Pulse arc welding control method and pulse arc welding power supply

Abstract

In consumable electrode pulsed arc welding, the goal is to suppress the amount of spatter generated even when a short circuit occurs between the welding wire and the base metal, thereby achieving good welding quality. [Solution] In a pulse arc welding control method in which welding is performed by repeatedly applying a welding current Iw during the peak rise period, peak period, peak fall period, and base period as one pulse period and controlling the arc length based on the welding voltage set value, the welding wire feed speed Fw is set to a positive feed peak value that is larger than the average positive feed speed value during the peak period from time t2 to t3, and is set to the average positive feed speed value during the base period from time t4 to t41 to cause a short circuit, and when a short circuit occurs at time t41 it is set to a reverse feed peak value and the reverse feed peak value is maintained even when the short circuit is released at time t42.

Description

Technical Field

[0001] The present invention relates to a pulsed arc welding control method and a pulsed arc welding power source for feeding and welding a welding wire.

Background Art

[0002] Pulsed arc welding for feeding and welding a welding wire is used for welding steel and the like. In this pulsed arc welding, a welding wire is fed, a peak rising current that rises from the value of the base current to the value of the peak current is energized during the peak rising period, the peak current is energized during the peak period, a peak falling current that falls from the value of the peak current to the value of the base current is energized during the peak falling period, and the base current is energized during the base period. The energization of these welding currents is repeated as one pulse cycle to perform welding. In pulsed arc welding, by making one droplet transfer state per pulse cycle, generation of spatter is reduced and a beautiful bead appearance can be obtained.

[0003] In the invention of Patent Document 1, during a predetermined period from a first point during the peak period to a second point during the base period, the feeding speed of the welding wire is made lower than the feeding speed at the rising point of the peak current, or reverse feeding is performed in which the welding wire is fed in a direction away from the welding object.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In pulsed arc welding, a short circuit between the welding wire and the base metal results in increased spatter generation and poor welding quality. Therefore, the present invention aims to provide a pulsed arc welding control method and a pulsed arc welding power supply that can suppress increased spatter generation and achieve good welding quality even when a short circuit between the welding wire and the base metal occurs. [Means for solving the problem]

[0006] A pulse arc welding control method provided by a first aspect of the present invention involves feeding a welding wire in both forward and reverse directions, supplying a peak rise current that rises from the base current value to the peak current value during the peak rise period, supplying the peak current during the peak period, supplying a peak fall current that decreases from the peak current value to the base current value during the peak fall period, supplying the base current during the base period, repeating the supply of these welding currents as one pulse period, and performing arc length control based on a welding voltage set value to perform welding. In this pulse arc welding control method, an average feeding speed set value for the welding wire is set, the feeding speed is set to a forward feeding peak value that is greater than the average feeding speed set value during the peak period, to the average feeding speed set value during the base period, to the reverse feeding peak value if a short circuit occurs during the base period, to maintain the reverse feeding peak value even after the short circuit is released, and to set the forward feeding peak value of the next pulse period to the average feeding speed set value if the short circuit does not occur during the base period.

[0007] In a preferred embodiment of the present invention, if the short circuit does not occur during the base period, the integral value of the peak current in the next pulse period is made larger.

[0008] In a preferred embodiment of the present invention, the start of the peak rise period is delayed until the short circuit is released.

[0009] In a preferred embodiment of the present invention, when the welding voltage setting value is equal to the reference voltage setting value, the base period is set to the reference base period; when the welding voltage setting value is less than the reference voltage setting value, the base period is made longer than the reference base period; and when the welding voltage setting value is greater than the reference voltage setting value, the base period is made shorter than the reference base period.

[0010] In a preferred embodiment of the present invention, at least one of the forward feed peak value and the reverse feed peak value is modulated and controlled so that the average value of the feed speed is equal to the average feed speed set value.

[0011] A pulse arc welding power supply provided by a second aspect of the present invention sets an average feed rate setting value for welding wire, sets the feed rate to a forward feed peak value greater than the average feed rate setting value during the peak period, sets it to the average feed rate setting value during the base period, sets it to a reverse feed peak value if a short circuit occurs during the base period, maintains the reverse feed peak value even after the short circuit is released, and sets the forward feed peak value of the next pulse period to the average feed rate setting value if no short circuit occurs during the base period. [Effects of the Invention]

[0012] According to the present invention, even if a short circuit occurs between the welding wire and the base material, it is possible to suppress the generation of spatter and obtain good welding quality. [Brief explanation of the drawing]

[0013] [Figure 1] This is a block diagram of a welding apparatus for implementing a pulsed arc welding control method according to an embodiment of the present invention. [Figure 2] Figure 1 shows a timing chart of each signal in a welding apparatus illustrating a pulse arc welding control method according to an embodiment of the present invention. The figure shows the case where the value of the welding voltage setting signal Vr is smaller than the value of the reference voltage setting signal Vsr. [Figure 3]Figure 1 shows a timing chart of each signal in a welding apparatus illustrating a pulse arc welding control method according to an embodiment of the present invention. The figure shows the case where the value of the welding voltage setting signal Vr is larger than the value of the reference voltage setting signal Vsr to the extent that a short circuit occurs. [Figure 4] Figure 1 shows a timing chart of each signal in a welding apparatus illustrating a pulse arc welding control method according to an embodiment of the present invention. The figure shows the case where the value of the welding voltage setting signal Vr is larger than the value of the reference voltage setting signal Vsr to the extent that a short circuit does not occur. [Modes for carrying out the invention]

[0014] Embodiments of the present invention will be described below with reference to the drawings.

[0015] Figure 1 is a block diagram of a welding apparatus for implementing a pulse arc welding control method according to an embodiment of the present invention. The welding apparatus mainly consists of a pulse arc welding power supply PS, a robot control device RC, a robot (not shown), etc., enclosed by dashed lines. The following describes each block with reference to the same figure.

[0016] The pulse arc welding power supply PS consists of the following blocks:

[0017] The power control circuit MC takes a commercial AC power supply such as 3-phase 200V (not shown in the diagram) as input and performs output control such as inverter control according to the drive signal Dv described later, outputting a welding voltage Vw and welding current Iw suitable for welding. This power control circuit MC, although not shown in the diagram, includes a primary rectifier circuit for rectifying the commercial AC power supply, a capacitor for smoothing the rectified DC, an inverter circuit for converting the smoothed DC into high-frequency AC according to the drive signal Dv, an inverter transformer for stepping down the high-frequency AC to a voltage value suitable for welding, and a secondary rectifier circuit for rectifying the stepped-down high-frequency AC.

[0018] The reactor WL is inserted between the positive output of the power control circuit MC and the welding torch 4, and smooths the output of the power control circuit MC.

[0019] The wire feed motor WM is rotationally driven by a wire feed control signal Fc described later. The welding wire 1 is fed forward and backward at a wire feed speed Fw through the welding torch 4 by the rotation of a wire feed roll 5 coupled to the wire feed motor WM, and an arc 3 is generated between the wire and the base material 2. The wire feed motor WM and the welding torch 4 are mounted on a robot. A welding voltage Vw is applied between a power supply tip (not shown) in the welding torch 4 and the base material 2, and a welding current Iw flows.

[0020] The welding current average value setting circuit IAR outputs a predetermined welding current average value setting signal Iar. The average wire feed speed setting circuit FAR outputs an average wire feed speed setting signal Far corresponding to the welding current average value setting signal Iar. The reference voltage setting circuit VSR outputs a reference voltage setting signal Vsr for setting an appropriate arc length corresponding to the welding current average value setting signal Iar.

[0021] The voltage fine adjustment circuit DVR outputs a predetermined voltage fine adjustment signal Dvr. The value of the voltage fine adjustment signal Dvr is a real number in the range of, for example, -5V to +5V. The welding voltage setting circuit VR inputs the reference voltage setting signal Vsr and the voltage fine adjustment signal Dvr, adds the two values, and outputs a welding voltage setting signal Vr. Therefore, the welding voltage setting signal Vr is a signal obtained by finely adjusting the value of the reference voltage setting signal Vsr set univariately by the welding current average value setting signal Iar by the value of the voltage fine adjustment signal Dvr.

[0022] The welding voltage detection circuit VD detects the welding voltage Vw and outputs a welding voltage detection signal Vd. The welding voltage averaging circuit VAV averages (passes through a low-pass filter) the welding voltage detection signal Vd and outputs a welding voltage average value signal Vav. The voltage error amplification circuit EV amplifies the error between the welding voltage setting signal Vr(+) and the welding voltage average value signal Vav(-) and outputs a voltage error amplification signal Ev.

[0023] ? The current modulation circuit IC takes the above-mentioned voltage error amplification signal Ev as input and performs PI (proportional-integral) control or PID (proportional-integral-derivative) control, outputting a peak current setting signal Ipr and a base current setting signal Ibr. This circuit modulates the peak current setting signal Ipr and the base current setting signal Ibr so that the welding voltage average value signal Vav becomes equal to the welding voltage setting signal Vr. As a result, arc length control is performed to maintain the arc length at an appropriate value. Alternatively, only the peak current setting signal Ipr may be modulated, while the base current setting signal Ibr is set to a predetermined value.

[0024] The short-circuit detection circuit SD takes the welding voltage detection signal Vd as input and outputs a short-circuit detection signal Sd that is High level when this value is less than the short-circuit detection value (approximately 10V), indicating that it is in a short-circuit period, and Low level when it is above the short-circuit detection value, indicating that it is in an arc generation period.

[0025] The short-circuit base current setting circuit IBS outputs a predetermined short-circuit base current setting signal Ibs. The value of the short-circuit base current setting signal Ibs is set to be less than or equal to the value of the base current setting signal Ibr during the arc generation period, for example, 30 to 50 A.

[0026] The peak rise period setting circuit TUR outputs a predetermined peak rise period setting signal Tur.

[0027] The peak period setting circuit TPR takes the short-circuit generation signal So (described later) as input and outputs a peak period setting signal Tpr which becomes a predetermined reference peak period when the short-circuit generation signal So is at a high level (when a short circuit occurs during the base period of the previous pulse cycle), and a predetermined increasing peak period when the short-circuit generation signal So is at a low level (when a short circuit does not occur during the base period of the previous pulse cycle). Here, the increasing peak period > reference peak period. This ensures that the integral value of the peak current is larger when a short circuit does not occur during the base period of the previous pulse cycle than when a short circuit occurs.

[0028] The peak-fall-down period setting circuit TKR outputs a predetermined peak-fall-down period setting signal Tkr.

[0029] The base period setting circuit TBR takes the above-mentioned voltage fine adjustment signal Dvr as input, performs the calculation shown in the following equation, and outputs the base period setting signal Tbr. Therefore, when the value of the welding voltage setting signal Vr is equal to the value of the reference voltage setting signal Vsr, the value of the base period setting signal Tbr is set to the reference base period; when the value of the welding voltage setting signal Vr is less than the value of the reference voltage setting signal Vsr, the value of the base period setting signal Tbr is made longer than the reference base period; and when the value of the welding voltage setting signal Vr is greater than the value of the reference voltage setting signal Vsr, the value of the base period setting signal Tbr is made shorter than the reference base period. Tbr = (Base period) + Dvr × K However, K is a constant; for example, when Dvr < 0, K = -0.4, and when Dvr > 0, K = -0.2. For example, if the reference base period is 3 ms, then when Dvr = -5V, Tbr = 5 ms, and when Dvr = +5V, Tbr = 2 ms.

[0030] The welding current setting circuit IR takes the following inputs: the first early period setting signal Ta1r (described later), the short-circuit detection signal Sd, the short-circuit base current setting signal Ibs, the peak rise period setting signal Tur, the peak period setting signal Tpr, the peak fall period setting signal Tkr, the base period setting signal Tbr, the peak current setting signal Ipr, and the base current setting signal Ibr, and outputs the welding current setting signal Ir and the timer signal Tm. 1) During the peak rise period Tu determined by the peak rise period setting signal Tur, a timer signal Tm=1 is output, and the peak rise current Iu, which rises from the value of the base current setting signal Ibr to the value of the peak current setting signal Ipr, is output as the welding current setting signal Ir. 2) Subsequently, during the peak period Tp determined by the peak period setting signal Tpr, the timer signal Tm=2 is output, and the peak current setting signal Ipr is output as the welding current setting signal Ir. 3) Subsequently, during the peak fall period Tk determined by the peak fall period setting signal Tkr, a timer signal Tm=3 is output, and the peak fall current Ik, which decreases from the value of the peak current setting signal Ipr to the value of the base current setting signal Ibr, is output as the welding current setting signal Ir. 4) Subsequently, during the base period Tb determined by the base period setting signal Tbr, a timer signal Tm=4 is output. When the short-circuit detection signal Sd is at a low level (arc generation period), a welding current setting signal Ir is output, which is the value of the base current setting signal Ibr. When it is at a high level (short-circuit period), a welding current setting signal Ir is output, which is the value of the short-circuit period base current setting signal Ibs. However, the base period Tb is extended from the moment the short-circuit detection signal Sd changes from a high level (short-circuit period) to a low level (arc generation period) until the period determined by the first early period setting signal Ta1r has elapsed. 5) Repeat steps 1) to 4) above.

[0031] The short-circuit generation circuit SO takes the above-mentioned timer signal Tm and short-circuit discrimination signal Sd as inputs and outputs a short-circuit generation signal So that is set to a high level when the short-circuit discrimination signal Sd changes to a high level (short circuit) when the timer signal Tm = 4 (base period), and is reset to a low level when the timer signal Tm changes to 4 (base period) in the next pulse period.

[0032] The feed rate modulation circuit WC takes the average feed rate setting signal Far and the average feed rate detection signal Fad (described later) as inputs, performs modulation control based on the error amplified signals of both values, and outputs the forward peak value modulation signal Wsc and the reverse peak value setting signal Wrr. This circuit modulates the value of the average feed rate detection signal Fad so that it is equal to the value of the average feed rate setting signal Far. At least one of the forward peak value modulation signal Wsc and the reverse peak value setting signal Wrr may also be modulated.

[0033] The forward transmission peak value setting circuit WSR takes the above-mentioned short-circuit generation signal So, the above-mentioned average feed rate setting signal Far, and the above-mentioned forward transmission peak value modulation signal Wsc as inputs and outputs a forward transmission peak value setting signal Wsr which is the value of the forward transmission peak value modulation signal Wsc when the short-circuit generation signal So is at a high level (when a short circuit occurs during the base period of the previous pulse cycle), and the value of the average feed rate setting signal Far when the short-circuit generation signal So is at a low level (when a short circuit does not occur during the base period of the previous pulse cycle).

[0034] The welding current detection circuit ID detects the above welding current Iw and outputs a welding current detection signal Id. The current error amplification circuit EI amplifies the error between the above welding current setting signal Ir(+) and the above welding current detection signal Id(-) and outputs a current error amplification signal Ei. The drive circuit DV takes this current error amplification signal Ei and the start signal On from the robot control device RC (described later) as input and outputs a drive signal Dv to drive the inverter circuit in the power control circuit MC when the start signal On is at a high level (welding start) by performing pulse width modulation control etc. based on the current error amplification signal Ei. When the start signal On is at a low level (welding stop), it does not output a drive signal Dv.

[0035] The first delay period setting circuit TD1R takes the above-mentioned voltage fine adjustment signal Dvr as input, performs the calculation Td1r[ms] = |Dvr| × 0.1, and outputs the first delay period setting signal Td1r. Therefore, the value of the first delay period setting signal Td1r becomes larger as the absolute value of the difference between the welding voltage setting signal Vr and the reference voltage setting signal Vsr (voltage fine adjustment signal Dvr) increases. For example, when Dvr = -1V, Td1r = 0.1ms, and when Dvr = -5V, Td1r = 0.5ms.

[0036] The second delay period setting circuit TD2R takes the above-mentioned voltage fine adjustment signal Dvr as input, performs the calculation Td2r[ms] = |Dvr| × 0.1, and outputs the second delay period setting signal Td2r. Therefore, the value of the second delay period setting signal Td2r becomes larger as the absolute value of the difference between the welding voltage setting signal Vr and the reference voltage setting signal Vsr (voltage fine adjustment signal Dvr) increases. Here, we assume that Td2r = Td1r, but both values ​​may be set to different values.

[0037] The first early period setting circuit TA1R takes the above-mentioned voltage fine adjustment signal Dvr as input, performs the calculation Ta1r[ms] = |Dvr| × 0.2, and outputs the first early period setting signal Ta1r. Therefore, the value of the first early period setting signal Ta1r becomes larger as the absolute value of the difference between the welding voltage setting signal Vr and the reference voltage setting signal Vsr (voltage fine adjustment signal Dvr) increases. For example, when Dvr = +1V, Ta1r = 0.2ms, and when Dvr = +5V, Ta1r = 1.0ms.

[0038] The second early period setting circuit TA2R takes the above-mentioned voltage fine adjustment signal Dvr as input, performs the calculation Ta2r[ms] = |Dvr| × 0.2, and outputs the second early period setting signal Ta2r. Therefore, the value of the second early period setting signal Ta2r becomes larger as the absolute value of the difference between the welding voltage setting signal Vr and the reference voltage setting signal Vsr (voltage fine adjustment signal Dvr) increases. Here, we assume that Ta2r = Ta1r, but both values ​​may be set to different values.

[0039] The feed rate rise time setting circuit TFUR outputs a predetermined feed rate rise time setting signal Tfur. It is desirable that the feed rate rise time setting signal Tfur is shorter than the peak rise time setting signal Tur.

[0040] The feed rate fall time setting circuit TFKR outputs a predetermined feed rate fall time setting signal Tfkr. It is desirable that the feed rate fall time setting signal Tfkr has a shorter period than the peak fall time setting signal Tkr.

[0041] The long-term short-circuit detection circuit SLD takes the short-circuit detection signal Sd as input and outputs a long-term short-circuit detection signal Sld that becomes high when the short-circuit detection signal Sd changes to a high level and after the long-term short-circuit detection value (approximately 5ms) has elapsed, and then becomes low when the short-circuit detection signal Sd subsequently goes low. Therefore, the long-term short-circuit detection signal Sld is a signal that remains high for the duration of the short circuit, which is longer than or equal to the long-term short-circuit detection value.

[0042] The long-term short-circuit reverse peak value setting circuit WLR outputs a predetermined long-term short-circuit reverse peak value setting signal Wlr. The long-term short-circuit reverse peak value setting signal Wlr is a negative value and has a larger absolute value than the reverse peak value setting signal Wrr mentioned above.

[0043] The feed speed setting circuit FR takes the above-mentioned short-circuit detection signal Sd, long-term short-circuit detection signal Sld, long-term short-circuit reverse peak value setting signal Wlr, voltage fine adjustment signal Dvr, forward peak value setting signal Wsr, average feed speed setting signal Far, reverse peak value setting signal Wrr, timer signal Tm, feed speed rise time setting signal Tfur, feed speed fall time setting signal Tfkr, first delay period setting signal Td1r, second delay period setting signal Td2r, first early period setting signal Ta1r, and second early period setting signal Ta2r as inputs, performs the following processing, and outputs the feed speed setting signal Fr. (1) When the voltage fine adjustment signal Dvr ≤ 0 1) The feed speed setting signal Fr starts changing from the value of the reverse feed peak value setting signal Wrr when the timer signal Tm=1 (peak rise period) has changed and the period of the first delay period setting signal Td1r has elapsed, and changes to the value of the forward feed peak value setting signal Wsr during the period determined by the feed speed rise period setting signal Tfur, and maintains that value. 2) The feed rate setting signal Fr starts changing from the value of the positive feed peak value setting signal Wsr when the timer signal Tm=3 (peak falling period) has changed and the period of the second delay period setting signal Td2r has elapsed, and changes to the value of the average feed rate setting signal Far during the period determined by the feed rate falling period setting signal Tfkr, and maintains that value during the timer signal Tm=4 (base period). 3) The feed rate setting signal Fr becomes the value of the reverse feed peak value setting signal Wrr when the short-circuit detection signal Sd changes to a high level (short circuit), and maintains that value even after the short circuit is released. However, during the period when the long-term short-circuit detection signal Sld is at a high level, the signal switches from the reverse feed peak value setting signal Wrr to the long-term short-circuit reverse feed peak value setting signal Wlr. (2) When the voltage fine adjustment signal Dvr > 0 1) When the feed speed setting signal Fr changes to timer signal Tm=4 (base period), a period of (Tbr-Ta1r) has elapsed, and the short-circuit detection signal Sd is at a low level (arc generation period), the Fr starts changing from the value of the reverse feed peak value setting signal Wrr (or the average feed speed setting signal Far if no short circuit occurred during the base period of the previous pulse cycle), and changes to the value of the forward feed peak value setting signal Wsr during the period determined by the feed speed rise time setting signal Tfur, and maintains that value. 2) The feed rate setting signal Fr starts changing from the value of the positive feed peak value setting signal Wsr after a period of (Tpr - Ta2r) has elapsed from the time the timer signal Tm = 2 (peak period), changes to the value of the average feed rate setting signal Far during the period determined by the feed rate falling period setting signal Tfkr, and maintains that value during the timer signal Tm = 4 (base period). 3) When the short-circuit detection signal Sd changes to a high level (short circuit), the feed speed setting signal Fr becomes the value of the reverse-transmission peak value setting signal Wrr until the timer signal Tm=4 (base period) ends, and maintains that value even after the short circuit is released. However, during the period when the long-term short-circuit detection signal Sld is at a high level, the signal switches from the reverse-transmission peak value setting signal Wrr to the long-term short-circuit reverse-transmission peak value setting signal Wlr.

[0044] The average feed rate detection circuit FAD takes the feed rate setting signal Fr as input, calculates the average value, and outputs the average feed rate detection signal Fad. Alternatively, the feed rate Fw may be directly detected and the average value calculated instead of the feed rate setting signal Fr.

[0045] The feed control circuit FC takes the feed speed setting signal Fr and the start signal On from the robot control device RC (described later) as inputs, and outputs a feed control signal Fc to the feed motor WM when the start signal On is at a high level (welding start), to feed the welding wire 1 at the value of the feed speed setting signal Fr. When the start signal On is at a low level, it outputs a feed control signal Fc to the feed motor WM to stop feeding.

[0046] The robot control device RC moves the robot (not shown in the diagram) according to a pre-programmed work program and outputs a start signal "On" to command the start or stop of welding.

[0047] Figure 2 is a timing chart of each signal in the welding apparatus shown in Figure 1, illustrating a pulse arc welding control method according to an embodiment of the present invention. This figure shows the case where the value of the welding voltage setting signal Vr in Figure 1 is smaller than the value of the reference voltage setting signal Vsr in Figure 1. Figure (A) shows the time variation of the welding current Iw, Figure (B) shows the time variation of the welding voltage Vw, Figure (C) shows the time variation of the welding wire feeding speed Fw, and Figure (D) shows the time variation of the short-circuit generation signal So. The operation of each signal will be explained below with reference to this figure.

[0048] In this figure, because the value of the voltage fine-tuning signal Dvr in Figure 1 is set to a negative value, the value of the welding voltage setting signal Vr in Figure 1 is smaller than the value of the reference voltage setting signal Vsr in Figure 1. When the value of the welding voltage setting signal Vr is equal to the value of the reference voltage setting signal Vsr, the arc length is controlled to an appropriate value. When welding at a welding speed exceeding 1 m / min, the arc length is set shorter than the appropriate value to improve welding quality. In such cases, the value of the welding voltage setting signal Vr is set to a value smaller than the value of the reference voltage setting signal Vsr.

[0049] As shown in Figure (C), the feeding speed Fw is in a forward feeding state when it is a positive value above 0, where the feed is advanced towards the base material, and in a reverse feeding state when it is a negative value below 0, where the feed is advanced away from the base material.

[0050] During the predetermined peak rise period Tu from time t1 to t2, as shown in Figure (A), a peak rise current Iu is supplied, which rises from a current-modulated base current Ib to a current-modulated peak current Ip, and as shown in Figure (B), a peak rise voltage is applied between the welding wire and the base material, which rises from a base voltage Vb to a peak voltage Vp.

[0051] As shown in Figure (D), a short circuit occurred during the base period of the previous pulse cycle prior to time t1, so the short circuit signal So is at a high level. Therefore, the forward transmission peak value setting signal Wsr in Figure 1 is equal to the value of the forward transmission peak value modulation signal Wsc in Figure 1. The short circuit signal So is reset to a low level at the start of the base period at time t4. As shown in Figure (C), the feed rate Fw begins to change from the reverse transmission peak value Wr at a point one delay period Td1 after the start of the peak rise period Tu at time t1. It then changes during the feed rate rise period Tfu and reaches the forward transmission peak value Ws at a point later than the end of the peak rise period Tu at time t2. The feed rate rise period Tfu is set to be less than or equal to the peak rise period Tu. The forward transmission peak value Ws is greater than the average feed rate forward value Fa. The above peak rise period Tu is set by the peak rise period setting signal Tur in Figure 1. The base current Ib is set by the base current setting signal Ibr in Figure 1. The peak current Ip is set by the peak current setting signal Ipr in Figure 1. The reverse peak value Wr is set by the reverse peak value setting signal Wrr in Figure 1. The forward peak value Ws is set by the forward peak value setting signal Wsr (forward peak value modulation signal Wsc) in Figure 1. The first delay period Td1 is set by the first delay period setting signal Td1r in Figure 1. The feed rate rise period Tfu is set by the feed rate rise period setting signal Tfur in Figure 1.

[0052] During the predetermined peak period Tp from time t2 to t3, a current-modulated peak current Ip is supplied as shown in Figure (A), and a peak voltage Vp is applied between the welding wire and the base material as shown in Figure (B). The above peak period Tp is set to the reference peak period of the peak period setting signal Tpr in Figure 1.

[0053] During the predetermined peak fall period Tk between times t3 and t4, as shown in Figure (A), a peak fall current Ik is supplied, which decreases from a current-modulated peak current Ip to a current-modulated base current Ib. As shown in Figure (B), a peak fall voltage decreases from a peak voltage Vp to a base voltage Vb, which is applied between the welding wire and the base material. As shown in Figure (C), the feed rate Fw begins to change from the positive feed peak value Ws at a point after the second delay period Td2 from the start of the peak fall period Tk at time t3. It then changes during the feed rate fall period Tfk, reaching the average feed rate positive value Fa at a point after the end of the peak fall period Tk at time t4. The feed rate fall period Tfk is set to be less than or equal to the peak fall period Tk. The peak fall period Tk is set by the peak fall period setting signal Tkr in Figure 1. The second delay period Td2 is set by the second delay period setting signal Td2r in Figure 1. The feed rate fall time Tfk is set by the feed rate fall time setting signal Tfkr in Figure 1. The average feed rate positive value Fa is set by the average feed rate setting signal Far in Figure 1.

[0054] During the predetermined base period Tb from time t4 to t5, a current-modulated base current Ib is supplied as shown in Figure (A), and a base voltage Vb is applied between the welding wire and the base material as shown in Figure (B). As shown in Figure (C), the feed rate Fw is equal to the average feed rate positive value Fa. The base period Tb is set by the base period setting signal Tbr in Figure 1.

[0055] When a short circuit occurs between the welding wire and the base material at time t41 during the base period Tb, the welding voltage Vw rapidly decreases to a short-circuit voltage of a few volts, as shown in Figure (B), and the short-circuit detection signal Sd in Figure 1 becomes high. In response, the short-circuit occurrence signal So is set to high, as shown in Figure (D), and reset to low at the start of the base period of the next pulse cycle. As shown in Figure (A), the base current Ib decreases to a value determined by the short-circuit period base current setting signal Ibs (approximately 30-50A) in Figure 1. As shown in Figure (C), the feed rate Fw changes to the reverse feed peak value Wr when a short circuit occurs at time t41, and maintains that value until the start of the next cycle. At time t42, when the short circuit is released and the arc is regenerated, the welding voltage Vw rapidly increases to an arc voltage of several tens of volts, as shown in Figure (B), and the short-circuit detection signal Sd in Figure 1 becomes low. In response, as shown in Figure (A), the base current Ib increases to a value determined by the base current setting signal Ibr. On the other hand, as shown in Figure (C), the feed rate Fw maintains the reverse feed peak value Wr. Since the value of the base current Ib when the short circuit is released at time t42 is a small value determined by the short-circuit period base current setting signal Ibs, sputter generation associated with the release of the short circuit is very small.

[0056] Although not shown in the diagram, when the short-circuit period exceeds a predetermined long-term short-circuit discrimination value (approximately 5 ms), the long-term short-circuit discrimination signal Sld in Figure 1 goes to a high level. In response, the feed rate Fw is accelerated to a value determined by the long-term short-circuit reverse feed peak value setting signal Wlr in Figure 1. When the short-circuit period becomes a long-term short-circuit condition, the reverse feed peak value is accelerated to encourage the short-circuit to be released.

[0057] The first delay period Td1 and the second delay period Td2 described above become larger as the absolute value of the difference between the welding voltage setting signal Vr and the reference voltage setting signal Vsr (voltage fine-tuning signal Dvr) increases, for example, in the range of 0.1 to 0.5 ms. The base period Tb described above is set to a shorter period as the value of the welding voltage setting signal Vr increases, for example, in the range of 2 to 5 ms. Depending on the timing of the short circuit, the period of the average feed rate positive value Fa and the period of the reverse feed peak value Wr change. When the value of the welding voltage setting signal Vr changes, the first delay period Td1, the second delay period Td2, and the base period Tb change. Furthermore, if the short circuit period becomes a long-term short circuit, the reverse feed peak value is accelerated. Due to these factors, the average value of the feed rate Fw changes. When the average value of the feed rate Fw changes, the bead appearance, penetration depth, etc., fluctuate, and the welding quality deteriorates. To prevent this, in this embodiment, at least one of the forward feed peak value Ws and reverse feed peak value Wr is modulated so that the value of the average feed speed detection signal Fad in Figure 1 is equal to the value of the average feed speed setting signal Far in Figure 1. As a result, the average value of the feed speed Fw is always controlled to a predetermined value.

[0058] Figure 3 is a timing chart of each signal in the welding apparatus shown in Figure 1, illustrating a pulse arc welding control method according to an embodiment of the present invention. This figure shows the case where the value of the welding voltage setting signal Vr in Figure 1 is larger than the value of the reference voltage setting signal Vsr in Figure 1 to the extent that a short circuit occurs. Figure (A) shows the time variation of the welding current Iw, Figure (B) shows the time variation of the welding voltage Vw, Figure (C) shows the time variation of the welding wire feeding speed Fw, and Figure (D) shows the time variation of the short circuit generation signal So. The operation of each signal will be explained below with reference to this figure.

[0059] In this figure, because the value of the voltage fine-tuning signal Dvr in Figure 1 is set to a positive value, the value of the welding voltage setting signal Vr in Figure 1 is greater than the value of the reference voltage setting signal Vsr in Figure 1. When the value of the welding voltage setting signal Vr is equal to the value of the reference voltage setting signal Vsr, the arc length is controlled to an appropriate value. Depending on the joint shape of the base material, the arc length may be set longer than the appropriate value to improve welding quality. In such cases, the value of the welding voltage setting signal Vr is set to a value greater than the value of the reference voltage setting signal Vsr. In this figure, the value of the welding voltage setting signal Vr is such that a short circuit occurs during the base period, and is approximately 0 to 3V greater than the value of the reference voltage setting signal Vsr.

[0060] As shown in Figure (C), the feeding speed Fw is in a forward feeding state when it is a positive value above 0, where the feed is advanced towards the base material, and in a reverse feeding state when it is a negative value below 0, where the feed is advanced away from the base material.

[0061] During the predetermined peak rise period Tu from time t1 to t2, as shown in Figure (A), a peak rise current Iu is supplied, which rises from a current-modulated base current Ib to a current-modulated peak current Ip, and as shown in Figure (B), a peak rise voltage is applied between the welding wire and the base material, which rises from a base voltage Vb to a peak voltage Vp.

[0062] As shown in Figure (D), a short circuit occurred during the base period of the previous pulse cycle prior to time t1, so the short circuit signal So is at a high level. Therefore, the forward transmission peak value setting signal Wsr in Figure 1 is equal to the value of the forward transmission peak value modulation signal Wsc in Figure 1. As shown in Figure (C), the transmission speed Fw begins to change from the reverse transmission peak value Wr at a point one early period Ta1 before the start of the peak rise period Tu at time t1. It then changes during the transmission speed rise period Tfu and reaches the forward transmission peak value Ws before the end of the peak rise period Tu at time t2. The reason the forward transmission peak value Ws is reached before time t2 is that the transmission speed rise period Tfu is set to be less than or equal to the peak rise period Tu. The peak rise period Tu is set by the peak rise period setting signal Tur in Figure 1. The base current Ib is set by the base current setting signal Ibr in Figure 1. The peak current Ip is set by the peak current setting signal Ipr in Figure 1. The reverse transmission peak value Wr is set by the reverse transmission peak value setting signal Wrr in Figure 1. The forward transmission peak value Ws is set by the forward transmission peak value setting signal Wsr (forward transmission peak value modulation signal Wsc) in Figure 1. The first early period Ta1 is set by the first early period setting signal Ta1r in Figure 1. The feed rate rise period Tfu is set by the feed rate rise period setting signal Tfur in Figure 1.

[0063] During the predetermined peak period Tp from time t2 to t3, a current-modulated peak current Ip is supplied as shown in Figure (A), and a peak voltage Vp is applied between the welding wire and the base material as shown in Figure (B). The above peak period Tp is set to the reference peak period of the peak period setting signal Tpr in Figure 1.

[0064] During the predetermined peak fall period Tk from time t3 to t4, as shown in Figure (A), a peak fall current Ik is supplied, which decreases from a current-modulated peak current Ip to a current-modulated base current Ib, and as shown in Figure (B), a peak fall voltage decreases from a peak voltage Vp to a base voltage Vb, which is applied between the welding wire and the base material. As shown in Figure (C), the feed rate Fw begins to change from the positive feed peak value Ws at a point two periods earlier (Ta2) from the start of the peak fall period Tk at time t3. It then changes during the feed rate fall period Tfk and reaches the average feed rate positive value Fa before the end of the peak fall period Tk at time t4. The reason the average feed rate positive value Fa is reached before time t4 is that the feed rate fall period Tfk is set to be less than or equal to the peak fall period Tk. The above peak fall period Tk is set by the peak fall period setting signal Tkr in Figure 1. The second early period Ta2 described above is set by the second early period setting signal Ta2r in Figure 1. The feed rate fall period Tfk described above is set by the feed rate fall period setting signal Tfkr in Figure 1. The average feed rate positive value Fa described above is set by the average feed rate setting signal Far in Figure 1.

[0065] During the predetermined base period Tb from time t4 to t5, a current-modulated base current Ib is supplied as shown in Figure (A), and a base voltage Vb is applied between the welding wire and the base material as shown in Figure (B). As shown in Figure (C), the feed rate Fw is equal to the average feed rate positive value Fa. The base period Tb is set by the base period setting signal Tbr in Figure 1.

[0066] When a short circuit occurs between the welding wire and the base material at time t41, near the end of the base period Tb, the welding voltage Vw rapidly decreases to a short-circuit voltage of a few volts, as shown in Figure (B), and the short-circuit detection signal Sd in Figure 1 becomes high. In response to this, as shown in Figure (D), the short-circuit occurrence signal So is set to high and reset to low at the start of the base period of the next pulse cycle. As shown in Figure (A), the base current Ib decreases to a value determined by the short-circuit period base current setting signal Ibs in Figure 1. As shown in Figure (C), the feed rate Fw changes to the reverse feed peak value Wr. Furthermore, at time t42, when the short-circuit period exceeds a predetermined long-term short-circuit detection value (approximately 5 ms), the long-term short-circuit detection signal Sld in Figure 1 becomes high. In response to this, as shown in Figure (C), the feed rate Fw is accelerated to a value determined by the long-term short-circuit reverse feed peak value setting signal Wlr in Figure 1. When a short circuit period results in a long-term short circuit, the reverse peak value Wr is accelerated to prompt the short circuit to be released.

[0067] At time t5, the short-circuit period continues even after the period determined by the base period setting signal Tbr has ended, so the base period Tb is extended. At time t51, when the short circuit is released and the arc is re-generated, as shown in Figure (B), the welding voltage Vw rapidly increases to an arc voltage value of several tens of volts, and the short-circuit discrimination signal Sd and the long-term short-circuit discrimination signal Sld in Figure 1 become low levels. The value of the base current Ib when the short circuit is released is a small value determined by the short-circuit period base current setting signal Ibs, so the generation of spatter associated with the release of the short circuit is very small. When the arc is re-generated, as shown in Figure (A), the base current Ib increases to the value determined by the base current setting signal Ibr. As shown in Figure (C), the feed rate Fw begins to change from the reverse feed peak value Wr to the forward feed peak value Ws. At time t52, after the first early period Ta1 has elapsed from time t51, the system transitions to the peak rise period Tu. From here on, the above operation is repeated.

[0068] The first early period Ta1 and the second early period Ta2 described above become larger as the absolute value of the difference between the welding voltage setting signal Vr and the reference voltage setting signal Vsr (voltage fine adjustment signal Dvr) increases, for example, in the range of 0.2 to 1.0 ms. The base period Tb described above is set to a shorter period as the value of the welding voltage setting signal Vr increases, for example, in the range of 2 to 5 ms. Depending on the timing of the short circuit, the period of the average feed rate positive value Fa and the period of the reverse feed peak value Wr change. When the value of the welding voltage setting signal Vr changes, the first early period Ta1, the second early period Ta2, and the base period Tb change. Furthermore, if the short circuit period becomes a long-term short circuit, the reverse feed peak value is accelerated, and if the short circuit period continues at the end of the base period Tb, the base period Tb is extended. Due to these factors, the average value of the feed rate Fw changes. When the average value of the feed rate Fw changes, the bead appearance, penetration depth, etc., fluctuate, and the welding quality deteriorates. To prevent this, in this embodiment, at least one of the forward feed peak value Ws and reverse feed peak value Wr is modulated so that the value of the average feed speed detection signal Fad in Figure 1 is equal to the value of the average feed speed setting signal Far in Figure 1. As a result, the average value of the feed speed Fw is always controlled to a predetermined value.

[0069] Figure 4 is a timing chart of each signal in the welding apparatus shown in Figure 1, illustrating a pulse arc welding control method according to an embodiment of the present invention. This figure shows the case where the value of the welding voltage setting signal Vr in Figure 1 is larger than the value of the reference voltage setting signal Vsr in Figure 1 to the extent that a short circuit does not occur. Figure (A) shows the time variation of the welding current Iw, Figure (B) shows the time variation of the welding voltage Vw, Figure (C) shows the time variation of the welding wire feeding speed Fw, and Figure (D) shows the time variation of the short circuit occurrence signal So. The operation of each signal will be explained below with reference to this figure.

[0070] In this figure, because the value of the voltage fine-tuning signal Dvr in Figure 1 is set to a positive value, the value of the welding voltage setting signal Vr in Figure 1 is greater than the value of the reference voltage setting signal Vsr in Figure 1. When the value of the welding voltage setting signal Vr is equal to the value of the reference voltage setting signal Vsr, the arc length is controlled to an appropriate value. Depending on the joint shape of the base material, the arc length may be set longer than the appropriate value to improve welding quality. In such cases, the value of the welding voltage setting signal Vr is set to a value greater than the value of the reference voltage setting signal Vsr. In this figure, the value of the welding voltage setting signal Vr is a value that does not cause a short circuit during the base period, and is about 3V or more greater than the value of the reference voltage setting signal Vsr.

[0071] In this figure, the explanation of the same operation as in Figure 3 will not be repeated. The following explanation will describe an operation that is different from that in Figure 3.

[0072] As shown in Figure (D), since no short circuit occurred during the base period of the previous pulse cycle before time t1, the short circuit occurrence signal So is at a low level throughout the entire period. Therefore, the positive feed peak value setting signal Wsr in Figure 1 is equal to the value of the average feed rate setting signal Far in Figure 1. Consequently, as shown in Figure (C), the feed rate Fw is a constant value of the average feed rate positive value Fa throughout the entire period of the peak period Tp and the base period Tb. Under welding conditions where no short circuit occurs during the base period, the welding state can be stabilized by setting the feed rate Fw to a constant value of the average feed rate positive value Fa.

[0073] As shown in Figure (D), since the short-circuit generation signal So is at a low level, the peak period setting signal Tpr in Figure 1 becomes an increasing peak period, and is a larger value than the reference peak period in Figures 2 and 3. This makes the integral value of the peak current Ip during the peak period Tp larger than in Figures 2 and 3. Since the feed rate Fw is a constant value of the average feed rate positive feed value Fa, increasing the integral value of the peak current Ip stabilizes the droplet transfer state and improves the welding condition. Furthermore, when the output control is pulse period modulation control, the integral value of the peak current Ip can be increased by increasing the peak current Ip and the peak period Tp.

[0074] During the predetermined base period Tb from time t4 to t5, a current-modulated base current Ib is supplied as shown in Figure (A), and a base voltage Vb is applied between the welding wire and the base material as shown in Figure (B). No short circuit occurs during the base period Tb.

[0075] Numerical examples for each of the above parameters are shown below: Tu=1ms, Tp (reference peak period)=1ms, Tp (increasing peak period)=1.5ms, Tk=1ms, Ip=350~450A, Ib=50~150A, Ws=50m / min, Fa=7m / min, Wr=-30m / min, Tfu=0.8ms, Tfk=0.8ms

[0076] The effects of this embodiment will be described below. According to this embodiment, in a pulse arc welding control method in which welding is performed by feeding the welding wire in forward and reverse directions, supplying a peak rise current that rises from the base current value to the peak current value during the peak rise period, supplying the peak current during the peak period, supplying a peak fall current that decreases from the peak current value to the base current value during the peak fall period, supplying the base current during the base period, and repeating the supply of these welding currents as one pulse period, and controlling the arc length based on the welding voltage set value, an average feeding speed set value for the welding wire is set, the feeding speed is set to a forward feeding peak value that is greater than the average feeding speed set value during the peak period, to the average feeding speed set value during the base period, to the reverse feeding peak value if a short circuit occurs during the base period, to maintain the reverse feeding peak value even after the short circuit is released, and if no short circuit occurs during the base period, the forward feeding peak value of the next pulse period is set to the average feeding speed set value. In this embodiment, during the peak period, a peak current above the critical current value is applied, and the feed rate is set to the forward feed peak value to form droplets of appropriate size. During the subsequent base period, a base current below the critical current value is applied, and the feed rate is set to the average feed rate forward value to cause a short circuit between the droplets and the molten pool. When a short circuit occurs, the base current is applied and the feed rate is set to the reverse feed peak value to quickly resolve the short circuit. Even after the short circuit is resolved, the base current is applied and the feed rate is maintained at the reverse feed peak value to lengthen the arc and prevent re-short circuits. In this embodiment, since the feed rate is set to the reverse feed peak value during a short circuit, even if the current value during the short circuit is small, the short circuit can be reliably resolved early with minimal spatter generation. As a result, in this embodiment, by repeating the above process, stable pulsed arc welding with periodic short circuits can be performed. Furthermore, in this embodiment, under welding conditions where no short circuit occurs during the base period, the feed rate is kept constant at the average feed rate forward value for the entire duration of both the peak and base periods. This improves the welding condition.

[0077] More preferably, according to this embodiment, if no short circuit occurs during the base period, the integral value of the peak current in the next pulse period is increased. When no short circuit occurs during the base period, the feed rate is constant to the average feed rate plus value. In this case, by increasing the integral value of the peak current, the droplet transfer state can be stabilized and the welding state can be improved.

[0078] More preferably, according to this embodiment, the start of the peak rise period is delayed until the short circuit is cleared. In rare cases, a short circuit that occurred during the base period may persist until the end of the base period, and the short circuit may be cleared during the peak rise period or peak period of the next cycle, causing the arc to regenerate. In such cases, the arc will regenerate with a large welding current value, resulting in a large amount of spatter. In this embodiment, the start of the peak rise period of the next cycle is delayed until the short circuit that occurred during the base period is cleared. As a result, even if the short circuit is not cleared at the end of the base period, spatter generation can be reduced, and welding quality can be improved.

[0079] More preferably, according to this embodiment, when the welding voltage setting is equal to the reference voltage setting, the base period is set to the reference base period; when the welding voltage setting is less than the reference voltage setting, the base period is made longer than the reference base period; and when the welding voltage setting is greater than the reference voltage setting, the base period is made shorter than the reference base period. When the welding voltage setting is less than the reference voltage setting, the arc length is short, which can cause short circuits to continue into the next cycle, making the welding state unstable. For this reason, in this embodiment, the base period is made longer to suppress the continuation of short circuits into the next cycle. When the welding voltage setting is greater than the reference voltage setting, a longer base period can cause magnetic blow, making the welding state unstable. For this reason, in this embodiment, the base period is made shorter to suppress the occurrence of magnetic blow.

[0080] More preferably, according to this embodiment, at least one of the forward feed peak value and the reverse feed peak value is modulated so that the average feed rate is equal to the average feed rate set value. In this embodiment, the period during which the feed rate is equal to the average feed rate forward value and the period during which it is equal to the reverse feed peak value changes depending on the timing of short circuits occurring during the base period, so the average feed rate changes. When the average feed rate changes, the bead appearance, penetration depth, etc., fluctuate, and the welding quality deteriorates. In this embodiment, at least one of the forward feed peak value and the reverse feed peak value is modulated so that the average feed rate is equal to a predetermined value, so that the welding quality can always be kept good.

[0081] Furthermore, according to this embodiment, the pulse arc welding power supply sets an average feed rate setting value for the welding wire, sets the feed rate to a positive feed peak value greater than the average feed rate setting value during the peak period, sets it to the average feed rate setting value during the base period, sets it to a negative feed peak value if a short circuit occurs during the base period, maintains the negative feed peak value even after the short circuit is cleared, and sets the positive feed peak value of the next pulse period to the average feed rate setting value if no short circuit occurs during the base period. The pulse arc welding power supply according to this embodiment provides the above-mentioned effects.

[0082] More preferably, according to this embodiment, the base current value is smaller during the short-circuit period than during the arc generation period. By making the base current value smaller during the short-circuit period than during the arc generation period, the current value when the arc re-starts is smaller, which can further reduce sputter generation.

[0083] More preferably, according to this embodiment, the reverse feed peak value is advanced when the short-circuit period exceeds a reference value. When a long-term short circuit occurs, where the short-circuit period exceeds a reference value, the welding state becomes unstable. In this embodiment, when a long-term short-circuit condition occurs, the reverse feed peak value is advanced to release the short circuit early. As a result, this embodiment can suppress the instability of the welding state caused by the occurrence of a long-term short circuit.

[0084] More preferably, according to this embodiment, when the welding voltage setting is smaller than the reference voltage setting, the welding wire feed speed starts changing from the reverse feed peak value to the forward feed peak value at a point one delay period after the start of the peak rise period, and starts changing from the forward feed peak value to the base period forward feed value at a point one delay period after the start of the peak fall period. When the welding voltage setting is smaller than the reference voltage setting, the arc length is short, which may cause a short circuit during the peak period or peak fall period. In such cases, a short circuit occurs when the welding current is high, resulting in a lot of spatter and poor welding quality. In this embodiment, the feed speed starts changing from the reverse feed peak value to the forward feed peak value at a point one delay period after the start of the peak rise period, and starts changing from the forward feed peak value to the base period forward feed value at a point one delay period after the start of the peak fall period. By providing the first and second delay periods in this way, the timing of droplet migration can be delayed, so that the occurrence of a short circuit associated with droplet migration can be guided to the base period. If a short circuit occurs during the base period, the welding current value is low, which can suppress spatter generation and improve welding quality.

[0085] More preferably, according to this embodiment, when the welding voltage setting is greater than the reference voltage setting, the welding wire feed speed starts changing from the reverse feed peak value to the forward feed peak value at a point one early period before the start of the peak rise period, and starts changing from the forward feed peak value to the base period forward feed value at a point one early period before the start of the peak fall period. When the welding voltage setting is greater than the reference voltage setting, the arc length is long, which may cause a short circuit to occur near the end of the base period. In such cases, the short circuit continues until the peak period of the next cycle, and the short circuit is released with a large welding current value, resulting in a lot of spatter and poor welding quality. In this embodiment, the feed speed starts changing from the reverse feed peak value to the forward feed peak value at a point one early period before the start of the peak rise period, and starts changing from the forward feed peak value to the base period forward feed value at a point one early period before the start of the peak fall period. By establishing a first early period and a second early period in this way, droplet migration can be accelerated, thereby guiding the occurrence of short circuits associated with droplet migration to the early stages of the base period. If a short circuit occurs early in the base period, it will be resolved during the base period, thus suppressing spatter generation and improving welding quality.

[0086] More preferably, according to this embodiment, the first delay period, the second delay period, the first early period, and the second early period are set to larger values ​​as the absolute value of the difference between the welding voltage set value and the reference voltage set value increases. In this way, regardless of the magnitude of the welding voltage set value, a short circuit can be made to occur in the early period of the base period. As a result, even if the arc length is set to a short or long state by the welding voltage set value, the generation of spatter can be suppressed. [Explanation of symbols]

[0087] 1: Welding wire, 2: Base material, 3: Arc, 4: Welding torch, 5: Feed roll, DV: Drive circuit, Dv: Drive signal, DVR: Voltage fine adjustment circuit, Dvr: Voltage fine adjustment signal, EI: Current error amplification circuit, Ei: Current error amplification signal, EV: Voltage error amplification circuit, Ev: Voltage error amplification signal, Fa: Average feed speed positive feed value, FAD: Average feed speed detection circuit, Fad: Average feed speed detection signal, FAR: Average feed speed setting circuit, Far: Average feed speed setting signal, FC: Feed control circuit, Fc: Feed control signal, FR: Feed speed setting circuit, Fr: Feed speed setting signal, Fw: Feed speed IAR: Welding current average value setting circuit, Iar: Welding current average value setting signal, Ib: Base current, Ibr: Base current setting signal, IBS: Short-circuit period base current setting circuit, Ibs: Short-circuit period base current setting signal, IC: Current modulation circuit, ID: Welding current detection circuit, Id: Welding current detection signal, Ik: Peak falling current, Ip: Peak current, Ipr: Peak current setting signal, IR: Welding current setting circuit, Ir: Welding current setting signal, Iu: Peak rising current, Iw: Welding current, MC: Power control circuit, On: Start signal, PS: Welding power supply, RC: Robot control device, SD: Short circuit Discrimination circuit, Sd: Short circuit discrimination signal, SLD: Long-term short circuit discrimination circuit, Sld: Long-term short circuit discrimination signal, SO: Short circuit generation circuit, So: Short circuit generation signal, Ta1: First early period, TA1R: First early period setting circuit, Ta1r: First early period setting signal, Ta2: Second early period, TA2R: Second early period setting circuit, Ta2r: Second early period setting signal, Tb: Base period, TBR: Base period setting circuit, Tbr: Base period setting signal, Td1: First delay period, TD1R: First delay period setting circuit, Td1r: First delay period setting signal, Td2: Second delay period, TD2R: Second delay Period setting circuit, Td2r: Second delay period setting signal, Tfk: Feed speed falling period, TFKR: Feed speed falling period setting circuit, Tfkr: Feed speed falling period setting signal, Tfu: Feed speed rising period, TFUR: Feed speed rising period setting circuit, Tfur: Feed speed rising period setting signal, Tk: Peak falling period, TKR: Peak falling period setting circuit, Tkr: Peak falling period setting signal, Tm: Timer signal, Tp: Peak period, TPR: Peak period setting circuit, Tpr: Peak period setting signal, Tu: Peak rising period, TUR: Peak rising period setting circuit,Tur: Peak rise time setting signal, VAV: Welding voltage averaging circuit, Vav: Welding voltage average value signal, Vb: Base voltage, VD: Welding voltage detection circuit, Vd: Welding voltage detection signal, Vp: Peak voltage, VR: Welding voltage setting circuit, Vr: Welding voltage setting signal, VSR: Reference voltage setting circuit, Vsr: Reference voltage setting signal, Vw: Welding voltage, WC: Feed speed modulation circuit, WL: Reactor, WLR: Long-term short-circuit reverse peak value setting circuit, Wlr: Long-term short-circuit reverse peak value setting signal, WM: Feed motor, Wr: Reverse peak value, Wrr: Reverse peak value setting signal, Ws: Forward peak value, Wsc: Forward peak value modulation signal, WSR: Forward peak value setting circuit, Wsr: Forward peak value setting signal,

Claims

1. In a pulsed arc welding control method in which welding is performed by feeding the welding wire in forward and reverse directions, applying a peak rise current that rises from the base current value to the peak current value during the peak rise period, applying the said peak current during the peak period, applying a peak fall current that decreases from the said peak current value to the said base current value during the peak fall period, applying the said base current during the base period, repeating the application of these welding currents as one pulse period, and controlling the arc length based on the welding voltage set value, The average feed rate setting value for welding wire is set, and the feed rate is set to a forward feed peak value greater than the average feed rate setting value during the peak period, set to the average feed rate setting value during the base period, set to a reverse feed peak value if a short circuit occurs during the base period, and maintains the reverse feed peak value even after the short circuit is cleared. If the short circuit does not occur during the base period, the forward transmission peak value of the next pulse period is set to the average transmission speed setting value. A pulsed arc welding control method characterized by the following:

2. If the short circuit does not occur during the base period, the integral value of the peak current in the next pulse period will be increased. The pulse arc welding control method according to feature 1.

3. The start of the peak rise period is delayed until the short circuit is released. The pulse arc welding control method according to claim 1 or 2, characterized by the above.

4. When the welding voltage setting value is equal to the reference voltage setting value, the base period is set to the reference base period; when the welding voltage setting value is less than the reference voltage setting value, the base period is made longer than the reference base period; and when the welding voltage setting value is greater than the reference voltage setting value, the base period is made shorter than the reference base period. The pulse arc welding control method according to claim 1 or 2, characterized by the above.

5. The forward transmission peak value and the reverse transmission peak value are modulated and controlled so that the average value of the transmission speed is equal to the average transmission speed set value. The pulse arc welding control method according to claim 1 or 2, characterized by the above.

6. In a pulsed arc welding power supply that feeds the welding wire in forward and reverse directions, supplies a peak rise current that increases from the base current value to the peak current value during the peak rise period, supplies the peak current during the peak period, supplies a peak fall current that decreases from the peak current value to the base current value during the peak fall period, supplies the base current during the base period, repeats the supply of these welding currents as one pulse period, and performs arc length control based on the welding voltage set value for welding, The average feed rate setting value for welding wire is set, and the feed rate is set to a forward feed peak value greater than the average feed rate setting value during the peak period, set to the average feed rate setting value during the base period, set to a reverse feed peak value if a short circuit occurs during the base period, and maintains the reverse feed peak value even after the short circuit is cleared. If the short circuit does not occur during the base period, the forward transmission peak value of the next pulse period is set to the average transmission speed setting value. A pulsed arc welding power supply characterized by the following features.

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