JP2003170272A - Arc start controlling method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate a problem of occurrence of unnecessary immediately prior contact arc 3c just before a welding wire and a base material are brought into contact with each other, the extremity of the wire is melted and adhered to the base material to make an arc start inferior in an arc start controlling method in which an initial current Is is given upon discrimination of forwarding motion of a welding wire 1 to the contact state of the welding wire with a base material 2, the welding wire is retracted from the base material and fed, the welding wire is moved away from the base material to generate an initial arc 3a, the welding wire is forwarded and fed again, a regular welding current Ia is supplied to be set to a regular arc 3b. <P>SOLUTION: An output of a welding power supply device is instantly stopped upon discrimination (at a time t2) of occurrence of unnecessary immediately prior contact arc and after the immediately prior arc is eliminated, the output of the welding power supply device is started again after elapsing of a predetermined output stopping time Ts to prevent a melting and adhesion of a welding wire at contact. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arc start control method for consumable electrode arc welding in which a wire feed motor capable of forward and reverse rotation feeds a welding wire forward and backward to a base metal to start an arc. Regarding

[0002]

2. Description of the Related Art A wire feed motor is rotated forward to feed a welding wire forward to a base metal, and when it is determined that the welding wire has come into contact with the base metal, the wire feed motor is rotated backward to feed the welding wire to the base metal. When the welding wire is fed backward from the material and at the same time an initial current of a predetermined small current value is applied, and when the welding wire separates from the base metal and an initial arc occurs due to the above backward feeding, the welding wire is fed forward again and at the same time. Apply a steady welding current,
BACKGROUND ART An arc start control method for consumable electrode arc welding (generally called a retract arc start method) for shifting from an initial arc generation state to a steady arc generation state has been conventionally known. Hereinafter, this conventional arc start control method will be described with reference to the drawings.

FIG. 1 is a block diagram of a conventional arc welding apparatus. Hereinafter, description will be given with reference to FIG. When the welding start signal St is input from the welding start circuit ST provided outside, the welding power supply device PS outputs the welding voltage Vw and the welding current Iw for generating the arc, and also supplies the welding wire 1. And outputs a feed control signal Fc for controlling the wire feeding motor WM to the wire feeding motor WM. The welding wire 1 is fed by the feeding roll 5 directly connected to the wire feeding motor WM.
It is fed through the welding torch 4. Wire feeding motor W
When M rotates forward, the welding wire 1 is fed forward to the base material 2, and when it rotates backward, the welding wire 1 is fed backward in a direction away from the base material 2. The welding voltage Vw output from the welding power source PS is supplied to the welding wire 1 by the contact tip 4a attached to the tip of the welding torch 4. When the welding wire 1 and the base material 2 are in a contact (short circuit) state or an arc 3 generation state, the welding current Iw is applied. On the other hand, when the welding wire 1 and the base material 2 are separated from each other and no arc 3 is generated, the welding voltage Vw becomes the maximum no-load voltage Vnl and the welding current Iw.
Does not energize. The shortest distance between the tip of the welding wire 1 and the base material 2 is the wire tip-base material distance Lw [mm].
Therefore, the distance Lw between the tip of the wire and the base material during the generation of the arc 3 becomes substantially equal to the arc length.

FIG. 2 is a timing chart of each signal of the above welding apparatus. The same figure (A) shows the welding start signal St
4B shows the time change of the feed control signal Fc, and FIG. 7C shows the time change of the short circuit judgment signal Sd for judging the contact state between the welding wire and the base metal. , (D) shows the time change of the welding voltage Vw, and (E) in the same figure.
Shows the time change of the welding current Iw, (F) of the same figure shows the time change of the wire tip-base metal distance Lw, (G1) of the same figure.
(G5) shows the feeding state of the welding wire at each time. Hereinafter, description will be given with reference to FIG.

Time period from time t1 to t2 (forward feed period) At time t1, when the welding start signal St is input (High level) as shown in FIG. As described above, the feed control signal Fc becomes a positive initial feed rate setting value Fsi, and the welding wire 1 is fed forward to the base material 2 at the initial feed rate, as shown in FIG. . When the feeding control signal Fc has a positive value, it is forward feeding, and when it is negative, it is backward feeding. The external characteristics of the welding power source device during the period from time t1 to t4 are output-controlled to be a constant current characteristic or a drooping characteristic in order to pass an initial current Is described later. However, during the period from time t1 to t2, the welding wire 1 and the base material 2 are in an unloaded state as shown in FIG. The welding voltage Vw becomes the no-load voltage Vnl, and the initial current Is does not flow, as shown in FIG. On the other hand, as shown in FIG. 6F, the wire tip / base material distance Lw gradually decreases with the lapse of time due to the forward feeding.

Period from time t2 to t3 (reverse feeding period) At time t2, when the welding wire 1 comes into contact with the base material 2 by the forward feeding described in the above item (G2), the same figure (G2) As shown in D), the value of the welding voltage Vw changes to a predetermined reference voltage value Vt1 [V] or less, so that the short circuit determination signal Sd goes to a high level (short circuit) as shown in FIG. Change. In response to this, as shown in FIG. 7B, the feed control signal Fc becomes the negative backward feed speed setting value Fsr, and the welding wire is backward fed at the backward feed speed from the base metal. It At the same time, as shown in FIG.
Initial current I of small current value due to constant current characteristic or drooping characteristic
s is energized. The value of the initial current Is is set to a small current value of about several [A] to several tens [A]. On the other hand, during this period, the welding wire is fed backward, but in order to feed backward the delay time for reversing the wire feeding motor WM and the play caused by the bending of the welding wire in the welding torch. Due to the lag time, the welding wire and the base metal remain in contact. Therefore, as shown in FIG. 4F, the wire tip-base material distance Lw remains 0 [mm] during this period.

Period from Time t3 to t4 (Reverse Feeding Period) Immediately after time t3, when the welding wire 1 and the base material 2 are separated by the backward feeding as described in the above item (G3), Initial arc 3a through which the initial current Is of
Occurs. When the initial arc 3a occurs, the same figure (D)
As shown in, the welding voltage Vw has a voltage value that exceeds the reference voltage value Vt1 described above, which is proportional to the arc length of the initial arc 3a. For this reason, as shown in FIG. 6C, the short circuit determination signal Sd tends to change to the Low level (non-short circuit) at the time t3, but the predetermined off delay time Tod.
Is provided, it remains at High level (short circuit) until time t4. As a result, as shown in (G4) of the figure, the backward feeding is continued while maintaining the initial arc generation state 3a. Therefore, as shown in FIG. 6F, the wire tip-base metal distance Lw during this period
Becomes progressively longer over time. The reason for providing the above-mentioned off-delay time Tod is that if the re-forward feed described on the next page is started immediately after the generation of the initial arc 3a, the contact state may occur again.

Period after Time t4 (Re-forward Feeding Period) At time t4, as shown in FIG. 7C, the short circuit determination signal Sd is Hi after the off delay time Tod has elapsed.
When changing from gh level to Low level, the same figure (B)
As shown in, the feed control signal Fc becomes a positive steady feed rate set value Fs, and the welding wire is fed forward again at the steady feed rate. At the same time, since the external characteristic of the welding power source device is output-controlled to the constant voltage characteristic corresponding to the predetermined voltage setting value Vs, as shown in FIG.
Becomes a voltage value corresponding to this voltage setting value Vs, and
As shown in (E) of the same figure, the steady welding current Ia corresponding to the above-mentioned steady feeding speed is supplied. By this energization,
The initial arc 3a shown in (G4) of the figure shifts to the steady arc 3b shown in (G5) of the figure, and as shown in (F) of the figure, the wire tip / base metal distance Lw is also set to the above voltage setting. The steady arc length corresponds to the value Vs.

[0009]

FIG. 3 is a timing chart corresponding to FIG. 2 described above for explaining the problem to be solved by the prior art. Each signal of (A) to (G4) in the figure is the same as that in FIG. Hereinafter, description will be given with reference to FIG.

As in the case of FIG. 2, at time t1,
As shown in FIG. 7A, the welding start signal St is input (H
High level), the feeding control signal Fc becomes a positive initial feeding speed setting value Fsi as shown in FIG. 7B, and the welding wire 1 is Base material 2
Is fed forward at the initial feed rate. At the same time, as in the case of FIG. 2, the external characteristics of the welding power supply device are output-controlled to the constant current characteristics or the drooping characteristics, but as shown in FIG.
Since the welding voltage Vw is in the unloaded state, the unloaded voltage Vnl
Becomes

Due to the forward feeding described above,
As shown in (F) of the figure, the distance Lw between the wire tip and the base material
Becomes shorter and shorter. Then, at time t11, when the tip of the wire and the base material come very close to each other and are in a state of being in contact with each other, as shown in FIG.
Therefore, the arc 3c may occur immediately before the contact. When the arc 3c just before the contact occurs, the initial current Is is conducted as shown in FIG. The forward feed is continued with the arc 3c immediately before contact being generated, and when the welding wire and the base metal contact each other at time t2, the arc 3c immediately before contact is extinguished. At this time, since the wire tip portion and the base material 2 are melted by the arc 3c immediately before contact during the period from time t11 to t2, as shown in FIG.
When the contact is made and the arc 3c immediately before the contact disappears, the tip of the wire may be welded to the base material 2 (hereinafter, this phenomenon is referred to as welding at the time of contact).

On the other hand, as shown in FIG.
At, the short circuit determination signal Sd changes to High level (short circuit), and the backward feeding of the welding wire is started. However, the initial arc 3a never occurs because the tip of the wire is welded to the base material and the welding wire and the base material are not separated. Therefore, even at a time t21 after a long time has elapsed from the time t2, the feed control signal Fc shown in (B) of the figure remains the backward feed speed setting value Fsr, and the short circuit shown in (C) of the figure occurs. The determination signal Sd remains at the high level (short circuit), the welding voltage Vw shown in (D) of the figure remains a low value of about several [V], and the welding current Iw shown in the (E) of FIG. The current value Is remains as it is, and FIG.
The distance Lw between the wire tip and the base material shown in (4) remains 0 [mm], and the welding wire 1 is still welded to the base material 2 as shown in FIG. For this reason, arc start cannot be performed, resulting in arc start failure.

The above-mentioned welding at the time of contact is likely to occur when the material of the base material is steel or stainless steel, and is less frequent when it is aluminum or its alloy. Also,
In the case of steel or stainless steel, the initial current Is value is about 5
When it is more than [A], welding at the time of contact is likely to occur frequently. Furthermore, at the time t11 described above, when the arc 3c immediately before the contact occurs and the initial current Is is conducted, an overshoot due to a response delay of the feedback control system of the welding power source device occurs, and several tens of [A] or more are generated. Since the overshoot current Ip is applied, the melting of the tip portion of the welding wire is promoted, and welding during contact is likely to occur. Therefore, it is difficult to prevent welding at the time of contact with the conventional technology.

Therefore, the present invention provides an arc start control method capable of surely performing a good arc start without causing the above-mentioned welding at the time of contact.

[0015]

The first aspect of the present invention is shown in FIGS.
As shown in FIG. 4, when the welding start signal St is input to the welding power supply device, the output of the welding power supply device is started and the forward feeding of the welding wire to the base metal is started. When it is determined that the arc state 3c or the contact state with the base material is As, the output of the welding power supply device is immediately stopped, the backward feeding of the welding wire from the base material is started, and the welding power supply is supplied. When a predetermined output stop time Ts elapses from the output stop of the device, the output is restarted and the initial current Is of a small current value is supplied, and by this backward feeding, the welding wire is separated from the base metal and the initial arc 3a is generated. After that, the re-advancing feed of the welding wire is started, and a steady welding current is applied to the initial arc generation state 3a.
This is an arc start control method for consumable electrode arc welding, in which the transition from the normal to the steady arc generation state 3b is performed.

A second invention is, as shown in FIGS. 6 to 7, an arc start control method for starting the backward feeding of the welding wire described in the first invention after the output stop time Ts has elapsed.

A third aspect of the present invention, as shown in FIGS. 8 to 9, performs the backward feeding of the welding wire according to the first aspect of the invention with a predetermined backward feeding delay time Td after the output of the welding power source device is stopped. This is an arc start control method that starts after a lapse of time.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments 1 to 3 will be described below as examples of embodiments of the present invention with reference to the drawings. [Embodiment 1] According to the invention of Embodiment 1, when a welding start signal is input, the welding power source device starts to output and the forward feeding of the welding wire to the base metal is started. When it is determined that an arcing state or a contact state has occurred between the base metal and the base metal, the output of the welding power supply device is immediately stopped, the backward feeding of the welding wire from the base metal is started, and the welding power supply device is After a predetermined output stop time Ts has elapsed from the stop of the output of No. 1, the output is restarted and an initial current of a small current value is supplied, and by this backward feeding, the welding wire separates from the base metal and welding is performed after the initial arc occurs. This is an arc start control method for starting re-advance feeding of the wire and passing a steady welding current to smoothly shift from the initial arc generation state to the steady arc generation state. That is, it is determined that the welding wire is very close to the base metal due to the forward feed, and the arc immediately before the contact is generated or is contacted, and the output of the welding power supply device is immediately output during the output stop time Ts. Stop. This immediately extinguishes the arc just before the contact, which prevents welding at the time of contact. Also, the reason why the output is stopped when the welding wire contacts the base metal without the arc just before the contact occurring is that if the contact state is incomplete even after the contact once, the arc just before the contact occurs and the welding occurs. This is to prevent this from occurring. Output stop time T
The value of s is set to an appropriate value according to various welding conditions such as the type of welding wire (material, diameter, etc.), type of wire feeding motor, joint shape, welding posture, and the like. Hereinafter, the invention of the first embodiment will be described with reference to the drawings.

FIG. 4 is a block diagram of a welding power supply device PS for carrying out the invention of the first embodiment. Hereinafter, description will be given with reference to FIG. The output control circuit INV is a commercial power source (3
Phase 200 [V] etc.) as an input, and a drive signal D described later.
Output control such as inverter control and thyristor control is performed according to v, and welding voltage Vw and welding current Iw suitable for welding
Is output.

The welding start circuit ST is a torch switch of a welding torch, a welding process control device, etc., and is high during welding.
The welding start signal St which becomes the h level is output. The voltage detection circuit VD detects the welding voltage Vw, and detects the voltage detection signal Vw.
Output d. The short circuit determination circuit SD determines that the voltage detection signal Vd is the predetermined reference voltage value V as described above with reference to FIG.
When it is t1 or less, the short circuit determination signal Sd which becomes High level is output. The arc short circuit determination circuit AS outputs a high level arc short circuit determination signal As when the voltage detection signal Vd is equal to or lower than a predetermined second reference voltage value Vt2 (arc / short circuit state).

The initial feeding speed setting circuit FSI outputs a predetermined initial feeding speed setting signal Fsi. The second logic NOT circuit NOT2 logically inverts the arc short circuit determination signal As and outputs a switching signal Not2. The feeding speed switching circuit SF is connected to the a side until the switching signal Not2 changes from the high level (no load state) to the low level (arc / short circuit state), and the initial feeding speed setting signal Fsi is fed. Is output as the feed speed control setting signal Fsc, and H
After changing from the high level to the low level, it switches to the b side and outputs a backward / steady feeding speed setting signal Sr described later as a feeding speed control setting signal Fsc. The backward feed speed setting circuit FSR outputs a predetermined backward feed speed setting signal Fsr. The steady feeding speed setting circuit FS outputs a predetermined steady feeding speed setting signal Fs. In the reverse / steady feed speed switching circuit SR, the short circuit determination signal Sd is H
Until the high level (short circuit) changes to the low level (non-short circuit), the reverse feed speed setting signal Fsr is connected as the a side and is output as the reverse / steady feed speed setting signal Sr. After changing to the level, it switches to the b side and outputs the above-mentioned steady feed speed setting signal Fs as the backward / steady feed speed setting signal Sr. The feed control circuit FC, when the welding start signal St is at the high level (start), feeds the feed speed control setting signal Fsc.
The feeding control signal Fc for feeding the welding wire at a speed corresponding to is output to the wire feeding motor WM.

The voltage setting circuit VS outputs a predetermined voltage setting signal Vs. The initial current setting circuit ISI outputs a predetermined initial current setting signal Isi. The voltage error amplification circuit EV includes the voltage setting signal Vs and the voltage detection signal V
The error with d is amplified and the voltage error amplified signal Ev is output. By the feedback control by the voltage error amplification circuit EV, the external characteristic of the welding power source device becomes a constant voltage characteristic for passing a steady welding current. Current detection circuit ID
Detects the welding current Iw and outputs a current detection signal Id. The current error amplification circuit EI amplifies the error between the initial current setting signal Isi and the current detection signal Id and outputs the current error amplification signal Ei. This current error amplifier circuit EI
By the feedback control by, the external characteristic becomes a constant current characteristic or a drooping characteristic for passing the initial current Is. The external characteristic switching circuit SP uses the short circuit determination signal Sd.
Is from High level (short circuit) to Low level (non-short circuit)
Until it changes to, it is connected to the a side and outputs the current error amplified signal Ei as the error amplified signal Ea. After changing from the High level to the Low level, it switches to the b side and the voltage error amplified signal Ev is error amplified. Output as signal Ea.

The output stop time timer circuit TS outputs a high level for a predetermined time from the time when the arc short circuit determination signal As changes from a low level (no load state) to a high level (arc / short circuit state). The stop time signal Ts is output. The logical NOT circuit NOT logically inverts the output stop time signal Ts and logically negates the signal N.
Output ot. The logical product circuit AND performs a logical product of the logical negation signal Not and the welding start signal St and outputs an output permission signal On. The drive circuit DV outputs the drive signal Dv in accordance with the error amplification signal Ea when the output permission signal On is at the high level (output permission), and is Low.
At the level (output prohibited), the drive signal Dv is not output. As a result, the output of the welding power supply device is stopped during the output stop time Ts.

FIG. 5 is a timing chart of each signal of the above welding power source device. The same figure (A) shows the time change of the welding start signal St, and the same figure (B) shows the feed control signal Fc.
The time change of the short circuit determination signal Sd is shown in the same figure, the time change of the arc short circuit determination signal As is shown in the same figure, and the output permission signal On of FIG. FIG. 6F shows the change over time of the welding voltage Vw, FIG. 9G shows the change over time of the welding current Iw, and FIG. 9H shows the change of the wire tip / base metal distance Lw. The time change is shown, and (I1) to (I5) of the same figure show the feeding state of the welding wire at each time. Hereinafter, description will be given with reference to FIG.

When the welding start signal St is input (High level) as shown in (A) of the figure at the time point t1 of the period from time t1 to t11, the feed control is performed as shown in (B) of the figure. The signal Fc has a positive initial feed rate set value, and the welding wire 1 is fed forward to the base material 2 at the initial feed rate, as shown in FIG.
During this period, since the welding wire 1 and the base material 2 are in an unloaded state as shown in (I1) of the figure, the welding voltage Vw becomes an unloaded voltage as shown in (F) of the figure. , The initial current Is does not flow, as shown in FIG. On the other hand, as shown in FIG. 3H, the wire tip / base material distance Lw gradually decreases with the lapse of time due to forward feeding.

At the time t11 between the times t11 and t3, the forward feed of the above item causes the tip of the welding wire and the base metal to come very close to each other, and an arc 3c immediately before contact is generated as shown in (I2) of the same figure. Then, as shown in FIG. 7F, the welding voltage Vw drops to an arc voltage value lower than the no-load voltage value and becomes lower than the second reference voltage value Vt2 predetermined at time t2. In response to this, as shown in FIG. 4D, the arc short circuit determination signal A
When s changes to the High level (arc / short circuit state), the output permission signal On changes from time t2 to time t when a predetermined output stop period Ts elapses, as shown in FIG.
During the period up to 3, it becomes Low level (output prohibited). That is, during a very short arc period just before contact between times t11 and t2, a welding current of a very small value is supplied as shown in FIG. Since it stops, energization stops. The arc generation period immediately before contact between times t11 and t2 is very short and only a very small value of welding current is passed, so the tip of the welding wire and the base metal do not melt. Therefore, as shown in (I3) of the same figure, even if the welding wire and the base metal come into contact with each other immediately after time t2, the tip of the welding wire does not weld to the base metal.

Further, as shown in FIG. 3D, time t2
When the arc short circuit determination signal As changes from the Low level to the High level, the feeding control signal Fc becomes a negative backward feeding speed setting value as shown in FIG. The material is fed backward at the backward feeding speed. However, due to the delay time for reversing the wire feeding motor and the delay time for backward feeding the play due to the bending of the welding wire in the welding torch, as shown in FIG. Until time t4, the welding wire and the base metal remain in contact with each other. Also, at time t2,
When the output of the welding power supply device is stopped, the value of the welding voltage Vw becomes approximately 0 [V], which is lower than the reference voltage value Vt1, as shown in FIG. like,
The short circuit determination signal Sd changes to High level (short circuit).

When the output stop time Ts elapses in the period t3 from the time t3 to t4, the output permission signal On changes to the high level (output permission) as shown in FIG. Starts output again. As a result, as shown in FIG.
The overshooting initial current is applied, and the welding voltage Vw becomes a short circuit voltage value of about several [V] as shown in FIG. At this time, even if an overshoot current is applied, since the welding wire and the base material are in contact with each other, no arc is generated, the contact portion is not melted, and no welding occurs.

The operation in the period from time t4 to t5 and the subsequent periods is the same as that of the above-described conventional technique. Immediately after the time t4, as shown in (I4) of the same figure, the welding wire 1 and the base metal 2 are removed by the backward feeding described in the above section.
When and are separated from each other, an initial arc 3a in which an initial current flows is generated. When the initial arc 3a is generated, the welding voltage Vw becomes a voltage value exceeding the reference voltage value Vt1 proportional to the arc length of the initial arc 3a, as shown in FIG. Therefore, as shown in FIG. 7C, the short circuit determination signal Sd tends to change to the Low level (non-short circuit) at time t4, but due to the off-delay time, it remains High until time t5.
It remains at the h level (short circuit). As a result, the backward feeding is continued while maintaining the initial arc generation state.
Therefore, as shown in FIG. 3H, the wire tip-base metal distance Lw during this period gradually increases with the lapse of time.

At time t5 after time t5, as shown in (C) of the figure, the short circuit determination signal Sd is High after the off delay time has elapsed.
When the level is changed to the Low level, as shown in FIG. 7B, the feed control signal Fc becomes a positive steady feed rate set value, and the welding wire is fed forward again at the steady feed rate. . At the same time, since the external characteristic of the welding power source device is output-controlled to a constant voltage characteristic corresponding to the predetermined voltage setting signal Vs, the welding voltage Vw becomes the voltage setting signal Vs as shown in FIG. At a corresponding voltage value, a steady welding current corresponding to the above-mentioned steady feeding speed is supplied, as shown in FIG. As a result, the figure (I4)
The initial arc 3a shown in FIG. 6 shifts to the steady arc 3b shown in FIG. 13 (I5), and the wire tip / base metal distance Lw also corresponds to the voltage setting signal Vs as shown in FIG. The arc length becomes steady.

In the above-mentioned drawing, the case where the arc immediately before contact occurs at time t11 is shown. However, when the welding wire and the base metal contact immediately after time t2 without the arc immediately before contact occurring, the signal The operation is similar to that shown in FIG.

[Embodiment 2] The invention of Embodiment 2 is the same as that of Embodiment 1.
The invention is an arc start control method for starting the backward feeding of the welding wire after the output stop time Ts has elapsed. That is, in the invention of the first embodiment, it is determined that the arc between the welding wire and the base material is in the arc generation state or the contact state immediately before the contact due to the forward feed (time t2 in FIG. 5 described above).
Then, immediately stopping the output of the welding power supply device,
Start backward feeding of the welding wire from the base metal. On the other hand, in the invention of the second embodiment, when it is determined that the welding wire and the base material are in the arc generation state or the contact state immediately before the contact between the welding wire and the base material (time t2 in FIG. 7 described later),
Immediately stop the output of the welding power supply device, and after a predetermined output stop time Ts has elapsed from the output stop time (see FIG.
At the time t3) of, the welding power supply device starts to output,
Start backward feeding of the welding wire from the base metal. Therefore, the forward feeding of the welding wire is continued during the output stop time Ts. In this way, the output stop time T
The reason why the forward feeding of the welding wire is continued even during s is to make the contact state of the welding wire more complete and to prevent arcing and welding at the start of re-output of the welding power supply device. is there. Hereinafter, the invention of the second embodiment will be described with reference to the drawings.

FIG. 6 is a block diagram of a welding power source device for carrying out the invention of the second embodiment. In the figure, the same circuit blocks as those in FIG. 4 described above are designated by the same reference numerals, and the description thereof will be omitted. Hereinafter, a circuit block indicated by a dotted line different from FIG. 4 will be described. The feeding speed switching circuit SF of the second embodiment is connected to the a side until the output stop time signal Ts changes from the High level (output prohibited) to the Low level (output permitted) and outputs the initial feeding speed setting signal Fsi. The feed rate control setting signal Fsc is output, and when the High level is changed to the Low level, it is switched to the b side and the backward / steady feed rate setting signal Sr is output as the feed rate control setting signal Fsc.

FIG. 7 is a timing chart of each signal of the above welding power source device. The signals in (A) to (I5) in the same figure are the same as those in FIG. 5 described above. The operation of each signal is different from that of FIG. 5 in the following points, and the other operations are the same. That is, as shown in FIG. 7B, the feed control signal Fc is the output stop time T determined in advance.
At time t3 when s has elapsed, the value changes to a negative backward feeding speed setting value, and backward feeding of the welding wire is started.

[Third Embodiment] The invention of the third embodiment is the same as the first embodiment.
In the arc start control method, the backward feeding of the welding wire is started after the elapse of a predetermined backward feeding delay time Td after the output of the welding power source device is stopped. That is, in the invention of the third embodiment, when it is determined that the arc between the welding wire and the base material is in the arc generation state or the contact state immediately before the contact due to the forward feeding (time t2 in FIG. 9 described later), the welding is immediately performed. The output of the power supply device is stopped, the output of the welding power supply device is started after the elapse of a predetermined output stop time Ts from this output stop time (time t3 in FIG. 9, which will be described later), and the output stop time is predetermined. After the backward feeding delay time Td has elapsed (time t31 in FIG. 9, which will be described later), backward feeding of the welding wire from the base material is started. Therefore, the forward feeding of the welding wire is continued during the backward feeding delay time Td from the time when the output is stopped. The reason why the forward feeding of the welding wire is continued even during the backward feeding delay time Td is that the contact state of the welding wire is set to a more complete state similarly to the invention of the second embodiment described above. This is to prevent arcing and welding at the start of output, and in addition to setting an appropriate backward feed delay time Td according to the type (material, diameter, etc.) of the welding wire. . Hereinafter, the invention of the third embodiment will be described with reference to the drawings.

FIG. 8 is a block diagram of a welding power source device for carrying out the invention of the third embodiment. In the figure, the same circuit blocks as those in FIG. 4 described above are designated by the same reference numerals, and the description thereof will be omitted. Hereinafter, a circuit block indicated by a dotted line different from FIG. 4 will be described. The backward feeding delay time timer circuit TD has a backward feeding delay time which becomes High level for a predetermined time from the time when the arc short circuit determination signal As changes from Low level (no load state) to High level (arc / short circuit state). The signal Td is output. The feeding speed switching circuit SF of the third embodiment is connected to the a side until the backward feeding delay time signal Td changes from the High level to the Low level, and feeds the initial feeding speed setting signal Fsi. The signal is output as the setting signal Fsc, and after changing from the High level to the Low level, it switches to the b side and moves backward /
The steady feed speed setting signal Sr is fed to the feed speed control setting signal Fsc.
Output as.

FIG. 9 is a timing chart of each signal of the above welding power source device. The signals in (A) to (I5) in the same figure are the same as those in FIG. 5 described above. The operation of each signal differs from that of FIG. 5 in the following points, and the other operations are the same. That is, as shown in FIG. 7B, the feed control signal Fc changes to a negative backward feed speed setting value at the time t31 when a predetermined backward feed delay time Td has elapsed, and welding The backward feeding of the wire is started.

[Effect] FIG. 10 shows the above-described first to third embodiments.
FIG. 3 is a welding ratio comparison chart showing the effect of the invention of FIG. This figure is an example of an experimental result comparing the frequency of occurrence of welding (welding rate) at the time of contact between the conventional technique and the present invention (the invention of Examples 1 to 3). The figure shows the ratio of welding at the time of contact that occurred during 100 arc starts in carbon dioxide arc welding using a mild steel wire with a diameter of 1.2 [mm]. As is clear from the figure, in the prior art, 22% of the welding occurred during contact, but in the present invention, welding did not occur even once during contact.

[0039]

According to the arc start control method of the present invention,
By determining the occurrence of the arc immediately before the contact and immediately stopping the output of the welding power source device, it is possible to prevent the welding at the time of contact, so that it is possible to always obtain a good arc startability. Furthermore, in the inventions of the second and third embodiments, the output of the welding power source device is immediately stopped by determining the occurrence of the arc immediately before the contact, and a predetermined time is set from the output stop time in order to complete the contact state. By continuing the forward feed for a period of time, it is possible to reliably prevent the occurrence of welding due to arc generation during re-output of the welding power supply device.

[Brief description of drawings]

FIG. 1 is a block diagram of a conventional welding device.

FIG. 2 is a timing chart of a conventional welding device.

FIG. 3 is a timing chart for explaining a problem to be solved by the conventional technique.

FIG. 4 is a block diagram of the welding power supply device according to the first embodiment.

FIG. 5 is a timing chart of the welding power source device according to the first embodiment.

FIG. 6 is a block diagram of a welding power supply device according to a second embodiment.

FIG. 7 is a timing chart of the welding power source device according to the second embodiment.

FIG. 8 is a block diagram of a welding power supply device according to a third embodiment.

FIG. 9 is a timing chart of the welding power source device according to the third embodiment.

FIG. 10 is a comparison diagram of welding rates showing the effect of the present invention.

[Explanation of symbols]

1 welding wire 2 base material 3 arc 3a Initial arc 3b Steady arc 3c Arc just before contact 4 welding torch 4a contact tip Feeding roll of 5 wire feeding device AND AND circuit AS arc short circuit determination circuit As arc short circuit discrimination signal DV drive circuit Dv drive signal Ea Error amplified signal EI current error amplifier circuit Ei Current error amplification signal EV voltage error amplifier circuit Ev voltage error amplification signal FC feeding control circuit Fc feed control signal FS steady feed speed setting circuit Fs Steady feeding speed setting (value / signal) FSI initial feeding speed setting circuit Fsi initial feeding speed setting (value / signal) FSR reverse feed speed setting circuit Fsr Reverse feed speed setting (value / signal) Ia Steady welding current ID current detection circuit Id current detection signal Ip overshoot current Is initial current ISI initial current setting circuit Isi initial current setting signal Iw welding current Lw Wire tip-base material distance NOT logic NOT circuit Not logical negation signal NOT2 Second logical NOT circuit Not2 switching signal On output enable signal PS welding power supply SD short circuit determination circuit Sd Short circuit determination signal SF feeding speed switching circuit SP external characteristic switching circuit SR reverse / steady feeding speed switching circuit Sr backward / steady feed speed switching signal ST welding start circuit St welding start signal TD backward feed delay timer circuit Td Reverse feed delay time (signal) Tod Off delay time TS output stop time timer circuit Ts output stop time (signal) VD voltage detection circuit Vd voltage detection signal Vnl no-load voltage VS voltage setting circuit Vs voltage setting (value / signal) Vt1 reference voltage value Vt2 Second reference voltage value Vw welding voltage WM wire feeding motor

Claims (3)

[Claims] 1. When a welding start signal is input to the welding power source device, the welding power source device starts to output and the welding wire is forwardly fed to the base metal, and the welding wire and the mother wire are fed by this forward feeding. When it is determined that an arc or a contact state with the material has been determined, the output of the welding power supply device is immediately stopped and the backward feeding of the welding wire from the base material is started, and the output of the welding power supply device is output. When a predetermined output stop time elapses from the stop, the output is restarted and a small current value of the initial current is applied.By this backward feeding, the welding wire separates from the base metal, and after the initial arc occurs, the welding wire is restarted. An arc start control method for consumable electrode arc welding in which forward feed is started and a steady welding current is passed to smoothly transition from the initial arc generation state to the steady arc generation state. 2. An arc start control method for starting the backward feeding of the welding wire according to claim 1 after the output stop time has elapsed. 3. An arc start control method according to claim 1, wherein the backward feeding of the welding wire is started after a predetermined backward feeding delay time elapses after the output of the welding power source device is stopped.