JPS5970470A - Pulse arc welding machine - Google Patents

Abstract

PURPOSE:To obtain a titled welding machine that stabilizes arc condition and equalizes droplet transfer by magnetically connecting a smoothing reactor for total current and a smoothing reactor for base current and changing the base current according to behavior of peak current. CONSTITUTION:In a pulse arc welding machine that welds a base metal 12 supplying a welding current from a rectifier 1, controlling a peak current iP by the transistor 2 of a switching element, and controlling a base current iB by the transistor 3 of a switching element and feeding a welding wire 10 by a wire feeding device 11, a smoothing reactor 4 for total current ia of combined iP and iB and a smoothing reactor 5 for iB are wound around the same iron core to generate induced electromotive force in the same direction. Consequently, iB decreases suddenly in the leading edge of iP, and transition of ia is carried out smoothly. In the trailing edge, iB increases once and then decreases, and transition to base section is carried out smoothly.

Description

[Detailed description of the invention] The present invention relates to a consumable electrode type pulse arc welding machine.

Consumable electrode type pulsed arc welding, which transfers a droplet spray with relatively low heat input, is performed with a current waveform as shown in FIG. A is the rising section of the peak current iA where the welding wire is heated and melted and grows as a droplet, B is the peak section where the droplet is subjected to pinching force, and C is the section where the droplet detaches from the welding wire and transfers to the base metal. A falling section D of the peak current 1p is a base section where the welding wire is preheated by the base current IB.

Conventionally, a welding machine used for such welding has been constructed as shown in FIG.

1 is a rectifier, 2 is a transistor which is a switching element for controlling the peak current 1p, and 6 is a base current IB.
4 is a smoothing reactor with a total current ia, which is the sum of iP and +B.
5 is a smoothing reactor for the base current IB, 6 is a diode that flows a flywheel current 'Dp due to the induced electromotive force of the smoothing reactor 4 when the transistor 2 is off, and 7 is a flywheel that is caused by the induced electromotive force of the smoothing reactor 5 when the transistor 6 is off. A diode that allows current 'DB to flow, 8 is an output current detector, 9 is a base current detector, 10 is a welding wire,
11 is a wire feeding roller, 12 is a base material, and 16 is a wire feeding control circuit that drives the wire feeding roller 11.

14 is an output current control circuit of the welding machine, which is composed of elements 15 to 24.

The output current detection circuit 18 amplifies the detection signal of the total current ia from the output current detector 8, and the peak signal generation circuit 20 amplifies the signal from the output current detection circuit 18 and the output current setter 15.
A signal (peak signal) for turning on and off the transistor 2 so that the detected value of the total current ia matches the set value is sent to the peak current control transistor drive circuit 26 via the peak/base changeover switch 22. .

The peak/base changeover switch 22 selects the peak time (tP) and base time (tP) set by the pulse frequency setter 16.
B) It is a switch that is turned on only for the tP waiting time in response to [see FIG. 6].

Base current detection 1 (j 1111 path 19 amplifies the base current IB detection signal from the base current detector 9, and the base signal generation circuit 21 amplifies the signal from the base current detection circuit 19 and the signal from the base current setter 17. tP, tT]
It is sent to the base current control transistor drive circuit 24 during the breakthrough period.

The peak current 1P is 1a〈■yu+ as shown in Figure 4.
When α, keep transistor 2 on and 'a''Ia
+α turns off transistor 2, i,)I,−
When α, transistor 2 is kept off and 1a==I
, -α is obtained by controlling the transistor 2 to turn on and off so that the cycle of turning on the transistor 2 is repeated. Similarly, regarding the base current IB, IB-
This can be obtained by controlling the transistor 6 on and off within the range of ±β.

(2) is the set value of the total current Ia, (2) is the set value of the base current 1B, and α and β are constants determined by the circuit configuration.

・ 6 ・ Total current la, base current IB, and output voltage ■ when consumable electrode type pulse arc welding is performed using the welding machine shown in Figure 2. An example of the waveform is shown in FIG. 4 or 5.

That is, the base current IB flows even during the tP period when the peak current jp flows, and does not become zero.

In addition, its value also changes depending on the timing of transition from the base interval (a-b) to the rising interval of IP (b-c, ) (iBO value at the time of transition). When transitioning to (b-c) 1. B-
If transistor 3 is on at □-α, lp
The value of IB decreases relatively slowly with the rise of The value of jB drops rapidly at the moment it rises.This is because the base current lB is suppressed by the output voltage of the peak current circuit when transistor 2 is turned on. In (c-d),
When transistor 2 is off, the value of iB increases, and when transistor 2 is on, the value of IB decreases.

Figures 4 and 5: In the peak section (C-d), the total current 1 is the sum of the peak current 1P and the base current ■ゎ.
■. It is controlled by turning on and off the transistor 20 so that it falls within a predetermined range of ±α, but the rise period (+) of jp
-C) shows that ia changes depending on the value of IB. Voltage v generated in smoothing reactor 4 as ia changes
LP also changes.

Since the sum of vLP and output voltage va is almost constant, vL
When P changes, va also changes. Further, since the flywheel current IDP flowing through the diode B is determined by the value of vLP, when vLP changes, 'DP also changes. As a result, the rising waveform of ia and the on/off period of transistor 2 change depending on the iBO value, and it is desirable that the current (total current) Ia during the tP period be uniform.

The output current ia during the tP period controls droplet growth and migration, is one of the most important factors in pulsed arc welding, and has a great influence on droplet migration and arc stability. That is, if the output current ia during the tP period is not always uniform, the droplet transfer will lack uniformity, the arc stability will deteriorate, and the welding result will be adversely affected.

Next, paying attention to the falling section (d-e) of lp, the 4th
In both FIG. 5 and FIG. 5, the value of IB is larger than the base interval. During the falling edge υ of ip, the transistor 2 turns off, and a flywheel current 'DP flows between the wire 10 and the base material 12 due to the diode A. On the other hand, the transistor 3 is controlled so that the current 1 flowing through the base current detector 9 is 18±β, but when the transistor 2 is off, the diode 6 is on, and the base current circuit is connected via the diode 6. Since the condition is the same as in the case of a short circuit, the base current IB tends to over-sheet, a current exceeding the control upper limit flows, and the average value of iB becomes larger than in the base section. As a result, the waveform of the plate □ in the falling section (de) becomes as shown in FIG. 41 or FIG. 5.

If we observe the Ia waveform at the time of falling in more detail, the reduction rate i of ia changes each time the transistor 3 is turned off, and -1 becomes a small force. This is because the flywheel current 'DB flowing through the diode 7 when the transistor B is turned off is added to the flywheel current Ir)P caused by the diode B, and as a result, the slope of the fall of one waveform increases every time the transistor 6 is turned off. Those who are loose are being washed away. As a result, compared to the case where the IB value at the time of falling is zero, the amount of arc heat after the droplet detaches becomes larger, and while this is repeated, the droplet grows too fast and cannot be detached due to the peak current. Coupled with the fact that the output current la during the tP period is not uniform, the uniformity of the droplet transfer is inhibited.

Well, if you pay attention to the waveform of the output voltage va, as shown in Figures 4 and 5, due to the delay in the fall of the output current Ia, the falling interval of ip transitions to the base interval (e-'f). Since the output voltage va at this time has significantly decreased, the arc may become unstable at this transition point, causing potency and weldability to deteriorate.

・ 7 ・ It is an object of the present invention to solve the problems of the prior art described above and to provide a consumable chamber/polar pulse arc welding machine that improves the uniformity of droplet transfer and the stability of the arc. .

As mentioned above, the problem with the conventional technology is that the value of the base current IB during the peak current rise period changes depending on the timing of transition from the base period to the peak current rise period, which affects the rise waveform of the total current ia. However, in the peak current falling section, the total current is 1 due to the influence of the base current IB.
This is due to the delay in the fall of a. Therefore, in the present invention, the smoothing reactor for the total current or peak current and the smoothing reactor for the base current are magnetically coupled so that their respective induced electromotive forces are in the same direction, and the peak current IP is At 1:00, the base current IB is controlled by the electromotive force induced in the base current smoothing reactor to reduce the change in the value of IB when the peak current rises and the delay in the fall of the total current it when the peak current falls. It is something that we are trying to do.

Embodiments of the present invention will be described below with reference to the drawings.

・ 8 ・ FIG. 6 is a diagram showing an embodiment of the present invention. In the figure, the same reference numerals as in FIG. 2 indicate corresponding parts, and the explanation thereof will be omitted.

However, the smoothing reactor 4 for the full current and the smoothing reactor 5 for the base current are wound around the same iron core 25, and generate induced forces in the same direction as the polarities are indicated by black circles. A bypass diode 26 is connected in parallel to the transistor 6 in order to prevent the transistor 6 from being destroyed by the back electromotive force induced in the base current smoothing IJ actor 5 when the peak current 1P rises.

Figure 7 shows the total current flowing through the output current detector 8 in Figure 6.
. The waveforms of the base current iB flowing through the base current detector 9 and the output voltage va are shown.

In FIG. 7, 1a=iB in the base section (ab and ef). In the rising and rising sections (b-c) of the peak current 1p, the back electromotive force induced in the base current smoothing reactor 5 by the magnetic flux change accompanying the increase in IP acts to suppress the base current IB, and its effect is as follows. It continues as long as IP is increasing, and continues even if IB goes in the opposite direction (negative value). Therefore, as shown in the figure, the base interval (a-b)
When transitioning from lp to the rising section (b-c), IB=
■Even if transistor 6 is turned on in yaw β, lp
With the rise of 51B, the decrease in 51B becomes steeper than in the IB waveform of FIG. 4, and the value of iB during the peak current rise section changes less depending on the value of IE at the transition point. Therefore, the rising waveform of the total current ia is less likely to be affected by the value of IB. During the period (b'-c) in FIG. 7, the reverse current IB flows through the diode 6, and the resulting magnetic flux is produced in a direction that cancels the magnetic flux due to lp, so that ip rises more rapidly.

In the falling period (d-e) of the peak current ip, contrary to the rising period, the electromotive force induced in the base current smoothing reactor 5 due to the magnetic flux change accompanying the decrease in ip increases the base current I.
It works to increase B.

At this time, the transistor 2 is off, and the flywheel current 'DP flowing through the diode 6 becomes the peak current iP. On the other hand, when the value of 1B exceeds the control upper limit value, the transistor 6 is also turned off, and the flywheel current 'DB flowing through the diode 7 becomes the base current IB. IB increases as 1F decreases until point d' in the middle of the peak current falling section, but after that IB also decreases and IE
When ``I B-β'' is crossed, the transistor 3 is turned on and the transition is made to the base interval (e-f). (The value of ip and 1B at point 1' is determined by the mutual inductance of smoothing reactor 4 and smoothing reactor 5.

Turn on and off transistor 2 and set the value of Ip to Ia=I, ±
In the peak section (c-d) where transistor 2 is on, as in the (b-〇) section, and when transistor 2 is off, as in the (d-e) section, the in
The value of increases or decreases.

That is, by adopting the configuration shown in FIG. 6, the base current IB changes according to the behavior of the peak current IP, and as a result, the value of IB during the IP period is always equalized, and therefore the total current Ia is The values are also almost uniform. In addition, the base current IE in the falling period of the peak current flows due to the electromotive force induced in the base current smoothing reactor 5 as the peak current decreases. The delay in the ia falling waveform caused by the base current drop is eliminated, the output voltage VtL does not fall too much as seen in the va waveform in Figure 7, and the transition from the peak current falling section to the base section is smooth. It is carried out. Therefore, compared to the case using the welding machine shown in FIG. 2, the arc condition becomes more stable, droplet transfer becomes uniform, and weldability is improved.

FIG. 8 is a diagram showing another embodiment of the present invention, in which the mode of magnetic coupling between the smoothing reactor 4 for full current and the smoothing reactor 5 for base current is the same as in FIG. 6, but when the peak current rises, smoothing for base current In order to protect the transistor 6 from the back electromotive force induced in the reactor 5, a reverse current prevention diode 27 is connected in series with the transistor 6.

FIG. 9 shows the waveforms of the total current ia, base current IB, and output voltage V& when the configuration shown in FIG. 8 is adopted. In this embodiment, the negative value of iB is canted by the reverse current prevention diode 27, and IB becomes zero between (b' and c). The iB waveform 12 in other sections is the same as that in FIG. In the example of FIG. 6, as mentioned above, since IB takes a negative value between (b' and c), the rise of IP becomes faster and shows a rapid current change. ) to the constant Ip interval (c-d), the arc state may be disturbed, but in the example of Fig. 8, the rising speed at the start of the rise of Ip is fast, but 1B = 0
At this point, the rising speed of lp becomes slow, so the transition from the IP rising section to the constant Ip section occurs smoothly, without disturbing the arc state.

In the embodiments shown in FIGS. 6 and 8, the structure is such that both the peak current and the base current flow through the smoothing reactor 4, but if you pay attention to the coupling between the smoothing reactor 4 and the smoothing reactor 5, the smoothing reactor 4 can be configured so that only the peak current flows. Almost the same effect can be obtained even if the reactor 5 is configured as a smoothing reactor with only a base current. Furthermore, if the base current control switching element has sufficient reverse withstand voltage against the induced electromotive force of the smoothing reactor 5, the protection diodes 26 and 27 are not necessary, and the use of the protection diodes 26 and 27 is an essential requirement. isn't it.

The effects of the present invention can be summarized as follows.

(1) The transition from the base section to the peak current rising section and the transition from the peak current falling section to the base section are performed more smoothly, and the output voltage does not drop too much during the latter transition.

(2) Since the base current value during the peak current period is always equalized, the rise and fall speeds of the output current (total current) change depending on the value of the base current when the peak current rises or falls. This can be prevented and the uniformity of output current can be improved.

According to the present invention, the smoothing reactor for full current or peak current and the smoothing reactor for base current are magnetically coupled, and protection diodes are inserted as necessary, without complicating the circuit configuration of the welding machine. , improves droplet transfer uniformity and arc stability in consumable electrode pulsed arc welding.

Weldability can be improved.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of current waveforms in pulsed arc welding, Figure 2 is a circuit configuration diagram of a conventional pulsed arc welding machine, Figure 6 is an explanatory diagram of peak time tP and base time tB, and Figures 4 and 5. is the total current la in the conventional pulse arc welding machine,
A waveform diagram of base current 1B and output voltage va, FIG. 6 is a circuit configuration diagram showing an embodiment of the present invention, FIG. 7 is a waveform diagram of ia, 1, and va in the embodiment of FIG. 6, and FIG. 9 is a circuit configuration diagram showing another embodiment of the present invention, and FIG. 9 is a waveform diagram of ia, iB, and va in the embodiment of FIG. 1... Rectifier 2... Transistor for pulse current control (first switching element) 6... L transistor for base current control (second switching element) 4... First smoothing reactor for full current 5. ... Second smoothing reactor for base current 6.7 ... Flywheel diode 8 ... Output current detector 9
... Base current detector 10 ... Welding wire
11...Wire feeding roller 12...Base material
16... Wire feeding control circuit 15 14... Welding machine output current control circuit 25... Iron core 26 that magnetically couples the smoothing reactor 4.5
... Bypass diode 27 ... Reverse current prevention diode Patent attorney Junnosuke Nakamura 16. Fig. 1 IP 3 causes off Fig. 1 = 8 Fig. 9 Fig.

Claims (1)

[Claims] A first switching element for peak current control, a second switching element for base current control, and control for turning on and off the first switching element so that the total current including the first peak lightning current and the base current is within a predetermined range. a control means for turning on and off the second switching element so that the base current falls within a predetermined range; a first smoothing reactor for the total current or the peak current; and a second smoothing reactor for the base current; In a pulsed arc welding machine that transfers droplets from a welding wire to a base metal using an electric current, a first smoothing reactor and a second smoothing reactor are magnetically coupled so that their respective induced electromotive forces are in the same direction. A pulse arc welding machine featuring