JPH0452076A - Pulse arc welding method and pulse arc welding equipment using this method - Google Patents

Abstract

PURPOSE:To improve stability of the welding average voltage and to perform welding with the stabilized arc length by controlling a base current application period so that the welding average voltage is perfectly coincident with a reference value. CONSTITUTION:(1) When a peak current application signal is outputted from a current application changeover part 3 according to a base current application completion signal outputted from a base period control means 2, a welding voltage error integration circuit 20 compares the detected welding voltage E with the welding average voltage reference value set by a welding voltage setting part 4 to start integration of a differential signal. A zero crossing detection circuit 21 (voltage integration level discrimination part monitors an integration output level of the welding voltage error integration circuit 20 and when an integration output level of the differential signal extending from the peak current application starting time to the base current applying time attains a zero level (below), the base current application completion signal is outputted to the current application changeover part 3 which holds and outputs the peak current application signal and the operation of (1) is again resumed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a pulsed arc welding method and a pulsed arc welding apparatus using this method.

[Prior Art] In this type of pulse arc welding, a peak current Ip and a base current 1b necessary for transfer of droplets are alternately applied to the welding wire, and the application of the peak current Ip melts the welding wire with a pinch effect. Welding is performed by separating droplets, but since there are many factors to be set, in general, welding average current 1a (wire feeding speed), peak welding current 1a (wire feeding speed), peak shedding heel lp and its energization are Period tp, base tff
By setting the welding average voltage Eafe and variably controlling the energization period T (for energization since the peak current energization period tp is set), variable control of IJI T allows the base current energization period tb to be varied. It is customary to control the arc voltage so that the welding average voltage Ea (corresponding to control) is at a specified level.

However, in this method, when the peak current is variably set according to various welding conditions depending on the welding wire and the welding base material, the peak current is changed each time. The distribution period tp has to be readjusted, which is difficult and time-consuming, so improvements have been desired.

Therefore, in the previous application (filed on June 8, 1990), the inventor proposed that when the peak current is set variably, 1 pulse 1
A novel pulsed arc welding method was proposed in which the peak current application period suitable for droplet transfer was automatically controlled, and the present invention is a further improvement on that earlier application.

[Problems to be Solved by the Invention] That is, the present invention makes the peak current variable and automatically controls the optimum peak current energization period for transitioning to one pulse 12a according to the set peak current. The purpose of this research is to provide a welding method that allows detailed control according to the welding conditions.
The improvement compared to the previously filed invention is that the welding average voltage is automatically controlled to a stable and predetermined value by eliminating control time delays and unstable elements in the control system during the base current energization period. It is in.

Moreover, the present invention proposed at the same time aims to provide a pulse arc welding device that realizes this welding method.

[Means for Solving the Problems] In order to achieve the above object, the method of the present invention according to claim 1 proposes to control the peak current application period by adjusting the detected welding current to the detected welding current when the base current is applied. Integrate after performing predetermined arithmetic processing, and integrate after performing predetermined arithmetic processing different from the arithmetic processing during base current energization on the detected welding during subsequent peak current energization,
When the sum of these integral levels reaches a predetermined level, the peak current is stopped and switched to the base current, while the base current is turned on so that the welding average voltage matches the welding average voltage reference value. In order to control the period, the welding voltage detected from the start of the peak current application is compared with a predetermined welding average voltage reference value, and the integration of the difference is started, and when the base current is applied subsequently, this integral output is When the level matches the level at the start of integration, the base current is stopped and switched to the peak current, thereby alternately switching between the peak current and the base current.

The apparatus of the present invention according to claim 2 is characterized in that, in order to control the peak current energization period, the detected welding current is subjected to predetermined arithmetic processing at the base current energization time and the peak current energization time, respectively. an arithmetic circuit that performs the arithmetic processing; a current integrator circuit that integrates the arithmetic-processed signal output from the arithmetic circuit; peak period control means comprising a current integration level determination unit that outputs a current energization end signal and resets the current integration circuit; and a base current energization period so that the welding average voltage matches the welding average voltage reference value. In order to control
a welding voltage error integration circuit that compares the welding voltage detected from the start of the peak current application to the base current application with a predetermined welding average voltage reference value and integrates the difference; and the welding voltage error integration circuit. The base period control means includes a voltage integral level determination section that outputs a base current energization end signal when the integral output level of the base current supply terminal matches the level at the start of the integration.

As an example of such a base period control means in the present invention, in a welding voltage error integration circuit, the welding voltage detected from the start of peak current application is compared with the welding average voltage reference value, and the integral of the difference is calculated from the zero level. When the integrated output level reaches zero level during base current energization, the voltage is integrated by the zero cross detection circuit, and the base current energization is determined by the discrimination section 1.
An example is a configuration that outputs No. 8.

[Function] In the present invention according to claim 1, when the base current is applied,
The detected welding current (instantaneous value of the base current) is subjected to predetermined arithmetic processing and then integrated, and when the subsequent peak current is applied, the detected welding current (instantaneous value of the peak current) is subjected to the arithmetic processing that is applied when the base current is applied. is integrated after performing different predetermined arithmetic processing, and when the sum of these integral levels reaches a predetermined level, the peak current is stopped and switched to the base current, and by kneading, the peak current is Automatically controls the energization period.

On the other hand, the welding voltage detected from the start of the peak current application is compared with a predetermined welding average voltage reference value and the integration of the difference is started, and when the base current is applied subsequently, this integrated output level is set at the start of the product 9J. When it matches the level of the welding average voltage, the base current is stopped and the peak current is switched to the peak current, thereby automatically controlling the base current application period so that the +8 contact average voltage matches the welding average voltage reference value. As a result, welding is performed by alternately switching between the peak current and the base current.

In the apparatus of the present invention as set forth in claim 2, in the peak period control means, the welding current (instantaneous value of the base current) detected from the start of base current energization is subjected to predetermined arithmetic processing in the arithmetic circuit, and then the current integrating circuit The welding current (instantaneous value of the peak current) detected during subsequent peak current application
After performing predetermined calculation processing (different from the calculation processing when the base current is applied) in the calculation circuit, it is integrated in the current integration circuit, and the sum of these integration levels in the current integration circuit reaches a predetermined level. When this happens, a peak current energization end signal is output from the current integration level determination section to switch to base current energization and reset the current integration circuit, thereby controlling the peak current energization period.

On the other hand, the base period control means compares the welding voltage (instantaneous values of peak voltage and base voltage) detected from the start of peak current application with a predetermined welding average voltage reference value in a welding voltage error integration circuit. Integration of the difference is started, and when the integral output level matches the level at the start of the integration during the subsequent base current energization, a base current energization end signal is output from the voltage integration level determination section to switch to peak current energization, Thereby, the base current energization period is controlled so that the welding average voltage matches the welding average voltage reference value.

[Example] The present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the configuration of the main parts of a welding apparatus for carrying out the pulse arc welding method of the present invention as set forth in claim 1.

In the present invention, the peak electric current m I p can be variably set manually, and at the same time, if the reference values of the welding average current, base current, and welding average voltage are each manually set,
While automatically controlling the base current energization period tb so that the welding average voltage Ea matches the welding average voltage reference value Er,
This is to control the optimum peak current application period tp for slowing down droplet transfer with one pulse.

In FIG. 1, 1 is a peak period control means for controlling the peak current energization period tp, 2 is a base period control means for controlling the base current energization interval tb, and 3 is a base current energization signal or a peak current energization signal. The energization switching section switches and holds and outputs the signal, 4 is the welding average voltage reference value E
This is a welding voltage setting section that sets r.

Note that the diagram omits a current control means for controlling the welding current in response to a peak current energization signal or a base current energization signal output from the energization switching unit 3 (described later), and this current control means Peak current 1 set by
Negative feedback control is performed so that p or base current Ib is stably energized.

The peak period control means 1 outputs a timing signal to end the energization of the peak current 1p, and for this purpose, the welding current 1 (-\ - The instantaneous value of the welding current I (peak current 1p) is applied to the instantaneous value of the base current 1b) (calculation of raising the base current 1b to the 8th power). ) on the instantaneous value of (calculation of multiplying peak current rp to the power of )
A current integrator circuit 11 integrates the arithmetic processing result output from the iP circuit 10, and peak current energization ends when the integrated value of the current integrator circuit 11 reaches a predetermined level. It is provided with a current integration level determination section 12 that outputs a signal, resets the current integration circuit 11, integrates it, and clears the error.

On the other hand, the base period control means 2 uses the instantaneous value of the welding voltage E (peak voltage Ep) between the welding wire and the welding base material from the start of peak current application to the welding average voltage standard set by the welding voltage setting section 4. Integration of the difference signal is started by comparing it with the value Er, and the instantaneous value of the welding voltage E (base voltage) is similarly set as the welding average voltage reference 1 during subsequent mousse current application.
The welding voltage error integration circuit 20 that compares the direct Er and integrates the difference signal, and the integral output level of the welding voltage error integration circuit 20 reach the peak current! A voltage integral level determination unit 21 is provided which outputs a base current energization end signal when the output level matches the output level at the start. In addition, in this configuration,
The welding voltage error integration circuit 20 integrates the difference signal from zero level from the start of peak current energization to the time of base current energization, and when this integrated output level reaches zero level (below), the zero cross detection circuit A voltage integral level determination unit 21 (hereinafter referred to as a zero-cross detection circuit) comprises a voltage integral level determination unit 21 (hereinafter referred to as a zero-cross detection circuit), and outputs a base current energization end signal.

That is, the base period control means 2 controls the peak voltage Ep during the peak current energization period tp and the welding average voltage reference f.
The integral level of the difference from iEr is the base current conduction period t
When the base voltage Eb at b and the welding average voltage reference value Er match the integral level of the difference, the base current Ib is stopped and the peak current Ip is switched to the peak current Ip, so the welding average voltage Ea The base current flow MLu is made to completely match the welding average voltage reference value Er.
The distances t and b between M are controlled, and since it is not a negative feedback control system, no control time delay or hunting occurs.

The welding method of the present invention implemented with such a configuration will be explained with reference to the waveform diagrams of FIGS. 2(a) to 2(i). Note that corresponding parts in FIG. 1 are designated with corresponding symbols (a) to (i).

Depending on the welding conditions, welding average current 1a, peak current Ip
, base current Ib and welding average voltage Ea are set.

■When a base current energization signal is output from the energization switching section 3 in response to the peak current energization end signal output from the peak period control means 1, the arithmetic circuit 10 of the peak period control means 1
The detected welding current I (base current 1b (instantaneous (f
fi)) is subjected to predetermined calculation processing (calculation of raising the base current 1b to the 8th power) and outputted to the current integration circuit 11, and the current integration circuit 11 integrates the signal subjected to this calculation processing.

■Subsequently, when a peak current energization signal is output from the energization switching unit 3 in response to a base current energization end signal output from the base period control means 2, the arithmetic circuit 10 outputs the detected welding current I (peak current 1p (instantaneous value)) is subjected to a predetermined calculation process (calculation of multiplying the peak current by 1 pfeA) and output to the current integration circuit 11, which integrates the signal subjected to this calculation process.

■The current integral level determination unit 12 monitors the integral output level of the current integrating circuit 11, and when this level reaches a predetermined level L, it sends a peak current energization end signal to the energization switching unit 3. At the same time, the current integration circuit 11 is reset to clear the integration level.

(2) Upon receiving the peak current energization end signal, the energization switching unit 3 stops outputting the peak current energization signal, and instead holds and outputs the base current energization signal. As a result, the arithmetic circuit 1
The arithmetic multiplier of 0 is switched to B and the operation returns to (2) again.

The peak period control means 1 outputs a peak current energization end signal by repeating the operations (1) to (2) above.

On the other hand, the base period control means 2 performs the following operation.

■When a peak current energization signal is output from the energization switching unit 3 in response to the base current energization end signal output from the base period control means 2, the welding voltage error integration circuit 20 outputs the detected welding voltage E (peak voltage Ep (instantaneous value of ) with the welding average voltage reference value Er set by the welding voltage setting section 4, and the integration of the difference signal is started.

■Subsequently, when the base current energization signal is output from the energization switching section 3 in response to the peak current energization end signal output from the peak period control means 1, the welding voltage error integration circuit 2
0, the detected welding voltage E (instantaneous value of the base voltage Eb) is compared with the welding average voltage reference value Er set by the welding voltage setting section 4, and the difference signal is integrated.

On the other hand, the zero cross detection circuit 21 monitors the integral output level of the welding voltage error integration circuit 20, and when the integral output level of the differential signal from the start of peak current application to the time of mousse current application reaches zero level (below), Energization switching section 3
The base current energization completion signal is outputted at , and the energization switching section 3 holds and outputs the peak current energization signal and returns to the operation of (2).

The base period control means 2 outputs a base current energization end signal by repeatedly performing the operations (1) to (4) above.

That is, the peak period control means 1 controls the peak current 1p.
The base period control means 2 outputs a timing signal to end the energization of the base current mIb, and the energization switching unit 3 receives these timing signals and starts the base current energization. A signal or a peak current energization signal is held and outputted, and the base current FCIb and the peak current II) are alternately switched for energization.

FIGS. 3(a) to 3(d) show waveforms for explaining the operating principles of the peak period control means 1 and the base period control means 2. FIG.

The base period control means 2 is shown in FIGS. 3(c) and (d).
As shown in Peak! The difference between the peak voltage Ep and the welding average voltage reference value Er (E
p-Er) is integrated from the zero level (corresponding to the shaded area α in the figure (C)), the integral output level rises with a slope corresponding to the difference, and subsequently, when the mousse current is applied, the base voltage Eb and Difference from welding average voltage reference value Er (Eb-E
r) is integrated (corresponding to the shaded area β in FIG. 3(c)), and the integrated output level decreases with a slope corresponding to the difference. Then, when the integral output level reaches zero level (α=β), the supply of base current Ib is terminated.

Therefore, according to this control, even if, for example, the welding average voltage Ea is set low and a short circuit occurs during droplet detachment during the base current energization period tb (see Fig. 3 (C)), the welding voltage decreases. Then, the integrated output of the welding voltage error integration circuit 20 decreases steeply, and the base current energization period tb is automatically reduced by tbl, so that control is performed so that the welding average voltage Ea matches the welding average voltage reference value Er. It will be done. Also, the arc length increases during welding and the base voltage Eb decreases to Eb
Even if the welding voltage error integration times Vs20
The decline in the integrated output becomes gradual, and it becomes possible to automatically increase the base current energization period to tb2 and make the welding average voltage Ea match the welding average voltage reference value Er.

Furthermore, welding voltage E (peak voltage Ep and base voltage Eb) may vary due to transient fluctuation factors during welding other than those mentioned above.
Even if the welding average voltage Ea fluctuates, control is performed so that the welding average voltage Ea completely matches the welding average voltage reference value Er by controlling the base current energization period tb.

On the other hand, in the peak period control means 1, as shown in FIGS.
As shown in , a short circuit occurs when the droplet is detached during the base current conduction period tb, and the base current conduction period becomes tbl.
When the base current Ib is calculated and the integral output level is low, the calculation process of the peak current Ip and the time required for the integral level to reach the predetermined value are increased.
As a result, the peak current energization period tp is increased by tpl, and control is performed to ensure the optimum energization energy for droplet detachment. Further, when the base voltage Eb increases due to an increase in the arc length, the base current energization period is increased to t,b2 by the control of the base period control means 2, and the output level is adjusted by the calculation processing and integration of the base current 1b. increases, so the calculation process for the peak current 1p and the time for the integral ratio KARE to reach a predetermined value are reduced, and as a result, the peak current energization period tp is reduced to tp2, and the energization energy is controlled to the optimum value. There is.

In this way, the base period control means 2 is configured to handle cases where the welding average voltage Ea is set low and a short circuit occurs during the current flow period tb of the base 11t, or when the base voltage Eb increases as the arc length increases. Even if the welding average voltage Ea
It is possible to control the base current conduction period tb so that it completely matches the welding average voltage reference value Er, and since it is not a negative feedback control system, there is no control time delay or hunting, and the welding average voltage can significantly improve the stability of

The other peak period control means 1 is such that even when the peak flow fp or the base flow 1b is variably set, the total amount of energy applied to the welding wire is optimal for one pulse and one droplet transfer. As soon as the peak current 1p reaches this value, the application of the peak current 1p is stopped and the current is switched to the current 1b.
It becomes possible to effectively prevent the occurrence of
Even when the welding average voltage Ea is low and a short circuit occurs during droplet detachment, it is possible to perform good pulse arc welding with reduced amount of spatter, and by setting the peak current Ip low, the arc sound becomes softer. It can reduce the burden on workers. In addition, since the peak current conduction period tp is controlled by the amount of energy supplied to the welding wire, for example, if the primary side power supply voltage decreases or the secondary side welding cable is long, the conduction current waveform may change due to cable inductance. Even in the case of dullness, the peak current application period tp is automatically controlled to be longer so that a certain amount of energy is applied to the welding wire, so that stable pulsed arc welding can be performed.

Next, the technical background of the present invention will be explained.

Figure 4 uses 1.2mmφ mild steel welding wire,
This is a graph obtained by actually measuring the value of the peak current energization period tp required to cause 1 pulse 1 droplet transfer by varying the peak current ■p when argon gas is used as the shielding gas, and the base current Ib Data is plotted when the welding average current Ia is varied with the welding average current ra fixed at 50A, and data when the base current 1b is varied while the welding average current ra is fixed at 20OA. According to this graph, when the average welding current Th is the same, the larger the base current Ib is, the shorter the peak current application period tp required to generate one droplet per pulse is.
It can be seen that when the base current Ib is the same, the peak current application period tp required to cause droplet detachment is reduced as the welding average current 1a is large.

In the present invention, in this graph, the peak current application period tp required for one pulse and one droplet transfer is calculated as follows:
The fact that it fluctuates depending on the sum of the energization energy between liJ1 tb and the peak current flow tlll1 tp, and that the energization energy is calculated by multiplying the base current Ib and the peak current 1p by a predetermined multiplier, respectively, is integrated. Utilizing the fact that it is almost equivalently determined by This achieves stable welding.

FIG. 5 shows the progress of droplet detachment with respect to time changes in welding current I in the pulsed arc welding method of the present invention. As a result, the tip of the welding wire W is constricted by the pinch effect caused by the applied current, and the droplet Wa is brought into a state where it is about to detach, and the peak current application period tp
After switching to the base current energization period tb, the droplet W
a is transferred to the base metal M side, and by controlling in this way, it is possible to perform good welding with a reduced amount of spatter even when the welding average voltage Ea is low and a short circuit occurs when the droplet detaches. It becomes possible.

Figures 6 (a) and (b) show how the droplet detachment cycle changes in pulsed arc welding, depending on the peak current Ip, the peak current conduction period tp, and the size of the base flow 1b. It is. That is, from Fig. 4, welding average current 1a = 200A (welding wire feeding speed = 7.3
m/m1n), peak current 1pl = 450 A, base current rb = i for 1.2mmφ mild steel wire
It can be seen that when a current of 50 A is applied, the minimum peak current application period tPI required for one pulse and one droplet transfer is approximately 1.7 ms (at this time, the current application period TI = 4.53 m5).

(See Figure 6(a)). Also, peak current 1p2=350
A. When base current rb=50A is applied, the minimum peak current application visit tP required for 1 pulse 1 droplet transfer
2 is approximately 3.25 m5 (at this time, the energization period T1 = 6.5 ms).

Fig. 6(b)
When the wire feeding speed) and the base current 1b are constant,
If the peak current 1p increases, the amount of droplets detached by one pulse will decrease, and the energization period T will become shorter; conversely, if the peak current a[p decreases, the amount of droplets detached by one pulse will increase. It can be seen that the energization period T becomes longer.

In the present invention, the peak period control means 1 integrates the base current 1b and the peak current 1p after arithmetic processing, but according to the above data, (Ipl"Xtp
l) + (IblLIXtbl) = (Ib2BXtb2
) + Multiplier A to satisfy (Ib2BXtb2)
, If B is determined, the peak current ■p and the base current 1b
The amount of energy supplied to the welding wire can be equivalently determined even when changing the amount of energy, and the peak current application period tp is automatically set so that the determined amount of energy becomes the optimal value for one pulse and one droplet transfer. It becomes possible to control.

Figures 7 (a) and (b) show the peaks for one droplet transfer per pulse depending on the magnitude of the base current (b) when the welding average current Ia and peak current tp are constant in pulsed arc welding. This figure shows how the current application period tp (the period up to the state just before the IAWIC melt'a is detached) changes. That is, when the base current 1b is low, the energy contributing to droplet detachment due to the base current 1bl is low, as shown in FIG. ! It is necessary to lengthen the current flow period tp3, and conversely, the base current rb
When the base voltage a is high, as shown in figure (b),
It can be seen that since the energy applied to the welding wire by I b 2 is large, the peak current application period tp must be shortened so that the droplets do not separate during the peak current application period tpA. The peak period control means 1 performs control that takes into consideration the energization energy caused by the base current [b].

Figure 8 shows the pulse arc welding method of the present invention described above*
*This is a block diagram showing an example of the configuration of a tx I-less arc welding device (corresponds to !Jl requirement 2).

In the figure, l is a peak period control means, 2 is a base period control means, 3 is an energization switching section, and 4 is a welding voltage setting section, and since these are the same as in FIG. 1, they are given the same symbols. . 5 is a current control means for outputting an energization control signal for switching the peak current 1p and the base current Ib and energizing in response to the switching signal of the energization switch M3; 6 is a current control means for controlling generation and extension of an arc when starting the welding device; This is a startup control unit that outputs a compensation signal for prompting. AMPI is a welding current amplification circuit that amplifies the welding current, AMP 2 is a welding voltage amplification circuit that amplifies the welding voltage (in this embodiment, the amplification degree is set to less than 1), and 7 is an output from the current control means 5. A pulse width controller 8 controls the duty of the switching voltage output from the inverter INV in accordance with an energization control signal, and a wire feed controller 8 controls the feed of the welding wire W.

In addition, RFC is a rectifier circuit section that rectifies three-phase AC voltage, and T
is a transformer that insulates and transforms the switching voltage output from the inverter INV, DI and D2 are diodes that full-wave rectify the power output from the transformer T, and S is a diode for extracting the welding current level as a corresponding voltage. In the shunt resistance, L is a no-actor, and M is a weld base metal.

In the peak period control means 1, the arithmetic circuit 10 and the voltage/L integration circuit 11 are the same as those shown in FIG. The current integration level determination unit 12 determines whether the current integration level of the current integration circuit 11 is at a predetermined level L.
Comparator 12a that outputs a peak current energization end signal when the peak current energization end signal is output when the energy applied to the welding wire reaches the optimal value required for one pulse and one droplet transfer. and a one-shot multivibrator (hereinafter referred to as one-shot MV) 12b which outputs a pulse signal having a predetermined time width Tm in response to the peak current energization end signal output from the comparator 12a. Further, the current integration circuit 11 receives a peak current energization end signal of pulse < T m output from the one-shot MV 12b, and its integration level is reset to return to zero level.

In the base period control means 2, a welding voltage error integration circuit 20 and a voltage integration level determination section 21 consisting of a zero-cross detection circuit are the same as in the case of FIG. The analog switch 5W20 is open until the arc occurs and the welding voltage amplification circuit AMP is switched on.
2, the no-load voltage amplified by welding voltage error integration circuit 20
As a result, the output timing of the base current energization end signal output from the zero-cross detection circuit 21 is determined by the no-load voltage until the arc occurs (higher than the welding voltage after the arc occurs). This prevents delays and controls the base current conduction period tb to the shortest possible time to promote arc expansion. In addition, in this configuration, the period in which the peak current energization end signal with the pulse width Tm is outputted from the peak period control means 1, even when the base current energization end signal is outputted from the base period control means 2. , the base electric current m I b is energized with priority.

The current control means 5 has a welding current setting 1g50 which determines the welding average current reference value 1r, and a peak current reference value 'a l.
A peak current setting section 51 that sets p r and a base 1i
A base current setting section 52 that sets the current reference value 1br, and an energization switching section 3 that sets the reference level set by each of these setting sections.
Analog switch 5W5 that selects the peak current energization signal or base current energization signal output from the
0. The SW 51 is provided with a welding current error amplification circuit 53 that outputs the error between the peak current reference value 1pr or the base current reference value 1br and the welding current (2) output from the welding current setting circuit gAMP1. In addition, the peak current setting section 5
1 is designed to be interlocked with the welding current setting section 50,
Even when the peak current reference value 1pr is set to the minimum value, it is prevented from becoming a value lower than the welding average current reference M I r. Further, the welding average current reference value 1r set by the welding current setting section 50 is output to the wire feeding control section 8, and the welding wire is fed at a speed proportional to the welding average current reference value 1r.

The pulse width control section 7 generates a pulse width control signal corresponding to the error signal transmitted from the current control means 5 through the PWM control circuit 7I, and outputs the pulse width control signal to the inverter INV through the drive circuit 70.
is transmitted to change the duty of the switching voltage, thereby performing feedback control so that the welding current (peak current 1p and base current 1b) always matches the level set by the current control means 50.

The starting control unit 6 controls the start control unit 6 for a predetermined time tl after the arc is generated.
At the same time, the starting current reference signal Is is sent to the welding current error amplification circuit 53 of the current control means 5, and the analog switch 5W20 of the energization cycle control means 2 is opened during the period until an arc occurs.

Next, the operation of the pulse arc welding apparatus having such a configuration will be explained with reference to the waveform charts shown in FIGS. 9(&) to (m). Note that corresponding parts in FIG. 8 are designated with corresponding symbols (a) to (m).

1. Operation at the start of welding.

■When you operate the torch switch (not shown), welding wire W
A no-load voltage is applied between the base material M and the base material M.

■During the period from when the no-load voltage is applied until the arc occurs, the analog switch SW 20 of the base period control means 2 is opened by the start control section 6, so that the no-load voltage is applied to the welding voltage error integration circuit. 20, the welding voltage error integration circuit 20 integrates the difference (-Er) between the zero-level welding voltage and the welding average voltage reference value Er, so the output level becomes zero, and the zero-crossing detection circuit 21 outputs a signal to the energization switching section. 3, the base current energization end signal is continuously output.

■When the welding wire W contacts the base metal M, an arc is generated,
During the period from when the arc occurs until a predetermined time t1 has elapsed, the starting current reference signal Is is sent from the starting control section 6 to the welding current error amplification circuit 53 of the current control means 5 to increase the welding current ■ to the maximum value. control and promote an increase in arc length.

(2) On the other hand, when the peak current energization signal is held and output from the energization switching section 3 in response to the base current energization end signal output from the base period control means 2, the peak period control means:
The calculation multiplier of the calculation circuit 10 is switched to A, and the welding current I (starting current I
s) is subjected to calculation processing (calculation of raising the starting current Is to the A power) in the calculation circuit 10, and the processed signal is integrated by the current integration circuit 11.

■When the integral output level of the current integrating circuit 11 reaches a predetermined level L determined in advance by the comparator 12a of the current integral level determining section 12, a peak current energization end signal is output to the one-shot MV 12b, and the one-shot MV 12b reaches this peak. Upon receiving the current energization end signal, the predetermined pulse width t
The signal m is output to the energization switching unit 3, and the current integration circuit 11 is reset (the pulse width tm is set to the time required to reset the current integration circuit 11).

■The energization switching unit 3 receives the peak current energization end signal output from the one-shot MV12b, holds and outputs the base current energization signal, and thereby switches the arithmetic multiplier of the arithmetic circuit IO to the multiplier B, and controls the welding current. The analog switch S W 51 of the means 5 is closed to switch the welding current I to the base current rb.

7 On the other hand, when an arc occurs, the control means 2 closes the analog switch 5W20, applies the welding voltage E to the welding voltage error integration circuit 20, and starts integrating the difference. As the base current increases, the output timing of the base current energization end signal is delayed, thereby increasing tb during the base $i distribution tlU1.

(At the beginning of welding, the base current conduction period tb is the minimum, so the peak period control means 1 is one-shot) At the same time as the peak current conduction period end signal of the pulse Illtm output from the MV12b stops, the peak current conduction period tb is restarted.
Return to p. ) In this way, during the first welding period, the base period control means 2 shortens the base current energization period tb'1trIt, and the starting current Is is applied by the starting control section 6 until the time t1 elapses, and the welding wire is Control is performed so that the arc length quickly reaches a predetermined value by promoting the melting of i! @
will gradually increase the welding average voltage Ea to the welding average voltage reference value E r
Control is performed to stabilize the arc and maintain a predetermined arc length.

2. Operation during steady welding.

After entering the steady welding state after the above-mentioned initial welding operation, the first
By the operation explained in the figure, the peak current energization signal and the base current energization signal are alternately output from the energization switching unit 3, and the current control means 5 receives these energization signals and alternately outputs the peak current 1p or the base current Ib. Turn on the electricity and weld. In addition, the operation when the average welding voltage is set low and a short circuit occurs when the droplet detaches during the base current energization interval tb, and the operation when the arc length increases and the base voltage Eb increases, etc. are as described above. Since it is the same as that described in FIG. 3, it will be omitted.

As described above, in the pulse arc welding apparatus of the present invention, the base period control means 2 controls the base current energization interval tb so that the welding average voltage Ea completely matches the welding average voltage reference 111iEr, and also Since no feedback control system is used, there is no control time delay or hunting compared to a negative feedback circuit configured using a V/F conversion circuit, etc., and the stability of the welding average voltage Ea is significantly improved. It becomes possible to do so.

In addition, since the peak current energization period tp is automatically controlled based on the amount of energy energized to the welding wire by the base current 1b and the peak current aIp, the peak current +p
, even when the base current 1b is set variably, 1 pulse 1
The peak current 1p is applied for the optimum time necessary for droplet transfer, and it is possible to effectively prevent droplet detachment during the peak current application period tp, and short circuits occur when the droplet detaches when the welding average voltage Ea is low. Even when the welding method is used, it is possible to perform welding with a reduced amount of spatter.

FIG. 10 shows a specific circuit example of the pulse arc welding apparatus of the present invention, in which the 86th minute corresponding to that in FIG. )～(m
) The corresponding parts (a) to (m) correspond to the waveform diagram.
The symbol is attached.

In the figure, the arithmetic circuit IO of the peak period control means l is
It is configured by combining a square calculation circuit 10a and an inversion amplifier circuit 10b, and when it receives a base tjfE energization signal from the energization switching section 3, it closes the analog switch 10c and performs calculation processing to raise the welding current I to the B power. On the other hand, when a peak current energization signal is received from the energization switching section 3, the analog switch 10d is closed and arithmetic processing is performed to raise the welding current I to the A power. The current integrator group Pi11 is constituted by an integrator circuit using an operational amplifier 11b, and receives the peak current energization end signal transmitted from the one-shot MV 12b to switch the analog switch lla.
is closed to forcibly discharge the charge in the integrating capacitor llc (reset operation). Energization switching section 3
is NAND gate 3a.

It has a configuration that combines an RS flip-flop 3b and a NOT gate 3C, and during the period when the peak current energization end signal is applied to the reset terminal R, the base current energization end signal is applied to the N A N through the NOT gate 3c.
Even when the base current energization signal is applied to the D gate 3a, priority is given to outputting the base current energization signal.

The welding voltage error integration circuit 20 of the base distance control means 2 is as follows:
The inverted and amplified negative level welding voltage E output from the welding voltage amplifier circuit AMP2 and the positive level welding average voltage set by the welding voltage setting section 4 are connected to the inverting input terminal side of the integrating circuit using the operational amplifier 20a. The difference between the welding voltage E and the welding average voltage reference value Er is equivalently integrated by adding the reference value Er and calculating and integrating the sum.

The diode 20b (using a Schottky barrier diode) causes the output level of the operational amplifier 20a to be lower than the zero level (actually, the forward voltage of the diode is lower than the zero level, so it is approximately -0.2 volts). This is a clamp diode for immediately raising the integral output from the zero level at the time of switching to the peak current conduction period tp without causing the integral output to decrease. In addition, the zero cross detection circuit 21 is composed of a comparator 21a with the reference voltage set to zero level, and during the period when an integral signal lower than the zero level is input to the inverting input terminal side, the base current supply at the "■" level ends. It is designed to output a signal.

In this embodiment, the comparator 21a of the zero-cross detection circuit 21 is operated by supplying positive and negative DC power supplies, but it is also possible to operate it using a DC power supply with only positive voltage. In order to prevent malfunctions due to excessive negative voltage being applied to the inverting input terminal side of the comparator 21a, the integrated output level is clamped to -0.2 volts by the diode 20b of the welding voltage error integration circuit 20, resulting in malfunctions. It also serves as prevention.

Further, in this configuration, the voltage is integrated when the integral output level of the welding voltage error integration circuit 20 of the base period control means 2 increases from zero level when the peak current is applied, and decreases to zero level when the base current is applied. Hell discrimination part (
The configuration is such that the welding voltage error integration circuit 20 performs integration in the direction falling from a predetermined level at the start of peak current energization, and detects the base current. It is possible to adopt a configuration in which integration is performed in the increasing direction during energization, and when the integrated output level matches the level at the start of integration, the voltage integration level determination section 21 does not detect.

FIG. 11 shows the welding apparatus of the present invention shown in FIG. 8, in which the peak period control means 1, the base period control means 2, the energization switching section 3, and the starting control section 6 are replaced by a signal processing section 9 comprising a CPU.
This shows an example of the configuration when the signal processing unit 9 is replaced with a ROM that stores processing programs, data, etc.
9a, - RAM 9b for temporarily storing processing data, etc.
are connected.

In the welding apparatus having such a configuration, the peak period control means 1
The arithmetic processing, integration processing, and integral level determination processing that were previously performed in the signal processing unit 9 are performed in a concentrated manner according to the program stored in the ROM 9a, and the welding processing that was previously performed in the base period control means 2 Voltage error integration processing and zero-cross detection processing are also performed under the approval of the signal processing unit 9 in the same way, making it possible to reduce the number of parts and simply modifying the program stored in the ROM 9a. This makes it possible to easily change the processing content, simplifying the design, and improving reliability.

In the figure, the signal processing section 9 performs the functions of the peak current energization period control means 2 and the activation control section 6, but the signal processing section 9 performs other functions.
It is also possible to have a configuration in which the tasks are performed in a concentrated manner. Furthermore, in the above description, the configuration is such that the signal processing section 9 performs signal processing in each section according to the program stored in the ROM 9a, but in order to improve the processing speed, a microprogram (hardware) is installed in the signal processing section 9. It is also possible to have a configuration in which a program is configured such that it performs the same processing as a program).

[Effects of the Invention] According to the pulse arc welding method of the present invention as set forth in claim 1, the average welding voltage is low and welding n! Even if a short circuit occurs during disconnection, or if the arc length fluctuates momentarily or the welding voltage changes due to factors such as camera shake, the base current is adjusted so that the average welding voltage completely matches the reference value. Since the energization visit is controlled and there is no control time delay or hunting, the stability of the welding average voltage can be significantly improved, making it possible to perform welding with a stable arc length. In addition, the peak current and base i current can be variably set, and the optimal peak current energization visit for pulse 1 droplet transfer is automatically controlled according to the set values. Fine-grained control can be performed according to welding conditions.

According to the present invention described in claim 2, it is possible to provide a pulse arc welding apparatus that can realize the welding method described in claim 1.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of main parts of a welding device for carrying out the pulse arc welding method according to claim 1, Figs. ~(d) are waveform diagrams explaining the control principles of the peak-to-peak opening control means and the base visiting control means, FIG. 4 is a graph showing the minimum value of the peak current energization period required for one pulse and one droplet transfer, and FIG. The figure is an explanatory diagram showing the progress of droplet detachment with respect to welding current.
FIGS. 6(a) and 6(b) are explanatory diagrams showing how the droplet transfer period changes due to changes in peak current, and FIG. 7(a). (b) is an explanatory diagram showing how the peak current energization period changes due to a change in the base current; FIG. 8 is a side view of the block configuration of the pulse arc welding apparatus of the present invention according to claim 2;
Figures 9(a) to (m) are waveform diagrams of each part thereof, Figure 10 is a detailed circuit diagram thereof, and Figure 11 is a diagram of the configuration of the pulse arc welding apparatus of the present invention when configured using a CPU. It is a diagram. [Explanation of symbols...Beak visit control means 1...Arithmetic circuit 11...Current integration circuit 12...Current integration level determination section 2...Base period control means 20...Welding voltage error integration Circuit 21... Voltage integration/＼ru discrimination part (zero cross detection circuit) 3 ・ 4 ・ E ・ r p b M ・ b p W φ ・Electrification switching section ・Welding voltage setting section ・Welding voltage . . . Welding average voltage Reference value: Peak current, Base current, Welding base material, Base current conduction period, Peak current conduction period, Welding wire

Claims (2)

[Claims] (1) In a pulsed arc welding method in which a peak current and a base current are applied alternately between the welding wire and the welding base metal, in order to control the peak current application period, when the base current is applied, the detected welding The current is integrated after being subjected to predetermined arithmetic processing, and when the subsequent peak current is applied, the detected welding current is subjected to predetermined arithmetic processing that is different from the arithmetic processing when the base current is applied, and then integrated. When the sum reaches a predetermined level, the peak current is stopped and the base current is applied, while the base current is controlled so that the welding average voltage matches the welding average voltage reference value. Then, the welding voltage detected from the start of the peak current application is compared with a predetermined welding average voltage reference value, and the integration of the difference is started, and when the base current is applied subsequently, this integral output level is set at the start of integration. A pulse arc welding method characterized in that when the level of the base current matches the level of the current, the base current is stopped and the peak current is switched to the peak current. (2) In a pulse arc welding device in which a peak current and a base current are applied alternately between the welding wire and the welding base metal, in order to control the peak current application period, the detected welding current is applied to the base metal. An arithmetic circuit that performs predetermined arithmetic processing when current is applied and when the peak current is applied, a current integration circuit that integrates a signal output from the arithmetic circuit and subjected to arithmetic processing, and the current peak period control means comprising: a current integral level determination section that outputs a peak current energization end signal and resets the current integrating circuit when the integral output level of the integrating circuit reaches a predetermined level; In order to control the base current energization period so that the average voltage matches the welding average voltage reference value, the welding voltage detected from the start of peak current energization to the time of base current energization is set to a predetermined welding average voltage reference value. A welding voltage error integrator circuit that compares the values and integrates the difference, and a voltage integration level determination that outputs a base current energization end signal when the integral output level of the welding voltage error integrator circuit matches the level at the start of integration. 1. A pulse arc welding device comprising: base period control means comprising: