JP2010000539A - Output control method in pulse arc welding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make satisfactory a droplet transfer state in a small current region in consumption electrode pulse arc welding where arc length control is performed by feedback-controlling peak current and base current. <P>SOLUTION: A welding current variation ΔI is calculated in accordance with a voltage error between a welding voltage set value Vr and the detected value Vd of welding voltage. Further, a preset peak period Tp, a base period Tb and an allocation ratio α (0≤α≤1) are input, and a peak current set signal Ipr=Ipr(n-1)+(ΔI×(Tp+Tb)×α/Tp) is calculated, so as to control peak current. Simultaneously, a base current set signal Ibr=Ibr(n-1)+(ΔI×(Tp+Tb)×(1-α)/Tp) is calculated, so as to control base current. In this way, the allocation of the welding current variation ΔI to the base current can be reduced compared with the peal current, and, a droplet transfer state in a small current region can be made satisfactory. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pulse arc welding output control method for stabilizing a welding state by improving the output control method in consumable electrode pulse arc welding.

  FIG. 7 is a general current / voltage waveform diagram of consumable electrode pulse arc welding. FIG. 4A shows the welding current Iw for energizing the arc, and FIG. 4B shows the welding voltage Vw between the welding wire and the base material. Hereinafter, a description will be given with reference to FIG.

  During the peak period Tp from time t1 to t2, as shown in FIG. 4A, a peak current Ip greater than the critical current value is applied to transfer the droplets from the welding wire, and shown in FIG. Thus, the peak voltage Vp proportional to the arc length is applied between the welding wire and the base material.

  During the base period Tb from time t2 to t3, as shown in FIG. 6A, the base current Ib having a constant current value is energized to prevent the formation of droplets, as shown in FIG. In addition, a base voltage Vb is applied. The welding is performed by repeating the period from time t1 to t3 as the pulse period Tpb.

  In order to perform good pulse arc welding, it is important to maintain the arc length at an appropriate value. In order to maintain the arc length at an appropriate value, the following output control is performed. The arc length is substantially proportional to the welding voltage average value Vav indicated by a broken line in FIG. For this purpose, the welding voltage average value Vav is detected, and the output for changing the welding current average value Iav indicated by the broken line in FIG. 5A so that the detected value becomes equal to the welding voltage set value corresponding to the appropriate arc length. Take control. When the welding voltage average value Vav is larger than the welding voltage set value, the arc length is longer than the appropriate value. Therefore, the welding current average value Iav is decreased to reduce the wire melting rate and shorten the arc length. To do. On the other hand, when the welding voltage average value Vav is smaller than the welding voltage set value, the arc length is shorter than the appropriate value, so the welding current average value Iav is increased to increase the wire melting rate and the arc length is increased. Like that. As the welding voltage average value Vav, a value obtained by smoothing the welding voltage Vw is generally used. For this reason, in the following description, the welding voltage average value Vav and the welding voltage smoothing value Vav are used in the same meaning.

  In the above, as means for changing the welding current average value Iav, changing at least one of the peak period Tp, the base period Tb, the peak current Ip, or the base current Ib is performed. In particular, the current characteristic modulation control for setting the peak period Tp and the base period Tb to predetermined values and changing the peak current Ip and / or the base current Ib to change the welding current average value Iav has the following characteristics. There is. In multi-electrode pulse arc welding in which a plurality of welding wires are adjacent and welding is performed while simultaneously generating arcs, the energization of the peak current Ip is synchronized in order to suppress instability of the welding state due to interference between the arcs. Is done. In order to achieve this synchronization, it is necessary to perform the above current value modulation control in which the peak period Tp and the base period Tb are constant values. Further, the weldability is improved by motivating the weaving of the welding torch and the peak period Tp. In such a case, the current value modulation control is advantageous. The present invention can be applied when arc length control is performed by this current value modulation control.

  The above current value modulation control is performed as follows. A welding voltage set value Vr corresponding to an appropriate arc length is set in advance. A welding voltage smoothing value Vav is detected. A voltage error ΔV = (Vr−Vav) between the welding voltage setting value Vr and the welding voltage smoothing value Vav is calculated. The error ΔV is multiplied by a predetermined amplification factor G to calculate a welding current change amount ΔI = G × ΔV. Then, the peak current Ip and the base current Ib are changed by the welding current change amount ΔI. That is, the current value modulation control changes the welding current average value Iav by changing the peak current Ip and the base current Ib in accordance with the voltage error proportional to the error between the appropriate arc length and the current arc length.

JP 2004-237342 A

  In the above-described current value modulation control of the prior art, the peak current Ip and the base current Ib change by the welding current change amount ΔI calculated according to the voltage error ΔV. However, the peak current value Ip is a large current of 400 A or more, and the base current value Ib is a small current of 70 A or less. For this reason, if the welding current change amount ΔI of the same value is changed, the base current Ib changes relatively large compared to the peak current Ip, so that the stability of the droplet transfer state may deteriorate. Arise. In particular, when the wire feed speed is low, that is, when the welding current average value Iav is in a small current region, the droplet transfer state tends to become unstable if the welding current change amount ΔI is large.

  The above problem will be described below with numerical examples. It is assumed that the voltage error ΔV = 0.1V. If the amplification factor G = 100, the welding current change amount ΔI = 0.1 × 100 = 10 A. Here, when Ip = 550A, Ib = 50A, Tp = 1ms, and Tb = 4ms, the peak current Ip = 550 + 10 = 560A and the base current Ib = 50 + 10 = 60A. In this case, the welding current average value Iav is increased by the welding current change amount ΔI = 10A. Thus, since the change ratio of the base current Ib is larger than the peak current Ip, the influence on the droplet transfer is increased.

  In order to solve this problem, it can be considered that the welding current change amount ΔI with respect to the peak current Ip and the base current Ib is set to different values. However, the amplification factor G for calculating the welding current change ΔI from the voltage error ΔV that is proportional to the error between the appropriate arc length and the current arc length includes the stability and transient response of the arc length control (current value modulation control) system. There is an appropriate value for improving the property. For this reason, if the welding current change amount ΔI with respect to the peak current Ip and the base current Ib is appropriately set to a different value, the change amount of the welding current average value Iav with respect to the voltage error ΔV will deviate from the appropriate value, and the arc length control will be performed. The stability and transient response of the system will deteriorate.

  Therefore, in the present invention, the change amount of the peak current Ip and the change amount of the base current Ib are different while maintaining the change amount of the welding current average value Iav with respect to the voltage error ΔV at an appropriate value that makes the arc length control system stable. It is an object of the present invention to provide an output control method for pulse arc welding that can be set to a predetermined value.

In order to solve the above-described problem, the first invention
The welding wire is fed at a predetermined wire feed speed, and a peak current corresponding to the peak current set value Ipr is applied during a predetermined peak period Tp, and a base current set value is set during a predetermined base period Tb. In a pulse arc welding output control method in which a base current corresponding to Ibr is energized and welding is performed by repeating these energizations as one pulse period,
At the start of the nth pulse cycle, a welding current change amount ΔI is calculated according to a voltage error between a predetermined welding voltage set value and a detected value of the welding voltage, and a distribution ratio α (0 ≦ α ≦ 1) is calculated. Set in advance,
The peak current set value change amount ΔIpr = ΔI × (Tp + Tb) × α / Tp is calculated, and this value is added to the peak current set value in the (n−1) th pulse period to add the value in the nth pulse period. The peak current set value Ipr is calculated to control the peak current,
The base current set value change amount ΔIbr = ΔI × (Tp + Tb) × (1−α) / Tb is calculated, and this value is added to the base current set value in the (n−1) th pulse cycle to calculate the nth time Calculating the base current set value Ibr in a pulse period to control the base current;
An output control method of pulse arc welding characterized by the above.

In the second invention, the distribution ratio α changes according to the wire feeding speed.
An output control method for pulse arc welding according to the first aspect of the invention.

In the third aspect of the invention, the welding wire is fed at a predetermined wire feed speed, and an electrode minus polarity base current corresponding to the electrode minus polarity base current set value Inr is set during a predetermined electrode minus polarity base period Tn. During the predetermined electrode positive polarity peak period Tp, the peak current corresponding to the peak current set value Ipr is supplied, and during the predetermined electrode positive polarity base period Tb, the base current corresponding to the base current set value Ibr is applied. In the output control method of pulse arc welding in which energization is performed and welding is performed by repeating these energizations as one pulse period,
At the start of the nth pulse cycle, a welding current change amount ΔI is calculated according to a voltage error between a predetermined welding voltage setting value and a welding voltage detection value, and a distribution ratio α (0 ≦ α ≦ 1) and Base period distribution ratio β (0 ≦ β ≦ 1) is set in advance,
The peak current set value change amount ΔIpr = ΔI × (Tn + Tp + Tb) × α / Tp is calculated, and this value is added to the peak current set value in the (n−1) th pulse cycle, and the peak current set value change in the nth pulse cycle. The peak current set value Ipr is calculated to control the peak current,
Base current set value change amount ΔIbr = ΔI × (Tn + Tp + Tb) × (1−α) × β / Tb is calculated, and this value is added to the base current set value in the (n−1) th pulse period to add the nth Calculating the base current set value Ibr in the second pulse period to control the base current;
Electrode negative polarity base current set value change amount ΔInr = ΔI × (Tn + Tp + Tb) × (1-α) × (1-β) / Tn is calculated, and this value is calculated as the electrode negative polarity in the (n−1) th pulse period. Adding the base current set value to calculate the electrode negative polarity base current set value Inr in the nth pulse period to control the electrode negative polarity base current;
An output control method of pulse arc welding characterized by the above.

In the fourth aspect of the invention, the distribution ratio α and / or the base period distribution ratio β changes according to the wire feed speed.
The output control method of pulse arc welding according to claim 3, wherein:

  According to the first aspect of the invention, the stability and transient response of the arc length control system are improved by optimizing the amount of change in the welding current according to the voltage error between the welding voltage setting value and the welding voltage detection value. can do. Further, by distributing the welding current change amount between the peak current and the base current at an appropriate distribution ratio, the burden on the base current can be reduced, and the droplet transfer state can be kept good.

  According to the second aspect of the invention, in addition to the effect of the first aspect, by changing the distribution ratio in conjunction with the wire feed speed, the droplets over the entire current range from the small current range to the large current range. The transition state can be further improved.

  According to the third aspect of the invention, the effect of the first aspect of the invention can be achieved in AC pulse arc welding in which a part of the base period is reversed to the electrode negative polarity.

  According to the fourth aspect of the invention, in addition to the effect of the third aspect, the distribution ratio and the base period distribution ratio are changed in conjunction with the wire feeding speed, so that the entire current range from the small current range to the large current range can be changed. The droplet transfer state can be further improved over the current range.

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

[Embodiment 1]
FIG. 1 is a block diagram of a welding power source for carrying out an output control method of pulse arc welding according to Embodiment 1 of the present invention. Hereinafter, each block will be described with reference to FIG.

  The power supply main circuit PM receives a commercial power supply (not shown) such as three-phase 200V as input, performs output control by inverter control according to a drive signal Dv described later, and outputs a welding current Iw and a welding voltage Vw. Although not shown, the power supply main circuit PM includes a primary rectifier that rectifies commercial power, a capacitor that smoothes the rectified direct current, an inverter circuit that converts the smoothed direct current into high-frequency alternating current according to the drive signal Dv, A high-frequency transformer that steps down the high-frequency alternating current to a voltage value suitable for arc welding, a secondary rectifier that rectifies the stepped-down high-frequency alternating current, and a reactor that smoothes the rectified direct current. The welding wire 1 is fed through the welding torch 4 by the rotation of the feed roll 5 coupled to the wire feed motor WM, and the arc 3 is generated between the base metal 2 and welding is performed.

  The welding voltage detection circuit VD detects and smoothes the welding voltage Vw, and outputs a welding voltage detection signal Vd. The welding voltage setting circuit VR outputs a predetermined welding voltage setting signal Vr. The voltage error amplification circuit EV outputs a welding current change amount signal ΔI calculated by multiplying a voltage error between the welding voltage setting signal Vr and the welding voltage detection signal Vd by a predetermined amplification factor.

  The distribution ratio setting circuit HR outputs a predetermined distribution ratio signal α. The value of the distribution ratio signal α is in the range of 0 ≦ α ≦ 1.0. The peak current setting circuit IPR receives the distribution ratio signal α, the peak current setting signal Ipr (n−1) in the previous period, and the welding current change amount signal ΔI at the start of the n-th pulse period, A peak current set value change amount ΔIpr = ΔI × (Tp + Tb) × α / Tp is calculated and a peak current set signal Ipr = Ipr (n−1) + ΔIpr is output. Here, Tp is the length of the peak period, and Tb is the length of the base period. Both values are predetermined values. The base current setting circuit IBR receives the distribution ratio signal α, the base current setting signal Ibr (n−1) in the previous period, and the welding current change amount signal ΔI as inputs at the start of the n-th pulse period. Then, the base current set value change amount ΔIbr = ΔI × (Tp + Tb) × (1−α) / Tb is calculated, and the base current set signal Ibr = Ibr (n−1) + ΔIbr is output.

  The pulse cycle timer circuit TPB outputs a pulse cycle signal Tpb that is at a high level during a predetermined peak period Tp and is at a low level during a predetermined base period Tb. The switching circuit SW receives the pulse period signal Tpb, the peak current setting signal Ipr, and the base current setting signal Ibr, and when the pulse period signal Tpb is at a high level (peak period Tp), the peak current setting is performed. The signal Ipr is output as the welding current setting signal Ir, and the base current setting signal Ibr is output as the welding current setting signal Ir during the low level (base period Tb). The welding current detection circuit ID detects the welding current Iw and outputs a welding current detection signal Id. The current error amplification circuit EI amplifies an error between the welding current setting signal Ir and the welding current detection signal Id and outputs a current error amplification signal Ei. The drive circuit DV receives the current error amplification signal Ei as input, performs pulse width modulation control, and outputs a drive signal Dv for driving the inverter circuit based on the result.

  The wire feed speed setting circuit FR outputs a wire feed speed setting signal Fr for setting the wire feed speed of the welding wire 1. The feed control circuit FC receives the wire feed speed setting signal Fr as an input, and feeds the feed control signal Fc for feeding the welding wire 1 at a speed determined by the wire feed speed setting signal Fr. Output to motor WM.

  The arithmetic expressions used in the peak current setting circuit IPR and the base current setting circuit IBR will be described below. The welding current change amount signal ΔI is calculated by multiplying the voltage error proportional to the error between the appropriate arc length and the current arc length by the amplification factor. This amplification factor is set so that the arc length control system is stable and the transient response is good. At this time, an integral element and a differential element may be added to form a general PID controller. Moreover, a peak voltage can also be used instead of the welding voltage smoothing value. This is because the peak voltage value is proportional to the arc length during the peak period Tp, so that the welding state can be stabilized also by controlling the arc length. By multiplying the value of the welding current change amount signal ΔI by (Tp + Tb), an integrated value of the welding current change amount in the n-th pulse period is calculated. The distribution ratio signal α is a value indicating a ratio for distributing the integral value to the peak period. Therefore, 1−α is a value indicating the ratio of distributing the integral value to the base period. For example, when α = 0.6, it means that 60% of the integral value is borne during the peak period and the remaining 40% is borne during the base period. Thus, each value of the peak current setting signal Ipr and the base current setting signal Ibr is calculated. In this case, the amount of change in the welding current average value Iav is only equal to ΔI. Therefore, the stability and transient response of the arc length control system are maintained assured.

Hereinafter, the above calculation will be described with numerical examples. If Ipr (n-1) = 550A, Ibr (n-1) = 50A, Tp = 1ms, Tb = 4ms, ΔI = 10A and α = 0.5,
Ipr = 550 + (10 × 5 × 0.5 / 1) = 575A
Ibr = 50 + (10 × 5 × 0.5 / 4) = 56.25A.
Thus, the burden on the base current is lighter than 10A in the prior art.

When the wire feeding speed is made faster than in the case of the above numerical example, the set value of the peak period Tp is normally kept as it is, but the set value of the base period Tb is decreased. That is, the frequency is increased by shortening the pulse period in accordance with the wire feed speed. Therefore, if Ipr (n-1) = 550A, Ibr (n-1) = 50A, Tp = 1ms, Tb = 2ms, ΔI = 10A and α = 0.5,
Ipr = 550 + (10 × 3 × 0.5 / 1) = 565A,
Ibr = 50 + (10 × 3 × 0.5 / 2) = 57.5A.
Thus, the burden on the base current is still reduced.

  According to the first embodiment described above, the arc length control system has good stability and transient response by optimizing the amount of change in the welding current in accordance with the voltage error between the welding voltage setting value and the welding voltage detection value. Can be. Further, by distributing the welding current change amount between the peak current and the base current at an appropriate distribution ratio, the burden on the base current can be reduced, and the droplet transfer state can be kept good.

[Embodiment 2]
FIG. 2 is a block diagram of a welding power source for carrying out the output control method of pulse arc welding according to Embodiment 2 of the present invention. In the figure, the same blocks as those in FIG. 1 described above are denoted by the same reference numerals, and description thereof is omitted. Hereinafter, the second distribution ratio setting circuit HR2 indicated by a broken line different from FIG. 1 will be described with reference to FIG.

  The second distribution ratio setting circuit HR2 receives the wire feed speed setting signal Fr and outputs a distribution ratio signal α according to a predetermined function α = f (Fr). An example of this function is shown in FIG. In the figure, the horizontal axis represents the wire feed speed setting signal Fr (m / min), and the vertical axis represents the distribution ratio signal α. As shown in the figure, the function f (Fr) is a straight line with a downward slope where α = 0.6 when Fr = 0 m / min and α = 0.4 when Fr = 20 m / min. . By doing this, when the wire feed speed is low, that is, when the welding current average value is small, the burden on the base current is further reduced, thereby further reducing the state of droplet transfer in the small current region. Good.

  According to the second embodiment described above, in addition to the effects of the first embodiment, the distribution ratio is changed in conjunction with the wire feed speed, so that the melting is performed over the entire current region from the small current region to the large current region. The droplet transfer state can be further improved.

  The distribution ratio α may be changed according to the welding method, the type of welding wire, the base material material, and the like.

[Embodiment 3]
FIG. 4 is a current / voltage waveform diagram showing an output control method of pulse arc welding according to Embodiment 3 of the present invention. FIG. 4A shows the welding current Iw for energizing the arc, and FIG. 4B shows the welding voltage Vw between the welding wire and the base material. This figure shows the case of AC pulse arc welding in which a part of the base period is an electrode minus polarity period. In the figure, the upper side of 0A and 0V is the electrode positive polarity EP, and the lower side is the electrode negative polarity EN. Hereinafter, a description will be given with reference to FIG.

  During the predetermined electrode minus polarity base period Tn from time t1 to t2, as shown in FIG. 5A, the electrode minus polarity base current In having a constant current value is applied to prevent the formation of droplets. As shown in FIG. 5B, an electrode negative polarity voltage Vn is applied.

  During the electrode positive polarity peak period Tp from time t2 to t3, as shown in FIG. 6A, a peak current Ip greater than the critical current value is applied to transfer the droplets from the welding wire, and FIG. ), A peak voltage Vp is applied between the welding wire and the base material.

  During the electrode positive polarity base period Tb from time t3 to t4, as shown in FIG. 6A, the base current Ib having a constant current value is energized to prevent the formation of droplets. As shown, the base voltage Vb is applied. Then, the period from time t4 to t5 returns to the electrode minus polarity base period Tn again. Welding is performed by repeating the period from time t1 to t4 as the pulse period Tpb. Therefore, a part of the base period from time t3 to t5 (time t4 to t5) has an electrode negative polarity and is AC pulse arc welding.

  In order to perform good pulse arc welding, it is important to maintain the arc length at an appropriate value. In order to maintain the arc length at an appropriate value, the following output control is performed. The arc length is substantially proportional to the welding voltage average value Vav (average value of the absolute value of the welding voltage Vw) indicated by a broken line in FIG. For this purpose, the welding voltage average value Vav is detected, and the welding current average value Iav (welding current Iw) indicated by the broken line in FIG. 9A is set so that the detected value becomes equal to the welding voltage setting value corresponding to the appropriate arc length. The output is controlled to change the average value of the absolute values of When the welding voltage average value Vav is larger than the welding voltage set value, the arc length is longer than the appropriate value. Therefore, the welding current average value Iav is decreased to reduce the wire melting rate and shorten the arc length. To do. On the other hand, when the welding voltage average value Vav is smaller than the welding voltage set value, the arc length is shorter than the appropriate value, so the welding current average value Iav is increased to increase the wire melting rate and the arc length is increased. Like that.

  In the above, as means for changing the welding current average value Iav, current value modulation control for changing the electrode negative polarity base current In, the peak current Ip, and the base current Ib is performed. Hereinafter, the current value modulation control according to the third embodiment will be described.

In the figure, it is assumed that the pulse period from time t1 to t4 is the nth pulse period. Therefore, before the time t1, it is the (m-1) th pulse cycle.
(1) A voltage error between the welding voltage average value Vav and a predetermined voltage setting value Vr is calculated at time t1, which is the starting point of the nth pulse cycle.
(2) A welding current change amount ΔI is calculated based on the voltage error.
(3) The following calculation is performed with the welding current change amount ΔI, the predetermined distribution ratio α and the base period distribution ratio β as inputs.
Peak current change ΔIp = ΔI × (Tn + Tp + Tb) × α / Tp
Base current change amount ΔIb = ΔI × (Tn + Tp + Tb) × (1−α) × β / Tb
Electrode negative polarity base current change amount ΔIn = ΔI × (Tn + Tp + Tb) × (1-α) × (1-β) / Tn
(4) The peak current change amount ΔIp, base current change amount ΔIb, and electrode negative polarity base current change amount in each of the peak current value, base current value, and electrode negative polarity base current value in the (n−1) th pulse period. By adding ΔIn, the peak current value, the base current value, and the electrode negative polarity base current value in the nth pulse period are calculated and energized.

  FIG. 5 is a block diagram of a welding power source for carrying out the above-described output control method of pulse arc welding according to Embodiment 3 of the present invention. In the figure, the same reference numerals are given to the same blocks as those in FIG. Hereinafter, each block will be described with reference to FIG.

  The inverter circuit INV receives an AC commercial power supply (not shown) such as a three-phase 200V as an input, performs inverter control on a rectified and smoothed DC voltage according to a drive signal Dv described later, and outputs a high-frequency AC. The inverter transformer INT steps down the high-frequency AC voltage to a voltage value suitable for arc welding. The secondary rectifiers D2a to D2d rectify the stepped-down high-frequency alternating current into direct current. The electrode plus polarity transistor PTR is turned on by an electrode plus polarity drive signal Pd described later, and the output of the welding power source becomes the electrode plus polarity EP. The electrode negative polarity transistor NTR is turned on by an electrode negative polarity drive signal Nd described later, and the output of the welding power source becomes the electrode negative polarity EN. The reactor WL smooths the rippled output. The welding wire 1 is fed through the welding torch 4 by the rotation of the feed roll 5 coupled to the wire feed motor WM, and an arc 3 is generated between the base metal 2 and the welding wire 1.

  The welding voltage detection circuit VD detects the welding voltage Vw, smoothes the absolute value thereof, and outputs a welding voltage detection signal Vd. The welding voltage setting circuit VR outputs a predetermined welding voltage setting signal Vr. The voltage error amplification circuit EV outputs a welding current change amount signal ΔI calculated by multiplying a voltage error between the welding voltage setting signal Vr and the welding voltage detection signal Vd by a predetermined amplification factor.

  The third distribution ratio setting circuit HR3 receives a wire feed speed setting signal Fr, which will be described later, and outputs a distribution ratio signal α according to a predetermined function α = f (Fr), and a predetermined function β = g (Fr ) To output a base period distribution ratio signal β. Examples of these functions will be described later with reference to FIG. The value of the distribution ratio signal α is in the range of 0 ≦ α ≦ 1.0, and the value of the base period distribution ratio signal β is in the range of 0 ≦ β ≦ 1.0.

  The peak current setting circuit IPR receives the distribution ratio signal α, the peak current setting signal Ipr (n−1) in the previous period, and the welding current change amount signal ΔI at the start of the n-th pulse period, A peak current set value change amount ΔIpr = ΔI × (Tn + Tp + Tb) × α / Tp is calculated and a peak current set signal Ipr = Ipr (n−1) + ΔIpr is output. Here, Tn is the length of the electrode negative polarity base period, Tp is the length of the electrode positive polarity peak period, and Tb is the length of the electrode positive polarity base period. These values are predetermined values. The base current setting circuit IBR is configured such that the distribution ratio signal α, the base period distribution ratio signal β, the base current setting signal Ibr (n−1) in the previous period, and the Using the welding current change amount signal ΔI as an input, the base current set value change amount ΔIbr = ΔI × (Tn + Tp + Tb) × (1−α) × β / Tb is calculated and the base current set signal Ibr = Ibr (n−1) + ΔIbr Is output. The electrode negative polarity base current setting circuit INR is configured such that the distribution ratio signal α, the base period distribution ratio signal β, and the electrode negative polarity base current setting signal Inr (n -1) and the welding current change amount signal ΔI described above are input, and electrode negative polarity base current set value change amount ΔInr = ΔI × (Tn + Tp + Tb) × (1-α) × (1-β) / Tn is calculated. The electrode negative polarity base current setting signal Inr = Inr (n−1) + ΔInr is output.

  The second pulse period timer circuit TPB2 has a value of 1 during a predetermined electrode negative polarity base period Tn, and has a value of 2 during a subsequent predetermined electrode positive polarity peak period Tp. During the electrode positive polarity base period Tb, the value becomes 3, and these operations are repeated to output the pulse period signal Tpb. The second switching circuit SW2 receives the pulse cycle signal Tpb, the peak current setting signal Ipr, the base current setting signal Ibr, and the electrode negative polarity base current setting signal Inr as inputs, and the pulse cycle signal Tpb = 1. At this time, the electrode negative polarity base current setting signal Inr is output as the welding current setting signal Ir. When the pulse cycle signal Tpb = 2, the peak current setting signal Ipr is output as the welding current setting signal Ir, and the pulse cycle signal Tpb. When = 3, the base current setting signal Ibr is output as the welding current setting signal Ir. The welding current detection circuit ID detects the welding current Iw, converts it into an absolute value, and outputs a welding current detection signal Id. The current error amplification circuit EI amplifies an error between the welding current setting signal Ir and the welding current detection signal Id and outputs a current error amplification signal Ei. The drive circuit DV receives the current error amplification signal Ei as input, performs pulse width modulation control, and outputs a drive signal Dv for driving the inverter circuit INV based on the result.

  The wire feed speed setting circuit FR outputs a wire feed speed setting signal Fr for setting the wire feed speed of the welding wire 1. The feed control circuit FC receives the wire feed speed setting signal Fr as an input, and feeds the feed control signal Fc for feeding the welding wire 1 at a speed determined by the wire feed speed setting signal Fr. Output to motor WM.

  The secondary drive circuit DVS outputs the electrode minus polarity drive signal Nd when the pulse cycle timer signal Tpb = 1, and the electrode plus polarity drive signal Pd when the pulse cycle timer signal Tpb = 2 or 3. Is output. Thus, the electrode has a negative polarity during the electrode negative polarity base period, and the electrode has a positive polarity during the electrode positive polarity peak period and the electrode positive polarity base period.

  The arithmetic expressions used in the peak current setting circuit IPR, the base current setting circuit IBR, and the electrode negative polarity base current setting circuit INR will be described below. The welding current change amount signal ΔI is calculated by multiplying the voltage error proportional to the error between the appropriate arc length and the current arc length by the amplification factor. This amplification factor is set so that the arc length control system is stable and the transient response is good. At this time, an integral element and a differential element may be added to form a general PID controller. Moreover, a peak voltage can also be used instead of the welding voltage smoothing value. This is because the peak voltage value is proportional to the arc length during the electrode positive polarity peak period Tp, so that the welding state can also be stabilized by controlling the arc length. By multiplying the value of the welding current change amount signal ΔI by (Tn + Tp + Tb), an integrated value of the welding current change amount in the nth pulse period is calculated. The distribution ratio signal α is a value indicating a ratio of distributing the integral value to the electrode positive polarity peak period. Therefore, 1−α is a value indicating the ratio of distributing the integral value to the base period. For example, when α = 0.6, it means that 60% of the integral value is borne during the peak period and the remaining 40% is borne during the base period. Furthermore, the base period distribution ratio signal β is a value indicating a ratio of distributing the integral value distributed in the base period to the electrode positive polarity base period and the electrode negative polarity base period. For example, when α = 0.6 and β = 0.7, 60% of the integral value is borne by the electrode positive polarity peak period, 40% × 70% = 28% is borne by the electrode positive polarity base period, The remaining 12% will be borne by the electrode negative polarity base period. In this way, each value of the peak current setting signal Ipr, the base current setting signal Ibr, and the electrode negative polarity base current setting signal Inr is calculated. In this case, the amount of change in the welding current average value Iav is only equal to ΔI. Therefore, the stability and transient response of the arc length control system are maintained assured. Then, the distribution ratio α and the base period distribution ratio β may be set so that the welding state is stabilized.

  The distribution ratio α and the base period distribution ratio beta may be changed according to the welding method, the type of the welding wire, the base material material, and the like.

  FIG. 6 is a diagram illustrating the functions α = f (Fr) and β = g (Fr) described above. In the figure, the horizontal axis represents the wire feed speed setting signal Fr (m / min), and the vertical axis represents the distribution ratio signal α and the base period distribution ratio signal β. The function f (Fr) shown in the figure is the same as the function of FIG. 3 described above, and α = 0.6 when Fr = 0 m / min, and α = 0.4 when Fr = 20 m / min. It is a descending straight line. As shown in the figure, the function g (Fr) is a straight line that rises to the right where β = 0.4 when Fr = 0 m / min and β = 0.6 when Fr = 20 m / min. . By doing so, when the wire feed speed is low, that is, when the welding current average value is small, the burden on the peak current is increased by the value of α, and the electrode minus polarity is determined by the value of β. By increasing the burden on the base current and further reducing the burden on the base current, the droplet transfer state in the small current region is further improved. The function in the figure is merely an example, and may be changed in a curved shape or a step shape.

  According to the third embodiment described above, the present invention can be applied to AC pulse arc welding, and the same effects as in the first and second embodiments can be achieved.

It is a block diagram of the welding power supply which concerns on Embodiment 1 of this invention. It is a block diagram of the welding power supply which concerns on Embodiment 2 of this invention. In Embodiment 2 of this invention, it is a figure which illustrates the relationship between the wire feeding speed setting signal Fr and the distribution ratio signal (alpha). It is an electric current and voltage waveform diagram which shows the output control method of the pulse arc welding which concerns on Embodiment 3 of this invention. It is a block diagram of the welding power supply which concerns on Embodiment 3 of this invention. In Embodiment 3 of this invention, it is a figure which illustrates the relationship between the wire feed speed setting signal Fr, distribution ratio signal (alpha), and base period distribution ratio signal (beta). It is a current / voltage waveform diagram in pulse arc welding of the prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Welding wire 2 Base material 3 Arc 4 Welding torch 5 Feed roll D2a-D2d Secondary rectifier DV Drive circuit Dv Drive signal DVS Secondary side drive circuit EI Current error amplification circuit Ei Current error amplification signal EV Voltage error amplification circuit f ( Fr) Function FC Feed control circuit Fc Feed control signal FR Wire feed speed setting circuit Fr Wire feed speed setting signal

G amplification factor g (Fr) function HR distribution ratio setting circuit HR2 second distribution ratio setting circuit HR3 third distribution ratio setting circuit Iav welding current average value Ib base current IBR base current setting circuit Ibr base current setting signal ID welding current detection circuit Id welding current detection signal In electrode negative polarity base current INR electrode negative polarity base current setting circuit Inr electrode negative polarity base current setting signal INT inverter transformer INV inverter circuit Ip peak current IPR peak current setting circuit Ipr peak current setting signal Ir welding current setting Signal Iw Welding current Nd Electrode minus polarity drive signal NTR Electrode minus polarity transistor Pd Electrode plus polarity drive signal PM Power supply main circuit PTR Electrode plus polarity transistor SW Switching circuit SW2 Second switching circuit Tb (electrode plus polarity) Base period Between Tn Electrode negative polarity base period Tp (electrode positive polarity) Peak period TPB Pulse period timer circuit Tpb Pulse period (signal)
TPB2 Second pulse period timer circuit Vav Welding voltage average value (welding voltage smooth value)
Vb Base voltage VD Welding voltage detection circuit Vd Welding voltage detection signal Vn Electrode negative polarity voltage Vp Peak voltage VR Welding voltage setting circuit Vr Welding voltage setting (value / signal)
Vw Welding voltage WM Wire feed motor α Allocation ratio (signal)
β Base period allocation ratio (signal)
ΔI Welding current change (signal)
ΔIb Base current change amount ΔIbr Base current set value change amount ΔIn Electrode minus polarity base current change amount ΔInr Electrode minus polarity base current set value change amount ΔIp Peak current change amount ΔIpr Peak current set value change amount ΔV Voltage error

Claims (4)

The welding wire is fed at a predetermined wire feed speed, and a peak current corresponding to the peak current set value Ipr is applied during a predetermined peak period Tp, and a base current set value is set during a predetermined base period Tb. In a pulse arc welding output control method in which a base current corresponding to Ibr is energized and welding is performed by repeating these energizations as one pulse period,
At the start of the nth pulse cycle, a welding current change amount ΔI is calculated according to a voltage error between a predetermined welding voltage set value and a detected value of the welding voltage, and a distribution ratio α (0 ≦ α ≦ 1) is calculated. Set in advance,
The peak current set value change amount ΔIpr = ΔI × (Tp + Tb) × α / Tp is calculated, and this value is added to the peak current set value in the (n−1) th pulse period to add the value in the nth pulse period. The peak current set value Ipr is calculated to control the peak current,
The base current set value change amount ΔIbr = ΔI × (Tp + Tb) × (1−α) / Tb is calculated, and this value is added to the base current set value in the (n−1) th pulse cycle to calculate the nth time Calculating the base current set value Ibr in a pulse period to control the base current;
An output control method of pulse arc welding characterized by the above. The distribution ratio α changes according to the wire feeding speed.
The output control method of pulse arc welding according to claim 1. The welding wire is fed at a predetermined wire feed speed, and an electrode negative polarity base current corresponding to the electrode negative polarity base current setting value Inr is energized during a predetermined electrode negative polarity base period Tn. During the electrode positive polarity peak period Tp, a peak current corresponding to the peak current set value Ipr is energized, and during the predetermined electrode plus polarity base period Tb, a base current corresponding to the base current set value Ibr is energized. In the output control method of pulse arc welding in which welding is repeated with one pulse period as
At the start of the nth pulse cycle, a welding current change amount ΔI is calculated according to a voltage error between a predetermined welding voltage setting value and a welding voltage detection value, and a distribution ratio α (0 ≦ α ≦ 1) and Base period distribution ratio β (0 ≦ β ≦ 1) is set in advance,
The peak current set value change amount ΔIpr = ΔI × (Tn + Tp + Tb) × α / Tp is calculated, and this value is added to the peak current set value in the (n−1) th pulse cycle, and the peak current set value change in the nth pulse cycle. The peak current set value Ipr is calculated to control the peak current,
Base current set value change amount ΔIbr = ΔI × (Tn + Tp + Tb) × (1−α) × β / Tb is calculated, and this value is added to the base current set value in the (n−1) th pulse period to add the nth Calculating the base current set value Ibr in the second pulse period to control the base current;
Electrode negative polarity base current set value change amount ΔInr = ΔI × (Tn + Tp + Tb) × (1-α) × (1-β) / Tn is calculated, and this value is calculated as the electrode negative polarity in the (n−1) th pulse period. Adding the base current set value to calculate the electrode negative polarity base current set value Inr in the nth pulse period to control the electrode negative polarity base current;
An output control method of pulse arc welding characterized by the above. The distribution ratio α and / or the base period distribution ratio β changes according to the wire feeding speed.
The output control method for pulse arc welding according to claim 3.

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