JP2003103367A - Output control method of pulse arc welding power supply unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an output control method capable of forming an external characteristics having an inclination Ks [V/A] of the proper value in order to improve weldability in a pulse arc welding power supply unit. SOLUTION: The output control method of the pulse arc welding power supply unit that performs welding by forming the external characteristics having the inclination Ks of the proper value by controlling the output of the welding power supply unit so that the welding current average value Iw(n) during a period of time and the welding voltage average value Vw(n) during a period of time in the pulse period Tpb(n) of an nth time during welding can maintain the relationship of Vw(n)=Ks.(Is-Iw(n))+Vs by setting in advance the inclination Ks of the external characteristics and the welding current set value Is and the welding voltage set value Vs.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In consumable electrode pulse arc welding, it is extremely important to maintain the arc length during welding at an appropriate value in order to improve the welding quality such as beautiful bead appearance and uniform penetration depth. is there. Generally, the arc length is determined by the balance between the feed rate of the welding wire and the melting rate. Therefore, if the feed rate during welding is substantially constant, and this feed rate becomes substantially equal to the melting rate that is substantially proportional to the average value of the welding current, the arc length will always be constant. However, the feed rate during welding fluctuates due to fluctuations in the rotation speed of the feed motor, fluctuations in the frictional force in the feed path due to bending of the welding torch, etc. Change. Further, the arc length also changes due to fluctuations in the distance between the tip and the work piece due to hand shake of the welding operator, irregular vibration of the molten pool, and the like. Therefore, in order to suppress changes in the arc length due to these various fluctuations (hereinafter, referred to as disturbance), it is necessary to constantly adjust the melting rate according to the disturbance to suppress changes in the arc length (hereinafter, referred to as arc). Long control).

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

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

A period from time t1 to t2 (base period T
b) During a predetermined base period Tb, as shown in FIG. 7A, a predetermined base current Ib is applied to a low current value of about 20 to 80 [A] to prevent droplet transfer. As shown in FIG. 7B, the welding voltage instantaneous value Vo becomes the base voltage Vb according to the above energization. Further, the time length of the base period Tb is determined by the welding wire feeding speed, material,
It is preset to an appropriate value corresponding to the diameter and the like.

A period from time t2 to t3 (peak period T
p) During the peak period Tp, a predetermined peak current Ip of about 300 to 600 [A] is applied to transfer droplets, as shown in FIG. As shown, the welding voltage instantaneous value Vo becomes the peak voltage Vp according to the above energization.

[0007]

As shown in FIG. 1A, the average value of the welding current instantaneous value Io during one cycle (pulse period Tpb) becomes the one cycle welding current average value Iw, and similarly, in FIG. As shown, one cycle of the welding voltage instantaneous value Vo (pulse cycle Tp
The average value during b) is the one cycle welding voltage average value Vw.
In the pulse arc welding power supply device, as described above,
Output control for maintaining the arc length at an appropriate value is performed as follows. That is, one cycle welding voltage average value Vw
Is represented by the following formula. Vw = (1 / Tpb) · ∫Vo · dt (1) Formula However, the above integration is pulse period Tpb (time t1 to t3)
Do between The time length of the pulse period Tpb is controlled so that the one-cycle welding voltage average value Vw shown in the above equation becomes substantially equal to the welding voltage setting value Vs of the predetermined target value. In addition,
Substituting Vw = Vs into equation (1) and transforming yields the following equation. ∫ (Vs−Vo) · dt = 0 (2) Formula However, the above integration is performed during the pulse period Tpb. In the above equation, the voltage error integrated value Sv = ∫ (Vs−Vo) · dt
It is defined as The calculation of the voltage error integrated value Sv is started from the start of the pulse period Tpb at time t1, and the voltage error integrated value Sv during the peak period Tp after time t2 is 0.
When it becomes [V], the pulse cycle Tpb is ended and the next pulse cycle Tpb is started. As described above, in the output control method of the prior art 1, the pulse cycle T is set so that the one-cycle welding voltage average value Vw for each cycle becomes equal to the voltage setting value Vs.
The arc length is maintained at a proper value by controlling the time length of pb.

[Prior Art 2] FIG. 2 is an external characteristic diagram of a welding power source device showing a relationship between a one-cycle welding current average value Iw on the horizontal axis and a one-cycle welding voltage average value Vw on the vertical axis.
Hereinafter, description will be given with reference to FIG. In the figure, the characteristic L
1 indicates the external characteristic of the slope Ks = 0 [V / A], and the characteristic L
Reference numeral 2 indicates an external characteristic having a slope Ks = -0.1 [V / A].
In the output control method of the above-described conventional technique 1, the one-cycle welding voltage average value Vw is output-controlled to be equal to the predetermined welding voltage set value Vs regardless of the one-cycle welding current average value Iw. Therefore, the above-mentioned external characteristic L1 having the inclination Ks = 0 is formed.

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

In the following description, the external characteristic L2 shown in FIG. 2 will be referred to as a target external characteristic to be formed. Therefore, the straight line expression of the external characteristic L2 is the following expression based on the predetermined welding current setting value Is, welding voltage setting value Vs, and inclination Ks. Vw = Ks · (Iw−Is) + Vs (3) Formula Hereinafter, an output control method for forming the external characteristic L2 shown by the above formula will be described.

FIG. 3 shows the external characteristic L2 expressed by the equation (3).
FIG. 7 is a current / voltage waveform diagram for explaining an output control method of the related art 2 for forming the circuit. The same figure (A) shows the time change of the welding current instantaneous value Io, and the same figure (B) shows the welding voltage instantaneous value V.
The time change of o is shown. Hereinafter, description will be given with reference to FIG.

At the time point t (n) at which the n-th pulse period Tpb (n) starts, the (n-1) -th pulse period Tpb (n-
The previous period welding current average value Iw (n-1) in 1) is calculated, and Iw
= Iw (n-1) is substituted into the above-mentioned formula (3) to set the voltage control set value Vsc (n) which is the target value of the one cycle welding voltage average value Vw.
= Ks. (Iw (n-1) -Is) + Vs is calculated. This calculation is to calculate the voltage control set value Vsc (n) at the point P1 on the external characteristic L2 shown in FIG. Then, by the voltage control set value Vsc (n) and the welding voltage instantaneous value Vo, the voltage error integral value Sv = ∫ (Vsc (n) −Vo) · Equation (2) from time t (n). Calculate dt. Then, the time t (n + 1) at which the voltage error integration value Sv during the peak period of the n-th pulse period Tpb (n) becomes 0 [V].
Then, the n-th pulse cycle Tpb (n) is finished and
The second pulse cycle Tpb (n + 1) is started. Therefore,
One cycle welding voltage average value Vw (n) = Vsc (n) in the nth pulse cycle Tpb (n). After that, the above operation is repeated to control the output. An external characteristic having a predetermined slope Ks can be formed by the output control method of the conventional technique 2 described above.

FIG. 4 is a block diagram of a welding power source device PS for implementing the above-described output control method of the prior art 2. Hereinafter, each circuit block will be described with reference to FIG. The voltage detection circuit VD detects the welding voltage instantaneous value Vo and outputs a voltage detection signal Vd. Current detection circuit ID
Detects the welding current instantaneous value Io and detects the current detection signal Id.
Is output. The one-cycle welding current average value calculation circuit IW calculates the average value of the current detection signal Id for one cycle and outputs the one-cycle welding current average value signal Iw.

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

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

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

FIG. 5 is a timing chart of each signal of the above-mentioned welding power source device PS. The same figure (A) shows the time variation of the welding current instantaneous value Io, the same figure (B) shows the time variation of the welding voltage instantaneous value Vo, and the same figure (C) shows the time variation of the voltage error integral value signal Sv. The comparison signal C is shown in FIG.
m shows the change over time, and FIG. 7E shows the change over time of the switching signal Mm. 1A and 1B are the same as FIG. 1 described above. Hereinafter, description will be given with reference to FIG.

A period from time t (n−1) to t (n) (n−1th)
At the time t (n-1) of the pulse cycle Tpb (n-1) of the second time, the voltage error integrated value signal Sv becomes 0 as shown in FIG.
At [V], as shown in FIG.
m becomes High level for a short time. In response to this change,
As shown in FIG. 7E, the switching signal Mm has a base period T.
During the period b, the level becomes High, and the welding current instantaneous value signal Io becomes the base current Ib as shown in FIG.
During this base period Tb, the voltage error integrated value signal Sv = ∫
(Vsc (n-1) -Vo) ・ dt = ∫ (Vsc (n-1) -Vb) ・
The calculation of dt is performed. Since V (n-1)> Vb, the voltage error integrated value signal Sv as shown in FIG.
Increases with time.

When the switching signal Mm changes to the low level as shown in FIG. 7E, as shown in FIG.
The welding current instantaneous value signal Io becomes the peak current Ip. During this peak period Tp, the voltage error integrated value signal Sv = ∫ (V
sc (n-1) -Vo) ・ dt = ∫ (Vsc (n-1) -Vp) ・ dt
Is calculated. Here, since V (n-1) <Vp, the voltage error integrated value signal Sv decreases with the passage of time and becomes 0 [V] at time t (n), as shown in FIG.

A period after the time t (n) (n-th pulse period Tpb (n) at the start time t (n) of the n-th pulse period Tpb (n) has been described above in the section of FIG. , From time t (n-1)
Substituting the calculated value of the previous period welding current average value Iw (n-1) during T (n) into the equation (3), as shown in FIG. 7B, the nth pulse period Tpb ( The voltage control setting signal Vsc (n) of (n) is calculated. The subsequent operation is the same as the operation described in the above section, and the description thereof will be omitted. As described above, the output control method of the conventional technique 2 can form the external characteristic having the predetermined slope Ks.

[0022]

FIG. 6 is a current / voltage waveform diagram corresponding to FIG. 3 described above for explaining the problem to be solved. The same figure (A) shows the temporal change of the welding current instantaneous value Io, and the same figure (B) shows the temporal change of the welding voltage instantaneous value Vo. This figure shows the (n-1) th pulse period Tpb (n-1)
This is the case where a short circuit occurs between the welding wire and the object to be welded. Generally, in pulse arc welding, short-circuiting occurs several times to several tens of times per second due to droplet transfer. Hereinafter, description will be given with reference to FIG.

When a short circuit occurs during the (n-1) th pulse period Tpb (n-1) as shown in FIG. 9A, normally, the short circuit state is released early to regenerate the arc. A short circuit release current It having a large value is applied to the. Therefore, the previous period welding current average value Iw (n-1) in the (n-1) th pulse period Tpb (n-1) becomes larger than the value of the previous period. As described above in the description of FIG. 3, in order to form the external characteristic having the slope Ks, the previous period welding current average value Iw (n-1) is substituted into the equation (3), and The voltage control set value Vsc (n) is calculated. Therefore, when the previous period welding current average value Iw (n-1) increases, the voltage control set value Vsc (n) of the nth pulse period Tpb (n) decreases. As a result, the one cycle welding voltage average value Vw (n) also becomes smaller, so the arc length in the nth pulse cycle Tpb (n) becomes shorter than in the previous cycle, and a short circuit is more likely to occur. . In other words, the occurrence of one short circuit induces the next short circuit, the arc state becomes unstable, the bead appearance deteriorates, the penetration depth becomes uneven, and welding defects such as large amount of spatter occur. Cheap. Especially during high-speed welding,
In order to prevent the occurrence of welding defects such as undercut,
Usually, it is necessary to set the arc length short and perform welding.
Therefore, a short circuit is likely to occur, and the arc state is likely to be unstable in the output control method of the conventional technique.

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

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

[0026]

The first aspect of the invention is shown in FIGS.
As shown in, the predetermined base current Ib is supplied to a value that does not cause droplet transfer during the predetermined base period Tb, and then the peak current Ip that is predetermined at a value that causes droplet transfer during the peak period Tp. In the output control method of the welding power supply device used for consumable electrode pulse arc welding, in which the current is supplied for 1 cycle and the current is repeatedly supplied as the pulse cycle Tpb, the slope Ks of the external characteristics of the welding power supply device and the welding current setting are set. The value Is and the welding voltage setting value Vs are preset,
The first variable A = Ks · (Ip−I
s) and the second variable B = Ks · (Ip−Ib) · Tb are calculated, the welding voltage instantaneous value Vo during welding is detected, and the nth pulse period Tpb (n) from the start time point is detected. The slope forming voltage error integrated value Sva = ∫ (A + Vs−Vo) · dt is calculated, and the nth base period Tb (n) subsequent to the nth base period Tb (n) is calculated.
At the time when the slope forming voltage error integrated value Sva during the peak period Tp (n) becomes equal to or less than the value of the second variable B, the n-th pulse cycle Tpb (n) is ended, and the pulse cycle Tpb (n) is continued. Nth
This is an output control method for a pulse arc welding power supply device in which the + 1st pulse cycle Tpb (n + 1) is started and the above operation is repeated to form an external characteristic having the above-mentioned inclination Ks and welding is performed.

The second invention is the first invention described in the first invention.
Of the variable A and the second variable B is performed for each predetermined variable calculation cycle Tc during welding or for each start point of the pulse cycle, the output control method of the pulse arc welding power supply device.

As shown in FIGS. 10 to 11, the third invention sets the feed rate setting value Ws of the welding wire and the material and diameter of the welding wire, and calculates the welding current setting value Is from them. Alternatively, it is an output control method of the pulse arc welding power supply device described in the second invention.

Examples 1 to 3 illustrating the embodiment of the present invention will be described below. [Embodiment 1] FIG. 7 is a current / voltage waveform diagram for explaining the operation principle of the output control method of the present invention. Same figure (A)
Shows the temporal change of the welding current instantaneous value Io, and FIG. 7B shows the temporal change of the welding voltage instantaneous value Vo. In the figure,
The target external characteristic formed by the output control method according to the first embodiment is Vw = Ks. (Ws) according to the predetermined welding current setting value Is, the welding voltage setting value Vs, and the slope Ks, as in the above-described formula (3). Iw-Is) + Vs is a straight line. Hereinafter, description will be given with reference to FIG.

As shown in the figure, the 1-cycle welding current average value Iw (n) and the 1-cycle welding voltage average value Vw (n) in the n-th pulse period Tpb (n) are calculated, and both calculated values are calculated. Vw (n) = K
Time point t when the relationship of s · (Iw (n) −Is) + Vs is established
At (n + 1), the n-th pulse cycle Tpb (n) is finished and
The output is controlled to start the + 1st pulse cycle Tpb (n + 1). As a result, the target external characteristic shown by the equation (3) is formed, and in the prior art 2, the previous period welding current average value Iw (n-1) and the current period one period welding voltage average value Vw.
While (n) and (3) were in the relationship of the formula (3), Example 1
Then, the one-cycle welding current average value Iw (n) of the current cycle and the one-cycle welding voltage average value Vw (n) of the current cycle have the relationship of the equation (3). Therefore, the output control in the current cycle is not affected by the disturbance generated in the previous cycle. Hereinafter, the control formula corresponding to the above-mentioned formula (2) which is the basis of the present invention will be derived.

It is assumed that the integration in all the following equations is performed from the start time point to the end time point of the n-th pulse period Tpb (n). (1) 1 cycle welding current average value Iw [A] is peak current Ip [A], base current Ib [A], base period Tb
[S] and the nth peak period Tp (n) [s] are represented by the following equation. Iw = Ip − ((Ip−Ib) · Tb / (Tp (n) + Tb)) (41) Equation (2) In the above equation, when Iw = current set value Is [A], Tp = Tps Becomes Is = Ip-((Ip-Ib) * Tb / (Tps + Tb) (42) Expression (3) The following expression is obtained from the expressions (41) and (42): Iw-Is = (Ip-Ib) * Tb・ ((1 / (Tps + Tb))-(1 / (Tp (n) + Tb))) (43) Expression

(4) The slope Ks [V / A] of the external characteristic is
1st cycle welding voltage average value Vw (n) [V] of the nth time, voltage setting value Vs [V], 1st cycle welding current average value I of the nth time
It is represented by the following equation by w (n) [A] and current set value Is [A]. Ks = (Vw (n) -Vs) / (Iw (n) -Is) (44) Equation (5) Substituting Equation (43) into the above equation yields the following equation. Vw (n) -Vs = Ks. (Ip-Ib) .Tb. ((1 / (Tps + Tb))-(1 / (Tp (n) + Tb))) (45) Formula (6) One cycle welding voltage average The value Vw (n) is defined by the following equation by the welding voltage instantaneous value Vo. Vw (n) = (1 / (Tp (n) + Tb)) ・ ∫Vo ・ dt (46) Formula

(7) Substituting the above equation into the equation (45) gives the following equation. (1 / (Tp (n) + Tb)) ・ ∫ (Vo-Vs) ・ dt = Ks ・ (Ip-Ib) ・ Tb ・ ((1 / (Tps + Tb))-(1 / (Tp (n) + Tb ))) (47) Equation (8) The above equation is transformed into the following equation. ∫ (Vo-Vs) * dt = Ks * (Ip-Ib) * Tb * ((Tp (n) + Tb) / (Tps + Tb))-Ks * (Ip-Ib) * Tb (48) Formula (9) When the equation (42) is modified, it becomes the following equation. (Ip−Ib) · Tb / (Tps + Tb) = Ip−Is (49) Formula (10) Substituting the above formula into the formula (48) gives the following formula. ∫ (Vo-Vs) * dt = Ks * (Ip-Is) * (Tp (n) + Tb) -Ks * (Ip-Ib) * Tb (410) Equation (11) Become. ∫Ks · (Ip−Is) · dt−∫ (Vo−Vs) · dt = Ks · (Ip−Ib) · Tb (411) Formula

(12) Here, in order to simplify the equation, the first variable A is introduced and defined by the following equation. A = Ks · (Ip−Is) (5) Formula (13) Similarly, the second variable B is introduced and defined by the following formula. B = Ks · (Ip−Ib) · Tb (6) Equation (14) By substituting Equation (5) and Equation (6) into Equation (411), the following equation, which is a control equation of the present invention, is obtained. ∫ (A + Vs−Vo) · dt = B (7) Formula

Therefore, the nth pulse period Tpb
At the end of (n), the above equation will hold.
At the start of the n-th pulse cycle Tpb (n),
Since the set value parameters of the slope Ks, the peak current Ip, the current set value Is, the base current Ib, and the base period Tb can be regarded as constants, the first variable A shown in the above equation (5) and the above equation (6) are given. The second variable B indicated by can be both regarded as a constant. Here, the n-th pulse period T
The slope forming voltage error integrated value Sva from the start point of pb (n) is defined as Sva = ∫ (A + Vs−Vo) · dt, which is the left side of the above equation (7). Usually, Ks ≦ 0, Ib <Is <Ip, Tb
Since> 0, A = Ks · (Ip−Is) ≦ 0 and B = K
s · (Ip−Ib) · Tb ≦ 0. In FIG.
Vs> Vo (= Vb) during the base period Tb,
The value of (A + Vs−Vo) can be a positive value or a negative value depending on the value of the set value parameter. On the other hand, since Vs <Vo (= Vp) during the peak period Tp, (A + Vs−V
o) <0, and the value of the slope forming voltage error integrated value Sva decreases gradually with the passage of time during the peak period Tp. Therefore, the slope forming voltage error integrated value Sva from the start time of the n-th pulse period Tpb (n) is calculated, and the calculated value becomes equal to the value of the second variable B or the second variable B When it becomes less than or equal to the value, the n-th pulse cycle Tpb (n) is ended. That is, the pulse period ends when the following equation is established. Sva = ∫ (A + Vs−Vo) · dt ≦ B Equation (8) However, the integration is performed during the n-th pulse period Tpb (n).

As described above, according to the present invention, the first variable A
= Ks · (Ip−Is) and the second variable B = Ks · (I
p−Ib) · Tb is calculated, then the welding voltage instantaneous value Vo during welding is detected, and the slope forming voltage error integrated value Sva = ∫ (A + V) from the start of the n-th pulse cycle Tpb (n).
s-Vo) .dt is calculated, and the value of the slope forming voltage error integrated value Sva during the nth peak period Tp following the nth base period Tb becomes equal to or less than the value of the second variable B. At this point, the n-th pulse cycle Tpb (n) is ended, the n + 1-th pulse cycle Tpb (n + 1) is subsequently started, and the above-mentioned operation is repeated to thereby obtain the above-mentioned inclination Ks. It is an output control method of a pulse arc welding power supply device for forming an external characteristic and performing welding.

When the slope Ks = 0 is set, the first variable A = 0 and the second variable B = 0, so that the equation (8) becomes Sva = ∫ (Vs−Vo) · dt ≦ 0. , Which coincides with the equation (2) in the case of the above-mentioned conventional technique. That is, the special case (Ks = 0) in the expression (8) showing the output control method of the present invention is the case of the expression (2) showing the output control method of the prior art.

FIG. 8 is a block diagram of the pulse-period-controlled welding power supply PSA of the first embodiment for carrying out the present invention described above. 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 first variable operation circuit CA has a slope setting signal Ks, a peak current setting signal Ip and a welding current setting signal I.
Using s as an input, the operation of the equation (5) described above is performed, and
The variable calculation value signal Ca of is output. The second variable calculation circuit CB has a slope setting signal Ks, a peak current setting signal Ip,
Using the base current setting signal Ib and the base period setting signal Tb as inputs, the calculation of the above-described equation (6) is performed, and the second variable calculation value signal Cb is output.

The slope forming voltage error integrating circuit SVA receives the first variable calculation value signal Ca, the welding voltage setting signal Vs and the voltage detection signal Vd as input, and starts the n-th pulse period Tpb (n). Then, the left side of the above equation (8) is integrated to output the slope forming voltage error integrated value signal Sva.
The variable comparison circuit CMA compares the slope forming voltage error integrated value signal Sva with the second variable operation value signal Cb, and when it becomes SVa ≦ Cb, a comparison signal which becomes High level for a short time. Output Cm. That is, the above-mentioned slope forming voltage error integration circuit SVA and the variable comparison circuit CMA perform the calculation of the above-mentioned equation (8) showing the output control method of the present invention. The description of the operation thereafter is the same as that of FIG.

FIG. 9 is a diagram showing the relationship between the time change of the slope forming voltage error integrated value Sva shown on the left side of the above equation (8) and the pulse period Tpb. The figure (A) shows the welding current instantaneous value I.
In the same figure (B), the vertical axis represents the change in o, and the vertical axis represents the slope forming voltage error integrated value Sva from the start point (t0) of the pulse period.
Of the pulse period Tpb is shown on the horizontal axis. The three characteristics Y1 to Y3 shown in the figure have the same set value parameters described in the section of the description of FIG. 7, and therefore the first variable A, the second variable B and the welding voltage in the equation (8) are used. When the set values Vs are the same, the arc length during welding is a proper value (characteristic Y2), is shorter than the proper value (characteristic Y1), and is longer than the proper value (characteristic Y3). Hereinafter, description will be given with reference to FIG.

When the arc length is a proper value (characteristic Y2) The base voltage when the arc length is a proper value is Vb2 and the peak voltage is Vp2. Times t0 to t1 shown in FIG.
Up to the base period Tb, the slope forming voltage error integration value S
va is a calculated value of Sva = ∫ (A + Vs−Vb2) dt and gradually decreases with the passage of time. Then, during the peak period Tp after the time t1, the slope forming voltage error integrated value Sva.
Becomes gradually smaller as the calculated value of Sva = ∫ (A + Vs−Vp2) dt with the lapse of time, with a slope different from that during the base period Tb, and when Sva ≦ B at time t3, the pulse period Tpb2 ends.

When the arc length is shorter than the proper value (characteristic Y1) Since the welding voltage instantaneous value Vo is substantially proportional to the arc length, the base voltage when the arc length is shorter than the proper value is Vb1 <Vb2.
And the peak voltage becomes Vp1 <Vp2. During the base period Tb from time t0 to t1 shown in FIG. 7A, the slope forming voltage error integrated value Sva is Sva = ∫ (A + Vs−Vb1).
As the calculated value of dt, it becomes smaller with a gradual gradient as compared with the case of the above term with the passage of time. Then, during the peak period Tp after the time t1, the slope forming voltage error integrated value Sva is S
As the calculated value of va = ∫ (A + Vs−Vp1) · dt decreases with the passage of time with a gradient different from that during the base period Tb, and when Sva ≦ B at time t4, the pulse period Tpb
1 ends. Therefore, when the arc length is shorter than the proper value, the pulse period Tpb1 is Tpb2 in the above term.
And the one-cycle welding voltage average value Vw increases, the arc length changes in the increasing direction and approaches an appropriate value.

When the arc length is longer than the proper value (characteristic Y3) As described above, the welding voltage instantaneous value Vo is substantially proportional to the arc length. Therefore, when the arc length is longer than the proper value, the base voltage is Vb3>. It becomes Vb2 and the peak voltage becomes Vp3> Vp2. In the base period Tb from time t0 to t1 shown in FIG. 9A, the slope forming voltage error integrated value Sva is Sva = ∫ (A
+ Vs-Vb3) ・ dt as the calculated value,
It becomes smaller with a steeper slope than in the above case. And
During the peak period Tp after the time t1, the slope forming voltage error integrated value Sva becomes a calculated value of Sva = ∫ (A + Vs−Vp3) · dt and becomes smaller with a gradient different from that during the base period Tb over time, and at the time t2. When Sva ≦ B, the pulse cycle Tpb3 ends. Therefore, when the arc length is longer than the proper value, the pulse period Tpb3 becomes shorter than Tpb2 in the above term, and the one-cycle welding voltage average value Vw becomes smaller, so the arc length changes in the direction of shortening. Will approach the proper value. As described above, the pulse period changes as the slope of the slope forming voltage error integrated value Sva changes according to the variation of the arc length during welding, and as a result, the one-cycle welding voltage average value Vw changes. Suppress fluctuations in arc length.

[Embodiment 2] The invention of Embodiment 2 is the first variable A and the second variable B in the invention of Embodiment 1 described above.
Is calculated by a predetermined variable calculation cycle Tc [s] during welding.
This is a method of controlling the output of the pulse arc welding power supply device, which is performed for each time or each time when the pulse period Tpb is started. Hereinafter, Example 2
The invention will be described.

The welding power source apparatus for carrying out the output control method of the second embodiment has a configuration in which the operations of the first variable arithmetic circuit CA and the second variable arithmetic circuit CB in FIG. 8 described above are changed as follows. Becomes The first variable calculation circuit CA according to the second embodiment has a slope setting signal Ks and a peak current setting signal Ip.
And the welding current setting signal Is as an input, the variable comparison signal Cm is output for a short time Hi at every predetermined variable calculation cycle Tc.
At each start time point of the pulse period Tpb which becomes the gh level, the calculation of the above-mentioned formula (5) is performed, and the first variable calculation value signal Ca
Is output. The second variable calculation circuit CB of the second embodiment receives the slope setting signal Ks, the peak current setting signal Ip, the base current setting signal Ib, and the base period setting signal Tb as input, or every predetermined variable calculation cycle Tc or variable. Every time the pulse period Tpb at which the comparison signal Cm becomes High level for a short period of time is started, the calculation of the equation (6) is performed, and the second variable calculation value signal Cb is output.

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

[Third Embodiment] The invention of the third embodiment sets the feed rate setting value Ws of the welding wire and the material and diameter of the welding wire, and sets the welding current in the invention of the first or second embodiment. It is the output control method of the pulse arc welding power supply device which calculates the value Is. Hereinafter, the invention of Example 3 will be described.

The welding power source device for carrying out the invention of the third embodiment has a structure in which the welding current setting circuit IS in FIG. 8 described above is replaced with a welding current set value calculation circuit CIS described later in FIG. 110. FIG. 10 is a block diagram of the welding current set value calculation circuit CIS. The feeding speed setting circuit WS installed outside the welding power source device outputs a predetermined feeding speed setting signal Ws. The welding current set value calculation circuit CIS built in the welding power source device inputs the above-mentioned feed rate setting signal Ws, the material of the welding wire and the diameter of the welding wire, and calculates the welding current calculated by the melting characteristics illustrated in FIG. The setting signal Is is output.

FIG. 11 shows the feed rate set value Ws shown on the vertical axis.
FIG. 6 is a melting characteristic diagram showing the relationship between the welding current setting value Is shown on the horizontal axis and the welding current setting value Is. In the figure, the material of the welding wire is aluminum alloy A5356, and the diameter of the welding wire is 1.
The melting characteristics in the case of 2 [mm] or 1.6 [mm] are shown. For example, the welding current setting value Is when the feeding speed setting value Ws = 900 [cm / min] is Is when the diameter is 1.2 [mm].
= 150 [A], and when the diameter is 1.6 [mm], Is
= 250 [A]. Even when the material of the welding wire is steel, stainless steel, etc., the welding current setting value Is is calculated from the melting characteristic diagram corresponding to the figure.

In the above-described third embodiment of the invention, the output control method of the present invention is applied even when the feed speed setting signal Ws, which is often used in place of the welding current setting signal Is, is input from the outside. It can be carried out.

[0052]

According to the present invention, since the operating points of the one-cycle welding current average value Iw and the one-cycle welding voltage average value Vw in each pulse period Tpb always exist on the target external characteristic, each pulse period Tpb. Fluctuations in arc length due to internal disturbances are suppressed during that period. Therefore, since the transient response to the disturbance is excellent, the variation of the arc length during welding is reduced, and good welding quality can always be obtained. further,
In the invention of the second embodiment, even if the set value parameter changes during welding, by appropriately recalculating the first variable A and the second variable B, it is possible to always perform appropriate output control. . Furthermore, in the invention of the third embodiment, the output control method of the present invention can be implemented even when the feed speed setting signal Ws is input from the outside in place of the welding current setting signal Is.

[Brief description of drawings]

[Figure 1] Current / voltage waveform diagram of pulse arc welding

[Fig. 2] External characteristic diagram of welding power source device

FIG. 3 is a current / voltage waveform diagram for explaining an output control method according to Related Art 2.

FIG. 4 is a block diagram of a welding power source device of prior art 2.

FIG. 5 is a timing chart of a welding power supply device according to the related art 2.

FIG. 6 is a current / voltage waveform diagram for explaining a problem to be solved.

FIG. 7 is a current / voltage waveform diagram for explaining the output control method of the first embodiment.

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

FIG. 9 is a diagram showing the relationship between the time change of the slope forming voltage error integrated value Sva and the pulse period Tpb of the first embodiment.

FIG. 10 is a welding current set value calculation circuit C according to the third embodiment.
Block diagram of IS

FIG. 11 is a melting characteristic diagram showing the relationship between the feed rate set value Ws and the welding current set value Is.

[Explanation of symbols]

1 welding wire 2 Objects to be welded 3 arc 4 welding torch 5a Feeding roll of wire feeding device A first variable B second variable CA first variable calculation circuit Ca First variable calculation value signal CB Second variable operation circuit Cb second variable operation value signal CIS welding current set value calculation circuit CM comparison circuit Cm comparison signal CMA variable comparison circuit EI current error amplifier circuit Ei Current error amplification signal IB base period setting circuit Ib base current (setting signal) ID current detection circuit Id current detection signal INV output control circuit Io Welding current instantaneous value IP peak period setting circuit Ip peak current (setting signal) IS welding current setting circuit Is welding current setting (value / signal) Isc current control setting signal It Short circuit release current IW 1 cycle welding current average value calculation circuit Iw, Iw (n) 1 cycle welding current average value (signal) KS slope setting circuit Ks External characteristic slope (setting signal) L1, L2 external characteristics MM timer circuit Mm switching signal P1 operating point PS welding power supply PSA Pulse cycle control welding power supply device SV voltage error integration circuit Sv Voltage error integrated value (signal) SVA slope forming voltage error integrating circuit Sva slope forming voltage error integrated value (signal) SW base / peak switching circuit Tb base period (setting signal) Tp peak period Tpb, Tpb (n) pulse period Vb base voltage VD voltage detection circuit Vd voltage detection signal Vo Welding voltage instantaneous value Vp peak voltage VS welding voltage setting circuit Vs welding voltage setting (value / signal) VSC external characteristic control circuit Vsc voltage control setting (value / signal) Vw, Vw (n) 1 cycle welding voltage average value WS feed speed setting circuit Ws feeding speed setting (value / signal) Y1 to Y3 melting characteristics

Claims (3)

[Claims] 1. A predetermined base current Ib is applied to a value that does not cause droplet transfer during a predetermined base period Tb, and a predetermined peak current Ip is continuously applied to a value that causes droplet transfer during a peak period. In an output control method of a welding power supply device used for consumable electrode pulse arc welding in which energization is performed and welding is performed by repeatedly energizing these one cycle as a pulse cycle, a slope Ks of an external characteristic of the welding power supply device and a welding current set value Is And a welding voltage set value Vs are preset, and the first variable A = Ks · (Ip−Is) and the second variable are set according to the set value.
After calculating the variable B = Ks · (Ip−Ib) · Tb, the welding voltage instantaneous value Vo during welding is detected and the slope forming voltage error integrated value S from the start point of the n-th pulse cycle is detected.
va = ∫ (A + Vs−Vo) · dt is calculated so that the slope forming voltage error integrated value Sva during the nth peak period following the nth base period becomes equal to or less than the value of the second variable B. At this point, the n-th pulse cycle is ended, the (n + 1) -th pulse cycle is subsequently started, and the above-described operation is repeated to form an external characteristic having the inclination Ks and perform welding. Output control method for welding power supply device. 2. A pulse arc welding power source for performing the calculation of the first variable A and the second variable B according to claim 1 at each predetermined variable calculation cycle during welding or at each start point of the pulse cycle. Output control method of device. 3. The pulse arc welding power supply device according to claim 1, wherein the welding wire feed rate setting value and the material and diameter of the welding wire are set, and the welding current setting value Is is calculated from them. Output control method.