JP2007196238A - Control method for output of consumable electrode pulse arc welding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control fluctuation in arc length in a consumable electrode pulse arc welding for performing welding by energizing the welding current in which the conduction of the peak current during the peak period and the conduction of the base current during the base period form one pulse period. <P>SOLUTION: In a control method for the output of the consumable electrode pulse arc welding, a mean welding current value Iav is continuously calculated from the starting point of the n-th pulse period, a peak voltage value Vp is detected, and the mean welding current set value is calculated by a predetermined external characteristic L3 with the peak voltage value Vp as the input. When the mean welding current value Iav is equal to the mean welding current set value during the base period continuous with the peak period, the n-th pulse period is completed, and the (n+1)-th pulse period is started. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an output control method for consumable electrode pulse arc welding for improving the stability of arc length control.

  In consumable electrode pulse arc welding, it is extremely important to maintain the arc length during welding (apparent arc length) at an appropriate value in order to obtain good weld quality such as a beautiful bead appearance and uniform penetration depth. It is. Generally, the arc length is determined by the balance between the welding wire feed rate and the melting rate due to arc heat or the like. Therefore, when the melting rate substantially proportional to the average value Iav of the welding current becomes equal to the feeding rate, the arc length is always constant and stabilized. However, the feeding speed during welding varies due to fluctuations in the rotational speed of the feeding motor, fluctuations in the frictional force of the feeding path due to the routing of the welding torch cable, and the like. For this reason, the balance with the melting rate is lost, and the arc length changes. Furthermore, the arc length also fluctuates due to fluctuations in the distance between the power supply tip and the base material (torch height) due to the shaking of the welding operator, irregular vibrations in the molten pool, and the like. Therefore, in order to suppress the variation of the arc length due to these various fluctuation factors (hereinafter referred to as disturbance), it is essential to control the arc length to always adjust the melting rate according to the disturbance and suppress the change in the arc length. Become.

In consumable electrode gas shielded arc welding including consumable electrode pulse arc welding, as a method for suppressing fluctuations in arc length caused by the various disturbances described above, output control for forming external characteristics of the welding power source to a desired value is performed. It is commonly used. FIG. 6 shows an example of external characteristics. In the figure, the horizontal axis represents the average value Iav of the welding current passing through the welding wire, and the vertical axis represents the average value Vav of the welding voltage applied between the welding wire and the base material. Generally, since the welding voltage value is proportional to the arc length, the average welding voltage value Vav is proportional to the average arc length. Moreover, the average welding current value Iav is proportional to the melting rate as described above. Therefore, this figure shows the relationship between the melting rate and the average arc length. When the arc length fluctuates, the fluctuation of the arc length is suppressed by changing the melting rate based on this external characteristic. The external characteristic L1 shown in the figure is a case of a complete constant voltage characteristic with a slope Ks = 0 V / A. The external characteristic L2 is a case of a constant voltage characteristic having a slope Ks = −0.1 V / A and a downward slope. Since the external characteristic can be expressed as a straight line, the external characteristic having an inclination Ks passing through the intersection P0 between the welding current reference value Is and the welding voltage reference value Vs can be expressed by the following equation.
Vav = Ks · (Iav−Is) + Vs (1)

  By the way, it is widely known that the stability of arc length control (referred to as self-control action) is greatly influenced by the slope Ks of the external characteristic of the welding power source. That is, in order to stabilize the arc length against disturbance, it is necessary to control the slope Ks of the external characteristic to an appropriate value according to the welding conditions including the welding method. For example, the appropriate value of the slope Ks is in the range of about 0 to -0.03 V / A in the carbon dioxide arc welding method, and in the range of about -0.05 to -0.3 V / A in the pulse arc welding method. Therefore, in the pulse arc welding method which is the subject of the present invention, in order to stabilize the arc length control, it is not in the external characteristic L1 shown in the figure but in the range of about -0.05 to -0.3 V / A. Therefore, it is necessary to form the external characteristic L2 and the like having a predetermined slope Ks. Hereinafter, a conventional technique for forming an external characteristic having a desired inclination Ks in pulse arc welding will be described.

  FIG. 7 is a current / voltage waveform diagram of pulse arc welding. 4A is a waveform diagram of the welding current (instantaneous value) io, and FIG. 2B is a waveform diagram of the welding voltage (instantaneous value) vo. Hereinafter, description will be given with reference to FIG.

(1) Peak period Tp between times t1 and t2
During the predetermined peak period Tp, a predetermined peak current Ip having a large current value is applied to transfer the welding wire to the droplet as shown in FIG. In addition, a peak voltage Vp substantially proportional to the arc length during this period is applied.

(2) Base period Tb between times t2 and t3
During the base period Tb determined by the output control of the welding power source described later, as shown in FIG. 5A, a predetermined base current Ib having a small current value is applied so as not to grow the droplets at the tip of the welding wire, As shown in FIG. 5B, a base voltage Vb that is substantially proportional to the arc length during this period is applied.

Welding is performed by repeating the period from time t1 to t3 consisting of the peak period Tp and the base period Tb as one pulse Tpb. As shown in FIG. 6A, the average value of the welding current for each pulse period Tpb is Iav. Similarly, as shown in FIG. 5B, the average value of the welding voltage for each pulse period Tpb is Vav. Output control for forming external characteristics of the welding power source is performed by feedback control using the time length of the pulse period Tpb as an operation amount. That is, output control is performed by increasing or decreasing the pulse period Tpb (base period Tb) with the peak period Tp as a constant value.

  As shown in FIG. 8, the average value of the welding current in the n-th pulse period Tpb (n) from time t (n) to t (n + 1) is Iav (n), and the average value of the welding voltage is Vav. (n). In FIG. 6 described above, output control is performed so that the intersection P1 between these Iav (n) and Vav (n) is on a preset external characteristic L2. Hereinafter, the output control method of the welding power source for forming the external characteristic having the desired inclination Ks will be described.

A conventional external characteristic forming method will be described with reference to the pulse arc welding waveform diagram described above with reference to FIG. The target external characteristic to be formed is the external characteristic of the above-described equation (1). The average welding current value Iav and average welding voltage value Vav in the n-th pulse period Tpb (n) can be expressed by the following equations.
Iav = (1 / Tpb (n)) · ∫ia · dt (2) Equation Vav = (1 / Tpb (n)) · ∫va · dt (3) However, the integration is the nth time It is performed during the pulse period Tpb (n), ia is the absolute value of the welding current io, and va is the absolute value of the welding voltage vo.

Substituting these formulas (2) and (3) into the above-described formula (1) and rearranging them gives the following formula.
∫ (Ks · ia−Ks · Is + Vs−va) · dt = 0 (4) where the integration is performed during the nth pulse period Tpb (n), and Ks is the slope of the external characteristic, Is Is a welding current reference value, and Vs is a welding voltage reference value.

Therefore, when the nth pulse cycle Tpb (n) ends, the above equation (4) is established. Here, when the left side of the above equation (4) is defined as the integral value SVi, the following equation is obtained.
Svj = ∫ (Ks · ia−Ks · Is + Vs−va) · dt (5)

  The calculation of the integral value Svi of the above equation (5) is started from the time when the nth pulse cycle Tpb (n) starts. When the n-th predetermined peak period Tp ends and the integrated value Svi = 0 (or Svi ≧ 0) is reached during the n-th base period Tb, the n-th pulse period Tpb (n ) Ends. By repeating this operation, it is possible to form the external characteristic of the above-described equation (1).

The external characteristic forming method described above will be summarized and described below.
(1) The external characteristics of the target welding power source are set in advance by the inclination Ks, the welding current reference value Is, and the welding voltage reference value Vs.
(2) The absolute value va of the welding voltage vo and the absolute value ia of the welding current io are detected during welding.
(3) The calculation of the integral value Svi = ∫ (Ks · ia−Ks · Is + Vs−va) · dt is started from the start time of the nth pulse cycle Tpb (n).
(4) When the integral value Svi in the nth base period Tb following the nth predetermined peak period Tp becomes 0 or more (Svi ≧ 0), the nth pulse period Tpb (n ) Ends.
(5) Subsequently, by starting the (n + 1) th pulse cycle Tpb (n + 1) and repeating the operations (3) to (4), the desired external characteristic set in the above (1) can be obtained. Form.

  FIG. 9 is a block diagram of a welding power source equipped with output control for forming the above-described external characteristics. Hereinafter, each block will be described with reference to FIG.

  The power supply main circuit PM receives an AC commercial power supply (3-phase 200V, etc.) as input, performs power control such as inverter control in accordance with a current error amplification signal Ei described later, and outputs a welding current io and a welding voltage vo suitable for welding. . The welding wire 1 is fed through the welding torch 4 by the rotation of the feeding roll 5 of the wire feeding device, and an arc 3 is generated between the welding wire 1 and the base material 2. The voltage detection circuit VD detects the welding voltage vo and converts it into an absolute value, and outputs a welding voltage absolute value signal va. The current detection circuit ID detects the welding current io and converts it into an absolute value, and outputs a welding current absolute value signal ia.

  The welding current reference value setting circuit IS outputs a predetermined welding current reference value signal Is. The welding voltage reference value setting circuit VS outputs a predetermined welding voltage reference value signal Vs. The inclination setting circuit KS outputs an inclination setting signal Ks having a predetermined external characteristic. Desired external characteristics are set by these three signals Is, Vs, and Ks. The integration circuit SVI receives the welding voltage absolute value signal va, the welding current absolute value signal ia, the welding voltage reference value signal Vs, the welding current reference value signal Is, and the slope setting signal Ks, and integrates the above equation (5). The value Svi = ∫ (Ks · ia−Ks · Is + Vs−va) · dt is calculated, and the integrated value signal Svi is output. When the comparison circuit CM determines that the value of the integration value signal Svi is 0 or more (Svi ≧ 0), the comparison circuit CM outputs a comparison signal Cm that becomes a high level for a short time.

  The welding current waveform parameter setting circuit PF outputs a welding current waveform parameter setting signal Pf including a peak current setting value Ips, a base current setting value Ibs, and a peak period setting value Tps forming a welding current waveform. The current setting circuit ICS receives the comparison signal Cm and the welding current waveform parameter setting signal Pf and starts the n-th pulse period Tpb (n). During the period determined by the peak period setting value Tps, the current setting circuit ICS The peak current set value Ips is output as the welding current setting signal Ics, and then the base current set value Ibs is output as the welding current setting signal Ics during the period until the comparison signal Cm becomes the high level. The current error amplification circuit EI amplifies an error between the welding current setting signal Ics and the welding current absolute value signal ia, and outputs a current error amplification signal Ei. Thereby, the welding current setting signal Ics and the welding current io have the same waveform.

  FIG. 10 is a timing chart of each signal of the above-described welding power source. 4A shows the welding current io, FIG. 2B shows the welding voltage vo, and FIG. 3C shows the change over time of the integrated value signal Svi. Hereinafter, description will be given with reference to FIG.

  When the n-th pulse period Tpb (n) starts at time t (n), the peak current Ip is energized as shown in FIG. 9A, and the peak voltage is applied as shown in FIG. Vp is applied. In response to this, the value of the integral value signal Svi decreases in the negative direction as shown in FIG. When the base period Tb starts at time t2, the base current Ib is energized as shown in FIG. 9A, and the base voltage Vb is applied as shown in FIG. The value of the integral value signal Svi shown in FIG. 5C increases and becomes 0 at time t3, and the nth pulse cycle Tpb (n) ends. Thereafter, the above-described operation is repeated (see, for example, Patent Documents 1 and 2).

JP 2003-230958 A Japanese Patent Laid-Open No. 2005-118872

  As described above, in order to improve the stability of the arc length control, it is necessary to form the external characteristic having the desired slope Ks described above with reference to FIG. In FIG. 6, the average welding voltage value Vav on the vertical axis is an average value for each pulse period Tpb, and the welding voltage value and the arc length are in a proportional relationship. As a result, the vertical axis represents the average arc length for each pulse period. Is equivalent to indicating Therefore, the stability of the arc length control is realized by controlling the relationship between the melting rate determined by the average welding current Iav and the arc length to an external characteristic having a desired slope.

  FIG. 11 is a schematic diagram of the arc generation unit. FIG. 11A shows the arc generation unit during the peak period Tp, and FIG. 11B shows the arc generation unit during the base period Tb. As shown in FIG. 4A, during the peak period Tp, the peak current Ip having a large current value is energized, so that the directivity of the arc 3 becomes strong, and the arc 3 is between the base metal 2 immediately below the welding wire 1. Occurs. The shortest distance from the tip of the welding wire to the base metal 2 is called the apparent arc length La1 and has a great influence on the welding quality. Therefore, the simple term “arc length” usually refers to the apparent arc length La1. The arc length control described above is to control the apparent arc length La1 that has a significant effect on the welding quality to an appropriate value. In FIG. 5A, the true arc length Lt1 is the actual distance of the arc 3, and when the arc 3 is generated immediately below, Lt1≈La1. This true arc length Lt1 is proportional to the welding voltage value (peak voltage value Vp). Therefore, in this case, the apparent arc length that is originally desired to be detected can be detected by the welding voltage value (peak voltage value Vp). Similarly, when the arc 3 is generated immediately below in the base period Tb, the apparent arc length can be detected by the welding voltage value (base voltage value Vb). The prior art output control is constructed on the precondition that the above-described state, that is, the apparent arc length can be accurately detected by the welding voltage value.

  However, as shown in FIG. 5B, since the base current Ib having a small current value is energized during the base period Tb, the directivity of the arc 3 is weak. For this reason, the arc 3 may be generated in an oblique direction without being generated directly under the surface state of the base material 2, the shielding state of the shielding gas, and irregular vibration of the molten pool. The generation of the arc 3 in the oblique direction often occurs in MIG welding in which the arc cathode spot moves in search of an oxide film on the surface of the base material. In this state, the apparent arc length La2 and the true arc length Lt2 become considerably different values as shown in FIG. At this time, the welding voltage value (base voltage value Vb) is a value proportional to the true arc length Lt2, and is not proportional to the apparent arc length La2. For this reason, the average welding voltage value Vav for each pulse period is an average value of the peak voltage value Vp proportional to the apparent arc length and the base voltage value not proportional to the apparent arc length. With the welding voltage value Vav, the apparent arc length for each pulse period cannot be detected accurately. As a result, arc length controllability is reduced.

  Therefore, the present invention provides an output control method for consumable electrode pulse arc welding that can improve the arc length controllability even under welding conditions in which an arc is frequently generated in an oblique direction.

In order to solve the above-described problem, the first invention is a consumable electrode pulse arc that is welded by applying a welding current with a peak current applied during a peak period and a base current applied during a base period as one pulse period. In the welding output control method,
The average welding current value is calculated every moment from the start of the nth pulse cycle, the peak voltage value during the peak period is detected, and the average welding current set value is determined according to a predetermined external characteristic using the peak voltage value as an input. To calculate
When the average welding current value becomes equal to the average welding current set value during the base period following the peak period, the nth pulse cycle is ended, and then the (n + 1) th pulse cycle is started. This is an output control method for consumable electrode pulse arc welding.

  According to a second aspect of the present invention, there is provided an output control method for consumable electrode pulse arc welding according to the first aspect, wherein the peak current has a slope at the rise and / or fall.

  According to a third aspect of the present invention, an electrode minus period is provided before the peak period, and the electrode minus polarity is switched during the electrode minus period to pass an electrode minus current. It is an output control method of consumable electrode pulse arc welding according to the invention.

  4th invention calculates the said average welding current value by the setting signal of the said welding current, The output of the consumable electrode pulse arc welding of any one of the 1st-3rd invention characterized by the above-mentioned It is a control method.

  According to the first aspect of the present invention, the apparent arc length change is accurately detected by the peak voltage value under the welding conditions in which the arc is frequently generated in the oblique direction, and the peak voltage value Vp is set in advance as the input. An average welding current set value is calculated based on the external characteristics, and output control is performed so that the average welding current value for each pulse period becomes the average welding current set value. As a result, the arc length controllability is improved and good welding quality can be obtained even under welding conditions (for example, during MIG welding) where the arc is generated in an oblique direction.

  Furthermore, according to the second invention, even when the rising and / or falling of the peak current has an inclination, the same effect as that of the first invention can be obtained.

  Furthermore, according to the third aspect of the invention, the same effect as that of the first aspect of the invention described above can be achieved in AC pulse arc welding with an electrode minus period.

  Furthermore, according to the third invention, the average welding current value can be calculated from the setting signal of the welding current, and the same effect as the first invention described above can be obtained.

  Embodiments of the present invention will be described below with reference to the drawings.

[Embodiment 1]
FIG. 1 is a diagram showing external characteristics of the welding power source according to Embodiment 1 of the present invention. In the figure, the horizontal axis represents the average welding current Iav, and the vertical axis represents the peak voltage value Vp. Unlike FIG. 6 which shows a prior art, the reason why the vertical axis is changed to the peak voltage value Vp is as follows. As described above with reference to FIG. 11, the peak current Ip having a large current value is applied during the peak period Tp, so that the directivity of the arc becomes strong, and the arc is generated immediately below the welding wire. As a result, since the apparent arc length and the true arc length are substantially equal, the apparent arc length can be detected from the peak voltage value Vp proportional to the true arc length. Therefore, the change in the apparent arc length for each pulse period is detected by the change in the apparent arc length during the peak period Tp. Since a change in the apparent arc length in a pulse period of several cycles to several tens of cycles becomes a problem in the welding quality, it is not necessary to detect the average apparent arc length in one pulse cycle. It is important to detect the apparent arc length of the peak period Tp for each pulse period and to accurately detect the change width of the apparent arc length over several cycles to several tens of cycles.

In the figure, setting the vertical axis to the peak voltage value Vp is equivalent to setting the external characteristic with the apparent arc length as the vertical axis. Therefore, good arc length control can be performed by controlling the output of the welding power source so that the external characteristics shown in FIG. The external characteristic L3 shown in the figure is a straight line passing through the point P0 and having an inclination Ks, and can be expressed by the following equation. Point P0 is an intersection of welding current reference value Is and peak voltage reference value Vps.
Vp = Ks · (Iav−Is) + Vps (6)

  FIG. 2 is a block diagram of a welding power source equipped with output control for forming the above-described external characteristic L3. In the figure, the same blocks as those in FIG. 9 described above are denoted by the same reference numerals, and description thereof is omitted. Hereinafter, blocks indicated by dotted lines different from those in FIG. 9 will be described.

The peak voltage detection circuit VPD detects the peak voltage Vp and outputs a peak voltage detection signal Vpd. The average current calculation circuit IAV calculates an average value every moment from the start time of each pulse period, and outputs an average welding current value signal Iav. The method for calculating the average value will be described in detail with reference to FIG. The peak voltage reference value setting circuit VPS outputs a predetermined peak voltage reference value signal Vps. The average welding current setting circuit IAVS receives the welding current reference value signal Is, the inclination setting signal Ks, the above peak voltage reference value signal Vps, and the above peak voltage detection signal Vpd as inputs. = ((Vpd-Vps) / Ks) + Is (7)
And an average welding current setting signal Iavs is output. Thereby, the average welding current value Iav (average welding current setting signal Iavs) on the external characteristic of FIG. 1 corresponding to the peak voltage detection signal Vpd is calculated. The second comparison circuit CM2 is a short time for ending the current pulse period when the average welding current value signal Iav and the average welding current setting signal Iavs are equal to each other in the base period following the peak period. The comparison signal Cm which becomes High level is output.

  FIG. 3 is a timing chart of each signal of the welding power source described above. FIG. 4A shows the welding current io, FIG. 4B shows the welding voltage vo, and FIG. 4C shows the time variation of the average welding current value signal Iav and the average welding current setting signal Iavs. Hereinafter, a description will be given with reference to FIG.

  When the n-th pulse period Tpb (n) starts at time t1, the peak current Ip is energized as shown in FIG. 5A, and the peak voltage Vp is applied as shown in FIG. To do. With this peak voltage value Vp as an input, the value of the average welding current setting signal Iavs shown in FIG. Therefore, the value of the average welding current setting signal Iavs is newly calculated corresponding to the peak voltage value Vp for each pulse period Tpb.

If the elapsed time from the time t1, which is the starting point of the nth pulse period Tpb (n), is t, the average welding current value Iav at the elapsed time t can be expressed by the following equation.
Iav = (1 / t) · ∫ia · dt (8) where ia is a welding current absolute value signal and integration is performed during the elapsed time t.
As shown in FIG. 5C, the value of the average welding current value signal Iav changes according to the above equation (8), becomes Iav> Iavs during the peak period Tp, and gradually decreases during the base period Tb, at time t3. In this case, Iav = Iavs. At the time t3, the n-th pulse cycle Tpb (n) ends.

The above-described output control method of the present invention is organized as follows.
(1) A desired external characteristic is set by the above equation (6) by the welding current reference value signal Is, the peak voltage reference value signal Vps, and the inclination setting signal Ks.
(2) The average welding current setting signal Iavs is calculated by the above equation (7) with the peak voltage detection signal Vpd of the nth pulse cycle Tpb (n) as an input.
(3) The average welding current value signal Iav is calculated every moment from the start point of the n-th pulse period Tpb (n) by the above equation (8).
(4) In the base period Tb following the peak period Tp of the n-th pulse period Tpb (n), the n-th time is reached when the average welding current value signal Iav becomes equal to the average welding current setting signal Iavs. The second pulse period Tpb (n) is terminated.

  According to the first embodiment described above, in welding conditions in which an arc is generated in an oblique direction, the change in the apparent arc length is accurately detected by the peak voltage value, and the average welding current and the apparent arc length are calculated. External characteristics indicating the relationship can be formed to desired values. For this reason, the arc length controllability is improved and good welding quality can be obtained.

[Embodiment 2]
FIG. 4 is a timing chart corresponding to FIG. 3 when the rising period Tu and the falling period Td are provided before and after the peak period Tp in the welding current / voltage waveform. During the rising period Tu, a transition current rising from the base current Ib to the peak current Ip is energized as shown in FIG. 9A, and the base voltage Vb is changed to the peak voltage Vp as shown in FIG. A transition voltage rising to is applied. During the subsequent peak period Tp, the peak current Ip is energized as shown in FIG. 9A, and the peak voltage Vp is applied as shown in FIG. During the subsequent falling period Td, as shown in FIG. 6A, a transition current that falls from the peak current Ip to the base current Ib is energized, and as shown in FIG. A transition voltage falling to the voltage Vb is applied. During the subsequent base period Tb, the base current Ib is energized as shown in FIG. 9A, and the base voltage Vb is applied as shown in FIG.

  As shown in FIG. 6C, the average welding current setting signal Iavs is calculated by the above equation (7) with the peak voltage value Vp shown in FIG. The average welding current value signal Iav is calculated by the above equation (8). The value of the average welding current value signal Iav increases during the rising period Tu and the peak period Tp, decreases during the falling period Td and the base period Tb, becomes Iav = Iavs at time t4, and this pulse period is finished.

  The rising period Tu and the falling period Td may be both or either. According to the second embodiment, even when the rising and / or falling of the peak current has an inclination, the same effect as that of the first embodiment described above can be obtained.

[Embodiment 3]
FIG. 5 is a timing chart corresponding to FIG. 3 in the case of AC pulse arc welding in which an electrode minus period Tn is provided before the peak period Tp in the welding current / voltage waveform. During the electrode minus period Tn, as shown in FIG. 6A, the electrode minus current In flow is conducted with the electrode minus polarity, and the electrode minus voltage Vn is applied as shown in FIG. During the subsequent peak period Tp, the peak current Ip is applied by switching to the normal electrode positive polarity as shown in FIG. 6A, and the peak voltage Vp is applied as shown in FIG. During the subsequent base period Tb, the base current Ib is energized as shown in FIG. 9A, and the base voltage Vb is applied as shown in FIG.

  As shown in FIG. 6C, the average welding current setting signal Iavs is calculated by the above equation (7) with the peak voltage value Vp shown in FIG. The average welding current value signal Iav is calculated by the above equation (8). The value of the average welding current value signal Iav increases during the electrode minus period Tn and the peak period Tp, decreases during the base period Tb, and becomes Iav = Iavs at time t4, thus ending this pulse cycle.

  The electrode minus period Tn may be provided before or after the peak period Tp. According to the third embodiment, the same effect as that of the above-described first embodiment can be obtained even in AC pulse arc welding with an electrode minus period Tn.

[Embodiment 4]
As described above, the average welding current average value Iav is calculated by the above equation (8). In the welding current waveform described above with reference to FIG. 3A, the peak current Ip and the base current Ib are set by the welding current setting signal Ics described above with reference to FIG. Therefore, when the welding current setting signal Ics is used instead of the absolute value ia of the welding current io, the above equation (8) is corrected to the following equation.
Iav = (1 / t) · ∫Ics · dt (81) where the elapsed time t is the elapsed time from the start of the pulse cycle, and the integration is performed during this elapsed time t. The same applies to the welding current waveform shown in FIGS. 4 and 5 described above.

Further, in FIG. 3, the average welding current value Iav and the average welding current setting signal Iavs become equal at time t3, the peak current Ip is peaked by the peak current setting value Ips, and the base current Ib is peaked by the base current setting value Ibs. Since the period Tp is preset by the peak period setting value Tps, the following equation is established.
Iavs = (Ips · Tps + Ibs · Tb) / (Tps + Tb)
When the above equation is arranged by the base period Tb, the following equation is obtained.
Tb = (Ips−Iavs) · Tps / (Iavs−Ibs) (91) Therefore, when the pulse period is started and the average welding current setting signal Iavs is calculated from the peak voltage value Vp, the above equation (91) Thus, the base period Tb of the current pulse period can be calculated.

Similarly, in the welding current waveform of FIG. 4, when the average welding current setting signal Iavs is determined, the base period Tb is calculated by the following equation.
Tb = ((A · Tus + Ips · Tps + A · Tds) / (Iavs−Ibs)) − Tus−Tps−Tds
(92) where A = (1/2) · (Ips−Ibs), Tus is a predetermined rising period setting value, and Tds is a predetermined falling period setting value.

Similarly, in the welding current waveform of FIG. 5, when the average welding current setting signal Iavs is determined, the base period Tb is calculated by the following equation.
Tb = ((Ins−Iavs) · Tns + (Ips−Iavs) · Tps) / (Iavs−Ibs)
(93) where Ins is a predetermined electrode minus current set value and Tns is a predetermined electrode minus period set value.

  As described above, according to the fourth embodiment, the base period Tb can be controlled by the welding current setting signal Ics or the welding current waveform parameter, and the same effects as in the first embodiment can be obtained.

It is a figure which shows the external characteristic of the welding power supply which concerns on Embodiment 1 of this invention. It is a block diagram of the welding power supply carrying the output control which forms the external characteristic of FIG. It is a timing chart of each signal in the welding power supply of FIG. FIG. 4 is a timing chart corresponding to FIG. 3 when a rising period Tu and a falling period Td are provided before and after a peak period Tp in a welding current / voltage waveform. FIG. 4 is a timing chart corresponding to FIG. 3 when an electrode minus period Tn is provided before a peak period Tp in a welding current / voltage waveform. It is a figure which shows the external characteristic in a prior art. It is a current and voltage waveform diagram of pulse arc welding in the prior art. FIG. 6 is a current / voltage waveform diagram showing an average value Iav (n) of welding current and an average value Vav (n) of welding voltage in the n-th pulse period Tpb (n) in the prior art. It is a block diagram of the welding power source carrying the output control which forms the external characteristic of FIG. 10 is a timing chart of each signal in the welding power source of FIG. 9. It is a schematic diagram of the arc generation part for demonstrating a subject.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Welding wire 2 Base material 3 Arc 4 Welding torch 5 Feed roll CM Comparison circuit Cm Comparison signal CM2 2nd comparison circuit EI Current error amplification circuit Ei Current error amplification signal ia Welding current absolute value (signal)
IAV average current calculation circuit
Iav Average welding current value (signal)
IAVS average welding current setting circuit Iavs average welding current setting signal Ib base current Ibs base current setting value ICS current setting circuit Ics welding current setting signal ID current detection circuit In electrode minus current Ins electrode minus current setting value io welding current Ip peak current Ips Peak current set value IS Welding current reference value setting circuit Is Welding current reference value (signal)
KS Inclination setting circuit Ks Inclination setting signals L1 to L3 External characteristics La1 and La2 Apparent arc length Lt1 and Lt2 True arc length PF Welding current waveform parameter setting circuit Pf Welding current waveform parameter setting signal SVI Integration circuit Svi Integration value (signal)
Tb Base period Td Falling period Tds Falling period set value Tn Electrode minus period Tns Electrode minus period set value Tp Peak period Tpb Pulse period Tps Peak period set value Tu Falling period Tus Falling period set value va Welding voltage absolute value ( signal)
Vav Average welding voltage value Vb Base voltage VD Voltage detection circuit Vn Electrode minus voltage vo Welding voltage Vp Peak voltage VPD Peak voltage detection circuit
Vpd Peak voltage detection signal VPS Peak voltage reference value setting circuit Vps Peak voltage reference value (signal)
VS Welding voltage reference value setting circuit Vs Welding voltage reference value (signal)

Claims (4)

In an output control method of consumable electrode pulse arc welding in which welding is performed by energizing a welding current with the energization of the peak current during the peak period and the energization of the base current during the base period as one pulse cycle,
The average welding current value is calculated every moment from the start of the nth pulse cycle, the peak voltage value during the peak period is detected, and the average welding current set value is determined according to a predetermined external characteristic using the peak voltage value as an input. To calculate
When the average welding current value becomes equal to the average welding current set value during the base period following the peak period, the nth pulse cycle is ended, and then the (n + 1) th pulse cycle is started. A method for controlling the output of consumable electrode pulse arc welding.   2. The method of controlling output of consumable electrode pulse arc welding according to claim 1, wherein the peak current has a slope at the rise and / or fall.   3. The consumable electrode pulse arc welding according to claim 1 or 2, wherein an electrode minus period is provided before the peak period, and an electrode minus current is applied by switching to an electrode minus polarity during the electrode minus period. Output control method. The output control method for consumable electrode pulse arc welding according to any one of claims 1 to 3, wherein the average welding current value is calculated by a setting signal of the welding current.

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