KR19980063921A - Plasma Arc Equipment - Google Patents

Abstract

It facilitates the generation of pilot arc.

The DC power supply circuit 2 supplies a DC voltage between the torch electrode 8 and the workpiece 10 when the open / close switch 24 is closed.

At the same time, the drive unit 28D is driven, and the solenoid valve 28 supplies compressed air from the compressor 20 between the torch electrode 8 and the workpiece 10 at the first flow rate.

The high frequency voltage generator 12 generates a pilot arc between the torch electrode 8 and the nozzle 11.

When a plasma arc occurs between the torch electrode 8 and the workpiece 10, the plasma arc detector 18 detects this and closes the open / close switch 32.

As a result, the drive unit 30D is driven, and compressed air is also supplied from the solenoid valve 30 between the torch 8 and the nozzle 11.

Description

Plasma Arc Equipment

The present invention relates to a device using a plasma arc, such as, for example, a plasma arc welder or a plasma arc cutter.

In the plasma arc cutting machine, a plasma gas is supplied between the nozzle and the torch electrode which are spaced around the torch electrode to generate the plasma arc.

In addition, a DC current is supplied between the torch electrode and the workpiece.

Again, a high frequency voltage is supplied between the torch electrode and the nozzle to promote the generation of plasma arc.

An example of this plasma arc cutting machine is shown in FIG.

This plasma arc cutting machine has a DC power supply circuit (2).

The DC power supply circuit 2 starts operation when the relay contact 4 is closed.

The relay contact 4 is closed when the relay drive unit 4D is energized.

The DC power supply circuit 2 operates to receive a commercial AC voltage from the input terminals 6 and 6 and convert it into a DC voltage.

This DC power supply circuit 2 has, for example, a first converter for rectifying and smoothing a commercial AC voltage.

The DC voltage of the first converter is converted into a high frequency voltage by the high frequency inverter.

The high frequency voltage is transformed by the insulation transformer and converted into a DC voltage by the second converter.

This DC voltage is generated between the negative electrode side output terminal (-) and the positive electrode side output terminal (+) of the DC power supply circuit 2.

The negative electrode side output terminal (-) is connected to the torch electrode 8 and the positive electrode side output terminal (+) to the workpiece 10.

Since there is a gap between the torch electrode 8 and the workpiece 10, no arc is generated by simply supplying a DC voltage to both.

Here, a pilot arc is generated between the torch electrode 8 and the nozzle 11 arranged at intervals around the torch electrode 8, based on which the torch electrode 8 and the torch electrode 8 are generated. Arc is generated between the workpieces 10.

For this reason, for example, a high frequency voltage generator 12 for generating a pulsed high frequency voltage of several KV is provided between the negative electrode side output terminal (-) and the torch electrode 8 of the DC power supply circuit 2. .

In addition, the current limiting resistor 14 and the open / close switch 16 are connected in series between the nozzle 11 and the positive electrode side output terminal (+) of the DC power supply circuit 2.

In addition, when the plasma current flows between the torch electrode 8 and the workpiece 10, the positive electrode side output terminal (+) of the workpiece 10 and the DC power supply 2 is controlled to maintain a constant value, that is, to control the constant current. The current detector 18 is provided in between.

The high frequency inverter is controlled so that this detection current is returned to the DC power supply circuit 2 and a constant plasma current flows.

A gas source, for example, an air compressor 20, is provided to supply gas for plasma generation, for example, compressed air, at a distance between the torch electrode 8 and the nozzle 11 for generating a plasma arc. .

The piping 21 is provided between this air compressor 20 and the said space | interval.

In this pipe 21, an electric valve, for example a solenoid valve 22, is provided.

This solenoid valve 22 is an open / close valve opened and closed by the drive part 22D.

The solenoid valve 22 supplies compressed air at the above-mentioned intervals at a predetermined flow rate in the valve-opening state and does not supply compressed air at the above-mentioned intervals in the valve closing state.

The relay drive unit 4D and the drive unit 22D of the solenoid valve 22 are connected in parallel.

This parallel circuit is connected between the power supply lines 26 and 26 in series with the on / off switch 24.

The on / off switch 24 is attached to the torch where the torch electrode 8 is provided.

As shown in Fig. 4A, when the on / off switch 24 is turned ON, the relay driving unit 4D and the driving unit 22D of the solenoid valve are energized and they operate.

The solenoid valve 22 is driven by the action of the driving part 22D of the solenoid valve, and as shown in the diagram (c), the compressed air from the air compressor 20 passes through the solenoid valve 22 at a predetermined flow rate. It is supplied in the gap between the fault electrode 8 and the nozzle 11.

At the same time, the relay contact 4 is closed by the operation of the relay driver 4D, and the nozzle 11 is opened from the DC power supply circuit 2 via the high frequency voltage generator 12, the current limiting resistor 14, and the opening / closing switch 16. ) And a torch electrode are supplied with a DC voltage.

The DC voltage is also supplied between the workpiece 10 and the torch electrode 8 via the high frequency voltage generator 12 and the current detector 18.

At this time, since there is a gap between the workpiece 10 and the torch electrode 8 and the torch electrode 8 and the nozzle 11 as described above, no arc is generated.

At this time, the interval between the torch electrode 8 and the nozzle 11 is larger than the interval between the workpiece 10 and the torch electrode 8.

Here, the high frequency voltage generator 12 is operated in connection with the closure of the relay contact 4 to generate a pilot arc between the nozzle 11 and the torch electrode 8, as shown in Fig. 4B. Similarly, a pilot arc is generated between the nozzle 11 and the torch electrode 8.

In this state, for example, a pilot current of 15 A flows between the nozzle 11 and the torch electrode 8.

In this state, when the torch electrode 8 and the nozzle 11 are brought close to the workpiece 10, the distance between the torch electrode 8 and the workpiece 10 is reduced, and the pilot arc described above is piloted so that Fig. 4 ( As shown in d), a main current flows between the torch electrode 8 and the workpiece | work 10. As shown to FIG.

This main current is detected by the current detector 18 and returned to the DC power supply circuit 2, and the DC power supply circuit 2 is constant current controlled so that a current of 70 A flows, for example.

In addition, since the current detector 18 detects that the main current has flown, the open / close switch 16 is opened and the pilot current is cut off.

At the same time, the high frequency voltage generator 12 is also stopped.

Moreover, compressed air is made into plasma by generation | occurrence | production of pilot arc and a main electric current.

When the plasma arc cutting machine is stopped, the open / close switch 24 is opened.

As a result, the energization of the relay driver 4D and the solenoid valve driver 22D is stopped.

The relay contact 4 is opened by the energization stop to the relay drive part 4D, and the DC power supply circuit 2 is stopped.

At the same time, the solenoid valve 22 is closed by the energization stop to the solenoid valve drive part 22D, and supply of compressed air is stopped.

In the plasma arc cutting machine as described above, compressed air is supplied between the nozzle 11 and the torch electrode 8 from the time of generating the pilot arc.

Moreover, this compressed air is the flow rate required at the time of the plasma arc generation.

For example, when the main current (cutting current) is set to 70 A, the flow rate is 270 l / min.

Because of this large flow rate, there is a problem that the pilot arc does not occur satisfactorily.

As a technique for solving this problem, the DC power supply circuit 2 generates power to increase the power generated by the high frequency voltage generator 12 or to increase the voltage supplied between the nozzle 11 and the torch electrode 8. It is conceivable to increase the voltage or decrease the value of the current limiting resistor 14 so that a large number of pilot currents flow.

However, in these techniques, the capacity of the high frequency voltage generator 12 or the DC power supply circuit 2 must be made large, and the current limiting resistor 14 must be made large in order to prevent damage even if a large current flows. Can not be done.

In addition, although the above-mentioned plasma arc cutting machine uses compressed air, an inert gas such as argon may be used, for example, gas for plasma generation.

This gas is contained in a cylinder or the like and has a limit on its capacity.

Gases with a limit in this capacity are used in vain at the time of pilot arc generation.

1 is a block diagram of one embodiment of a plasma cutting machine according to the present invention;

2 is an operation explanatory diagram of an embodiment

3 is a block diagram of an example of a conventional plasma cutting machine;

4 is an explanatory view of the operation of the plasma cutting machine of FIG.

(Explanation of symbols for the main parts of the drawing)

2. DC power circuit (DC power supply means)

8. Torch Electrode

10. Workpiece

11. Nozzle

12. High frequency voltage generator (pilot arc generating means)

18. Plasma arc detector

20. Compressor (gas supply source)

28,30. Solenoid valve (flow control means)

28D, 30D. Drive part (flow control means)

In order to solve the above problem, in the invention described in claim 1, the DC power supply means supplies a DC voltage between the torch electrode and the workpiece when the bias signal is supplied.

When the bias signal is supplied, the pilot arc generating means generates a pilot arc between the nozzle and the torch electrode arranged at intervals around the torch electrode.

The gas flow rate adjusting means supplies the gas at a selected flow rate among the first flow rate and the second flow rate more than that between the nozzle and the torch electrode from the source of the plasma arc generation gas.

When a plasma arc is generated between the torch electrode and the workpiece, the plasma arc detection signal generates a plasma arc detection signal.

The flow rate control means such that the flow rate of the gas from the gas flow rate adjusting means is the first flow rate when the bias signal is generated and the flow rate of the gas from the gas flow rate adjusting means is the second flow rate when the plasma arc detection signal is generated. The gas flow rate adjusting means is controlled.

According to the invention as set forth in claim 1, when the pilot arc generating means is operated to generate the pilot arc, the flow rate control means supplies the gas flow rate adjusting means with the gas between the nozzle and the torch electrode at the first flow rate.

When the plasma arc occurs, the flow rate control means supplies the gas to the gas flow rate adjusting means at a second flow rate, which is a flow rate greater than the first flow rate, between the nozzle and the torch electrode.

In the invention according to claim 2, in the invention according to claim 1, the gas flow rate adjusting means is constituted by the first and second flow rate adjusting means.

The first and second flow rate adjusting means are connected in parallel with each other.

The first flow rate adjusting means supplies gas at the first flow rate when the bias signal is closed in the non-supply state and the bias signal is supplied.

The second flow rate adjusting means is closed in the non-supply state of the plasma arc detection signal and supplies the gas at the flow rate of the difference between the first flow rate and the second flow rate in the supply state of the plasma arc detection signal.

According to the invention described in claim 2, when the pilot arc is generated, gas is supplied between the nozzle and the torch electrode only by the first flow rate adjusting means.

At the time of the generation of the plasma arc, in addition to the first flow rate adjusting means, gas is also supplied from the second flow rate adjusting means between the nozzle and the torch electrode.

Furthermore, the first and second flow rate adjusting means supplies gas at the first and second flow rates in a state where the bias signal or the detection signal of the plasma arc is being supplied, and stops the supply when the above-mentioned both signals are lost. The flow rate control means may be one capable of so-called ON / OFF control.

In the invention described in claim 3, in the invention according to claim 1, the DC power supply means is subjected to constant current control.

The plasma arc detection means detects a current flowing through the torch electrode and the workpiece, and this current is also supplied to the DC power supply means as a control signal for constant current control.

According to the invention as set forth in claim 3, the plasma arc detection means is not only used for detecting the plasma arc but also used for the constant current control of the DC power supply means.

(Example)

An embodiment of the present invention will be described with reference to FIGS. 1 and 2.

This embodiment also implements the present invention in a plasma arc cutting machine.

The same parts as those of the components of the conventional plasma arc cutting machine shown in Fig. 3 are given the same reference numerals, and the description thereof is omitted.

In addition, the DC power supply circuit 2 has a high frequency voltage generator 12 in the DC power supply means, the current limiting resistor 14, the open / close switch 16 in the plasma arc generating means and the air compressor 20 in the supply source of the plasma gas. Reference numeral 24 denotes the biased signal generation means and the current detector 18 corresponds to the plasma detection means, respectively.

There is a flow rate adjusting means provided in the pipe 21 as a difference between the plasma arc cutting machine shown in Fig. 3 and the present embodiment.

This flow rate adjusting means has an electric valve, for example, the solenoid valve 28,30.

These solenoid valves 28 and 30 are connected in parallel with each other.

When the solenoid valve 28 is not energized by the drive part 28D, it will be in a valve closing state, and will be in a valve open state when the drive part 28D is energized, and the 1st flow volume, for example, 70-90 L / min. The compressed air is supplied to the gap between the nozzle 11 and the torch electrode 8 at a flow rate of.

The solenoid valve 30 is in a valve-closed state when the drive unit 30D is not energized, and in a valve open state when the drive unit 30D is energized, for example, compressed air at a flow rate of 180 to 200 l / min. The gap is supplied to the gap between the nozzle 11 and the torch electrode 8.

Therefore, when the positron valves 28 and 30 are in operation, the compressed air is supplied to the interval between the nozzle 11 and the torch electrode 8 at a second flow rate, for example, about 270 L / min. .

This flow rate is, for example, the flow rate of the compressed air necessary for generating a plasma arc satisfactorily when the main current is set at 70 A.

The solenoid valve 30 shares the difference between the first flow rate and the second flow rate.

The drive part 28D of the electromagnetic open / close valve 28 is connected in parallel with the relay drive part 4D.

Therefore, when the open / close switch 28 is closed, the drive part 28D is added and the electromagnetic open / close valve 28 will be in a valve open state.

When the open / close switch 28 is opened, the driving portion 28D is released, and the electromagnetic opening and closing valve 28 is in a valve closing state.

The drive unit 30D of the electromagnetic open / close valve 30 is connected in series with the on / off switch 32 and is connected to the power supply lines 26 and 26.

The on / off switch 32 is closed while the current detector 18 detects the main current (plasma current).

Therefore, the drive part 30D of the electromagnetic opening and closing valve 30 is also added to the period in which the plasma current flows, and the electromagnetic opening and closing valve 30 is also in the valve opening state for this period.

The drive parts 28D, 30D, and the opening / closing switch 32 constitute a flow control means.

In this plasma arc cutting machine, as shown in Fig. 2 (a), when the on / off switch 24 is closed, it is energized to the relay drive unit 4D and the drive unit 28D of the solenoid valve.

The energization of the solenoid valve 28D causes the solenoid valve 28 to be in the valve open state, and as shown in Fig. 2C, the first flow rate (about 1 / of the flow rate required for generating a plasma arc satisfactorily). Compressed air is supplied between the nozzle 11 and the torch electrode 8.

As the relay drive unit 4D is energized, the relay contact 4 is closed, and the DC power supply circuit 2 is disposed between the torch electrode 8 and the nozzle 11, and the torch electrode 8 and the workpiece 10 are closed. Supply DC voltage in between.

At this point of time, the spacing between the torch electrode 8 and the nozzle 11 and the spacing between the torch electrode 8 and the workpiece 10 do not generate pilot arc or plasma arc.

As shown in Fig. 2 (b) in relation to the closure of the relay contact 4, the high frequency voltage generator 12 is operated, and a pilot arc is generated between the nozzle 11 and the torch electrode 8, and a pilot current is generated. Flows between them.

At this time, since the flow rate of the compressed air is smaller than the normal state as described above, the pilot arc easily occurs.

Therefore, the pilot current can be set to 10 A which is smaller than that shown in FIG.

In addition, it is not necessary to increase the power of the high frequency voltage generator 12 to easily generate the pilot arc, and it is not necessary to increase the voltage generated by the DC power supply circuit 2, and to increase the pilot current, the current limiting resistor 14 There is no need to decrease the resistance of).

When the torch electrode 8 approaches the workpiece 10 while the pilot arc is generated, the pilot arc is piloted to generate a plasma arc between the torch electrode 8 and the workpiece 10. As shown, the main current flows.

The flow of this main current is detected by the current detector 18 and the open / close switch 32 is closed.

As a result, the solenoid valve 30 is energized to the driving portion 30D of the solenoid valve, and as shown in FIG. Supplied from.

As shown in Fig. 2 (f), the solenoid valve 30 and the solenoid valve 28 supply compressed air at a flow rate of 270 liters / minute between the nozzle 11 and the torch electrode 11.

This flow rate is a flow rate necessary for generating a plasma arc satisfactorily.

At the same time, the plasma current detected by the current detector 18 is fed back to the DC power supply circuit 2.

This controls the inverter in the DC power supply circuit 2 so that, for example, a plasma current of 70 A is maintained.

In addition, the DC power supply circuit 2 stops the high frequency voltage generator 12 and the opening / closing switch 24 is opened by detecting that the main current flows by the current detector 18.

As a result, the generation of the pilot arc is stopped.

Thus, a plasma arc generate | occur | produces and when cutting | disconnection of the workpiece | work by this plasma arc is complete | release, the opening-closing switch 24 is opened.

As a result, the energization of the relay driver 4D and the solenoid valve driver 28D is interrupted, and the relay contact 4 is opened.

As a result, the DC power supply circuit 2 stops the generation of the DC voltage.

At the same time, the solenoid valve 28 is closed.

When the voltage supply from the DC power supply circuit 2 is stopped, the generation of the plasma arc is stopped, the on / off switch 32 is opened, the energization of the solenoid valve to the drive unit 30D is stopped, and the solenoid valve 30 is closed. A blockage condition occurs. Since both solenoid valves 28 and 30 are closed, the supply of compressed air is also stopped.

In the above-described embodiment, solenoid valves 28 and 30 for opening and closing the valve are used as the flow rate adjusting means.

This is because the control circuit of these solenoid valves becomes a simple structure only by turning ON / OFF the drive parts 28D and 30D.

However, when the opening / closing switch 24 is closed using one flow regulating valve, the flow rate adjusting valve is set to the first flow rate and the plasma arc detector 18 detects the plasma arc. You may comprise so that the flow volume of may adjust to the 2nd flow volume.

In the above embodiment, compressed air was used as the gas for plasma arc generation.

However, a gas such as inert gas or oxygen may be used instead of compressed air.

In this case, inert gas or oxygen can be used as a gas supply source in which these gases are accommodated in a cylinder instead of being supplied from a compressor.

In the above embodiment, the present invention is implemented in a plasma arc cutting machine, but the present invention may also be implemented in other plasma arc using equipment, for example, a plasma welding machine.

As described above, according to the invention as set forth in claim 1, when the pilot arc generating means is operated to generate the pilot arc, the flow rate control means supplies the gas to the gas flow rate adjusting means at a first flow rate between the nozzle and the torch electrode. Supply.

When the plasma arc occurs, the flow rate control means supplies the gas to the gas flow rate adjusting means at a second flow rate, which is a flow rate greater than the first flow rate, between the nozzle and the torch electrode.

Therefore, when generating the pilot arc, since the gas is supplied at the first flow rate, which is a small amount, it is possible to generate the pilot arc satisfactorily, and it is not necessary to make the pilot arc generating means or the DC power supply means a large capacity.

In addition, gas is not consumed in vain.

In addition, when the plasma arc is generated, the gas at the flow rate required for the generation is supplied, so that the plasma arc can be maintained satisfactorily.

According to the invention described in claim 2, at the time of the generation of the pilot arc, the gas is supplied between the nozzle and the torch electrode only by the first flow rate adjusting means.

At the time of the generation of the plasma arc, in addition to the first flow rate adjusting means, gas is also supplied from the second flow rate adjusting means between the nozzle and the torch electrode.

Moreover, the first and second flow rate adjusting means supplies gas at the first and second flow rates in a state where the bias signal or the detection signal of the plasma arc is being supplied, and stops the supply when the above-mentioned both signals are lost. Therefore, the flow rate control means needs only to be able to perform so-called ON / OFF control, and the structure of the flow rate adjustment means can be simplified.

According to the invention as set forth in claim 3, the plasma arc detection means is not only used for detecting the plasma arc but also used for the constant current control of the DC power supply means.

Therefore, it is not necessary to provide the plasma arc detection means only for switching the gas flow rate, and the circuit configuration can be simplified.

Claims (3)

DC power supply means 2 for supplying a DC voltage between the torch electrode 8 and the workpiece 10 when the bias signal is supplied, and the periphery of the torch electrode 8 when the bias signal is supplied. Means for generating a pilot arc between the nozzles 11 and the torch electrode 8 disposed at intervals between the nozzles 11, the source 20 of the plasma arc generating gas, and the nozzles 11 from the supply source 20; Gas flow rate adjusting means (28), (30) for supplying gas at a selected flow rate among the first flow rate and the second flow rate more than the flow rate between the torch electrodes (8); The plasma arc detection means 18 for generating a plasma arc detection signal when a plasma arc is generated between the torch electrode 8 and the workpiece 10, and the gas flow rate adjusting means 28 when the bias signal is generated. Plasma arc gum with the flow rate of the gas from As the signal is generated gas flow rate adjusting means 28, the flow control means (28D), a plasma arc using apparatus comprising a (30D) of the flow rate of gas from 30, the flow rate of the second. The method of claim 1, The gas flow rate adjusting means 28, 30 includes a first flow rate adjusting means 28 for supplying gas at a first flow rate when the bias signal is closed in the non-supply state and the bias signal is supplied; It is provided in parallel with the flow rate adjusting means 28 of 1, and is closed in the non-supply state of the plasma arc detection signal, and at the flow rate of the difference between a 1st flow volume and a 2nd flow volume in the supply state of a plasma arc detection signal. Plasma arc using device, characterized in that it comprises a second flow rate adjusting means 30 for supplying the gas The method of claim 1, The DC power supply means 2 is constant current controlled, and the plasma arc detection means 18 detects a current flowing through the torch electrode 8 and the workpiece 10, and this current is used as a control signal for constant current control. Plasma arc using equipment, characterized in that is also supplied