JP2587390Y2 - AC / DC TIG 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 an AC / DC TIG arc welding machine with improved arc starting.

[0002]

2. Description of the Related Art Conventionally, in a TIG arc welding machine,
Using a tungsten electrode made of a high melting point material, a welding machine is supplied with a DC or AC welding output feedback-controlled to a constant current from the welding machine to the welding load of the electrode and the base material, and the base material is melted and welded.

[0003] When the tungsten electrode is brought into contact with the base material at the time of arc start and is started with a large capacity, the tungsten electrode melts into the base material and causes poor welding. If the starting current at the time of arc start is small, the electrode is not heated, so that no arc is generated between the tungsten electrode and the base material, and arc start failure occurs. Therefore, at the time of arc start, a gap is provided between the electrode and the base material, and an arc is generated by applying a high frequency (2 to 3 MHz) and a high voltage (2000 to 3000 V) to the gap. It has shifted to constant current welding.

When a TIG arc welding machine is used for direct current arc welding, if a thin plate is arc-started with a large current, the base material will suffer from burn welding, so the current level at the time of arc start is reduced. However, when the current level is low, arc start failure occurs. Therefore, the thorium tungsten electrode or the yttrium tungsten electrode in which thorium or yttrium is mixed in the electrode is used to increase the emission of thermionic electrons from the electrode.

However, when the electrode is used for AC arc welding using a thorium tungsten electrode or a yttrium tungsten electrode, the electrode is heated by thermoelectrons while the base material is at a positive potential and the base material is at a reverse polarity of a negative potential. Thorium and yttrium may be dissolved out of the base material, and the base material may be considered as dark spot welding failure. For this reason, when using an arc welding machine for an AC arc welding machine, a 100% tungsten electrode is usually used.

[Problems to be solved by the invention]

[0006] When AC welding and DC welding are successively used using a TIG arc welding machine, a 100% tungsten electrode is used as an electrode. However, a 100% tungsten electrode tends to cause arc start failure as described above.

[0007] This invention provides an AC / DC TI that can reliably start an arc in both AC welding and DC welding.
It is an object to provide a G arc welding machine.

[0008]

In order to achieve the above object, in the case of the AC / DC TIG welding machine of the present invention, a DC power supply is input, switching elements are switched, and DC or AC is output to output, and AC welding is performed. Or an AC / DC TIG arc welding machine used in DC welding,
A DC start current setting device for setting a DC start current, an AC start current setting device for setting an AC start current during the AC welding, a setting signal for the DC start current setting device, and a setting signal for the AC start current setting device A start current setting switch for switching between the first and the second, a timer for setting a time for outputting the start current, and a DC start current of a positive polarity or a reverse polarity during the DC welding by turning on and off the switching element. It is constituted by a low-frequency drive device which outputs continuously and outputs a drive signal for outputting a DC start current having a reverse polarity during AC welding and outputting an AC start current which continues after a predetermined time.

[0009]

The AC / DC TIG of the present invention constructed as described above.
In the case of an arc welding machine, at the time of direct current welding, the switching element is driven for a predetermined time and the switching element is driven to output a direct current to start the arc. The arc is started by setting the continuous alternating current to drive the switching element.

[0010]

Embodiment (1 embodiment) An embodiment will be described with reference to FIGS. In FIG. 1, reference numerals 1a and 1b denote power input terminals of a welding machine, 2 denotes an input rectifier having a bridge configuration of diodes 3, 4, 5, and 6, 7 denotes a smoothing capacitor, and 8 denotes two IGBTs, transistors, and MOSFETs. A high-frequency inverter having a half-bridge configuration including switching elements 9 and 10 and capacitors 11 and 12;
Under the control of 3, the DC output of the capacitor 7 is converted into a high-frequency AC having a predetermined frequency of 1 kHz or more.

Reference numeral 14 denotes a transformer for converting a high-frequency AC of the high-frequency inverter 8 into a voltage required for welding, and 15 denotes a transformer 1
4, 16, 17 and 1 for rectifying the secondary output of
An output rectifier having a bridge configuration of 8, 19, a smoothing reactor 20, an IGBT, a transistor, a MOSFE
Four switching elements 22, 23, 24, 25 such as T
Is a low-frequency generator having a full-bridge inverter configuration, and converts the DC output of the reactor 20 into a low-frequency welding output of about 100 Hz and outputs it in a steady state under PWM control of the low-frequency driving device 26.

Reference numeral 27 denotes a welding load, and the low frequency generator 2
Tungsten electrode 2 connected to one pair of output terminals
8. The base material 29 is formed.

Reference numeral 30 denotes a current detector provided between the output terminal and the base material 29. 31 is a DC start current setting device that outputs a start current setting signal for DC welding,
Reference numeral 32 denotes an AC start current setting device that outputs a start current setting signal for AC welding, which is set higher than the output signal of the DC start current setting device. 33 is a stationary current setter that outputs a stationary current setting signal, 34 is setters 31 and 32
, A start-time setting switch for switching the output time of the start current, 36, a start-time switch for switching the start time according to the welding mode, and 37, an OR circuit for setting signal selection. OR gates 38 and 39 whose anodes are connected to the setting device 34 and the setting device 33.

The diodes 40 and 41 have diodes 38 and 39 at one end.
The opening / closing section is provided by a relay contact or an electronic switch connected to the cathode of the battery. 4
2 is an output current setting signal of the OR circuit 34 and the current detector 30
An error amplifier that calculates an error with the current detection signal of
The output signal is supplied to the high-frequency driving device 13 as a constant current feedback control signal. The OR circuit 37 and the opening / closing units 40 and 41 form a setting signal output switching unit.

Reference numerals 45 to 47 denote start command signal terminals in output form. The electrodes have a negative potential and a positive potential, respectively, in DC arc welding.
When the base material has the opposite polarity of the negative potential, a start command for AC arc welding is issued.

Next, the operation will be described. The AC power of the power input terminals 1a and 1b is rectified and smoothed by the input rectifier 2 and the capacitor 7 and converted into DC. The DC is supplied to the high frequency inverter 8, and the driving control of the switching elements 9 and 10 by the high frequency driving device 13 is performed. Is converted to a high-frequency alternating current.

Further, the high-frequency AC is supplied to an output rectifier 15 via a transformer 14, and the rectifier 15 and the reactor 20 are rectified and smoothed to convert the high-frequency AC again to DC to form a DC power supply. The direct current is supplied to the low-frequency generator 21 as a power source, and the low-frequency driver 21 controls the driving of the switching elements 22 to 25 so that the low-frequency generator 21 is in a DC or AC output state at the start of the arc and after the arc is generated. Move to

Further, the output of the low frequency generator 21 is supplied to the welding load 27, and the current flowing through the welding load 27 is detected by the current detector 30 based on this supply. Then, the current detection signal of the current detector 30 and the output current setting signal of the OR circuit 37 are supplied to the error amplifier 42, and the output signal of the amplifier 42 causes the high frequency driving device 13 to output the output of the high frequency inverter 8 to the output current setting signal. Based on the constant current feedback control.

Next, the operation at the time of arc start will be described. Now, when performing DC arc welding, the setting switch 3
4. The start current switch 36 selects DC side DC.
When a signal for commanding a positive polarity by DC arc welding is input to the start command signal terminal 45, a drive signal is input to the switching elements 24 and 23 of the low frequency generator 21 by the low frequency driver 26 and turned on. When a high-frequency high voltage is applied between the electrode 28 and the base material 29 by a high-frequency generator (not shown), the switching element 24, the current detector 30, the base material 2
9, a current flows through the tungsten electrode 28 and the switching element 23. On the other hand, the timer 35 counts the time according to the activation signal. This current is detected by the current detector 30,
This detection signal and the output current setting signal of the DC start current setting unit 31 are supplied to the error amplifier 42,
2, the high-frequency driving device 13 controls the high-frequency inverter 8 and outputs a starting current I1 as shown in FIG. 2, which is fed back to a constant current based on the setting signal of the DC start current setting device 31, and An arc is generated in the material 29.

When the timer 35 times out after the time T1, the opening / closing section 40 is opened and the opening / closing section 41 is short-circuited. The output current setting signal of the steady current setting unit 33 is supplied to the error amplifier 42, and the setting signal with the detection signal is amplified to become a steady-state constant current I2 based on the setting signal as shown in FIG.

However, when the arc is not generated between the electrode 28 and the base material 29 during the above-described DC arc welding and an arc start failure occurs, a signal for instructing the reverse polarity to the start command signal terminal 46 is inputted. I do. A drive signal is input to the switching elements 22 and 25 of the low-frequency generator 21 via a low-frequency drive signal 26 in response to a command signal, and is turned on. When a high frequency high voltage is applied between the electrode 28 and the base material 29 from a high frequency generator (not shown), the switching element 22 and the electrode 2
8, base material 29, current detector 30, switching element 25
A current having the opposite polarity as shown in FIG. Then, the constant current I1 based on the setting signal of the DC start current setting unit 31 flows to the welding load 27 until the timer 35 times out, and the tungsten electrode 28 is heated by the thermoelectrons to generate an arc.

When the timer 35 times out, the opening / closing section 40 is opened and the opening / closing section 41 is short-circuited. The output current setting signal of the steady-state current setting unit 33 is supplied to the error amplifier 42, an error from the detection signal is amplified, and a steady-state constant current based on the setting signal is output. However, the low-frequency driving device 26 receives the time-up signal from the timer 35, turns off the driving signal to the switching elements 22 and 25 of the low-frequency generating device 21, outputs the driving signal to the switching elements 24 and 23, and performs switching. The elements 24 and 23 are turned on.
As a result, a positive current I2 flows as shown in FIG. 3 in which a positive potential is applied to the base material 29 and a negative potential is applied to the tungsten electrode 28.

When performing AC arc welding, the setting device 34,
The start current switch 36 selects AC on the AC side. When a signal for instructing AC arc welding is input to the start command signal terminal 47, a drive signal is input to the switching elements 22 and 25 of the low frequency generator 21 by the low frequency driver 26 to turn it on. At this time, when a high frequency voltage is applied between the electrode 28 and the base material 29 by a high frequency generator (not shown), the switching element 22, the tungsten electrode 28, and the base material 2
9, currents of opposite polarities flow through the current detector 30 and the switching element 25 as shown in FIG. This current is detected by the current detector 30, and the detection signal is supplied to the error amplifier 42 with the output current setting signal of the AC start current setting device 32, and the high frequency driving device 13
Controls the high-frequency inverter 8 and outputs a starting current I3 as shown in FIG. 4 which is fed back to a constant current based on the setting signal of the AC start current setting unit 31, and an arc is generated in the electrode 28 and the base material 29. And tungsten electrode 2
8 is heated by thermionic electrons.

Further, when the timer 35 further times out after T2 time to avoid arc start failure, a time-up signal is inputted to the low frequency driving device 26,
The switching elements 22 and 25 are driven by the low frequency driving device 26.
Is turned off, a drive signal is input to the switching elements 24 and 23 to turn them on, and then the switching elements 22 and 25 and the switching elements 24 and 23 are turned on and off alternately.
An alternating current is applied to the welding load 27 as shown in FIG.

When the timer 35 further times out after the time T3, the opening / closing section 40 is opened and the opening / closing section 41 is short-circuited. The output setting signal of the steady current setting unit 33 is supplied to the error amplifier 42, and the error from the detection signal is amplified. As shown in FIG.
Is output.

(Other Embodiments) In the above embodiment, the low-frequency generator 21 is implemented using a bridge inverter, but can be applied to a low-frequency generator 61 using a switching circuit as shown in FIG. . That is, in FIG. 5, the same reference numerals as those in FIG. 1 indicate the same or those having the same functions, and the points different from FIG. 1 are the following points (A) to (D).

(A) A transformer 54 having a secondary winding intermediate tap is provided in place of the transformer 14 shown in FIG. 1. The primary winding of this transformer is connected to a high frequency inverter, and the secondary winding tap is provided. Connected to the electrode 28. (A) Instead of the output rectifier 15 of FIG.
To 59, an output rectifier 55 having a two-phase half-wave rectification circuit configuration is provided, and a pair of AC terminals of the rectifier 55 is connected to both ends of a secondary winding.

(C) In place of the smoothing reactor 20 of FIG. 1, smoothing reactors 60a and 60b having one end connected to the positive and negative output terminals of the output rectifier 55 are provided. (D) A low-frequency generator 61 having two semiconductor switching elements 62 and 63 is provided in place of the low-frequency generator 21 having the bridge configuration in FIG. 1, and the collector and emitter of the switching element 62 are connected to the other end of the smoothing reactor 60a. , The emitter and collector of the switching element 63 are connected to the other end of the smoothing reactor 60b and the base material 29 via the current detector 30, and the bases of the switching elements 62 and 63 are connected. Is connected to the output of the low frequency driving device 26.

Then, similarly to the output of the secondary winding of the transformer 14 shown in FIG. 1, the high-frequency AC is subjected to two-phase half-wave rectification by the output rectifier 55 and is smoothed by the smoothing reactors 60a and 60b to form a DC power supply. . Furthermore, the low frequency driving device 26
When the switching element 62 is turned on, a DC current having a positive polarity flows to the welding load 27. When the switching element 63 is turned on, a DC current of the opposite polarity is applied to the welding load 27.
Flows to Further, by alternately turning on and off the switching elements 62 and 63, an alternating current flows through the welding load 27.

The operation of the AC / DC TIG arc welding machine shown in FIG. 5 at the time of arc start may be operated in the same manner as the arc welding machine shown in FIG.

In the above two embodiments, the transformers 14, 5
Although the AC input power supply (low-frequency AC power supply) is converted to high-frequency AC by a half-bridge inverter in order to reduce the size of 4, the AC input power may be converted to AC by a full-bridge inverter. Further, the high-frequency AC is rectified and smoothed and used as the DC power supply used for the input of the low-frequency generators 21 and 61. You may. In this case, in order to perform the constant current feedback control, the output of the error amplifier 42 may be used as the input signal of the low frequency driving device 21 or 61. The configuration of each unit is not limited to the embodiment.

[0032]

[Effects of the Invention] Since the present invention is configured as described above, the DC set for a predetermined time during DC welding is output and the arc is started. It is set by an alternating current that is set and continues after a predetermined time, and the arc starts.
% Tungsten electrode can be reliably performed.

[Brief description of the drawings]

FIG. 1 is a connection diagram of an embodiment of an AC / DC TIG arc welding machine of the present invention.

FIG. 2 is a timing chart for explaining the operation of FIG. 1 when the arc start of DC welding is operated with a positive polarity.

FIG. 3 is a timing chart for explaining the operation of FIG. 1 when the arc start of DC welding is operated with a reverse polarity.

FIG. 4 is a view when an arc start of AC flow welding is started.
4 is a timing chart for explaining the operation of the first embodiment.

FIG. 5 is a connection diagram of another embodiment of the AC / DC TIG arc welding machine of the present invention.

[Explanation of symbols]

 2 Input Rectifier 4 High Frequency Inverter 13 High Frequency Drive 14,54 Transformer 15,55 Output Rectifier 21,61 Low Frequency Generator 26 Low Frequency Drive 27 Welding Load 28 Tungsten Electrode 29 Base Material 30 Current Detector 31 DC Start Current Setting Device 32 AC start current setting device 33 steady current setting device 34 setting switching device 35 timer 36 start current switching device 37 OR circuit 38,39 diode 40,41 opening / closing section 42 error amplifier 45-47 start command signal terminal

────────────────────────────────────────────────── ─── Continued on front page Examiner Michitaka Ohata (58) Field surveyed (Int.Cl. ⁶ , DB name) B23K 9/073 B23K 9/067

Claims (1)

(57) [Scope of request for utility model registration] 1. An AC / DC TIG arc welding machine used in AC welding or DC welding by inputting a DC power supply, switching a switching element, and outputting DC or AC as an output. A DC start current setting device to be set, an AC start current setting device to set an AC start current at the time of the AC welding, and a start to switch between a setting signal of the DC start current setting device and a setting signal of the AC start current setting device. A current setting switch,
A timer for setting the output time of the start current, and on / off of the switching element, output a DC start current of positive polarity or reverse polarity at the time of DC welding, continue the DC output after a predetermined time, and at the time of AC welding, An AC / DC TIG arc welding machine comprising a low-frequency driving device that outputs a drive signal that outputs a DC start current of a polarity and outputs an AC start current that continues after a predetermined time.