JP7542373B2 - Pulse Arc Welding Power Supply - Google Patents

Description

The present invention relates to a pulse arc welding power source that can suppress variations in arc length during peak and base periods.

Consumable electrode pulsed arc welding is widely used for welding steel and the like. In this type of pulsed arc welding, the welding wire is fed, a peak current is passed during the peak period, and a base current is passed during the base period, and welding is performed by repeating these welding current passes as one pulse cycle. In addition, the arc length is maintained at an appropriate value by feedback controlling the pulse cycle or peak period of the welding current so that the average value of the welding voltage is equal to the welding voltage set value. In pulsed arc welding, one droplet is transferred per pulse cycle, and the droplet transfer state is stable, so there is little spatter and a beautiful bead appearance can be obtained.

In consumable electrode arc welding, including pulse arc welding, maintaining the arc length during welding at an appropriate value is important to obtain good welding quality. The average value of the welding voltage is proportional to the average arc length. Therefore, in pulse arc welding, the welding wire is fed at a constant speed, and feedback control is performed so that the average value of the welding voltage is equal to a predetermined welding voltage setting value, thereby controlling the average arc length to an appropriate value. However, the instantaneous arc length fluctuates during the pulse period, as melting is promoted during the peak period when a peak current of a large current value flows, and melting is suppressed during the base period when a base current of a small current value flows, and the instantaneous arc length becomes longer. In the invention of Patent Document 1, the feed speed during the peak period is faster than the feed speed during the base period. This suppresses the fluctuation of the arc length during the pulse period, thereby improving the welding quality.

JP 2015-30017 A

In conventional pulse arc welding, the welding wire feed speed is made faster during peak periods than during base periods, and the welding current is controlled so that the average value of the welding voltage is equal to the welding voltage set value. This feedback control causes the pulse period or peak period of the welding current to change from moment to moment. As a result, the average value of the feed speed also fluctuates from moment to moment. When the average value of the feed speed fluctuates, the problem of uneven bead appearance occurs.

The present invention aims to provide a pulse arc welding power supply that can suppress fluctuations in the average feed speed and obtain a good bead appearance in pulse arc welding, in which the welding wire feed speed is made faster during peak periods than during base periods, and the welding current is controlled so that the average value of the welding voltage is equal to the welding voltage set value.

In order to solve the above-mentioned problems, the invention of claim 1 comprises:
a feed motor that feeds the welding wire;
A feed control unit that controls a feed speed of the feed motor;
a power control unit that outputs a welding current with a peak current during a peak period and a base current during a base period as one pulse period;
a voltage feedback control unit that controls the pulse period or the peak period of the welding current so that an average value of the welding voltage becomes equal to a predetermined welding voltage set value;
In a pulse arc welding power source comprising:
the feed control unit sets a feed rate set value formed from a peak period feed rate set value and a base period feed rate set value, sets the peak period feed rate set value to a value faster than the base period feed rate set value, controls the feed rate to be equal to the feed rate set value, and variably controls the peak period feed rate set value and/or the base period feed rate set value so that a detected value of an average feed rate is equal to a predetermined average feed rate set value.
The present invention relates to a pulse arc welding power source.

In the present invention, the welding current further has a rise period and a fall period,
the feed rate set point is accelerated from the base period feed rate set point to the peak period feed rate set point during the rise period, and decelerated from the peak period feed rate set point to the base period feed rate set point during the fall period;
2. A pulse arc welding power supply according to claim 1 .

According to the pulse arc welding power supply of the present invention, in pulse arc welding in which the welding wire feed speed is made faster during peak periods than during base periods and the welding current is controlled so that the average value of the welding voltage is equal to the welding voltage set value, it is possible to suppress fluctuations in the average value of the feed speed and obtain a good bead appearance.

1 is a block diagram of a pulse arc welding device according to an embodiment of the present invention. 2 is a timing chart of each signal in the pulse arc welding device of FIG. 1 .

The following describes an embodiment of the present invention with reference to the drawings.

Figure 1 is a block diagram of a pulse arc welding device according to an embodiment of the present invention. The welding device is mainly composed of a welding power source PS, a robot control device RC, a robot (not shown), etc., all of which are enclosed by dashed lines. Each block will be explained below with reference to the figure.

The welding power source PS consists of the following blocks:

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

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

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

The welding voltage detection circuit VD detects the above welding voltage Vw and outputs a welding voltage detection signal Vd. The welding voltage averaging circuit VAV averages this welding voltage detection signal Vd (passes it through a low-pass filter) and outputs a welding voltage average value signal Vav. The welding voltage setting circuit VR outputs a predetermined welding voltage setting signal Vr. The voltage error amplifier circuit EV amplifies the error between the above welding voltage setting signal Vr (+) and the above welding voltage average value signal Vav (-) and outputs a voltage error amplifier signal Ev.

The voltage feedback control circuit VF receives the voltage error amplified signal Ev, performs voltage/frequency conversion based on the voltage error amplified signal Ev, and outputs a pulse period signal Tf that is at a high level for a short period of time every pulse period.

The rising period setting circuit TUR outputs a predetermined rising period setting signal Tur. The peak period setting circuit TPR outputs a predetermined peak period setting signal Tpr. The falling period setting circuit TKR outputs a predetermined falling period setting signal Tkr.

The peak current setting circuit IPR outputs a predetermined peak current setting signal Ipr. The base current setting circuit IBR outputs a predetermined base current setting signal Ibr.

The welding current setting circuit IR receives as inputs the pulse period signal Tf, the rise period setting signal Tur, the peak period setting signal Tpr, the fall setting signal Tkr, the peak current setting signal Ipr and the base current setting signal Ibr, and performs the following processing each time the pulse period signal Tf changes to a High level for a short period of time, to output a welding current setting signal Ir and a timer signal Tm.
1) During the rise period Tu determined by the rise period setting signal Tur, a timer signal Tm=1 is output, and a welding current setting signal Ir that increases linearly from the value of the base current setting signal Ibr to the value of the peak current setting signal Ipr is output.
2) Subsequently, during the peak period Tp determined by the peak period setting signal Tpr, a timer signal Tm=2 is output, and the peak current setting signal Ipr is output as the welding current setting signal Ir.
3) Subsequently, during the falling period Tk determined by the falling period setting signal Tkr, a timer signal Tm=3 is output, and a welding current setting signal Ir that decreases linearly from the value of the peak current setting signal Ipr to the value of the base current setting signal Ibr is output.
4) Subsequently, during the base period Tb until the pulse period signal Tf again goes high for a short time, the timer signal Tm=4 is output, and the base current setting signal Ibr is output as the welding current setting signal Ir.

The average feed speed setting circuit FAR outputs a predetermined average feed speed setting signal Far. The feed speed error amplifier circuit EF amplifies the error between the average feed speed setting signal Far(+) and an average feed speed detection signal Fad(-) described below, and outputs a feed speed error amplification signal Ef.

The peak period feed rate setting circuit FPR receives the above-mentioned feed rate error amplification signal Ef as an input, performs variable speed control of Fpr = Fp0 + ∫Ef, and outputs the peak period feed rate setting signal Fpr. Fp0 is an initial value, and Fp0>Far. The base period feed rate setting signal FBR outputs a predetermined base period feed rate setting signal Fbr. It is set to Fbr<Far. These circuits make the peak period feed rate Fp faster than the base period feed rate Fb. Furthermore, even if the pulse period changes due to voltage feedback control, the peak period feed rate Fp is variably controlled so that the value of the average feed rate detection signal Fad is equal to the value of the average feed rate setting signal Far. The peak period feed rate Fp may be set to a predetermined value, and the base period feed rate Fb may be variably controlled. Furthermore, both the peak period feed rate Fp and the base period feed rate Fb may be variably controlled.

The welding current detection circuit ID detects the welding current Iw and outputs a welding current detection signal Id. The current error amplifier circuit EI amplifies the error between the welding current setting signal Ir(+) and the welding current detection signal Id(-) and outputs a current error amplifier signal Ei. The drive circuit DV receives the current error amplifier signal Ei and a start signal On from the robot control device RC described below as inputs, and when the start signal On is at a high level (welding starts), it performs PWM modulation control based on the current error amplifier signal Ei and outputs a drive signal Dv for driving the inverter circuit in the power control circuit MC, and does not output the drive signal Dv when the start signal On is at a low level (welding stops).

The feed speed setting circuit FR receives the peak period feed speed setting signal Fpr, the base period feed speed setting signal Fbr, and the timer signal Tm, performs the following processing, and outputs a feed speed setting signal Fr.
1) During the rising period Tu of the timer signal Tm=1, the feed speed setting signal Fr that linearly accelerates from the value of the base period feed speed setting signal Fbr to the value of the peak period feed speed setting signal Fpr is output.
2) Subsequently, during the peak period Tp of the timer signal Tm=2, the peak period feed speed setting signal Fpr is output as the feed speed setting signal Fr.
3) Subsequently, during the falling period Tk of the timer signal Tm=3, the feed speed setting signal Fr is output, which linearly decelerates from the value of the peak period feed speed setting signal Fpr to the value of the base period feed speed setting signal Fbr.
4) Subsequently, during the base period Tb of the timer signal Tm=4, the base period feed speed setting signal Fbr is output as the feed speed setting signal Fr.

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

The average feed speed detection circuit FAD receives the above-mentioned feed speed setting signal Fr as input, detects the average value of the feed speed setting signal Fr, and outputs the average feed speed detection signal Fad.

The robot control device RC moves the robot (not shown) according to a pre-taught work program and outputs an activation signal On to command the start or stop of welding.

Figure 2 is a timing chart of each signal in the pulse arc welding device of Figure 1. Figure (A) shows the change over time of the welding current Iw, Figure (B) shows the change over time of the welding voltage Vw, and Figure (C) shows the change over time of the welding wire feed speed Fw. The operation of each signal will be explained below with reference to the figure.

During the pulse period Tf from time t1 to t2, during the predetermined rise period Tu, as shown in FIG. 1A, an upward transition current Iu is applied that rises from a predetermined base current Ib to a predetermined peak current Ip, as shown in FIG. 1B, an upward transition voltage is applied between the welding wire and the base metal that rises from a base voltage Vb to a peak voltage Vp, as shown in FIG. 1C, the feed speed Fw accelerates from the base period feed speed Fb to the peak period feed speed Fp. During the subsequent predetermined peak period Tp, as shown in FIG. 1A, a peak current Ip of a large current value equal to or greater than the critical value is applied to transfer droplets from the welding wire, as shown in FIG. 1B, a peak voltage Vp proportional to the arc length is applied, as shown in FIG. 1C, and the feed speed Fw becomes the peak period feed speed Fp. During the subsequent predetermined fall period Tk, as shown in FIG. 1A, a falling transition current Ik is passed which falls from a peak current Ip to a base current Ib, as shown in FIG. 1B, a falling transition voltage is applied which falls from a peak voltage Vp to a base voltage Vb, as shown in FIG. 1C, the feed speed Fw is decelerated from the peak period feed speed Fp to the base period feed speed Fb. During the subsequent base period Tb, as shown in FIG. 1A, a base current Ib with a small current value less than the critical value is passed in order to prevent droplets from being formed, as shown in FIG. 1B, a base voltage Vb proportional to the arc length is applied, as shown in FIG. 1C, and the feed speed Fw becomes the base period feed speed Fb. During the peak period Tp, the peak current Ip with a large current value is passed, promoting melting and making the arc longer, and during the base period Tb, the base current Ib with a small current value is passed, suppressing melting and making the arc shorter. However, because the feed speed Fw is faster during the peak period than during the base period, the range of change in arc length is smaller than when the feed speed is constant, and the welding condition is stabilized.

In this embodiment, the pulse period Tf is feedback-controlled (modulation-controlled) so that the value of the welding voltage average value signal Vav in FIG. 1 is equal to the predetermined value of the welding voltage setting signal Vr in FIG. 1. For this reason, the rise period Tu, peak period Tp, fall period Tk, peak current Ip, and base current Ib are set to predetermined values, and the base period Tb (pulse period Tf) is determined by feedback control so that the average value of the welding voltage Vw is equal to the predetermined welding voltage setting value. This controls the average arc length to an appropriate value.

The rise period Tu is set by the rise period setting signal Tur in FIG. 1, the peak period Tp is set by the peak period setting signal Tpr in FIG. 1, and the fall period Tk is set by the fall period setting signal Tkr in FIG. 1. The peak current Ip is set by the peak current setting signal Ipr in FIG. 1, and the base current Ib is set by the base current setting signal Ibr in FIG. 1. The peak period feed rate Fp is set by the peak period feed rate setting signal Fpr in FIG. 1, and the base period feed rate Fb is set by the base period feed rate setting signal Fbr in FIG. 1.

In the pulse period Tf from time t2 to t3, the waveforms of the welding current Iw, welding voltage Vw, and feed speed Fw are the same as in the previous period. However, the peak period feed speed Fp is greater than in the previous period. As described above, the pulse period Tf changes from moment to moment due to voltage feedback control. Accordingly, the average value of the feed speed Fw also fluctuates. In contrast, in this embodiment, the peak period setting signal Fpr in FIG. 1 is variably controlled so that the average feed speed detection signal Fad in FIG. 1 is equal to the predetermined average feed speed setting signal Far in FIG. 1. This variable speed control changes the peak period feed speed Fp. As a result, the average value of the feed speed Fw becomes a constant value, ensuring uniformity in the bead appearance.

In the above variable speed control, the peak period feed speed setting signal Fpr and/or the base period feed speed setting signal Fbr may be changed so that the average feed speed detection signal Fad is equal to the average feed speed setting signal Far.

In the above, the voltage feedback control was described as pulse period modulation control, which changes the pulse period, but the same applies to peak period modulation control, which changes the peak period.

Numerical examples of the above-mentioned parameters are shown below.
Tu=0.5ms, Tp=1.2ms, Tk=0.5ms, Tf≒5ms
Ip=450A, Ib=50A
Far=3.5m/min, Fb=3m/min, Fp≒4.5m/min

According to the above-described embodiment, the feed control unit variably controls the peak period feed rate and/or the base period feed rate so that the peak period feed rate is faster than the base period feed rate and the average feed rate is constant. This makes it possible to reduce the instantaneous change in arc length between the peak period and the base period and to maintain the average feed rate constant, ensuring uniformity in bead appearance. As a result, in this embodiment, in a pulse arc welding power source that makes the welding wire feed rate faster during the peak period than during the base period and controls the welding current so that the average welding voltage is equal to the welding voltage setting value, it is possible to suppress fluctuations in the average feed rate and obtain a good bead appearance.

Furthermore, according to this embodiment, the welding current further includes a rise period and a fall period, and the feed speed is accelerated from the base period feed speed to the peak period feed speed during the rise period, and is decelerated from the peak period feed speed to the base period feed speed during the fall period. As a result, in this embodiment, the feed speed changes in synchronization with the waveform of the welding current, making it possible to further reduce instantaneous changes in the arc length and to make the welding state more stable.

1 welding wire 2 base material 3 arc 4 welding torch 5 feed roll DV drive circuit Dv drive signal EF feed speed error amplifier circuit Ef feed speed error amplifier signal EI current error amplifier circuit Ei current error amplifier signal EV voltage error amplifier circuit Ev voltage error amplifier signal FAD average feed speed detection circuit Fad average feed speed detection signal FAR average feed speed setting circuit Far average feed speed setting signal Fb base period feed speed FbR base period feed speed setting circuit Fbr base period feed speed setting signal FC feed control circuit Fc feed control signal Fp peak period feed speed FPR peak period feed speed setting circuit Fpr peak period feed speed setting signal FR feed speed setting circuit Fr feed speed setting signal Fw feed speed Ib base current IBR base current setting circuit Ibr base current setting signal ID welding current detection circuit Id welding current detection signal Ik Falling transition current Ip Peak current IPR Peak current setting circuit Ipr Peak current setting signal IR Welding current setting circuit Ir Welding current setting signal Iu Rising transition current Iw Welding current MC Power control circuit On Start signal PS Welding power source RC Robot control device Tb Base period Tf Pulse period (signal)
TKR Falling period setting circuit Tkr Falling period setting signal Tp Peak period TPR Peak period setting circuit Tpr Peak period setting signal Tu Rising period TUR Rising period setting circuit Tur Rising period setting signal VAV Welding voltage averaging circuit Vav Welding voltage average value signal Vb Base voltage VD Welding voltage detection circuit Vd Welding voltage detection signal VF Voltage feedback control circuit Vp Peak voltage VR Welding voltage setting circuit Vr Welding voltage setting signal Vw Welding voltage WL Reactor WM Feeder motor

Claims (2)

a feed motor that feeds the welding wire;
A feed control unit that controls a feed speed of the feed motor;
a power control unit that outputs a welding current with a peak current during a peak period and a base current during a base period as one pulse period;
a voltage feedback control unit that controls the pulse period or the peak period of the welding current so that an average value of the welding voltage becomes equal to a predetermined welding voltage set value;
In a pulse arc welding power source comprising:
the feed control unit sets a feed rate set value formed from a peak period feed rate set value and a base period feed rate set value, the peak period feed rate set value is a value faster than the base period feed rate set value, controls the feed rate to be equal to the feed rate set value, and variably controls the peak period feed rate set value and/or the base period feed rate set value so that a detected value of an average feed rate is equal to a predetermined average feed rate set value.
A pulse arc welding power source comprising: the welding current further comprises a rise period and a fall period;
the feed rate set point is accelerated from the base period feed rate set point to the peak period feed rate set point during the rise period, and decelerated from the peak period feed rate set point to the base period feed rate set point during the fall period;
2. A pulse arc welding power supply as claimed in claim 1.

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