AC pulsed arc welding control method and AC pulsed arc welding power supply

Abstract

In consumable electrode AC 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 an AC pulsed 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 with positive electrode polarity, and during the electrode negative polarity period, with the welding wire feeding speed Fw is set to the positive feed peak value during the peak period at time t2 to t3, to a base period positive feed value smaller than the positive feed peak value during the base period at time t4 to t41 so that a short circuit occurs during the base period, to the reverse feed peak value when a short circuit occurs at time t41, to maintain the reverse feed peak value even if the short circuit is released at time t42, and to the electrode negative polarity feeding speed during the electrode negative polarity period at time t5 to t6.

Description

Technical Field

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

Background Art

[0002] Alternating current pulse arc welding for feeding and welding a welding wire is used for welding steel, aluminum, etc. In this alternating current pulse arc welding, a welding wire is fed. During the electrode positive polarity period, during the peak rising period, 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 period, the peak current is energized. During the peak falling 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 base period, the base current is energized. During the electrode negative polarity period, an electrode negative polarity current is energized. The energization of these welding currents is repeated as one pulse cycle to perform welding.

[0003] In order to increase the welding speed for the purpose of improving the efficiency of welding, it is necessary to increase the melting speed of the welding wire. In alternating current pulse arc welding, by providing an electrode negative polarity period, the melting speed is increased by about 1.5 times compared to direct current pulse arc welding, so the welding operation can be made more efficient.

[0004] In the invention of Patent Document 1, during a predetermined period from a first point in time during the peak period to a second point in time during the base period, the feeding speed of the welding wire is made lower than the feeding speed at the rising time 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

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In AC 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 suppress the increase in spatter generation even when a short circuit occurs between the welding wire and the base metal, thereby achieving good welding quality. [Means for solving the problem]

[0007] The AC pulsed arc welding control method provided by the first aspect of the present invention involves feeding the welding wire in forward and reverse directions, and during the positive electrode polarity period, a peak rise current is supplied that rises from the base current value to the peak current value during the peak rise period, the peak current is supplied during the peak period, a peak fall current is supplied that falls from the peak current value to the base current value during the peak fall period, the base current is supplied during the base period, and a negative electrode polarity current is supplied during the negative electrode polarity period, with these welding currents supplied in one pulse period. In an AC pulsed arc welding control method that repeatedly performs arc length control based on a welding voltage set value to perform welding, the welding wire feeding speed is set to the forward feeding peak value during the peak period, to a base period forward feeding value smaller than the forward feeding peak value during the base period so that a short circuit occurs during the base period, to the reverse feeding peak value when the short circuit occurs, to maintain the reverse feeding peak value even after the short circuit is released, and to the electrode negative polarity period feeding speed of reverse feeding, feeding stopped, or forward feeding.

[0008] In a preferred embodiment of the present invention, the short-circuit occurrence time from the start of the base period until the short circuit occurs is detected, and the base period forward value is modulated and controlled so that the short-circuit occurrence time becomes equal to the short-circuit occurrence time set value.

[0009] In a preferred embodiment of the present invention, the electrode negative polarity period supply rate is set according to the duration of the electrode negative polarity period.

[0010] In a preferred embodiment of the present invention, the start of the negative electrode polarity period is delayed until the short circuit is released.

[0011] In a preferred embodiment of the present invention, the forward feed peak value and / or the reverse feed peak value are modulated and controlled so that the average value of the feed speed is a predetermined value.

[0012] In a preferred embodiment of the present invention, the electrode negative polarity current is modulated and controlled so that the electrode negative polarity current ratio is a predetermined value.

[0013] An AC pulsed arc welding power supply provided by a second aspect of the present invention feeds a welding wire in both forward and reverse directions, and in the electrode positive polarity period, during the peak rise period, a peak rise current is supplied that rises from the base current value to the peak current value, during the peak period the peak current is supplied, during the peak fall period a peak fall current is supplied that falls from the peak current value to the base current value, during the base period the base current is supplied, and during the electrode negative polarity period an electrode negative polarity current is supplied, and these supply of welding currents is repeated as one pulse period, and the arc length is controlled based on the welding voltage set value for welding, wherein the feeding speed of the welding wire is set to the forward feed peak value during the peak period, during the base period a base period forward feed value that is smaller than the forward feed peak value so that a short circuit occurs during the base period, when the short circuit occurs the base period the base period forward feed value is set to the reverse feed peak value, and even if the short circuit is released the reverse feed peak value is maintained, and during the electrode negative polarity period the feeding speed is set to reverse feed, feed stop, or forward feed. [Effects of the Invention]

[0014] 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]

[0015] [Figure 1]This is a block diagram of a welding apparatus for implementing an AC 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 an AC pulsed 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 an AC pulsed 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 greater than the value of the reference voltage setting signal Vsr. [Modes for carrying out the invention]

[0016] Embodiments of the present invention will be described below with reference to the drawings.

[0017] Figure 1 is a block diagram of a welding apparatus for implementing an AC pulsed arc welding control method according to an embodiment of the present invention. The welding apparatus mainly consists of an AC pulsed 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.

[0018] The AC pulsed arc welding power supply PS consists of the following blocks:

[0019] The power control circuit MC is connected to an AC commercial power supply such as three-phase 200V (not shown), and takes as inputs the drive signal Dv and the polarity switching signal Spn described later. It performs output control such as inverter control according to the drive signal Dv, and switches between the electrode positive polarity EP and the electrode negative polarity EN according to the polarity switching signal Spn, and outputs an AC welding voltage Vw and a welding current Iw suitable for welding. Although not shown, this power control circuit MC includes a primary rectification circuit that rectifies the AC commercial power supply, a capacitor that smooths the rectified DC, a primary side inverter circuit that converts the smoothed DC into high-frequency AC according to the drive signal Dv, an inverter transformer that steps down the high-frequency AC to a voltage value suitable for welding, a secondary rectification circuit that rectifies the stepped-down high-frequency AC, a reactor that smooths the rectified DC, and a secondary side inverter circuit that switches the smoothed DC between the electrode positive polarity EP and the electrode negative polarity EN according to the polarity switching signal Spn.

[0020] The feeding motor WM is rotationally driven by a feeding control signal Fc described later. The welding wire 1 is fed forward and backward at a feeding speed Fw through the welding torch 4 by the rotation of the feeding roll 5 coupled to the feeding motor WM described above, and an arc 3 is generated between the base material 2. The feeding motor WM and the welding torch 4 are mounted on a robot. A welding voltage Vw is applied between the power supply tip (not shown) in the welding torch 4 and the base material 2, and a welding current Iw is energized.

[0021] The welding current average value setting circuit IAR outputs a predetermined welding current average value setting signal Iar. The feeding speed average value setting circuit FAR outputs a feeding speed average value setting signal Far corresponding to the welding current average value setting signal Iar described above. 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 described above.

[0022] The voltage fine-tuning circuit DVR outputs a predetermined voltage fine-tuning signal Dvr. The value of the voltage fine-tuning signal Dvr is a real number in the range of, for example, -5V to +5V. The welding voltage setting circuit VR takes the above reference voltage setting signal Vsr and the above voltage fine-tuning signal Dvr as inputs, 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 with the value of the voltage fine-tuning signal Dvr.

[0023] The welding voltage detection circuit VD detects the above AC welding voltage Vw, converts it to an absolute value, and outputs a welding voltage detection signal Vd. The welding voltage averaging circuit VAV averages this welding voltage detection signal Vd (passes it through a low-pass filter) and outputs a welding voltage average value signal Vav. The voltage error amplification circuit EV amplifies the error between the above welding voltage setting signal Vr(+) and the above welding voltage average value signal Vav(-) and outputs a voltage error amplification signal Ev.

[0024] The current modulation circuit IC takes the above voltage error amplification signal Ev as an input, performs PI (proportional-integral) control or PID (proportional-integral-derivative) control, and outputs a peak current setting signal Ipr and a base current setting signal Ibr. The peak current setting signal Ipr and the base current setting signal Ibr are current-modulated and controlled by this circuit 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 so that the arc length is maintained at an appropriate value. It is also possible to perform current modulation control only on the peak current setting signal Ipr and set the base current setting signal Ibr to a predetermined value.

[0025] The short-circuit discrimination circuit SD takes the above welding voltage detection signal Vd as an input. When this value is less than the short-circuit discrimination value (about 10V), it discriminates that it is a short-circuit period and becomes High level. When it is greater than or equal to the short-circuit discrimination value, it discriminates that it is in the arc generation period and outputs a short-circuit discrimination signal Sd that becomes Low level.

[0026] 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.

[0027] The peak rise period setting circuit TUR outputs a predetermined peak rise period setting signal Tur. The peak period setting circuit TPR outputs a predetermined peak period setting signal Tpr. The peak fall period setting circuit TKR outputs a predetermined peak fall period setting signal Tkr.

[0028] 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.

[0029] The electrode negative polarity period setting circuit TNR outputs a predetermined electrode negative polarity period setting signal Tnr.

[0030] The welding current setting circuit IR takes the following inputs: the electrode negative polarity period setting signal Tnr, the electrode negative polarity current control setting signal Incr (described later), the short-circuit detection signal Sd, the short-circuit period 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 performs the following processing to output 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) Next, 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, and 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, if the short-circuit detection signal Sd is at a high level (short-circuit period) when the base period Tb ends, the base period Tb will be extended until it changes to a low level (arc generation period) and 0.2 ms has elapsed. 5) Next, during the electrode negative polarity period Ten, which is determined by the electrode negative polarity period setting signal Tnr, a timer signal Tm=5 is output, the electrode negative polarity current control setting signal Incr is output as the welding current setting signal Ir, and immediately before the end of the electrode negative polarity period Ten, a welding current setting signal Ir is output that rises to the value of the base current setting signal Ibr. 6) Repeat steps 1) to 5) above.

[0031] The polarity switching circuit SPN takes the above timer signal Tm as input and outputs a polarity switching signal Spn that is high level when the timer signal Tm = 1 to 4 (electrode positive polarity period Tep) and low level when the timer signal Tm = 5 (electrode negative polarity period Ten).

[0032] The feed speed modulation circuit WC takes the feed speed average value setting signal Far and the feed speed average value 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 setting signal Wsr and the reverse peak value setting signal Wrr. This circuit modulates the feed speed average value detection signal Fad so that its value is equal to the feed speed average value setting signal Far. Alternatively, only the forward peak value setting signal Wsr or the reverse peak value setting signal Wrr may be modulated. In this case, the parameter that is not modulated is set to a predetermined value.

[0033] The short-circuit occurrence time detection circuit TSD takes the above-mentioned timer signal Tm and short-circuit discrimination signal Sd as inputs, detects the short-circuit occurrence time from the moment the timer signal Tm changes to 4 (base period) until the short-circuit discrimination signal Sd changes to a high level (short-circuit period), and outputs a short-circuit occurrence time detection signal Tsd. Alternatively, the moving average value of the short-circuit occurrence time may be calculated and used as the short-circuit occurrence time detection signal Tsd.

[0034] The short-circuit occurrence time setting circuit TSR outputs a short-circuit occurrence time setting signal Tsr for setting a specific point in time during the base period. Here, the short-circuit occurrence time setting signal Tsr may also be a signal with a setting range that has an upper limit and a lower limit.

[0035] The base period positive transmission value setting circuit WBR takes the short-circuit occurrence time detection signal Tsd and the short-circuit occurrence time setting signal Tsr as inputs, performs one of the following processes 1) to 3), and outputs the base period positive transmission value setting signal Wbr. This circuit sets the base period positive transmission value setting signal Wbr within a range smaller than the value of the positive transmission peak value setting signal Wsr, so that a short circuit occurs at a specific point in time during the base period. 1) The base period positive transmission value setting signal Wbr is set in advance through experimentation so that a short circuit occurs at a specific point in time during the base period. 2) The value of the base period forward transmission value setting signal Wbr is modulated and controlled so that the value of the short-circuit occurrence time detection signal Tsd is equal to the value of the short-circuit occurrence time setting signal Tsr. 3) When the short-circuit occurrence time setting signal Tsr is within the set range, the value of the base period forward transmission value setting signal Wbr is modulated and controlled so that the value of the short-circuit occurrence time detection signal Tsd is within the set range between the upper and lower limits of the short-circuit occurrence time setting signal Tsr.

[0036] The electrode negative polarity period feed rate setting circuit WNR outputs an electrode negative polarity period feed rate setting signal Wnr that changes from a negative value to a positive value according to a predetermined function that takes the electrode negative polarity period setting signal Tnr as input. The function causes the value of the electrode negative polarity period feed rate setting signal Wnr to change from a negative value (reverse feed), 0 (feed stop) to a positive value (forward feed) as the value of the electrode negative polarity period setting signal Tnr increases.

[0037] The welding current detection circuit ID detects the AC welding current Iw mentioned above, converts it to an absolute value, and outputs a welding current detection signal Id. The current error amplification circuit EI amplifies the error between the welding current setting signal Ir(+) and the welding current detection signal Id(-) mentioned above 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 mentioned above by performing pulse width modulation control etc. based on the current error amplification signal Ei when the start signal On is at a high level (welding start). When the start signal On is at a low level (welding stop), it does not output a drive signal Dv.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] The feed speed setting circuit FR takes the following signals as input: the electrode negative polarity period feed speed setting signal Wnr, the short circuit detection signal Sd, the long-term short circuit detection signal Sld, the long-term short-circuit reverse peak value setting signal Wlr, the voltage fine adjustment signal Dvr, the forward peak value setting signal Wsr, the base period forward value setting signal Wbr, the reverse peak value setting signal Wrr, the timer signal Tm, the feed speed rise period setting signal Tfur, the feed speed fall period setting signal Tfkr, the first delay period setting signal Td1r, the second delay period setting signal Td2r, the first early period setting signal Ta1r, and the second early period setting signal Ta2r, performs the following processing, and outputs the feed speed setting signal Fr. (1) When the voltage fine adjustment signal Dvr ≤ 0 1) The feed rate setting signal Fr starts changing from the value of the electrode negative polarity period feed rate setting signal Wnr 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 positive feed peak value setting signal Wsr during the period determined by the feed rate 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 base period positive feed value setting signal Wbr 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) during the timer signal Tm=4 (base period), 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. 4) The feed rate setting signal Fr will be the value of the feed rate setting signal Wnr during the negative electrode polarity period while the timer signal Tm=5 (negative electrode polarity period Ten) is active. 5) Repeat steps 1) to 4) above. (2) When the voltage fine adjustment signal Dvr > 0 1) The feed rate setting signal Fr starts changing from the value of the electrode negative polarity period feed rate setting signal Wnr when the timer signal Tm=5 (electrode negative polarity period) has elapsed for a period of (Tnr-Ta1r), and changes to the value of the positive feed peak value setting signal Wsr during the period determined by the feed rate rise time setting signal Tfur, and maintains that value. 2) The feed speed 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 base period positive feed value setting signal Wbr during the period determined by the feed speed 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 peak value setting signal Wrr when the short-circuit detection signal Sd changes to a high level (short circuit) during the timer signal Tm=4 (base period), 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 peak value setting signal Wrr to the long-term short-circuit reverse peak value setting signal Wlr. 4) The feed rate setting signal Fr will be the value of the feed rate setting signal Wnr during the negative electrode polarity period while the timer signal Tm=5 (negative electrode polarity period Ten) is active. 5) Repeat steps 1) to 4) above.

[0047] The feed speed average value detection circuit FAD takes the feed speed setting signal Fr as input, calculates the average value, and outputs the feed speed average value detection signal Fad. Alternatively, the feed speed Fw may be detected directly and the average value calculated instead of the feed speed setting signal Fr.

[0048] 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.

[0049] The electrode negative current ratio calculation circuit RND takes the above-mentioned welding current detection signal Id and timer signal Tm as inputs, calculates the percentage of the value obtained by integrating the welding current detection signal Id over the electrode negative polarity period Ten of timer signal Tm=5 relative to the value obtained by integrating the welding current detection signal Id over the pulse period Tf of timer signal Tm=1 to 5, and outputs this as the electrode negative polarity current ratio calculation signal Rnd. Therefore, the electrode negative polarity current ratio Rn[%] is the percentage of the electrode negative polarity current Ien relative to the average value of the welding current Iw.

[0050] The electrode negative polarity current ratio setting circuit RNR outputs a predetermined electrode negative polarity current ratio setting signal Rnr.

[0051] The electrode negative polarity current setting circuit INR takes the electrode negative polarity current ratio calculation signal Rnd and the electrode negative polarity current ratio setting signal Rnr as inputs, modulates them based on the error amplification values ​​of both values, and outputs the electrode negative polarity current setting signal Inr. This circuit modulates the value of the electrode negative polarity current setting signal Inr so that the value of the electrode negative polarity current ratio calculation signal Rnd becomes equal to the value of the electrode negative polarity current ratio setting signal Rnr.

[0052] The electrode negative polarity current control setting circuit INCR takes the above-mentioned electrode negative polarity current setting signal Inr as input and outputs an electrode negative polarity current control setting signal Incr, which is a pulse waveform with one or more periods and uses this value as the average.

[0053] 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.

[0054] Figure 2 is a timing chart of each signal in the welding apparatus shown in Figure 1, illustrating an AC pulsed 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 polarity switching signal Spn. The operation of each signal will be explained below with reference to this figure.

[0055] 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.

[0056] The welding current Iw shown in Figure (A) and the welding voltage Vw shown in Figure (B) are positive values ​​above 0 when the electrode is positive polarity EP, and negative values ​​below 0 when the electrode is negative polarity EN. The feed rate Fw shown in Figure (C) is a forward feed state where the material is fed forward towards the base material when the value above 0 is positive, and a reverse feed state where the material is fed backward away from the base material when the value below 0 is negative. The polarity switching signal Spn shown in Figure (D) is at a high level during the electrode positive polarity period Tep from time t1 to t5, and at a low level during the electrode negative polarity period Ten from time t5 to t6.

[0057] At time t1, as shown in Figure (D), the polarity switching signal Spn changes from a low level to a high level, resulting in a positive electrode polarity period Tep. In response to this, at time t1, as shown in Figure (A), the welding current Iw changes from a negative base current Ib to a positive base current Ib, and as shown in Figure (B), the welding voltage Vw changes from a negative arc voltage value to a positive arc voltage value. During the predetermined peak rise period Tu from time t1 to t2, as shown in Figure (A), a peak rise current Iu increases from a current-modulated base current Ib to a current-modulated peak current Ip, and as shown in Figure (B), a peak rise voltage increases from a base voltage Vb to a peak voltage Vp, which is applied between the welding wire and the base material.

[0058] As shown in Figure (C), the feed rate Fw begins to change from the electrode negative polarity period feed rate Wn at a point one delay 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 positive feed peak value Ws at a point after 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 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 positive feed peak value Ws is set by the positive feed peak value setting signal Wsr 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 time Tfu mentioned above is set by the feed rate rise time setting signal Tfur shown in Figure 1.

[0059] 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 by the peak period setting signal Tpr in Figure 1.

[0060] 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 base period positive feed value Wb 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 base period positive feed value Wb is set to be less than the positive feed peak value Ws. The above 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.

[0061] 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). The base period Tb is set by the base period setting signal Tbr shown in Figure 1.

[0062] 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. The short-circuit occurrence time detection circuit TSD in Figure 1 outputs a short-circuit occurrence time detection signal Tsd for times t4 to t41. Then, the base period positive transmission value setting circuit WBR in Figure 1 modulates the signal based on the error amplification value between the short-circuit occurrence time detection signal Tsd and a predetermined short-circuit occurrence time setting signal Tsr, and outputs a base period positive transmission value setting signal Wbr. The base period positive transmission value Wb is set by this base period positive transmission value setting signal Wbr. This circuit modulates the base period positive transmission value setting signal Wbr within a range of values ​​smaller than the value of the positive transmission peak value setting signal Wsr, so that a short circuit occurs at a specific point in time during the base period. For example, the specific point in time is 1 ms after the start of the base period. This method ensures that a short circuit occurs reliably at a specific point in the base period, allowing for a periodic repetition of the arc generation period and the short-circuit period. As a result, stable welding with minimal spatter generation can be achieved.

[0063] When a short circuit occurs at time t41, 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 throughout the base period Tb. At time t42, 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 in Figure 1 becomes low. In response to this, 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, the generation of spatter associated with the release of the short circuit is very small. The reverse peak value Wr mentioned above is set by the reverse peak value setting signal Wrr shown in Figure 1.

[0064] 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.

[0065] At time t5, as shown in Figure (D), the polarity switching signal Spn changes to a low level, so the period from time t5 to t6 becomes the electrode negative polarity period Ten. During the predetermined electrode negative polarity period Ten from time t5 to t6, as shown in Figure (A), a negative electrode negative polarity current Ien with a current-modulated, pulsed waveform is applied, and the electrode negative polarity current Ien rises to a negative base current Ib just before the end of the electrode negative polarity period Ten. As shown in Figure (B), a negative electrode negative polarity voltage Ven with a pulsed waveform is applied between the welding wire and the base material. Simultaneously, as shown in Figure (C), the feed rate Fw becomes the electrode negative polarity period feed rate Wn. Since this figure is for the case where Wn < 0, the feed is in the reverse feed state. If Wn = 0, the feed is stopped. If Wn > 0, the feed is in the forward feed state. The value of Wn changes according to the length of the electrode negative polarity period Ten. The value of the electrode negative polarity current Ien is modulated and controlled so that the value of the electrode negative polarity current ratio calculation signal Rnd in Figure 1 is equal to the value of the electrode negative polarity current ratio setting signal Rnr in Figure 1. As a result, the electrode negative polarity current ratio becomes a predetermined value, thus improving welding quality. The electrode negative polarity period Ten is set by the electrode negative polarity period setting signal Tnr in Figure 1. The electrode negative polarity current Ien is set by the electrode negative polarity current control setting signal Incr in Figure 1. The electrode negative polarity period feed rate Wn is set by the electrode negative polarity period feed rate setting signal Wnr in Figure 1.

[0066] 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 base period positive feed value Wb 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, when 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, the forward transmission peak value Ws and / or reverse transmission peak value Wr are modulated and controlled so that the value of the transmission speed average value detection signal Fad in Figure 1 is equal to the value of the transmission speed average value setting signal Far in Figure 1. As a result, the average value of the transmission speed Fw is always controlled to a predetermined value.

[0067] Figure 3 is a timing chart of each signal in the welding apparatus shown in Figure 1, illustrating an AC pulsed 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 greater 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 polarity switching signal Spn. The operation of each signal will be explained below with reference to this figure.

[0068] 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.

[0069] The welding current Iw shown in Figure (A) and the welding voltage Vw shown in Figure (B) are positive values ​​above 0 when the electrode is positive polarity EP, and negative values ​​below 0 when the electrode is negative polarity EN. The feed rate Fw shown in Figure (C) is a forward feed state where the material is fed forward towards the base material when the value above 0 is positive, and a reverse feed state where the material is fed backward away from the base material when the value below 0 is negative. The polarity switching signal Spn shown in Figure (D) is at a high level during the electrode positive polarity period Tep from time t1 to t52, and at a low level during the electrode negative polarity period Ten from time t52 to t6.

[0070] At time t1, as shown in Figure (D), the polarity switching signal Spn changes from a low level to a high level, resulting in a positive electrode polarity period Tep. In response to this, at time t1, as shown in Figure (A), the welding current Iw changes from a negative base current Ib to a positive base current Ib, and as shown in Figure (B), the welding voltage Vw changes from a negative arc voltage value to a positive arc voltage value. During the predetermined peak rise period Tu from time t1 to t2, as shown in Figure (A), a peak rise current Iu increases from a current-modulated base current Ib to a current-modulated peak current Ip, and as shown in Figure (B), a peak rise voltage increases from a base voltage Vb to a peak voltage Vp, which is applied between the welding wire and the base material.

[0071] As shown in Figure (C), the feed rate Fw begins to change from the electrode negative polarity period feed rate Wn at a point one unit before the start of the peak rise period Tu at time t1, by the first early period Ta1. It then changes during the feed rate rise period Tfu and reaches the positive feed peak value Ws before the end of the peak rise period Tu at time t2. The reason the positive feed peak value Ws is reached before time t2 is that the feed rate 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 positive feed peak value Ws is set by the positive feed peak value setting signal Wsr 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 time Tfu mentioned above is set by the feed rate rise time setting signal Tfur shown in Figure 1.

[0072] 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 by the peak period setting signal Tpr in Figure 1.

[0073] 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. 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 base period positive feed value Wb before the end of the peak fall period Tk at time t4. The reason the base period positive feed value Wb 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 base period positive feed value Wb is set to be less than the positive feed peak value Ws. The peak fall period Tk is set by the peak fall period setting signal Tkr in Figure 1. The second early period Ta2 is set by the second early period setting signal Ta2r in Figure 1. The feed rate fall period Tfk is set by the feed rate fall period setting signal Tfkr in Figure 1.

[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). The base period Tb is set by the base period setting signal Tbr shown in Figure 1.

[0075] If a short circuit occurs between the welding wire and the base metal at time t41, near the end of the base period Tb, due to disturbances such as irregular movement of the molten pool, the welding voltage Vw will rapidly decrease to a short-circuit voltage of a few volts, as shown in Figure (B), and the short-circuit detection signal Sd in Figure 1 will reach a high level. As described above, the base period positive transmission value setting circuit WBR in Figure 1 performs modulation control based on the error amplification value between the short-circuit occurrence time detection signal Tsd and a predetermined short-circuit occurrence time setting signal Tsr, and outputs the base period positive transmission value setting signal Wbr. The base period positive transmission value Wb is set by this base period positive transmission value setting signal Wbr. This circuit modulates the base period positive transmission value setting signal Wbr within a range of values ​​smaller than the value of the positive transmission peak value setting signal Wsr, so that the short circuit occurs at a specific point in time during the base period. In this way, even if the timing of the short circuit occurrence fluctuates temporarily due to disturbances, the timing of the short circuit occurrence can be converged to a specific point in time on average, so that the arc generation period and the short-circuit period can be repeated periodically. As a result, stable welding with less spatter generation can be achieved.

[0076] When a short circuit occurs at time t41, 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 peak value Wr. Furthermore, at time t42, when the short-circuit period exceeds a predetermined long-term short-circuit discrimination value (approximately 5ms), the long-term short-circuit discrimination signal Sld in Figure 1 goes to a high level. 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 peak value setting signal Wlr in Figure 1. When the short-circuit period becomes a long-term short-circuit state, the reverse peak value Wr is accelerated to encourage the release of the short circuit. The above reverse peak value Wr is set by the reverse peak value setting signal Wrr in Figure 1.

[0077] 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, the welding voltage Vw rapidly increases to an arc voltage value of several tens of volts, as shown in Figure (B), 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. At time t52, which is delayed from time t51 when the arc is generated, the electrode transitions to the negative polarity period Ten.

[0078] At time t52, as shown in Figure (D), the polarity switching signal Spn changes to a low level, so the period from time t52 to t6 becomes the electrode negative polarity period Ten. During the predetermined electrode negative polarity period Ten from time t52 to t6, as shown in Figure (A), a negative electrode negative polarity current Ien with a current-modulated, pulsed waveform is applied, and the electrode negative polarity current Ien rises to a negative base current Ib just before the end of the electrode negative polarity period Ten. As shown in Figure (B), a negative electrode negative polarity voltage Ven with a pulsed waveform is applied between the welding wire and the base material. Simultaneously, as shown in Figure (C), the feed rate Fw becomes the electrode negative polarity period feed rate Wn. Since this figure is for the case where Wn > 0, the feed is in the forward feed state. If Wn = 0, the feed is stopped. If Wn < 0, the feed is in the reverse feed state. The value of Wn changes according to the length of the electrode negative polarity period Ten. The value of the electrode negative polarity current Ien is modulated and controlled so that the value of the electrode negative polarity current ratio calculation signal Rnd in Figure 1 is equal to the value of the electrode negative polarity current ratio setting signal Rnr in Figure 1. As a result, the electrode negative polarity current ratio becomes a predetermined value, thus improving welding quality. The electrode negative polarity period Ten is set by the electrode negative polarity period setting signal Tnr in Figure 1. The electrode negative polarity current Ien is set by the electrode negative polarity current control setting signal Incr in Figure 1. The electrode negative polarity period feed rate Wn is set by the electrode negative polarity period feed rate setting signal Wnr in Figure 1.

[0079] 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-tuning 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 base period positive feed value Wb 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, the forward transmission peak value Ws and / or reverse transmission peak value Wr are modulated and controlled so that the value of the transmission speed average value detection signal Fad in Figure 1 is equal to the value of the transmission speed average value setting signal Far in Figure 1. As a result, the average value of the transmission speed Fw is always controlled to a predetermined value.

[0080] Numerical examples for each of the above parameters are shown below: Tu=1ms, Tp=1ms, Tk=1ms, Tb=2~5ms, Ten=1~4ms, Ip=350~450A, Ib=50~150A, Ien(average)=350~500A, Ws=50m / min, Wb=10~30m / min, Wr=-30m / min, Wn=-20~+10m / min, Tfu=0.8ms, Tfk=0.8ms

[0081] The effects of this embodiment will be described below. According to this embodiment, in an AC pulse arc welding control method in which welding is performed by feeding the welding wire in both forward and reverse directions, during the electrode positive polarity period, a peak rise current is supplied that rises from the base current value to the peak current value during the peak rise period, the peak current is supplied during the peak period, a peak fall current is supplied that decreases from the peak current value to the base current value during the peak fall period, the base current is supplied during the base period, and an electrode negative polarity current is supplied during the electrode negative polarity period, and these supply of welding currents are repeated as one pulse period, and arc length control is performed based on the welding voltage set value, the welding wire feeding speed is set to the forward feed peak value during the peak period, to a base period forward feed value smaller than the forward feed peak value during the base period so that a short circuit occurs during the base period, to the reverse feed peak value when a short circuit occurs, to maintain the reverse feed peak value even after the short circuit is released, and to set the electrode negative polarity period feeding speed to reverse feed, feed stop, or forward feed during the electrode negative polarity period. In this embodiment, during the peak period, a peak current greater than or equal to the critical current value is applied, and the feed rate is set to the positive feed peak value to form droplets of appropriate size. During the subsequent base period, a base current less than the critical current value is applied, and the feed rate is set to a base period positive feed value smaller than the positive feed peak value so that a short circuit occurs during the base period. When a short circuit occurs, the base current is applied and the feed rate is set to the negative 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 negative feed peak value to lengthen the arc and prevent the occurrence of another short circuit. During the subsequent electrode negative polarity period, a electrode negative polarity current is applied to increase the melting speed of the welding wire, thereby improving the efficiency of the welding operation. In this embodiment, since the feed rate is set to the negative 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, a short circuit can be reliably generated during the base period, enabling stable AC pulsed arc welding with a periodic repetition of arc generation and short-circuit periods. Furthermore, in this embodiment, the melting rate can be increased by providing a period of negative electrode polarity, thereby improving the efficiency of welding operations.

[0082] More preferably, according to this embodiment, the short-circuit occurrence time from the start of the base period until a short circuit occurs is detected, and the base period forward feed value is modulated and controlled so that the short-circuit occurrence time is equal to the short-circuit occurrence time setting value that sets a specific point in time. In this way, even if the welding state fluctuates due to changes in the distance between the power supply tip and the base material, welding speed, welding position, etc., the base period forward feed value is modulated and controlled so that a short circuit occurs at a specific point in time, thereby enabling stable AC pulsed arc welding that periodically repeats the arc generation period and the short-circuit period.

[0083] More preferably, according to this embodiment, the electrode negative polarity period feeding rate is set according to the duration of the electrode negative polarity period. In this embodiment, as the duration of the electrode negative polarity period increases, the electrode negative polarity period feeding rate is changed from a negative value to a positive value (reverse feeding, feeding stop, forward feeding), thereby stabilizing the droplet formation state and suppressing the occurrence of short circuits with the molten pool, thus improving the welding condition.

[0084] More preferably, according to this embodiment, the start of the negative electrode polarity 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 negative electrode polarity period, causing the arc to regenerate. In such cases, the arc will regenerate with a large welding current, resulting in a large amount of spatter. In this embodiment, the start of the negative electrode polarity period 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.

[0085] More preferably, according to this embodiment, the forward feed peak value and / or reverse feed peak value are modulated and controlled so that the average feed rate is a predetermined value. In this embodiment, the period during which the feed rate is the base period forward feed value and the period during which it is the reverse feed peak value changes depending on the timing of the short circuit that occurs 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, the forward feed peak value and / or reverse feed peak value are modulated and controlled so that the average feed rate is a predetermined value, so that the welding quality can always be kept good.

[0086] More preferably, according to this embodiment, the electrode negative polarity current is modulated and controlled so that the electrode negative polarity current ratio is a predetermined value. In this embodiment, even if the welding state fluctuates, the electrode negative polarity current ratio is maintained at a predetermined value by modulating and controlling the electrode negative polarity current. As a result, in this embodiment, it is possible to suppress the deterioration of welding quality caused by fluctuations in the electrode negative polarity current ratio, such as fluctuations in the bead appearance and penetration shape.

[0087] Furthermore, according to this embodiment, in an AC pulsed arc welding power supply, the welding wire feeding speed is set to the positive feed peak value during the peak period, to a base period positive feed value smaller than the positive feed peak value during the base period so that a short circuit occurs during the base period, to the reverse feed peak value when a short circuit occurs, to maintain the reverse feed peak value even after the short circuit is released, and to the negative electrode period feeding speed of reverse feeding, feeding stopped, or positive feeding during the negative electrode polarity period. The pulsed arc welding power supply according to this embodiment provides the above-mentioned effects.

[0088] More preferably, according to this embodiment, the short-circuit occurrence time setting value is set to a short-circuit occurrence time setting range having an upper limit and a lower limit, and the base period forward feed value is modulated and controlled so that the short-circuit occurrence time falls within the short-circuit occurrence time setting range. In this embodiment, the target value of the short-circuit occurrence time is given a range between the upper and lower limits. In this way, it is possible to suppress the base period forward feed value from changing too sensitively in response to fluctuations in the welding state, thereby stabilizing the welding state.

[0089] 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 a short circuit to continue until the period of negative electrode polarity, leading to an unstable welding state. For this reason, in this embodiment, the base period is made longer to suppress the continuation of the short circuit until the period of negative electrode polarity. When the welding voltage setting is greater than the reference voltage setting, a longer base period can easily cause magnetic blow, leading to an unstable welding state. For this reason, in this embodiment, the base period is made shorter to suppress the occurrence of magnetic blow.

[0090] 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.

[0091] 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.

[0092] 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 electrode negative polarity period feed speed to the positive feed peak value at a point one delay period after the start of the peak rise period, and starts changing from the positive feed peak value to the base period positive 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 to occur during the peak period or peak fall period. In such cases, a short circuit occurs when the welding current is large, resulting in a lot of spatter and poor welding quality. In this embodiment, the feed speed starts changing from the electrode negative polarity period feed speed to the positive feed peak value at a point one delay period after the start of the peak rise period, and starts changing from the positive feed peak value to the base period positive feed value at a point one delay period after the start of the peak fall period. By providing a first and second delay period in this way, the timing of droplet migration can be delayed, thus allowing the occurrence of short circuits associated with droplet migration to occur during the base period. If a short circuit occurs during the base period, the welding current value is small, which suppresses spatter generation and improves welding quality.

[0093] More preferably, according to this embodiment, when the welding voltage setting is greater than the reference voltage setting, the welding wire feed rate starts changing from the electrode negative polarity period feed rate to the positive feed peak value at a point one period before the start of the peak rise period, and starts changing from the positive feed peak value to the base period positive feed value at a point one 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 electrode negative polarity period, and the short circuit is released with a large welding current, resulting in a lot of spatter and poor welding quality. In this embodiment, the feed rate starts changing from the electrode negative polarity period feed rate to the positive feed peak value at a point one period before the start of the peak rise period, and starts changing from the positive feed peak value to the base period positive feed value at a point one period before the start of the peak fall period. By establishing a first early period and a second early period in this way, droplet transfer can be accelerated, thereby guiding the occurrence of short circuits associated with droplet transfer to the base period. If a short circuit occurs during the base period, it will be resolved during the base period, thus suppressing spatter generation and improving welding quality.

[0094] More preferably, according to this embodiment, the first delay period, second delay period, first early period, and 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 at a specific point in 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]

[0095] 1: Welding wire, 2: Base metal, 3: Arc, 4: Welding torch, 5: Feeding 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, FAD: Feeding speed average value detection circuit, Fad: Feeding speed average value detection signal, FAR: Feeding speed average value setting circuit, Far: Feeding speed average value setting signal, FC: Feeding control circuit, Fc: Feeding control signal, FR: Feeding speed setting circuit, Fr: Feeding speed setting signal, Fw: Feeding 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, RND: electrode negative current ratio calculation circuit Rnd: Electrode negative current ratio calculation signal, RNR: Electrode negative polarity current ratio setting circuit, Rnr: Electrode negative polarity current ratio setting signal, INCR: Electrode negative polarity current control setting circuit, Incr: Electrode negative polarity current control setting signal, SD: Short circuit detection circuit, Sd: Short circuit detection signal, SLD: Long-term short circuit detection circuit, Sld: Long-term short circuit detection signal, SPN: Polarity switching circuit, Spn: Polarity switching 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 fall time setting circuit, Tkr: Peak fall time setting signal, Tm: Timer signal, Tp: Peak period, TPR: Peak period setting circuit, Tpr: Peak period setting signal, TSD: Short circuit occurrence time detection circuit, Tsd: Short circuit occurrence time detection signal, TSR: Short circuit occurrence time setting circuit, Tsr: Short circuit occurrence time setting signal, Tu: Peak rise period, TUR: Peak rise period setting circuit, Tur: Peak rise period 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, Wb: Base period positive feed value, WBR: Base period positive feed value setting circuit, Wbr: Base period positive feed value setting signal, WC: Feed speed modulation circuit, WLR: Long-term short-circuit reverse feed peak value setting circuit, Wlr: Long-term short-circuit reverse feed peak value setting signal, WM: Feed motor, Wn: Electrode negative polarity period feed speed, WNR: Electrode negative polarity period feed speed setting circuit, Wnr: Electrode negative polarity period feed speed setting signal, Wr: Reverse feed peak value, Wrr: Reverse feed peak value setting signal, Ws: Forward feed peak value, Wsr: Forward feed peak value setting signal,

Claims

1. In an AC pulsed arc welding control method in which welding is performed by feeding the welding wire in both forward and reverse directions, during the positive electrode polarity period, a peak rise current is supplied that rises from the base current value to the peak current value during the peak rise period, the peak current is supplied during the peak period, a peak fall current is supplied that decreases from the peak current value to the base current value during the peak fall period, the base current is supplied during the base period, and a negative electrode polarity current is supplied during the negative electrode polarity period, and these supply of welding currents is repeated as one pulse period, and the arc length is controlled based on the welding voltage set value, A method for controlling AC pulsed arc welding, characterized in that the feeding speed of the welding wire is set to the forward feeding peak value during the peak period, set to a base period forward feeding value smaller than the forward feeding peak value during the base period so that a short circuit occurs during the base period, set to the reverse feeding peak value when the short circuit occurs, maintain the reverse feeding peak value even after the short circuit is released, and set to the electrode negative polarity period feeding speed for reverse feeding, feeding stop, or forward feeding during the electrode negative polarity period.

2. The AC pulse arc welding control method according to claim 1, characterized in that the short-circuit occurrence time from the start of the base period until the short-circuit occurs is detected, and the base period forward value is modulated and controlled so that the short-circuit occurrence time is equal to the short-circuit occurrence time set value.

3. The AC pulsed arc welding control method according to claim 1 or 2, characterized in that the electrode negative polarity period feeding speed is set according to the duration of the electrode negative polarity period.

4. The AC pulsed arc welding control method according to claim 1 or 2, characterized in that the start of the electrode negative polarity period is delayed until the short circuit is released.

5. The AC pulse arc welding control method according to claim 1 or 2, characterized in that the forward feed peak value and / or the reverse feed peak value are modulated and controlled so that the average value of the feed speed is a predetermined value.

6. The AC pulsed arc welding control method according to claim 1 or 2, characterized in that the electrode negative polarity current is modulated and controlled so that the electrode negative polarity current ratio is a predetermined value.

7. In an AC pulsed arc welding power supply that feeds the welding wire in both forward and reverse directions, during the positive electrode polarity period, a peak rise current is supplied that rises from the base current value to the peak current value during the peak rise period, the peak current is supplied during the peak period, a peak fall current is supplied that decreases from the peak current value to the base current value during the peak fall period, the base current is supplied during the base period, and a negative electrode polarity current is supplied during the negative electrode polarity period, and these supply cycles of welding currents are repeated as one pulse period, and the arc length is controlled based on the welding voltage set value for welding, An AC pulsed arc welding power supply characterized in that the feeding speed of the welding wire is set to the forward feeding peak value during the peak period, to a base period forward feeding value smaller than the forward feeding peak value during the base period so that a short circuit occurs during the base period, to the reverse feeding peak value when the short circuit occurs, to maintain the reverse feeding peak value even after the short circuit is released, and to set the electrode negative polarity period feeding speed to reverse feeding, feeding stopped, or forward feeding during the electrode negative polarity period.

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