JPH0472636B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an improvement in a welding device that performs short-circuit transitional arc welding by supplying power to a welding load via a DC reactor, and particularly relates to an improvement in a welding device that performs short-circuit transitional arc welding by supplying power to a welding load via a DC reactor. By creating this, the control output supplied to the welding load can be changed differently when a short circuit occurs and when an arc occurs, thereby supplementing or increasing the effect of the DC reactor and making it possible to downsize the DC reactor required for welding. This is what I did.

BACKGROUND ART A prior art example of this type of arc welding power supply device is JP-A-55-14977.

That is, what was proposed in JP-A-55-14977 is a welding power supply device using a controlled rectifying element (thyristor), in which the conduction angle of the controlled rectifying element is shortened by a certain amount when the wire is short-circuited during welding. When an arc occurs, the conduction angle is controlled to be longer by a certain amount, and this method has advantages in reducing the amount of spatter generated and downsizing the DC reactor.

Problems to be Solved by the Invention However, the above device can only control the conduction angle to a certain extent even when the welding conditions change, so in the small current range, the conduction angle becomes too short when the wire is short-circuited. This causes problems such as arc breakage and wire welding, and in a large current range, the control angle becomes relatively small with respect to the reference conduction angle, reducing the effectiveness of the electronic reactor.

The technical object of the present invention is to solve the above-mentioned problems.

Means for Solving the Problems The present invention was developed as a result of intensive studies by the inventor, and in electronically forming a composite control signal, the reference input signal is set to the reference input signal during the short circuit section. Subtracts the differential change amount according to the input signal or outputs a signal obtained by subtracting a certain amount from the reference input signal, while adding the differential change amount according to the reference input signal to the reference input signal during the arc generation section. The device is characterized in that it is configured to output a signal.

Effects of the Invention When short-circuit transition arc welding is performed using the device of the present invention, it is automatically determined whether the welding is in the short-circuit section or the arc generation section, and when the short-circuit section is in the short-circuit section, the reference input signal (according to the welding conditions) is automatically determined. It is possible to obtain a signal as a composite control signal by subtracting a differential change amount corresponding to the input signal level (set by A signal obtained by adding the amount of differential change according to the signal level can be obtained as a composite control signal, so if the level of the reference input signal increases, the composite control signal will change at a large rate of change, and the level of the reference input signal will increase. The smaller the change rate, the more the composite control signal can be changed at a small rate of change.

Effects of the Invention Since the device of the present invention is characterized by the above configuration, the effect of the DC reactor can be supplemented by the composite control signal, so the reactance value of the DC reactor required for welding can be reduced.
A small and inexpensive short-circuit transfer type arc welding power supply device can be provided.

In addition, in the device of the present invention, the composite control signal is changed at a rate according to the reference input signal set according to the welding conditions, so it is stable under all welding conditions from small current range to large current range. You can expect the same effect.

Furthermore, in the apparatus of the present invention, the rising slope of the welding current during the short-circuit section is suppressed and the peak current is suppressed, so that the amount of spatter generated can also be reduced.

In addition, since the welding voltage waveform can have a sufficiently steep slope at the time of arc generation, the generation of molten balls can be effectively prevented.

For these reasons, the apparatus of the present invention has advantages such as stabilizing the peak even during high-speed welding and making it possible to perform welding with excellent bead appearance.

Embodiment of the Invention An embodiment of the invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a schematic configuration of the device of the present invention, in which A is a control circuit section, B is an output control section including switching elements such as thyristors and transistors, 1 is a welding wire, and 2 is a welding wire. 3 is a base material which is a workpiece to be welded, 4 is a DC reactor, 5 is a welding wire feed roll, 6 is a speed control circuit for a motor 7 for driving a welding wire feed roll, and 8 is a transformer or DC power source. , constitutes a welding power source.

Further, reference numeral 9 indicates a welding condition setting device (setting a reference voltage Vref which becomes a reference input signal to be described later) provided in the control circuit section A to obtain a control output according to the welding conditions.

FIG. 2 shows the configuration of a control circuit section forming a main part of the apparatus of the present invention.

This circuit section A includes a short circuit/arc discrimination circuit 10,
It is composed of a feed bag control circuit 11 and a composite signal generation circuit 12, and the circuit as a whole converts the feed bag signal (Vfeed) taken out from the output side of the output control section into the control signal Vcont output from the composite signal generation circuit 12. A control signal Vout is sent to the output control section B so that they match.

However, in the embodiment, when the level of the control signal is high, the output is low, and when the level of the control signal is low, the output is high.

The short circuit/arc discrimination circuit 10 is an operational amplifier OP
3 is provided with hysteresis setting resistors R11 and R12 to form a positive feedback circuit, and the reference signal Vref
into the inverting input terminal of the operational amplifier OP3, and the load voltage Va extracted from the output side of the DC reactor into the non-inverting input terminal of the operational amplifier OP3 in the voltage divider circuit 10.
It is input via 1.

Light emitting diodes constituting photocouplers PC1 to PC4 are provided at the output end of the operational amplifier OP3.

In other words, the load voltage Va is determined by the voltage dividing circuit 101 consisting of resistors R9 and R10 and the clamp diode D1.
The reference voltage Vref, which is set according to the welding conditions, is input to the non-inverting input terminal of the operational amplifier OP3 via the inverting input terminal of the operational amplifier OP3.

The light emitting diode installed at the output end of operational amplifier OP3 is a component of PC1 and PC4.
The components of PC2 and PC3 are connected in antiparallel to each other, and when the output of operational amplifier OP3 reaches a positive saturation level, PC1 and PC4 are turned on.
When the negative saturation level is reached, PC2 and PC3
turns on.

A resistor R13 provided between the antiparallel body of the light emitting diodes and the ground is a current setting resistor for setting the current flowing through the light emitting diodes.

On the other hand, the composite signal generation circuit 12 includes an operational amplifier
An inverting adder using OP1 is configured, and the inverting input terminal of operational amplifier OP1 is connected to a reference signal input circuit 120 configured by external resistor R1, photocouplers PC1 and PC2, capacitor C1, and resistor R.
2, the first differentiation circuit 12 configured using R6
1 and photocoupler PC3, PC4, operational amplifier OP
Gain 1 configured using 2 and resistors R4 and R5
inverting amplifier, capacitor C2, resistor R3, R
The second differentiating circuit 122 configured using 7 is connected in parallel.

A reference voltage Vref that is set according to welding conditions is supplied to the input terminals of these three circuits 120 to 122.

On the other hand, the feedback control circuit 11 is constructed by connecting a first inverting amplifier constructed using an operational amplifier OP4 to a second inverting amplifier constructed using an operational amplifier OP5.

Here, the first inverting amplifier includes an output control section B.
Feedback signal extracted from the output side of
Vfeed is input, and the second inverting amplifier amplifies the error between the amplified feedback signal Vfeed output from the first inverting amplifier and the composite control signal Vcont output from the composite signal generation circuit 12, The output is outputted to the output control section B as a control signal Vout.

Next, the operation of the present invention will be explained.

Now, during welding, if the welding wire is short-circuited, the load voltage Va will be approximately 0V, so the voltage divider circuit 10
The terminal voltage Va' of the resistor R10 of 1 is also approximately 0V.

Then, the input condition of operational amplifier OP3 is Vref＞
Va', the output of the operational amplifier OP3 becomes a negative saturation level (-Vcc), and the photocoupler PC2,
PC3 is turned on. At this time, photocoupler PC1,
PC4 is turned off.

As a result, in the first differentiating circuit 121, PC1
is OFF and PC2 is ON, so capacitor C
1. A discharge loop is formed by the resistor R6 and the photocoupler PC2, and the charge stored in the capacitor C1 is instantly discharged.

At the same time, the second differentiating circuit 122 uses the PC
3 is ON and PC4 is OFF, so resistor R3,
An inverting amplifier with a gain of 1 consisting of a resistor R7, a capacitor C2, a photocoupler PC3, an operational amplifier OP2 and resistors R4 and R5 (the output is
), a charging loop is formed, a charging current i2 flows, and the capacitor C2 is charged.

However, when welding arc occurs during welding, the welding load Va takes a value according to the set welding conditions, so the input condition of operational amplifier OP3 becomes Vref<Va', and the output of operational amplifier OP3 becomes positive. It reaches the saturation level (+Vcc), and photocouplers PC1 and PC4 turn on. At this time, photocouplers PC3 and PC3 are turned off.

As a result, in the first differentiation circuit 121, PC1
is ON and PC2 is OFF, so the differentiator circuit 12
1, a charging loop is formed by photocoupler PC1, capacitor C1, and resistor R6, and charging current i
1 flows and the capacitor C1 is charged.

At the same time, the second differentiating circuit 122
Since PC4 is ON and PC3 is OFF, a discharge loop is formed by photocoupler PC4, capacitor C2, and resistor R7, and the electric charge stored in capacitor C2 is instantly discharged.

As a result of the above operation, the short circuit/arc discrimination circuit 10
When it determines that the welding wire is short-circuited,
The composite control signal Vcont is subtracted from the reference voltage Vref by the amount of differential change corresponding to the time constant of the charging loop in which the second differentiating circuit 122 is formed.

In the example, the composite control signal Vcont is
Since it is obtained as the output of the inverting adder, applying Kirchhoff's law now, iref=i2+if Vref/R1=i2+(0−Vcont)/R8 Therefore, Vcont=−R8(Vref/R1−i2) i2=Vref/(R3+R7) [1-et/C2(R3+R7)] (where i2 is the charging current flowing through the second differentiator circuit, and if is the current flowing through the feedback resistor R8 of the operational amplifier OP1) On the other hand, When the short circuit/arc discrimination circuit 10 determines that a welding arc has occurred, the control signal is
Vcont is added to the reference voltage Vref by the amount of differential change corresponding to the time constant of the charging loop formed in the first differentiating circuit 121, and as shown in FIG.
A synthesized control signal with the waveform shown in
Vcont is obtained.

In the example, the composite control signal Vcont is
Since it is obtained as the output of the inverting adder, applying Kirchhoff's law, irer + i1 = if Vref / R1 + i1 = (0 - Vcont) / R8 Therefore, Vcont = -R8 (Vref / R1 + i1) i1 = Vref / (R2+R6) [1-et/C1(R2+R6)] (where i1 is the charging current if flowing through the first differentiating circuit and represents the current flowing through the feedback resistor R8 of the operational amplifier OP1) As a result, the present invention In the device, a synthesized control signal with a waveform as shown in Figure 3a is used.
Vcont will be obtained.

In addition, Fig. 3 b and c are composite control signals.
It shows waveform diagrams of welding load current Ia and load voltage Va according to Vcont, and Figures 4 a to c show output characteristic diagrams corresponding to Figure 3 of the conventional device with a constant composite control signal Vcont. There is.

As is clear from the comparison between Figures 3 and 4, in the device of the present invention, the rising slope of the welding current Ia in the short-circuit period t is suppressed, and the peak current is suppressed, so the amount of spatter generated is reduced. It is highly effective in reducing

Furthermore, since the welding voltage Va has a sufficiently steep slope during the arc generation period T, it also has the effect of suppressing the generation of molten balls.

Because of these effects, the arc can be stabilized even during high-speed welding, and welding with excellent bead appearance can be expected.

FIG. 5 is a diagram showing the configuration of another example of the device of the present invention, particularly a control circuit section in which the composite control signal Vcon at the time of a short circuit changes to a level obtained by subtracting a certain amount from the reference input signal Vref.

In this circuit section, when the short circuit/arc discrimination circuit 10' detects a short circuit in the welding wire,
Since the photocouplers PC2 and PC3 are turned ON and PC1 is turned OFF, the charge stored in the capacitor C1 in the first differentiating circuit 121' is instantly discharged, and in the second differentiating circuit 122', the photocoupler PC3, the resistor R3, An energizing loop is formed by R7 and an inverting amplifier with a gain of 1.

On the other hand, when the short circuit/arc discrimination circuit 10' detects the occurrence of an arc, the photocoupler PC1
is turned ON and the photocouplers PC2 and PC3 are turned OFF, so that a charging loop is formed by the capacitor C1 and the resistors R2 and R6 in the first differentiating circuit 121', and the capacitor C1 is charged.

As a result, as shown in FIG. 6, a flat composite control signal Vcont obtained by subtracting a certain amount from the reference input signal is obtained in the short-circuit period t. It is included in the above, and has the same effect as the above-mentioned one.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing a schematic configuration of the device of the present invention;
Fig. 2 is a circuit diagram showing the configuration of the control circuit section, Figs. 3 a to c are output characteristic diagrams corresponding to the composite control signal to explain the operation of the device of the present invention, and Fig. 4 is the same as Fig. 3 in the conventional device. Corresponding figures, FIG. 5 are circuit diagrams showing the configuration of other examples of the control circuit section, and FIGS. 6 a to c
shows an output characteristic diagram of the control circuit shown corresponding to FIG. (Explanation of symbols) A indicates an output control section, B indicates a control circuit section, 10 indicates a short circuit/arc discrimination circuit, 11 indicates a feedback control circuit, and 12 indicates a composite signal generation circuit.

Claims (1)

[Scope of Claims] 1. In a short-circuit transitional arc welding power supply device that extracts a feedback signal from the output side of an output control section and supplies current to a welding load via a DC reactor, the power supply device includes: (a) detecting a load voltage; (b) A short circuit/arc discrimination circuit that determines whether the current is in a short circuit section or an arc generation section based on the voltage level of A composite signal generation circuit that outputs a composite control signal obtained by adding or subtracting a predetermined amount of change to a reference signal set according to conditions, and (c) an error between the composite control signal of this composite signal generation circuit and the above feedback signal. (d) The composite signal generating circuit generates a differential change in the reference input signal according to the reference input signal during a short-circuit period. A signal obtained by subtracting a certain amount from the reference input signal or by subtracting a certain amount from the reference input signal is output as a composite control signal, while a signal obtained by adding the amount of differential change according to the reference input signal to the reference input signal during the arc generation section. A short-circuit transitional arc welding power supply device, characterized in that it is configured to output the following as a composite control signal.