JPH0331551B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a short-circuit transitional arc welding machine that performs welding by frequently repeating short-circuiting and arc generation between a wire electrode (hereinafter simply referred to as "wire") and a base material. It is.

A prior art arc welding machine of this type is shown in FIG. In the figure, 1
is a wire, 2 is a base material that is the object to be welded, 3 is a wire feeding motor for feeding the wire 1 in the direction of the base material 2, 4 is a torch through which the wire 1 passes, and 5 is a rectified three-phase alternating current. 6 is a switching element such as a transistor for turning on and off the output voltage of the DC power supply circuit 5; 7 is a reactor; 8
1 is a flywheel diode for circulating the energy stored in the reactor 7 immediately after the switching element 6 is turned off; 9 is a voltage detector for detecting the voltage between the wire 1 and the base material 2;
0 and 11 are the first voltages for comparing the welding voltage detected by the voltage detector 9 and the reference voltages V _p and V _p ;
A second comparator, 12 is a timer for giving a delay time T to the signal from the comparator 11, 13 is an ON command from the comparator 10, and a timer 13 for giving an ON command from the comparator 10 and a timer 12
Upon receiving the OFF command, the switching element 6 turns ON,
Switch command circuit for commanding OFF, 14
1 is an auxiliary power source for ensuring the operation of the voltage detector 9, and 10 to 13 constitute a control circuit 15.

Next, the operation of this short-circuit transitional arc welding machine will be explained. First, the wire feeding motor 3 is driven to feed the wire 1 toward the base material 2 . A minute voltage is applied between the wire 1 and the base material 2 by the auxiliary power source 14, and the voltage detector 9 detects a short circuit between the wire 1 and the base material 2 based on the voltage change.
The detected voltage V is compared with the short circuit judgment voltage value V _p between the wire 1 and the base material 2 by the comparator 10, and if V≦V _p , the switch command circuit 13 sends an ON signal to the switching element 6. is emitted, the switching element 6 becomes conductive, and the reactor 7
Short circuit current rises with a time constant determined by Similarly, the detected voltage V is compared with the arc judgment voltage V _p by the comparator 11, and if V≦V _p , the switch command circuit 13 issues a switching signal after a predetermined delay time T has elapsed as necessary. to element 6
When the OFF signal is issued, the switching element 6 is cut off, and thereafter the energy stored in the reactor 7 is released via the wire 1, the base material 2, and the flywheel diode 8. Figures 2a and 2b are current and voltage waveform diagrams during welding, and Figure 2c is a diagram showing the short circuit period and arcing period between wire 1 and base metal 2.As shown in the figure, the welding current waveform is It becomes almost a triangular wave.

This short-circuit transitional arc welding machine is configured as described above, and it is determined that the wire has contacted the base material when the short-circuit reference voltage V _p is reached, and from that point on, the current to burn out the wire (short-circuit current ) is configured to rise at a constant slope determined by the reactor 7.

Generally, in an arc welding machine, it is necessary to change the feeding speed of a wire feeding device depending on welding conditions such as the thickness of the base material. In this welding machine, when a short circuit occurs, the short circuit voltage has a constant rise determined by the no-load voltage of the DC power supply circuit 5 and the reactor 7, so if the feed speed of the wire feeding device is too fast compared to the rise of the short circuit voltage, The disadvantage was that the wire penetrated too far into the base metal, prolonging the short circuit time, and causing large spatter during arc regeneration. In addition, due to camera shake of the welding torch, it is not possible to correct the arc length that changes instantaneously with the momentary short-circuit voltage waveform and arc voltage waveform, and due to camera shake of the welding torch, the short-circuit time and arc period vary. This caused instability in the arc length, and there was a risk of weld bead defects.

This invention was made to eliminate the above-mentioned drawbacks, and the welding current is adjusted so that the welding voltage increases along a predetermined reference short-circuit voltage waveform V _sp from the point at which the wire electrode short-circuits to the base metal. The welding current is also controlled so that the welding voltage decreases along a predetermined reference arc voltage waveform V _ap from the time when the arc is regenerated between the wire electrode and the base metal. This reference short-circuit voltage waveform V _sp is predetermined as a waveform that becomes a first predetermined signal value after a first predetermined time from the point of short circuit, and the reference arc voltage waveform V _ap is a waveform that becomes the first predetermined signal value after a first predetermined time from the point of short circuit.
This waveform is predetermined as a waveform that reaches a second predetermined signal value after a predetermined time. When such control is performed, fluctuations in the short-circuit period and fluctuations in the arc period caused by changes in the wire feeding speed or instantaneous changes in the arc length due to hand shake of the torch, etc. can be reflected in the instantaneous short-circuit voltage waveform. and arc voltage waveforms will also be automatically corrected.

Before arriving at this invention, the inventors photographed the melting transfer phenomenon of the short-circuit transfer arc phenomenon with a high-speed camera and carefully analyzed the welding current waveform and welding voltage waveform for this phenomenon, and as a result, they found the following. I understood what happened.

(i) First, when we fix the welding current waveform and analyze the phenomenon, we find that the change in short-circuit voltage during the short-circuit period from short-circuit to arc regeneration corresponds to the change in the shape of melting transition of the wire electrode, and The change in the transition shape is determined by the wire feeding speed and the wicking phenomenon (surface tension) of the base material into the molten pool.

(ii) If the welding conditions such as shield glass, wire material, wire diameter, etc. are constant, the short circuit voltage V _snax immediately before arc regeneration is almost constant.

(iii) The short circuit period varies in a complex manner depending on four factors: wire feed speed, welding current, previous arc period, and disturbances such as hand shake.

(iv) The change in welding voltage during the arc period from arc regeneration to short circuit again corresponds to the wire feed speed, in other words the arc length and arc current.

(v) The arc duration is determined by the arc current value, in other words the rate at which a molten ball is formed at the tip of the wire electrode by the arc current, and the wire feeding speed.

(vi) The arc voltage V _anio just before a short circuit varies depending on the arc current value, but the shielding gas,
If the wire material and wire diameter are constant, the voltage value will be approximately constant.

Based on the above knowledge, the present invention has developed a system in which the rise of the welding voltage during the short-circuit period is set to V _snax , where the arc is regenerated after a predetermined time, and the fall of the welding voltage during the arc period is set to V _anio after a predetermined time. This was based on the idea that if the welding current value is controlled, the effects of changes in wire feed speed, hand shake of the torch, etc. can be compensated for.

An embodiment of the present invention will be described below with reference to FIG. FIG. 3 shows a control circuit 15 that constitutes a controller.
Since the main circuit is the same as that in FIG. 1, it will be omitted.

The output terminal of the voltage detector 9 is connected to the terminal X,
Terminal Y is connected to a trigger terminal of switching element 6. Although not shown in the figure, a drive circuit for driving the switching element is actually inserted between the trigger terminal and the trigger terminal. 16 is a comparison circuit for determining arc regeneration, 17 is a comparison circuit for determining short circuit, and comparison circuits 16 and 17
Configure the period judger. 18 and 19 are flip-flop circuits operated by the output signals of comparison circuits 16 and 17; 20 and 21 are integration circuits;
3 is an adder circuit that adds a constant voltage to the output signals of the integrating circuits 20 and 21, and 24 and 25 are the voltage value a input from the terminal X and the magnitude of the output signals V _sp and V _ap from the adder circuits 22 and 23. Comparison circuit for comparing
6 is a logical OR circuit which inputs the logical output of the comparator circuit 24 and the logical output of the comparator circuit 25 and makes a decision.

FIGS. 4A and 4B are diagrams showing welding voltage waveforms, welding current waveforms, and operating signal waveforms at various parts in the control circuit, respectively, when welding is performed in this embodiment. In addition, FIG. 4A shows the waveforms of various parts in the welding machine when the wire feeding speed is slow, and FIG. 4B shows the waveforms of various parts inside the welding machine when the wire feeding speed is fast. In A and B, a indicates the welding voltage waveforms _Vs and _Vp detected by the voltage detector 9,
The broken lines indicate the reference short circuit voltage waveform V _sp and the reference arc voltage waveform V _ap . b is the output waveform of the flip-flop 18, c is the output waveform of the flip-flop 19, d is the output signal of the adder circuit 22, that is, the reference short circuit voltage waveform V _sp , and e is the output waveform of the adder circuit 23, that is, the reference arc voltage waveform V _ap . , f is the output signal f obtained by ORing the logical output signals of the comparators 24 and 25 by the OR circuit 26, and g is the welding current waveform g that flows when the switching element is turned on and off according to the output signal f. are shown respectively.

Next, the operation of this embodiment will be explained.

In FIG. 3, the comparison circuits 16 and 17 are composed of variable resistors VR1 and VR2, resistors R1 to R10, diodes D1 to D4, zero point detectors A1 and A2, Zener diode Z1 and inverter A4, and are configured to detect voltage. A detection signal a from the device 9 is input. The variable resistor VR1 in the comparator is applied to this detection signal a.
A reference short-circuit voltage V _p and a reference arc voltage V _p set in advance by a variable resistor VR2 are added thereto and input to the zero point detectors A1 and A2. This zero point detector A1 outputs an L level signal when the input voltage passes through the zero point. Further, the zero point detector A2 emits an output signal of L level when the input voltage passes through the zero point. The output signal of the zero point detector A2 is inverted by an inverter A3, and the signal is input to flip-flop circuits 18 and 19. Further, the output signal of the zero point detector A1 is input to the flip-flop circuit 18.

Incidentally, the diodes D1 to D4 are for protection to prevent overvoltage from being input to the inputs of the zero point detectors A1 and A2. Also, Zener diodes Z1, Z2 and resistors R3, R8, R4, R9
The part consisting of is a hysteresis circuit to prevent malfunction of zero point determination due to input signal noise.

The output signal of the comparison circuit 16 is the flip-flop 1.
9 and a reset input R of flip-flop 18. The output signal of the comparator 17 is also connected to the set input S of the flip-flop 18.
and is input to the reset input R of the flip-flop circuit 19. Then, the signal waveform of the output signal Q of the flip-flops 18 and 19 is as shown in FIG. 4b.
c. Moreover, the signal waveform of the output signal becomes the inverted waveform of FIGS. 4b and 4c. The output signals Q of flip-flops 18 and 19 are input to the bases of transistors Tr1 and Tr2. The emitter voltage of these transistors Tr1 and Tr2 is
0 and 21 are input. In addition, the output signal is output from the analog switch SW in the integrating circuits 20 and 21.
1, is input to the gate of SW2. Integral circuit 2
0, 21 are resistors R13, R14, amplifiers A5, A
6. Consists of capacitors C1 and C2 and analog switches SW1 and SW2. Integral circuit 2
0, 21, transistors Tr1 and Tr2 are ON
When this state is reached, capacitors C1 and C2 are charged with a time constant represented by the product of R13 and C1 and a time constant represented by the product of R14 and C2, and the output voltage increases accordingly. Also, Tr1 and
When Tr2 turns OFF, analog switch SW
1 and SW2 operate, discharging the charges stored in the capacitors C1 and C2, and resetting the output voltage to zero voltage. The adder circuits 22 and 23 include a resistor R1
5~R22, amplifier A7, A8, inverter A9, A
10, and DC voltages V5 and V6 are added to the output signals of the integrating circuits 20 and 21. V5
The voltage value is the voltage immediately after a short circuit, and is approximately 1V.
level, V6 is the voltage value immediately after arc regeneration,
It is about 25V to 30V. Note that by changing the voltage value of V6 by changing the volume, the welding voltage can be changed arbitrarily, and the arc length can be changed freely. The output signals V _sp and V _ap of the adder circuits 22 and 23 are as follows:
The reference waveforms of the short circuit voltage waveform and the arc voltage waveform are input to the + terminals of the comparators 24 and 25, respectively, and the welding voltage signal a detected by the voltage detector 9 is input to the other - terminal. The reference waveform V _sp of this short-circuit voltage waveform is set so that it becomes the first predetermined signal value after a first predetermined time after the short-circuit time, that is, after a predetermined short-circuit period, that is, the short-circuit voltage V _snax immediately before the arc occurs, The reference waveform V _ap of the arc voltage waveform is set so that it becomes the second predetermined signal value, that is, the arc voltage V _anio immediately before short circuiting, after a second predetermined time after the arc occurs, that is, after a predetermined arc period. The comparator 24 compares the voltage of the welding voltage signal a during the short circuit period with the output signal V _sp (d in Fig. 4) of the adder 22, and if the welding voltage signal a is higher than the output signal V _sp , the voltage is set to L level. If the signal is low, an H level signal is generated. On the other hand, the comparator 25 compares the voltage during the arc period of the welding voltage signal a with the output signal V _ap (e in Fig. 4) of the adder 23, and if the voltage of the welding voltage signal a is higher than the output signal V _ap , the output signal is L. Generates a level signal, if low, H
It emits a level signal.

The output signals of the comparators 24 and 25 operating in this manner are input to the logical OR circuit 26,
If either of the 25 output signals is at H level, an H level output is generated. The output signal f of this OR circuit 26 is as shown in f in FIGS. 4A and 4B, respectively. According to this signal f, that is, when the output is at H level, switching element 6 is turned on, and conversely, when the output is at L level, switching element 6 is turned on.
When controlled to be OFF, the welding current g is
The welding voltage a becomes as shown in Fig. 4g, and the welding voltage a becomes as shown in Fig. 4a.

In order to make the explanation of the circuit in Fig. 4 easier to understand, the ripples of both the welding voltage a and the welding current g are schematically illustrated to be large, but in reality, by improving the sensitivity of voltage detection, the number of switching times can be increased. , and the ripples are getting smaller.

Furthermore, as can be seen from the comparison between A and B in Fig. 4, the welding voltage a remains approximately constant depending on the wire feeding speed, and the number of times the switching element 6 is switched automatically increases depending on the wire feeding speed. , the rise and fall of the welding current are determined.

Furthermore, by increasing the resistor R13 or capacitor C1 and the resistor R14 or capacitor C2 according to the increase in wire feeding speed with such control, the short circuit period and arc period can be lengthened, and more stable welding can be performed. There may be cases where

In the above embodiments, the control circuit was constructed using operational amplifiers and logic circuit elements, but it goes without saying that an equivalent control circuit can also be constructed using a microcomputer or the like. The preset short-circuit period (first predetermined time), arc period (second predetermined time), reference short-circuit voltage waveform, and reference arc voltage waveform are stored in the computer's storage device, and the period is determined by performing logical operations on the computer. It can realize the functions of a device and a controller.

This invention detects the point of short circuit between the wire electrode and the base metal from the welding voltage value between the wire electrode and the base metal, and applies a welding current to burn out the wire electrode from that point, so that the wire electrode burns out. Welding is performed by repeating the operation of reducing the welding current and shorting again from the point at which an arc is _generated . (1st
(predetermined signal value), arc voltage value immediately before re-shorting Va _nio
(second predetermined signal value), and after a short circuit period (first predetermined time) at the time of short circuit, short circuit release voltage value Vs _nax (first
A reference short-circuit voltage waveform is set such that a predetermined signal value is reached, and the arc period (second
A reference arc voltage waveform is set so that the arc voltage value Va _nio (second predetermined signal value) immediately before the short circuit is reached after a predetermined time), and a voltage detector that detects the welding voltage is set based on the detected value of this voltage detector. a period determiner for determining whether welding is a short circuit period or an arc period;
When welding is in a short-circuit period, the welding current is controlled on-off so that it changes along the reference short-circuit voltage waveform,
The controller is equipped with a controller that controls the welding current on and off so that it changes along the reference arc voltage waveform when welding is in the arc period. Even when the speed is set, the short circuit current rise and arc current automatically correspond to the wire feeding speed, so welding can always be performed with regular short circuit transitions and arc length changes.
Welding has become easier.

Furthermore, even if the welding torch shakes, the welding voltage can be kept almost constant, and large spatter that occurs during arc regeneration can be reduced, making it possible to perform better welding.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing a short-circuit transitional arc welding machine according to the prior art, Figure 2a is its current waveform diagram, Figure b is its voltage waveform diagram, Figure c is a diagram showing the welding state, and Figure 3 is a diagram showing the welding state. A control circuit diagram of an embodiment of the present invention, FIGS. 4A and 4B, are waveform diagrams of various parts in this embodiment. In the figure, 1 is a wire electrode, 2 is a base material, 3 is a wire feeding motor, 5 is a DC power supply circuit, 6 is a switching element, 7 is a reactor, 8 is a flywheel diode, 9 is a voltage detector, 10, 11
is a comparator, 13 is a switch command circuit, 14 is an auxiliary power supply, 15 is a control circuit, 16 and 17 are comparison circuits,
18, 19 are flip-flop circuits, 20, 21
is an integration circuit, 22, 23 is an addition circuit, 24, 25
2 is a comparison circuit, and 26 is a logical OR circuit. In addition,
The same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. Detecting the point of short circuit between the wire electrode and the base metal from the welding voltage value between the wire electrode and the base metal, applying a welding current to burn out the wire electrode from that point, and In welding where the welding current is reduced from the point at which the electrode burns out and an arc is generated, the welding current is repeatedly shorted again, the short circuit period (first predetermined time), arc period (second predetermined time), and short circuit release are determined in advance. The voltage value Vs _nax (first predetermined signal value) and the arc voltage value Va _nio (second predetermined signal value) immediately before re-short circuit are set, and the short circuit release voltage value Vs is set after the short circuit period (first predetermined time) at the time of the short circuit. _nax (1st
A reference short-circuit voltage waveform is set such that a predetermined signal value) is obtained, and the arc voltage value immediately before a short-circuit is set after the above-mentioned arc period (second predetermined time) from the point of arc occurrence.
A voltage detector is used to detect the welding voltage by setting a reference arc voltage waveform such that Va _nio (second predetermined signal value). a period determiner for determining whether the welding is in the short-circuit period, controls the welding current on-off so that it changes along the reference short-circuit voltage waveform, and when the welding is in the arc period; A short-circuit transfer arc welding machine characterized by comprising a controller that controls the welding current on and off so that it changes along the reference arc voltage waveform. 2. The short-circuit transitional arc welding machine according to claim 1, wherein the reference short-circuit voltage waveform of the short-circuit period and the reference arc voltage waveform of the arc period are set according to the wire feeding speed. 3 The period determiner and the controller are configured with a computer having a storage device, and the preset short circuit period (first predetermined time), arc period (second predetermined time), reference short circuit voltage waveform, and reference arc voltage waveform are set in advance as described above. 3. The short-circuit transitional arc welding machine according to claim 1 or 2, wherein the short-circuit transitional arc welding machine is stored in a storage device of a computer.