JP2543270B2 - Arc welding machine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arc welding machine used for welding materials such as aluminum and magnesium that require oxide film removal.

[0002]

2. Description of the Related Art Conventionally, an AC arc welder has been used for welding materials such as aluminum and magnesium that require removal of an oxide film at the time of welding. FIG. 3 shows an example of the circuit configuration of a conventional AC arc welder.

In FIG. 3, 1 is a commercial power source, 2 and 5 are rectifying diodes, 3 is a switching element, 4 is a welding transformer, 6a and 6b are capacitors, 7 is a workpiece, 8 is an arc load, 9 is an electrode, 10a and 10b are switching elements, 11a is a drive signal circuit A for driving the switching element 10a, 11b is a drive signal circuit B for driving the switching element 10b, and 12 is a drive signal circuit A1.
An oscillating circuit that determines the pulse periods of 1a and the drive signal circuit B11b, and 13 is an inverter.

In the circuit shown in FIG. 3, the commercial power source 1 is rectified by a rectifying diode 2, the rectified output is switched by a switching element 3, the AC output is stepped down by a welding transformer 4, and two output terminals are provided. Series circuit of capacitors 6a and 6b and two switching elements 10a and 10
b series circuits are connected to each other, and two capacitors 6a
And 6b connection point and two switching elements 10a and 10
Welding load between the connection points of b, that is, the workpiece (base metal)
7, the electrode 9 and the arc 8 are connected to each other, and one of the two switching elements 10a and 10b is connected to the switching element 10a.
Is connected to the drive signal circuit A11a, the other switching element 10b is connected to the drive signal circuit B11b, and the drive signal circuit A11a is connected to the oscillator circuit 12
Is directly connected to the drive signal circuit B11b with the polarity of the output of the oscillation circuit 12 inverted by the inversion circuit 13.

A pulse output synchronized with the output waveform of the oscillation circuit 12 is output from the drive signal circuit A11a, and the switching element 10a is repeatedly turned on and off. On the other hand, since the output of the oscillation circuit 12 is inverted and input to the drive signal circuit B11b by the inverter 13, the drive signal circuit B11b turns the switching element 10b on and off alternately with the switching element 10a.

By this operation, when the switching element 10a is turned on and the switching element 10b is turned off,
Current is switching element 10a → electrode 9 → arc load 8
→ Welding object 7 → Flowing in the course of capacitor 6b, conversely switching element 10a is OFF and switching element 10b
When is ON, the current is from capacitor 6a to workpiece 7
→ Arc load 8 → Electrode 9 → Switching element 10b. Therefore, the alternating current shown in FIG. 4 flows through the arc load 8.

During the period in which a positive current is flowing through the arc load 8 on the electrode 9 side, it has the effect of removing the oxide film having a higher melting point than the base metal of the workpiece 7, and during the period in which the electrode 9 side is negative, Since it has a strong effect of melting the workpiece 7,
This kind of AC arc welding machine was used for welding aluminum and magnesium.

[0008]

However, in the AC arc welding machine described above, when aluminum material or magnesium material is welded, the directivity of the arc is poor, so that (1) fillet welding is difficult (2) It has drawbacks such as difficulty in back-side welding, and it is a harmonic when the polarity is reversed. (3) Arc noise is high. Furthermore, due to the electrode heating effect when the current on the electrode side + flows, (4) Electrode wear is fast. There were problems such as.

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned conventional problems, and increases fillet welding and backside welding by increasing arc directivity and stability and reducing the electrode heating effect. The purpose of this is to make it easy and at the same time suppress the consumption of electrodes and further reduce the arc noise.

[0010]

In order to achieve the above object, the arc welding machine of the present invention has a rectifier circuit connected to the secondary side of a welding transformer and has two capacitors connected in series at its output end. A connection circuit and a series connection circuit of two switching elements are respectively connected, and a welding load is connected between the midpoint of the series connection of the two capacitors and the midpoint of the series connection of the two switching elements, A drive signal circuit A that drives one of the two switching elements, and a drive signal circuit B that outputs an inverted signal of the drive signal circuit A and drives the other switching element.
An oscillator circuit that determines the pulse period of the two drive signal circuits A and B, and a timer circuit that inputs a signal for the oscillator circuit to repeat oscillation and stop operation at a constant period to the oscillator circuit It was done.

[0011]

With the above structure, the negative AC current on the electrode side is periodically mixed with the conventional AC current,
The negative DC characteristic on the electrode side is added to the AC characteristic. As a result, the electrode becomes a hot cathode during the minus side of the electrode side, and the pole point is stabilized, so that the directivity of the arc is increased, the arc is stabilized, and there is no electrode heating effect as in the case of the plus side of the electrode, resulting in electrode wear. Suppressed. In addition, since there is no polarity reversal during DC mixing, noise due to harmonics is eliminated and arc noise is reduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the AC arc welding machine of the present invention will be described below with reference to the drawings.

In FIG. 1, the main circuit configuration is the same as that of the conventional example shown in FIG. 3, so the primary side of the welding transformer 4 is omitted. Also, with respect to other portions, the same portions as those in FIG. 3 are denoted by the same reference numerals, and different portions will be described. In FIG. 1, 14 is a timer circuit, and 15 is a pulse width adjusting circuit.

In the circuit shown in FIG. 1, the timer circuit 1
Oscillation circuit 1 when 4 repeats ON and OFF in a constant cycle
When the timer circuit 14 is turned on, the oscillation circuit 12 oscillates, and when the timer circuit 14 is turned off, the oscillation circuit 12 stops oscillating, and the timer circuit 14 and the oscillation circuit 1
2 repeats this operation. When the timer circuit 14 is ON, the switching elements 10a and 10
Since the drive circuit A11a and the drive circuit B11b output a signal for alternately turning on and off b based on the signal from the oscillation circuit 12, an alternating current flows during the period of T _AC as shown in FIG. On the other hand, the timer circuit 14 is OF
In the case of F, the oscillation circuit 12 stops the oscillation, but the switching element 10a is turned on and the switching element 10b is turned on.
Is kept off, the current flows from the capacitor 6a to the workpiece 7 to the arc load 8 to the electrode 9 to the switching element 10b.
2 and a negative DC current on the electrode side flows during the period T _DC as shown in FIG.

In this way, the ON / OF of the timer circuit 14 is
A mixed current in which alternating current and direct current flow alternately according to F can be easily obtained. Therefore, the timer circuit 1
Depending on the time limit setting of 4, the DC current period ratio = T _OFF / (T
_ON + T _OFF ) = T _DC / (T _AC + T _DC ) can be freely selected.

Even when the DC current period ratio is fixed, if the pulse width adjusting circuit 15 narrows the pulse width during the oscillating operation of the oscillating circuit 12, the pulse width of the drive signal circuit A11a becomes narrow and the drive signal circuit B11 becomes narrow.
Since the pulse width of b becomes wider and the conduction period of the switching element 10b becomes wider and the ratio of the negative current on the electrode side increases accordingly, the same effect as increasing the DC current period ratio is obtained, and the hot cathode discharge The period ratio increases, the directivity and stability of the arc increase, the electrode heating effect decreases, and electrode consumption is suppressed.

[0017]

As is apparent from the above description, according to the present invention, the alternating current period and the negative direct current period on the electrode side are alternately repeated periodically to increase the ratio of the direct current period to perform arc welding. By doing so, the period ratio of hot cathode discharge increases, and the poles stabilize during this period, so the directivity and stability of the arc increase, facilitating fillet welding and backside welding of aluminum, magnesium, etc. The electrode heating effect generated in the case of side plus is reduced to suppress the electrode consumption. Furthermore, by providing a direct current period,
The generation of higher harmonics at the time of polarity reversal is reduced, which also has the effect of reducing arc noise.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of an arc welding machine of the present invention.

FIG. 2 is a waveform diagram of output current in the same example.

FIG. 3 is a circuit configuration diagram in a conventional example.

FIG. 4 is a waveform diagram of output current in a conventional example.

[Explanation of symbols]

 4 Welding transformer 5 Rectifier diode (rectifier circuit) 6a, 6b Capacitor 7 Welding object 8 Arc load 9 Electrodes 10a, 10b Switching element 11a Drive signal circuit A 11b Drive signal circuit B 12 Oscillation circuit 14 Timer circuit 15 Pulse width adjustment circuit

Claims (2)

(57) [Claims] 1. A rectifier circuit is connected to the secondary side of a welding transformer, and a series circuit of two capacitors and a series circuit of two switching elements are connected to the output terminals of the rectifier circuit, respectively, and two capacitors are connected in series. Drive signal circuit A for driving one switching element of the two switching elements by connecting a welding load between the middle point and the middle point of the series connection of two switching elements, and the drive signal circuit A
Drive signal circuit B for outputting the inversion signal of the other drive circuit and driving the other switching element, an oscillation circuit for determining the pulse period of the two drive signal circuits A and B, and the oscillation circuit oscillates and stops at a constant period. An arc welding machine equipped with a timer circuit that inputs a signal for repeating the above to the oscillation circuit. 2. The arc welding machine according to claim 1, further comprising a pulse width adjusting circuit for the oscillation circuit.