JP2001162373A - Method of controlling of arc length for consumable electrode gas shield arc welding and welding power source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constantly enable an assured welding quality of a welded work, which is unavailable by a conventional technology for a controlling method of an arc length in a consumable electrode gas shield arc welding due to an inevitable fluctuation in the arc length generated by such instable factors as a fluctuation in a cleaning width, an instant short circuiting caused by the shifting of a weld droplet, or the like. SOLUTION: In the method of controlling an arc length and the device, the values Iw of a welding current and the values Vw of a welding voltage repeatedly detected during the welding and a preliminarily set feeding speed set value Ws are inputted, the calculated value La of an arc length is outputted from a calculation circuit CL for the arc length, the calculated values are used as a feedback signal, and an output control of a welding power source device is executed by a feedback control with a preliminarily set value Ls of the arc length used as a target value, thus the arc length during the welding is kept at the target value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arc for consumable electrode gas shielded arc welding in which the welding quality of a workpiece is improved by feedback-controlling an arc length calculation value calculated by a plurality of arithmetic processes during welding. Related to length control method.

[0002]

2. Description of the Related Art In consumable electrode gas shielded arc welding, welding conditions that affect the welding quality of a workpiece include:
There are an apparent arc length (hereinafter simply referred to as an arc length), an average welding current value, a welding speed, a wire type, a shield gas type, and the like. The welding quality of the above-mentioned work piece is that the penetration is proper, there is no welding defect such as undercut, overlap, blow hole, etc., the bead appearance is good, and the spatter adheres to the work piece. Is small. The setting of the average welding current value is usually performed by setting a wire feed speed (hereinafter, simply referred to as a feed speed).

[0003] In welding, the setting of the average welding current value (feeding speed), welding speed, type of wire, type of shielding gas, and the like among the above welding conditions are determined by the material of the workpiece,
It can be set in advance according to the shape and the like. But,
Among the above welding conditions, the arc length is affected by arc phenomenon instability factors such as droplet transfer occurring during welding, irregular movement of a molten pool, and the like, when a welding wire is fed through a welding torch. It constantly changes rapidly due to mechanical instability factors such as fluctuations in the feeding speed due to frictional force and fluctuations in the distance between the tip and the workpiece due to hand shake of the welding operator. If the arc length changes during welding, poor welding quality such as poor penetration, occurrence of undercut, deterioration of bead appearance, and large amount of spatter adhered to the workpiece will occur. Therefore, in order to ensure good welding quality of the workpiece, the arc length must be adjusted in accordance with the above-mentioned instability factors such as arc phenomena and mechanical instability factors (hereinafter simply referred to as instability factors). It is necessary to control the arc length to always maintain an appropriate constant value.

In order to perform this arc length control, it is necessary to set an appropriate value of the arc length in advance as a target value and to detect the arc length as a feedback signal. However, it is difficult to directly detect the arc length. Therefore, usually, as an alternative to detecting the arc length, under certain conditions, the welding voltage value that is directly proportional to the arc length is detected,
Used as a feedback signal. That is, arc length control using a voltage set value corresponding to an appropriate arc length as a target value and a welding voltage detection value as a feedback signal is used as a conventional technique. By the arc length control according to the conventional technique, a change in the arc length due to the above-mentioned instability factor can be suppressed, and good welding quality of a workpiece can be obtained.

However, in the above-described arc length control, it is necessary to set a voltage set value corresponding to an appropriate arc length in order to obtain good welding quality. When a welding method such as pulse arc welding or direct current arc welding is selected in welding, an appropriate arc length can be regarded as a substantially constant value regardless of the welding conditions described above. For example, in pulse arc welding, an appropriate arc length may be considered to be about 3 [mm] regardless of the welding conditions described above. Further, in globule transfer welding of DC arc welding, an appropriate arc length may be regarded as about 2 [mm].

[0006] However, unlike the above, the voltage set value corresponding to the appropriate arc length is not uniquely determined when a welding method is selected, but is the above-mentioned average welding current value, welding speed, and wire setting value. A different value is obtained for each combination of various welding conditions such as the type and the type of shielding gas. For example,
In pulse arc welding of steel, the average welding current is 2
The voltage set value corresponding to an appropriate arc length of 3 [mm] at 00 [A] is 25 [V], and the average welding current value is 300 [V].
The voltage set value corresponding to the same appropriate arc length of 3 [mm] at [A] is 34 [V], which is a different value. Further, in pulse arc welding with an average welding current value of 200 [A], an appropriate arc length 3 when the workpiece is steel.
The voltage setting corresponding to [mm] is 25 [V], and the voltage setting corresponding to the same appropriate arc length of 3 [mm] when the workpiece is an aluminum alloy is 21 [V], which is different. Becomes As described above, in the conventional arc length control, setting the voltage set value to an appropriate value is a very troublesome operation based on a wealth of knowledge.

A technique that can easily and accurately perform the above-described complicated voltage setting to an appropriate value by automatically controlling the voltage is a conventional voltage setting automatic control described below. In this voltage setting automatic control, an average arc length in a steady state during welding (hereinafter, referred to as an average arc length) is calculated by a plurality of arithmetic processings.
The average arc length calculation value is used as a feedback signal, and the voltage set value is automatically set by feedback control using an appropriate arc length set value as a target value. Further, the output of the welding power supply device is controlled by the above-described conventional arc length control using the automatically set voltage set value as a target value and the welding voltage detection value as a feedback signal, and finally controlling the arc length. It is carried out. Hereinafter, the above-described conventional voltage setting automatic control will be described.

FIG. 1 is a schematic diagram of an arc generating section for explaining main terms used in the following description.
As shown in the figure, the welding wire 1 is fed by a feeding roll 5a of a wire feeding device, and is fed from a contact tip 4a attached to a tip portion of the welding torch 4. An arc 3 is generated between the wire tip 1a and the workpiece 2 to melt the wire tip 1a and the workpiece 2 to form a molten pool 2a. The welding wire 1 is fed at a preset feeding speed Wf [mm / s], and a welding current Iw [A] is supplied. The wire tip 1a is melted in a direction opposite to the wire feeding direction at a wire melting speed (hereinafter simply referred to as melting speed) Wm [mm / s] by the arc heat and the Joule heat of the wire protruding portion. At this time, the distance between the tip and the workpiece is Lw [mm], and the welding voltage value between the tip and the workpiece is Vw [V]. The apparent arc length is La [mm], and the arc voltage value is Va [V]. Further, the wire protrusion length is Lx [mm], and the wire protrusion voltage value is Vx
[V]. As is clear from the figure, Lw = La + L
x and Vw = Va + Vx.

The average arc length calculation method used in the above-described prior art voltage setting automatic control includes an average feed speed Wfa,
In this method, the average welding current value Iwa and the average welding voltage value Vwa are input, and a plurality of arithmetic processes are performed to calculate an average arc length calculation value Laa as a result. Hereinafter, details of each arithmetic processing will be described.

First, the average wire overhang length Lxa [mm] in the steady state is determined by an average feed speed Wfa [mm / s] by experiments.
And the average welding current value Iwa [A] as a variable. Lxa = (Wfa-k2 · Iwa ) / (k1 · Iwa 2) ... (1) where, k1 [1 / (s · A 2)] and k2 [mm / (s · A )] , the welding wire It is a constant determined by the diameter, material (mild steel, stainless steel, aluminum alloy, etc.) and type (solid wire, flux-cored wire, etc.). However, (1)
The precondition that the equation is satisfied is a steady state in which the transient change in the wire protrusion length Lx has converged, that is, the feeding speed Wf [mm / s] and the melting speed Wm [mm / s] are substantially equal. It is time. Therefore, the average wire protrusion length Lxa in the steady state is obtained by the calculation of the expression (1).

Second, the average wire protrusion voltage Vxa
[V] is represented by the following equation using the above average wire protrusion length Lxa [mm] and the average welding current value Iwa [A] as variables. Vxa = Rx · Lxa · Iwa (2) where Rx
[Ω / mm] is a resistance value per unit length of the welding wire, and is a constant determined by the diameter, material and type of the welding wire.

Third, the average arc voltage value Vaa [V]
Is expressed by the following equation using the average wire protrusion voltage value Vxa [V] and the average welding voltage value Vwa [V] as variables. Vaa = Vwa−Vxa (3)

Finally, the average arc length calculation value Laa [mm]
It is known from experiments that the average arc voltage value Vaa [V] and the average welding current value Iwa [A] can be expressed by the following equation. Laa = (Vaa−ac · Iwa) / (b + d · Iwa) (4) where a [V], b [V / mm], c [Ω] and d [Ω / m]
m] is a constant determined by the diameter, material and type of the welding wire, and the type of shielding gas.

As described above, the average feed speed Wfa, the average welding current value Iwa and the average welding voltage value Vwa are used as inputs.
By sequentially repeating the arithmetic processing shown in the equations (1) to (4), the average arc length calculation value Laa can be finally calculated. However, the prerequisite for satisfying the expression (1) is a steady state in which the feeding speed Wf and the melting speed Wm are substantially equal, and the wire protrusion length Lx hardly changes, as described above. Therefore, what can be calculated by the above-described conventional average arc length calculation method is the average arc length Laa. The steady state here includes a state in which the average arc length Laa gradually changes below a few [Hz].

FIG. 2 shows an average arc length calculation circuit CLA for implementing the above-described prior art average arc length calculation method.
FIG. 3 is a block diagram showing the configuration of FIG. As shown in the figure, the average feed length detection value Wfa, the average welding current detection value Iwa, and the average welding voltage detection value Vwa during welding are input to the average arc length calculation circuit CLA, and a plurality of calculation processes are performed. As a result, the average arc length calculation value Laa is output. First, the average wire overhang length calculation circuit LXA receives the average feed speed detection value Wfa and the average welding current detection value Iwa and performs an operation corresponding to the above-described equation (1). As a result, the average wire overhang length is obtained. The operation value Lxa is output.

Second, the average wire overhang voltage calculation circuit VXA receives the above average wire overhang length calculation value Lxa and average welding current detection value Iwa as input (2).
An operation corresponding to the equation is performed, and as a result, an average wire protrusion voltage calculation value Vxa is output. Third, the average arc voltage calculation circuit VAA receives the average welding voltage detection value Vwa and the average wire protrusion voltage calculation value Vxa as input and performs a calculation corresponding to the above-described equation (3). An arc voltage calculation value Vaa is output.

Finally, the average arc length calculation circuit LAA is:
With the above average arc voltage calculation value Vaa and average welding current detection value Iwa as inputs, a calculation corresponding to the above-described equation (4) is performed, and as a result, an average arc length calculation value Laa is output. As described above, the average arc length calculation circuit CLA
Calculates the average arc length calculation value Laa during welding by sequentially repeating the arithmetic processing by the arithmetic circuits described above.

FIG. 3 shows the average arc length calculation circuit CL.
1 is a block diagram showing a circuit configuration of a consumable electrode gas shielded arc welding power supply device for implementing a conventional voltage setting automatic control method using A. FIG. In the same drawing, a pulse arc welding power supply device is exemplified as a consumable electrode gas shielded arc welding power supply device. Hereinafter, each circuit block will be described with reference to FIG.

The output control circuit 6 receives an input of a commercial power supply, controls the output in accordance with a current error amplification signal Eai described later, and outputs a welding current Iw and a welding voltage V suitable for an arc load.
Output w. Generally, as the output control circuit 6, an inverter control circuit, a chopper control circuit, a thyristor phase control circuit, or the like is used. In the case of an inverter control circuit, a primary rectifier circuit for rectifying a commercial power supply, a smoothing circuit for smoothing a rectified rippled DC voltage, an inverter circuit for converting the smoothed DC voltage to a high-frequency AC, A high-frequency transformer for stepping down the alternating current to a voltage suitable for the arc load, a secondary rectifier circuit for rectifying the stepped-down high-frequency alternating current, a DC reactor for smoothing the rectified rippled DC, and a current error amplification signal Eai to be described later. And a PWM control circuit that performs a PWM control according to the following.

The welding wire 1 is fed by a feed roll 5a of a wire feeding device, and is fed from a contact tip attached to the tip of the welding torch 4,
An arc 3 is generated between the workpiece 2 and the workpiece 2 to perform welding.

The feed speed setting circuit WS outputs a preset feed speed setting signal Ws. Usually welding wire 1
Are fed at a preset feed rate, the feed rate setting signal Ws and the above-described average feed rate detection signal Wfa have substantially the same value. Here, the feed speed setting signal Ws is used as an alternative signal to the average feed speed detection signal Wfa in order to provide a simpler circuit configuration that does not require the feed speed detection circuit. The welding current detection circuit ID is the welding current Iw
And outputs a welding current detection signal Id. The welding voltage detection circuit VD detects the welding voltage Vw and outputs a welding voltage detection signal Vd. The welding current smoothing circuit IDA is:
The above welding current detection signal Id is input, the signal is smoothed, and the average welding current detection value Ida is output. The welding voltage smoothing circuit VDA receives the above welding voltage detection signal Vd, smoothes the signal, and outputs an average welding voltage detection signal Vda.

The average arc length calculation circuit CL described above with reference to FIG.
A receives the feed speed setting signal Ws, the average welding current detection signal Ida, and the average welding voltage detection signal Vda as inputs,
The arithmetic processing described above is performed, and as a result, an average arc length calculation signal Laa is output. Average arc length setting circuit LA
S outputs a preset average arc length setting signal Las. The arc length error amplification circuit EAL amplifies an error between the average arc length calculation signal Laa as a feedback signal and the average arc length setting signal Las as a target value, and outputs an arc length error amplification signal ΔL. I do.

The error signal integration circuit VS receives the arc length error amplification signal ΔL as an input, integrates the signal, and
It outputs a voltage setting signal Vs. Voltage filter circuit VDF
Receives the welding voltage detection signal Vd as an input and calculates a number [k
[Hz] is removed. The reason why the high-frequency component included in the welding voltage detection signal Vd is removed is as follows. That is, as described above, the arc length rapidly changes due to the arc phenomenon instability factor and the mechanical instability factor,
Accordingly, the welding voltage Vw also changes rapidly. The frequency component of the speed at which the welding voltage Vw changes is several tens [Hz] to
It is about several hundred [Hz]. Therefore, the output control circuit 6
In order to improve the stability of the control system against higher-frequency noises such as the occurrence of unnecessary high-frequency components, unnecessary high-frequency components of several kHz or more are removed. Even after this processing, the frequency components necessary for detecting the original change in the arc length remain. The voltage error amplifier circuit EAV outputs the welding voltage filter signal Vdf serving as a feedback signal.
, And an error between the voltage setting signal Vs as the target value and the voltage setting signal Vs is amplified, and a voltage error amplified signal ΔV is output.

The V / F conversion circuit VF receives the above-described voltage error amplification signal ΔV, converts the signal into a signal having a frequency proportional to the magnitude of the voltage value, and converts the frequency signal into a H signal for a short time at each frequency. Vf is output. The peak current conduction time setting circuit TP outputs a preset peak current conduction time setting signal Tp. Monostable multivibrator MM
Outputs a switching signal Mm which becomes an H signal for a certain period of time set by the above peak current conduction time setting signal Tp, using the above-mentioned frequency signal Vf as an input, a rising edge when the signal becomes a minute time H signal as a trigger signal, and I do. The peak current setting circuit IP outputs a preset peak current setting signal Ip. The base current setting circuit IB outputs a preset base current setting signal Ib. Switching circuit SW
Switches the peak current setting signal Ip and the base current setting signal Ib using the switching signal Mm as a control signal, and outputs a current setting signal Is. At this time, when the switching signal Mm is the H signal, it is connected to the a side, the peak current setting signal Ip becomes the current setting signal Is, and the switching signal M
When m is the L signal, it is connected to the b side, and the base current setting signal Ib becomes the current setting signal Is.

The current error amplifier circuit EAI amplifies the error between the welding current detection signal Id serving as a feedback signal and the current setting signal Is serving as a target value, and outputs a current error amplified signal Eai. As described above, output control is performed by the output control circuit 6 using this signal as a control signal.

FIG. 4 is a timing chart of each signal in the block diagram of the prior art pulse arc welding power supply device described above with reference to FIG. FIG. 6A shows the time change of the welding current detection signal Id, and FIG. 6B shows the time change of the welding voltage detection signal Vd.
Shows the time change of the average arc length calculation signal Laa, FIG. 3D shows the time change of the frequency signal Vf, and FIG. 3E shows the time change of the switching signal Mm. I have. Hereinafter, the operation of each signal will be described with reference to FIGS.

(1) Between time t1 and time t4 shown in FIG. 4, there is almost no change in the arc length and a steady state of a constant value. In such a steady state, the average welding voltage detection signal Vda and the average welding current detection signal Ida are constant values, and the feed speed setting signal Ws is also a predetermined constant value. Circuit CLA
The average arc length calculation signal Laa shown in FIG. The voltage setting signal Vs described above with reference to FIG. 3 is output such that the average arc length calculation signal Laa and the average arc length setting signal Las described above with reference to FIG. 3 are substantially equal. Further, the voltage setting signal Vs described above and FIG.
In order that the welding voltage filter signal Vdf shown in (B) becomes substantially equal, the V / F conversion circuit VF described above with reference to FIG.
The frequency signal Vf shown in (D) is output. This frequency signal Vf has a pulse period T1 as shown in FIG.
The signal becomes an H signal for a very short time every time. Using the rise of this signal to the H signal as a trigger signal, the switching signal Mm shown in FIG. 4E is output from the monomultivibrator MM described above with reference to FIG. The switching signal Mm is, as shown in FIG.
The signal becomes an H signal during the peak current conduction time setting signal Tp. As shown in FIG. 4A, the welding current detection signal Id is the peak current conduction time Tp at which the switching signal Mm becomes the H signal.
During this period, the peak current Ip is conducted, and while the switching signal Mm is the L signal, the base current Ib is conducted. Further, as shown in FIG. 4B, the welding voltage detection signal Vd has a high voltage value during a period during which the peak current Ip flows, and has a low voltage value during a period during which the base current Ib flows.

(2) Next, at time t4, the distance between the tip and the workpiece is sharply reduced due to hand shake of the welding operator or the like, and the arc length La shown in FIG.
Will be described below. Since the arc length La becomes shorter during the period from the time t4 to the time t5, the welding voltage detection value Vd that is directly proportional to the arc length La also becomes smaller than the value before the time t4. Therefore, the welding voltage filter signal Vdf shown in FIG. 4B becomes small, but the average welding voltage detection value Vda shown in FIG. 4B hardly changes because the transient state is smoothed. Similarly, the average welding current detection signal Ida shown in FIG. 4A hardly changes because the transient state is smoothed.

As described above, both the average welding voltage detection signal Vda and the average welding current detection signal Ida are constant values with almost no change, and the feed speed setting signal Ws is also a preset constant value. The average arc length calculation signal Laa shown in FIG. 4C output by the above average arc length calculation circuit CLA also becomes a constant value with almost no change. For this reason, the voltage setting signal Vs output so that the average arc length calculation signal Laa is substantially equal to the average arc length setting signal Las described above with reference to FIG. 3 is a constant value with almost no change.

Further, the above-mentioned voltage setting signal Vs and FIG.
In order that the welding voltage filter signal Vdf shown in (B) becomes substantially equal, the V / F conversion circuit VF described above with reference to FIG.
The frequency signal Vf shown in (D) is output. At this time,
Since the welding voltage filter signal Vdf is small as described above, the pulse cycle of the frequency signal Vf is T
2, which is shorter than the pulse period T1 before time t4. Therefore, the welding current detection signal Id is as shown in FIG.
As shown in the figure, the peak current Ip is supplied during the period of the peak current supply time Tp, and the base current Ib is supplied during the period until the pulse period T2 elapses thereafter. That is, in the period from time t4 to time t5, the welding voltage filter signal Vdf decreases with the change in the arc length La, and as a result, the pulse cycle is shortened to T2 <T1 by feedback control. When the pulse period is shortened, the effective value of the welding current is increased, so that the melting speed is increased, and as a result, the arc length La is increased. That is, control for restoring the change in the arc length La works.

The period from time t5 to time t6 As shown in FIG.
As in the period of the time t5, the state is still shorter than before the time t4. Therefore, the same operation as in the above-described section is performed. That is, since the value is still smaller than the voltage setting signal Vs due to the change in the welding voltage filter signal Vdf due to the change in the arc length La, the pulse cycle T3 becomes shorter than the pulse cycle T1 by feedback control. When the pulse period is shortened, the effective value of the welding current is increased, so that the melting speed is increased, and as a result, the arc length La is further increased.

The period from time t6 to time t7 As shown in FIG.
Although it is longer than the period at time t6, it is still at time t4
It is shorter than before. Therefore, the same operation as in the above-described section is performed. That is, by the change of the welding voltage filter signal Vdf accompanying the change of the arc length La,
Since the value is still smaller than the voltage setting signal Vs, the pulse cycle T4 becomes shorter than the pulse cycle T1 by the feedback control. When the pulse period is shortened, the effective value of the welding current is increased, so that the melting speed is increased and the arc length La is further increased, and returns to the original value before time t4 at time t7.

As described above, in the prior art, the control for suppressing the rapid change in the arc length caused by the unstable factor of the arc phenomenon, the mechanical instability factor, and the like is performed by using the welding voltage filter signal Vdf as the feedback signal. And the voltage setting automatic control hardly contributes. Further, in the above, the output control of the welding power supply device is performed by presetting the peak current Ip and the peak current conduction time Tp, and performing feedback control of the pulse cycle T. In addition to the above method, a method of presetting the peak current Ip and the pulse period T and performing feedback control of the peak current conduction time Tp or a method of presetting the peak current conduction time Tp and the pulse period T and performing feedback control of the peak current Ip Conventional techniques for controlling the output of the welding power supply device by the above method are also used.

FIG. 5 is a diagram showing a change over time of an average arc length calculation signal at the time of arc start in order to show the effect of the above-described conventional voltage setting automatic control method. FIG. 7A shows an average arc length calculation signal L at the time of arc start.
The time-dependent change of aa is shown together with the schematic diagram of the arc generating unit, and FIG. 3B shows the time-dependent change of the voltage setting signal Vs described above with reference to FIG.

At time t1, the initial value of the average arc length calculation signal Laa when the arc 3 is generated is L0 [m
m]. The initial value L0 is determined by a preset initial value Vs0 of the voltage setting sign Vs shown in FIG. At time t1, the value of the average arc length calculation signal Laa serving as a feedback signal is larger than the value of the average arc length setting signal Las serving as a target value, and therefore, the updated voltage setting signal V output by the voltage setting automatic control.
The value of s becomes smaller than the initial setting value Vs0. When the voltage setting signal Vs decreases, the output of the welding power supply device decreases due to the arc length control based on the welding voltage filter signal Vdf described above, and as a result, the arc length decreases.

After time t1, the same operation as that of the item is repeated. At this time, as described above with reference to FIG.
In the prior art average arc length calculation circuit CLA, the number [H
z] Only the change in the average arc length less than or equal to z] can be calculated. Therefore, the response speed as a control system of the voltage setting automatic control using the average arc length calculation value Laa as a feedback signal is about 1 [Hz] or less. For this reason,
As shown in FIG. 5, the voltage setting signal Vs and the average arc length calculation signal Laa gradually decrease due to the slow response speed, and the average arc length calculation signal Laa approaches the average arc length setting signal Las. Then, at time t3,
Both are substantially equal, and converge to an appropriate average arc length.

As described above, the conventional voltage setting automatic control method can automatically control the average arc length to a proper average only by setting a proper average arc length setting signal Las. It is possible to obtain a high welding quality of the workpiece.

[0038]

FIG. 6 is a diagram showing a conventional voltage setting automatic control method for explaining a problem to be solved by the present invention at the time of arc start under the same welding conditions as in FIG. 5 described above. FIG. 5 is a diagram showing a time change of an average arc length calculation signal in FIG. FIG. 3A shows a time-lapse change of the average arc length calculation signal Laa at the time of arc start together with a schematic diagram of an arc generating unit. FIG. 3B shows the voltage setting signal Vs described above with reference to FIG. The time change is shown. However, only the average welding current value differs between the welding conditions of FIG. 6 and the welding conditions of FIG. 5, and the average welding current value of FIG. 6 is smaller than the average welding current value of FIG. It is.

At time t1, the initial value of the average arc length calculation signal Laa when an arc is generated is L1 [mm].
This is longer than L0 [mm] in FIG. The reason is that the preset initial set value Vs0 of the voltage setting symbol Vs shown in FIG. 5B is the same as that in FIG. 5, but the average initial current value is small, so that the same initial set value Vs0 is obtained. This is because the corresponding average arc length differs and becomes longer.

From this state, the average arc length calculation signal Laa is gradually shortened by the same operation as in FIG. 5, and converges to the value of the average arc length setting signal Las at time t3. At this time, as described above, the response speed of the voltage setting automatic control is reduced to about 1 [Hz] or less, being limited by the calculation speed of the average arc length calculation circuit CLA of the related art. As a result, the state in which the average arc length is extremely long continues from the time t1 to the time t2, and the welding quality of the work to be welded such as the occurrence of blowholes, the occurrence of undercuts, and the deterioration of the bead appearance becomes poor. .

The initial setting value Vs0 of the voltage setting signal Vs
The factors that cause the average arc length to be different even if are the same value include not only the average welding current value described above, but also many other factors such as the diameter of the welding wire, the type of shielding gas, and the welding speed.

FIG. 7 shows an apparent arc length and a true arc length when the cleaning width fluctuates due to a cause to be described later in order to explain the problem to be solved by the present invention of the prior art voltage setting automatic control method. FIG. FIG. 6A shows a case where the cleaning width is narrow and the apparent arc length becomes long, and FIG. 6B shows a case where the cleaning width is wide and the apparent arc length becomes short. As described above, the welding voltage value and the apparent arc length are directly proportional to each other, but argon gas (Ar) is used as a shielding gas.
When a shield gas having a ratio of about 90% or more or 100% is used (hereinafter, referred to as an argon-rich gas), the ratio may not always be directly proportional for reasons to be described later. In addition, as an example of the above shielding gas, 100 mm is used for MIG welding of aluminum and its alloy.
[%] Argon gas is used, and a mixed gas such as 98 [%] argon gas + 2 [%] oxygen, 95 [%] argon gas + 5 [%] oxygen is used for MIG welding of stainless steel. 90 for mag welding thin steel
[%] Argon gas + 10 [%] carbon dioxide gas, 95 [%]
A mixed gas such as argon gas + 5 [%] carbon dioxide gas is used. In the MIG or MAG welding using the above-described argon-rich gas, a cleaning action occurs on the surface of the workpiece, so that an arc is likely to be generated from an uncleaned boundary portion of the workpiece. For this reason, the apparent arc length changes due to the reason described later due to the narrowing of the cleaning width.

As shown in FIG. 1A, the welding wire 1 is supplied with power from the contact tip 4a, and an arc 3 is generated between the welding wire 1 and the workpiece 2. Cleaning width is CZ1
And an arc is generated at the boundary of the cleaning area. At this time, the apparent arc length is La1 [mm], but the true arc length is Lb1 [mm]. The true arc length is the length of the arc actually generated, and the apparent arc length is the length between the tip of the wire and the workpiece directly below. What is directly proportional to the welding voltage value is exactly the true arc length Lb1. On the other hand, the welding quality is greatly affected by the apparent arc length La1,
It is hardly affected by the true arc length Lb1. Therefore, the arc length control for improving the welding quality is control of the apparent arc length as described above. If the cleaning width CZ1 is always substantially the same during welding,
Since the apparent arc length La1 and the true arc length Lb1 are geometrically directly proportional, the control of the apparent arc length is the same as the control of the true arc length. Since the arc length and the welding voltage value are directly proportional, the control of the true arc length and the control of the welding voltage value are the same. Therefore, as described above, when the cleaning width during welding is a substantially constant value, it can be replaced by controlling the apparent arc length by controlling the welding voltage value. However, if the cleaning width during welding varies, the above substitution does not apply for the following reasons.

FIG. 6B shows a case where the cleaning width fluctuates due to the above-mentioned cause during welding and increases from CZ1 to CZ2. At this time, since the arc length control based on the welding voltage value according to the conventional technique described above is performed, the true arc length that is in direct proportion to the welding voltage value is Lb1 having the same value as that in FIG. It is controlled so that
Therefore, the apparent arc length La2 changes and becomes shorter by ΔL12 than La1 in FIG. Therefore, in welding in which the cleaning width fluctuates during welding, the apparent arc length may not be able to be maintained at a constant value by arc length control using a welding voltage value according to a conventional technique.

In MIG welding or MAG welding using an argon-rich gas, the cleaning width during welding is constantly fluctuated due to the surface condition of the workpiece, the shielding state of the arc generating portion due to the shielding gas, temperature change of the workpiece, and the like. It is often. Hereinafter, the operation of the related art when the cleaning width fluctuates rapidly during welding will be described.

FIG. 8 is a diagram showing the temporal change of the apparent arc length La when the cleaning width fluctuates rapidly during welding using the conventional pulse arc welding power supply device described above with reference to FIG. . FIG. 7A shows a time change of the arc shape during welding, and FIG. 7B shows an apparent arc length La and an average arc length calculation signal Laa which are instantaneous values.
(C) shows the time change of the voltage setting signal Vs. In the figure, since the argon-rich gas is used as the shielding gas, the cleaning action occurs as described above.

At time t1 during welding, FIG.
As shown in (1), the cleaning width is constant, and the apparent arc length La1 [mm] is at an appropriate value. Therefore, the apparent arc length La and the average arc length setting signal Las shown in FIG. Similarly, FIG.
Is set at a constant value. The above state continues until just before time t2.

At time t2, if the cleaning width rapidly fluctuates and becomes narrow due to a change in the surface condition of the work to be welded, a change in the shield condition of the shield gas, etc., the arc shape suddenly decreases as shown in FIG. Change. That is, as described above, even if the cleaning width fluctuates, the true arc length hardly changes by the conventional arc length control, but the apparent arc length La2 [mm] becomes longer. This state continues until the cleaning width returns to the original stable state. During this period, since the apparent arc length La2 is longer than an appropriate value, welding defects such as generation of blow holes and generation of undercut are likely to occur.

At time t3, if the cleaning width fluctuates rapidly and widens, the true arc length hardly changes, but the apparent arc length La3 as shown in FIG.
[Mm] becomes shorter. If the apparent arc length La3 is shorter than the appropriate value, poor welding quality of the work to be welded such as generation of a large amount of spatter and deterioration of the bead appearance is likely to occur.

As described above, when the voltage control automatic control of the prior art and the arc length control of the conventional technology are used together, the change in the apparent arc length due to the rapid fluctuation of the cleaning width is suppressed, and the welding quality is always good. It is difficult to keep.

Therefore, in the present invention, the arc length calculation method of the prior application (Japanese Patent Application No. 10-331266) by the same applicant as the present invention, which can calculate the arc length of an instantaneous value described later, is used as the arc length control method. By using it, the rapid change of the arc length due to the unstable factor can always be suppressed in a short time, and the appropriate arc length can be automatically set, so that the welding quality of the workpiece can be improved. Can be good. The prior invention is an invention of the above-described arc length calculation method and a welding line tracing control method using the arc length calculation method, and has a completely different configuration from the present invention.

[0052]

According to the first aspect of the present invention, as shown in FIGS. 9 and 10, in the arc length control method of the consumable electrode gas shielded arc welding, the welding current value Iw and the welding current value Iw during welding are controlled. The welding voltage value Vw is repeatedly detected and the feeding speed Wf is repeatedly detected or preset, and the welding current value Iw detected at the n-th time, the welding voltage value Vw detected at the n-th time, and the n-th A melt speed calculation step WM for outputting a detected melt speed calculated value Wm with the detected or preset feed speed Wf as an input;
A wire overhang length change amount calculation process DLX for outputting a wire overhang length change amount calculation value ΔLx, an n-th wire overhang length addition operation process DX for outputting an n-th wire overhang length calculation value Lx, and an n-th wire Projected portion voltage calculation value V
a wire protruding portion voltage calculating process VX for outputting x,
An arc length calculation process CL including an arc voltage calculation process VA for outputting a second arc voltage calculation value Va and an arc length calculation process LA for outputting an nth arc length calculation value La.
And outputs the n-th arc length calculation value La.
The output control of the welding power supply device is performed by feedback control using the n-th arc length calculation value La as a feedback signal and a preset arc length set value Ls as a target value to maintain the arc length during welding at the target value. This is an arc length control method.

The invention of claim 2 at the time of filing is shown in FIGS.
As shown in FIG. 0, in the arc length control method of the consumable electrode gas shielded arc welding, the welding current value Iw and the welding voltage value Vw during welding are repeatedly detected and the feeding speed Wf is determined.
Is repeatedly detected or set in advance, and when the n-th detected welding current value Iw and the first calculation are performed, the previously set wire protrusion length initial value Lx0 becomes the previously calculated wire protrusion length calculation value Lx (n-1) The melting speed calculation process WM for outputting the n-th melting speed calculation value Wm as an input, the n-th detection or the preset feeding speed Wf, and the n-th melting speed calculation value Wm , And outputs an n-th wire protrusion length change amount calculation value ΔLx, the wire protrusion length change amount calculation process DLX, the n-th wire protrusion length change amount calculation value ΔLx, and the previous wire protrusion length calculation value Lx (n-1) is input and a wire overhang length addition operation process DX for outputting an n-th wire overhang length operation value Lx
And the n-th wire projection length calculation value Lx and the n-th detected welding current value Iw, and
A wire protrusion voltage calculation process VX for outputting a wire protrusion voltage calculation value Vx for the third time, the welding voltage value Vw detected at the n-th time, and the wire protrusion voltage calculation value Vx for the n-th time as input, An arc voltage calculation process VA for outputting an n-th arc voltage calculation value Va, and an n-th arc voltage calculation value Va and the n-th welding current value Iw detected as input, The n-th arc length calculation value La is output by an arc length calculation process CL including an arc length calculation process LA that outputs an arc length calculation value La, and the n-th arc length calculation value La is used as a feedback signal. And an arc length control for controlling the output of the welding power supply device by feedback control using a preset arc length set value Ls as a target value to maintain the arc length during welding at the target value. It is a method.

The invention of claim 3 at the time of filing is shown in FIGS.
As shown in FIG. 0, in the arc length control method of the consumable electrode gas shielded arc welding, the welding current value Iw and the welding voltage value Vw during welding are repeatedly detected and the feeding speed Wf is determined.
Is repeatedly detected or set in advance, and when the n-th detected welding current value Iw and the first calculation are performed, the previously set wire protrusion length initial value Lx0 becomes the previously calculated wire protrusion length calculation value Lx (n-1). With the constants α and β set in advance, the n-th melting speed calculation value Wm = α · Iw +
a melting speed calculation process WM that is β · Lx (n−1) · Iw ² ;
With the n-th detection or the previously set feeding speed Wf and the n-th melting speed calculation value Wm as inputs, the n-th wire protrusion length change calculation value ΔLx = ( Wf−Wm) · ΔT, the wire extension length change calculation process DLX, the n-th wire extension length change value ΔLx, and the previous wire extension length calculation value Lx (n−1), The nth wire overhang length calculation value Lx = Lx (n-1) + ΔLx, wire overhang length addition operation process DX, the nth wire overhang length calculation value Lx, and the n-th detected welding current Value Iw
, And an n-th wire protrusion voltage calculation value Vx = Rx · Lx · Iw by a preset constant Rx.
, And the n-th detected welding voltage value Vw and the n-th calculated wire projection voltage value Vx, and the n-th calculated arc voltage value Va = The arc voltage calculation process VA which is Vw-Vx, the n-th arc voltage calculation value Va and the n-th detected welding current value Iw are input, and the n-th arc voltage calculation process is performed based on preset constants a to d. Arc length calculation value of La = (Va−ac · Iw) / (b + d · Iw)
The n-th arc length calculation value La is output by an arc length calculation process CL including an arc length calculation process LA, and the n-th arc length calculation value La is used as a feedback signal. This is an arc length control method for controlling the output of the welding power supply device by feedback control using the value Ls as a target value and maintaining the arc length during welding at the target value.

The invention of claim 4 at the time of filing is shown in FIGS.
As shown in FIG. 0, the peak current Ip is supplied during the peak current supply time Tp, and then the base current Ib is supplied until the end of the pulse period T, so that the peak current Ip is supplied and the base current Ib is supplied. In the arc length control method of the consumable electrode pulse arc welding that alternately repeats the above, the feedback control described in claim 1, claim 2 or claim 3 applies the n-th arc length calculation value L
a is a feedback signal, and the arc length set value Ls
, A feedback control for controlling the output of the welding power supply device using the pulse period T, the peak current conduction time Tp or the peak current Ip as a control signal. An arc length control method according to item 3.

The invention of claim 5 at the time of filing is shown in FIGS.
As shown in FIG. 3, in the arc length control method of the consumable electrode DC arc welding having a constant voltage characteristic corresponding to the voltage set value Vs, it is described in claim 1 at the time of application, claim 2 at the time of application, or claim 3 at the time of application. The feedback control uses the n-th arc length calculation value La as a feedback signal, sets the arc length set value Ls as a target value, and sets the voltage set value Vs
The present invention relates to a feedback control in which the output of the welding power supply device is controlled to a constant voltage characteristic by using the control signal as a control signal.
An arc length control method according to claim 2 or 3 at the time of application.

The invention of claim 6 at the time of filing is shown in FIGS.
0, a welding current detection circuit ID for repeatedly detecting the welding current value Iw, a welding voltage detection circuit VD for repeatedly detecting the welding voltage value Vw, a feeding speed detection circuit for repeatedly detecting the feeding speed Wf, or A feed speed setting circuit WS for presetting the feed speed Wf, the n-th detected welding current value Iw, and the n-th detected welding voltage value V
w and the above-mentioned n-th detection or a preset feeding speed W
f, and outputs an n-th melting speed calculation value Wm to output a melting speed calculation process WM; an n-th wire projection length change calculation value DLX that outputs a wire projection length change calculation value ΔLx; n-th wire overhang length calculation value L
a wire overhang length adding operation process DX for outputting x;
A wire extension voltage calculation process VX for outputting a wire extension voltage calculation value Vx for the first time, an arc voltage calculation process VA for outputting an nth arc voltage calculation value Va, and an arc length calculation value La for the nth time Output arc length calculation process L
A, an arc length calculation circuit CL that outputs an arc length set value Ls, an arc length set circuit LS that outputs an arc length set value Ls, and the n-th arc length calculated value La as a feedback signal. A consumable electrode gas shielded arc welding power supply device for controlling the output of the welding power supply device by the output signal of the feedback control circuit to maintain the arc length during welding at a target value.

The invention of claim 7 at the time of filing is shown in FIGS.
0, a welding current detection circuit ID for repeatedly detecting the welding current value Iw, a welding voltage detection circuit VD for repeatedly detecting the welding voltage value Vw, a feeding speed detection circuit for repeatedly detecting the feeding speed Wf, or A feed speed setting circuit WS for presetting the feed speed Wf, and a previously set wire protrusion length Lx0 which is a preset wire protrusion length initial value Lx0 at the time of calculating the n-th detected welding current value Iw and the first time. A melt speed calculation process WM for outputting a melt speed calculation value Wm for the nth time with the calculated value Lx (n-1) as an input, a feed speed Wf for the nth detection or a preset feed speed, and the nth melt speed calculation process. The nth wire protrusion length change amount calculation process DLX which outputs the nth wire protrusion length change amount calculation value ΔLx with the melt speed calculation value Wm as an input, and the nth wire protrusion length change amount calculation value ΔLx When As inputs and serial last wire extension length computation value Lx (n-1), the wire extension length sum operation process DX for outputting the n-th wire extension length computation value Lx
And the n-th wire projection length calculation value Lx and the n-th detected welding current value Iw, and
A wire protrusion voltage calculation process VX for outputting a wire protrusion voltage calculation value Vx for the third time, the welding voltage value Vw detected for the n-th time, and the wire protrusion voltage calculation value Vx for the n-th time as input, The n-th arc voltage calculation process VA for outputting the n-th arc voltage calculation value Va, and the n-th arc voltage calculation value Va and the n-th detected welding current value Iw as inputs, An arc length calculation circuit CL comprising an arc length calculation process LA for outputting an arc length calculation value La, an arc length setting circuit LS for outputting an arc length setting value Ls, and feedback of the n-th arc length calculation value La Signal, and the arc length set value L
a consumable electrode gas shielded arc welding power supply device for controlling the output of the welding power supply device by the output signal of the feedback control circuit to maintain the arc length during welding at the target value. It is.

The invention of claim 8 at the time of filing is shown in FIGS.
0, a welding current detection circuit ID for repeatedly detecting the welding current value Iw, a welding voltage detection circuit VD for repeatedly detecting the welding voltage value Vw, a feeding speed detection circuit for repeatedly detecting the feeding speed Wf, or A feed speed setting circuit WS for presetting the feed speed Wf, and a previously set wire protrusion length Lx0 which is a preset wire protrusion length initial value Lx0 at the time of calculating the n-th detected welding current value Iw and the first time. Using the calculated value Lx (n-1) as an input, predetermined constants α and β
Thus, the n-th melting speed calculation value Wm = α · Iw + β
Lx (n−1) · Iw ² , the melting speed calculation process WM, the n-th detection or the preset feeding speed Wf and the n-th melting speed calculation value Wm, Based on the set constant ΔT, the n-th wire protrusion length change calculation value ΔLx = (Wf−Wm) · ΔT, and the wire protrusion length change calculation process DLX, and the n-th wire protrusion length change calculation value ΔLx And the last wire overhang length calculation value Lx (n-1) as input, the wire overhang length addition operation process DX in which the n-th wire overhang length calculation value Lx = Lx (n-1) + ΔLx, The n-th wire protrusion length calculation value Lx and the n-th detected welding current value Iw are input, and the n-th wire protrusion voltage calculation value Vx = Rx · Lx · Iw by a preset constant Rx. Calculation of voltage at a certain wire protrusion The Vth, the n-th detected welding voltage value Vw, and the n-th wire protrusion voltage calculation value Vx are input, and the n-th arc voltage calculation value Va = Vw−Vx. The voltage calculation process VA, the n-th arc voltage calculation value Va and the n-th detected welding current value Iw are input,
The n-th arc length calculation value La = (Va−a · c · Iw) / (b + d · I) by using preset constants a to d.
w) arc length calculation process LA, arc length setting circuit LS for outputting arc length set value Ls, and n-th arc length calculated value La as a feedback signal. And a feedback control circuit that sets the arc length set value Ls as a target value.
This is a consumable electrode gas shielded arc welding power supply for controlling the output of the welding power supply in accordance with the output signal of the feedback control circuit and maintaining the arc length during welding at a target value.

The invention of claim 9 at the time of filing is shown in FIGS.
As shown in FIG. 0, the peak current Ip is supplied during the peak current supply time Tp, and then the base current Ib is supplied until the end of the pulse period T, so that the peak current Ip is supplied and the base current Ib is supplied. In the consumable electrode pulse arc welding power supply device which alternately repeats the above, the feedback control circuit according to claim 6, claim 7, or claim 8 feedbacks the n-th arc length calculation value La. 7. A feedback control circuit for controlling the output of a welding power source device using the pulse period T, the peak current conduction time Tp or the peak current Ip as a control signal, the arc length set value Ls as a target value, and the control signal. , A consumable electrode gas shielded arc welding power supply apparatus according to claim 7 or claim 8.

The invention according to claim 10 at the time of filing is a consumable electrode DC arc welding power supply device having a constant voltage characteristic corresponding to a voltage set value Vs, as shown in FIGS.
A feedback control circuit according to claim 6, claim 7, or claim 8 applies the n-th arc length calculation value La as a feedback signal and sets the arc length set value Ls as a target value. 7. A feedback control circuit as claimed in claim 6, wherein the feedback control circuit is configured to control the output of the welding power supply device to a constant voltage characteristic by using the voltage set value Vs as a control signal.
A consumable electrode gas shielded arc welding power supply device according to claim 7 or 8 at the time of filing.

[0062]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIGS. 9 and 10, an embodiment of the present invention relates to a method of controlling the arc length of a consumable electrode gas shielded arc welding.
And the welding voltage value Vw is repeatedly detected, and the feeding speed Wf is repeatedly detected or set in advance. When the n-th welding current value Iw and the first calculation are calculated, the preset wire protrusion length initial value Lx0 is used. A previously set constant α is input with the previous wire protrusion length calculation value Lx (n-1) as an input.
And β, the n-th calculation value of melting speed Wm = α · I
Melting speed calculation process WM that is w + β · Lx (n−1) · Iw ²
And the feed speed Wf detected at the n-th time or set in advance.
And the n-th melting speed calculation value Wm as input,
The nth wire protrusion length change calculation value ΔLx = (Wf−Wm) · ΔT using the preset constant ΔT, the wire protrusion length change calculation process DLX, and the nth wire protrusion length change calculation value With the input of ΔLx and the previous wire extension length calculation value Lx (n−1) as input, the wire extension length addition calculation process DX in which the nth wire extension length calculation value Lx = Lx (n−1) + ΔLx is performed, The n-th wire protrusion length calculation value Lx and the n-th detected welding current value Iw are input, and the n-th wire protrusion voltage calculation value Vx = Rx · Lx · by a preset constant Rx.
The n-th arc voltage calculation value Va is input with the wire protrusion voltage calculation process VX, which is Iw, the n-th detected welding voltage value Vw, and the n-th wire protrusion voltage calculation value Vx. = Vw-Vx, and the n-th arc voltage calculation value Va and the n-th detected welding current value Iw as inputs, and the n-th arc voltage calculation process VA is performed using predetermined constants a to d. The second arc length calculation value La = (Va−ac · Iw) / (b + d ·
Iw) by the arc length calculation process CL consisting of the arc length calculation process LA, the n-th arc length calculation value La
Is output, the output control of the welding power supply device is performed by the feedback control using the n-th arc length calculation value La as a feedback signal, and a preset arc length set value Ls as a target value, and the target arc length during welding is set. This is an arc length control method that maintains the value.

[0063]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the above-mentioned prior art average arc length calculation method, the precondition is that the melting speed Wm and the feed speed Wf are substantially equal. However, as described above, it cannot be used at a high speed of several Hz or more. On the other hand, in the arc length calculation method of the prior application, the change in the wire protrusion length can be calculated by calculating the melting speed for each minute time and calculating the difference from the feeding speed. It can be used even when the changing speed of the arc length is as fast as several [kHz].

In the arc length calculation method of the prior application, unlike the prior art, the welding current value Iw, the feeding speed Wf, and the welding voltage value Vw of the instantaneous value, not the average value, are input as the input in the short time ΔT during welding. By detecting each time and performing a plurality of arithmetic processes on the detected values, it is possible to calculate the arc length of the instantaneous value for each minute time ΔT. Hereinafter, the calculation processing of the calculation method will be described.

At every minute time ΔT [s], the welding current value Iw
[A], feeding speed Wf [mm / s] and welding voltage value Vw
The n-th calculation when [V] is detected and the arc length La is calculated is as follows. First, the melting speed Wm (n) [mm / s] is determined by an experiment to determine the welding current value Iw (n).
[A] and the previous wire protrusion length Lx (n-1) [m
m] as a variable is known by the following equation. Wm (n) = α · Iw (n) + β · Lx (n−1) · Iw (n) ² (5) where α [mm / (s · A)] and β [1 / (s · A2)] is a constant determined by the diameter, material and type of the welding wire.
Secondly, in order to consider a transient state in which the change rate of the arc length is fast, that is, the feed rate Wf ≠ the melting rate Wm, it is necessary to find a change in the wire protrusion length at every minute time ΔT. The change in the wire protrusion length is the detected feed speed W.
Since the difference between f (n) [mm / s] and the above-mentioned melting speed Wm (n) [mm / s], the change ΔLx (n) [Lx (n) [ mm] is given by the following equation. ΔLx (n) = (Wf (n) −Wm (n)) · ΔT (6) Third, the wire protrusion length Lx in the n-th calculation
(n) [mm] is an added value of the previous wire protrusion length Lx (n-1), which is the (n-1) -th calculation value, and the wire protrusion length change ΔLx (n) [mm]. The following equation is obtained. Lx (n) = Lx (n-1) + ΔLx (n) (7) In the prior art, since the feed rate Wf ≒ the melting rate Wm is a precondition, ΔLx (n) = 0 in the equation (6). Means that the wire protrusion length Lx (n) is calculated.

The subsequent calculations are the same as in the prior art, and are as follows. Fourth, the wire protrusion voltage Vx (n) [V] is equal to the wire protrusion length Lx (n) [m
m] and the welding current value Iw (n) [A] as variables, and the following expression is the same as the above expression (2). Vx (n) = Rx · Lx (n) · Iw (n) (8) where Rx [Ω / mm] is a resistance value per unit length of the welding wire, and the diameter, material, and It is a constant determined by the type. Fifth, the arc voltage value Va
(n) [V] is the same as the following equation (3), using the welding voltage value Vw (n) [V] and the wire protrusion voltage Vx (n) [V] as variables. Va (n) = Vw (n) -Vx (n) (9) Finally, the arc length La (n) [mm] is determined by the arc voltage value Va (n) [V] and the welding current value Iw ( n) With [A] as a variable, it is expressed by the following equation, which is the same as the above-described equation (4). La (n) = (Va (n) −ac · Iw (n)) / (b + d · Iw (n)) (10) where a [V], b [V / mm], c [ Ω] and d [Ω / m
m] is a constant determined by the diameter, material and type of the welding wire, and the type of shielding gas.

As described above, the arc length La (n) can be calculated for each minute time ΔT by repeating the calculations based on the expressions (5) to (10). However,
Since the initial value of the wire protrusion length Lx (0) = Lx0 is required in the first calculation of the expression (5), an appropriate initial value of the wire protrusion length may be set. Further, since the welding wire is fed at a preset feed speed, the feed speed set value can be used as an alternative to the detected value of the feed speed Wf used in the calculation of the equation (6). .

FIG. 9 is a block diagram showing a configuration of an arc length calculation circuit CL for implementing the above-described arc length calculation method of the invention of the prior application. As shown in the figure, in the arc length calculation circuit CL, the feed speed detection value W which is an instantaneous value during welding is provided.
f (n), welding current detection value Iw (n) and welding voltage detection value Vw
(n) is input, a plurality of arithmetic processes are performed, and an arc length calculation value La (n) is output. This calculation is performed for a short time ΔT
It is performed every time.

First, the melting speed calculation circuit WM calculates the welding current detection value Iw (n) and the previous wire protrusion length calculation value Lx (n−
With 1) as an input, a calculation corresponding to the above-described equation (5) is performed, and as a result, a melt speed calculation value Wm (n) is output. Second, the wire protrusion length change amount calculation circuit DL
The calculated melting speed Wm (n) and the detected feed speed Wf
With (n) as an input, a calculation corresponding to the above-described expression (6) is performed, and as a result, a wire protrusion length change value ΔL is calculated.
Output x (n). Thirdly, the wire overhang length addition operation circuit DX calculates the wire overhang length change amount operation value ΔLx
With the input of (n) and the previous wire overhang length calculation value Lx (n-1) as input, a calculation corresponding to the above equation (7) is performed, and as a result, the wire overhang length calculation value Lx (n) is output.

Fourth, a wire protrusion voltage calculation circuit V
X is input with the calculated wire protrusion length Lx (n) and the detected welding current value Iw (n), performs a calculation corresponding to the above equation (8), and as a result, calculates the calculated wire protrusion voltage Vx. (n) is output. Fifth, the arc voltage calculation circuit VA receives the welding voltage detection value Vw (n) and the wire protrusion voltage calculation value Vx (n) as inputs and performs a calculation corresponding to the above-described equation (9). As a result, an arc voltage operation value Va (n) is output. Finally, the arc length calculation circuit LA performs the calculation corresponding to the above-described equation (10) by using the above-described arc voltage calculation value Va (n) and the welding current detection value Iw (n) as inputs, and as a result, the arc The length calculation value La (n) is output.

As described above, the arc length calculation circuit CL
Can sequentially calculate the arc length calculation value La (n), which is an instantaneous value during welding, at every minute time ΔT by repeatedly performing the arithmetic processing by the arithmetic circuits described above. As described above, at the time of the first calculation, the initial value Lx0 previously set as the previous wire protrusion length calculation value Lx (0) is used for the calculation.

FIG. 10 is a circuit block diagram of a consumable electrode gas shielded arc welding power supply for implementing the arc length control method of the present invention using the above-described arc length calculation circuit CL. This figure exemplifies the case of a pulse arc welding power supply as a consumable electrode gas shielded arc welding power supply as in the prior art FIG. Hereinafter, each circuit block will be described with reference to the same figure. However, the same circuit blocks as those in FIG. The circuit blocks different from those in FIG. 3 are an arc length calculation circuit CL, an arc length filter circuit LAF, an arc length setting circuit LS, and an arc length V / F conversion circuit VFL indicated by dotted lines, and are circuit blocks unique to the present invention. It is.

The major differences between the prior art and the present invention are as follows. That is, in the prior art, two-stage feedback control of voltage setting automatic control based on the average arc length calculation value and arc length control based on the welding voltage filter signal has been employed. On the other hand, the present invention is different in that a single-stage feedback control of the arc length control based on the instantaneous arc length calculation value is used.

The arc length calculation circuit CL described above with reference to FIG.
With the feed speed setting signal Ws, the welding current detection signal Id, and the welding voltage detection signal Vd as inputs, the arithmetic processing described above with reference to FIG. 9 is performed, and as a result, an arc length calculation signal La is output. Here, instead of the above-described feed speed setting signal Ws, a feed speed detecting circuit may be added as described above and a feed speed detecting signal Wf as an output signal thereof may be used. The arc length filter circuit LAF receives the arc length calculation signal La as an input and outputs an arc length filter signal Laf from which high-frequency components of several [kHz] or more have been removed.
Here, the reason why high-frequency components of several [kHz] or more are removed is the same as in the case of the voltage filter circuit VDF described above with reference to FIG. That is, the frequency component corresponding to the change in the arc length to be detected is several tens [Hz] to several hundred [Hz].
This is because the stability of the control system with respect to noise generated by the output control circuit 6 and the like is improved by removing unnecessary frequency components beyond that.

The arc length setting circuit LS outputs a preset arc length setting signal Ls. The arc length error amplification circuit EL amplifies the error between the arc length filter signal Laf serving as a feedback signal and the arc length setting signal Ls serving as a target value, and generates an arc length error amplification signal ΔLa
Is output as a voltage signal. Arc length V / F conversion circuit V
The FL receives the above-described arc length error amplified signal ΔLa as an input, converts the amplified signal into a signal having a frequency proportional to the magnitude of the voltage value, and converts the frequency signal V into a minute time H signal for each frequency.
Output f. The subsequent signal processing is the same as in FIG. 3 and will not be described.

FIG. 11 shows the time change of the arc length calculation signal at the time of arc start to show the effect of the arc length control method of the present invention described above with reference to FIG. 10 in comparison with FIG. 6 in the prior art. FIG. This figure shows a time-dependent change of the arc length calculation signal La at the time of starting an arc, together with a schematic diagram of an arc generating unit. At time t1, the initial value of the arc length calculation signal La when an arc occurs is:
L1 [mm] as in the case of FIG. In this state, the arc length calculation signal La (= L1) which is the feedback signal is the arc length setting signal L which is the target value.
Since the length is longer than s, the arc length control signal La of the present invention sharply shortens the arc length calculation signal La, and the time t2
Converges to the value of the arc length setting signal Ls.

The reason for the convergence in such a short time is as shown in FIG.
This is because the calculation speed of the arc length calculation circuit CL of the present invention described above is much faster than that of the prior art, and the response speed of the feedback control system is also very fast.
That is, as described above, the calculation speed of the average arc length calculation circuit of the related art is several [Hz] or less, and the response speed of the voltage setting automatic control of the related art is about 1 [Hz] or less. On the other hand, as described above, the calculation speed of the arc length calculation circuit of the present invention is about several [kHz], and the response speed of the arc length control of the present invention is about several hundred [Hz]. Further, the arc length control method of the present invention uses the arc length setting signal L
Only by setting s to an appropriate value, as described above, an appropriate arc length can be maintained immediately after the start of the arc, regardless of the welding conditions, so that good welding quality of the workpiece can be obtained.

FIG. 12 shows the effect of the arc length control method of the present invention when the cleaning width fluctuates rapidly during welding.
FIG. 9 is a time change diagram of an arc length calculation signal for comparison with FIG. 8 in the related art. FIG. 7A shows the time change of the arc shape during welding, and FIG. 7B shows the time change of the apparent arc length calculation signal La and the arc length setting signal Ls. As in the case of FIG. 8, since an argon-rich gas is used as the shielding gas,
As described above, the cleaning action occurs. Further, the apparent arc length calculation signal La shown in FIG.
The apparent instantaneous value of the arc length La shown in (B) is the same value. This is because, as described above with reference to FIG. 9, the arc length calculation method of the present invention has a high calculation speed, so that the instantaneous value of the apparent arc length can be calculated accurately.

At time t1 during welding, FIG.
As shown in (1), the cleaning width is constant, and the apparent arc length La1 [mm] is at an appropriate value. Therefore, the arc length calculation signal La and the arc length setting signal Ls shown in FIG.

At time t2, if the cleaning width rapidly fluctuates and becomes narrow due to a change in the surface condition of the work to be welded, a change in the shield condition of the shield gas, or the like, the apparent arc length increases instantaneously. The apparent arc length calculation signal La shown in FIG. For this reason, the apparent arc length calculation signal La which is a feedback signal becomes larger than the arc length setting signal Ls which is the target value, and the output of the welding power supply device is controlled by the arc length control of the present invention, and the apparent arc length control signal La becomes apparent. The arc length returns to the original set value in a short time. Similarly, even if the cleaning width sharply fluctuates and widens at time t3, and the apparent arc length is instantaneously shortened, the apparent arc length is reduced to the original set value in a short time by the arc length control of the present invention. Return to.

As described above, even if the cleaning width suddenly fluctuates during welding, the apparent arc length hardly changes by the arc length control method of the present invention. Obtainable.

FIG. 10 described above shows a case where the arc length control method of the present invention is applied to a pulse arc welding power supply device of a consumable electrode gas shielded arc welding power supply device.
Further, the arc length control method of the present invention can also be applied to a DC arc welding power supply device of a consumable electrode gas shielded arc welding power supply device. Hereinafter, this case will be described.

FIG. 13 is a block diagram showing a circuit configuration of a DC arc welding power supply device for implementing the arc length control method of the present invention. Hereinafter, each circuit block will be described with reference to FIG. 10, but the same reference numerals are given to the same circuit blocks as in FIG. FIG.
Circuit blocks different from 0 are an arc length error signal integration circuit VSL and a voltage error amplification circuit EAV, which are indicated by dotted lines. The block diagram of FIG. 10 and the block diagram of FIG. 13 are the same as those of the circuit block relating to the arc length control of the present invention, and the difference is that the welding power supply device of FIG. 10 has a constant current characteristic. On the other hand, the welding power supply device of FIG. 13 has a constant voltage characteristic.

The arc length error signal integration circuit VSL receives the arc length error amplification signal ΔLa as an input, integrates the signal, and outputs a voltage setting signal Vs. The voltage error amplifier circuit EAV amplifies an error between the welding voltage detection signal Vd serving as a feedback signal and the voltage setting signal Vs serving as a target value, and outputs a voltage error amplified signal Eav. As described above, output control is performed by the output control circuit 6 using this signal as a control signal.

Further, as a typical example in which the apparent arc length changes rapidly during welding, the case where the cleaning width changes as described above with reference to FIG. 12 has been described. However, when the apparent arc length changes rapidly during welding,
In addition to the above, there are the following cases. That is, in the spray transfer of pulse arc welding or the globule transfer of DC arc welding, when the apparent arc length changes suddenly due to an instantaneous short circuit between the droplet and the workpiece to be welded, which occurs occasionally when the droplet transfers. There is. Even in such a case, according to the arc length control method of the present invention, it is possible to suppress the change in the apparent arc length in a short time and return to the original state, and thus always obtain good welding quality of the workpiece. be able to.

[0086]

According to the arc length control method of the present invention, the arc length of the instantaneous value can be calculated. Therefore, only by setting the arc length set value to an appropriate value, the arc length control method is always appropriate regardless of various welding conditions. A long arc length can be maintained, and as a result, good welding quality of the workpiece can be obtained. The appropriate value of the arc length setting value can be easily set since it becomes a substantially constant value corresponding to a welding method such as pulse arc welding or DC arc welding as described above.

Further, according to the arc length control method of the present invention, the instantaneous arc length can be calculated, so that the response speed of the feedback control system becomes very fast, and an unstable factor such as an arc phenomenon and a mechanical failure are generated. With respect to a rapid change in the arc length during welding caused by a stability factor or the like, the change can be suppressed in a short time and the original state can be restored. Therefore, the proper arc length can always be maintained,
Good welding quality of the workpiece can be obtained.

The arc length control method of the present invention can be used for all types of consumable electrode gas shield arc welding such as pulse arc welding and DC arc welding. In particular, in spray transfer welding of pulse arc welding or globule transfer welding of direct current arc welding, it is possible to suppress a rapid change in the arc length due to an instantaneous short circuit caused by the transfer of droplets. Welding quality can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an arc generating unit for explaining main terms.

FIG. 2 is a block diagram showing a configuration of an average arc length calculation circuit CLA for implementing a conventional average arc length calculation method.

FIG. 3 is a block diagram showing a circuit configuration of a consumable electrode gas shielded arc welding power supply for implementing a conventional voltage setting automatic control method using an average arc length calculation circuit CLA.

FIG. 4 is a timing chart of each signal in the block diagram of the conventional pulse arc welding power supply device described in FIG. 3;

FIG. 5 is a diagram showing a time change of an average arc length calculation signal at the time of arc start to show the effect of the voltage control automatic control method of the related art.

FIG. 6 is a diagram showing an average arc length calculation signal at the time of arc start under the same welding conditions as in FIG. 5 in order to explain the problem to be solved by the present invention of the prior art voltage setting automatic control method. It is a figure showing a time change.

FIG. 7 is a graph showing changes in an apparent arc length and a true arc length when a cleaning width is changed, in order to explain a problem to be solved by the present invention of a voltage setting automatic control method of the prior art. FIG.

FIG. 8 is a diagram showing a temporal change of an apparent arc length La when the cleaning width fluctuates rapidly during welding using the conventional pulse arc welding power supply device shown in FIG. 3; .

FIG. 9 is a block diagram showing a configuration of an arc length calculation circuit CL for implementing the arc length calculation method of the prior application.

FIG. 10 is a circuit block diagram of a consumable electrode gas shielded arc welding power supply for implementing the arc length control method of the present invention using the arc length calculation circuit CL.

FIG. 11 is a diagram showing a time change of an arc length calculation signal at the time of an arc start in order to show an effect of the arc length control method of the present invention in comparison with FIG. 6 in a conventional technique.

FIG. 12 is an arc length calculation signal for showing the effect of the arc length control method of the present invention when the cleaning width fluctuates rapidly during welding in comparison with FIG. 8 in the prior art. It is a time change figure.

FIG. 13 is a block diagram showing a circuit configuration of a DC arc welding power supply device for implementing the arc length control method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Welding wire 1a Welding wire tip 2 Workpiece 2a Weld pool 4 Welding torch 4a Contact tip 5a Feeding roll of wire feeder 6 Output control circuit a, b, c constant CL Arc length calculation circuit CLA Average arc length Calculation circuit CZ1, CZ2 Cleaning width DLX Wire protrusion length change calculation circuit DX Wire protrusion length addition calculation circuit EAI Current error amplification circuit Eai Current error amplification signal EAL Arc length error amplification circuit EAV Voltage error amplification circuit EL Arc length error amplification circuit IB Base current setting circuit Ib Base current (setting signal) ID Welding current detection circuit Id Welding current detection signal IDA Average welding current smoothing circuit Ida Average welding current detection signal IP Peak current setting circuit Ip Peak current (setting signal) Is Current setting signal Iw , Iw (n) welding current (detected value) Iwa Average welding current (detected value) k1, k2 Constant L0, L1 (Average) Initial value of arc length calculation signal La, La (n) Arc length (calculated value / calculated signal) LA Arc length calculation circuit La1 to La3 Apparent Arc length (calculation signal) LAA average arc length calculation circuit Laa average arc length (calculation value / calculation signal) LAF arc length filter circuit Laf arc length filter signal LAS average arc length setting circuit Las average arc length setting signal Lb1 True arc length LS Arc length setting circuit Ls Arc length setting signal Lw Distance between tip and workpiece Lx, Lx (n) Wire protrusion length (calculated value) Lx (n-1) Previous protrusion length (calculated value) Lx0 Initial wire protrusion length Value LXA Average wire overhang length calculation circuit Lxa Average wire overhang length (calculated value) MM Mono multivibrator Mm Switching signal Rx Unit length of welding wire Ripple resistance SW switching circuit T1 to T4 Pulse period t1 to t7 Time Tp Peak current conduction time (setting signal) TP Peak current conduction time setting circuit VA Arc voltage calculation circuit Va, Va (n) Arc voltage (calculation value) VAA Average arc voltage calculation circuit Vaa Average arc voltage (calculated value) VD welding voltage detection circuit Vd welding voltage detection signal VDA welding voltage smoothing circuit Vda average welding voltage detection signal VDF voltage filter circuit Vdf voltage filter signal VF V / F conversion circuit Vf frequency Signal VFL Arc length V / F conversion circuit VS Error signal integration circuit Vs Voltage setting signal Vs0 Initial setting value of voltage setting signal VSL Arc length error signal integration circuit Vw, Vw (n) Welding voltage (detection value) Vwa Average welding voltage ( VX Wire protrusion voltage calculation circuit Vx, Vx (n) Wire protrusion voltage (calculation) VXA Average wire protrusion voltage calculation circuit Vxa Average wire protrusion voltage (calculated value) Wf, Wf (n) Feeding speed (detected value) Wfa Average feeding speed (detected value) WM Melting speed calculating circuit Wm, Wm ( n) Melting speed (calculated value) WS Feeding speed setting circuit Ws Feeding speed setting signal ΔL Arc length error amplification signal ΔL12 Apparent arc length change length ΔLa Arc length error amplification signal ΔLx Wire extension length change ΔV Voltage error amplification signal

Claims (10)

[Claims] In an arc length control method for consumable electrode gas shielded arc welding, a welding current value Iw and a welding voltage value Vw during welding are repeatedly detected, and a feeding speed Wf is repeatedly detected or set, and the n-th welding current value Iw and the welding speed value are repeatedly determined. The welding current value Iw detected at the n-th time and the welding voltage value V detected at the n-th time
w and the n-th detection or a preset feed speed W
f, an n-th melt speed calculation step for outputting a melt speed calculation value Wm; an n-th wire protrusion length change calculation step for outputting a wire protrusion length change value ΔLx; , A wire overhang length addition process of outputting the wire overhang length calculation value Lx, an n-th wire overhang voltage calculation process of outputting the wire overhang voltage calculation value Vx, and an n-th arc voltage calculation value Va. The arc voltage calculation process to be output and the n-th arc length calculation value La
The arc length calculating step of outputting an arc length calculating step of outputting the n-th arc length calculating value La, using the n-th arc length calculating value La as a feedback signal, and setting a predetermined arc length setting An arc length control method for controlling output of a welding power supply device by feedback control using a value Ls as a target value and maintaining an arc length during welding at a target value. 2. A method for controlling the arc length of consumable electrode gas shielded arc welding, wherein the welding current value Iw and the welding voltage value Vw during welding are repeatedly detected and the feed speed Wf is repeatedly detected or preset, and At the time of the first calculation, the welding current value Iw detected the second time and the previously calculated wire protrusion length calculation value Lx (n-1) which is a preset wire protrusion length initial value Lx0 are input, and the n-th melting speed is calculated. A melting speed calculating step of outputting a calculated value Wm, and an n-th wire projection length change by inputting the n-th detected or preset feeding speed Wf and the n-th melting speed calculated value Wm. And calculating the n-th wire protrusion length change amount calculation value ΔLx and the previous wire protrusion length calculation value Lx (n-1) as inputs. The first wa A wire overhang length addition process for outputting an ear overhang length calculation value Lx, and an n-th wire over-run, with the n-th wire overhang length calculation value Lx and the n-th detected welding current value Iw as inputs. A wire protrusion voltage calculation process for outputting a protrusion voltage calculation value Vx; and an n-th wire protrusion voltage calculation value, wherein the n-th detected welding voltage value Vw and the n-th wire protrusion voltage calculation value Vx are input. An arc voltage calculation step of outputting an arc voltage calculation value Va; and the n-th arc voltage calculation value Va
And the n-th detected welding current value Iw as an input, and an n-th arc length calculation step of outputting an n-th arc length calculation value La.
The output of the welding power supply device is performed by feedback control in which the arc length calculation value La for the third time is output, the arc length calculation value La for the n-th time is used as a feedback signal, and the preset arc length set value Ls is set as a target value. An arc length control method for maintaining an arc length during welding at a target value. 3. An arc length control method for consumable electrode gas shielded arc welding, wherein a welding current value Iw and a welding voltage value Vw during welding are repeatedly detected and a feed speed Wf is repeatedly detected or preset, and At the time of the first calculation, the welding current value Iw detected the second time and the previously calculated wire protrusion length calculation value Lx (n-1), which is a preset wire protrusion length initial value Lx0, are input, and a predetermined constant α and β
Thus, the n-th melting speed calculation value Wm = α · Iw + β
· Lx (n-1) · Iw and ^{2. The} term melting rate calculation process, the said n-th detection or feeding speed Wf the preset n-th
The n-th wire protrusion length change amount calculation value ΔLx = (Wf−Wm) · ΔT is calculated by a preset constant ΔT with the melt speed calculation value Wm as an input. The n-th wire protrusion length change amount calculation value ΔLx and the previous wire protrusion length calculation value Lx (n-1) are input, and
The n-th wire protrusion length calculation value Lx = Lx (n-1) + ΔL
x, a wire overhang length calculation process, and the n-th wire overhang length calculation value Lx and the n-th detected welding current value Iw, and a preset constant Rx
As a result, the n-th wire protrusion voltage calculation value Vx = R
a wire protruding portion voltage calculating process of x · Lx · Iw;
The n-th welding voltage value Vw detected and the n-th wire protrusion voltage calculation value Vx are input to the n-th welding voltage value Vw.
The arc voltage calculation process in which the arc voltage calculation value Va at the time of Va = Vw−Vx, and the arc voltage calculation value Va at the n-th time
And the welding current value Iw detected at the n-th time as inputs, and the n-th arc length calculation value La = (Va−a−c · Iw) / (b + d ·) based on preset constants a to d.
Iw), the n-th arc length calculation value La is output by an arc length calculation process including an arc length calculation process, and the n-th arc length calculation value La is used as a feedback signal, and a preset arc length setting is performed. An arc length control method for controlling the output of a welding power supply device by feedback control using a value Ls as a target value to maintain an arc length during welding at a target value. 4. A consumable electrode pulse in which a peak current is supplied during a peak current supply time and a base current is supplied thereafter until the end of a pulse cycle, and a peak current supply and a base current supply are alternately repeated. In the arc length control method for arc welding, the feedback control may be performed using the n-th control.
The second arc length calculation value La is used as a feedback signal,
4. The feedback control according to claim 1, wherein the arc length set value Ls is a target value, and feedback control is performed to control the output of the welding power supply device using the pulse cycle, the peak current conduction time or the peak current as a control signal. The arc length control method to be described. 5. An arc length control method for consumable electrode DC arc welding having a constant voltage characteristic corresponding to a voltage setting value, wherein the feedback control uses the n-th arc length calculation value La as a feedback signal, 4. The arc length according to claim 1, wherein the arc length is set as a target value, and feedback control is performed using the voltage set value as a control signal to control the output of the welding power supply device to obtain a constant voltage characteristic. 5. Control method. 6. A welding current detection circuit for repeatedly detecting a welding current value Iw, a welding voltage detection circuit for repeatedly detecting a welding voltage value Vw, and a feeding speed detection circuit or a feeding speed for repeatedly detecting a feeding speed Wf. A feed speed setting circuit for setting Wf in advance, and the welding current value I detected at the n-th time.
w, a melting speed calculating step of outputting the n-th melting speed calculated value Wm by using the n-th detected welding voltage value Vw and the n-th detected or preset feed speed Wf as inputs, Calculated value Δ of the nth wire extension change
Calculating a wire protrusion length change for outputting Lx;
A wire overhang length addition operation process of outputting a wire overhang length calculation value Lx for the third time, a wire overhang voltage calculation process of outputting an n-th wire overhang voltage calculation value Vx, and an n-th arc voltage calculation value Va , An arc length calculation circuit that outputs an n-th arc length calculation value La, and an arc length calculation circuit that outputs an arc length setting value Ls. n
The second arc length calculation value La is used as a feedback signal,
A consumable electrode gas for controlling the output of the welding power supply device by the output signal of the feedback control circuit to maintain the arc length during welding at the target value. Power supply for shielded arc welding. 7. A welding current detection circuit for repeatedly detecting a welding current value Iw, a welding voltage detection circuit for repeatedly detecting a welding voltage value Vw, and a feeding speed detection circuit or a feeding speed for repeatedly detecting a feeding speed Wf. A feed speed setting circuit for setting Wf in advance, and a welding current value Iw detected at the n-th time.
When the first calculation is performed, a melt speed is output by inputting a previously calculated wire protrusion length Lx (n-1), which is a preset wire protrusion length initial value Lx0, and outputting an nth melt speed calculation value Wm. The calculation process, the n-th detected or preset feed speed Wf and the n-th melt speed calculation value Wm
A wire overhang length change calculation process of outputting an n-th wire overhang length change operation value ΔLx as an input;
The n-th wire protrusion length change amount calculation value ΔLx and the previous wire protrusion length calculation value Lx (n-1) are input, and
An n-th wire overhang length calculation process for outputting a wire overhang length calculation value Lx; the n-th wire overhang length calculation value Lx and the n-th detected welding current value Iw
, An n-th wire protrusion voltage calculation process of outputting an n-th wire protrusion voltage calculation value Vx, the n-th welding voltage value Vw detected and the n-th wire protrusion voltage calculation value Vx and an arc voltage calculation step of outputting an n-th arc voltage calculation value Va, and an n-th arc voltage calculation value Va and the n-th detected welding current value Iw as inputs. An arc length calculating circuit for outputting an n-th arc length calculation value La, an arc length setting circuit for outputting an arc length setting value Ls, and an n-th arc length calculation value La And a feedback control circuit that sets the arc length set value Ls as a target value. The output signal of the feedback control circuit outputs the output of the welding power supply device. Consumable electrode gas shielded arc welding power supply to maintain the arc length during welding and controls the target value. 8. A welding current detection circuit for repeatedly detecting a welding current value Iw, a welding voltage detection circuit for repeatedly detecting a welding voltage value Vw, and a feeding speed detection circuit or a feeding speed for repeatedly detecting a feeding speed Wf. A feed speed setting circuit for setting Wf in advance, and the welding current value I detected at the n-th time.
At the time of the first calculation, w and the previously calculated wire protrusion length calculation value Lx (n-1), which is the preset wire protrusion length initial value Lx0, are used as inputs, and the n-th calculation is performed using preset constants α and β.
The second calculated melt speed Wm = α · Iw + β · Lx (n−1) ·
The melting speed calculation process of Iw ² and the n-th detection or predetermined feeding speed Wf and the n-th melting speed calculation value Wm are input, and the n-th melting speed calculation process is performed by a preset constant ΔT. Calculated value ΔLx =
(Wf-Wm) .multidot..DELTA.T, a wire protrusion length change calculation process, and the n-th wire protrusion length change calculation value .DELTA.T
Lx and the previous wire extension length calculation value Lx (n-1) are input, and the nth wire extension length calculation value Lx = Lx (n-
1) The wire overhang length addition process of + ΔLx, and the n-th wire overhang length calculation value Lx and the n-th detected welding current value Iw are input and the n-th wire overhang length calculation process is performed using a preset constant Rx. The wire protrusion voltage calculation value Vx = Rx · Lx · Iw of the wire protrusion voltage calculation process, and the n-th welding voltage value Vw detected and the n-th wire protrusion voltage calculation value Vx are calculated. As an input, the n-th arc voltage calculation value Va = Vw−Vx
Arc voltage calculation process, and the n-th arc voltage calculation value Va and the n-th detected welding current value Iw
, And the n-th arc length calculation value La = (Va−a−c · Iw) according to preset constants a to d.
/ (B + d · Iw), an arc length calculation circuit comprising an arc length calculation process, an arc length setting circuit for outputting an arc length set value Ls, and the n-th arc length calculated value La
And a feedback control circuit that sets the arc length set value Ls as a target value, and controls the output of the welding power supply device by the output signal of the feedback control circuit to set the arc length during welding to the target value. Maintain consumable electrode gas shielded arc welding power supply. 9. A consumable electrode pulse in which a peak current is supplied during a peak current supply time and a base current is supplied thereafter until the end of a pulse cycle, and a peak current supply and a base current supply are alternately repeated. In the arc welding power supply device, the feedback control circuit sets the n-th arc length calculation value La as a feedback signal, sets the arc length set value Ls as a target value, and calculates the pulse cycle, peak current conduction time or peak current. 9. The consumable electrode gas shielded arc welding power supply according to claim 6, which is a feedback control circuit that performs output control of the welding power supply as a control signal. 10. A consumable electrode DC arc welding power supply having a constant voltage characteristic corresponding to a voltage set value, wherein the feedback control circuit sets the arc length setting value La as a feedback signal, 9. The consumable electrode gas shield according to claim 6, wherein the feedback control circuit is a feedback control circuit for controlling the output of the welding power supply device to a constant voltage characteristic by setting the value Ls as a target value and using the voltage set value as a control signal. Arc welding power supply.