JP6425552B2 - Output control method of pulse arc welding - Google Patents

Description

  The present invention relates to a power control method of pulse arc welding in which a welding wire is fed and welding is performed with a welding current having a peak current in a peak period and a base current in a base period as one pulse cycle.

  A consumable electrode type pulse that generates welding arc by supplying welding current of a pulse waveform that feeds welding wire at a constant speed, and makes the pulse current with one pulse cycle the peak current in the peak period and the base current in the base period. Arc welding methods are widely used. This pulse arc welding method can efficiently perform high-quality welding with less spatter generation amount to various metal materials such as steel, stainless steel, and aluminum.

  FIG. 5 is a current-voltage waveform diagram during steady-state welding in consumable electrode type pulse arc welding. The figure (A) shows the waveform of the welding current Iw which energizes an arc, and the figure (B) shows the waveform of the welding voltage Vw applied between a welding wire and a base material. This will be described below with reference to the same figure.

  During the peak period Tp from time t1 to t2, as shown in FIG. 6A, the peak rises with a slope, and is a peak set to a steady-state peak current value that is equal to or greater than the critical value in order to form and transfer droplets. The current Ip flows, and as shown in FIG. 6B, it rises with a slope, and a peak voltage Vp proportional to the arc length is applied. During the base period Tb from time t2 to time t3, as shown in FIG. 6A, it falls with a slope, and the base current is set to a steady base current value less than the critical value so as not to form a droplet. Ib is energized, and as shown in the figure (B), it falls with a slope, and a base voltage Vb proportional to the arc length is applied. Welding is performed by repeating time t1 to t3 as one pulse cycle Tf.

  Each waveform parameter in the case where the welding wire is a metal-based cored wire with a diameter of 1.2 mm for stainless steel is, for example, as follows. The peak current Ip = 450 A, the peak period Tp = 2.0 ms including the rise, the pulse period Tf = 3.0 to 10.0 ms, the base current Ib = 50 A, the rise period and the fall period = 0.5 ms.

  During the peak period Tp, the tip of the welding wire is melted to grow a droplet, and a pinching portion is gradually formed at the top of the droplet. Then, at time t2, the base period Tb is entered, and at time t21 after the welding current Iw falls and converges to the base current Ib, the droplet shifts to the molten pool. During this transition, the droplet may be elongated and in contact with the molten pool, and a short circuit (often less than 0.2 ms) may occur. Therefore, as shown in FIG. 6B, at time t21, the welding voltage Vw becomes several volts, and a short circuit occurs. As shown in FIG. 6A, the welding current Iw increases after a predetermined time from time t21 when the short circuit occurs, and returns to the normal value at time t22 when the short circuit ends. The predetermined time is about 0.1 ms. The reason for increasing the welding current Iw is to release the short circuit early and return to the arc generation state.

  In consumable electrode type arc welding including pulse arc welding, it is important to maintain an appropriate arc length during welding in order to obtain good welding quality. This arc length control is performed as follows. The average value Vav of the welding voltage shown to the figure (B) is substantially proportional to average arc length. For this purpose, the welding voltage average value Vav is detected, and the welding voltage average value Vav is equal to the welding voltage setting value Vr (not shown) set to a value corresponding to an appropriate average arc length. The pulse period Tf (frequency modulation control) or the peak period Tp (pulse width modulation control) is changed by feedback control.

  In the frequency modulation control, the peak period Tp, the peak current Ip and the base current Ib become waveform parameters and are set to predetermined values. Then, the pulse period Tf (base period Tb) is feedback-controlled.

  In the pulse width modulation control, the peak current Ip, the pulse period Tf and the base current Ib become waveform parameters and are set to predetermined values. Then, the peak period (pulse width) Tp is feedback-controlled.

  The welding voltage average value Vav is detected by detecting the welding voltage Vw and passing it through a low pass filter (cutoff frequency of about 1 to 10 Hz).

  In each modulation control, the waveform parameter is set to an appropriate value so as to be a so-called 1 pulse period 1 droplet transition state in which one droplet moves in 1 pulse period.

  In the invention of Patent Document 1, in the pulse arc welding, the slope of the peak current is loosened in a predetermined period from the arc generation as compared with the main welding. Thereby, the arc breakage can be suppressed by suppressing the magnetic blowing at the time of the arc start.

Patent No. 3003673

  In pulse arc welding, during the transition period after arc start, the arc length suddenly and rapidly increases, and the phenomenon that the welding state becomes unstable sometimes occurs. And since the arc length becomes very long, it may lead to arc breakage or welding to the feed tip. The phenomenon that the arc length rapidly increases often occurs during the transition period after the arc start, but may also occur during the steady welding period.

  Therefore, it is an object of the present invention to provide an output control method of pulse arc welding capable of achieving a stable welding state by suppressing a phenomenon in which the arc length suddenly and rapidly increases.

In order to solve the problems described above, the invention of claim 1 is
In the power control method of pulse arc welding, a welding wire is fed, and welding is performed by applying a welding current having a peak current in a peak period and a base current in a base period as one pulse period,
When the welding voltage in the peak period becomes equal to or higher than a predetermined reference voltage value, the peak current is decreased by a predetermined decrease value, and the base current is increased by a predetermined increase value.
It is an output control method of pulse arc welding characterized by the above.

In the invention of claim 2, the decrease value is set based on a unit length resistance value of the welding wire.
It is an output control method of pulse arc welding according to claim 1 characterized by things.

The invention according to claim 3 is that, when the arc length control is frequency modulation control, the increase value does not decrease the average value of the pulse period and the peak current during a period in which the peak current is decreased. The difference between the pulse period and the average value during the period is set to be less than a predetermined value,
It is an output control method of pulse arc welding according to claim 1 or 2 characterized by things.

According to the invention of claim 4, when the arc length control is pulse width modulation control, the increase value decreases the average value of the peak period and the peak current during the period in which the peak current is being reduced. Set so that the difference with the average value of the peak periods during the non-period is less than a predetermined value,
It is an output control method of pulse arc welding according to claim 1 or 2 characterized by things.

In the invention of claim 5, the period during which the peak current is reduced is set to a predetermined period.
It is an output control method of pulse arc welding given in any 1 paragraph of Claims 1-4 characterized by the above-mentioned.

In the invention of claim 6, the period during which the peak current is reduced is set to a period until the welding voltage in the peak period falls below the reference voltage value.
It is an output control method of pulse arc welding given in any 1 paragraph of Claims 1-4 characterized by the above-mentioned.

  According to the present invention, even if a phenomenon in which the arc length becomes long rapidly occurs, the peak current value decreases early, so that the abnormal heating state can be suppressed. For this reason, in the present invention, it is possible to suppress the progress of the phenomenon in which the arc length is rapidly increased, and to quickly return the arc length to the proper state. Furthermore, in the present invention, since the average value of the pulse period or peak period is less than a predetermined value during the period during which the peak current occurs and the period during which the peak current is not reduced The welding condition can be kept good.

It is a timing chart for explaining an output control method of pulse arc welding concerning Embodiment 1 of the present invention. It is a figure which shows the relationship between reduction value (DELTA) d [A] shown on a vertical axis | shaft, and unit length resistance value Rw [m ohm / mm] of the welding wire shown on a horizontal axis. It is a block diagram of a welding power supply for enforcing the output control method of pulse arc welding concerning Embodiment 1 of the present invention. It is a block diagram of the welding power supply for enforcing the output control method of pulse arc welding concerning Embodiment 2 of the present invention. It is a general current-voltage waveform figure in consumable electrode type pulse arc welding in a prior art.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First Embodiment
The invention of the first embodiment reduces the peak current by a predetermined reduction value when the peak voltage which is the welding voltage in the peak period becomes equal to or higher than a predetermined reference voltage value, and pre-sets the base current. It is to increase by a fixed increase value. The period during which the peak current is reduced is set to a predetermined period. Since the phenomenon of the arc length rapidly increasing often occurs during the transition period after the arc start, the following description will be made during the transition period after the arc start. The same applies to the operation during the steady welding period.

  FIG. 1 is a timing chart for explaining an output control method of pulse arc welding according to a first embodiment of the present invention. The figure (A) shows the time change of welding start signal St, the figure (B) shows the time change of feed speed Fw, the figure (C) shows the time change of welding current Iw, the figure ( D) shows the time change of welding voltage Vw, and the figure (E) shows the time change of correction period signal Stk. In the figure, the description of the same operation as that of FIG. 5 described above will not be repeated. This will be described below with reference to the same figure.

  When the welding start signal St changes to High level (welding start) at time t1 as shown in (A) in the figure, the welding power source is activated, and as shown in (B) in FIG. The feed at a predetermined slow down speed is started, and a no-load voltage is applied between the welding wire 1 and the base material 2 as shown in FIG. The slow down speed is set to a slow speed of about 1 m / min.

  When the tip of welding wire 1 contacts base material 2 at time t2, arc 3 is generated after a short circuit. In response to this, as shown in FIG. 6C, during a predetermined hot start period Th of time t2 to t3, a hot start current Ih (about 500 A) of a large current value determined in advance is energized. As shown in (D) of the figure, welding voltage Vw sharply decreases to a short circuit voltage value of several volts during a short circuit from time t2, and increases to an arc voltage value of several tens of volts until time t3 when arc 3 occurs. Do. When the welding current Iw starts to be energized at time t2, as shown in FIG. 7B, the feed speed Fw is accelerated with a slope and converges to a predetermined steady feed speed Fwc at time t7. . As shown in FIG. 6E, the correction period signal Stk is at the low level, and as described later, is at the high level during the period from time t9 to time t12. A period in which the correction period signal Stk is at High level is a correction period Tk.

  When the hot start period Th ends at time t3, during a period from time t3 to t4, as shown in FIG. 6C, a predetermined steady base current Ibc is supplied, and as shown in FIG. , A steady base voltage Vbc proportional to the arc length is applied.

  During a predetermined peak period Tp from time t4 to t5, as shown in FIG. 6C, a predetermined steady-state peak current Ipc is supplied, and as shown in FIG. 6D, it is proportional to the arc length. A steady-state peak voltage Vpc is applied. At this point of time, the phenomenon that the arc length rapidly increases does not occur, so the steady-state peak voltage Vpc is less than the reference voltage value Vth indicated by the broken line. The reference voltage value Vth is preset by an experiment based on the peak voltage value when the arc length is longer than the appropriate range. That is, when the peak voltage value becomes equal to or higher than the reference voltage value Vth, it can be determined that the arc length becomes longer than the appropriate range and the phenomenon that the arc length becomes rapidly longer occurs. . During the base period Tb from time t5 to t6, the steady base current Ibc is energized as shown in FIG. 7C, and the steady base voltage Vbc is applied as shown in FIG. . As described above, the pulse period Tf (base period Tb) is feedback controlled (frequency modulation control) so that the average value of the welding voltage Vw in the pulse period Tf from time t4 to t6 is equal to the predetermined welding voltage setting signal Vr. ).

  The operation of the pulse period Tf from time t6 to t8 is similar to the operation of the pulse period Tf from time t4 to t6. At time t7 during the pulse cycle Tf from time t6 to t8, as shown in FIG. 7B, the feed speed Fw converges to the steady feed speed Fwc. The inclination period of the feed speed Fw from time t2 to t7 is about 50 ms. In the same figure, a waveform for two cycles is drawn during this inclination period, but in actuality it will be around 10 cycles.

  Since a phenomenon in which the arc length rapidly increases during peak period Tp from time t8 occurs, as shown in FIG. 7D, it exceeds the reference voltage value Vth shown by the broken line at time t9 when the peak voltage rises. Therefore, as shown in FIG. 6E, the correction period signal Stk changes to the high level at time t9. The correction period signal Stk returns to the low level at time t12 which is a predetermined period after time t9. Since the correction period signal Stk is at the high level, as shown in FIG. 7C, a predetermined correction peak current Ipk is applied, and as shown in FIG. 6D, the correction peak higher than the reference voltage value Vth. A voltage Vpk is applied. Similarly, during the base period Tb from time t10, since the correction period signal Stk is at the high level, a predetermined correction base current Ibk is supplied as shown in FIG. As shown in FIG. 5, since the arc length is long, the corrected base voltage Vbk having a value larger than the steady base voltage Vbc is applied. As described above, the pulse period Tf (base period Tb) is feedback controlled (frequency modulation control) so that the average value of the welding voltage Vw in the pulse period Tf from time t8 to t11 becomes equal to the welding voltage setting signal Vr. Be done.

  The operation of the pulse cycle Tf from time t11 to t13 is similar to the operation of the pulse cycle Tf from time t8 to t11. At time t12 in the base period Tb in the pulse period Tf from time t11 to t13, as shown in FIG. 7E, the correction period signal Stk returns to the low level because the predetermined period ends. The correction period Tk of time t9 to t12 is set to about 50 to 300 ms. In the same figure, although the waveform for two cycles is drawn in this correction period Tk, it becomes about 10 to 60 cycles in fact.

  Since the correction period signal Stk shown in FIG. 5E is at the low level from the pulse period Tf of time t13 to t15, the same operation as in the steady welding period of time t4 to t8 described above is performed. During the above peak period Tp from time t13 to t14, the steady peak current Ipc flows as shown in FIG. Since the arc length is restored to the appropriate range by current control in the correction period Tk, a steady-state peak voltage Vpc less than the reference voltage value Vth is applied, as shown in FIG. During the base period Tb from time t14 to t15, as shown in FIG. 6C, the above-mentioned steady base current Ibc is supplied, and as shown in FIG. 14D, the steady base voltage Vbc proportional to the arc length. Apply. After this, the operation of this cycle will be repeated.

  The corrected peak current Ipk is set to a value obtained by reducing the value of the steady-state peak current Ipc by a predetermined decrease value Δd. The corrected base current Ibk is set to a value obtained by increasing the value of the steady base current Ibc by a predetermined increase value Δu. The steady-state peak current Ipc is a value equal to or greater than the critical value, and is set to a range in which one pulse cycle 1 droplet transition state is achieved. The steady-state base current Ibc is a value less than the critical value, and is set to a range in which no droplet is formed during the base period Tb. The corrected peak current Ipk is a value equal to or more than the critical value, but is reduced by the decrease value Δd, so the multiple pulse period 1 droplet transition state is often reached. Although the corrected base current Ibk is set to a value less than the critical value, since it is increased by the increase value Δu, a small number of droplets are often formed during the base period Tb.

  The arc condition was observed using a high-speed camera when a phenomenon in which the arc length increased rapidly during the transition period after the arc start occurred. When the arc length is in the normal state, the arc 3 is generated from the droplet formed at the lower end of the wire protrusion. The phenomenon in which the arc length is rapidly increased was determined that the wire 3 was melted at an intermediate position of the wire protruding portion and the arc 3 was generated from the melted portion. The reason for melting at the middle position of the wire protrusion was that the wire 1 at the melting position was damaged, and therefore it was determined that abnormal heating was caused and melting occurred. The reason why the damage occurs to the welding wire 1 is that when the feeding speed Fw is reduced at the end of the previous welding and the feeding is stopped, friction is generated at a portion where the inner surface of the feed tip contacts the welding wire 1 to supply power. This is because the welding wire 1 may be damaged by arcing or the like. In addition, when the feed speed Fw is accelerated at the time of arc start, the welding wire 1 may be damaged in the same manner. And in order for the location of the welding wire 1 damaged within the feed tip to be fed to the intermediate position of the wire protrusion, it takes about 100 to 500 ms after the arc start. For this reason, the phenomenon in which the arc length increases rapidly tends to occur in the range of about 100 to 500 ms after the arc start. However, even if the welding wire 1 is damaged, if the resistance value per unit length of the welding wire 1 (hereinafter referred to as unit length resistance value) is small, abnormal heating hardly occurs, so the arc length is rapid. The phenomenon of becoming longer becomes less likely to occur. If the welding wire 1 is damaged during the steady welding period, a phenomenon in which the arc length rapidly increases may occur. When acceleration and deceleration of the feed speed Fw are repeated during the steady welding period, the occurrence frequency of the phenomenon becomes high.

  Therefore, in order to suppress the occurrence of the phenomenon in which the arc length is rapidly increased, it is possible to prevent damage to the welding wire 1 in the feed tip or to prevent abnormal heating. Since it is difficult to prevent damage to the welding wire 1, measures are taken to prevent abnormal heating. Abnormal heating occurs when a large current value peak current is applied to the damaged portion of the welding wire 1. For this reason, the occurrence of the phenomenon in which the arc length rapidly increases is determined early by the peak voltage value becoming equal to or higher than the reference voltage value Vth, and the steady-state peak current Ipc decreases during the correction period Tk from the determination time point. Abnormal heating is prevented by supplying the corrected peak current Ipk reduced by the value Δd. However, as the correction peak current Ipk is closer to the steady-state peak current Ipc, that is, as the decrease value Δd is smaller, the droplet transfer state becomes better. In other words, when the decrease value Δd becomes large, the droplet transfer state becomes a little worse, so that the spatter increases. Therefore, it is desirable to set the decrease value Δd to the minimum value within a range in which the phenomenon in which the arc length increases rapidly does not progress. Abnormal heating is more likely to occur as the unit length resistance value of the welding wire is larger. For this purpose, it is desirable to change the appropriate value of the reduction value Δd in accordance with the unit length resistance value of the welding wire 1. This relationship will be described later with reference to FIG.

  Since the corrected peak current Ipk is smaller than the steady-state peak current Ipc, the average value of the pulse period Tf during the correction period Tk is longer than the mean value of the pulse period Tf during the steady-state welding period. As the pulse period Tf becomes longer, the welding state becomes somewhat unstable. The pulse period Tf changes because of the above-described frequency modulation control. In order to make the average value of the pulse period Tf in the correction period Tk equal to the average value of the pulse period Tf in the steady welding period, the corrected base current Ibk should be larger than the steady base current Ibc. For this purpose, the corrected base current Ibk is set to a value obtained by increasing the steady base current Ibc by the increase value Δu. Therefore, the increase value Δu is set such that the difference between the average value of the pulse period Tf during the correction period Tk and the average value of the pulse period Tf during the steady welding period is less than a predetermined value after the correction peak current Ipk is set. Set to The predetermined value is about 10%.

  When the arc length control is pulse width modulation control, the pulse period Tf has a fixed value, and the peak period (pulse width) Tp is feedback controlled. For this purpose, the correction base current Ibk (increase value Δu) may be set so that the difference between the average values of the peak periods Tp between the correction period Tk and the steady welding period is less than a predetermined value.

  FIG. 2 is a view showing the relationship between the decrease value Δd [A] shown on the vertical axis and the unit length resistance value Rw [mΩ / mm] of the welding wire shown on the horizontal axis.

  As shown in the figure, in the range of Rw <0.03, Δd = 0. This is because, since the unit length resistance value Rw of the welding wire is small, abnormal heating does not occur even if the welding wire is damaged. When the material of the welding wire is aluminum, it belongs to this range.

  In the range of Rw ≧ 0.03, it is a straight line rising to the right. That is, as the unit length resistance value Rw increases, the decrease value Δd also increases. In the case of a mild steel solid wire with a diameter of 1.2 mm, Rw = 0.09 and Δd = 10A. In the case of a soft steel solid wire with a diameter of 0.9 mm, Rw = 0.16, and Δd = 20A. In the case of a stainless steel solid wire with a diameter of 1.2 mm, Rw = 0.65, and Δd = 80A. In the case of a metal-based coret wire of stainless steel having a diameter of 1.2 mm, Rw = 0.85 and Δd = 100A.

  FIG. 3 is a block diagram of a welding power source for implementing the power control method of pulse arc welding according to the first embodiment of the present invention described above with reference to FIG. Each block will be described below with reference to the figure.

  Power supply main circuit PM receives a commercial power supply (not shown) such as three-phase 200 V, performs output control by inverter control according to a drive signal Dv described later, and outputs welding current Iw and welding voltage Vw. Although not shown, the power supply main circuit PM is a primary rectifier for rectifying a commercial power supply, a capacitor for smoothing rectified DC, and an inverter circuit for converting the smoothed DC into high frequency AC according to the drive signal Dv. The high frequency transformer which steps down high frequency alternating current to a voltage value suitable for arc welding, the secondary rectifier which rectifies the stepped down high frequency alternating current, and the reactor which smoothes the rectified direct current are provided.

  The welding wire 1 is wound around a wire reel 1a. The welding wire 1 is fed through the welding torch 4 by the rotation of the feed roll 5 coupled to the wire feed motor WM, and an arc 3 is generated between the welding wire 1 and the base material 2 to perform welding. A welding current Iw is energized in the arc 3, and a welding voltage Vw is applied between a feeding tip (not shown) in the welding torch 4 and the base material 2.

  The welding voltage detection circuit VD detects the welding voltage Vw and outputs a welding voltage detection signal Vd. Welding voltage average value calculation circuit VAV takes this welding voltage detection signal Vd as an input, passes it through a low pass filter, and averages it to output welding voltage average value signal Vav. Welding voltage setting circuit VR outputs a predetermined welding voltage setting signal Vr. The voltage error amplification circuit EV amplifies an error between the welding voltage setting signal Vr and the welding voltage average value signal Vav to output a voltage error amplification signal Ev.

  The voltage / frequency conversion circuit VF receives the voltage error amplification signal Ev as an input, and outputs a pulse cycle signal Tf having a frequency corresponding to the value of the voltage error amplification signal Ev. The pulse cycle signal Tf is a signal that goes high for a short time every pulse cycle.

  The peak period setting circuit TPR outputs a predetermined peak period setting signal Tpr. The timer circuit TM receives the above peak period setting signal Tpr and the above pulse cycle signal Tf as input, and whenever the pulse cycle signal Tf changes to high level, a timer signal which becomes high level only during a period determined by the peak period setting signal Tpr. Output Tm. Therefore, when the timer signal Tm is at the high level, it is a peak period, and when it is at the low level, it is a base period.

  The welding start circuit ST outputs a welding start signal St which becomes High level when the welding power source is started. The welding start circuit ST corresponds to a start switch of the welding torch 4, a PLC for controlling the welding process, a robot control device, and the like.

  The welding current detection circuit ID detects the above-mentioned welding current Iw and outputs a welding current detection signal Id. The current conduction determination circuit CD receives the above-described welding current detection signal Id, and when the value is equal to or more than a threshold (about 10 A), it determines that the welding current Iw is flowing and conducts current at high level. The discrimination signal Cd is output.

  The hot start period circuit STH receives the current conduction determination signal Cd as an input and starts the hot start period signal Sth which becomes high level during a predetermined hot start period Th from the time when the current conduction determination signal Cd changes to high level. Output. The hot start current setting circuit IHR outputs a predetermined hot start current setting signal Ihr.

  The welding wire selection circuit WS selects the combination of the material and diameter of the welding wire to be used, and outputs a welding wire selection signal Ws. For example, when selecting a mild steel solid wire with a diameter of 1.2 mm, Ws = 1, when selecting a soft steel solid wire with a diameter of 0.9 mm, Ws = 2, and when selecting a stainless steel metal cored wire with a diameter of 1.2 mm, Ws = 3 It becomes.

  Unit length resistance value setting circuit RWR receives the above-mentioned welding wire selection signal Ws, reads the unit length resistance value of the welding wire corresponding to welding wire selection signal Ws from the built-in database, and performs the unit length resistance value. The setting signal Rwr is output.

  The reduction value setting circuit ΔDR receives the unit length resistance value setting signal Rwr as described above, and outputs a reduction value setting signal Δdr calculated based on the relational expression described above with reference to FIG.

  Welding current average value setting circuit IR outputs a predetermined welding current average value setting signal Ir.

  The steady-state peak current setting circuit IPCR outputs a predetermined steady-state peak current setting signal Ipcr. Steady-state base current setting circuit IBCR outputs a predetermined steady-state base current setting signal Ibcr.

  The corrected peak current setting circuit IPKR receives the steady peak current setting signal Ipcr and the decrement value setting signal Δdr as described above, subtracts the decrement value setting signal Δdr from the steady peak current setting signal Ipcr, and corrects the corrected peak current setting signal. Output as Ipkr.

  The steady welding period pulse period calculation circuit TFC receives the welding current average value setting signal Ir, the peak period setting signal Tpr, the steady peak current setting signal Ipcr, and the steady base current setting signal Ibcr as inputs. = (Tpr · (Ipcr-Ibcr)) / (Ir-Ibcr) is calculated, and a steady welding period pulse period signal Tfc is output.

  The correction base current setting circuit IBKR receives the welding current average value setting signal Ir, the steady welding period pulse period signal Tfc, the peak period setting signal Tpr, and the corrected peak current setting signal Ipkr as inputs, Ibkr = (Tfc.Ir-Tpr.Ipkr) / (Tfc-Tpr) is calculated and output as the corrected base current setting signal Ibkr.

  The correction period circuit STK receives the welding voltage detection signal Vd described above, the hot start period signal Sth described above and the timer signal Tm described above, and after the hot start period signal Sth changes from high level to low level (hot start period After the end of Th), when the value of welding voltage detection signal Vd when timer signal Tm is at High level (peak period) becomes equal to or higher than a predetermined reference voltage value Vth, it is set to High level, and then predetermined period The correction period signal Stk, which is later reset to the low level, is output.

  The peak current setting circuit IPR receives the above correction period signal Stk, the above correction peak current setting signal Ipkr and the above steady peak current setting signal Ipcr as input, and corrects it when the correction period signal Stk is High level (correction period) The peak current setting signal Ipkr is output as a peak current setting signal Ipr, and when Stk = Low level (stationary welding period), the steady peak current setting signal Ipcr is output as a peak current setting signal Ipr.

  The base current setting circuit IBR receives the above correction period signal Stk, the above correction base current setting signal Ibkr and the above steady base current setting signal Ibcr as input, and corrects it when the correction period signal Stk is High level (correction period) The base current setting signal Ibkr is output as the base current setting signal Ibr, and when Stk = Low level (stationary welding period), the steady base current setting signal Ibcr is output as the base current setting signal Ibr.

  The switching circuit SW receives the hot start period signal Sth, the timer signal Tm, the hot start current setting signal Ihr, the peak current setting signal Ipr and the base current setting signal Ibr as input, and performs a hot start period. When the signal Sth is high level, the hot start current setting signal Ihr is output as the current control setting signal Icr, and when the hot start period signal Sth is low level and the timer signal Tm is high level, the peak current setting signal Ipr is output as the current control setting signal Icr, and when the hot start period signal Sth is at the low level and the timer signal Tm is at the low level, the base current setting signal Ibr is output as the current control setting signal Icr.

  The current error amplification circuit EI amplifies an error between the current control setting signal Icr and the welding current detection signal Id, and outputs a current error amplification signal Ei. Drive circuit DV receives this current error amplification signal Ei and the above-mentioned welding start signal St, and when the welding start signal St is at a high level, performs PWM control to drive the inverter circuit of the above-mentioned power supply main circuit PM. And outputs a drive signal Dv.

Feed speed setting circuit FR receives the above-mentioned welding current average value setting signal Ir, and corresponds to the value of welding current average value setting signal Ir according to the relation between the welding current average value and the feeding speed built in advance. The feed speed setting signal Fr is calculated and output.

  The feed control circuit FC receives the feed speed setting signal Fr, the welding start signal St, and the current conduction discrimination signal Cd as inputs, and at a predetermined slow-down speed when the welding start signal St becomes High level. A feed control signal Fc for feeding the welding wire 1 is output, and thereafter, when the current conduction determination signal Cd changes to a high level, the feed speed set by the feed speed setting signal Fr is accelerated by a predetermined inclination and is determined. A feed control signal Fc for feeding the welding wire 1 by Fw is outputted to the above-mentioned wire feed motor WM.

  This figure shows the case where the method of arc length control is frequency modulation control. In the case of pulse width modulation control, the pulse cycle signal Tf may be set to a predetermined value, and the peak period setting signal Tpr may be feedback controlled based on the voltage error amplification signal Ev. At this time, the corrected base current setting signal Ibkr may be set such that the difference between the average value of peak periods in the correction period and the average value of peak periods in the steady welding period is less than a predetermined value.

  According to the first embodiment described above, when the peak voltage which is the welding voltage in the peak period becomes equal to or higher than a predetermined reference voltage value, the peak current is decreased by a predetermined decrease value, and the base current Is increased by a predetermined increase value. The reduction value is set based on the unit length resistance value of the welding wire. When the arc length control is frequency modulation control, the increase value is set such that the difference between the average value of the pulse periods during the correction period and the average value of the pulse periods during the steady welding period is less than a predetermined value. . When the arc length control is pulse width modulation control, the increase value is set such that the difference between the average value of peak periods in the correction period and the average value of peak periods in the steady welding period is less than a predetermined value. Ru. The correction period is set to a predetermined period. As a result, in the present embodiment, even if the phenomenon in which the arc length becomes long rapidly occurs, the peak current value decreases early, so that the abnormal heating state can be suppressed. For this reason, in the present embodiment, it is possible to suppress the progress of the phenomenon in which the arc length is rapidly increased, and to quickly return the arc length to the appropriate state. Furthermore, in the present embodiment, the average value of the pulse period or peak period is a predetermined value during the period during which the peak current is reduced (correction period) and during the period when the peak current is not decreased (steady welding period). Since the difference is less than, it is possible to keep the welding condition well during both periods.

Second Embodiment
In the invention of the second embodiment, the correction period Tk is set to a period until the peak voltage becomes lower than the reference voltage value.

  FIG. 4 is a block diagram of a welding power source for implementing the power control method of pulse arc welding according to the second embodiment. This figure corresponds to FIG. 3 described above. The same reference numerals are given to the same blocks, and the description thereof will not be repeated. This figure is obtained by replacing the correction period circuit STK of FIG. 3 with a second correction period circuit STK2. Hereinafter, this block will be described with reference to the figure.

  The second correction period circuit STK2 receives the welding voltage detection signal Vd, the hot start period signal Sth and the timer signal Tm, and after the hot start period signal Sth changes from high level to low level (hot After the end of the start period Th), when the value of the welding voltage detection signal Vd when the timer signal Tm is at the high level (peak period) becomes equal to or higher than a predetermined reference voltage value Vth, it is set to the high level When the value of the welding voltage detection signal Vd when the timer signal Tm is at the high level becomes less than the reference voltage value Vth, the correction period signal Stk which is reset to the low level is output.

  The timing chart for explaining the output control method of pulse arc welding according to the second embodiment of the present invention is the same as FIG. 1 described above, and therefore the description will not be repeated. However, only the timing at which the correction period signal Stk changes from the high level to the low level shown in FIG. That is, the end timing of the correction period Tk is different. In the first embodiment, the end timing is reached when a predetermined period has elapsed from the start of the correction period Tk. On the other hand, in the second embodiment, the time when the peak voltage value is less than the reference voltage value Vth is the end timing.

  According to the second embodiment described above, the period during which the peak current is reduced (correction period) is set to a period until the welding voltage (peak voltage) in the peak period becomes lower than the reference voltage value. Thus, in addition to the effects of the first embodiment, the following effects can be obtained. That is, in the present embodiment, since the correction period can be automatically set to the optimum value, it is not necessary to conduct an experiment to set the correction period to the appropriate value for each of various welding conditions. Because of this, production preparation becomes efficient. Furthermore, since the correction period is always set to the optimum value, it is possible to rapidly converge to the steady welding state.

DESCRIPTION OF SYMBOLS 1 welding wire 2 base material 3 arc 4 welding torch 5 feed roll CD current conduction discrimination circuit Cd current conduction discrimination signal DV drive circuit Dv drive signal EI current error amplification circuit Ei current error amplification signal EV voltage error amplification circuit Ev voltage error amplification Signal FC Feed control circuit Fc Feed control signal FR Feed speed setting circuit Fr Feed speed setting signal Fw Feed speed Fwc Stationary feed speed Ib Base current Ibc Stationary base current IBCR Stationary base current setting circuit Ibcr Stationary base current setting Signal Ibk Correction base current IBKR Correction base current setting circuit Ibkr Correction base current setting signal IBR Base current setting circuit Ibr Base current setting signal Icr Current control setting signal ID Welding current detection circuit Id Welding current detection signal Ih Hot start current IHR Hot start current Setting circuit Ihr Hot start current setting signal I p peak current Ipc steady peak current IPCR steady peak current setting circuit Ipcr steady peak current setting signal Ipk corrected peak current IPKR corrected peak current setting circuit Ipkr corrected peak current setting signal IPR peak current setting circuit Ipr peak current setting signal IR welding current average value Setting circuit Ir Welding current average value setting signal Iw Welding current PM Power supply main circuit Rw Unit length resistance value RWR Unit length resistance value setting circuit Rwr Unit length resistance value setting signal ST Welding start circuit St Welding start signal STH Hot start period circuit Sth hot Start period signal STK Correction period circuit Stk Correction period signal STK2 Second correction period circuit SW Switching circuit Tb Base period Tf Pulse period (signal)
TFC steady welding period pulse period calculation circuit Tfc steady welding period pulse period signal Th hot start period Tk correction period TM timer circuit Tm timer signal Tp peak period TPR peak period setting circuit Tpr peak period setting signal VAV welding voltage average value calculation circuit Vav welding Voltage average value (signal)
Vb base voltage Vbc steady base voltage Vbk correction base voltage VD welding voltage detection circuit Vd welding voltage detection signal VF voltage / frequency conversion circuit Vp peak voltage Vpc steady peak voltage Vpk correction peak voltage VR welding voltage setting circuit Vr welding voltage setting signal Vth reference Voltage value Vw Welding voltage WM Wire feeding motor WS Welding wire selection circuit Ws Welding wire selection signal Δd Decrease value ΔDR Decrease value setting circuit Δdr Decrease value setting signal Δu Increase value

Claims (6)

In the power control method of pulse arc welding, a welding wire is fed, and welding is performed by applying a welding current having a peak current in a peak period and a base current in a base period as one pulse period,
When the welding voltage in the peak period becomes equal to or higher than a predetermined reference voltage value, the peak current is decreased by a predetermined decrease value, and the base current is increased by a predetermined increase value.
An output control method of pulse arc welding characterized in that. The decrease value is set based on a unit length resistance value of the welding wire.
The power control method of pulse arc welding according to claim 1, characterized in that: When the arc length control is frequency modulation control, the increase value is an average value of the pulse period during the period during which the peak current is reduced and the pulse period during the period during which the peak current is not reduced. The difference from the average value is set to be less than a predetermined value,
The power control method of pulse arc welding according to claim 1 or 2, characterized in that: When the arc length control is pulse width modulation control, the increase value is an average value of the peak period during the period during which the peak current is reduced and the peak period during the period when the peak current is not reduced. Set so that the difference with the average value of is less than a predetermined value,
The power control method of pulse arc welding according to claim 1 or 2, characterized in that: The period during which the peak current is reduced is set to a predetermined period,
The power control method of pulse arc welding according to any one of claims 1 to 4, characterized in that: The period during which the peak current is reduced is set to a period until the welding voltage during the peak period falls below the reference voltage value.
The power control method of pulse arc welding according to any one of claims 1 to 4, characterized in that:

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