JP2003311409A - Method for controlling arch length in pulse arc welding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for controlling arc length in which the arc length is constantly retained to an appropriate value by exactly detecting the arc length even if unusual voltage occurs. <P>SOLUTION: Welding voltage Vw is detected. The detection value of the welding voltage is limited within a predetermined variation range Vc±ΔVc using a reference voltage waveform previously determined as input as a center voltage value Vc to calculate a welding voltage limiting value Vft. The average value of the welding voltage is calculated by using the welding voltage limiting value Vft as input. The arc length is controlled by the average value of the welding voltage obtained from the welding voltage limiting value Vft. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse arc in which a welding wire is fed at a constant speed and a peak current during a peak period and a base current during a base period are repeatedly applied as a pulse period. In welding, the present invention relates to an arc length control method for pulse arc welding, which controls a pulse period and the like so that an average welding voltage value or an average peak voltage value becomes substantially equal to a predetermined target value and maintains an arc length at an appropriate value.

[0002]

2. Description of the Related Art In consumable electrode type arc welding, in order to obtain good welding quality, it is necessary to maintain the arc length during welding at an appropriate value. In consumable electrode type pulse arc welding in which the energization of the peak current during the peak period and the energization of the base current during the base period are repeated as a pulse cycle, the welding voltage average value or the peak voltage average value is a predetermined target value. Conventionally, an arc length control method has been used in which the pulse length and the like are controlled so as to be substantially equal to the arc length and the arc length is maintained at an appropriate value. Hereinafter, this conventional arc length control method will be described with reference to the drawings.

FIG. 1 is a current / voltage waveform diagram of pulse arc welding. FIG. 1 (A) shows the welding current Iw with time, and FIG. 1 (B) shows the welding voltage Vw with time. Hereinafter, description will be given with reference to FIG.

Period of Times t1 to t3 As shown in FIG. 7A, during the peak rising period Tup of times t1 to t2, a transition current rising from the base current Ib to the peak current Ip is conducted, and thereafter, Time t2 to t3
During the peak period Tp of, the peak current Ip is conducted. Similarly, as shown in FIG.
During the period, the transition voltage that rises from the base voltage Vb to the peak voltage Vp is applied, and during the subsequent peak period Tp, the peak voltage Vp is applied. The values of the peak period Tp and the peak current Ip are set to appropriate values so that one pulse / one droplet transfer occurs depending on the type of welding wire, the type of shield gas, the feed rate, and the like.

[0007] During the period from time t3 to t5, as shown in FIG. 7A, during the peak falling period Tdw from time t3 to t4, the transition current flowing from the peak current Ip to the base current Ib is conducted, and thereafter. Time t4 to t5
The base current Ib is conducted during the base period Tb. Similarly, as shown in FIG. 7B, the peak falling period Tdw
During the period, a transition voltage that drops from the peak voltage Vp to the base voltage Vb is applied, and during the subsequent base period Tb, the base voltage Vb is applied. The value of the above base current Ib is
It is set to a low value of about several tens [A] so as not to melt the tip of the welding wire.

Therefore, the pulse period Tf from the time t1 to t5 is formed by the peak rising period Tup, the peak period Tp, the peak falling period Tdw and the base period Tb.
By the way, the values of the peak rising period Tup and the peak falling period Tdw are determined by the inductance value and the resistance value inside and outside the welding power source device. However, in order to reduce the amount of spatter and improve the bead appearance,
The above-mentioned peak rising period Tup and peak falling period Tdw
The value of may be set to a number [ms]. Further, as shown in FIG. 7A, the average value of the welding current Iw becomes the welding current average value Iav, and as shown in FIG. 7B, the average value of the welding voltage Vw becomes the welding voltage average value Vav. . Further, as shown in FIG. 7B, the average value of the peak voltage Vp becomes the peak voltage average value Vpa.

The arc length control of pulse arc welding is performed as follows. That is, since the average arc length and the above-mentioned welding voltage average value Vav or peak voltage average value Vpa are in a substantially proportional relationship, the arc length during welding should be detected by the welding voltage average value Vav or peak voltage average value Vpa. You can Then, the welding current average value Iav is changed by changing at least one of the pulse period Tf, the peak period Tp, the peak current Ip, or the base current Ib so that these detected values become substantially equal to the target value. ,
The arc length is controlled to an appropriate value by changing the melting rate. Therefore, in the conventional arc length control method, it is a prerequisite for good arc length control that the arc length is accurately detected by the welding voltage average value Vav or the peak voltage average value Vpa. Therefore, if an error occurs in the detection of the arc length, the arc length cannot be precisely controlled.

[0008]

As described above, in the prior art, the welding voltage Vw is detected, and the welding voltage detection value Vd is input to calculate the welding voltage average value Vav or the peak voltage average value Vpa, Detect the arc length. However, as will be described later, various arc phenomena that become disturbances occur randomly during welding, and an abnormal voltage may be superimposed on the welding voltage Vw due to these arc phenomena. Originally, this abnormal voltage is a voltage that has nothing to do with the arc length.
The arc length cannot be accurately detected depending on w. If the arc length is erroneously detected in this way, the arc length cannot be maintained at an appropriate value, and the arc length will fluctuate significantly during welding, which is important for welding such as penetration depth and bead appearance. The quality is poor. Generally, the generation of the abnormal voltage is more remarkable as the shield gas contains less oxidizing components. Therefore, in pulse MIG welding using a shield gas containing an inert gas such as argon gas or helium gas as a main component, an abnormal voltage is frequently generated, and the adverse effect of erroneous detection of the arc length becomes large. Less than,
Three typical examples of abnormal voltage generation in pulsed MIG welding of aluminum alloys will be described.

Abnormal Voltage Due to Cathode Spot Formation Immediately after Opening of Short Circuit FIG. 2 is a voltage / current waveform diagram when a minute short circuit occurs during the base period, and FIG. 2 (A) shows a temporal change of the welding voltage Vw. The same figure (B) shows the time change of the welding current Iw. Hereinafter, description will be given with reference to FIG. As previously mentioned,
In the pulse arc welding, the peak period is set so that one pulse and one droplet are transferred by energizing the peak current once. Therefore, as shown in the figure, the droplet transfer is often performed immediately after the end of the peak period (time t1). At the time of this droplet transfer, the droplet at the tip of the welding wire and the base material may come into contact with each other for a short time (hereinafter referred to as a micro short circuit). As shown in (A) of the figure, when a short circuit occurs at time t2 and the short circuit is released at time t3 after a short time, the time from the time t3 to t4 immediately after that is more than the normal value indicated by the dotted line. May have a large abnormal voltage. The reason for this is that the short circuit at time t2 extinguishes the arc once and the arc is re-ignited at time t3.
During this re-ignition, the cathode spot is formed on the molten pool, which is the shortest distance directly below the welding wire. However, since the oxide film on the surface of the molten pool is usually already cleaned, the cathode spots will be formed in the part without the oxide film. For this reason, the cathode drop voltage value becomes a very large value, and is superimposed as an abnormal voltage. Since this cathode drop voltage value is not in proportion to the arc length, the arc length cannot be correctly detected depending on the welding voltage Vw on which the abnormal voltage is superimposed. Since the cathode drop voltage value is influenced by the cleaning state of the oxide film of the base material, the formation position of the cathode spots, etc., the value may be small and the generation period may be short. On the contrary, the value may be large and the generation period may be long. As shown in FIG. 3A, the abnormal voltage is generated not only during the base period but also during the peak period.
The arc length cannot be correctly detected even by the welding voltage average value and the peak voltage average value.

Abnormal Voltage Due to Long-Term Short-Circuit FIG. 3 is a voltage / current waveform diagram when a long-term short-circuit occurs during the base period. FIG. 3A shows the welding voltage Vw with time. B) shows the time change of the welding current Iw. Hereinafter, description will be given with reference to FIG. If the non-melting part at the tip of the welding wire short-circuits with the base metal due to the feed rate, droplet formation state, molten pool vibration, etc., several tens [ [ms] may be required for a long time. This long-term short circuit often occurs during the base period, but also during the peak period. When a long-term short circuit occurs during the period from time t1 to t2, as shown in FIG.
The welding voltage value Vw during this period is a very low abnormal voltage of about several [V]. When the short circuit is opened at time t2, an abnormal voltage similar to the above item is generated between times t2 and t3. Further, as shown in FIG.
During the long-term short-circuiting period of t2, as described above, in order to promote the fusing of the non-melted portion, it is usual to supply a base current having a value larger than the normal value. As shown in FIG. 7A, the abnormal voltage during the long-term short-circuiting period between times t1 and t2 is a value that is much lower than the normal value indicated by the dotted line, and is a value that is not related to the arc length. The arc length cannot be correctly detected depending on the welding voltage average value and the peak voltage average value including the abnormal voltage.

Abnormal voltage due to the movement of the cathode spot during the base period. FIG. 4 shows the voltage when the cathode spot moves during the base period.
It is a current waveform figure, the figure (A) shows the time change of welding voltage Vw, and the figure (B) shows the time change of welding current Iw. Hereinafter, description will be given with reference to FIG. As previously mentioned,
Since the base current value is as low as several tens of [A], the directivity of the arc is weakened, and the cathode spot during the base period easily moves in search of the oxide film. Then, when the cathode spot moves and is newly formed, the above-mentioned cathode drop voltage value varies depending on the state of the oxide film on the surface of the base material, so that the welding voltage V
There is a case where an abnormal voltage is superimposed on w. As shown in FIG. 9A, when the cathode spot moves during the period from time t1 to t2, the welding voltage value Vw during this period fluctuates and becomes an abnormal voltage. Since this abnormal voltage greatly fluctuates from the normal value indicated by the dotted line and is a value that is not related to the arc length, the arc length cannot be correctly detected depending on the welding voltage average value including this abnormal voltage. Can not.

As described above, when an abnormal voltage irrelevant to the arc length is generated due to various arc phenomena, the arc length is accurately determined depending on the welding voltage average value or peak voltage average value including the abnormal voltage. Cannot be detected.
For this reason, in the prior art, when abnormal voltage occurs, the arc length during welding fluctuates, and welding quality deteriorates. This phenomenon is remarkable in pulse MIG welding, but also occurs in pulse MAG welding. That is, it is a problem that occurs in all of the pulse arc welding.

Therefore, the present invention provides an arc length control method for pulse arc welding which can always maintain the arc length at an appropriate value by accurately detecting the arc length even if the above abnormal voltage occurs. To do.

[0014]

According to the invention of claim 1, during the peak rise period Tup, the base current Ib to the peak current I are increased.
The peak period Tp is maintained by continuously applying the transition current rising to p.
During the peak fall period Tdw, the peak current Ip continues to be supplied during the period, and the peak current Ip changes to the base current Ib during the peak falling period Tdw.
Is continuously applied to the base current Tb during the base period Tb, and these energizations are repeated as the pulse period Tf, and the average value Vav of the welding voltage is set to a predetermined voltage setting value. Arc length control for pulse arc welding in which at least one of the pulse period Tf, the peak period Tp, the peak current Ip, or the base current Ib is controlled to be substantially equal to Vs to maintain the arc length at an appropriate value. In the method, the welding voltage Vw
Is detected, the welding voltage limit value Vft is calculated by limiting the welding voltage detection value Vd to the predetermined fluctuation range Vc ± ΔVc with the predetermined reference voltage waveform as the center voltage value Vc, and the welding voltage limit value Vft is calculated. The arc length control method for pulse arc welding is characterized in that the welding voltage average value Vav is calculated by inputting the voltage limit value Vft.

According to a second aspect of the present invention, at the start of the n-th pulse period Tf (n), the welding voltage limit value Vft only during the peak period Tp is moving averaged over a predetermined period in the past to obtain a peak voltage moving average value. Vpr is calculated and the base period T
The base voltage moving average value Vbr is calculated by moving average the welding voltage limit value Vft only during b over the past predetermined period, and the peak voltage moving average value is calculated from the base voltage moving average value Vbr during the peak rising period Tup. The transition voltage rises to Vpr, and the peak voltage moving average value Vbr continues during the subsequent peak period Tp, and the peak voltage moving average value Vpr changes from the base voltage moving average value Vbr during the subsequent peak falling period Tdw. 2. The arc length control method for pulse arc welding according to claim 1, wherein a reference voltage waveform having the falling transition voltage and the base voltage moving average value Vbr during the subsequent base period Tb is calculated.

According to the invention of claim 3, the peak rising period Tup
The peak current Ip continues to be supplied during the peak period Tp while the transition current rising from the base current Ib to the peak current Ip continues to be supplied during the peak fall period Tdw. The base current Ib is supplied during the base period Tb, and these supply currents are repeated as the pulse period Tf, and the average value Vpa of the peak voltage during the peak period Tp is The pulse period Tf or the peak period T is set so as to be substantially equal to the predetermined voltage set value Vs.
In the arc length control method of pulse arc welding, which controls at least one of p or the peak current Ip or the base current Ib to maintain the arc length at an appropriate value, the peak voltage Vp is detected, and the peak voltage detection value is detected. A peak voltage limit value Vpf is calculated by limiting Vpd as an input within a predetermined fluctuation range Vpc ± ΔVc with a predetermined reference peak voltage value Vpc as a center value, and the peak voltage limit value Vpf is input as the above peak. An arc length control method for pulse arc welding, which is characterized in that a voltage average value Vpa is calculated.

According to a fourth aspect of the invention, at the start of the n-th pulse period Tf (n), the peak voltage limit value Vpf is moving averaged over a predetermined period in the past to obtain a peak voltage moving average value Tpr.
Is calculated and this peak voltage moving average value Tpr is set as a reference peak voltage value Vpc. 4. The arc length control method for pulse arc welding according to claim 3, wherein

According to the invention of claim 5, the peak rising period Tup
Inside is the electrode plus polarity and the base current Ib to the peak current I
The peak period Tp is maintained by continuously applying the transition current rising to p.
In the middle, the peak current Ip is continuously supplied with the electrode positive polarity, and during the peak falling period Tdw, the transition current descending from the peak current Ip to the base current Ib is continuously supplied with the electrode positive polarity and the electrode negative period Ten is continued. Inside is the negative polarity of the electrode and the negative current of the electrode is continuously applied to the base period T
In b, the base current Ib is applied with the electrode plus polarity,
These energizations are repeatedly energized as the pulse period Tf, and the pulse period Tf or the peak period Tp or the peak is set so that the average value Vav of the absolute values of the welding voltage Vw becomes substantially equal to the predetermined voltage set value Vs. Current Ip
Alternatively, in the arc length control method of pulse arc welding in which at least one of the base currents Ib is controlled to maintain the arc length at an appropriate value, the welding voltage Vw is detected, and the welding voltage detection value Vd is set as an input and determined in advance. A predetermined fluctuation range Vc ± ΔV with the reference voltage waveform as the central voltage value Vc
Arc length control of pulse arc welding, characterized in that the welding voltage limit value Vft is calculated within a limit of c and the average value Vav of the absolute values of the welding voltage Vw is calculated by inputting the welding voltage limit value Vft. Is the way.

According to a sixth aspect of the invention, at the start of the nth pulse period Tf (n), the welding voltage limit value Vft only during the peak period Tp is moving averaged over a predetermined period in the past to obtain a peak voltage moving average value. Vpr is calculated and electrode minus period T
Electrode minus voltage moving average value Ver calculated by moving average the welding voltage limit value Vft only during en
Is calculated and the welding voltage limit value Vft only during the base period Tb is moving averaged over the past predetermined period to calculate a base voltage moving average value Vbr. During the peak rising period Tup, the base voltage moving average value Vbr is calculated. The transition voltage rises to the peak voltage moving average value Vpr, the peak voltage moving average value Vpr during the subsequent peak period Tp, and the base voltage from the peak voltage moving average value Vpr during the subsequent peak falling period Tdw. A reference voltage waveform is calculated that has a transition voltage that drops to the moving average value Vbr, the electrode minus voltage moving average value Ver during the subsequent electrode negative period Ten, and the base voltage moving average value Vbr during the subsequent base period Tb. The arc length control method for pulse arc welding according to claim 5, wherein

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. Example 1 The arc length slightly changes by the difference between the welding wire feed amount and the melting amount for each pulse period. Therefore, the voltage value that rapidly changes during the pulse period like the abnormal voltage described above with reference to FIGS. 2 to 4 is a voltage that is not proportional to the arc length. The fluctuation range of the voltage value proportional to the arc length during the pulse period is about several [V] from the reference voltage values of the peak voltage value Vp and the base voltage value Vb. That is,
Of the welding voltage Vw, only the voltage value within the fluctuation range of about several [V] from the reference voltage value is substantially proportional to the arc length, and the voltage value outside this fluctuation range is not proportional to the arc length. Abnormal voltage. Therefore, in the invention of the first embodiment, the reference voltage waveform is set in advance, the welding voltage Vw is detected,
A predetermined fluctuation range Vc ± Δ in which the welding voltage detection value Vd is input and the above-mentioned reference voltage waveform is used as the center voltage value Vc
The welding voltage limit value Vft is calculated by limiting it to Vc, and the welding voltage average value Vav is calculated by using this welding voltage limit value Vft as an input. Then, at least one of the pulse period, the peak period, the peak current or the base current is controlled so that the welding voltage average value Vav based on the welding voltage limit value Vft becomes substantially equal to the voltage setting value Vs, and the arc length is controlled. Is maintained at an appropriate value.

FIG. 5 is a diagram showing a method of setting the above-mentioned reference voltage waveform. First, the reference peak voltage value Vpc, the reference base voltage value Vbc, and the variation range ΔVc are set in advance by experiments or the like according to the welding conditions such as the type of welding wire and the feeding speed. Then, as shown in the figure, the reference voltage waveform is defined by the following expression by the elapsed time t when the start time of the peak rising period Tup is 0 [s]. 0 ≦ t <Tup Vc = ((Vpc−Vbc) / Tup) · t + Vbc (11) Formula Tup ≦ t <Tup + Tp Vc = Vpc (12) Formula Tup + Tp ≦ t <Tup + Tp + Tdw Vc = ((Vbc−Vpc) / Tdw) -(T-Tup-Tp) + Vpc (13) Formula Tup + Tp + Tdw≤t <Tup + Tp + Tdw + Tb Vc = Vbc (14) Formula

In the above equation, for example, as shown in the figure, the welding voltage detection value at the elapsed time ta is Vd1 [V].
It was. The elapsed time ta is Tup + Tp ≦ ta <
Since it is Tup + Tp + Tdw, the center voltage value Vc1 [V] of the reference voltage waveform is as follows by substituting it in the above equation (13). Vc1 = ((Vbc-Vpc) / Tdw) * (ta-Tup-T
p) + Vpc Therefore, the welding voltage detection value Vd1 at the elapsed time ta
Is limited to within the fluctuation range Vc1 ± ΔVc. That is,
When Vd1 ≧ Vc1 + ΔVc, Vd1 = Vc + ΔVc is limited, and when Vd1 ≦ Vc1−ΔVc, Vd1 = Vc−Δ
Limited to Vc. With the welding voltage limit value Vft calculated in this way as an input, the welding voltage average value Vav is calculated.

FIG. 6 is a voltage diagram when an abnormal voltage is generated due to the formation of cathode spots immediately after the short circuit is opened as described above with reference to FIG. The figure (A) shows the time change of the welding voltage Vw, and the figure (B) shows the time change of the welding voltage limit value Vft. As shown in FIG. 7B, the welding voltage Vw is the reference voltage waveform with the center voltage value V
It is limited within the fluctuation range Vc ± ΔVc. As a result, the welding voltage limit value Vft during the short circuit period from time t2 to time t3
= Vc-ΔVc, and the welding voltage limit value Vft = Vc + ΔVc during the abnormal voltage generation period from time t3 to t4. In this way, the influence of the abnormal voltage can be reduced, so that stable arc length control is possible. Further, also in the case of FIGS. 3 to 4 described above, similarly, the influence of the abnormal voltage can be reduced.

FIG. 7 is a block diagram of a welding power supply device PS for carrying out the invention of the first embodiment described above. Less than,
Each circuit block will be described with reference to FIG. The output control circuit INV receives a commercial AC power supply three-phase 200 [V] and the like as input, performs output control such as inverter control and thyristor phase control according to a current error amplification signal Ei described later, and a welding voltage Vw and a welding voltage suitable for welding. The welding current Iw is output. The welding wire 1 is fed by the feeding roll 5 through the welding torch 4, and an arc 3 is generated between the welding wire 1 and the base material 2 to perform welding.

The voltage detection circuit VD detects the welding voltage Vw and outputs a welding voltage detection signal Vd. The reference voltage waveform storage circuit VC stores the reference voltage waveform defined by the above equations (11) to (14), and outputs a center voltage value signal Vc corresponding to an elapsed time signal St described later. The fluctuation range setting circuit ΔVC outputs a predetermined fluctuation range signal ΔVc. The limiting filter circuit FT receives the above-mentioned welding voltage detection signal Vd as an input and changes the range V from the above-mentioned center voltage value.
The welding voltage limit value signal Vft is output while limiting to within c ± ΔVc. The average value calculation circuit VAV inputs the above-mentioned welding voltage limit value signal Vft, calculates an average value, and outputs a welding voltage average value signal Vav.

The voltage setting circuit VS outputs a predetermined voltage setting signal Vs. The voltage error amplification circuit EV amplifies the error between the welding voltage average value signal Vav and the voltage setting signal Vs, and outputs a voltage error amplification signal Ev. The voltage / frequency conversion circuit V / F converts the voltage error amplification signal Ev into a frequency that is proportional to the value of the voltage error amplification signal Ev, and outputs a pulse cycle signal Tf that becomes High level for a short time at each frequency (pulse cycle). The elapsed time counting circuit ST counts the elapsed time from the time when the pulse period signal Tf changes to the High level (the start time of the peak rising period),
The elapsed time signal St is output.

The peak current setting circuit IPS outputs a predetermined peak current setting signal Ips. The base current setting circuit IBS outputs a predetermined base current setting signal Ibs. The current control setting circuit ISC receives the elapsed time signal St as an input and outputs a current control setting signal Isc that rises from the base current setting signal Ibs to the peak current setting signal Ips during the peak rising period, During the subsequent peak period Tp, the peak current setting signal Ips is output as the current control setting signal Isc, and during the subsequent peak falling period Tdw, the peak current setting signal Ips is changed to the base current setting signal Ibs. The falling current control setting signal Isc is output, and during the subsequent base period Tb, the base current setting signal Ibs is output as the current control setting signal Isc. The current detection circuit ID detects the welding current Iw,
The current detection signal Id is output. Current error amplifier circuit EI
Outputs the current error amplification signal Ei by amplifying the error between the current control setting signal Isc and the current detection signal Id.
As a result, the welding current Iw corresponding to the current control setting signal Isc is applied.

The welding power source device PS described above limits the welding voltage Vw within the fluctuation range Vc ± ΔVc with the reference voltage waveform as the center voltage value Vc to calculate the welding voltage limit value signal Vft. The average value signal Vav is calculated. Then, the pulse period signal Tf is controlled so that the welding voltage average value signal Vav becomes substantially equal to the voltage setting signal Vs. Further, the peak period, the peak current or the base current may be controlled based on the voltage error amplification signal Ev so that the welding voltage average value signal Vav and the voltage setting signal Vs are substantially equal to each other.

In the above, the variation range is Vc ± ΔVc
However, the plus side range + ΔVc1 and the minus side range −ΔVc2 may be set to different values. Variation range Δ
As an example of the value of Vc, the pulse M of aluminum alloy is shown.
In IG welding, ΔVc = 1.5 [V] or so, and in pulse MAG welding of steel, ΔVc = 2 [V] or so.

[Embodiment 2] The invention of embodiment 2 is to automatically calculate the reference voltage waveform during welding in the invention of embodiment 1 described above, and the calculation method will be described below. FIG. 8 is a diagram showing a temporal change of the welding voltage limit value Vft for explaining the method of calculating the reference voltage waveform.
In the figure, the current time is time tn, which is the start time of the n-th pulse cycle Tf (n). Further, the average value of the welding voltage limit value only in the peak period in the (n-1) th pulse period Tf (n-1) is the peak voltage limit value Vpf (n-1), and the welding voltage limit value only in the base period. Is the base voltage limit value Vbf (n-1). Similarly, the average value of the welding voltage limit value only in the peak period in the (n−m) th pulse period Tf (nm) is the peak voltage limit value Vpf (nm), and the average value of the welding voltage limit value only in the base period. Is the base voltage limit value Vbf (nm).

At time tn, the above (n-1) to (n)
The peak voltage moving average value Vpr (n) is calculated according to the following equation by inputting the -m) th peak voltage limit value Vpf. Vpr (n) = (Vpf (n-1) + ... + Vpf (nm)) / m (21) Similarly, at the time tn, the above (n-1) to (nm).
The base voltage moving average value Vbr (n) is calculated according to the following equation by inputting the base voltage limit value Vbf for the second time. Vbr (n) = (Vbf (n-1) + ... + Vbf (nm)) / m (22) Formula

In the above equations (11) to (14), the peak voltage moving average value Vpr is substituted for the reference peak voltage value Vpc, and the base voltage moving average value is set for the reference base voltage value Vbc. By substituting Vbr, the reference voltage waveform in the nth pulse period Tf (n) is defined by the following equation. 0 ≦ t <Tup Vc (n) = ((Vpr (n) −Vbr (n)) / Tup) · t + Vbr (n) (31) Formula Tup ≦ t <Tup + Tp Vc (n) = Vpr (n) (32 ) Formula Tup + Tp ≦ t <Tup + Tp + Tdw Vc (n) = ((Vbr (n) −Vpr (n)) / Tdw) · (t−Tup−Tp) + Vpr (n) (33) Formula Tup + Tp + Tdw ≦ t <Tup + Tp + Tdw + Tb Vc (t) n) = Vbr (n) Equation (34)

As described above, the peak voltage moving average value Vpr and the base voltage moving average value Vbr are calculated at each start point of the pulse period, and the reference voltage waveform is calculated by the equations (31) to (34). It is set automatically. Other than this behavior,
Since it is the same as the invention of the first embodiment described above, its explanation is omitted.

In the above, the peak voltage moving average value Vpr
When calculating, the peak voltage limit value Vpf may be calculated by weighted moving average. Similarly, when calculating the base voltage moving average value Vbr, the base voltage limit value Vbf may be calculated by weighted moving average. The length of the period for moving average is set to the past several cycles to several tens of cycles.

FIG. 9 is a block diagram of a welding power source device PS for carrying out the invention of the second embodiment described above. In the figure, the same circuit blocks as those in FIG. 7 described above are designated by the same reference numerals, and the description thereof will be omitted. Hereinafter, a circuit block indicated by a dotted line different from that of FIG. 7 will be described with reference to FIG. The moving average value calculating circuit VRA receives the welding voltage limit value signal Vft and the elapsed time signal St as inputs, and performs the calculations of the above equations (21) and (22) to obtain the peak voltage moving average value signal Vpr and the base voltage moving average. The value signal Vbr is output. The second reference voltage waveform storage circuit VC2 receives the peak voltage moving average value signal Vpr, the base voltage moving average value signal Vbr, and the elapsed time signal St described above, and defines them by the above equations (31) to (34). The reference voltage waveform is stored and the central voltage value signal Vc corresponding to the elapsed time signal St is output.

[Embodiment 3] In the invention of Embodiment 3, the peak voltage Vp is detected, and the fluctuation range Vpc with the reference peak voltage value Vpc as the center value by inputting this peak voltage detection value Vpd.
The peak voltage limit value Vpf is calculated by limiting within ± ΔVc,
The peak voltage average value Vpa is calculated by inputting the peak voltage limit value Vpf. Then, this peak voltage average value Vpa
Pulse period, so as to be substantially equal to the voltage setting value Vs,
At least one of peak period, peak current or base current
One or more are controlled to maintain the arc length at an appropriate value. The reference peak voltage value Vpc and the fluctuation range ΔVc are preset to appropriate values according to welding conditions such as the type of welding wire and the feeding speed.

FIG. 10 is a block diagram of a welding power supply device PS for carrying out the invention of the third embodiment. In the figure, the same circuit blocks as those in FIG. 7 described above are designated by the same reference numerals, and the description thereof will be omitted. Hereinafter, a circuit block indicated by a dotted line different from that of FIG. 7 will be described with reference to FIG.

The peak voltage detection circuit VPD detects the welding voltage Vw during the peak period and outputs the peak voltage detection signal Vpd.
Is output. The reference peak voltage setting circuit VPC outputs a predetermined reference peak voltage value signal Vpc. The peak voltage limiting filter circuit VPF receives the peak voltage detection signal Vpd as an input and limits it within a variation range Vpc ± ΔVc centered on the reference peak voltage value signal Vpc to obtain a peak voltage limiting value signal Vpf. Output. The peak voltage average value calculation circuit VPA receives the above-mentioned peak voltage limit value signal Vpf as an input to calculate an average value, and calculates the peak voltage average value signal Vpa.
Is output.

[Embodiment 4] The invention of the embodiment 4 is such that, in the invention of the embodiment 3, the reference peak voltage value Vpc is automatically calculated during welding. This calculation method uses the peak voltage limit value Vpf as an input, calculates the peak voltage moving average value Vpr by the above equation (21), and sets this as the reference peak voltage value Vpc, as in the case of FIG. 8 described above.

FIG. 11 is a block diagram of a welding power source device PS for carrying out the invention of the fourth embodiment. In the figure, the same circuit blocks as those in FIG. 10 described above are designated by the same reference numerals, and their description will be omitted. Hereinafter, a circuit block indicated by a dotted line different from that of FIG. 10 will be described with reference to FIG.

The peak voltage moving average value calculating circuit VPR is
Using the peak voltage limit value signal Vpf and the elapsed time signal St as input, the calculation of the above equation (21) is performed and the peak voltage moving average value signal Vpr is output. The second reference peak voltage setting circuit VPC2 outputs the above peak voltage moving average value signal Vpr as a reference peak voltage value signal Vpc.

[Embodiment 5] The invention of Embodiment 5 is an application of the invention of Embodiment 1 described above to an AC pulse arc welding method. The consumable electrode type AC pulse arc welding method is a welding method in which the polarity of the voltage applied to the consumable electrode (welding wire) in the output waveform described above with reference to FIG. . Specifically, between the peak falling period Tdw and the base period Tb of FIG.
An electrode minus period Ten reversed to the electrode minus polarity is inserted, and an electrode minus current is supplied during this period. In addition to the above, the case where the electrode minus period Ten is inserted between the base period Tb and the peak rise period Tup, or a part of the middle period of the base period Tb is set as the electrode minus period Ten is conventionally used. is there. Although the invention according to claim 5 or 6 includes all of the above three cases, the following description will exemplify the above first case.

FIG. 12 is a diagram showing a method of setting the reference voltage waveform in the fifth embodiment. First, the type of welding wire,
Depending on welding conditions such as feed rate, the standard peak voltage value Vp
c, reference base voltage value Vbc, reference electrode negative voltage value Ve
c and the variation range ΔVc are set in advance by experiments or the like. Then, as shown in FIG.
The reference voltage waveform is defined by the following equation by the elapsed time t when the start time of is 0 [s]. 0 ≦ t <Tup Vc = ((Vpc−Vbc) / Tup) · t + Vbc (411) Formula Tup ≦ t <Tup + Tp Vc = Vpc (42) Formula Tup + Tp ≦ t <Tup + Tp + Tdw Vc = ((Vbc−Vpc) / Tdw) -(T-Tup-Tp) + Vpc (43) Formula Tup + Tp + Tdw≤t <Tup + Tp + Tdw + Ten Vc = Vec (44) Formula Tup + Tp + Tdw + Ten≤t <Tup + Tp + Tdw + Ten + Tb Vc = Vbc (45) Formula

For example, as shown in the figure, the elapsed time ta2
It is assumed that the welding voltage detection value at is Vd2 [V].
The elapsed time ta2 is Tup + Tp + Tdw ≦ ta2 <Tup + Tp
Since it is + Tdw + Ten, the center voltage value Vc2 [V] = Vec of the reference voltage waveform is obtained by substituting it into the equation (44). Therefore, in the invention of the fifth embodiment, the welding voltage detection value Vd2 at the elapsed time ta2 is limited within the fluctuation range Vc2 ± ΔVc. That is, when Vd2 ≧ Vc2 + ΔVc, Vd2 = Vc2 + ΔVc is limited, and when Vd2 ≦ Vc2-ΔVc, Vd2 = Vc2-ΔVc is limited. The welding voltage limit value Vft calculated in this manner is input, and since it is an AC output, the welding voltage average value Vav is calculated by averaging its absolute values.

FIG. 13 is a voltage waveform diagram when an abnormal voltage is generated during the negative electrode period in AC pulse arc welding. The figure (A) shows the time change of the welding voltage Vw, and the figure (B) shows the time change of the welding voltage limit value Vft. As shown in FIG. 3B, the welding voltage Vw is limited within the fluctuation range Vc ± ΔVc with the reference voltage waveform as the center voltage value Vc. As a result, the welding voltage limit value Vft = Vc−ΔVc = Vec−ΔV during the abnormal voltage generation period from time t1 to t2
c. In this way, the influence of the abnormal voltage can be reduced, so that stable arc length control is possible.

FIG. 14 is a block diagram of a welding power source device PS for carrying out the invention of the fifth embodiment described above. Hereinafter, each circuit block will be described with reference to FIG. The second output control circuit INV2 is a commercial AC power supply 3-phase 2
00 [V] or the like as an input, output control by inverter control or the like is performed in accordance with a current error amplification signal Ei described later to generate a DC voltage suitable for an arc load, and the secondary side inverter circuit is operated by the secondary side inverter circuit in accordance with a polarity switching signal Sp described later. The DC voltage is converted into an AC voltage and an AC welding voltage Vw and a welding current Iw are output. The polarity switching signal Sp is Hi.
The output of the welding power source device has an electrode positive polarity at the gh level, and has an electrode negative polarity at the low level. The welding wire 1 is fed by the feeding roll 5 through the welding torch 4 and the arc 3 with the base material 2.
Occurs and welding is performed.

The second voltage detection circuit VD2 detects an AC welding voltage Vw and outputs an AC welding voltage detection signal Vd. The third reference voltage waveform storage circuit VC3 stores the reference voltage waveform defined by the above equations (41) to (45),
A central voltage value signal V corresponding to an elapsed time signal St described later.
Output c. The fluctuation range setting circuit ΔVC outputs a predetermined fluctuation range signal ΔVc. Limiting filter circuit FT
Is the input of the welding voltage detection signal Vd and is limited within the fluctuation range Vc ± ΔVc from the center voltage value,
The welding voltage limit value signal Vft is output. The second average value calculation circuit VA2 receives the above welding voltage limit value signal Vft, averages the absolute values, and outputs a welding voltage average value signal Vav.

The voltage setting circuit VS outputs a predetermined voltage setting signal Vs. The voltage error amplification circuit EV amplifies the error between the welding voltage average value signal Vav and the voltage setting signal Vs, and outputs a voltage error amplification signal Ev. The voltage / frequency conversion circuit V / F converts the voltage error amplification signal Ev into a frequency that is proportional to the value of the voltage error amplification signal Ev, and outputs a pulse cycle signal Tf that becomes High level for a short time at each frequency (pulse cycle). The elapsed time counting circuit ST counts the elapsed time from the time when the pulse period signal Tf changes to the High level (the start time of the peak rising period),
The elapsed time signal St is output.

The peak current setting circuit IPS outputs a predetermined peak current setting signal Ips. The base current setting circuit IBS outputs a predetermined base current setting signal Ibs. The electrode negative current setting circuit IES outputs a predetermined electrode negative current setting signal Ies. The second current control setting circuit ISC2 inputs the elapsed time signal St and outputs the current control setting signal Isc that rises from the base current setting signal Ibs to the peak current setting signal Ips during the peak rising period. And then the peak period T
During p, the peak current setting signal Ips is output as the current control setting signal Isc, and during the subsequent peak falling period Tdw, the peak current setting signal Ips is lowered to the base current setting signal Ibs. The setting signal Isc is output, the electrode minus current setting signal Ies is output as the current control setting signal Isc during the subsequent electrode minus period Ten, and the base current setting signal Ibs is current controlled during the subsequent base period Tb. It is output as the setting signal Isc. The second current detection circuit ID2 detects the AC welding current Iw, obtains its absolute value, and outputs the current detection signal Id.
The current error amplifier circuit EI has the above current control setting signal Isc.
And the current detection signal Id is amplified, and the current error amplification signal Ei is output. As a result, the welding current Iw corresponding to the current control setting signal Isc is applied. The polarity switching signal generation circuit SP receives the above-described elapsed time signal St as an input and outputs the polarity switching signal Sp that is at the Low level only during the electrode minus period.

The welding power source device PS described above limits the welding voltage Vw within the fluctuation range Vc ± ΔVc with the reference voltage waveform as the center voltage value Vc to calculate the welding voltage limit value signal Vft. From this signal, the welding voltage limit value signal Vft is calculated. The average value signal Vav is calculated. Then, the pulse period signal Tf is controlled so that the welding voltage average value signal Vav becomes substantially equal to the voltage setting signal Vs. Further, the peak period, the peak current or the base current may be controlled based on the voltage error amplification signal Ev so that the welding voltage average value signal Vav and the voltage setting signal Vs are substantially equal to each other.

[Embodiment 6] In the invention of Embodiment 6, the reference voltage waveform is automatically calculated during welding in the invention of Embodiment 5 described above, and the calculation method will be described below. FIG. 15 is a diagram showing a temporal change of the welding voltage limit value Vft for explaining the method of calculating the reference voltage waveform. In the figure, the current time is time tn, which is the start time of the n-th pulse cycle Tf (n). Also, the n-th
The average value of the welding voltage limiting value only during the peak period in the first pulse period Tf (n-1) is the peak voltage limiting value Vpf (n-
1), the average value of the welding voltage limit value only during the base period is the base voltage limit value Vbf (n-1), and the average value of the welding voltage limit value only during the electrode negative period is the electrode negative voltage limit value Vef ( n-1). Similarly, the average value of the welding voltage limit value only in the peak period in the (n−m) th pulse period Tf (nm) is the peak voltage limit value Vpf (nm), and the average value of the welding voltage limit value only in the base period. Is the base voltage limit value Vbf (nm), and the average of the welding voltage limit values only during the electrode negative period is the electrode negative voltage limit value Vef (nm).

At time tn, the above (n-1) to (n)
The peak voltage moving average value Vpr (n) is calculated according to the following equation by inputting the -m) th peak voltage limit value Vpf. Vpr (n) = (Vpf (n-1) + ... + Vpf (nm)) / m (51) Similarly, at time tn, the above (n-1) to (nm)
The base voltage moving average value Vbr (n) is calculated according to the following equation by inputting the base voltage limit value Vbf for the second time. Vbr (n) = (Vbf (n-1) + ... + Vbf (nm)) / m Expression (52) Similarly, at time tn, the above (n-1) -th
(nm) Input the negative voltage limit value Vef of the negative electrode and input the negative voltage moving average value Ver (n)
To calculate. Ver (n) = (Vef (n-1) + ... + Vef (nm)) / m (53) Formula

In the above equations (41) to (45), the peak voltage moving average value Vpr is substituted for the reference peak voltage value Vpc, and the base voltage moving average value is set for the reference base voltage value Vbc. Substituting Vbr and substituting the above-mentioned electrode minus voltage moving average value Ver into the reference electrode minus voltage value Vec, the reference voltage waveform in the n-th pulse period Tf (n) is defined by the following equation. It 0 ≦ t <Tup Vc (n) = ((Vpr (n) −Vbr (n)) / Tup) · t + Vbr (n) (61) Formula Tup ≦ t <Tup + Tp Vc (n) = Vpr (n) (62) ) Expression Tup + Tp ≦ t <Tup + Tp + Tdw Vc (n) = ((Vbr (n) −Vpr (n)) / Tdw) · (t−Tup−Tp) + Vpr (n) (63) Expression Tup + Tp + Tdw ≦ t <Tup + Tp + Tdw + TenVc (T) n) = Ver (n) (64) Formula Tup + Tp + Tdw + Ten ≦ t <Tup + Tp + Tdw + Ten + Tb Vc (n) = Vbr (n) (65) Formula

As described above, the peak voltage moving average value Vpr, the base voltage moving average value Vbr, and the electrode minus voltage moving average value Ver are calculated at each start point of the pulse period, and the equations (61) to () are calculated. The reference voltage waveform is automatically set by the equation (65). Other than this operation, it is the same as the invention of the fifth embodiment described above, and therefore the description thereof is omitted.

In the above, the peak voltage moving average value Vpr
When calculating, the peak voltage limit value Vpf may be calculated by weighted moving average. Similarly, when calculating the base voltage moving average value Vbr, the base voltage limit value Vbf may be calculated by weighted moving average, and when calculating the electrode minus voltage moving average value Ver, the electrode minus voltage limit value may be calculated. Vef may be calculated by weighted moving average. The length of the period for moving average is set to the past several cycles to several tens of cycles.

FIG. 16 is a block diagram of a welding power supply device PS for carrying out the invention of the above-described sixth embodiment. In the figure, the same circuit blocks as those in FIG. 14 described above are designated by the same reference numerals, and the description thereof will be omitted. Below, Figure 1
Circuit blocks indicated by dotted lines different from 4 will be described with reference to FIG.

The second moving average value calculating circuit VRA2 receives the welding voltage limit value signal Vft and the elapsed time signal St and performs the calculations of the above equations (51) to (53) to obtain the peak voltage moving average value signal Vpr. , A base voltage moving average value signal Vbr and an electrode minus voltage moving average value signal Ver. The fourth reference voltage waveform storage circuit VC4 includes the peak voltage moving average value signal Vpr, the base voltage moving average value signal Vbr, the electrode minus voltage moving average value signal Ver and the elapsed time signal S.
With t as an input, the reference voltage waveform defined by the equations (61) to (65) is stored, and the central voltage value signal Vc corresponding to the elapsed time signal St is output.

[Effects] The effects of the present invention will be described below with reference to the drawings. FIG. 17 is a diagram comparing the variation range of the arc length in pulse MIG welding of aluminum between the present invention and the prior art. In the figure, the welding wire is an aluminum wire with a diameter of 1.2 mm (JIS A40
43), pulse MIG welding was performed at a welding current of 150 [A], and the variation range of the arc length during welding from the target value was compared. As is clear from the figure, in the prior art, the variation range is 3 ± 1.5 [mm]. On the other hand, in the present invention, the variation range is 3 ±
The value is 0.3 [mm], which is greatly improved to ⅕ of the conventional technology. This is because the present invention can suppress the influence of the abnormal voltage on the arc length control.

FIG. 18 is a diagram comparing the amount of spatter generated in pulse MAG welding of steel with the present invention and the prior art. In the figure, a mild steel wire having a diameter of 1.2 [mm] is used as the welding wire, pulse MAG welding is performed at a welding current of 150 [A], and the amount of spatter generated during welding is compared. As is clear from the figure, in the conventional technique, the generation amount is 1.8 [g / min]. On the other hand, in the present invention, the amount of generation is 0.3 [g / min], which is greatly improved to 1/6 of that of the conventional technique. This is because, in the conventional technique, the welding state becomes unstable due to the variation of the arc length caused by the abnormal voltage and a lot of spatters occur, but in the present invention, the variation of the arc length caused by the abnormal voltage can be suppressed. Therefore, the amount of spatter generated can be reduced.

[0060]

According to the present invention, in pulse arc welding, the influence of abnormal voltage is suppressed by limiting the welding voltage detection value or the peak voltage detection value to within the fluctuation range with the reference voltage waveform as the center voltage value. Therefore, the variation of the arc length is reduced, and good welding quality can always be obtained. In addition to the above effects, the reference voltage waveform can be automatically calculated during welding, so the reference voltage waveform is always appropriate according to various welding conditions. Set to the value. For this reason, it is not necessary to preset the reference voltage waveform for each of various welding conditions by experiments or the like, and the working efficiency is improved.

[Brief description of drawings]

FIG. 1 is a current / voltage waveform diagram of prior art pulse arc welding.

FIG. 2 is an abnormal voltage waveform diagram associated with formation of cathode spots immediately after a short circuit is opened according to a conventional technique.

FIG. 3 is an abnormal voltage waveform diagram associated with a long-term short circuit according to the related art.

FIG. 4 is an abnormal voltage waveform diagram associated with cathode spot movement during a base period according to the related art.

FIG. 5 is a diagram showing a method of setting a reference voltage waveform according to the first embodiment of the invention.

FIG. 6 is a diagram showing a time change of the welding voltage limit value Vft corresponding to FIG. 2 in the invention of the first embodiment.

FIG. 7 is a block diagram of the welding power source device according to the first embodiment.

FIG. 8 is a diagram showing a method of calculating a reference voltage waveform according to the second embodiment of the invention.

FIG. 9 is a block diagram of a welding power supply device according to a second embodiment.

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

FIG. 11 is a block diagram of a welding power supply device according to a fourth embodiment.

FIG. 12 is a diagram showing a method of setting a reference voltage waveform according to the invention of Example 5;

FIG. 13 is a welding voltage limit value Vft in the invention of the fifth embodiment.
It is a figure which shows the time change of.

FIG. 14 is a block diagram of a welding power supply device according to a fifth embodiment.

FIG. 15 is a diagram showing a method of calculating a reference voltage waveform according to the sixth embodiment of the invention.

FIG. 16 is a block diagram of a welding power supply device according to a sixth embodiment.

FIG. 17 is a comparison diagram of the variation range of the arc length showing the effect of the present invention.

FIG. 18 is a spatter generation amount comparison diagram showing another effect of the present invention.

[Explanation of symbols]

1 welding wire 2 base material 3 arc 4 welding torch 5 feeding rolls EI current error amplifier circuit Ei Current error amplification signal EV voltage error amplifier circuit Ev voltage error amplification signal FT limit filter circuit Iav welding current average value (signal) IBS base current setting circuit Ibs Base current setting signal ID current detection circuit ID2 Second current detection circuit Id current detection signal IES Electrode negative current setting circuit Ies electrode negative current setting signal INV output control circuit INV2 second output control circuit IPS peak current setting circuit Ips peak current setting signal ISC current control setting circuit ISC2 second current control setting circuit Isc current control setting signal Iw welding current PS welding power supply SP polarity switching signal generation circuit Sp polarity switching signal ST Elapsed time counting circuit St elapsed time signal Tb base period Tdw peak falling period Ten electrode minus period Tf pulse period (signal) Tp peak period Tup peak rising period V / F voltage / frequency conversion circuit VAV average value calculation circuit VA2 second average value calculation circuit Vav Welding voltage average value (signal) Vb base voltage Vbc reference base voltage value Vbf Base voltage limit value Vbr Base voltage moving average value (signal) VC reference voltage waveform storage circuit Vc Reference voltage waveform center voltage value (signal) VC2 Second reference voltage waveform storage circuit VC3 Third reference voltage waveform storage circuit VC4 Fourth reference voltage waveform storage circuit VD voltage detection circuit VD2 second voltage detection circuit Vd voltage detection signal Vec Reference electrode negative voltage value Vef Electrode negative voltage limit value Ver electrode negative voltage moving average value (signal) Vp peak voltage VPA peak voltage average value calculation circuit Vpa Peak voltage average value (signal) VPC reference peak voltage setting circuit Vpc reference peak voltage value (signal) VPC2 Second reference peak voltage setting circuit VPD peak voltage detection circuit Vpd peak voltage detection signal VPF Peak voltage limiting filter circuit Vpf peak voltage limit value (signal) VPR peak voltage moving average value calculation circuit Vpr Peak voltage moving average value (signal) VRA moving average value calculation circuit VRA2 second moving average value calculation circuit VS voltage setting circuit Vs voltage setting (value / signal) Vw welding voltage ΔVc fluctuation range (signal)

Claims (6)

[Claims] 1. A transition current rising from a base current to a peak current is continuously supplied during a peak rising period, the peak current is continuously supplied during a peak period, and the peak current is changed to the base during a peak falling period. While continuing to supply a transition current that drops to a current, the base current is supplied during the base period, and these supply currents are repeatedly supplied as a pulse cycle, and the average value of the welding voltage is substantially equal to a predetermined voltage setting value. In the arc length control method of pulse arc welding, which controls at least one of the pulse period, the peak period, the peak current, or the base current so as to maintain the arc length at an appropriate value, the welding voltage is detected. , The welding voltage control is performed by limiting the welding voltage detection value as an input to a predetermined reference voltage waveform as a center voltage value within a predetermined fluctuation range. It calculates the value, the arc length control method for a pulse arc welding and calculates the welding voltage average value as inputs the welding voltage limit value. 2. At the start of the n-th pulse cycle, the welding voltage limit value only during the peak period is moving averaged over a predetermined period in the past to calculate a peak voltage moving average value, and at the same time only during the base period. A moving voltage average of the welding voltage limit value is calculated over the past predetermined period to calculate a base voltage moving average value, and during the peak rising period, a transition voltage which rises from the base voltage moving average value to the peak voltage moving average value is followed by the transition voltage. It becomes the peak voltage moving average value during the peak period, and becomes the transition voltage that drops from the peak voltage moving average value to the base voltage moving average value during the subsequent peak falling period, and becomes the base voltage during the following base period. The arc length control method for pulse arc welding according to claim 1, wherein a reference voltage waveform that is a moving average value is calculated. 3. A transition current rising from a base current to a peak current is continuously supplied during the peak rising period, the peak current is continuously supplied during the peak period, and the peak current is changed to the base during the peak falling period. While continuing to supply a transition current that drops to a current, the base current is supplied during the base period, and the supply of these currents is repeated as a pulse cycle, and the average value of the peak voltage during the peak period is a predetermined voltage. In an arc length control method for pulse arc welding, which controls at least one or more of the pulse period, the peak period, the peak current, or the base current so as to be substantially equal to a set value to maintain the arc length at an appropriate value. The peak voltage is detected and the detected peak voltage is used as an input for a predetermined variation range centered on a predetermined reference peak voltage value. Limited to calculate the peak voltage limit value, the arc length control method for a pulse arc welding, characterized in that to calculate the peak voltage average value as inputs the peak voltage limit value within. 4. At the start of the n-th pulse cycle, the peak voltage moving average value is calculated by moving average of the peak voltage limit values over a predetermined period in the past, and this peak voltage moving average value is used as a reference peak voltage value. The arc length control method for pulse arc welding according to claim 3, wherein the method is set. 5. During the peak rising period, the transition current that rises from the base current to the peak current is continuously supplied with the electrode positive polarity, and during the peak period, the peak current is continuously supplied with the electrode positive polarity and the peak falling period is obtained. Inside is an electrode positive polarity, and the transition current that drops from the peak current to the base current is continuously supplied, and during the electrode negative period, electrode negative polarity is continuously supplied and an electrode negative current is continuously supplied. The base current is energized, and these energizations are repeatedly energized as a pulse cycle, and the pulse cycle or the peak period or the peak is set so that the average value of the absolute value of the welding voltage becomes substantially equal to a predetermined voltage set value. Arc length control method of pulse arc welding for controlling the current or at least one of the base currents to maintain the arc length at an appropriate value Method, the welding voltage is detected, and the welding voltage limit value is calculated by limiting the welding voltage detection value as an input within a predetermined fluctuation range with a predetermined reference voltage waveform as the center voltage value. An arc length control method for pulse arc welding, wherein an average value of the absolute values of the welding voltage is calculated by inputting a limit value. 6. At the start of the n-th pulse period, a welding voltage limit value only during the peak period is moving averaged over a predetermined period in the past to calculate a peak voltage moving average value, and only during the electrode minus period. A moving average of the welding voltage limit value is calculated over the past predetermined period to calculate an electrode negative voltage moving average value, and the welding voltage limit value only during the base period is moving averaged over the past predetermined period to obtain a base voltage moving average value. Calculated, during the peak rising period becomes a transition voltage rising from the base voltage moving average value to the peak voltage moving average value, and during the subsequent peak period, becomes the peak voltage moving average value, and during the following peak falling period. The transition voltage decreases from the peak voltage moving average value to the base voltage moving average value, and during the subsequent electrode minus period, the voltage is reduced. The arc length control method for pulse arc welding according to claim 5, wherein a reference voltage waveform that becomes a pole negative voltage moving average value and becomes the base voltage moving average value during the subsequent base period is calculated.