation voltage V to the welding voltage ■f and compares this with the set voltage ■S, and as a result, the preamplifier 20 sends the set voltage ■s and the welding voltage V to the drive circuit 30.
The control voltage ■ has a smaller value than when comparing f. is calculated and output, and a nine control voltage m corresponding to the control voltage v0 is output from the drive circuit 30 to the control circuit 34. Therefore, when the welding current exceeds the set value during a short circuit, that is, in the period from time 'I'll to time T1□- in FIG. Compared to the conventional 11, the B
Values are quite limited.

Furthermore, during the arc generation period, when the short circuit detection circuit 38 outputs a Q output signal of "L" and at the same time the welding current detection circuit 36 outputs a current detection signal of rHJ, the transistor 44 turns off. And this result,
The preamplifier 42 generates a compensation voltage v2 having the same polarity as the set voltage ■s.

Therefore, the preamplifier 2o applies a compensation voltage v2 to the set voltage vs.
is added and compared with the welding voltage ■f, and as a result, Sirian 7
From a20 to the drive circuit 3o, the set voltage ■s and the welding voltage V
The control voltage V is larger than when compared with f. is output, and the control voltage V is output from the drive circuit 3o to the control circuit 34.

A control voltage corresponding to the output voltage is output. Therefore, the welding current is controlled by the control circuit 34 until the welding current becomes less than a predetermined value when an arc occurs, that is, from time TI2 to time T13 in FIG. 4, and the set voltage ■s and welding ■f are compared. If (indicated by the two-dot chain line -
The welding current decreases more slowly than in case 1).

As described above, in this embodiment, since the peak value of the welding current is limited, it is possible to extremely reduce the occurrence of spatter as shown in the conventional example. Furthermore, in this embodiment, since the arc-generating welding current is controlled to gradually decrease, sufficient energy is supplied to melt the wire electrode 10 by a predetermined amount, and as a result, the wire electrode lO An arc having a predetermined length can be reliably generated in the gap between the entire surface of the tip and the workpiece 12.

As explained above, according to the present invention, the welding current detection circuit detects the welding current, the short circuit detection circuit detects the short circuit state of the electrode, and the welding voltage and a calculation circuit that calculates a decrease in the control voltage by adding a predetermined compensation voltage to the set voltage and increases the control voltage by adding a predetermined compensation voltage to the set voltage until the welding current becomes less than a predetermined value when an arc occurs. By doing so, it is possible to suppress the peak value of the welding current to extremely reduce the occurrence of spatter, and it is also possible to reduce the welding current slowly to ensure the generation of an arc.

[Brief explanation of drawings]

FIG. 1 is a waveform diagram showing the control state of welding current in an example of a conventional DC arc welding machine, FIG. 3 is a circuit configuration diagram showing a preferred embodiment of the DC arc welding machine according to the present invention, and FIG.
This figure is a waveform diagram showing the control state of the welding current in the circuit shown in FIG. 3. The same parts in each figure are given the same reference numerals, and 10 is a wire electrode, 12 is a workpiece to be welded, 34 is a control circuit, 36 is a welding current detection circuit, 38 is a short circuit detection circuit, and 40 is an arithmetic circuit. Agent Patent attorney Shin Kuzuno - (1 other person) Procedural amendment (spontaneous) Commissioner of the Japan Patent Office 1, Indication of case Patent application No. 58-41813 2
, Name of invention DC arc welding machine 3, Person making the amendment 5, Drawing subject to amendment.

Claims (1)

[Claims] (1) In a DC arc welding machine equipped with a calculation circuit that calculates a control voltage based on a voltage difference between a set voltage and a welding voltage, and a control circuit that controls a welding current according to the calculated control voltage level, a welding current detection circuit that detects the current; a short circuit detection circuit that detects the short circuit state of the electrode;
If the welding current exceeds the set value during a short circuit, a predetermined compensation voltage is added to the welding voltage to reduce the control voltage, and when an arc occurs, the welding current is adjusted to the set voltage so that it is below the predetermined value. A direct welding machine characterized by comprising: an arithmetic circuit that increases and calculates a control voltage by adding a compensation voltage to the control voltage.