JP2006055886A - Tig welding machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect the short-circuit between an electrode and a base metal in a non-welding state by a means which is not checked by high pressure high frequency voltage generated at the time of starting an arc in TIG (Tungsten Inert Gas) welding. <P>SOLUTION: An automatic TIG welding system is inexpensively provided. The system is provided with a two mode starting means, in the starting of a welding machine, of the starting accompanied by high frequency and the starting not accompanied by high frequency which starts without being accompanied by high frequency at the time of performing the detection of the short-circuit of the electrode, and is additionally provided with a short-circuit detection function where, at this time, whether short-circuit is present or not is discriminated by the fact that electric current is detected or not, thus the discrimination of the short-circuit between the electrode and a base metal can be performed without providing a short-circuit detection circuit to be coupled/separated with a relay, contacts or the like. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technique for detecting a short circuit state between an electrode and a base material in an automatic welding apparatus using a TIG welder.

  In recent years, with the spread of robots, not only MAG welding but also TIG welding has been automated. Regardless of the welding method, one of the problems in automating welding is the problem of detection of fusion between an electrode and a base material.

  In other words, the welding torch is fixed to a moving device such as a robot, and the base material is fixed to a jig. Therefore, after welding is completed, the electrode fixed to the tip of the welding torch and the base material are fused together. If the operation is continued, the welding torch holding the electrode may be damaged. In order to avoid this phenomenon, it is necessary to detect the fusion between the electrode and the base material after the end of welding, and to stop a moving device such as a robot when the fusion is detected.

  As a method for detecting whether or not such an electrode and a base material are actually fused, the fusion is usually detected by detecting an electrical short circuit between the electrode and the base material.

  For example, a method of detecting a short circuit between an electrode and a base material, which is generally performed in MAG welding, is a method of applying a detection voltage between the electrode and the base material via a voltage dividing resistor. This utilizes the fact that the voltage between the base materials is different between when the electrode and the base material are short-circuited and when they are opened.

  This short-circuit detection circuit must be separated by a relay contact other than during short-circuit detection operation in order to prevent the short-circuit phenomenon between the electrode and the base metal that occurs during welding and the malfunction of the short-circuit detection circuit due to arc voltage, etc. (For example, refer to Patent Document 1).

  FIG. 3 is a circuit diagram around the welding torch including the conventional electrode short-circuit detection circuit, and the one indicated by the one-dot chain line in the drawing is an electrode short-circuit detection circuit.

  In FIG. 3, 7 is a welding torch, 8 is an electrode, 9 is a base material, 101 is a welding machine positive electrode output terminal connected to the electrode 8 via the welding torch 7, and 102 is a welding machine connected to the base material 9. Negative output terminal, 103 is a voltage applying means for detecting a short circuit, 104 is a resistor, 105 is a magnet switch, 106 and 107 are contacts of the magnet switch 105, 108 is a contact for driving the magnet switch 105, 109 is a short circuit detection A commanding contact 110 is a comparator for comparing the welding machine output terminal voltage with a reference voltage.

  Reference numeral 111 denotes a comparison voltage input terminal of the comparator 110, and a voltage between the welding machine output terminals 101-102 is applied during a short-circuit detection operation. Further, 112 is a reference voltage input terminal of the comparator 110, and is set so that a voltage lower than the voltage applied to the comparison voltage input terminal 111 is applied in a state where the welding machine output terminals 101 and 102 are not short-circuited. . Reference numeral 113 denotes a short-circuit detection relay that operates when the output of the comparator 110 becomes positive.

  The operation in such a conventional electrode short circuit detection circuit will be described. When short circuit detection is not performed in FIG. 3, the short circuit detection circuit is disconnected from the welding machine output terminal by the contacts 106 and 107. Next, when short-circuit detection is performed, the short-circuit detection circuit disconnected by closing the contacts 108 and 109 is connected to the welding machine output terminals 101 and 102, and the short-circuit detection voltage is output to the welding machine via the resistor 104. Applied between terminals 101-102.

And when the welding machine output terminals 101 and 102 are not short-circuited, the voltage of the comparison voltage input terminal 111 is higher than the voltage of the reference voltage input terminal 112, so the output of the comparator 110 becomes a negative voltage, but the short-circuit detection relay 113 does not operate. When the detection circuit is connected in a state where the contact machine output terminals 101 and 102 are short-circuited, the short-circuit detection voltage is almost applied to the resistor 104 and almost no voltage is applied to the comparison voltage input terminal 111. That is, since the voltage at the reference voltage input terminal 112 is higher than the voltage at the comparison voltage input terminal 111, the output of the comparator is positive and the short circuit detection relay 113 is operated.
Japanese Patent Laid-Open No. 08-1118018 (6th page, FIG. 4)

  However, in TIG welding, a high-frequency high-frequency voltage of several thousand volts is applied between an electrode and a base material that are positioned at a very short distance to generate a high-frequency discharge of a very small current between the electrode and the base material. An arc start method that induces main arc discharge for welding is used. Therefore, when the short-circuit detection means of the prior art is applied to TIG welding, even if the short-circuit detection circuit is disconnected from the welding machine output terminal at the time of arc start, the contact where the high-frequency voltage applied to the electrode and the base material is disconnected If the insulation is broken and leaked to the short-circuit detection circuit side, the short-circuit detection circuit malfunctions or is extreme, and the short-circuit detection circuit is destroyed. For these reasons, the short-circuit detection means of the prior art has a problem that it cannot be easily applied to a TIG welder.

  An object of this invention is to provide the electrode short circuit detection means which is not influenced by the high voltage | pressure high frequency at the time of the arc start peculiar to TIG welding.

  In order to solve the above problems, a TIG welding machine of the present invention generates a welding output portion that generates a welding output voltage for performing welding, and a high-frequency high-frequency voltage that superimposes the welding output voltage and starts an arc. A high-frequency output unit, and a start-up method selection means having at least two start-up methods of a start-up method for simultaneously generating the welding output voltage and the high-frequency voltage and a start-up method for generating only the welding output voltage alone. . The TIG welder of the present invention further includes short-circuit detecting means for detecting the presence / absence of a short circuit between the electrode and the base material based on the presence / absence of a welding current when a starting method for generating only the welding output voltage is selected. Moreover, the TIG welding machine of the present invention further includes an external output unit that outputs to the outside that the electrode is in a short-circuited state when the short-circuit detecting unit detects a short circuit between the electrode and the base material.

  Furthermore, in the TIG welding machine of the present invention, the starting method selection means has at least two starting methods: a starting method for simultaneously generating a welding output voltage and a high frequency voltage, and a starting method for generating only a welding output voltage independently. The two activation methods can be arbitrarily selected by an external signal.

  As described above, according to the present invention, in the TIG welding machine, by using the output voltage generation function and the current detection function, it is possible to perform a short circuit determination between the electrode and the base material without providing a short circuit detection circuit that performs coupling and disconnection at a relay contact or the like. It can be carried out.

  The best mode for carrying out the present invention will be described below with reference to FIG.

(Embodiment 1)
FIG. 1 is a configuration diagram of a TIG welding system showing an embodiment of the present invention, in which 1 is a TIG welding machine, and 2 is a welding machine control unit that receives and outputs signals from the TIG welding machine 1 and external devices. . The welding machine control unit 2 includes a starting method selection means 2a that selects and determines one of a plurality of starting methods at the time of welding output, and current detection information detected by the current detection unit 6 is externally transmitted from an external device or the like. And an external output means 2b for outputting to the output.

  Also, 3 is a welding output section that generates an output for welding, 4 is a high-frequency output section that generates a high-frequency high-frequency for arc start, and 5 is a cup that transmits high-frequency forces generated by the high-frequency output section 4 to the welding circuit. A ring transformer unit, 6 is a current detection unit for detecting a welding current, and 7 is a TIG welding torch, which is attached to a moving means (not shown) such as a tip of a robot arm. Reference numeral 8 denotes a TIG welding electrode, 9 denotes a base material, 10 denotes a torch moving means such as a robot, and a system control unit for controlling the TIG welding machine 1, and 10a denotes an electrode short-circuit determining means. The external device is not particularly limited, and may be the system control unit 10 or another operation / display unit.

  The operation | movement is demonstrated about the TIG welding system comprised as mentioned above. In the present embodiment, the system control unit 10 can arbitrarily command the welding machine control unit 2 to start with high frequency generation and to start welding output alone without high frequency generation. In the activation method selection means 2a provided in the above, the activation method instructed by the system control unit 10 can be selected and executed. When the current is detected by the current detection unit 6, the system control unit 10 can be immediately notified by the external output means 2b provided in the welding machine control unit 2. The short circuit determination means 10a in the system control unit 10 determines the presence or absence of a short circuit between the electrode and the base material from the type of activation by the system control unit 10 and the presence or absence of a current detection signal.

  Further detailed description will be given. First, in normal welding, the system control unit 10 instructs the welding machine control unit 2 to start welding in a state where the TIG welding electrode 8 is positioned with an appropriate gap between the TIG welding electrode 8 and the base material 9. In that case, start-up with high frequency is commanded. That is, at this time, the welding machine control unit 2 activates the welding output unit 3 and the high frequency output unit 4 at the same time, and a welding voltage in which a high frequency voltage is superimposed is applied between the TIG welding electrode 8 and the base material 9 to generate an arc. Is done. At this time, the short-circuit determining means 10a receives the current detection signal from the welding machine 1 but recognizes that the activation with high frequency is being executed, so that it is normal to receive the current detection, and the electrode short-circuit determination is performed. Absent.

  Next, when the system control unit 10 wants to know whether or not the TIG welding electrode 8 and the base material 9 are short-circuited, the system control unit 10 is accompanied by generation of high frequency in the starting method selection means 2a provided in the welding machine control unit 2. Command no start of welding voltage alone. In this case, the output of the welding voltage alone without the generation of high frequency is applied between the TIG welding electrode 8 and the base material 9. At this time, since the voltage applied between the TIG welding electrode 8 and the base material 9 is about several tens of volts, no current flows if there is even a slight gap. Further, if the TIG welding electrode 8 and the base material 9 are short-circuited, a current flows due to the applied welding voltage, and this current is detected by the current detection unit 6 and transmitted to the system control unit 10 from the external output means 2b. Then, the short-circuit determining means 10a determines that the TIG welding electrode 8 and the base material 9 are short-circuited when a current flows when starting without high frequency is performed.

  As described above, according to the present embodiment, the system control unit 10 checks whether or not to receive a current detection signal from the welding machine 1 after instructing the welding machine 1 to start the welding machine without high frequency. Thus, it is possible to determine whether the TIG welding electrode 8 and the base material 9 are short-circuited.

(Embodiment 2)
The configuration of the device in the present embodiment is shown in FIG. 2, and is different from the first embodiment in that a short-circuit determining unit 2 c is provided in the welding machine control unit 2 instead of the short-circuit determining unit 10 a in the system control unit 10. Yes. In addition, the same components as those in the first embodiment are denoted by the same reference numerals and redundant description is omitted.

  In the present embodiment, the system control unit 10 can arbitrarily transmit a welding activation command and a short circuit detection command to the activation method selection means 2a provided in the welding machine control unit 2 as necessary. When receiving a welding activation command, the activation method selection means 2a of the welding machine control unit 2 activates the high-frequency output unit 4 and the welding output unit 3 and notifies the short-circuit determination unit 2c that the welding activation is normal. . Since a high frequency voltage and a welding voltage are applied to the welding electrode 8, an arc is generated between the base material 9 and welding is normally performed. At this time, the current detector 6 detects the current and notifies the short-circuit determining means 2c, but since the short-circuit determining means 2c has already been notified that the normal welding is started, it is determined that the electrode is short-circuited even if the current detection notification is received. do not do. Next, when a short circuit detection command is received, the welding machine control unit 2 activates only the welding machine output unit 3 and notifies the short circuit determination means 2c that it is a short circuit detection operation. If there is no current detection notification from the current detection unit 6, the short-circuit determination means 2c indicates that the electrode 8 and the base material 9 are not short-circuited, and if the current detection notification is received, the electrode 8 and the base material 9 are short-circuited. The system control unit 10 is notified through the external output means 2b provided in the welding machine control unit 2.

  That is, in this embodiment, the system control unit 10 makes a status inquiry between the electrode and the base material to the TIG welding machine 1, the TIG welding machine 1 confirms the status, and returns a determination result to the system control unit 10. It has become.

  Since the means for detecting a short circuit between the electrode and the base material of the present invention is carried out without providing a special short circuit detection circuit, an automatic TIG welding system with a short circuit detection function can be provided at low cost, which is industrially useful.

The figure which shows the structure of the TIG welding apparatus in Embodiment 1 of this invention. The figure which shows the structure of the TIG welding apparatus in Embodiment 2 of this invention. The figure which shows the short circuit detection circuit of the conventional electrode short circuit detection means

Explanation of symbols

2a Start-up method selection means 2b External output means 2c 10a Short-circuit determination means 3 Welding output section 4 High-frequency output section

Claims (4)

A welding output section for generating a welding output voltage for performing welding, a high-frequency output section for generating a high-frequency high-frequency voltage superimposed on the welding output voltage and performing an arc start, and the welding output voltage and the high-frequency voltage simultaneously. A TIG welding machine comprising a starting method selection means having at least two kinds of starting methods: a starting method that generates and a starting method that generates only the welding output voltage. 2. The TIG welder according to claim 1, further comprising a short-circuit detecting means for detecting the presence or absence of a short circuit between the electrode and the base material based on the presence or absence of a welding current when a starting method for generating only the welding output voltage is selected. A TIG welding machine further comprising an external output means for outputting that the electrode is in a short circuit state when a short circuit between the electrode and the base material is detected by the short circuit detection means. The activation method selection means has at least two activation methods of an activation method that simultaneously generates a welding output voltage and a high-frequency voltage and an activation method that only generates a welding output voltage alone, and the two activation methods include: The TIG welding machine according to any one of claims 1 to 3, wherein the TIG welding machine can be arbitrarily selected by a signal from the outside.

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