JPS6253261B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a TIG arc welding device that performs welding by periodically and alternately changing the welding current into a pulse current and a base current, while keeping the arc voltage constant.
The present invention relates to an arc voltage control device that aims to equalize heat input to a base material during welding.

Generally, this type of TIG arc welding equipment includes a pulse switching signal for periodically and alternately changing the welding current into a pulse current and a base current;
There is a relationship between welding current and arc voltage as shown in FIG.

As shown in FIG. 1, the arc voltage changes in a complicated manner. The following two points can be considered as factors that cause this arc voltage waveform to change in a complicated manner.

There is a relationship between welding current and arc voltage as shown in the arc voltage current characteristic curve in FIG. 2, and the arc voltage changes in a complicated manner depending on the welding current.

When the welding current is switched from a pulsed current to a base current, or from a base current to a pulsed current, it is affected by the transient response of the welding current.

In addition, when welding in a state where the base material is tilted, if the welding current is small, for example 20A or less, the arc voltage waveforms during up welding and down welding are significantly different as shown in Figure 3. . This is because the molten metal flows in response to the slope of the base metal, and the arc point (anode) on the base metal side moves accordingly, and the non-consumable electrode
This is because the arc length changes even if the distance between the base materials is constant.

As mentioned above, in general TIG arc welding equipment, the arc voltage can be adjusted by switching the welding current between a pulse current and a base current, and by determining whether to perform upward welding or downward welding when the base material is inclined. This resulted in a large change in the heat input to the base metal, resulting in uneven welding quality.

In order to solve this drawback, conventionally, the fourth
A device as shown in the figure has been proposed in which a welding torch holding a non-consumable electrode is moved up and down in accordance with the arc voltage.

In Fig. 4, 1 is a welding torch holding a non-consumable electrode, 2 is a base material, 3 is an arc voltage detection device that detects the arc voltage generated between the non-consumable electrode and the base material 2, and 4 is a reference voltage generator. A comparator 6 compares the reference voltage outputted from the arc voltage detector 5 with the arc voltage detected by the arc voltage detection device 3 and outputs the difference voltage between the two voltages. 8 is a drive circuit driven by the output of the amplifier 6, and 9 is a motor that moves the welding torch 1 up and down in accordance with the output of the drive circuit.

In the above configuration, the arc voltage generated between the non-consumable electrode and the base material 2 is detected by the arc voltage detection device 3, this arc voltage is compared with a reference voltage by the comparator 4, and the output of the comparator 4 is The differential voltage is input to an amplifier 6 where it is integrated and amplified. This amplifier 6
The output of is input to the drive circuit 8, and this drive circuit 8
Based on the output, the motor 9 is rotated to move the welding torch 1 up and down to keep the arc voltage constant.

However, when the welding current is periodically and alternately switched between a pulse current and a base current by a power supply (not shown), the arc voltage changes drastically as shown in FIG. Therefore, in the apparatus shown in FIG. 4, the welding torch 1 vibrates up and down depending on the arc voltage detected by the arc voltage detection device 3, making it difficult to keep the arc voltage constant.

In order to eliminate the vertical vibration of the welding torch 1, it is possible to install a filter circuit in the arc voltage detection device 3 to remove complicated fluctuations in the voltage waveform, but this would cause a very large time delay in detection, and the arc voltage It becomes difficult to quickly detect and respond to changes in arc length or changes in arc length.

The present invention solves the above-mentioned drawbacks of the conventional device, and maintains the arc voltage constant by moving the welding torch up and down only during periods when the arc voltage changes very little, thereby making welding possible by keeping the heat input to the base metal constant during welding. This is to ensure uniform quality.

Embodiments of the present invention will be described below with reference to FIGS. 5 to 9.
This will be explained with reference to the figures.

FIG. 5 is a circuit diagram of an arc voltage control device showing an embodiment of the present invention, and the same components as those shown in FIG. 4 are designated by the same numbers and their explanations will be omitted.

10 is a welding power source connected to the welding torch 1 and the base metal 2; 11 is a welding power source that starts outputting a predetermined time _T1 after inputting a pulse switching signal Ps for switching the welding current from a base current to a pulse current, and performs welding. A pulse switching signal synchronous delay circuit that stops outputting when a pulse switching signal Ps for switching the current from a pulse current to a base current is input; 12 is a relay that is turned ON by the output of the pulse switching signal synchronous delay circuit 11; 13 is a relay The first normally open contact 12 is connected in series to the capacitor 7 and constitutes a feedback circuit for the amplifier 6. The second normally open contact 14 is connected between the amplifier 6 and the drive circuit 8. There is. There is a relationship between the pulse switching signal Ps and the output of the relay 12 as shown in FIG.

In the above configuration, the arc voltage between the non-consumable electrode held by the welding torch 1 and the base material 2 is constantly detected by the arc voltage detection device 3, and a substantially proportional voltage that is substantially proportional to the arc voltage is output. Comparator 4
Then, the reference voltage generated from the reference voltage generator 5 and the substantially proportional voltage output from the arc voltage detection device 3 are compared, and the difference voltage between the two voltages is output.

In this state, when a pulse switching signal for switching the welding current from the base current to the pulse current is input to the pulse switching signal synchronization delay circuit 11,
Output is started after a predetermined time _T1 after this pulse switching signal Ps is input, the relay 12 is operated, the first normally open contact 13 and the second normally open contact 14 are closed, and the amplifier 6 and the drive circuit 8 are closed. to drive.
That is, when the first normally open contact 13 and the second normally open contact 14 are closed, the amplifier 6 integrates and amplifies the differential voltage that is the output of the comparator 4, and drives the output through the second normally open contact 14. Input to circuit 8. The drive circuit 8 controls the rotation of the motor 9 based on the output of the amplifier 6 to move the welding torch 1 up and down so that the arc voltage is constant.

Next, when the pulse switching signal Ps for switching the welding current from the pulse current to the base current is input to the pulse switching signal synchronous delay circuit 11, the pulse switching signal synchronous delay circuit 11 stops outputting, and the relay 1
2 is OFF. Therefore, the first normally open contact 13 and the second normally open contact 14 are opened, and the drive circuit 8 stops driving. Therefore, the motor 9 stops rotating,
The vertical movement of the welding torch 1 stops.

In this way, in this embodiment, the welding current is switched from the base current to the pulse current for a predetermined period of time.
Since the drive circuit 8 is driven after T ₁ and stopped when the welding current switches from the pulse current to the base current, the welding current is large and stable while the drive circuit 8 is being driven. Since this period is a period in which the arc voltage changes little, the arc voltage can be kept constant without causing the welding torch 1 to vibrate up and down. Further, since the motor 9 only needs to operate during a period when the arc voltage changes little, a servo motor with a small time constant and a fast response speed can be used.

Note that the predetermined time _T1 is preferably a period from when the welding current is switched from the base current to the pulse current until the change in arc voltage becomes small, and although it varies depending on the welding power source 10, it is usually 10 to 40 msec.
It is.

Furthermore, in this example, the welding current is large;
The arc voltage is controlled to be constant only during the stable period, and no control is performed during other periods. However, during the base current, the current value is small and the heat input to the base material 2 is small, so There is little influence on the state of weld bead formation, and good welding results can be obtained by controlling only the pulse current.

The above embodiment is for a case where the base current is small, but if the base current is large, e.g.
If it is 20A or more, the arc voltage is stable. The relationship between the welding current waveform and welding voltage waveform at this time is shown in FIG. If the base current is quite large and the arc voltage at the base current is stable, it will be better to control the welding torch to move up and down to keep the arc voltage constant even at the base current. Welding results are obtained.

An embodiment of the present invention that performs control even when the base current is applied will be described below with reference to FIGS. 8 and 9.

In FIG. 8, components that are the same as those shown in FIGS. 4 and 5 are given the same reference numerals and their explanations will be omitted.

15 is a reference voltage generator for pulse current that generates a reference voltage for pulse current, 16 is a reference voltage generator for base current that generates a reference voltage for base current, and 17 is a generator that converts welding current from base current to pulse current. a third contact that is closed by a pulse switching signal Ps for switching from the pulse current to the base current and opened by the pulse switching signal Ps for switching from the pulse current to the base current;
18 is closed by a pulse switching signal Ps for switching the welding current from a pulse current to a base current,
This is a fourth contact that opens in response to a pulse switching signal Ps for switching from base current to pulse current.

Reference numeral 19 denotes a welding current detection device for detecting a welding current, and when the welding current detected by this welding current detection device 19 is larger than a predetermined current value (for example, 20A), the first relay 20 is activated and its normally open contact is The fifth contact 21 is closed. 22 starts outputting a predetermined time _T1 after the input of the pulse switching signal Ps for switching the welding current from the base current to the pulse current, and outputs the pulse switching signal Ps for switching the welding current from the pulse current to the base current. Pulse switching signal synchronization delay circuit for pulse current that stops output when input, 23 is a pulse switching signal for switching the welding current from pulse current to base current
The output starts after a predetermined time T1 after Ps is input through the fifth contact ₂₁ , and when a pulse switching signal Ps for switching the welding current from the base current to the pulse current is input through the fifth contact. This is a base current pulse switching signal synchronization delay circuit that stops output.

24 operates when the output of the pulse switching signal synchronous delay circuit 22 for pulse current or the output of the pulse switching signal synchronous delay circuit 23 for base current is input, and closes the first normally open contact 13 and the second normally open contact. to be accomplished.

In the above configuration, when the welding current is switched from the base current to the pulse current, the third contact is closed.
The arc voltage between the non-consumable electrode held in the welding torch 1 and the base metal 2 is constantly detected by the arc voltage detection device 3, and a substantially proportional voltage that is substantially proportional to the arc voltage is output and input to the comparator 4. Ru. This comparator 4 compares the pulse current reference voltage outputted from the pulse current reference voltage generator 15 and input via the third contact 17 with the substantially proportional voltage, and outputs the difference voltage between the two voltages. Ru.

On the other hand, the welding current detected by the welding current detection device 19 is larger than the predetermined current value when it is a pulse current,
The first relay 20 operates and the fifth contact 21 closes. However, the base current pulse switching signal synchronization delay circuit 23 does not output since the pulse switching signal Ps for switching the welding current from the pulse current to the base current is not input. The pulse switching signal synchronization delay circuit 22 for pulsed current outputs a predetermined time _T1 after the pulse switching signal for switching the welding current from the base current to the pulsed current is input. This output operates the second relay 24, which closes the first normally open contact 13 and the second normally open contact 14. By closing the first normally open contact 13, the amplifier 6 integrates and amplifies the differential voltage that is the output of the comparator 4, and inputs the output to the drive circuit 8 via the second normally open contact 14. The drive circuit 8 controls the rotation of the motor 9 based on the output of the amplifier 6 to move the welding torch 1 up and down so that the arc voltage is constant.

Next, when the base current is applied, a pulse switching signal for switching the welding current from the pulsed current to the base current opens the third contact 17 and closes the fourth contact.
The comparator 4 compares the base current reference voltage output from the base current reference voltage generator 15 and input via the fourth contact 18 with the substantially proportional voltage, and outputs the difference voltage between the two voltages.

On the other hand, when the welding current detected by the welding current detection device 19 is smaller when the base current is used than when it is a pulse current, but is larger than a predetermined current value (for example, 20A), the first relay 20 operates and the fifth contact 21 is Close. In response to the pulse switching signal for switching the welding current from the pulse current to the base current, the pulse switching signal synchronization delay circuit 22 stops outputting at pulse current, the second relay 24 stops operating, and the first normally open contact 13 and The second normally open contact 14 is opened and the drive circuit 8 stops driving. Therefore, the motor 9 stops rotating and the welding torch 1 stops moving up and down.
When this pulse switching signal is input to the base current pulse switching signal synchronization delay circuit 23 via the fifth contact 21, an output is performed after a predetermined time _T1 after the pulse switching signal is input, and the second relay 24 , the first normally open contact 13 and the second normally open contact 14
Close. By closing the first normally open contact 13, the amplifier 6 integrates and amplifies the differential voltage that is the output of the comparator 4, and inputs the output to the drive circuit 8 via the second normally open contact 14. The drive circuit 8 controls the rotation of the motor 9 based on the output of the amplifier 6 to move the welding torch 1 up and down so that the arc voltage is constant.
The relationship between the pulse switching signal and the output of the second relay 24 in this case is shown in FIG.

Moreover, when the welding current detected by the welding current detection device 19 is smaller than the predetermined current value, the first relay 20 does not operate and the fifth contact 21 opens. Therefore, the base current pulse switching signal synchronization delay circuit 23 does not output, the second relay 24 does not operate, the first normally open contact 13 and the second normally open contact 14 are open, and the motor 9 does not rotate. . Therefore, the welding torch 1 does not move up and down.

As described above, in this embodiment, if the welding current at the base current is larger than the predetermined current value, the drive circuit 8 is stopped when the base current is switched to the pulse current, and the drive circuit 8 is stopped after the predetermined time _T1 . The circuit 8 is driven, and when the pulse current is switched to the base current, the drive circuit 8 is stopped, and the drive circuit 8 is driven after a predetermined time _T1 . In addition, if the welding current at the base current is smaller than the predetermined current value, the drive circuit 8 starts driving after a predetermined time _T1 after switching from the base current to the pulse current, and the pulse current changes from the base current to the base current. When switched, the drive circuit 8 stops driving.

In this way, the period in which the drive circuit 8 is driven is a period in which the welding current is greater than the predetermined current value and the arc voltage is stable, so the welding torch 1 is not caused to vibrate up and down. In addition, the arc voltage can be kept constant.

Further, since the motor 9 only needs to operate during a period when the arc voltage changes little, a servo motor with a small time constant and a fast response speed can be used.

As described above, according to the present invention, the drive circuit is driven to move the welding torch up and down only during periods when the welding current is large and the arc voltage is stable, so vibration of the welding torch can be prevented and the arc voltage can be kept constant. can be kept.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between pulse switching signals, welding current waveforms, and arc voltage waveforms. Figure 2 is an arc voltage/current characteristic diagram. Figures 3 a and b are arcs during uphill and downhill welding. Voltage waveform diagram, Fig. 4 is a circuit diagram of a conventional arc voltage control device, Fig. 5 is a circuit diagram of an arc voltage control device showing the first embodiment of the present invention, and Fig. 6 a and b are pulse switching signals. FIG. 7 is a diagram showing the relationship between the welding current waveform and arc voltage waveform when the base current is 20 A or more, and FIG. 8 is a diagram showing the relationship between the welding current waveform and the arc voltage waveform when the base current is 20 A or more. FIG. 9, a circuit diagram of the voltage control device, is a diagram showing the relationship between the pulse switching signal and the output of the second relay. DESCRIPTION OF SYMBOLS 1... Welding torch, 2... Base metal, 3... Arc voltage detection device, 4... Comparator, 5... Reference voltage generator, 6... Amplifier, 7... Capacitor, 8...
Drive circuit, 9...Motor, 11...Pulse switching signal synchronization delay circuit, 12...Relay, 13...First
Normally open contact, 14... Second normally open contact, 15... Reference voltage generator for pulse current, 16... Reference voltage generator for base current, 17... Third contact, 18... Fourth contact, 19 ... Welding current detection device, 21 ... Fifth contact, 22 ... Pulse switching signal synchronization delay circuit during pulse current, 23 ... Pulse switching signal synchronization delay circuit during base current, 24 ... Second relay.

Claims (1)

[Claims] 1. Arc voltage detection for detecting the arc voltage between a non-consumable electrode and a base metal in a TIG arc welding device that performs welding by periodically changing the welding current into a pulse current and a base current. a reference voltage generator that generates a reference voltage when the welding current is a pulse current; and a comparison between the arc voltage detected by the arc voltage detection device and the reference voltage generated from the reference voltage generator. A comparator that outputs the difference voltage between the two voltages, and a pulse switching signal for switching the welding current from the base current to the pulsed current, which starts output after a predetermined time and changes the welding current from the pulsed current to the base current. It has a pulse switching signal synchronous delay circuit that stops output when a pulse switching signal for switching is input, and a feedback circuit consisting of a series circuit of a first contact and a capacitor that are closed by the output of this pulse switching signal synchronous delay circuit. an amplifier that integrates and amplifies the differential voltage output from the comparator; and a drive circuit that is driven by receiving the output of the amplifier through a second contact that is closed by the output of the pulse switching signal synchronization delay circuit. An arc voltage control device comprising a motor that moves a welding torch that holds the non-consumable electrode up and down based on the output of the drive circuit. 2. In a TIG arc welding device that performs welding by periodically changing the welding current alternately between a pulse current and a base current, there is an arc voltage detection device that detects the arc voltage between the non-consumable electrode and the base metal, and a A pulse current reference voltage generator that generates a pulse current reference voltage when the welding current is a base current; a base current reference voltage generator that generates a base current reference voltage when the welding current is a base current; a third contact that closes in response to a pulse switching signal for switching the current from the base current to the pulsed current; a fourth contact that closes in response to the pulse switching signal for switching the welding current from the pulsed current to the base current;
A pulse current reference voltage output from the pulse current reference voltage generator and input through the third contact; or a base current output from the base current reference voltage generator and input through the fourth contact. a comparator that compares a reference voltage with the arc voltage detected by the arc voltage detection device and outputs a voltage difference between the two compared voltages; a welding current detection device that detects the welding current; and a welding current detection device that detects the welding current. A fifth contact that closes when the welding current detected by the device is larger than a predetermined current value, and outputs a predetermined time after a pulse switching signal for switching the welding current from the base current to the pulse current is input. A pulse switching signal synchronization delay circuit for switching the welding current from the pulsed current to the base current, which stops the output when the pulse switching signal for switching the welding current from the pulsed current to the base current is input. When a pulse switching signal for switching the welding current from the base current to the pulse current is inputted via the fifth contact, the output is started after a predetermined time after the pulse switching signal is inputted through the fifth contact. a base current pulse switching signal synchronization delay circuit that stops output, and a first contact and a capacitor that are closed by the output of the pulse current pulse switching signal synchronization delay circuit or the output of the base current pulse switching signal synchronization delay circuit. an amplifier that has a feedback circuit formed of a series circuit and integrates and amplifies the differential voltage output from the comparator; and an output of the pulse switching signal synchronization delay circuit during pulse current or an output of the pulse switching signal synchronization delay circuit during base current. an arc comprising: a drive circuit driven by inputting the output of the amplifier through a second contact closed by the arc; and a motor that moves a welding torch holding the non-consumable electrode up and down based on the output of the drive circuit. Voltage control device.