JP2002361417A - Output control method for power unit of pulsed arc welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an output control method for forming external characteristics having an inclination Ks [V/A] of the optimum value for the purpose of improving welding performance in a power unit for pulsed arc welding. SOLUTION: In the output control method for a pulsed arc welding power unit, the inclination Ks of external characteristics is preliminarily set, as are a welding current setting value Is and a welding voltage setting value Vs, and the output of the welding power unit is controlled in the manner that a welding current average value Iw(n) of one period and a welding voltage average value Vw(n) of one period in the n-th pulse period Tpb(n) during welding maintains a relation of Vw(n)=Ks.(Is-Iw(n))+Vs. The external characteristics having the inclination Ks of the optimum value are thereby formed for welding to be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling an output of a welding power supply device for forming an external characteristic having a predetermined slope Ks in consumable electrode pulse arc welding.

[0002]

2. Description of the Related Art In consumable electrode pulse arc welding, it is extremely important to maintain an appropriate arc length during welding in order to maintain good welding quality such as beautiful bead appearance and uniform penetration depth. It is. Generally, the arc length is determined by the balance between the feeding speed and the melting speed of the welding wire. Therefore, when the feeding speed during welding is constant and the feeding speed is equal to the melting speed substantially proportional to the average value of the welding current, the arc length is always constant. However, since the feed speed during welding fluctuates due to fluctuations in the rotation speed of the feed motor, frictional forces in the feed path due to bending of the welding torch, etc., the balance with the melting speed is lost, and the arc length is reduced. Change. The arc length also changes due to fluctuations in the distance between the tip and the workpiece due to hand shake of the welding operator, irregular vibrations of the molten pool, and the like. Therefore,
In order to suppress the change in the arc length due to these various fluctuations (hereinafter, referred to as disturbance), it is necessary to always adjust the melting speed in accordance with the disturbance to suppress the change in the arc length (hereinafter, arc length). Control).

This arc length control method utilizes the fact that the arc length and the average value of the welding voltage are substantially proportional to each other, so that the welding power source is controlled so that the average value of the welding voltage becomes equal to a predetermined target value. Methods of controlling the output of the device are commonly used. Hereinafter, the output control method of the prior art 1 will be described.

[Prior Art 1] FIG. 2 is a current / voltage waveform diagram of pulse arc welding. FIG. 3A shows the temporal change of the welding current instantaneous value Io, and FIG. 3B shows the temporal change of the welding voltage instantaneous value Vo. Hereinafter, description will be made with reference to FIG.

[0005] A period from time t1 to time t2 (peak period T
p) During the predetermined peak period Tp, a predetermined peak current Ip of about 300 to 600 [A] is applied to transfer the droplet as shown in FIG. As shown in B), the welding voltage instantaneous value Vo becomes the peak voltage Vp in accordance with the above-described energization. The length of the peak period Tp is 1 to 3 depending on the material and diameter of the welding wire.
[Ms] is set in advance.

A period from time t2 to t3 (base period T
b) During the base period Tb, a predetermined base current Ib is applied to a low current value of about 20 to 80 [A] in order to prevent droplet transfer as shown in FIG. As shown in (B), the welding voltage instantaneous value Vo becomes the base voltage Vb according to the above-described energization.

[0007] As shown in FIG. 1A, the average value of the welding current instantaneous value Io during one cycle (pulse cycle Tpb) is the one-cycle welding current average value Iw. Similarly, FIG. As shown, one cycle of the welding voltage instantaneous value Vo (pulse cycle Tp
The average value during b) is the one-cycle welding voltage average value Vw.
In the pulse arc welding power supply device, as described above,
Output control for maintaining the arc length at an appropriate value is performed as follows. That is, one cycle welding voltage average value Vw
Is represented by the following equation. Vw = (1 / Tpb) · ∫Vo · dt (1) where integration is performed during the pulse period Tpb (time t1 to t3). The time length of the pulse period Tpb is controlled such that the one-period welding voltage average value Vw shown in the above equation becomes equal to the predetermined target welding voltage set value Vs. Note that, when Vw = Vs is substituted into the equation (1) and transformed, the following equation is obtained. ∫ (Vs−Vo) · dt = 0 (2) where the integration of the voltage error integrated value Sv is performed during the pulse period Tpb. In the above equation, the voltage error integrated value Sv = ∫ (Vs
−Vo) · dt. The calculation of the voltage error integrated value Sv is started from the start of the pulse cycle Tpb at time t1, and when the voltage error integrated value Sv becomes 0 [V] during the base period Tb after time t2, the pulse cycle is started. Tpb
Is completed, and the next pulse cycle Tpb is started. As described above, according to the output control method of the prior art 1, the arc length is appropriately adjusted by controlling the time length of the pulse cycle Tpb so that the one-cycle welding voltage average value Vw for each cycle becomes equal to the voltage set value Vs. Keep at the value.

[Prior Art 2] FIG. 3 is an external characteristic diagram of a welding power supply device showing the relationship between the one-cycle welding current average value Iw shown on the horizontal axis and the one-cycle welding voltage average value Vw shown on the vertical axis.
Hereinafter, description will be made with reference to FIG. The characteristic L1 has a slope Ks =
0 [V / A], and the characteristic L2 has a slope Ks =
It shows an external characteristic of -0.1 [V / A]. In the output control method of the prior art 1 described above, the one-cycle welding voltage average value Vw
Since the output is controlled so as to be equal to a predetermined welding voltage set value Vs irrespective of the value of the one-cycle welding current average value Iw, the above-mentioned external characteristic L1 having a slope Ks = 0 is formed. Become.

It has been widely known that the stability (called self-control action) of the arc length control system is greatly affected by the slope Ks of the external characteristic of the welding power supply device. That is, in order to stabilize the arc length control system, it is necessary to set the slope Ks of the external characteristic to an appropriate value corresponding to various welding methods. For example, in the carbon dioxide arc welding method, the appropriate value of the slope Ks of the external characteristic is (0 to -0.0
3) About [V / A], and in the pulse arc welding method, the appropriate value of the slope Ks of the external characteristic is (−0.05 to −0.3).
It is known to be about [V / A]. Therefore, in the pulse arc welding method which is the object of the present invention, in order to stabilize the arc length control system, instead of the external characteristic L1 shown in FIG.
It is necessary to form the external characteristic L2 having a predetermined slope Ks within a range of about A]. However, as described above, the output control method of the related art 1 cannot form an external characteristic having a slope Ks other than 0 [V / A]. Therefore, in order to solve this problem, an output control method according to Prior Art 2 described below has been proposed. Less than,
The output control method according to the prior art 2 will be described with reference to the drawings.

In the following description, the above-described external characteristic L2 in FIG. 3 is defined as a target external characteristic to be formed. Therefore, the equation of the straight line of the external characteristic L2 is given by the following equation based on the predetermined welding current set value Is, welding voltage set value Vs, and slope Ks. Vw = Ks ・ (Iw-Is) + Vs (3) Hereinafter, an output control method for forming the external characteristic L2 represented by the above expression will be described.

FIG. 4 shows the external characteristic L2 expressed by the above equation (3).
FIG. 9 is a current / voltage waveform diagram for explaining an output control method according to the related art 2 for forming a waveform. FIG. 3A shows the change over time of the welding current instantaneous value Io, and FIG.
5 shows a time change of o. Hereinafter, description will be made with reference to FIG.

At time t (n) at which the n-th pulse cycle Tpb (n) starts, the (n-1) -th pulse cycle Tpb (n-
1) Calculate the previous period welding current average value Iw (n-1) in
= Iw (n-1) is substituted into the above equation (3), and the voltage control set value Vsc (n), which is the target value of the one-period welding voltage average value Vw, is used.
= Ks. (Iw (n-1) -Is) + Vs. In this calculation, the voltage control set value Vsc (n) at the point P1 on the external characteristic L2 in FIG. 3 is calculated. Subsequently, based on the voltage control set value Vsc (n) and the welding voltage instantaneous value Vo, the voltage error integrated value Sv = ∫ (Vsc (n) −Vo) · described in the equation (2) from time t (n). dt is calculated. Then, the time t (n + 1) when the voltage error integrated value Sv during the base period of the n-th pulse cycle Tpb (n) becomes 0 [V].
Then, the n-th pulse cycle Tpb (n) ends and the (n + 1) -th
The first pulse cycle Tpb (n + 1) starts. Therefore,
One-cycle welding voltage average value Vw (n) = Vsc (n) during the n-th pulse cycle Tpb (n). Thereafter, output control is performed by repeating the above operation. According to the output control method of the related art 2 described above, an external characteristic having a predetermined slope Ks can be formed.

FIG. 5 is a block diagram of a welding power supply device PS for implementing the output control method of the above-mentioned prior art 2. Hereinafter, each circuit block will be described with reference to FIG. The voltage detection circuit VD detects the welding voltage instantaneous value Vo and outputs a voltage detection signal Vd. Current detection circuit ID
Detects the welding current instantaneous value Io and outputs the current detection signal Id
Is output. The one-cycle welding current average value calculation circuit IW calculates an average value of the current detection signal Id during one cycle, and outputs a one-cycle welding current average value signal Iw.

A welding voltage setting circuit VS installed outside the welding power supply device outputs a predetermined welding voltage setting signal Vs. A welding current setting circuit IS installed outside the welding power supply device outputs a predetermined welding current setting signal Is. Although not shown, the welding wire 1 is fed at a feeding speed corresponding to the welding current setting signal Is. The slope setting circuit KS outputs a slope setting signal Ks of a predetermined external characteristic. The external characteristic control circuit VSC receives the one-period welding current average signal Iw, the welding voltage setting signal Vs, the welding current setting signal Is, and the inclination setting signal Ks as inputs, and performs voltage control by the above-described equation (3). Setting signal Vsc
Is output. The voltage error integration circuit SV receives the voltage detection signal Vd and the voltage control setting signal Vsc as inputs, performs the integration of the above-described equation (2) from the start of each pulse cycle, and outputs a voltage error integrated value signal Sv. . Comparison circuit CM
Compares the above-mentioned voltage error integrated value signal Sv with 0 [V], and outputs a comparison signal Cm which becomes a High level for a short time when both values become equal. The above-described external characteristic control circuit VSC, voltage error integration circuit SV, and comparison circuit CM form a main part of the output control method of the related art 2 described above in the description of FIG.

The timer circuit MM uses the above-mentioned comparison signal Cm as a trigger signal to generate Hi for a predetermined peak period Tp.
The switching signal Mm having the gh level is output. The peak current setting circuit IP outputs a predetermined peak current setting signal Ip. The base current setting circuit IB outputs a predetermined base current setting signal Ib. The peak / base switching circuit SW receives the switching signal Mm as an input, switches to the a side when the input signal is at a high level, and outputs the peak current setting signal Ip as a current control setting signal Isc. When the signal is at the low level, the current is switched to the side b, and the base current setting signal Ib is changed to the current control setting signal Ib.
Output as sc. The current error amplification circuit EI amplifies the error between the current control setting signal Isc and the current detection signal Id, and outputs a current error amplification signal Ei.

The output control circuit INV uses the above-mentioned current error amplification signal Ei as a control signal, and uses the AC commercial power supply (three-phase 200
[V], etc.) as input, and the output is controlled by inverter control, thyristor phase control, etc., and the welding current instantaneous value Io corresponding to the current control setting signal Isc is supplied. That is, when Isc = Ip, the peak current Ip flows,
When Isc = Ib, the base current Ib flows. Further, the welding wire 1 is fed through the welding torch 4 by the feeding roll 5 a of the wire feeding device, and an arc 3 is generated between the welding wire 1 and the workpiece 2.

FIG. 6 is a timing chart of each signal of the welding power supply device PS described above. FIG. 3A shows the time change of the welding current instantaneous value Io, FIG. 3B shows the time change of the welding voltage instantaneous value Vo, and FIG. 3C shows the time change of the voltage error integrated value signal Sv. (D) shows the comparison signal C
FIG. 7E shows a time change of the switching signal Mm. FIGS. 7A and 7B are the same as FIG. 2 described above. Hereinafter, description will be made with reference to FIG.

A period from time t (n-1) to t (n) (n-1
(Pth pulse period Tpb (n-1)) At time t (n-1), when the voltage error integrated value signal Sv becomes 0 [V] as shown in FIG. As shown, the comparison signal Cm goes high for a short time. In response to this change, the switching signal Mm becomes High level during the peak period Tp, as shown in FIG.
As shown in FIG. 3A, the welding current instantaneous value signal Io becomes a peak current Ip. During the peak period Tp, the voltage error integrated value signal Sv = {(Vsc (n-1) -Vo) .dt =}
The calculation of (Vsc (n-1) -Vp) .dt is performed. Here, since V (n-1) <Vp, as shown in FIG.
The voltage error integrated value signal Sv changes in the negative direction with the passage of time.

As shown in FIG. 2E, when the switching signal Mm changes to Low level, as shown in FIG.
The welding current instantaneous value signal Io becomes the base current Ib. During this base period Tb, the voltage error integrated value signal Sv = ∫ (V
sc (n−1) −Vo) · dt = ∫ (Vsc (n−1) −Vb) · dt
Is performed. Here, since V (n-1)> Vb, as shown in FIG. 3C, the voltage error integrated value signal Sv increases with time, and becomes 0 [V] at time t (n).
become.

The period after time t (n) (at the start time t (n) of the n-th pulse cycle Tpb (n) at the start time t (n) of the n-th pulse cycle Tpb (n), as described above in the description of FIG. Thus, from time t (n-1)
The calculated value of the previous period welding current average value Iw (n-1) during T (n) is substituted into Expression (3), and as shown in FIG. 10B, the n-th pulse period Tpb ( The voltage control setting signal Vsc (n) of (n) is calculated. The subsequent operation is the same as the operation described in the above section, and thus the description is omitted. As described above, according to the output control method of the related art 2, it is possible to form an external characteristic having a predetermined slope Ks.

[0021]

FIG. 7 is a current / voltage waveform diagram corresponding to FIG. 4 described above for describing a problem to be solved. FIG. 3A shows the temporal change of the welding current instantaneous value Io, and FIG. 3B shows the temporal change of the welding voltage instantaneous value Vo. The figure shows the (n-1) th pulse period Tpb (n-1)
In this case, a short circuit occurs between the welding wire and the workpiece during welding. Generally, in pulse arc welding, several to several tens of short circuits occur per second as droplets move. Hereinafter, description will be made with reference to FIG.

As shown in FIG. 2A, when a short circuit occurs during the (n-1) th pulse period Tpb (n-1), the short circuit state is usually released early to regenerate an arc. Is supplied with a short-circuit release current It having a large value. For this reason, the previous period welding current average value Iw (n-1) during the (n-1) th pulse period Tpb (n-1) is larger than the value of the previous period. As described above in the description of FIG. 4, in order to form the external characteristic having the slope Ks, the previous period welding current average value Iw (n-1) is substituted into the equation (3), and The voltage control set value Vsc (n) is calculated. Therefore, when the preceding cycle welding current average value Iw (n-1) increases, the voltage control set value Vsc (n) of the n-th pulse cycle Tpb (n) does not decrease. As a result, the one-cycle welding voltage average value Vw (n) is also reduced, so that the arc length during the n-th pulse cycle Tpb (n) is shorter than the previous cycle, and a short circuit is more likely to occur. . In other words, the occurrence of one short circuit will induce the next short circuit, and the arc state will become unstable, resulting in poor bead appearance, uneven penetration depth, large amount of spatter, and other welding defects. Cheap. In particular, at the time of high-speed welding, in order to prevent the occurrence of welding defects such as undercuts, it is usually necessary to perform welding with the arc length set short. For this reason, a short circuit is likely to occur, and the arc state tends to be unstable in the output control method of the related art.

In the output control method of the prior art 2, since the state of the previous cycle is fed back and the output control of the next cycle is performed, the phase margin of the feedback control system is reduced in principle, and the control system becomes unstable. It is in a state that is easy to become.
For example, when the welding voltage instantaneous value Vo increases due to disturbance during the (n-1) th pulse period Tpb (n-1), the pulse period Tpb (n-) becomes equal to the voltage control set value Vsc (n-1).
The time length of 1) becomes longer. For this reason, since the (n-1) -th preceding cycle welding current average value Iw (n-1) becomes small, the voltage control set value Vsc (n) of the next cycle becomes independent of the arc state in the next cycle. growing. As described above, the voltage control set value Vsc (n) in the next cycle changes due to disturbance in the previous cycle,
This will affect the arc length in the next cycle. As a result, the occurrence of one disturbance may cause a change in the arc length after the next cycle.

Therefore, in the present invention, a predetermined slope Ks
The output control method of the welding power supply device which forms the external characteristics having the above, suppresses the influence on the arc length due to the disturbance of the current cycle by the stable control system during the current cycle, and does not affect the arc length of the next cycle. provide.

[0025]

According to the first aspect of the present invention, as shown in FIG. 8, during a predetermined peak period Tp, a predetermined peak current Ip is applied to a value for causing the droplet to transfer. Then, during the base period Tb, a predetermined base current Ib is applied to a value that does not cause the droplet to transfer, and welding is performed by repeatedly applying a current of one cycle as a pulse cycle Tpb to perform welding. In the output control method of the power supply device, the slope Ks of the external characteristic of the welding power supply device
And the welding current set value Is and the welding voltage set value Vs are set in advance, and 1 in the n-th pulse cycle Tpb (n) during welding is set.
The average welding current value Iw (n) during one cycle and the average welding voltage value Vw (n) during one cycle are represented by Vw (n) = Ks · (Is−Iw
(n)) This is an output control method of the pulse arc welding power supply for controlling the output of the welding power supply so as to maintain the relationship of + Vs.

As shown in FIG. 8, the invention of claim 2 at the time of filing applies a predetermined peak rising period T to the peak period Tp.
It is an output control method of the pulse arc welding power supply device according to claim 1 at the time of filing, in which an up and a predetermined peak fall period Tdw are provided.

The invention of claim 3 at the time of filing is shown in FIGS.
As shown in the figure, during the predetermined peak period Tp, a predetermined peak current Ip is applied to a value that causes the droplet to shift, and then, during the base period Tb, the predetermined base current Ib is set to a value that does not cause the droplet to shift. In the output control method of the welding power supply used for the pulsed arc welding of the consumable electrode in which welding is performed by repeatedly applying the current of one cycle as the pulse cycle Tpb, the slope Ks and the welding current of the external characteristic of the welding power supply are set. The value Is and the welding voltage set value Vs are set in advance,
According to the above set value, the first variable A = Ks · (Ib−I
s) and the second variable B = Ks ・ (Ib-Ip) ・ Tp, and then the welding voltage instantaneous value Vo during welding is detected to determine the nth pulse period Tpb (n) from the start. The slope forming voltage error integrated value Sva = ∫ (A + Vs−Vo) · dt is calculated, and the slope forming voltage error integrated value Sva during the n-th base period Tb following the n-th peak period Tp.
When the value becomes equal to or greater than the value of the second variable B, the n-th pulse cycle Tpb (n) is terminated, and the (n + 1) -th pulse cycle Tpb (n + 1) is started. Is repeatedly performed to form an external characteristic having the above-described inclination Ks, and is used to perform welding.

The invention of claim 4 at the time of filing is shown in FIGS.
As shown in the figure, during the predetermined peak period Tp, a predetermined peak current Ip is applied to a value that causes the droplet to shift, and then, during the base period Tb, the predetermined base current Ib is set to a value that does not cause the droplet to shift. And a predetermined peak rising period Tup and a predetermined peak falling period Tdw are provided in the peak period Tp, and the one-period energization is repeatedly performed as a pulse period Tpb, and consumable electrode pulse arc welding is performed. In the output control method of the welding power supply device used for the second step, the slope Ks of the external characteristic of the welding power supply device, the welding current set value Is and the welding voltage set value Vs are set in advance, and the second method according to claim 3 at the time of filing is described. The operation of variable B is expressed as B = Ks
(Ib-Ip) · (Tp + (1/2) · Tup + (1/2) · Tdw)
An output control method of the pulse arc welding power supply device according to claim 3 at the time of filing the application.

The invention of claim 5 at the time of filing is shown in FIGS.
Claim 3 or Claim at the time of filing, wherein the calculation of the first variable A and the second variable B is performed at every predetermined variable calculation cycle Tc during welding or at each start point of the pulse cycle. 4 is an output control method of the pulse arc welding power supply device according to 4.

The invention of claim 6 at the time of filing is shown in FIGS.
As shown in FIG. 3, a pulse set forth in claim 3 or claim 4 at the time of filing, wherein the welding wire feed speed set value Ws and the material and diameter of the welding wire are set, and the welding current set value Is is calculated based on them. 4 is an output control method of the arc welding power supply device.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A typical embodiment of the present invention is as follows.
As shown in FIG. 1 (same diagram as FIG. 8), the slope Ks of the external characteristic of the welding power supply device, the welding current set value Is and the welding voltage set value Vs are set in advance, and the n-th pulse cycle during welding is performed. The average welding current value Iw (n) during one cycle and the average welding voltage value Vw (n) during one cycle in Tpb (n) are Vw (n) = Ks
An output control method for a pulse arc welding power supply device that performs welding by forming an external characteristic having a slope Ks by controlling the output of the welding power supply device so as to maintain the relationship of (Is-Iw (n)) + Vs. It is.

[0032]

[Embodiment 1] The invention of Embodiment 1 described below corresponds to the inventions of Claims 1 and 2 at the time of filing.
The invention of the first embodiment is directed to the slope Ks of the external characteristic of the welding power supply device.
And the welding current set value Is and the welding voltage set value Vs are set in advance, and 1 in the n-th pulse cycle Tpb (n) during welding is set.
Periodic welding current average value Iw (n) and 1-period welding voltage average value V
This is an output control method of the pulse arc welding power supply device that controls the output of the welding power supply device so that w (n) maintains a relationship of Vw (n) = Ks · (Is−Iw (n)) + Vs. Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 8 is a current / voltage waveform diagram for explaining the output control method of the first embodiment. FIG. 3A shows the temporal change of the welding current instantaneous value Io, and FIG. 3B shows the temporal change of the welding voltage instantaneous value Vo. Referring to FIG.
The external characteristics of the target formed by the output control method of
As in the above-described equation (3), Vw = Vw =
It is a straight line indicated by Ks · (Iw−Is) + Vs. Less than,
Description will be made with reference to FIG.

As shown in the figure, the one-cycle welding current average value Iw (n) and the one-cycle welding voltage average value Vw (n) during the n-th pulse cycle Tpb (n) are calculated. And Vw (n) = K
The time t when the relationship of s · (Iw (n) −Is) + Vs is established
At (n + 1), the n-th pulse cycle Tpb (n) ends, and
Output control is performed so as to start the (+1) th pulse cycle Tpb (n + 1). As a result, the target external characteristics represented by the equation (3) are formed, and in the prior art 2, the previous cycle welding current average value Iw (n-1) and the current cycle one cycle welding voltage average value Vw are obtained.
(n) was in the relationship of the equation (3).
In this case, the one-cycle welding current average value Iw (n) of the current cycle and the one-cycle welding voltage average value Vw (n) of the current cycle have a relationship expressed by equation (3). Therefore, the output control of the current cycle is not affected by the disturbance generated in the previous cycle.

Further, the invention of claim 2 at the time of filing is the case where a predetermined peak rising period Tup and a predetermined peak falling period Tdw are provided in the peak period Tp. This is the same as the output control method of No. 1.

[Embodiment 2] The invention of Embodiment 2 described below corresponds to the inventions of Claims 3 and 4 at the time of filing. Hereinafter, the invention of the second embodiment will be described with reference to the drawings. FIG. 9 is a current / voltage waveform diagram showing set value parameters used in the following description. FIG. 3A shows the temporal change of the welding current instantaneous value Io, and FIG. 3B shows the temporal change of the welding voltage instantaneous value Vo. Hereinafter, description will be made with reference to FIG.

As shown in FIG. 3A, in the n-th pulse period Tpb (n) [s], the peak period Tp [s]
In addition, the peak rising period Tup [s] and the maximum peak period Tpp
[S] and a peak falling period Tdw [s] are provided, and they are set to a predetermined time length. Maximum peak period Tpp
In the middle, a predetermined peak current Ip [A] is conducted, and a peak voltage Vp [V] is applied as shown in FIG. Further, during the base period Tb [s], a predetermined base current Ib [A] flows as shown in FIG.
As shown in FIG. 3B, a base voltage Vb [V] is applied.

The reciprocal of the pulse period Tpb (n) is the pulse frequency f (n) [Hz]. The n-th one-cycle welding current average value Iw (n) [A] is energized, and the n-th one-cycle welding voltage average value Vw (n) [V] is applied. The target external characteristic formed by the output control is expressed by the above-described equation (3) based on a predetermined welding current set value Is [A], a welding voltage set value Vs [V], and a slope Ks [V / A]. Becomes

As described above, the predetermined set value parameters include a peak period Tp, a peak rising period Tup, a maximum peak period Tpp, a peak falling period Tdw, and a peak current Id.
p, base current Ib, welding current set value Is, welding voltage set value Vs, and slope Ks. As described above, the welding current set value Is and the welding voltage set value Vs are often set from outside the welding power supply device. Hereinafter, a control equation corresponding to the above-described equation (2), which is the basis of the second embodiment, will be derived.

The following integrations (1) to (16) are all performed during the period from the start to the end of the pulse period Tpb (n). (1) The relationship between the one-cycle welding current average value Iw and the pulse frequency f is given by the following equation. 1 / f = ((Ip−Ib) / (Iw−Ib)) · (Tpp + (1/2) · Tup + (1/2) · Tdw) (41) Equation (2) Equivalent peak period Tpe [s] It is defined by the following equation. Tpe = Tpp + (1/2) .Tup + (1/2) .Tdw (42) Equation (3) When the above equation is substituted into Equation (41), the following equation is obtained. 1 / f = ((Ip−Ib) / (Iw−Ib)) · Tpe (43) Equation (4) By transforming the above equation, the following equation is obtained. Iw = (Ip−Ib) · Tpe · f + Ib (44) Equation (5) In the above equation, when Iw = Is, f = fs [H
z], the following equation is obtained. Is = (Ip−Ib) · Tpe · fs + Ib (45)

(6) If Iw in equation (44) is Iw (n), the following equation is obtained. Iw (n) = (Ip−Ib) · Tpe · f (n) + Ib (46) Equation (7) The slope Ks of the external characteristic can be expressed by the following equation. Ks = (Vw (n) -Vs) / (Iw (n) -Is) (47) Equation (8) When the equations (45) and (46) are substituted into the above equation, the following equation is obtained. Vw (n) −Vs = Ks · (Ip−Ib) · Tpe · (f (n) −fs) (48) Equation (9) Vw (n) is defined by the following equation. Vw (n) = f (n) · ∫Vo · dt (49) Equation (10) The relationship between f (n) and Tpb (n) can be expressed by the following equation. f (n) = 1 / Tpb (n) (410) Equation (11) The following equation is established from Equations (49) and (410). Vw (n) −Vs = f (n) · ∫ (Vo−Vs) · dt (411) Equation (12) The following equation is established from the above equations and equation (48). f (n) · ∫ (Vo−Vs) · dt = Ks · (Ip−Ib) · Tpe · (f (n) −fs) Equation (412)

(13) By substituting equation (45) into the above equation and rearranging it, the following equation is obtained. ∫Ks ・ (Ib-Is) ・ dt + ∫ (Vs-Vo) ・ dt = Ks ・ (Ib-Ip) ・ Tpe (413) Here, to simplify the equation, the first variable A is introduced and defined by the following equation. A = Ks · (Ib−Is) (5) Equation (15) Similarly, a second variable B is introduced and defined by the following equation,
Substituting equation (42) for Tpe gives the following equation. B = Ks · (Ib−Ip) · Tpe = Ks · (Ib−Ip) · (Tpp + (1/2) · Tup + (1/2) · Tdw) (6) Equation (16) Equation (5) and ( By substituting equation (6) into equation (413), the following equation, which is the control of the invention of the second embodiment, is obtained. ∫ (A + Vs−Vo) · dt = B Equation (7)

At the end of the n-th pulse cycle Tpb (n), the above equation holds. At the start of the n-th pulse period Tpb (n), the above-described set value parameter can be regarded as a constant, so that the first variable A shown in the above equation (5) and the above-mentioned equation (6) are obtained. Can be regarded as a constant. The slope forming voltage error integrated value Sva from the start of the n-th pulse cycle Tpb (n) is defined as Sva = ∫ (A + Vs−Vo) · dt. Usually, Ks ≦ 0, Ib <Is <Ip, Tpe
> 0, A ≧ 0 and B ≧ 0. In FIG.
During the peak period Tp, Vs <Vo (= Vp),
The value of (A + Vs-Vo) becomes either a positive value or a negative value depending on the value of the set value parameter. On the other hand, during the base period Tb, since Vs> Vo (= Vb), (A + Vs−
Vb)> 0, and the above gradient forming voltage error integrated value Sva
During the base period Tb gradually increases with time. Therefore, the slope forming voltage error integrated value Sva from the start of the n-th pulse cycle Tpb (n) is calculated,
The calculated value is equal to the value of the second variable B, or
When the variable B becomes equal to or greater than the value of the variable B, the n-th pulse cycle Tpb (n) ends. That is, the pulse cycle ends when the following equation is satisfied. Sva = ∫ (A + Vs−Vo) · dt ≧ B (8) where integration is performed during Tpb (n).

As described above, the second embodiment of the present invention
A = Ks · (Ib−Is) and the second variable B = K
After calculating s · (Ib−Ip) · Tpe, the welding voltage instantaneous value Vo during welding is detected and the n-th pulse cycle Tpb
The slope forming voltage error integrated value Sva = ∫ from the start of (n)
(A + Vs−Vo) · dt is calculated, and the value of the gradient forming voltage error integrated value Sva in the nth base period Tb following the nth peak period Tp is equal to or greater than the value of the second variable B. , The n-th pulse period Tpb
(n), and then the (n + 1) th pulse cycle Tpb (n +
This is an output control method of a pulse arc welding power supply device that performs welding by forming the external characteristic having the above-mentioned inclination Ks by repeating the above operation after starting 1).

When the slope Ks is set to 0, the first variable A = 0 and the second variable B = 0, and therefore, the equation (8) becomes Sva = ∫ (Vs−Vo) · dt ≧ 0. , Which coincides with the equation (2) in the case of the prior art described above. That is, the special case (Ks = 0) in the equation (8) showing the output control method of the present invention is the case of the equation (2) showing the output control method of the prior art.

If the peak rise period Tup and the peak fall period Tdw do not exist during the peak period Tp, the second variable B = Ks ・ (Ib-Ip) ・ Tp (9) is calculated. Other than that, output control can be performed in the same manner as in the second embodiment.

FIG. 10 is a block diagram of a pulse-per-cycle control welding power supply PSA for carrying out the invention of the second embodiment. This figure illustrates a case where there is no peak rise period Tup and peak fall period Tdw during the peak period Tp. In this figure, the same circuit blocks as those in FIG. 5 described above are denoted by the same reference numerals, and description thereof will be omitted. Hereinafter, a first variable operation circuit CA, a second variable operation circuit CB, a slope forming voltage error integration circuit SVA, and a variable comparison circuit CMA, which are circuit block diagrams indicated by dotted lines different from FIG. 5, will be described.

The first variable operation circuit CA comprises a slope setting signal Ks, a base current setting signal Ib, and a welding current setting signal Ib.
With s as an input, the above-described equation (5) is operated, and the first
Is output. The second variable operation circuit CB includes a slope setting signal Ks, a base current setting signal Ib,
With the input of the peak current setting signal Ip and the peak period setting signal Tp, the calculation of the above-described equation (9) is performed, and the second variable calculation value signal Cb is output.

The gradient forming voltage error integration circuit SVA receives the first variable operation value signal Ca, the welding voltage setting signal Vs, and the voltage detection signal Vd as inputs and starts the n-th pulse cycle Tpb (n). Then, the integration on the left side of the above equation (8) is performed, and the gradient forming voltage error integrated value signal Sva is output.
The variable comparison circuit CMA compares the gradient forming voltage error integrated value signal Sva with the second variable operation value signal Cb, and when the condition becomes SVa ≧ Cb, the comparison signal which becomes the High level for a short time. Cm is output. That is, the above-described equation (8), which indicates the output control method of the present invention, is performed by the gradient forming voltage error integration circuit SVA and the variable comparison circuit CMA. The description of the subsequent operation is the same as that of FIG. In the case where the peak rise period Tup and the peak fall period Tdw are provided in the peak period Tp, the expression of the second variable operation value signal Cb may be replaced with the expression (6).

FIG. 11 shows the time change of the gradient forming voltage error integrated value Sva and the pulse period Tpb shown in the left side of the above-mentioned equation (8).
FIG. FIG. 6A shows the time change of the welding current instantaneous value Io, and FIG. 6B shows the gradient forming voltage error integrated value S from the start point (t0) of the pulse cycle on the vertical axis.
The time change of va is shown, and the horizontal axis shows the time length of the pulse period Tpb. The three characteristics Y1 to Y3 shown in FIG. 9 have the same set value parameters described above in the description of FIG. 9, and therefore, the first variable A, the second variable B, and the welding voltage in the equation (8). When the set value Vs is the same, the case where the arc length during welding is an appropriate value (characteristic Y2), the case where it is shorter than the appropriate value (characteristic Y1), and the case where it is longer than the appropriate value (characteristic Y3) are shown. Hereinafter, description will be made with reference to FIG.

When the Arc Length is an Appropriate Value (Characteristic Y2) The peak voltage when the arc length is an appropriate value is Vp2, and the base voltage is Vb2. Times t0 to t1 shown in FIG.
During the peak period Tp, the slope forming voltage error integrated value S
va gradually increases with time as a calculated value of Sva = ∫ (A + Vs−Vp2) · dt. Then, during the base period Tb after the time t1, the gradient forming voltage error integrated value Sva
Becomes gradually larger with the elapse of time as a calculated value of Sva = ∫ (A + Vs−Vb2) · dt, with a slope different from that during the peak period Tp, and the pulse period Tpb2 ends when Sva ≧ B at time t3.

When the arc length is shorter than the proper value (characteristic Y1) Since the instantaneous welding voltage Vo is proportional to the arc length, the peak voltage when the arc length is shorter than the proper value is Vp1 <Vp2, and the base voltage is Vb1 <Vb2. During the peak period Tp from time t0 to time t1 shown in FIG. 7A, the slope forming voltage error integrated value Sva is Sva = ∫ (A + Vs−Vp1) · d.
As the time elapses, the calculated value of t increases with a steeper gradient than in the above term. Then, during the base period Tb after the time t1, the slope forming voltage error integrated value Sva is equal to Sva =
The calculated value of ∫ (A + Vs−Vb1) · dt increases with time with a gradient different from that during the peak period Tp,
When Sva ≧ B at time t2, the pulse cycle Tpb1 ends. Therefore, when the arc length is shorter than the appropriate value, the pulse period Tpb1 is shorter than Tpb2 in the above term, and the one-cycle welding voltage average value Vw becomes larger, so that the arc length changes in a longer direction. Will approach the appropriate value.

When the arc length is longer than the proper value (characteristic Y 3) Since the instantaneous welding voltage Vo is proportional to the arc length, the peak voltage when the arc length is longer than the proper value is Vp 3> Vp 2, and the base voltage is Vb3> Vb2. During the peak period Tp from time t0 to t1 shown in FIG. 7A, the slope forming voltage error integrated value Sva is Sva = ∫ (A + Vs−Vp3) · d.
As the time elapses, the calculated value of t increases with a gentler gradient than in the above term. Then, during the base period Tb after time t1, the slope forming voltage error integrated value Sva is equal to S
As the calculated value of va = ∫ (A + Vs−Vb3) · dt increases with time with a gradient different from that during the peak period Tp, and when Sva ≧ B at time t4, the pulse period Tpb3
Ends. Therefore, when the arc length is longer than the appropriate value, the pulse period Tpb3 is longer than Tpb2 in the above item, and the one-cycle welding voltage average value Vw becomes smaller, so that the arc length changes in a shorter direction. Will approach the appropriate value. As described above, the pulse cycle changes by changing the gradient of the slope forming voltage error integrated value Sva according to the change in the arc length during welding, and as a result, the one-cycle welding voltage average value Vw changes. Suppress variations in arc length.

[Third Embodiment] The invention of a third embodiment described below corresponds to the invention of claim 5 at the time of filing. The invention of the third embodiment is based on the first variable A and the second variable A in the invention of the second embodiment.
Calculation of the variable B is performed by a predetermined variable calculation period T during welding.
This is an output control method of the pulse arc welding power supply device performed every c [s] or each time the pulse period Tpb starts. Less than,
The invention of the third embodiment will be described.

A welding power supply device for implementing the output control method of the third embodiment has a configuration in which the operations of the first variable operation circuit CA and the second variable operation circuit CB in FIG. 10 are changed as follows. Becomes The first variable operation circuit CA of the third embodiment includes a slope setting signal Ks and a base current setting signal Is.
b and the welding current setting signal Is, and the variable comparison signal Cm is set to a short time H at every predetermined variable operation cycle Tc.
At each start time of the pulse period Tpb at which the high level is set, the calculation of the above equation (5) is performed, and the first variable calculation value signal C
a is output. The second variable operation circuit CB of the third embodiment is
A pulse cycle Tpb in which the slope setting signal Ks, the base current setting signal Ib, the peak current setting signal Ip, and the peak period setting signal Tp are input, and the variable comparison signal Cm is at a high level for a short time every variable calculation cycle Tc. The calculation of the above-described expression (9) or (6) is performed at every start time of the operation, and the second variable operation value signal Cb is output.

In the invention of the third embodiment, even if the set value parameter changes during welding, the first variable A
And the second variable B are recalculated, so that appropriate output control is always performed according to the set value parameter at that time.

[Embodiment 4] The invention of Embodiment 4 described below corresponds to the invention of Claim 6 at the time of filing. According to the invention of the fourth embodiment, the feed wire set value Ws of the welding wire and the material and diameter of the welding wire are set.
It is an output control method of the pulse arc welding power supply device for calculating the welding current set value Is according to the invention of the first aspect. Hereinafter, the invention of the fourth embodiment will be described.

The welding power supply device for carrying out the invention of the fourth embodiment has a welding current setting circuit IS shown in FIG.
Is replaced by a welding current set value calculation circuit CIS described later with reference to FIG. FIG. 12 is a block diagram of the welding current set value calculation circuit CIS. A feed speed setting circuit WS installed outside the welding power supply device outputs a predetermined feed speed setting signal Ws. The welding current set value calculation circuit CIS incorporated in the welding power supply device receives the above-described feed speed setting signal Ws, the material of the welding wire and the diameter of the welding wire as inputs, and calculates the welding current calculated by the melting characteristics illustrated in FIG. The setting signal Is is output.

FIG. 13 shows the feed speed set value Ws shown on the vertical axis.
FIG. 9 is a melting characteristic diagram showing a relationship between the welding current setting value Is shown on the horizontal axis. The figure shows the case where the material of the welding wire is aluminum alloy A5356, and the diameter of the welding wire is 1.
It shows the melting characteristics in the case of 2 [mm] or 1.6 [mm]. For example, the welding current set value Is when the feed speed set value Ws = 900 [cm / min] is Is when the diameter is 1.2 [mm].
= 150 [A], and when the diameter is 1.6 [mm], Is
= 250 [A]. Even when the material of the welding wire is steel, stainless steel, or the like, the welding current set value Is is calculated from the melting characteristic diagram corresponding to FIG.

In the above-described fourth embodiment, the output control method of the present invention can be applied to the case where the feed speed setting signal Ws, which is frequently used in place of the welding current setting signal Is, is input from outside. Can be implemented.

[Effects] FIG. 14 is a current / voltage waveform diagram corresponding to FIG. 7 for explaining the effects of the present invention. FIG. 3A shows the temporal change of the welding current instantaneous value Io, and FIG. 3B shows the temporal change of the welding voltage instantaneous value Vo. This figure shows a case where a short circuit occurs between the welding wire and the workpiece during the (n-1) th pulse period Tpb (n-1), as in the case of FIG.
Hereinafter, description will be made with reference to FIG.

As shown in FIG. 9A, if a short circuit occurs during the (n-1) -th pulse period Tpb (n-1), the short circuit state is released early and an arc is regenerated. A large value short-circuit release current It is supplied. In the present invention, the n-th
The first one-cycle welding current average value Iw (n-1) and the n-1
An operating point which is an intersection (not shown) with the first one-cycle welding voltage average value Vw (n-1) always exists on the target external characteristic having the slope Ks. In addition, since a short circuit occurs during welding when the arc length is short in FIG. 11 described above, the (n−1) -th pulse cycle Tpb (n−1) becomes short as shown in the characteristic Y1. . As a result, the one-period welding voltage average value Vw (n-1) increases, and the arc length is changed in a direction of increasing the arc length.

Next, during the n-th pulse period Tpb (n), the n-th one-cycle welding current average value Iw (n) and the n-th
An operating point, which is an intersection (not shown) with the first one-cycle welding voltage average value Vw (n), always exists on the target external characteristic. Moreover, without being affected by the occurrence of a short circuit in the previous cycle,
The output is controlled so as to stabilize the arc length according to the disturbance during the current cycle.

In the output control method of the present invention, since the state of the current cycle is fed back and controlled irrespective of the previous cycle, the phase margin of the feedback control system becomes larger in principle than the prior art, and the stability of the control system becomes stable. The performance is improved. That is, the fluctuation of the arc length due to the disturbance during each pulse period Tpb is suppressed by the output control during that period, and does not affect the next period.

[0065]

According to the present invention, since the operating points of the one-cycle welding current average value Iw and the one-cycle welding voltage average value Vw in each pulse cycle Tpb always exist on the target external characteristics, each pulse cycle Tpb Variations in the arc length due to disturbances inside are suppressed during the cycle. Therefore, the transient response to the disturbance is excellent, and the fluctuation of the arc length during welding is reduced, so that good welding quality can be obtained. Furthermore, in the invention of the third embodiment, even if the set value parameter changes during welding, the first variable A and the second variable B are recalculated in accordance with the change, thereby always performing proper output control. Can be. Further, in the invention of the fourth embodiment, the output control method of the present invention can be implemented even when the feed speed setting signal Ws is input instead of the welding current setting signal Is from outside.

[Brief description of the drawings]

FIG. 1 is a current / voltage waveform diagram for describing an output control method according to an embodiment.

FIG. 2 Current / voltage waveform diagram of pulse arc welding

FIG. 3 is an external characteristic diagram of the welding power supply device.

FIG. 4 is a current / voltage waveform diagram for explaining an output control method according to Prior Art 2.

FIG. 5 is a block diagram of a welding power supply device according to prior art 2.

FIG. 6 is a timing chart of the welding power supply device of the prior art 2;

FIG. 7 is a current / voltage waveform diagram for explaining a problem to be solved.

FIG. 8 is a current / voltage waveform diagram for explaining an output control method according to the first embodiment.

FIG. 9 is a current / voltage waveform diagram showing set value parameters.

FIG. 10 is a block diagram of a welding power supply device according to a second embodiment.

FIG. 11 is a diagram showing a relationship between a temporal change of a slope forming voltage error integrated value Sva and a pulse period Tpb.

FIG. 12 shows a welding current set value calculation circuit C according to a fourth embodiment.
IS block diagram

FIG. 13 is a melting characteristic diagram showing a relationship between a feed speed set value Ws shown on the vertical axis and a welding current set value Is shown on the horizontal axis.

FIG. 14 is a current / voltage waveform diagram for explaining the effect of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Welding wire 2 Workpiece 3 Arc 4 Welding torch 5a Feeding roll of wire feeder A First variable B Second variable CA First variable operation circuit Ca First variable operation value signal CB Second Variable operation circuit Cb Second variable operation value signal CIS welding current setting value calculation circuit CM comparison circuit Cm comparison signal CMA Variable comparison circuit EI Current error amplification circuit Ei Current error amplification signal f Pulse frequency IB Base period setting circuit Ib Base current ( Setting signal) ID current detection circuit Id current detection signal INV output control circuit Io welding instantaneous value IP peak period setting circuit Ip peak current (setting signal) IS welding current setting circuit Is welding current setting (value / signal) Isc current control setting Signal It Short-circuit release current IW One-cycle welding current average calculation circuit Iw, Iw (n) One-cycle welding current average Signal) KS slope setting circuit Ks slope of external characteristic (setting signal) L1, L2 external characteristic MM timer circuit Mm switching signal P1 operating point PS welding power supply PSA pulse-per-cycle control welding power supply SV voltage error integration circuit Sv voltage error integration Value (signal) SVA slope forming voltage error integration circuit Sva slope forming voltage error integration value (signal) SW peak / base switching circuit Tb base period Tdw peak falling period Tp peak period Tpb, Tpb (n) pulse period Tpp maximum peak period Tup peak rise period Vb base voltage VD voltage detection circuit Vd voltage detection signal Vo welding voltage instantaneous value Vp peak voltage VS welding voltage setting circuit Vs welding voltage setting (value / signal) VSC external characteristic control circuit Vsc voltage control setting (value / signal) ) Vw, Vw (n) One-cycle welding voltage average value WS Feeding speed setting circuit W s Feeding speed setting (value / signal) Y1 to Y3 Melting characteristics

Claims (6)

[Claims] 1. A predetermined peak current is applied to a value that causes droplet transfer during a predetermined peak period, and a predetermined base current is subsequently applied to a value that does not cause droplet transfer during a base period; In the output control method of the welding power supply device used for the pulsed arc welding of the consumable electrode, in which welding is performed by repeatedly applying the current of one cycle as a pulse period, the gradient Ks of the external characteristic of the welding power supply, the welding current set value Is, and the welding voltage The set value Vs is set in advance, and the welding current average value I during one cycle of the n-th pulse cycle during welding is set.
w (n) and the average welding voltage Vw (n) during one cycle are Vw
An output control method for a pulse arc welding power supply that controls the output of the welding power supply so as to maintain the relationship of (n) = Ks · (Is−Iw (n)) + Vs. 2. The output control method according to claim 1, wherein a predetermined peak rise period and a predetermined peak fall period are provided in the peak period. 3. A predetermined peak current Ip is supplied during the predetermined peak period Tp to a value at which droplet transfer is performed, and subsequently, a predetermined base current Ib is set at a value at which droplet transfer is not performed during the base period Tb. The method of controlling the output of a welding power supply device used for pulsed arc welding of a consumable electrode, in which welding is performed by repeatedly applying a current in one cycle as a pulse cycle, comprising: a slope Ks of an external characteristic of the welding power supply and a welding current set value. Is and the welding voltage set value Vs are set in advance, and the first variable A = Ks · (Ib−Is) and the second variable
After calculating the variable B = Ks. (Ib-Ip) .Tp, the welding voltage instantaneous value Vo during welding is detected, and the gradient forming voltage error integrated value S from the start of the n-th pulse cycle is detected.
va = ∫ (A + Vs−Vo) · dt is calculated, and the gradient forming voltage error integrated value Sva in the n-th base period following the n-th peak period is equal to or larger than the value of the second variable B. At this point, the n-th pulse cycle is completed, the (n + 1) -th pulse cycle is subsequently started, and the above operation is repeated, thereby forming an external characteristic having the slope Ks to perform welding. Output control method for welding power supply unit. 4. A predetermined peak current Ip is supplied during a predetermined peak period Tp to a value that causes droplet transfer, and a predetermined base current Ib is subsequently set to a value that does not cause droplet transfer during a base period Tb. In the peak period Tp, a predetermined peak rising period Tup and a predetermined peak falling period Tdw are provided, and consumable electrode pulse arc welding is performed in which welding is performed by repeatedly applying a current in one cycle as a pulse period. In the output control method of the welding power supply device to be used, the slope Ks of the external characteristic of the welding power supply device, the welding current set value Is and the welding voltage set value Vs are set in advance, and the calculation of the second variable B is performed by B = Ks · ( Ib−Ip) · (Tp + (1/2)
The output control method of the pulse arc welding power supply device according to claim 3, wherein (Tup + (1/2) .Tdw). 5. The method according to claim 3, wherein the calculation of the first variable A and the second variable B is performed at every predetermined variable calculation period during welding or at the start of each pulse period. An output control method of a pulse arc welding power supply. 6. The pulse arc welding power source device according to claim 3, wherein a set value of a feed speed of the welding wire and a material and a diameter of the welding wire are set, and the welding current set value Is is calculated based on the set value. Output control method.