JPH04361873A - Arc welding machine - Google Patents

Abstract

PURPOSE:To suppress consumption of an electrode and further to reduce an arc sound by providing a welding machine used for welding materials such as aluminum and magnesium requiring to remove an oxide film at the time of performing welding with a characteristic suited for fillet welding and penetration welding. CONSTITUTION:This arc welding machine is provided with a drive circuit 11a where a rectifier circuit 5 is connected to the secondary side of a welding transformer 4, a series circuit of two capacitors 6a and 6b and a series circuit of two switching elements 10a and 10b are connected respectively to the output ends thereof, welding loads (materials 7 to be welded, arc load 6 and the electrode 9) are connected between intermediate points of the respective series circuits, and the switching element 10a is driven, a drive circuit 11b to output an inversion signal of the drive circuit 11a and drive the switching element 10b, an oscillation circuit 12 to determine pulse periods of the drive circuit A11a and the drive circuit B11b and a timer circuit 14 to allow the oscillation circuit 12 to repeat oscillation and stopping operation at a specified period.

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 removal of oxide films.

0002

2. Description of the Related Art Conventionally, AC arc welding machines have been used to weld materials such as aluminum and magnesium that require removal of oxide films during welding. FIG. 3 shows an example of the circuit configuration of a conventional AC arc welding machine.

In FIG. 3, 1 is a commercial power source, 2 and 5 are rectifier diodes, 3 is a switching element, 4 is a welding transformer, 6a and 6b are capacitors, 7 is an object to be welded, 8 is an arc load, 9 is an electrode, 10a and 10b are switching elements, 11a is a drive signal circuit A that drives the switching element 10a, 11b is a drive signal circuit B that drives the switching element 10b, and 12 is a drive signal circuit A11.
13 is an inverter.

In the circuit shown in FIG. 3, a commercial power source 1 is rectified by a rectifier diode 2, the rectified output is switched by a switching element 3, the AC output is step-down isolated by a welding transformer 4, and two transformers are connected to the output terminal. A series circuit of capacitors 6a and 6b and two switching elements 10a and 10
b are connected in series, and two capacitors 6a are connected.
and 6b and the two switching elements 10a and 10
The welding load, i.e. the workpiece (base metal), is applied between the connection points of b.
7, electrode 9, and arc 8, one switching element 10a of the two switching elements 10a and 10b
The drive signal circuit A11a is connected to the other switching element 10b, and the drive signal circuit B11b is connected to the other switching element 10b.The output pulse of the oscillation circuit 12 is directly connected to the drive signal circuit A11a, and the output pulse of the oscillation circuit 12 is directly connected to the drive signal circuit B11b. The output is connected with its polarity inverted by an inverting 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 by the inverter 13 and input to the drive signal circuit B11b, the drive signal circuit B11b turns on and off the switching element 10b alternately with the switching element 10a.

[0006] When the switching element 10a is turned on by this operation and the switching element 10b is turned off,
Current flows from switching element 10a → electrode 9 → arc load 8
→ Workpiece 7 → Condenser 6b flows, and conversely, when switching element 10a is OFF, switching element 10b
is ON, the current flows from capacitor 6a to workpiece 7
→ Arc load 8 → electrode 9 → switching element 10b. Therefore, an alternating current shown in FIG. 4 flows through the arc load 8.

[0007] During the period when a positive current is flowing through the arc load 8 on the electrode 9 side, there is an effect of removing the oxide film having a higher melting point than the base metal of the workpiece 7, and during the period when the electrode 9 side is negative, Because it has a strong effect of melting the object 7 to be welded,
This type of AC arc welding machine was used to weld aluminum, magnesium, etc.

[0008]

[Problems to be Solved by the Invention] However, with the above-mentioned AC arc welding machine, when welding aluminum or magnesium materials, the directionality of the arc is poor, so (1)
Difficult to perform fillet welding (2) Difficult to perform uranami welding (3)
) In addition, there were problems such as high arc noise and (4) rapid electrode wear due to the electrode heating effect when current flows on the electrode side.

The present invention seeks to solve the above-mentioned conventional problems by increasing the arc directivity and stability, and reducing the electrode heating effect to perform fillet welding and back wave welding. The purpose is to make it easier to use, suppress electrode wear, and further reduce arc noise.

0010

[Means for Solving the Problems] In order to achieve the above object, the arc welding machine of the present invention connects a rectifier circuit to the secondary side of a welding transformer, and connects two capacitors in series to the output end of the rectifier circuit. connecting the connection circuit and a series connection circuit of two switching elements, and connecting a welding load 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; a drive signal circuit B that outputs an inverted signal of the drive signal circuit A and drives the other switching element;
The configuration includes an oscillation circuit that determines the pulse period of the two drive signal circuits A and B, and a timer circuit that inputs a signal to the oscillation circuit so that the oscillation circuit repeats oscillation and stop operations at a constant period. This is what I did.

[0011]

[Operation] With the above configuration, negative DC current on the electrode side is periodically mixed with the conventional AC current,
A negative DC characteristic on the electrode side is added to the AC characteristic. As a result, during the period when the electrode side is negative, the electrode becomes a hot cathode and the pole point is stabilized, increasing the directionality of the arc and stabilizing the arc.There is also no electrode heating effect as in the case of the electrode side positive, and electrode wear is reduced. suppressed. Furthermore, since there is no polarity reversal during direct current mixing, there is no noise due to harmonics, and arc noise is reduced.

0012

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 in FIG. 3 showing the conventional example, so the primary side of the welding transformer 4 is omitted. Also, regarding other parts, the same parts as in FIG. 3 are given the same reference numerals, and different parts will be explained. In FIG. 1, 14 is a timer circuit, and 15 is a pulse width adjustment circuit.

In the circuit shown in FIG.
When 4 repeats ON and OFF at a constant cycle, oscillation circuit 1
2 are interlocked, so that when the timer circuit 14 is ON, the oscillation circuit 12 oscillates, and when the timer circuit 14 is 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 on and off based on the signal from the oscillation circuit 12, an alternating current flows during the TAC period as shown in FIG. On the other hand, the timer circuit 14 is turned off.
In the case of F, the oscillation circuit 12 stops oscillating, but the switching element 10a is turned on, and the switching element 10b is turned on.
continues to be OFF, the current flows from capacitor 6a → workpiece 7 → arc load 8 → electrode 9 → switching element 10b
As shown in FIG. 2, a negative DC current flows on the electrode side during the TDC period.

In this way, the ON/OFF of the timer circuit 14 is
According to F, a mixed current in which alternating current and direct current flow alternately can be easily obtained. Therefore, timer circuit 1
Depending on the time limit setting in step 4, the DC current period ratio = TOFF/(
TON+TOFF)=TDC/(TAC+TDC) can be freely selected.

Further, even when the DC current period ratio is fixed, if the pulse width during the oscillation operation of the oscillation circuit 12 is narrowed by the pulse width adjustment circuit 15, the pulse width of the drive signal circuit A11a becomes narrower, and the pulse width of the drive signal circuit B11 becomes narrower.
The pulse width of b becomes wider, and accordingly, the conduction period of the switching element 10b expands and the ratio of negative current on the electrode side increases, so the same effect as increasing the DC current period ratio is obtained, and the hot cathode discharge The period ratio increases, the directionality and stability of the arc increases, and the electrode heating effect decreases, suppressing electrode wear.

[0017]

Effects of the Invention As is clear from the above description, according to the present invention, the alternating current period and the electrode-side negative direct current period are alternately repeated periodically, and the ratio of the direct current period is increased to perform arc welding. By doing this, the period ratio of hot cathode discharge increases, and the pole point becomes stable during this period, which increases the directionality and stability of the arc, making fillet welding and back wave welding of aluminum, magnesium, etc. easier, and electrode Reduces the electrode heating effect that occurs in the case of positive side and suppresses electrode wear. Furthermore, by providing a DC current period,
There is less harmonic generation during polarity reversal, which also has the effect of reducing arc noise.

[Brief explanation of drawings]

[Fig. 1] A circuit configuration diagram showing an embodiment of an arc welding machine of the present invention.

[Figure 2] Waveform diagram of output current in the same example

[Figure 3] Circuit configuration diagram in conventional example

[Figure 4] Waveform diagram of output current in conventional example

[Explanation of symbols]

4 Welding transformer 5 Rectifier diode (rectifier circuit) 6a, 6b capacitor 7 Object to be welded 8 Arc load 9 Electrode 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)

[Claims] Claim 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 respectively connected to the output terminal of the rectifier circuit, and the two capacitors are connected in series. A drive signal circuit A that connects a welding load between a midpoint and a midpoint of a series connection of two switching elements and drives one of the two switching elements, and the drive signal circuit. a drive signal circuit B that outputs an inverted signal of A and drives the other switching element, and the two drive signal circuits A,
An arc welding machine equipped with an oscillation circuit that determines the pulse period of B, and a timer circuit that inputs a signal to the oscillation circuit so that the oscillation circuit repeats oscillation and stop operations at a constant period. 2. The arc welding machine according to claim 1, further comprising a pulse width adjustment circuit for the oscillation circuit.