Pulse arc welding control method and pulse arc welding power supply

Abstract

To obtain excellent welding quality by suppressing an increase in generation amount of spatters even when a short circuit occurs between a welding wire and a base material in consumable electrode pulse arc welding.SOLUTION: A feed speed Fw of a weld wire is set to a forward feed peak during a peak period from a time t2 to a time t3, and is set to a reverse feed peak during a base period from the time t4 to the time t52, and a start of the peak period at the time t41 is delayed until a short circuit between the weld wire and a base metal generated during the base period at the time t52 is released.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] Pulse arc welding, which involves feeding a welding wire to weld, is used to weld steel and other materials. In pulse arc welding, the welding wire is fed, and a peak-rise current is applied during the peak-rise period, increasing from the base current value to the peak current value. The peak current is applied during the peak period, and a peak-fall current is applied during the peak-fall period, decreasing from the peak current value to the base current value. The base current is applied during the base period, and these welding currents are repeated as one pulse cycle to perform welding. In pulse arc welding, by achieving one droplet transfer per pulse cycle, spatter is reduced and a beautiful bead appearance can be achieved.

[0003] 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 welding wire feed speed is set to be slower than the feed speed at the rising point of the peak current, or the welding wire is fed in a reverse direction, i.e., in a direction away from the workpiece to be welded. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6123069 Summary of the Invention [Problem to be solved by the invention]

[0005] In pulse arc welding, if a short circuit occurs between the welding wire and the base metal, the amount of spatter increases, resulting in poor welding quality. Therefore, an object of the present invention is to provide a pulse arc welding control method and a pulse arc welding power source that can suppress an increase in the amount of spatter and achieve good welding quality even if a short circuit occurs between the welding wire and the base metal. [Means for solving the problem]

[0006] A pulse arc welding control method provided according to a first aspect of the present invention is a pulse arc welding control method for welding by feeding a welding wire in forward and reverse directions, passing a peak rise current that rises from a base current value to a peak current value during a peak rise period, passing the peak current during the peak period, passing a peak fall current that falls from the peak current value to the base current value during a peak fall period, and passing the base current during a base period, repeating the passing of these welding currents as one pulse period, and performing arc length control based on a welding voltage set value, characterized in that the feeding speed of the welding wire is set to a forward feed peak value during the peak period and a reverse feed peak value during the base period, and the start of the peak rise period is delayed until a short circuit between the welding wire and the base metal that occurred during the base period is released.

[0007] As an example, the pulse arc welding control method of the present invention is characterized in that when the short circuit duration is equal to or greater than a reference value, the reverse feed peak value is made earlier.

[0008] As an example, the pulse arc welding control method of the present invention is characterized in that when the welding voltage set value is equal to a reference voltage set value, the base period is set to a reference base period, when the welding voltage set value is a value smaller than the reference voltage set value, the base period is made longer than the reference base period, and when the welding voltage set value is a value larger than the reference voltage set value, the base period is made shorter than the reference base period.

[0009] As an example, the pulse arc welding control method of the present invention is characterized in that the forward feed peak value and / or the reverse feed peak value are changed so that the average value of the feed speed becomes a predetermined value.

[0010] As an example, the pulse arc welding control method of the present invention is characterized in that the value of the base current is smaller during the short circuit period than during the arc generation period.

[0011] A second aspect of the present invention provides a pulse arc welding power supply that feeds a welding wire in forward and reverse directions, passes a peak rise current that rises from a base current value to a peak current value during a peak rise period, passes the peak current during the peak period, passes a peak fall current that falls from the peak current value to the base current value during a peak fall period, and passes the base current during a base period, repeating the passing of these welding currents as one pulse period, and performs arc length control based on a welding voltage set value for welding, characterized in that the pulse arc welding power supply sets a feed speed of the welding wire to a forward feed peak value during the peak period and to a reverse feed peak value during the base period, and delays the start of the peak rise period until a short circuit between the welding wire and the base metal that occurred during the base period is released. [Effects of the Invention]

[0012] According to the above configuration, for example, with respect to the pulse arc welding control method and pulse arc welding power source, even if a short circuit occurs between the welding wire and the base metal, the amount of spatter generated can be suppressed from increasing, thereby achieving good welding quality. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a block diagram of a welding device for carrying out a pulse arc welding control method according to an embodiment of the present invention. [Figure 2]2 is a timing chart of signals in the welding device of FIG. 1, illustrating a pulse arc welding control method according to an embodiment of the present invention, in which the value of welding voltage setting signal Vr is smaller than the value of reference voltage setting signal Vsr. [Figure 3] 2 is a timing chart of signals in the welding device of FIG. 1 illustrating a pulse arc welding control method according to an embodiment of the present invention, in which the value of welding voltage setting signal Vr is greater than the value of reference voltage setting signal Vsr. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0015] 1 is a block diagram of a welding apparatus for carrying out a pulse arc welding control method according to an embodiment of the present invention. The welding apparatus is mainly composed of a pulse arc welding power source PS, a robot control device RC, a robot (not shown), etc., all of which are enclosed by a dashed line. Each block will be described below with reference to the diagram.

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

[0017] The power control circuit MC receives an AC commercial power supply (not shown) such as a three-phase 200V, performs output control such as inverter control in accordance with a drive signal Dv described below, and outputs a welding voltage Vw and welding current Iw suitable for welding. Although not shown, the power control circuit MC includes a primary rectifier circuit that rectifies the AC commercial power supply, a capacitor that smoothes the rectified DC, an inverter circuit that converts the smoothed DC into high-frequency AC in accordance with the drive signal Dv, an inverter transformer that steps down the high-frequency AC to a voltage value suitable for welding, and a secondary rectifier circuit that rectifies 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 smoothes the output of the power control circuit MC.

[0019] The feed motor WM is driven to rotate by a feed control signal Fc, which will be described later. The welding wire 1 is fed forward and backward through the welding torch 4 at a feed speed Fw by the rotation of a feed roll 5 connected to the feed motor WM, and an arc 3 is generated between the welding wire 1 and the base material 2. The feed motor WM and the welding torch 4 are mounted on a robot. A welding voltage Vw is applied between a power feed 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 feed speed average value setting circuit FAR outputs a feed speed average value 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 receives the reference voltage setting signal Vsr and the voltage fine adjustment signal Dvr as inputs, adds the two values, and outputs the 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, which is centrally set by the welding current average value setting signal Iar, using 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 the welding voltage detection signal Vd (by passing 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 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 receives the voltage error amplified 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. This circuit performs current modulation control of 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 so that the arc length is maintained at an appropriate value. It is also possible to perform current modulation control of only the peak current setting signal Ipr, and set the base current setting signal Ibr to a predetermined value.

[0024] The short circuit determination circuit SD receives the welding voltage detection signal Vd as input, and outputs a short circuit determination signal Sd that goes to a high level when this value is less than the short circuit determination value (approximately 10 V) and determines that the current is in a short circuit period, and goes to a low level when this value is equal to or greater than the short circuit determination value and determines that the current is in an arc generation period.

[0025] The short circuit period base current setting circuit IBS outputs a predetermined short circuit period base current setting signal Ibs. The value of the short circuit period base current setting signal Ibs is set to be equal to or less than 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, the peak period setting circuit TPR outputs a predetermined peak period setting signal Tpr, and the peak fall period setting circuit TKR outputs a predetermined peak fall period setting signal Tkr.

[0027] Base period setting circuit TBR receives the above-described fine voltage adjustment signal Dvr as an input, performs the calculation of the following equation, and outputs base period setting signal Tbr. Therefore, when the value of welding voltage setting signal Vr is equal to the value of reference voltage setting signal Vsr, it sets the value of base period setting signal Tbr to the reference base period, when the value of welding voltage setting signal Vr is smaller than the value of reference voltage setting signal Vsr, it makes the value of base period setting signal Tbr shorter than the reference base period, and when the value of welding voltage setting signal Vr is larger than the value of reference voltage setting signal Vsr, it makes the value of base period setting signal Tbr longer than the reference base period. Tbr = (reference base period) + Dvr × K where K is a constant, for example, K=-0.4 when Dvr<0, and K=-0.2 when Dvr>0. For example, if the reference base period is 3 ms, then when Dvr=-5V, Tbr=5 ms, and when Dvr=+5V, Tbr=2 ms.

[0028] The welding current setting circuit IR receives as inputs a first early period setting signal Ta1r (described later), the short circuit determination 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, performs the following processing, and outputs a welding current setting signal Ir and a 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 decreasing 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, and when the short circuit determination signal Sd is at a low level (arcing period), a welding current setting signal Ir is output which has the value of the base current setting signal Ibr, and when the short circuit determination signal Sd is at a high level (short circuit period), a welding current setting signal Ir is output which has the value of the short circuit period base current setting signal Ibs. However, the base period Tb is extended from the time when the short circuit determination signal Sd changes from a high level (short circuit period) to a low level (arcing period) until the period determined by the first early period setting signal Ta1r has elapsed. 5) Repeat steps 1) to 4) above.

[0029] The feed speed modulation circuit WC receives the above-mentioned feed speed average value setting signal Far and a feed speed average value detection signal Fad (described later) as inputs, performs modulation control based on an error amplification signal of both values, and outputs a forward feed peak value setting signal Wsr and a reverse feed peak value setting signal Wrr. This circuit modulates and controls the value of the feed speed average value detection signal Fad so that it becomes equal to the value of the feed speed average value setting signal Far. It is also possible to modulate and control one of the forward feed peak value setting signal Wsr or the reverse feed peak value setting signal Wrr, and set the other to a predetermined value.

[0030] The welding current detection circuit ID detects the welding current Iw and outputs a welding current detection signal Id. The current error amplifier circuit EI amplifies the error between the welding current setting signal Ir(+) and the welding current detection signal Id(-) and outputs a current error amplification signal Ei. The drive circuit DV receives the current error amplification signal Ei and an activation signal On from the robot control device RC (described later), and performs pulse width modulation control and the like based on the current error amplification signal Ei when the activation signal On is high (welding starts) and outputs a drive signal Dv for driving the inverter circuit in the power control circuit MC, but does not output the drive signal Dv when the activation signal On is low (welding stops).

[0031] The first delay period setting circuit TD1R receives the above-mentioned voltage fine adjustment signal Dvr, calculates 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 increases as the absolute value of the difference (voltage fine adjustment signal Dvr) between the value of the welding voltage setting signal Vr and the value of the reference voltage setting signal Vsr increases. For example, when Dvr = -1 V, Td1r = 0.1 ms, and when Dvr = -5 V, Td1r = 0.5 ms.

[0032] The second delay period setting circuit TD2R receives the above-mentioned voltage fine adjustment signal Dvr as an input, calculates 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 increases as the absolute value of the difference (voltage fine adjustment signal Dvr) between the value of the welding voltage setting signal Vr and the value of the reference voltage setting signal Vsr increases. Here, Td2r = Td1r, but the two values ​​may be set to different values.

[0033] The first early period setting circuit TA1R receives the voltage fine adjustment signal Dvr, calculates 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 increases as the absolute value of the difference (voltage fine adjustment signal Dvr) between the welding voltage setting signal Vr and the reference voltage setting signal Vsr increases. For example, when Dvr = +1V, Ta1r = 0.2 ms, and when Dvr = +5V, Ta1r = 1.0 ms.

[0034] The second early period setting circuit TA2R receives the above-mentioned voltage fine adjustment signal Dvr as an input, calculates 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 increases as the absolute value of the difference (voltage fine adjustment signal Dvr) between the value of the welding voltage setting signal Vr and the value of the reference voltage setting signal Vsr increases. Here, Ta2r = Ta1r, but the two values ​​may be set to different values.

[0035] The feed speed rise period setting circuit TFUR outputs a predetermined feed speed rise period setting signal Tfur, which is preferably shorter than the peak rise period setting signal Tur.

[0036] The feed speed fall period setting circuit TFKR outputs a predetermined feed speed fall period setting signal Tfkr, which is preferably shorter than the peak fall period setting signal Tkr.

[0037] The long-term short-circuit determination circuit SLD receives the short-circuit determination signal Sd as input, and outputs a long-term short-circuit determination signal Sld that goes to High level when the long-term short-circuit determination value (approximately 5 ms) has elapsed since the short-circuit determination signal Sd changed to High level, and then goes to Low level when the short-circuit determination signal Sd goes to Low level thereafter. Therefore, the long-term short-circuit determination signal Sld is a signal that stays at High level while the short-circuit duration is equal to or greater than the long-term short-circuit determination value.

[0038] The long-term short-circuit reverse-transmission peak value setting circuit WLR outputs a predetermined long-term short-circuit reverse-transmission peak value setting signal Wlr. The long-term short-circuit reverse-transmission peak value setting signal Wlr has a negative value and an absolute value larger than that of the above-mentioned reverse-transmission peak value setting signal Wrr.

[0039] The feeding speed setting circuit FR receives as inputs the short circuit determination signal Sd, the long term short circuit determination signal Sld, the long term short circuit reverse feed peak value setting signal Wlr, the voltage fine adjustment signal Dvr, the forward feed peak value setting signal Wsr, the reverse feed peak value setting signal Wrr, the timer signal Tm, the feeding speed rise period setting signal Tfur, the feeding 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 a feeding speed setting signal Fr. (1) When the voltage fine adjustment signal Dvr<0 1) When a period of Td1r has elapsed since the timer signal Tm=1 (peak rise period), the value of the reverse feed peak value setting signal Wrr starts to change, 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. 2) When the period Td2r has elapsed since the timer signal Tm=3 (peak falling period), the forward feed peak value setting signal Wsr starts to change in value, and changes to the reverse feed peak value setting signal Wrr during the period determined by the feed speed falling period setting signal Tfkr. However, while the long-term short circuit determination signal Sld is at a high level, the reverse feed peak value setting signal Wrr is replaced by the long-term short circuit reverse feed peak value setting signal Wlr. (2) When the voltage fine adjustment signal Dvr>0 1) When a period of (Tbr-Ta1r) has elapsed since the timer signal Tm=4 (base period) and the short circuit determination signal Sd is at a low level (arc generation period), the value of the reverse feed peak value setting signal Wrr starts to change, 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. 2) When the period (Tpr-Ta2r) has elapsed since the timer signal Tm=2 (peak period), the forward feed peak value setting signal Wsr starts to change in value, and changes to the reverse feed peak value setting signal Wrr during the period determined by the feed speed fall period setting signal Tfkr. However, while the long-term short circuit determination signal Sld is at a high level, the reverse feed peak value setting signal Wrr is replaced by the long-term short circuit reverse feed peak value setting signal Wlr.

[0040] The feed speed average value detection circuit FAD receives the feed speed setting signal Fr, calculates an average value, and outputs a feed speed average value detection signal Fad. The average value may be calculated by directly detecting the feed speed Fw instead of the feed speed setting signal Fr.

[0041] The feed control circuit FC receives as input the feed speed setting signal Fr and a start signal On from the robot control device RC described later, and outputs a feed control signal Fc to the feed motor WM for feeding the welding wire 1 at the value of the feed speed setting signal Fr when the start signal On is at a high level (welding start), and outputs a feed control signal Fc to the feed motor WM for stopping feeding when the start signal On is at a low level.

[0042] The robot control device RC moves a robot (not shown) in accordance with a pre-taught work program, and outputs a start signal On to command the start or stop of welding.

[0043] 2 is a timing chart of each signal in the welding device of FIG. 1, illustrating a pulse arc welding control method according to an embodiment of the present invention. This figure shows a case where the value of the welding voltage setting signal Vr in FIG. 1 is smaller than the value of the reference voltage setting signal Vsr in FIG. 1. (A) in FIG. 2 shows the change over time of the welding current Iw, (B) in FIG. 2 shows the change over time of the welding voltage Vw, and (C) in FIG. 2 shows the change over time of the welding wire feed speed Fw. The operation of each signal will be explained below with reference to the figures.

[0044] In the figure, because the value of the voltage fine adjustment signal Dvr in FIG. 1 is set to a negative value, the value of the welding voltage setting signal Vr in FIG. 1 is smaller than the value of the reference voltage setting signal Vsr in FIG. 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 the welding quality. In such a case, 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.

[0045] The feed speed Fw shown in Figure 1(C) indicates a forward feed state in which the material is fed forward in a direction toward the base material when it is a positive value above 0, and a reverse feed state in which the material is fed backward in a direction away from the base material when it is a negative value below 0.

[0046] During a predetermined peak rise period Tu from time t1 to t2, as shown in FIG. 1A, a peak rise current Iu is supplied, which rises from a base current Ib that is current modulation controlled to a peak current Ip that is current modulation controlled, and as shown in FIG. 1B, a peak rise voltage that rises from a base voltage Vb to a peak voltage Vp is applied between the welding wire and the base metal.

[0047] As shown in FIG. 1C, the feed speed Fw starts to change from the reverse feed peak value Wr at a time point a first delay period Td1 after the start of the peak rise period Tu at time t1. Then, the feed speed Fw changes during the feed speed rise period Tfu and reaches the forward feed peak value Ws at a time point after the end of the peak rise period Tu at time t2. The feed speed rise period Tfu is set to be equal to or shorter than the peak rise period Tu. The peak rise period Tu is set by the peak rise period setting signal Tur in FIG. 1. The base current Ib is set by the base current setting signal Ibr in FIG. 1. The peak current Ip is set by the peak current setting signal Ipr in FIG. 1. The reverse feed peak value Wr is set by the reverse feed peak value setting signal Wrr in FIG. 1. The forward feed peak value Ws is set by the forward feed peak value setting signal Wsr in FIG. 1. The first delay period Td1 is set by the first delay period setting signal Td1r in FIG. 1. The above-mentioned feed speed rise period Tfu is set by the feed speed rise period setting signal Tfur of FIG.

[0048] During a predetermined peak period Tp from time t2 to t3, a peak current Ip that is modulated and controlled flows as shown in (A) of the figure, and a peak voltage Vp is applied between the welding wire and the base metal as shown in (B) of the figure. The peak period Tp is set by a peak period setting signal Tpr in FIG.

[0049] During a predetermined peak fall period Tk from time t3 to time t4, as shown in FIG. 1A, a peak fall current Ik is supplied, decreasing from a peak current Ip, which is modulated by current modulation, to a base current Ib, which is modulated by current modulation. As shown in FIG. 1B, a peak fall voltage, which decreases from a peak voltage Vp to a base voltage Vb, is applied between the welding wire and the base metal. As shown in FIG. 1C, the feed speed Fw starts to change from the forward feed peak value Ws at a time point after the second delay period Td2 from the start of the peak fall period Tk at time t3. Then, the feed speed Fw changes during the feed speed fall period Tfk, and reaches the reverse feed peak value Wr at a time point after the end of the peak fall period Tk at time t4. The feed speed fall period Tfk is set to be equal to or shorter than the peak fall period Tk. The peak fall period Tk is set by the peak fall period setting signal Tkr in FIG. 1. The second delay period Td2 is set by the second delay period setting signal Td2r in FIG. 1. The above-mentioned feeding speed fall period Tfk is set by the feeding speed fall period setting signal Tfkr in FIG.

[0050] During a predetermined base period Tb from time t4 to t5, as shown in FIG. 1(A), a base current Ib that is current modulation controlled is supplied, and as shown in FIG. 1(B), a base voltage Vb is applied between the welding wire and the base metal. As shown in FIG. 1(C), the feed speed Fw is set to the reverse feed peak value Wr. The base period Tb is set by the base period setting signal Tbr of FIG. 1.

[0051] When a short circuit occurs between the welding wire and the base metal at time t41 during the base period Tb, as shown in FIG. 1B, the welding voltage Vw suddenly decreases to a short circuit voltage value of several volts, and the short circuit determination signal Sd in FIG. 1 goes high. In response to this, as shown in FIG. 1A, the base current Ib decreases to a value determined by the short circuit period base current setting signal Ibs (approximately 30 to 50 A) in FIG. 1. Furthermore, at time t42, when the short circuit period exceeds a predetermined long-term short circuit determination value (approximately 5 ms), the long-term short circuit determination signal Sld in FIG. 1 goes high. In response to this, as shown in FIG. 1C, the feed speed Fw is accelerated to a value determined by the long-term short circuit reverse feed peak value setting signal Wlr (e.g., −30 m / min) in FIG. 1. When the short circuit period becomes a long-term short circuit state, the reverse feed peak value is increased to facilitate release of the short circuit. At time t43, when the short circuit is released and an arc is re-strike, as shown in Fig. 1B, the welding voltage Vw rises sharply to an arc voltage value of several tens of volts, and the short circuit determination signal Sd and long-term short circuit determination signal Sld in Fig. 1 go low. In response to this, as shown in Fig. 1A, the base current Ib increases to a value determined by the base current setting signal Ibr, and as shown in Fig. 1C, the feed speed Fw decelerates to a value determined by the reverse feed peak value setting signal Wrr. Since the value of the base current Ib when the short circuit is released at time t43 is a small value determined by the short circuit period base current setting signal Ibs, the generation of spatter accompanying the release of the short circuit is extremely small.

[0052] The first delay period Td1 and the second delay period Td2 increase as the absolute value of the difference (fine voltage adjustment signal Dvr) between the welding voltage setting signal Vr and the reference voltage setting signal Vsr increases, for example, in the range of 0.1 to 0.5 ms. The base period Tb decreases as the value of the welding voltage setting signal Vr increases, for example, in the range of 2 to 5 ms. 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 also change. Furthermore, when the short circuit period becomes a long-term short circuit state, the reverse feed peak value accelerates. These factors cause the average value of the feed speed Fw to change. When the average value of the feed speed Fw changes, the bead appearance, penetration depth, etc. fluctuate, resulting in poor welding quality. To prevent this, in this embodiment, the forward feed peak value Ws and / or the reverse feed peak value Wr are feedback-controlled so that the value of the feed speed average value detection signal Fad in FIG. 1 is equal to the value of the feed speed average value setting signal Far in FIG. 1. As a result, the average value of the feeding speed Fw is always controlled to a predetermined value.

[0053] 3 is a timing chart of each signal in the welding device of FIG. 1, illustrating a pulse arc welding control method according to an embodiment of the present invention. This figure shows a case where the value of the welding voltage setting signal Vr in FIG. 1 is greater than the value of the reference voltage setting signal Vsr in FIG. 1. (A) in FIG. 3 shows the change over time of the welding current Iw, (B) in FIG. 3 shows the change over time of the welding voltage Vw, and (C) in FIG. 3 shows the change over time of the welding wire feed speed Fw. The operation of each signal will be explained below with reference to the figures.

[0054] In the figure, because the value of the voltage fine adjustment signal Dvr in FIG. 1 is set to a positive value, the value of the welding voltage setting signal Vr in FIG. 1 is greater than the value of the reference voltage setting signal Vsr in FIG. 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 metal, welding may be performed by setting the arc length longer than the appropriate value to improve weld 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.

[0055] The feed speed Fw shown in Figure 1(C) indicates a forward feed state in which the material is fed forward in a direction toward the base material when it is a positive value above 0, and a reverse feed state in which the material is fed backward in a direction away from the base material when it is a negative value below 0.

[0056] During a predetermined peak rise period Tu from time t1 to t2, as shown in FIG. 1A, a peak rise current Iu is supplied, which rises from a base current Ib that is current modulation controlled to a peak current Ip that is current modulation controlled, and as shown in FIG. 1B, a peak rise voltage that rises from a base voltage Vb to a peak voltage Vp is applied between the welding wire and the base metal.

[0057] As shown in FIG. 1C, the feed speed Fw starts to change from the reverse feed peak value Wr at a time point a first early period Ta1 before the start of the peak rise period Tu at time t1. Then, the feed speed Fw changes during the feed speed rise period Tfu and reaches the forward feed peak value Ws at a time point before the end of the peak rise period Tu at time t2. The reason why the forward feed peak value Ws is reached at a time point before time t2 is because the feed speed rise period Tfu is set to be equal to or shorter than the peak rise period Tu. The peak rise period Tu is set by the peak rise period setting signal Tur in FIG. 1. The base current Ib is set by the base current setting signal Ibr in FIG. 1. The peak current Ip is set by the peak current setting signal Ipr in FIG. 1. The reverse feed peak value Wr is set by the reverse feed peak value setting signal Wrr in FIG. 1. The forward feed peak value Ws is set by the forward feed peak value setting signal Wsr in FIG. 1. The first early period Ta1 is set by a first early period setting signal Ta1r in Fig. 1. The feeding speed rise period Tfu is set by a feeding speed rise period setting signal Tfur in Fig. 1.

[0058] During a predetermined peak period Tp from time t2 to t3, a peak current Ip that is modulated and controlled flows as shown in (A) of the figure, and a peak voltage Vp is applied between the welding wire and the base metal as shown in (B) of the figure. The peak period Tp is set by a peak period setting signal Tpr in FIG.

[0059] During a predetermined peak fall period Tk from time t3 to time t4, as shown in FIG. 1A, a peak fall current Ik is supplied, decreasing from a peak current Ip, which is modulated by current modulation, to a base current Ib, which is modulated by current modulation. As shown in FIG. 1B, a peak fall voltage, which decreases from a peak voltage Vp to a base voltage Vb, is applied between the welding wire and the base metal. As shown in FIG. 1C, the feed speed Fw starts to change from the forward feed peak value Ws at a time point that is a second early period Ta2 before the start of the peak fall period Tk at time t3. Then, the feed speed Fw changes during the feed speed fall period Tfk, and reaches a reverse feed peak value Wr before the end of the peak fall period Tk at time t4. The reason the reverse feed peak value Wr is reached before time t4 is because the feed speed fall period Tfk is set to be equal to or shorter than the peak fall period Tk. The peak fall period Tk is set by the peak fall period setting signal Tkr shown in FIG. 1. The second early period Ta2 is set by the second early period setting signal Ta2r in Fig. 1. The feeding speed falling period Tfk is set by the feeding speed falling period setting signal Tfkr in Fig. 1.

[0060] During a predetermined base period Tb from time t4 to t5, as shown in FIG. 1(A), a base current Ib that is current modulation controlled is supplied, and as shown in FIG. 1(B), a base voltage Vb is applied between the welding wire and the base metal. As shown in FIG. 1(C), the feed speed Fw is set to the reverse feed peak value Wr. The base period Tb is set by the base period setting signal Tbr of FIG. 1.

[0061] When a short circuit occurs between the welding wire and the base metal at time t41, just before the end of the base period Tb, the welding voltage Vw suddenly decreases to a short circuit voltage value of several volts, as shown in FIG. 1B, and the short circuit determination signal Sd in FIG. 1 goes high. In response to this, the base current Ib decreases to a value determined by the short circuit period base current setting signal Ibs in FIG. 1, as shown in FIG. 1A. Furthermore, at time t42, when the short circuit period exceeds a predetermined long-term short circuit determination value (approximately 5 ms), the long-term short circuit determination signal Sld in FIG. 1 goes high. In response to this, the feed speed Fw is accelerated to a value determined by the long-term short circuit reverse feed peak value setting signal Wlr in FIG. 1, as shown in FIG. 1C. When the short circuit period becomes a long-term short circuit state, the reverse feed peak value is increased to facilitate release of the short circuit.

[0062] At time t5, the base period Tb is extended because the short circuit period continues even after the period determined by the base period setting signal Tbr has ended. At time t51, the short circuit is released and the arc is re-struck. As shown in FIG. 1B, the welding voltage Vw rapidly increases to an arc voltage value of several tens of volts, and the short circuit determination signal Sd and the long-term short circuit determination signal Sld in FIG. 1 become low. The base current Ib at the time the short circuit is released is a small value determined by the short circuit period base current setting signal Ibs, so spatter generation accompanying the release of the short circuit is extremely small. When the arc is re-struck, the base current Ib increases to a value determined by the base current setting signal Ibr, as shown in FIG. 1A. As shown in FIG. 1C, the feed speed Fw begins to change from the reverse feed peak value Wr to the forward feed peak value Ws. At time t52, when the first early period Ta1 has elapsed from time t51, the peak rise period Tu begins. The above-described operations are then repeated.

[0063] The first early period Ta1 and the second early period Ta2 increase as the absolute value of the difference (fine voltage adjustment signal Dvr) between the value of the welding voltage setting signal Vr and the value of the reference voltage setting signal Vsr increases, for example, in the range of 0.2 to 1.0 ms. The base period Tb decreases as the value of the welding voltage setting signal Vr increases, for example, in the range of 2 to 5 ms. 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 also change. Furthermore, if the short circuit period becomes a long-term short circuit state, the reverse feed peak value accelerates, and if the short circuit period is still in effect at the end of the base period Tb, the base period Tb is extended. These factors cause the average value of the feed speed Fw to change. When the average value of the feed speed Fw changes, the bead appearance, penetration depth, etc. fluctuate, resulting in poor welding quality. To prevent this, in this embodiment, the forward feed peak value Ws and / or the reverse feed peak value Wr are feedback controlled so that the value of the feed speed average value detection signal Fad in Fig. 1 becomes equal to the value of the feed speed average value setting signal Far in Fig. 1. As a result, the average value of the feed speed Fw is always controlled to a predetermined value.

[0064] Examples of values ​​for the above parameters are shown below: Tu=1ms, Tp=1ms, Tk=1ms, Ip=350-450A, Ib=50-150A, Ws=50m / min, Wr=-20m / min, Tfu=0.8ms, Tfk=0.8ms

[0065] The effects of this embodiment are described below. According to this embodiment, a pulse arc welding control method includes forward and reverse feeding a welding wire, supplying a peak rise current that increases from a base current value to a peak current value during a peak rise period, supplying a peak current during the peak period, supplying a peak fall current that decreases from the peak current value to the base current value during a peak fall period, and supplying a base current during the base period. These welding currents are repeated as one pulse period, and arc length control is performed based on a welding voltage set value. In this method, the welding wire feed speed is set to a forward feed peak value during the peak period and a reverse feed peak value during the base period. The start of the peak rise period is delayed until a short circuit between the welding wire and the base metal that occurred during the base period is released. The supply of the peak current during the peak period forms a droplet at the tip of the welding wire. By supplying the welding wire in reverse during the subsequent base period, an upward force can be continuously applied to the droplet throughout the base period, thereby ensuring that the droplet is transferred to the molten pool. In this case, if the feed rate change period (feed rate rise period and feed rate fall period) is set to a period shorter than the peak rise period and peak fall period, the upward force acting on the droplet can be strengthened, thereby ensuring more reliable droplet transfer. As a result, a one-pulse-period, one-droplet-transfer state can be maintained even if the welding condition fluctuates. Furthermore, a short circuit that occurred during the base period may occasionally continue at the end of the base period, and the short circuit may be released during the peak rise period or peak period of the next period, causing an arc to re-ignite. In such cases, the arc re-ignites with a high welding current value, resulting in increased spatter generation. In this embodiment, the start of the peak rise period of the next period is delayed until the short circuit that occurred during the base period is released. As a result, spatter generation can be reduced and welding quality can be improved, even when the short circuit has not been released even at the end of the base period.

[0066] More preferably, according to this embodiment, when the duration of the short circuit is equal to or greater than a reference value, the reverse feed peak value is increased. When a long-term short circuit occurs, in which the duration of the short circuit is equal to or greater than the reference value, the welding state becomes unstable. In this embodiment, when a long-term short circuit occurs, the reverse feed peak value is increased to quickly release the short circuit. As a result, this embodiment can suppress instability in the welding state due to the occurrence of a long-term short circuit.

[0067] More preferably, according to this embodiment, when the welding voltage set value is equal to the reference voltage set value, the base period is set to the reference base period; when the welding voltage set value is smaller than the reference voltage set value, the base period is made longer than the reference base period; and when the welding voltage set value is larger than the reference voltage set value, the base period is made shorter than the reference base period. When the welding voltage set value is smaller than the reference voltage set value, the arc length is short, which can cause a short circuit to continue into the next cycle, making the welding state unstable. For this reason, in this embodiment, the base period is made longer to prevent the short circuit from continuing into the next cycle. When the welding voltage set value is larger than the reference voltage set value, a longer base period can cause magnetic arc blow, making the welding state unstable. For this reason, in this embodiment, the base period is made shorter to prevent magnetic arc blow from occurring.

[0068] More preferably, according to this embodiment, the forward feed peak value and / or the reverse feed peak value are changed so that the average value of the feed speed becomes a predetermined value. In this embodiment, if a short circuit continues even at the end of the base period, the base period is extended. Furthermore, in this embodiment, if a long-term short circuit occurs, the reverse feed peak value is increased. Furthermore, in this embodiment, if the welding voltage set value changes, the length of the base period changes. The average value of the feed speed changes due to such factors. If the average value of the feed speed changes, the bead appearance, penetration depth, etc. will fluctuate, and the welding quality will deteriorate. In this embodiment, the forward feed peak value and / or the reverse feed peak value are feedback controlled so that the average value of the feed speed becomes a predetermined value, so that the welding quality can always be improved.

[0069] More preferably, according to this embodiment, the value of the base current during the short circuit period is smaller than that during the arc generation period. If the value of the base current during the short circuit period is smaller than that during the arc generation period, the current value when the arc re-strikes is small, thereby reducing the generation of spatter. Normally, if the current value during the short circuit period is reduced, the short circuit cannot be released early, resulting in a long-term short circuit and making the welding state unstable. In contrast, in this embodiment, the welding wire is reversed not after the short circuit occurs but before the short circuit occurs, so the short circuit can be released early even if the current value during the short circuit period is reduced.

[0070] Furthermore, according to this embodiment, the pulse arc welding power supply sets the welding wire feed speed to the forward feed peak value during the peak period and to the reverse feed peak value during the base period, and delays the start of the peak rise period until the short circuit between the welding wire and the base metal that occurred during the base period is released. The pulse arc welding power supply according to this embodiment achieves the above-mentioned effects.

[0071] More preferably, according to this embodiment, when the welding voltage set value is smaller than the reference voltage set value, the welding wire feed speed starts to change from the reverse feed peak value to the forward feed peak value at a time point that is the first delay period after the start of the peak rise period, and starts to change from the forward feed peak value to the reverse feed peak value at a time point that is the second delay period after the start of the peak fall period. When the welding voltage set value is smaller than the reference voltage set value, the arc length is short, so a short circuit may occur during the peak period or the peak fall period. In such a case, a short circuit occurs when the welding current is large, causing a large amount of spatter and deteriorating the welding quality. In this embodiment, the feed speed starts to change from the reverse feed peak value to the forward feed peak value at a time point that is the first delay period after the start of the peak rise period, and starts to change from the forward feed peak value to the reverse feed peak value at a time point that is the second delay period after the start of the peak fall period. By providing the first delay period and the second delay period in this manner, the timing of droplet transfer can be delayed, and the occurrence of a short circuit due to droplet transfer can be led to the base period. When a short circuit occurs during the base period, the value of the welding current is small, so that the occurrence of spatter can be suppressed and the welding quality can be improved.

[0072] More preferably, according to this embodiment, when the welding voltage set value is greater than the reference voltage set value, the welding wire feed speed starts to change from the reverse feed peak value to the forward feed peak value at a time point that is the first early period before the start of the peak rise period, and starts to change from the forward feed peak value to the reverse feed peak value at a time point that is the second early period before the start of the peak fall period. When the welding voltage set value is greater than the reference voltage set value, the arc length becomes long, and a short circuit may occur just before the end of the base period. In such a case, the short circuit continues until the peak period of the next cycle, and is released while the welding current value is high, causing a lot of spatter and deteriorating welding quality. In this embodiment, the feed speed starts to change from the reverse feed peak value to the forward feed peak value at a time point that is the first early period before the start of the peak rise period, and starts to change from the forward feed peak value to the reverse feed peak value at a time point that is the second early period before the start of the peak fall period. By providing the first early period and the second early period in this way, droplet transfer can be performed early, and the occurrence of a short circuit due to droplet transfer can be led to the early period of the base period. If a short circuit occurs early in the base period, it is released during the base period, so that spatter generation can be suppressed and welding quality can be improved.

[0073] 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 base voltage set value increases. In this way, a short circuit can occur in the early period of the base period regardless of the welding voltage set value. As a result, even if the arc length is set to a short or long state depending on the welding voltage set value, the generation of spatter can be suppressed. [Explanation of symbols]

[0074] 1: welding wire, 2: base metal, 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 amplifier circuit, Ei: current error amplification signal, EV: voltage error amplifier circuit, Ev: voltage error amplification signal, FAD: feed speed average value detection circuit, Fad: feed speed average value detection signal, FAR: feed speed average value setting circuit, Far: feed speed average value 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 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 fall current, Ip: peak current, Ipr: peak current setting signal, IR: welding current setting circuit, Ir: welding current setting signal, Iu: peak rise current, Iw: welding current, MC: power control circuit, On: start signal, PS: welding power source, RC: robot control device, SD: short circuit detection circuit, Sd: short circuit Discrimination signal, SLD: long-term short circuit discrimination circuit, Sld: long-term short circuit discrimination 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: feeding speed Fall period, TFKR: Feed speed fall period setting circuit, Tfkr: Feed speed fall period setting signal, Tfu: Feed speed rise period, TFUR: Feed speed rise period setting circuit, Tfur: Feed speed rise period setting signal, Tk: Peak fall period, TKR: Peak fall period setting circuit, Tkr: Peak fall period setting signal, Tm: Timer signal, Tp: Peak period, TPR: Peak period setting circuit, Tpr: Peak period 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, WC: feed speed modulation circuit, WL: reactor, 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, 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. 1. A pulse arc welding control method for welding by controlling an arc length based on a welding voltage set value, comprising: feeding a welding wire in forward and reverse directions; supplying a peak rise current that rises from a base current value to a peak current value during a peak rise period; supplying the peak current during the peak period; supplying a peak fall current that falls from the peak current value to the base current value during a peak fall period; and supplying the base current during the base period; repeating the supply of these welding currents as one pulse period; a welding wire feed speed is set to a forward feed peak value during the peak period and to a reverse feed peak value during the base period, and a start of the peak rise period is delayed until a short circuit between the welding wire and the base metal that has occurred during the base period is released.

2. 2. The pulse arc welding control method according to claim 1, wherein the reverse feed peak value is increased when the short circuit duration is equal to or greater than a reference value.

3. 2. The pulse arc welding control method according to claim 1, wherein when the welding voltage set value is equal to a reference voltage set value, the base period is set to a reference base period, when the welding voltage set value is smaller than the reference voltage set value, the base period is made longer than the reference base period, and when the welding voltage set value is larger than the reference voltage set value, the base period is made shorter than the reference base period.

4. 4. The pulse arc welding control method according to claim 3, wherein the forward feed peak value and / or the reverse feed peak value is changed so that the average value of the feed speed becomes a predetermined value.

5. 5. The pulse arc welding control method according to claim 1, wherein the value of the base current is smaller during the short circuit period than during the arc generation period.

6. a pulse arc welding power supply that feeds a welding wire in both forward and reverse directions, passes a peak rise current that rises from a base current value to a peak current value during a peak rise period, passes the peak current during the peak period, passes a peak fall current that falls from the peak current value to the base current value during a peak fall period, and passes the base current during the base period, repeating these passes of welding current as one pulse period, and performs arc length control based on a welding voltage set value, the pulse arc welding power supply sets a feed speed of the welding wire to a forward feed peak value during the peak period and to a reverse feed peak value during the base period, and delays the start of the peak rise period until a short circuit between the welding wire and the base metal that occurs during the base period is released.

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