JPH01321077A - Pulse arc welding power source - Google Patents

Abstract

PURPOSE:To improve a welding characteristic in a low current region by providing a constant current pulse power source circuit and a constant voltage power source circuit and changing over the power source circuits automatically based on a size comparison of the rotating speed of a wire feed motor with the set speed. CONSTITUTION:A changeover point setter 12 capable of setting a value in proportion to the wire feed quality is provided and a motor speed setter 1 is arranged to a motor driving circuit 2. The changeover point setter 12 outputs a changeover point set signal Vref to a signal generator 13 and the motor speed setter 1 inputs a motor speed set signal Vm to the signal generator 13. A changeover circuit 11 then compares two signals and outputs a pulse current or a current of the constant voltage power source circuit 10 to an outside arc 8 according to its compared result. Since a pulse power source and the constant voltage current are selected automatically to perform welding, the occurrence of welding spatters in the low current region is suppressed and the welding characteristic is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (A field of application) This invention is applicable to inert gases such as argon, oxygen,
This invention relates to a welding power source used for gas-shielded pulse arc welding using a consumable electrode (hereinafter referred to as a wire) in a gas mixture of carbon dioxide or the like with an inert gas.

(Prior art) Generally, in this type of welding method, the phenomenon in which the welding wire melts and transfers to the base metal changes discontinuously after reaching the critical current value. In order to stably perform spray transfer welding of base metals, a method is generally adopted in which a pulsed current is superimposed on a direct current.

In other words, by setting the base current below the critical current value and the pulse current above the critical current value, droplet transfer becomes spray transfer, and the average current is kept low to reduce the amount of heat input to the base material, making it relatively This makes it possible to perform good welding even with thin base metals.

FIG. 2 shows a conventional pulse arc welding power source of this type, in which (1) is a wire feed motor, (4) is a motor speed setting device that outputs a setting signal to set the speed;
(2) is a motor drive circuit that rotates the wire feeding motor (4) at a desired speed based on the setting signal from this motor speed setting device (1), and (3) is a DC power after insulating the manually applied AC power. A constant current pulse power supply circuit that converts into electric power and generates the aforementioned pulse current (pulsed current superimposed on the base DC current), in order to supply the above pulsed current to the arc (8) as welding output. Power supply chip (
7). (5) is a wire fed out by a drive roller (6) driven by the wire feed motor (4), and is passed through the power feeding tip (7) to the workpiece.
(9) and generates an arc (8) between it and the workpiece (9) to perform welding.

A conventional pulsed arc welding power source is configured as described above.
The constant current pulse power supply circuit (3) converts the input AC power into DC power after insulating it, and generates a pulse in which a pulse current is superimposed on a base DC current. This pulse is then used as welding output to pass through the power supply tip (7) to the arc (8).
).

On the other hand, the setting signal set by the motor speed setting device (1) is manually input to the motor drive circuit (2), and this motor drive circuit (2) rotates the wire feed motor (4) at a desired speed. supplies electricity. This wire feed motor (4) is connected to a drive roller (6), and the rotation of the drive roller (6) feeds the wire (5) toward the workpiece (9) through the power supply tip (7). be done. This wire (5) receives welding output from the power supply tip (7) and arcs (
8) is generated and welding is performed.

[Problem to be solved by the invention]

With the conventional pulsed arc welding power source as mentioned above, the wire feed amount (in consumable electrode type arc welding, it is the average current value)
Since it is configured so that there is a roughly proportional relationship between
It is possible to weld with almost no spatter and a good weld bead, but in the low current region (average current value of about 120 to 13
In welding (in the region of 0 A or less), the pulse frequency is too low, so there are problems such as arc breakage occurring during the base current period, and even if arc breakage does not occur, the shape of the bead becomes uneven.

Therefore, some methods have been adopted to solve the above problem by allowing pulse arc welding in the medium to high current range and short arc welding in the low current range, and FIG. 3 shows an example of this method. In the figure, (lO) is a constant voltage power supply circuit, and (11) is a switching means composed of, for example, a switch. That is, in this example, the welding output supplied to the arc (8) by the switching means (11) is determined to be the output of the constant current pulse power supply circuit (3) or the output of the constant voltage power supply circuit (10). can be selected arbitrarily. Therefore, for example, a welding operator can select the constant voltage power supply circuit (3) in a low current region and perform short arc welding. In the low current range, the generation of spatter, which is considered a drawback of short arc welding, is not a big problem.In fact, the high number of short circuits is an advantage compared to pulsed arc welding in this range, resulting in a uniform weld bead. is obtained.

However, in the example shown in Fig. 3, in order to select the desired welding method, the switching means (11) must be manually operated each time, resulting in poor workability and difficulty in determining the optimal switching time. The problem is that it is not easy.

The present invention has been made to solve these problems, and provides a pulsed arc welding power source that can eliminate the drawbacks of conventional pulsed arc welding in the low current range and does not impair workability. With the goal.

[Means to solve the problem]

The pulse arc welding power source according to the present invention is a power source for consumable electrode type pulse arc welding that supplies a consumable electrode to a workpiece and generates an arc between the workpiece and the workpiece to perform welding.
A motor speed setting device that sets the speed of the wire feeding motor that feeds the consumable electrode, a motor drive circuit that drives the wire feeding motor at a desired speed based on the signal from the motor speed setting device, and a constant current pulse. A power supply circuit, a constant voltage power supply circuit, a switching point setting device that sets the switching point, and the magnitude of the signal from this switching point setting device and the signal from the motor speed setting device are compared, and a switching signal is set based on the result. The present invention is provided with a signal generator for outputting an output, and a switching circuit for selectively switching between the constant current pulse power supply circuit and the constant voltage power supply circuit based on a switching signal from the signal generator.

[Effect]

In this invention, the switching circuit selectively switches between the constant current pulse power supply circuit and the constant voltage power supply circuit based on the switching signal from the signal generator. Then, in the low current region, a constant voltage power supply circuit is selected and short arc welding is performed.
It becomes possible to improve weldability in the low current range, which was a drawback of conventional pulsed arc welding power sources. Moreover, since the selection of each power supply circuit is automatically performed, there is no loss in work efficiency.

〔Example〕

FIG. 1 shows an embodiment of the present invention.
The same reference numerals as those in the figures and FIG. 3 indicate the same or corresponding parts.

Reference numeral (12) denotes a switching point setting device that outputs a switching point setting signal Vref, and is capable of continuously variably setting a value proportional to the wire feed rate as the switching point setting signal Vref. (13) is the switching point setting signal V ref and the motor speed setting signal ■ from the motor speed setting device (1). A signal generator that compares the magnitude relationship with and outputs the result.
The switching circuit (11) automatically switches between the constant current pulse power supply circuit (3) and the constant voltage power supply circuit (10) based on the signal from the signal generator (13).
). Also, the above signal generator (
13) has hysteresis within a certain range when comparing both signals V raf and V IB.

In the pulsed arc welding power source configured as described above, the switching point setter (12) sends switching point setting signals (1) to the signal generator (13). Output f.

The signal generator (13) also includes a motor speed setting device (1).
The motor speed setting signal ■□ from is input.

The input stage of the signal generator (13) is composed of, for example, two human-powered comparators, and the two signals V raf
%V II, and outputs an "H" signal when, for example, vr, f>V, Il, and outputs an "L" signal when Vrsr≦vlIl. The switching circuit (11)
By inputting the "H" signal or the "L" signal, either the output of the constant current pulse power supply circuit (3) or the output of the constant voltage power supply circuit (10) is selected and output, and the external arc (8
).

Here, for example, when an "H" signal is input to the switching circuit (11), that is, when V rat > VIB, the constant voltage power supply circuit (10) is selected and output, and vice versa.
When the “L” signal is input, that is, V raf≦V,
, if the circuit is configured to select and output the constant current pulse power supply circuit (3), the motor speed setting signal V
, is relatively small (ie in a relatively low current region), short arc welding is performed and the motor speed setting signal V. When is relatively large (that is, in a relatively large current region), pulsed arc welding is performed. Therefore, the drawbacks of conventional pulsed arc welding in the low current range can be overcome. Moreover, the dual power supply circuit (3), (
Since the switching in 10) is performed automatically without requiring any response operation, there is no loss in work efficiency.

〔Effect of the invention〕

As explained above, this invention is equipped with a constant current pulse power supply circuit and a constant voltage power supply circuit, and automatically selects and outputs one of the above two power supply circuits depending on the speed setting value of the wire feeding motor. As a result, the drawbacks of conventional pulsed arc welding power sources, especially in the low current range, can be overcome, and the power supply circuit can be switched at the optimum time without impairing workability.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a pulsed arc welding power source showing an embodiment of the present invention, Fig. 2 is a block diagram showing a conventional general pulsed arc welding power source, and Fig. 3 is a conventional block diagram showing a conventional pulsed arc welding power source having two power supply circuits. FIG. 2 is a block diagram showing a pulse arc welding power source of FIG. (1)...Motor speed setting device, (2)...Motor drive circuit, (3)...Constant current pulse power supply circuit, (4)...Wire feeding motor, (5)... Wire, (7)...Arc, (9)...Work, (lO)...Constant voltage power supply circuit, (11)...Switching circuit, (12)...Switching point setter, ( 13)...Signal generator. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] Motor speed setting that sets the speed of the wire feeding motor that feeds the consumable electrode in the power source for consumable electrode pulse arc welding, which feeds the consumable electrode to the workpiece and generates an arc between it and the workpiece to perform welding. a motor drive circuit that drives the wire feed motor at a desired speed based on the signal from the motor speed setting device, a constant current pulse power supply circuit, a constant voltage power supply circuit, and a switching point that sets the switching point. A setting device, a signal generator that compares the magnitude of the signal from this switching point setting device and the signal from the motor speed setting device, and outputs a switching signal based on the result, and a switching signal from this signal generator. A pulsed arc welding power source comprising a switching circuit that selectively switches between the constant current pulse power supply circuit and the constant voltage power supply circuit.