JPS5916672A - Pulsed arc welding machine - Google Patents

Abstract

PURPOSE:To provide a titled device which enables stable welding from a small current range up to a large current range by the constitution wherein a peak current value is controlled in accordance with the detected value of the arc voltage in welding current and a base current value is controlled in accordance with the detected value of the base current. CONSTITUTION:Welding is accomplished by flowing peak current and base current by turning-on and off of a current control transistor 2 and the fluctuation in current application rate and generating a pulsed arc 8 between a welding wire 6 to be fed at a specified speed and base materials 7. The detected arc voltage value detected with an arc voltage detection circuit 16 during welding and the set value of a setting circuit 17 arc compared, and a peak current value is controlled with the TR 2 by a control circuit 14 so as to make both to coincide. The base current value detected with a shunt resistor 5 and a current detection circuit 18 and the set value of a setting circuit 19 arc compared and the base current value is controlled with the TR 2 by a control circuit 15 to make both to coincide.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a consumable electrode type pulse arc welding machine, and in particular has an improved arc length compensation function for keeping the arc length constant against disturbances such as camera shake of the welding torch.

Pulsed arc welding using a consumable electrode is performed with a current waveform as shown in FIG. 1 in order to spray and transfer droplets with a relatively low heat input. a is the peak section where the heated and melted droplet of the consumable electrode (welding wire) is separated by the electromagnetic pinch force caused by the peak current Ip and transferred to the base material, b is the section where the consumable electrode is preheated with the base current In, The time of a tenth is called the pulse period.

Conventional consumable electrode type pulse arc welding machines usually control the external output characteristics of the welding power source to have constant current characteristics in both the peak section and the base section, and change the output average current by changing the pulse frequency. It is. Methods for compensating the arc length in such a conventional consumable electrode type pulse arc welding machine include (a method of changing the time of one pick section a), (2) a method of changing the time of one nopik section a, and (2) a method of compensating for the arc length among the elements shown in Figure 1. There were two methods: (3) changing the base current value; and (3) changing the base current value.

However, since the pulse frequency changes with the output average current, the base section disappears in the large current region as shown in FIG. 2, and the waveform is forced to have a continuous peak section a only. Arc length compensation must work effectively even in this large current range, but since the base section has disappeared, methods (2) and (3) above cannot function, and the current waveform Since the peak interval a is continuous, (
The method 1) has the disadvantage that it is difficult to compensate for the arc length with sufficient margin.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and provide a pulse arc welding machine that has an effective arc length compensation function from a small current range to a large current range and can perform stable welding.

In order to achieve the above object, the present invention detects the arc voltage and controls the peak current value so that the detected value matches the set value, and on the other hand, detects the base current and controls the detected value so that the detected value matches the set value. By controlling the base current value as shown in FIG. 3, the external output characteristics of the welding power source are made to be constant voltage characteristics with a slight downward trend in the peak section and constant current characteristics in the base section.

Considering the case where the arc length changes in Figure 3, when the arc length increases from Lo to Ll, the droplet diameter per pulse becomes smaller because the peak current value decreases from Ipo to Ip+ in the peak section. Therefore, the arc length decreases and returns to the original arc length according to the set arc voltage. Also, the arc is long. When the peak current value decreases from Ipo to L2 in the peak section, the peak current value decreases from Ipo to Ipo.
By increasing to F5, the droplet diameter per 1 pulse becomes larger, and therefore the arc length increases and returns to the original arc length according to the set arc voltage.

Even in the case shown in Figure 2, where the output current is dominated only by the peak section a in the large current range, the peak current value Ip can be changed freely, so it is possible to control the arc voltage to keep it constant. is easy and can provide arc length compensation with sufficient margin.

In the small current range, the base section a is longer than the peak section a, but the arc length can be sufficiently controlled by changing only the peak current value. T.

Let be the time of peak section a, and TB be the time of base section a, then, for example, Ip = 380 A, IB = 3
When 5A, Tp = 4ms, average current ■m-10O
In case A, the pulse period is Tki21m5. This is 3.372% of the current flowing in the peak section a, indicating that the arc length can be controlled even by slightly changing Ip.

The reason why the external output characteristic of the base section is set to be a constant current characteristic is to keep the heat input to the base section constant even if the arc length changes, thereby eliminating arc breakage.

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

FIG. 4 is a diagram showing one embodiment of the present invention. In the same figure, the welding power source, which is composed of a rectifier circuit 1, a current control transistor 2, a free wheel diode 3, and a smoothing afterter 4, operates the current control transistor 2 on and off at a constant cycle to control its conduction rate. By changing the peak current and the base current, a pulse arc 8 is generated between the welding wire 6 and the base metal 7 in the superimposed output current. The welding wire 6 is fed at a substantially constant speed by a wire feeding roller 9 driven by a wire feeding control circuit 10.

・ 4 ・ 11 is a transistor drive circuit that turns on and off the current control transistor 2, 12 is a pulse frequency setting circuit 13
This is a peak/base switch that transmits control signals from the peak current control circuit 14 and the base current control circuit 15 to the switching transistor drive circuit 11 according to the times of the peak section and base section set in .
1. The peak current control circuit 14 calculates the average value of the arc voltage detected by the arc voltage detection circuit 16 and the arc voltage setting circuit 1.
7 and generates a control signal for controlling the peak current value Ip so that the two match. In the region where the pulse frequency is high and the output average current is large, the arc length is longer than in the small current region, so as shown in the figure, the arc voltage setting of the arc voltage setting circuit 17 is adjusted in relation to the pulse frequency set by the pulse frequency setting circuit 13. Values can be set centrally. On the other hand, the base current control circuit 15 uses the base current value detected by the shunt resistor 5 and the current detection circuit 18 and the base current setting circuit 19
A control signal is generated to control the base current value IB so that the two values match.

20 is a peak current limiter circuit, and the peak current 1 detected by the current detection circuit 18 is transmitted to the peak current limiter setting circuit 2.
When the current value exceeds the set current value of 1, the peak current control circuit 14
The current control transistor 2 is turned off regardless of the output of the current control transistor 2. 22 is a diode that becomes conductive when the output of the peak current limiting circuit 20 becomes off level.

In the above configuration, when the average value of the arc voltage detected by the arc voltage detection circuit 16 becomes larger than the set voltage value of the arc voltage setting circuit 17, the control signal from the peak current control circuit 14 When the average value of the arc voltage becomes smaller than the set voltage value, the control signal from the peak current control circuit 14 increases the conduction rate of the current control transistor 2 to reduce the peak current value Ip. It works to increase the value Ip. On the other hand, when the base current value detected by the current detection circuit 18 becomes larger than the set current value of the base current setting circuit 19, the control signal from the base current control circuit 15 reduces the conduction rate of the current control transistor 2 and When the current value is decreased and the detected base current value becomes smaller than the set current value, the control signal from the base current control circuit 15 increases the conduction rate of the current control transistor 2 (thus increasing the base current value). work like that.

As a result, as shown in Figure 3, the peak part output characteristic of the welding power source becomes a constant voltage characteristic, and the base part output characteristic becomes a constant current characteristic, and arc length compensation functions effectively from a small current range to a large current range. At the same time, constant heat input is ensured in the base section.

FIG. 5 is a diagram showing another embodiment of the present invention. In this embodiment, a peak current control transistor and a base current control transistor are provided separately, and accordingly, a flywheel diode, a smoothing reactor, a shunt resistor for current detection, a transistor drive circuit for control, and a control transistor drive circuit are provided in the power supply circuit. Although two sets of current detection circuits are required, the basic configuration and function are the same as the embodiment shown in Fig. 4, so the fourth
・ 7 ・ Parts that correspond to those in the figures are indicated by the same reference numerals and their explanations will be omitted. The part with the subscript a in Fig. 5 is for the peak;
The portion with a subscript is for the base, and the peak/base switch 12 is turned on only in the peak section to generate a peak current.

Although each of the above embodiments uses a transistor as a current control switching element, a similar configuration can be made using a thyristor.

As explained above, in the pulse arc welding machine according to the present invention, the arc length compensation works effectively from the small current range to the large current range by controlling the peak current value corresponding to the change in the arc voltage, and the constant current control of the base current Since a constant heat input can be ensured in the base section, the arc can be maintained stably against disturbances with a relatively simple configuration, and good welding results can be obtained.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of pulsed arc welding, Fig. 2 is the same (output current waveform diagram in a large current range), Fig. 3 is a functional explanatory diagram of the present invention, and Fig. 4 is an example of the present invention. 8. The block diagram shown in FIG. 5 is a block diagram of another embodiment. ■ = Rectifier 2 of welding power source: Current control transistor 6: Welding wire 7: Base material 8: Arc 9: Wire feeding roller 10: Wire feed control circuit 11: Transistor drive circuit 12: Peak/base switch 14: Peak current control circuit 15: Base current control circuit 16: Arc voltage detection circuit 17 = Arc voltage setting circuit 18 Two current detection circuits 19: Base current setting circuit agent patent attorney Junnosuke Nakamura

Claims (1)

[Claims] In a pulse arc welding machine that generates an arc between a welding wire fed at a nearly constant speed and the base metal using a welding power source that generates an output current with a waveform that is a superimposition of a peak current and a base current, the arc voltage is It includes means for detecting and controlling the peak current value so that the detected value matches the set value, and means for detecting the base current and controlling the base current value so that the detected value matches the set value. A pulse arc welding machine characterized by: