JP2000288731A - Arc welder and arc start auxiliary device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an arc welder of a small power loss and light wt. and small size and can use even to AC welding current. SOLUTION: A positive pole side of a DC electric source 1 is connected with an output terminal 11 through an ammeter 19. Further, the one side of terminal in the circuit connected in parallel with a diode 12 and a switch 30, is connected with a negative pole side of the DC electric source 1 by making the direction of the diode 12 into the direction, to which the current of the DC electric source 1 flows, and the other side of terminal is connected with an output terminal 10. Further, a start auxiliary device 16 connected with a high voltage DC electric source 13, diode 14 and switch 15 in series between the output terminals 10, 11, is connected so as to match to the polarity of the DC electric source 1. Then, when the arc is started, the DC electric source 1 is connected with the switch 15 under state of opening the switch 30, and when the ammeter 19 detectes the welding current, the switch 15 is opened and the switch 30 is closed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arc welding machine and an arc start assist device capable of generating an arc in a welding load circuit in a non-contact manner.

[0002]

2. Description of the Related Art When performing TIG welding by a DC arc welding machine, an electrode is connected to a negative electrode side of the arc welding machine, and a base material is connected to a positive electrode side. During welding, an appropriate welding result can be obtained by maintaining the distance between the electrode tip and the base material at 5 to 8 mm. However, since the no-load voltage of the arc welding machine is about 100 V, the electrode tip and the base material are 5-8.
If it is mm apart, an arc cannot be generated (started) at the start of welding. For this reason, when an operator carries out welding with a welding torch, a high-frequency generation circuit is connected to the output circuit of the arc welding machine, and the arc is started in a state where high frequency is generated.

However, for example, when a welding torch is mounted on a robot to perform TIG welding, the high frequency generated from the high frequency generating circuit becomes noise and the robot control circuit may malfunction. For this reason, when performing TIG welding by a robot, a high-voltage DC start method of applying a high DC voltage between an electrode and a base material is adopted instead of the high-frequency generation circuit.

FIG. 5 is a connection diagram of an arc welding machine employing a conventional high-voltage DC start method. In the figure, reference numeral 1 denotes a power supply unit of the arc welding machine P. The power supply unit 1 rectifies an AC commercial power supply 2 to DC by a rectifier circuit 3 and smoothes the DC power by a capacitor 4. Then, the rectified DC is converted into a high-frequency AC by the inverter 5 and converted into a voltage suitable for TIG welding by the welding transformer 6, and then the AC output of the welding transformer 6 is converted into rectifiers 7a and 7a.
b and converted into a direct current by the rectifier circuit 8 composed of b and output. The DC current output from the power supply unit 1 is supplied to a DC reactor 9.
And a DC current having an external characteristic of a constant current characteristic is output from the output terminals 10 and 11.

One terminal of DC reactor 9 and output terminal 1
Between 0 and 0, high-voltage diodes 12 (three in series in the figure) that can withstand high voltage are arranged in a direction in which a DC current output from the rectifier circuit 8 can flow.
The output voltage is 5,000 at the output terminals 10 and 11.
A start auxiliary circuit 16 in which a high voltage DC power supply 13 of about V, a diode 14 and a switch 15 are connected in series is connected in parallel with the rectifier circuit 8 with the same polarity as the rectifier circuit 8. An electrode 17 held by a welding torch T is connected to the output terminal 10, and a base material 18 is connected to the output terminal 11. Reference numeral 19 denotes a current detector which is arranged in an output circuit of the power supply unit 1.

Next, the operation of the conventional arc welding machine P will be described. At the start of welding, that is, at the time of arc start,
The switch 15 is closed with the inverter 5 turned on.
Then, the output terminals 10 and 11, that is, the electrode 17 and the base material 1
8, the output voltage of the high-voltage DC power supply 13 is applied. When the electrode 17 and the base material 18 are in an insulated state, no current flows from the high-voltage DC power supply 13 to the power supply unit 1 due to the high breakdown voltage diode 12. When the insulation between the electrode 17 and the base material 18 is broken by the output voltage of the high-voltage DC power supply 13 to be in a conductive state, a current flows from the power supply 1 and the electrode 1
7. An arc is generated between the base material 18 and a detection signal is output from the current detector 19 which detects this current. Then, when the detection signal is output from the current detector 19, the switch 15 is opened.

[0007]

However, at the time of welding, a welding current flows through the high voltage diode 12. Generally, a high voltage diode has a high forward voltage (that is, a large internal resistance), and therefore has a large power loss due to resistance heating. Further, a cooling means for the high voltage diode 12 which generates heat must be provided inside the arc welding machine, and the volume and the weight of the arc welding machine P are large. Also, since the output current is only DC, the types of work that can be welded are limited.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in the prior art, to reduce power loss, to be lightweight and compact, and to be able to use an alternating welding current and an arc welding machine and an arc start auxiliary device. To provide.

[0009]

In order to achieve the above object, according to the first aspect of the present invention, a DC power supply, a high voltage DC power supply having a high output voltage, a first diode, and switching means are connected in series. A start auxiliary circuit, a second diode, and a current detector. The output terminal of the DC power supply and the terminal of the start auxiliary circuit are connected in parallel with the same polarity, and the direction of the second diode is changed. The start auxiliary circuit is arranged between one of the output terminals and one of the terminals of the start auxiliary circuit so that the current of the start auxiliary circuit does not flow into the DC power supply, and the current detector is disposed in the output circuit of the DC power supply. And, in an arc welding machine connecting both ends of the start assist circuit to a welding load circuit, a switch is provided,
This switch is connected in parallel with the second diode,
At the time of arc start, the DC power supply and the switching means are turned on with the switch opened, and when the current detector detects a welding current, the switch is opened and then the switch is closed. .

According to a second aspect of the present invention, there is provided a DC power supply, a high-voltage DC power supply having a high output voltage value, a start auxiliary circuit in which a first diode and switching means are connected in series, a second diode, An output terminal of the DC power supply and a terminal of the start auxiliary circuit are connected in parallel with the same polarity, and a current of the start auxiliary circuit flows into the DC power supply in a direction of the second diode. In one direction, disposed between one of the output terminals and one of the terminals of the start auxiliary circuit, the current detector is disposed in the output circuit of the DC power supply, and both ends of the start auxiliary circuit are welded load circuits. An arc welding machine connected to the converter, a conversion circuit for converting the output of the DC power supply to DC or AC, and a switch are provided, and an output terminal of the DC power supply is an input terminal of the conversion circuit. Connected, the output terminal of the conversion circuit and the terminal of the start auxiliary circuit are connected in parallel, and the second diode is connected to one of the output terminals in such a direction that the current of the start auxiliary circuit does not flow into the DC power supply. A switch connected in parallel with the second diode, and a DC output that matches an output of the conversion circuit with the polarity of the start auxiliary circuit at the time of arc start; When the switch is opened, the DC power supply and the opening / closing means are turned on, and when the current detector detects a welding current,
The switch is closed after opening the opening / closing means, and thereafter, the output of the conversion circuit is set to DC or AC output, and control is performed so as to supply DC or AC power to the welding load circuit. .

The invention of claim 3 is characterized in that, in claim 1 or claim 2, means for controlling the output current of the DC power supply at the time of arc start to several to several tens of amps is provided.

According to a fourth aspect of the present invention, a pair of input terminals, a pair of output terminals, a high-voltage DC power supply having a high output voltage value, a first diode, and a first switching means are connected in series. A start auxiliary circuit connected to the input terminal, a start circuit in which a DC power supply having a capacity capable of maintaining an arc, a second diode, a second switching means, and a current detector are connected in series, and a switch. One of the output terminals is connected to the other of the output terminals through the switch, the other of the input terminals is connected to the other of the output terminals, and the output of the start auxiliary circuit and the start circuit is matched with each other. It is characterized in that it is connected in parallel between the side terminals.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments. FIG. 1 is a connection diagram of a DC arc welding machine according to the present invention. Components having the same functions or the same functions as those in FIG. In the figure,
Reference numeral 30 denotes a switch (electromagnetic contactor), and a high-voltage diode 1
2 are connected in parallel. The contact resistance of the switch 30 is 1 milliohm or less, and the internal resistance value is small.

Next, the operation of this embodiment will be described. At the time of arc start, the switch 30 is opened, and the switch 15 is turned on with the inverter 5 turned on as in the conventional case.
Close. The electrode 1 is controlled by the output voltage of the high-voltage DC power supply 13.
7. When the conduction between the base material 18 is established, a current flows from the power supply unit 1 and an arc is generated between the electrode 17 and the base material 18. When the detection signal is output from the current detector 19, the switch 1
5 is opened and the switch 30 is closed. Then, all the current is diverted to the switch 30 side having a small internal resistance, and the current flowing through the high voltage diode 12 becomes zero. As a result, the heat value of the high voltage diode 12 becomes zero except for a short start time, and there is no need to provide a cooling device. Further, since the amount of heat generated by the switch 30 is small, there is no need to provide a cooling device. When the desired welding is completed, the inverter 5 is turned off and the switch 30 is opened to prepare for the next welding.

The reason why all the current is commutated to the switch 30 when the switch 30 is closed is as follows. That is, the diode has a characteristic that the current does not flow unless the voltage at both ends becomes higher than a certain voltage. In the case of this embodiment, the high breakdown voltage diode 12 is 3
Even if the current value is 500 A, the voltage 1700 across each high-voltage diode 12
Only about mV, no current flows.

FIG. 2 is a connection diagram of an AC / DC dual-purpose arc welding machine according to the present invention. Components having the same functions or functions as those in FIGS. In the figure,
Reference numeral 31 denotes a conversion circuit. The input side terminal is connected to the output terminal of the power supply unit 1, one of the output side terminals is connected to the cathode side of the high voltage diode 12 via the reactor 9, and the other is connected to the current detector 19 via the current detector 19. And is connected to the output terminal 11 to convert a DC current output from the power supply unit 1 into an AC current or a DC current.

Next, the operation of this embodiment will be described. 3 is a timing chart showing the operation of each part in FIG. 2, where A is the on / off signal of the power supply unit 1, B is the output voltage of the power supply unit 1, C is the welding current flowing through the high voltage diode 12, and D is Denotes an on / off signal of the switch 15, E denotes an output signal of the current detector 19, and F denotes an on / off signal of the switch 30.

When an arc is started, the current value output from the conversion circuit 31 in advance is a number that can maintain the arc.
While setting the power supply unit 1 to be tens of amperes,
The output of the conversion circuit 31 is set to a DC output that matches the polarity of the start auxiliary circuit 16. The switch 30 is kept open. In this state, when the power supply unit 1 (inverter 5) is turned on and the switch 15 is closed (time T0), a high voltage of about 5,000 V is applied between the electrode 17 and the base material 18. A no-load voltage of about 100 V is output to both ends of the power supply unit 1. Electrode 1 by high voltage DC power supply 13
7. When the base material 18 becomes conductive, a welding current flows to the power supply unit 1 via the high voltage diode 12, an arc is generated, and a detection signal is output from the current detector 19 (time T1). Next, the switch 15 is opened (time T
2) The switch 30 is closed (time T3). Then, all the current flowing through the high breakdown voltage diode 12 is diverted to the switch 30 side having a small internal resistance, and the high breakdown voltage diode 12
Is zero. Next, the output of the conversion circuit 31 is set to the AC output (time T4), and the output current value is set to the welding current value. When the welding is completed, the power supply unit 1 is turned off and the switch 30 is opened (time T5).

In the case of this embodiment, the power loss is
In addition, the high voltage diode 12 may be capable of supplying a current of several to several tens of amps at the start of welding, and the capacity may be reduced to approximately 1/10 or less of that of the conventional one. Can be.

Since not only DC welding but also AC welding can be performed, welding of aluminum or the like can be performed, and works of almost all materials can be welded.

In the above description, DC is applied until the switch 30 is closed, and AC is applied after the switch 30 is closed. However, AC may be set from the beginning.

FIG. 4 is a view showing an arc start assist device according to the present invention. Components having the same functions or the same functions as those shown in FIGS. In the figure, 3
Reference numeral 5 denotes an arc start assist device, which includes a pair of input terminals and 36a and 36b, and a pair of output terminals 37a and 37b.
The input side terminal 36a and the output side terminal 37a are connected via the switch 30, and the input side terminal 36b and the output side terminal 37b are directly connected. Reference numeral 38 denotes a start circuit in which a DC power supply 39 having a capacity (about 800 VA) capable of maintaining an arc, a high-voltage diode 12, a switch 40, and a current detector 19 are connected in series. The start circuit 38 is connected between the output side terminals 37a and 37b in parallel with the start auxiliary circuit 16 with the same polarity as the start auxiliary circuit 16. Reference numeral 41 denotes a normal DC or AC arc welding power supply having no DC start control function or start current control function.

Next, the operation of the arc start assist device will be described. The arc welding power supply 41, switches 15, 3
0 and 40 are all turned off. First, the switch 15 and the switch 40 are closed. When the electrode 17 and the base material 18 are brought into conduction by the output voltage of the high-voltage DC power supply 13, a current flows from the DC power supply 39 via the high voltage diode 12, and an arc is generated between the electrode 17 and the base material 18. When the detection signal is output from the current detector 19, the switch 15 is opened and the arc welding power supply 41 is turned on. Then, the switch 40 is opened and the switch 30 is closed. When the welding is completed, the switch 30 is opened.

Using this arc start assist device,
Even a normal DC or AC arc welding power supply having no DC start control function or start current control function can be used as a power supply for robot welding, for example, in combination with a robot.

[0025]

As described above, according to the present invention,
An output terminal of the DC power supply, comprising a DC power supply, a high-voltage DC power supply having a high output voltage value, a start auxiliary circuit in which a first diode and switching means are connected in series, a second diode, and a current detector; And the terminal of the start auxiliary circuit are connected in parallel with the same polarity, and the direction of the second diode is set so that the current of the start auxiliary circuit does not flow into the DC power supply. A switch is provided in an arc welding machine that is disposed between one of terminals of an auxiliary circuit, the current detector is disposed in an output circuit of the DC power supply, and both ends of the start auxiliary circuit are connected to a welding load circuit. This switch is connected in parallel with the second diode, and at the time of arc start, the DC power supply and the opening / closing means are turned on with the switch opened, and the power supply is turned on. When the detector detects the welding current, since control to open the closing means to close the switch, can reduce the power loss at the time of welding, moreover it is possible to reduce the weight, small in size. Further, by providing a conversion circuit for converting the output of the DC power supply into an AC, an AC welding current can be used, and works of various materials can be welded.

[Brief description of the drawings]

FIG. 1 is a connection diagram of a DC arc welding machine according to the present invention.

FIG. 2 is a connection diagram of a dual-use arc welding machine according to the present invention.

FIG. 3 is a timing chart showing the operation of each unit in FIG.

FIG. 4 is a view showing an arc start assist device according to the present invention.

FIG. 5 is a connection diagram of an arc welding machine employing a conventional high-voltage DC start method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 DC power supply 10 Output terminal 11 Output terminal 12 Diode 13 High voltage DC power supply 14 Diode 15 Switch 16 Start auxiliary circuit 19 Current detector 30 Switch

Claims (4)

[Claims] 1. A DC power supply, a high-voltage DC power supply having a high output voltage value, a start auxiliary circuit in which a first diode and switching means are connected in series, a second diode, and a current detector, The output terminal of the DC power supply and the terminal of the start auxiliary circuit are connected in parallel with the same polarity, and the direction of the second diode is set so that the current of the start auxiliary circuit does not flow into the DC power supply, and the output terminal And an electric current detector is arranged in an output circuit of the DC power supply, and both ends of the start auxiliary circuit are connected to a welding load circuit. , A switch, and this switch is connected in parallel with the second diode. At the time of arc start, the DC power supply and the switching means are turned off with the switch opened. When the current detector detects a welding current, the switch is closed after opening the opening / closing means. 2. A power supply comprising: a DC power supply; a high-voltage DC power supply having a high output voltage value; a start auxiliary circuit in which a first diode and switching means are connected in series; a second diode; and a current detector, The output terminal of the DC power supply and the terminal of the start auxiliary circuit are connected in parallel with the same polarity, and the direction of the second diode is set so that the current of the start auxiliary circuit does not flow into the DC power supply, and the output terminal And an electric current detector is arranged in an output circuit of the DC power supply, and both ends of the start auxiliary circuit are connected to a welding load circuit. A conversion circuit for converting the output of the DC power supply into DC or AC, and a switch,
An output terminal of the DC power supply is connected to an input terminal of the conversion circuit, an output terminal of the conversion circuit and a terminal of the start auxiliary circuit are connected in parallel, and the current of the start auxiliary circuit is connected to the second diode. The switch is connected in parallel with the second diode in a direction that does not flow into the DC power supply, and is disposed between one of the output terminals and one of the terminals of the start auxiliary circuit. Is set to a DC output according to the polarity of the start auxiliary circuit, the DC power supply and the switching means are turned on with the switch opened, and when the current detector detects a welding current, the switching is performed. After the means is opened, the switch is closed, and then the output of the conversion circuit is set to DC or AC output, so that DC or AC power is supplied to the welding load circuit. Arc welder and controls to supply. 3. An arc welding machine according to claim 1, further comprising means for controlling the output current of said DC power supply at the time of arc start to several to several tens of amperes. 4. A pair of input terminals, a pair of output terminals, a high-voltage DC power supply having a high output voltage value, a start auxiliary circuit in which a first diode and first switching means are connected in series. A start circuit in which a DC power supply having a capacity capable of maintaining an arc, a second diode, a second switching means, and a current detector are connected in series, and a switch, and one of the input-side terminals and the output-side terminal are provided. One is connected via the switch, the other of the input terminals is connected to the other of the output terminals, and the start auxiliary circuit and the start circuit are connected in parallel between the output terminals with matching polarities. An arc start assist device characterized in that: