JPH079136A - Direct current tig welding machine - Google Patents

Abstract

PURPOSE:To easily detect the generation of arc of both positive and reverse polarities from small current range up to large current range with a simple configuration in a direct current TIG welding device with changable output polarity. CONSTITUTION:Between output terminals of a main circuit 1, a 1st Zener diode in which the output voltage is made conductive in no-load voltage V1 in the outputting time of positive polarity and made nonconductive in the arc voltage V2 by joining cathode to the terminal of a base material 4 side, a 2nd Zener diode in which the outputting voltage is made conductive in non-load voltage V3 and nonconducctive in the arc voltage V4 in the reverse polarity outputting time by joining cathode to the terminal of an electrode 3 side are joined, and a photocoupler 7 for alternative current signals is joined between the 1st and 2nd Zener diodes. In such a way, even if the output polarity is any positive or reverse side, the generation of arc can be detected with the outputting voltage value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC TIG welding apparatus having an output polarity switching circuit.

[0002]

2. Description of the Related Art A DC TIG welding apparatus of this type uses a non-consumable electrode (hereinafter referred to as an electrode) as a minus during welding.
Welding output is the positive output that makes the work piece (hereinafter referred to as the base metal) positive, but in order to improve arc start performance, the electrode is positive only at the start of welding and the base metal is negative. The reverse polarity arc start method by the reverse polarity output is generally used.

The DC TIG welding apparatus adopting the reverse polarity arc start method has a structure as shown in FIG.

In the figure, reference numeral 1 designates an alternating current as an input, and an electrode 3
A main circuit section capable of switching the polarity of the output supplied between the base material and the base material 4, 2 is a control section for controlling the main circuit section, 3 is an electrode, 4 is a base material, and 9 is an insulated current detector. In such a DC TIG welding device capable of switching the output polarity, a reverse polarity arc start method in which the output polarity is reversed only at the start of welding, and a positive arc start method in which the output polarity is positive even at the start of welding You can choose and.

In the above structure, the generation of an arc between the electrode 3 and the base material 4 is detected by the insulation type current detector 9. When an arc is generated between the electrode 3 and the base material 4 and an output current flows, the insulation type current detector 9 sends a detection signal proportional to the output current to the control unit 2. The detection signal is subjected to full-wave rectification in the control unit 2, and regardless of whether the output current has a positive polarity or a reverse polarity, when the detection signal subjected to the full-wave rectification exceeds a preset threshold value, arc occurrence detection is performed. A signal is sent to the control unit 2 and used for various controls. This arc generation detection method is used in conventional DC TIG welding equipment and AC TIG
It is widely used in welding equipment.

[0006]

In the DC TIG welding apparatus having such a conventional structure as described above, it is possible to detect the generation of arcs of forward and reverse polarities while insulating the secondary side output of the welding apparatus and the control unit 2. Yes, but if the output current is small,
Since the detection signal sent from the insulation type current detector 9 to the control unit 2 is a minute signal, it may be difficult to distinguish the detection signal from the threshold value for detecting the arc occurrence. Therefore,
Increase the minimum output current value of the welding device to make it easier to distinguish the detection signal from the threshold value, or
It was necessary to separately load a current detector for small current detection.

The present invention solves the above problems and is a direct current TI capable of detecting arc generation of forward and reverse polarities with a simple structure.
It is intended to provide a G welding device.

[0008]

In order to achieve the above-mentioned object, the present invention is connected between terminals of a main circuit portion, and a cathode is connected to a terminal on the side of an object to be welded so that conduction is carried out at no-load voltage during positive output. Then, the first Zener diode which becomes non-conducting at the arc voltage and the second Zener which becomes non-conducting at the arc voltage by connecting the cathode to the non-consumable electrode side output terminal and conducting at no load voltage at the time of reverse polarity output The diode is connected to the anodes of the first Zener diode and the second Zener diode, and the polarity is reversed according to the voltage value between the output terminals when the first Zener diode or the second Zener diode is conductive. And an arc generation detector for detecting the occurrence of the arc.

[0009]

In the above structure, when the output polarity is positive and the output voltage is equal to or higher than the Zener voltage of the first Zener diode, the arc generation detector conducts and sends an arc non-occurrence signal to the control circuit. If the voltage is less than the voltage, the arc generation detection signal is sent to the control circuit without conducting. Also,
When the output polarity is the opposite polarity and the output voltage is equal to or higher than the Zener voltage of the second Zener diode, the arc generation detector conducts and sends the arc generation signal to the control circuit. Then, the arc generation detection signal is sent to the control circuit.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

In the figure, reference numeral 1 is a main circuit portion capable of switching the polarity of an output supplied between an electrode and a base material by inputting an alternating current, 2 is a control portion for controlling the main circuit portion, 3 is an electrode, and 4 is a mother material. It is a material.

Reference numeral 5 is a first Zener diode for discriminating the output voltage value at the time of positive output, and the cathode is connected to the welded object side terminal of the main circuit portion 1. Reference numeral 6 is a second Zener diode for discriminating the output voltage value at the time of reverse polarity output, and the cathode is connected to the non-consumable electrode side terminal of the main circuit unit 1. Reference numeral 7 denotes an arc generation detector that operates when the first Zener diode 5 or the second Zener diode 6 is conductive and outputs the signal to the control unit 2, and is formed of an AC signal photocoupler. Then, the first Zener diode 5 is provided at one pole and the second Zener diode 6 is provided.
Is connected to the other pole. Reference numeral 8 is a limiting resistor for suppressing current.

In the above structure, when welding is performed, the output voltage of the preselected polarity is supplied between the output terminals of the main circuit unit 1 together with the welding start command.

When the output polarity at the start of welding is positive, a positive output voltage is output between the base material 4 and the electrode 3 with the base material 4 side being positive and the electrode 3 side being negative. When the voltage at the time of positive polarity output is a positive potential, the positive polarity output voltage is the no-load voltage V until an arc is generated between the base material 4 and the electrode 3.
₁ , and the positive output voltage becomes the arc voltage V ₂ after the arc is generated. The relationship of V ₁ > V ₂ is established between the no-load voltage V ₁ and the arc voltage V ₂ .

If the value of the zener voltage V _Z1 of the first zener diode 5 is set so that V ₁ > V _Z1 > V ₂ , the first zener diode V ₁ is output when the output voltage is the no-load voltage V _1. 5 conducts, the Zener current flows from the first Zener diode 5 through the limiting resistor 8 to the AC signal photocoupler 7, the secondary side transistor of the AC signal photocoupler 7 conducts, and an arc non-generated signal is generated. It is sent to the control unit 2. Then, when an arc is generated and the output voltage becomes the arc voltage V ₂ , the first Zener diode 5 becomes non-conductive and the Zener current stops flowing. As a result, the secondary side transistor of the AC signal photocoupler 7 becomes non-conductive, and is recognized by the control unit 2 as an arc generation signal.

When the output polarity at the start of welding is reverse polarity, a reverse polarity output voltage is output between the base material 4 and the electrode 3 with the base material 4 side being negative and the electrode 3 side being positive. When the voltage at the time of reverse polarity output is a positive potential, the reverse polarity output voltage is the no-load voltage V ₃ until the arc is generated between the base material 4 and the electrode 3, and after the arc is generated, the reverse polarity output voltage is the arc. The voltage becomes V ₄ . The relationship of V ₃ > V ₄ is established between the no-load voltage V ₃ and the arc voltage V ₄ .

If the zener voltage order V _Z2 of the second zener diode 6 is set so that V ₃ > V _Z2 > V ₄ , the second zener voltage V ₃ becomes the second Zener voltage when the output voltage is the no-load voltage V _3. Since the diode 6 becomes conductive, and the Zener current flows from the second Zener diode 6 through the AC signal photocoupler 7 and the limiting resistor 8, the secondary side transistor of the AC signal photocoupler 7 becomes conductive and no arc occurs. The signal is sent to the control unit 2. When an arc occurs and the output voltage becomes the arc voltage V ₄ , the second Zener diode 6
Becomes non-conductive, and the Zener current stops flowing. As a result, the secondary side transistor of the AC signal photocoupler 7 becomes non-conductive, and is recognized by the control unit 2 as an arc generation signal.

As described above, according to the DC TIG welding apparatus of the embodiment of the present invention, the no-load voltages V ₁ and V ₃ and the arc voltages V ₂ and V ₄ are obtained at both the small output current and the large output current.
Therefore, it is possible to detect the occurrence of arc in a wide range from a small current to a large current by the Zener voltages V _Z1 and V _Z2 .

[0019]

As is apparent from the above description, according to the present invention, the first Zener diode for determining the positive output voltage value and the reverse polarity output voltage value for determining the positive output voltage value are provided between the output terminals of the main circuit section. By connecting the second Zener diode and the AC signal photocoupler, which is an arc generation detector, to detect the arc generation, a small output can be obtained regardless of whether the output polarity is positive or reverse. It is possible to provide a DC TIG welding apparatus capable of detecting arc generation from an electric current to a large output current depending on an output voltage value and capable of detecting arc generation of both forward and reverse polarities with a simple configuration.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of a DC TIG welding apparatus according to an embodiment of the present invention.

FIG. 2 is a block circuit diagram of a conventional DC TIG welding device.

[Explanation of symbols]

 1 Main Circuit Section 2 Control Section 3 Non-consumable Electrode (Electrode) 4 Workpiece (Base Material) 5 First Zener Diode 6 Second Zener Diode 7 Arc Generation Detector (Photocoupler for AC Signal)

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] February 17, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

In the above structure, the generation of an arc between the electrode 3 and the base material 4 is detected by the insulation type current detector 9. When an arc is generated between the electrode 3 and the base material 4 and an output current flows, the insulation type current detector 9 sends a detection signal proportional to the output current to the control unit 2. The detection signal is subjected to full-wave rectification in the control unit 2, and regardless of whether the output current has a positive polarity or a reverse polarity, when the full-wave rectified detection signal exceeds a preset threshold value, an arc generation signal is generated. Recognized as
It is recognized and used for various controls. This arc generation detection method is widely adopted in the conventional DC TIG welding apparatus and AC TIG welding apparatus.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

[0006]

In the DC TIG welding apparatus having such a conventional structure as described above, it is possible to detect the generation of arcs of forward and reverse polarities while insulating the secondary side output of the welding apparatus and the control unit 2. Yes, but if the output current is small,
Since the detection signal sent from the insulation type current detector 9 to the control unit 2 is a minute signal, it may be difficult to distinguish the detection signal from the threshold value for detecting the arc occurrence. Therefore,
Increase the minimum output current value of the welding device to make it easier to distinguish the detection signal from the threshold value, or
It was necessary to add a current detector for small current detection separately.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

The Zener voltage of the second Zener diode 6
By setting the value of the voltage V _{Z2 so} that V ₃ > V _Z2 > V ₄ , the second Zener diode 6 becomes conductive when the output voltage is the no-load voltage V ₃ , and the Zener current becomes the second voltage. Since it flows from the Zener diode 6 through the AC signal photocoupler 7 and the limiting resistor 8, the secondary side transistor of the AC signal photocoupler 7 becomes conductive and sends an arc non-occurrence signal to the control unit 2. Then, when an arc is generated and the output voltage becomes the arc voltage V ₄ , the second Zener diode 6 becomes non-conductive and the Zener current stops flowing. As a result, the secondary side transistor of the AC signal photocoupler 7 becomes non-conductive, and is recognized by the control unit 2 as an arc generation signal.

Claims (1)

[Claims] 1. A main circuit section capable of switching the polarity of an output supplied between a non-consumable electrode and an object to be welded by inputting an alternating current, a control section for controlling the main circuit section, and an output of the main circuit section. The first Zener diode is connected between the terminals, the cathode is connected to the work piece side output terminal, and it conducts at no-load voltage at positive output and becomes non-conducting at arc voltage, and the cathode at the non-consumable electrode side output terminal. Is connected to the second Zener diode which becomes conductive at no load voltage and becomes non-conductive at arc voltage at the time of reverse polarity output and the anodes of the first Zener diode and the second Zener diode. An arc generation detector for detecting arc generation of both positive and reverse polarities according to the voltage value between the output terminals when the Zener diode or the second Zener diode is turned on. TIG welding equipment.