JP3458632B2 - Welding voltage detection method and arc welding machine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding voltage detecting method and an arc welding machine for controlling a welding output by generating an arc between a welding wire and a welding base material (work).

[0002]

2. Description of the Related Art In recent years, in a consumable electrode type arc welding machine, in order to suppress the occurrence of spatter, a so-called loose neck detection control is performed to predict that a short circuit will be opened and reduce the welding current immediately before opening the short circuit. Then, the welding current at the moment when the arc was regenerated was reduced to suppress the arc force.

FIG. 4 shows the relationship between the welding phenomenon and the welding current detection waveform and the welding voltage detection waveform in arc welding generally involving a short circuit.

In FIG. 4, generally, as a welding phenomenon,
An arc period ((a), (e)) in which an arc is generated and a droplet is formed on the wire tip, and a short-circuit period ((b), (c)) in which the droplet at the wire tip short-circuits to the work ，
(D)). One of the causes of generation of spatter in such a welding phenomenon is that the droplet or molten pool is blown off by the arc force at the moment the short circuit is opened. This arcing force becomes larger as the welding current ((g1), (g2)) at the moment when the short circuit is opened becomes higher. Therefore, in recent years, it is necessary to detect the moment when the short circuit is opened and lower the welding current. It has been considered to control. Next, the configuration of the conventional consumable electrode type arc welding machine will be described with reference to FIG.

In FIG. 5, 1 is an AC power source, 2 is a first rectifying element, 3 is a first switching element, 4 is a main transformer, 5
Is a second rectifying element, 7 is a resistor, 8 is a third switching element, 9 is a reactor, 10 is an output terminal of a welding machine, 11 is a tip, 12 is a welding wire, 13 is a work, 14 is a welding voltage detection circuit, 16 Is a differentiating circuit, 17 is a voltage setting circuit, 1
Reference numeral 8 is a comparison circuit, 19 is a short circuit / arc determination circuit, 20 is a logical operation circuit, 21 is a delay circuit, and 27 is a control circuit.

The operation of this arc welding machine will be described below. The AC power supply 1 is rectified by the first rectifying element 2, and the output of the first rectifying element 2 is switched by the first switching element 3 in order to obtain an output suitable for welding, and power is supplied to the welding load. It is input to the transformer 4. The output of the main transformer 4 is rectified by the second rectifying element 5, and a reactor 9 connected in series between the second rectifying element 5 and the output terminal 10, and between the second rectifying element 5 and the reactor 9 Alternatively, the second switching element 8 connected in series between the reactor 9 and the output terminal 10 and the second switching element 8
It is supplied between the welding wire 12 and the work 13 through the resistor 7 connected in parallel to the switching element 8.

The welding voltage detecting circuit 14 detects the welding voltage and delays the output of the welding voltage detecting circuit 14, and the output of the delay circuit 21 is a differentiating circuit 16.
Is input to and differentiated. Further, the output of the differentiating circuit 16 and the output of the voltage setting circuit 17 are input to the comparing circuit 19, and when the output value Vi of the differentiating circuit 16 becomes larger than the output value Ve of the voltage setting circuit 17, the comparing circuit unit 1
The second switching element 8 is connected to the logical operation circuit 20 from 9
The signal is output so as to perform FF. Further, a short circuit / arc determination circuit 18 determines a short circuit or an arc from the output of the welding voltage detection circuit 14, and a logical operation circuit 20 outputs the output of the comparison circuit 19 and the short circuit / arc determination circuit 1.
The output of the second switching element 8 is logically operated with the output of the second switching element 8 as an input and the drive signal Vf of the second switching element 8 is output.

FIG. 6 shows the signal waveform of each part shown in FIG. 5. The above operation will be described in more detail with reference to FIG.

Since the ripple voltage signal synchronized with the switching of the first switching element 3 is superimposed on the welding voltage detection signal Va, if the welding voltage detection signal Va is directly differentiated, it is short-circuited with the differential signal at the rise of the ripple voltage signal. Since the differential signal of the voltage that gradually rises from the occurrence of the droplet to the constriction of the droplet and the differential signal of the voltage that rises when the droplet constricts are mixed, the conventional consumable electrode arc welding machine is The detection signal Va is converted into the delay signal Vh by the delay circuit 21 which is a filter, and the ripple voltage signal superimposed on the welding voltage detection signal is suppressed. The comparator circuit 19 compares the differential signal Vi obtained by differentiating the delay signal Vh by the differentiating circuit 16 with the predetermined comparison voltage signal Ve set by the voltage setting circuit 17, and detects the welding constricted signal Vf. Is output. The logical operation circuit 20 is
This signal and the short circuit / arc determination signal VAS for determining a short circuit or an arc by the short circuit / arc determination circuit 18 are logically operated to stop the neck detection control at the same time when the short circuit is released.

[0010]

When the consumable electrode type arc welding machine detects and controls the welding voltage, as shown in FIG. 6, the welding voltage detection signal Va supplies an output suitable for the welding load. 1 A ripple voltage signal due to switching synchronized with the switching of the switching element 3 is superimposed. In the conventional consumable electrode type arc welder, a delay signal Vh obtained by delaying the welding voltage detection signal Va using a filter is used.
Suppresses the ripple voltage signal. In this case, the instantaneous change appearing in the welding voltage waveform could not be reliably captured. Therefore, the instantaneous welding voltage indicating the welding phenomenon cannot be accurately detected, and the droplet cannot be accurately detected at the instant.

Further, when detecting whether the state of the arc is during the arc period or during the short circuit period when the wire is short-circuited by contact with the work, the variation in the distance between the tip and the work and the welding current at the time of the short circuit are high. In some cases, the accuracy cannot be accurately determined due to various fluctuations such as an increase in the value.

The present invention solves the above problems, and a welding voltage detection method for suppressing a ripple voltage signal superimposed on a welding voltage detection signal without delay and without time delay, and welding without time delay. By detecting the voltage signal, it is possible to accurately detect whether it is during an arc period or during a short circuit period, reliably detect the moment when the droplet is constricted, and perform neck detection control reliably to suppress welding current. It is an object of the present invention to provide an arc welder that suppresses the generation of spatter.

[0013]

In order to achieve the above object, the welding voltage detecting method of the present invention provides a first rectifying element for rectifying an AC power source and an output suitable for welding. A first switching element for switching the electric power to a welding load, a second rectifying element for rectifying the output of the main transformer, a welding voltage detecting circuit for detecting a welding voltage, Switching of the first switching element, which has a differential amplifier circuit for calculating a difference between a voltage signal synchronized with switching of one switching element and an output signal of the welding voltage detection circuit, and is superimposed on the output signal of the welding voltage detection circuit The ripple voltage signal due to is removed.

The arc welding machine of the present invention further comprises: a first rectifying element for rectifying an AC power source; a first switching element for switching the output of the first rectifying element to obtain an output suitable for welding; A main transformer that supplies electric power to a load and is provided with a secondary side auxiliary winding, a second rectifying element that rectifies the output of the main transformer, and a second rectifier that rectifies the output of the auxiliary winding of the main transformer. 3 rectifying element, a second switching element connected in series between the output terminal side and the output terminal of the second rectifying element, a welding voltage detecting circuit for detecting a welding voltage, an output of the welding voltage detecting circuit and the A differential amplifier circuit that calculates the difference between the outputs of the third rectifying element, a short-circuit / arc determination circuit that determines a short circuit or an arc from the output of the differential amplifier circuit, and a differentiation circuit that differentiates the output of the differential amplifier circuit. And the voltage setting circuit Comparing the output of the differentiating circuit and the output of the voltage setting circuit, and outputting so as to turn off the second switching element when the output value of the differentiating circuit is larger than the output value of the voltage setting circuit, A comparison circuit that outputs so that the second switching element is turned on when the output value of the differentiating circuit is smaller than the output value of the voltage setting circuit, and the output of the comparison circuit and the output of the short-circuit / arc determination circuit are logical When the output of the short-circuit / arc determination circuit is in the short-circuit period by calculation, the second switching element is turned on / off according to the output of the comparison circuit,
And a logical operation circuit for turning on the second switching element when the output of the short-circuit / arc determination circuit is in the arc period.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The welding voltage detecting method of the present invention comprises a differential amplifier circuit for calculating the difference between the voltage signal synchronized with the switching of the first switching element and the output signal of the welding voltage detecting circuit. It has an effect of removing the ripple signal due to the switching of the first switching element, which is superimposed on the output signal of the welding voltage detection circuit.

The arc welding machine of the present invention uses a differential amplifier circuit for calculating the difference between the outputs of the third rectifying elements for rectifying the output of the auxiliary winding of the main transformer, and the output of the differential amplifier circuit. To suppress the ripple voltage superimposed on the welding voltage detection signal by having a short circuit / arc determination circuit for determining a short circuit or an arc and a differentiating circuit for differentiating the output of the differential amplifier circuit, the welding voltage is suppressed. The rectified signal obtained by rectifying the output from the auxiliary winding of the main transformer, which is a signal synchronized with the ripple voltage signal from the detection signal, is differentially amplified by the differential amplifier circuit.

In this case, the output signal of the differential amplifier circuit is not delayed with respect to the welding voltage detection signal, there is no time delay with respect to the welding voltage detection signal, and it is possible to reliably detect when the droplet is squeezed. Have an effect. Hereinafter, an arc welder that implements the welding voltage detection method of the present invention will be described in detail with reference to FIGS. 1 to 4. That is, the arc welding machine according to the present embodiment includes the first rectifying element 2 that rectifies the AC power source 1, and the first switching element 3 that switches the output of the first rectifying element 2 to obtain an output suitable for welding. And a main transformer 4a that insulates the output of the switching element 3 to supply electric power to the welding load and also has an auxiliary winding on the secondary side.
And a second rectifying element 5 for rectifying the output of the main transformer 4a
A reactor 9 connected in series between the second rectifying element 5 and the output terminal 10, and a reactor 9 connected in series between the second rectifying element 5 and the reactor 9 or between the reactor 9 and the output terminal 10. Two switching elements 8, a resistor 7 connected in parallel to the second switching element 8, a welding voltage detection circuit 14 for detecting a welding voltage, a third rectifying element 6 for rectifying the output of the auxiliary winding, A differential amplifier circuit 15 that differentially amplifies the output of the welding voltage detection circuit and the output of the third rectifying element, a differentiation circuit 16 that differentiates the output of the differential amplification circuit 15, and an output of the differentiation circuit 16. A short-circuit / arc determination circuit 18 for further determining a short circuit or an arc, a voltage setting circuit 17, a comparison circuit 19 for comparing the output of the differentiating circuit 16 and the output of the voltage setting circuit 17, and an output of the comparison circuit 19. A logical operation circuit 20 that logically operates the output of the short-circuit / arc determination circuit 18, a control circuit 27 that outputs a drive signal of the switching element 3 from the output of the short-circuit / arc determination circuit 18 and the output of the comparison circuit 19. It is composed of. Further, the signal Vb obtained by rectifying the signal from the auxiliary winding of the main transformer 4a can be replaced with a signal that is synchronized with the drive signal of the first switching element 3, and the drive signal Vg of the first switching element 3 or the second rectifying element. 5 may be an input signal or an output signal. In addition, 11 to 13 are the same chips, welding wires, and works as in the conventional case.

FIG. 2 shows the waveform of the output signal of each part of FIG. The operation will be described below. The welding voltage detection circuit unit 14
Detects a welding voltage and outputs a welding voltage detection signal Va. In order to suppress the ripple voltage signal superimposed on the welding voltage detection signal Va, the main transformer 4a which is a signal synchronized with the ripple voltage signal from the welding voltage detection signal Va.
The rectified signal Vb obtained by rectifying the output from the auxiliary winding is differentially amplified by the differential amplifier circuit 15. A specific example of the differential amplifier circuit 15 is shown in FIG. FIG. 3 shows an operational amplifier 22 and a resistor 2.
It is a general differential amplifier circuit using 3 to 26 and can be easily realized. Then, the output V of the differential amplifier circuit 15
c is differentiated by the differentiating circuit unit 17 to output a differential signal Vd,
The increase in welding voltage when the droplet is constricted is made a signal that can be distinguished from when the droplet is constricted. Further, the short circuit / arc determination circuit 18 receives the output signal Vc of the differential amplifier circuit 15 as an input and compares it with a reference voltage in the short circuit / arc determination circuit 18,
The output signal VAS of either short circuit or arc is output.

The comparison circuit 19 compares the output signal Vd of the differentiating circuit 16 with the output signal Ve of the voltage setting circuit 17, and when the output signal Vd of the differentiating circuit 16 becomes larger than the output signal Ve of the voltage setting circuit 17, it becomes L level. Signal of the differentiating circuit 1
When the output signal Vd of 6 becomes smaller than the output signal Ve of the voltage setting circuit 17, an H level signal is output to the logical operation circuit 20. Further, the logical operation circuit 20 logically operates the main power of the comparison circuit 19 and the output VAS of the short circuit / arc determination circuit unit 18, and the output of the comparison circuit 19 is shorted at the L level and the output signal VAS of the arc determination circuit 18 is short circuited. In case of a period,
When the second switching element 8 is turned off and the output of the comparison circuit 19 is at the H level, the short circuit / arc determination circuit 18
When the output signal VAS of No. 2 is in the arc period, the drive signal Vf to the second switching element 8, which turns on the second switching element 8, that is, the neck detection signal is output. In this case, since the output signal Vc of the differential amplifier circuit 15 is not delayed with respect to the welding voltage detection signal Va and there is no time delay with respect to the welding voltage detection signal Va, the time when the droplet is squeezed is ensured. It has an action that can be detected. In FIG. 4, the welding currents g1 and g2 when the short circuit is opened represent the case where the neck detection control is not performed, respectively, but in the present embodiment, the welding current g2 should be surely reduced when the droplet is constricted. Therefore, the generation of spatter can be suppressed.

Although this effect has been described in the neck detection control for detecting the constriction of the wire tip, the short-circuit transfer type CO
2 In welding, etc., when detecting whether it is simply during the arc period or during the short circuit period when the wire tip is short-circuited to the base material, it is possible to detect accurately without being affected by the ripple voltage signal due to switching. Is something that can be done.

[0021]

As described above, according to the welding voltage detecting method of the present invention, the difference between the voltage signal synchronized with the first switching element for switching to obtain the welding output and the output of the welding voltage detecting circuit is calculated. By using the dynamic amplification circuit, it is possible to remove the ripple voltage signal superimposed on the welding voltage detection signal from the welding voltage detection signal without delay and to select the welding voltage signal without time delay. is there. Further, according to the present invention, the influence of the ripple voltage signal is detected when it is detected during the arc period or the short circuit period when the wire tip is short-circuited to the base material due to the use of the differential amplifier circuit. It is possible to detect accurately without receiving the arc and to reliably detect the moment when the droplet is constricted, so it is possible to reduce the welding current at the moment when the arc re-occurs and suppress the generation of spatter. It has an excellent effect of maintaining the welding workability.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an arc welder in which a welding voltage detection method of the present invention is implemented.

2A is a waveform diagram of an output signal of the welding voltage detection circuit, FIG. 2B is a waveform diagram of a rectification signal of an auxiliary winding of the main transformer, and FIG. 2C is a waveform diagram of an output signal of the differential amplifier circuit. d) Waveform diagrams of the output signal of the differentiation circuit and the output signal of the voltage setting circuit (e) Waveform diagram of the output signal of the short circuit / arc determination circuit (f) Waveform diagram of the drive signal of the second switching element

FIG. 3 is a circuit configuration diagram of the differential amplifier circuit.

FIG. 4 is a timing chart showing a relationship between a welding voltage waveform and a welding current waveform with respect to droplet transfer.

FIG. 5 is a block circuit diagram of a conventional arc welder.

6A is a waveform diagram of a conventional welding voltage detection signal, FIG. 6B is a waveform diagram of the same delayed signal, and FIG. 6C is a waveform diagram of an output signal of the differentiating circuit and an output signal of the voltage setting circuit. Waveform diagram of the output signal of the arc generating circuit (e) Waveform diagram of the drive signal of the second switching element

[Explanation of symbols]

3 First switching element 4a Main transformer 8 Second switching element 14 Welding voltage detection circuit 15 Differential amplifier circuit 16 Differentiation circuit 17 Voltage setting circuit 18 Short circuit / arc judgment circuit 19 Comparison circuit 20 Logical operation circuit 27 Control circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields investigated (Int.Cl. ⁷ , DB name) B23K 9/073 545 B23K 9/073 560

Claims (2)

(57) [Claims] Claim: What is claimed is: 1. A welding voltage detecting method for detecting an output voltage of a welding machine and performing welding control, comprising: rectifying an AC power source.
A rectifying element, a first switching element that switches the output of the first rectifying element to obtain an output suitable for welding, a main transformer that supplies electric power to a welding load, and rectifies the output of the main transformer. A second rectifying element, a welding voltage detecting circuit for detecting a welding voltage, and a differential amplifier circuit for calculating a difference between a voltage signal synchronized with switching of the first switching element and an output signal of the welding voltage detecting circuit. The welding voltage detecting method is characterized in that the ripple signal due to the switching of the first switching element, which is superimposed on the output signal of the welding voltage detecting circuit, is removed. 2. A first rectifying element for rectifying an AC power source, a first switching element for switching an output of the first rectifying element to obtain an output suitable for welding, and a power supply for a welding load and 2 A main transformer provided with a secondary auxiliary winding, a second rectifying element for rectifying the output of the main transformer, a third rectifying element for rectifying the output of the auxiliary winding of the main transformer, and the second A second switching element connected in series between the output side of the rectifying element and the output terminal; a welding voltage detecting circuit for detecting a welding voltage; and a difference between the output of the welding voltage detecting circuit and the output of the third rectifying element. A differential amplifier circuit for calculating, a short circuit / arc determination circuit for determining a short circuit or an arc from the output of the differential amplifier circuit, a differentiating circuit for differentiating the output of the differential amplifier circuit, a voltage setting circuit, and the differentiating circuit. The output of the circuit and the voltage setting The outputs of the differentiating circuits are compared, and when the output value of the differentiating circuit is larger than the output value of the voltage setting circuit, the second switching element is turned off, and the output value of the differentiating circuit is set to the voltage setting value. When it is smaller than the output value of the circuit, the second switching element is O
When the output of the short circuit / arc determination circuit is logically operated and the output of the short circuit / arc determination circuit is a short circuit period,
The second switching element is turned on / off according to the output of the comparison circuit, and when the output of the short-circuit / arc determination circuit section is in the arc period, the second switching element is turned on.
An arc welder equipped with a logical operation circuit unit for turning on N.