JP3368776B2 - TIG 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 TIG welding machine provided with a high frequency generator for starting an arc.

[0002]

2. Description of the Related Art Generally, a TIG welding machine is equipped with a high-frequency generator for starting an arc, because the electrode and the base material are not in contact with each other when starting the arc of the TIG welding machine.

A conventional TIG welding machine having a high frequency generator for starting an arc will be described below with reference to FIGS. 4 and 5.

In FIGS. 4 and 5, 1 is a primary side rectifier circuit for converting a three-phase or single-phase AC input into direct current, and 2 is a power source for converting direct current rectified by the primary side rectifier circuit into alternating current. Inverter circuit for controlling, 3 is the inverter circuit 2
Transformer that converts the AC output of the AC into a voltage suitable for welding, 4
Is a secondary side rectifier circuit for rectifying the AC output of the main transformer 3, 5 is a diode bridge rectifier circuit for inputting DC power to the arc starting high frequency generator 6, and 7 is the arc starting high frequency generator 6 Is a high-frequency generator 6 for starting an arc.
Is a down transformer for supplying power to, 8 is an electrode, and 9 is a base material.

Next, the operation of the TIG welding machine shown in FIG. 4 will be described. When a start signal is input to the TIG welding machine, the inverter circuit 2 operates, an AC voltage is generated on the secondary side of the main transformer 3, and the AC voltage is rectified by the rectifier circuit 4 to become an output voltage and become an electrode 8. It is supplied between the base materials 9.
On the other hand, the arc starting high frequency generator 6 is supplied with a voltage obtained by rectifying the commercial AC voltage from the input side of the welding machine through the down transformer 10 and the diode bridge rectifier circuit 5, and the arc starting high frequency generator 6 is supplied by the starting signal. Starts transmitting and applies a high frequency voltage between the electrode 8 and the base material 9 through the coupling coil 7. This high frequency voltage causes dielectric breakdown between the electrode 8 and the base material 9 to form an arc discharge circuit with the main circuit and start welding. Then, when the welding current is detected, the high frequency generator 6 automatically stops its operation.

In order to simplify the circuit of the TIG welding machine, there is also a TIG welding machine in which the input voltage of the arc starting high frequency generator is taken from the output side of the welding machine as shown in FIG.

Next, the operation of the TIG welding machine shown in FIG. 5 will be described. When a start signal is input to the TIG welding machine, the inverter circuit 2 operates, an AC voltage is generated on the secondary side of the main transformer 3, and the AC voltage is rectified by the rectifier circuit 4 to become a DC voltage. Supplied in between. On the other hand, the arc activating high-frequency generator 6 is supplied with the voltage rectified by the rectifier circuit 4, and the arc activating high-frequency generator 6 starts transmitting by the activation signal, and the high-frequency voltage is supplied to the electrode 8 through the coupling coil 7. It is applied between the base materials 9. This high frequency voltage causes dielectric breakdown between the electrode 8 and the base material 9 to form an arc discharge circuit with the main circuit and start welding.

[0008]

If the above-mentioned conventional structure is adopted, a high frequency voltage can be supplied between the electrode 8 and the base material 9 at the start of welding, and non-contact arc starting in TIG welding becomes possible.

However, in the structure shown in FIG. 4, since it is necessary to provide the down transformer 10 for supplying the arc starting high frequency generator 6 with power, it is difficult to realize the downsizing of the TIG welding machine.

Further, in the conventional configuration of FIG. 5, the voltage rectified by the normal rectification circuit 4 becomes one half of the voltage across the secondary winding of the main transformer 3, and the arc starting high frequency generator 6 causes the voltage. It was not enough to generate a high frequency voltage that can perform a stable arc start.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a TIG welding machine that is small in size and that improves arc start performance and reduces noise.

[0012]

In order to achieve this object, the TIG welding machine according to the first means of the present invention is installed on the primary side.
A TIG welding machine including a main transformer having a center tap for arranging a barter circuit and converting an AC input into a voltage suitable for welding, and a secondary side rectifying circuit for rectifying an output of the main transformer, A high-speed rectifier circuit that receives an AC voltage output from both ends of the secondary winding of the main transformer and rectifies the AC voltage, and a determination circuit that outputs a signal when the output voltage of the high-speed diode bridge exceeds a set value. And a high frequency generator for arc starting which generates a high frequency voltage according to the signal of the discrimination circuit.

The second means of the present invention is, after the arc start signal is inputted to the TIG welding machine of the first means,
A breaking circuit is provided for breaking the input circuit to the arc starting high-frequency generator when the current is not detected within a fixed time.

A third means of the present invention is that the discrimination circuit of the TIG welding machine of the first means or the second means is a discrimination circuit having two or more selectable discrimination values.

[0015]

According to the constitution of the first means of the present invention, the AC no-load voltage outputted to the secondary winding of the main transformer of the TIG welding machine at the start of welding is rectified by the high-speed rectification circuit, It has a function of generating a high-frequency voltage for arc starting when input to the high-frequency generating device for arc starting and the input voltage value exceeds a set value.

Further, the structure of the second means of the present invention has the function of stopping the high frequency voltage when the arc does not occur within a fixed time.

Further, according to the configuration of the third means of the present invention, T
By selecting the discriminant value of the discriminating circuit according to the usage conditions of the IG welding machine, the value of the high frequency voltage can be changed.

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. (Embodiment 1) FIG. 1 shows an inverter type TI according to the present invention.
1 shows the first embodiment when applied to a G welding machine. In FIG. 1, 1 is a primary side rectifier circuit that converts a three-phase or single-phase AC input into direct current, 2 is an inverter circuit that converts direct current rectified by the primary side rectifier circuit into alternating current, and controls power A main transformer 4 for converting the alternating current into a voltage suitable for welding, a secondary rectifier circuit 4 for rectifying the output of the main transformer 3,
5 is a high-speed diode bridge rectifier circuit (high-speed rectifier circuit) for rectifying the AC voltage output from the secondary winding of the main transformer 3 and inputting DC power to the arc-starting high-frequency generator 6, and 13 is for smoothing The condenser, 14 is the rectifying circuit 5
Zener diode (discrimination circuit) that conducts when the output voltage of the power supply exceeds a set value, 6 is a high frequency generator for arc starting,
Reference numeral 7 is a coupling coil, 8 is an electrode, and 9 is a base material.

Next, the operation of the TIG welding machine according to the first embodiment will be described.

When a start signal is input to the TIG welding machine, the inverter circuit 2 operates, an AC voltage is generated on the secondary side of the main transformer 3, and the AC voltage is rectified by the rectification circuit 4 and becomes an output voltage. It is supplied between the electrode 8 and the base material 9. Then, when there is no load until an arc is generated between the electrode 8 and the base material 9, the output voltage is a no-load voltage and its value is about 40V to 80V. Then, in the high-frequency generator 6 for arc starting, the AC voltage generated between both ends of the secondary winding of the main transformer 3 is rectified through the high-speed rectification circuit 5 for rectification and smoothed by the smoothing capacitor 13. Is supplied. The value of the AC voltage is about 80V to 160V when no load is applied.
The rectified voltage charges the smoothing capacitor 13, and when the charged voltage exceeds the Zener voltage (set voltage) of the determination circuit 14, the signal of the determination circuit 14 operates the arc starting high frequency generator 6 to generate a high frequency voltage. . in this way,
When the arc starting high frequency generator 6 operates, the charging voltage of the smoothing capacitor 13 decreases due to the operating current, and the generation of the high frequency voltage stops. Further, when the smoothing capacitor 13 is charged again and the charging voltage exceeds the set voltage of the discrimination circuit 14, the high frequency voltage is generated as described above, and these operations are repeated. This high frequency voltage is applied between the electrode 8 and the base material 9 via the coupling coil 7, and the high frequency voltage causes dielectric breakdown between the electrode 8 and the base material 9 to form an arc discharge circuit with the main circuit. It is formed and welding is started.

Since the main circuit of the TIG welding machine is usually composed of a high-speed inverter circuit, the AC voltage generated across the secondary winding of the main transformer 3 has a frequency of several kHz to several tens of kHz. Therefore, by using a high-speed rectifier element in the high-speed rectifier circuit 5, it can be widely applied from a high-speed inverter to a commercial frequency rectifier system using a general-purpose thyristor.

Further, the input voltage of the arc starting high-frequency generator 6 rises because the high-speed AC voltage generated across the secondary winding of the main transformer 3 is full-wave rectified by the high-speed rectifier circuit 5. Is fast and the secondary side rectifier circuit 4
It is possible to obtain twice the voltage as compared with the output voltage rectified by. Thereby, the high frequency generator 6 for starting the arc
The high frequency voltage output from the device can obtain a high voltage and a fast response speed, and the high frequency voltage can be quickly applied between the electrode 8 and the base material 9 to improve the arc start performance.

When welding is started, the arc voltage between the electrode 8 and the base material 9 is lowered, so that the AC voltage across the secondary winding of the main transformer 3 is also lowered, and the arc starting high-frequency generator is generated. The input voltage to 6 also decreases, and the high-frequency generator 6 for starting an arc automatically stops operating at the same time as the arc is generated without a high-frequency stop signal.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to FIG. In FIG. 2, reference numerals 1 to 14 are the same as those in FIG.

FIG. 2 shows an input circuit to the arc starting high frequency generator 6 when the current is not detected in the main circuit within a fixed time after the arc starting signal is input, as compared with FIG. A shutoff circuit for shutting off is provided. That is, 18 is a current detector that detects the flow of current in the main circuit, 19 is a timer circuit that receives a start signal and outputs a high-frequency stop signal when the current is not detected within a certain period of time, 2
Reference numeral 0 is a cutoff circuit which receives the signal from the timer circuit 19 and cuts off the input circuit to the arc starting high frequency generator 6.
The configuration other than the cutoff circuit 20 is the same as that in FIG.

In the TIG welding machine shown in FIG. 2, the basic operation up to the generation of high frequency is the same as the circuit operation shown in FIG. 2, but the timer circuit 19 uses the current detector 18 within a fixed time after the start signal is input. When the current detection signal from the circuit is not input, the high frequency stop signal is sent to the cutoff circuit 20, and the cutoff circuit 20 cuts off the input circuit to the arc starting high frequency generator 6 to stop the high frequency. Therefore, even when the arc start fails, the generation of high frequency noise can be minimized.

(Third Embodiment) A TIG welding machine according to a third embodiment of the present invention will be described below with reference to FIG.
In FIG. 3, reference numerals 1 to 13 are the same as those in FIG.

In FIG. 3, two or more discriminant values of the discriminator circuit 14A are selectable with respect to FIG. 1, 14a is a first Zener diode having a first discriminant value, and 14Sa is a first Zener diode 14a. First switch, 14b
Is a second Zener diode having a second discriminant value, 14Sb
Is a second switch for selecting the second Zener diode 14b, and the parts other than this discrimination circuit 14A are the same as those in FIG.

The basic operation of the TIG welding machine of FIG. 3 is the same as the circuit operation of FIG. 1, but the first Zener diode 14a and the second Zener diode 14 are used.
By setting the discriminant value of b to a value according to the usage conditions of the welding machine such as the cable length of the main circuit, it is only necessary to selectively turn on the first switch 14Sa or the second switch 14Sb, and the high frequency for arc starting can be set. The operating voltage of the generator 6 can be changed to change the value of the high frequency voltage. For example, if the first Zener diode 14a is set to a low value selected when the output cable of the welding machine is short, and the second Zener diode 14b is set to a high value selected when the output cable of the welding machine is long, If the output cable is short, the high-frequency voltage will be low if the first switch 14Sa is closed, and high-frequency noise can be suppressed while ensuring arc start performance. If the output cable is long, the high-frequency voltage can be reduced by closing the second switch 14Sb. The voltage goes up,
The arc start performance can be maintained. Needless to say, the number of Zener diodes and switches can be increased by the number of conditions.

Further, as the discrimination circuit 14A, it is possible to use a configuration such as a clamp circuit other than the Zener diode.

[0031]

As described above, according to the first means of the present invention, it is possible to realize the downsizing of the welding machine while improving the arc start performance, and the high frequency is stopped at the same time when the welding is started. High-frequency noise can be reduced, and the high-frequency voltage is generated at the input voltage value that is set by determining the input voltage to the high-frequency generator for arc starting. Therefore, the voltage between the secondary windings of the main transformer fluctuates. However, it has an excellent effect that the high-frequency voltage for starting the arc is hardly affected by it.

Further, according to the second means of the present invention, the high frequency voltage is stopped even when the arc is not started.
This has an excellent effect that the influence of high frequency noise on peripheral devices can be suppressed.

Further, according to the third means of the present invention, the value of the high frequency voltage can be selected according to the use conditions of the welding machine such as the cable length of the main circuit, so that even if the output side cable of the welding machine is extended. It has an excellent effect of obtaining a good arc start.

The present invention can be easily applied to a conventional circuit configuration and has an extremely excellent effect of obtaining a good arc start.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a TIG welding machine according to a first embodiment of the present invention.

FIG. 2 is a circuit configuration diagram of a TIG welding machine according to the second embodiment.

FIG. 3 is a circuit configuration diagram of a TIG welding machine according to the third embodiment.

FIG. 4 is a circuit configuration diagram of a conventional TIG welding machine.

FIG. 5 is a circuit configuration diagram of another conventional TIG welding machine.

[Explanation of symbols]

3 main transformer 4 Secondary side rectifier circuit 5 High-speed rectifier circuit 6 High frequency generator for starting arc 14,14A discrimination circuit 20 Breaking circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-264167 (JP, A) JP-A-8-164480 (JP, A) Actually open 61-22264 (JP, U) Actually open 6- 19972 (JP, U) Actual Kaihei 5-70766 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) B23K 9/067 B23K 9/073 B23K 9/167

Claims (3)

(57) [Claims] 1. A main transformer having an inverter circuit arranged on the primary side and having a center tap for converting to a voltage suitable for AC input welding, and a secondary side rectifying circuit for rectifying the output of the main transformer. A TIG welder, which has two main transformers
It has a high-speed rectifier circuit that receives the AC voltage output from both ends of the next winding and rectifies the AC voltage, and a determination circuit that outputs a signal when the output voltage of the high-speed rectification circuit exceeds a set value. A TIG welding machine equipped with a high-frequency generator for starting an arc that generates a high-frequency voltage by the signal of the circuit. 2. The TIG welding according to claim 1, further comprising a shut-off circuit for shutting off an input circuit to the high-frequency generator for arc starting when an arc starting signal is input and current detection is not performed within a fixed time. Machine. 3. The TIG welding machine according to claim 1, wherein the discriminating circuit has two or more discriminant values that can be selected, and the discriminant value can be selected depending on a welding machine usage condition such as cable extension. .