JPH0622550Y2 - Plasma arc processing equipment - Google Patents

Description

[Detailed Description of the Invention] [Industrial application] The present invention relates to a plasma arc processing apparatus for performing welding, cutting, spraying, etc. by a plasma arc, in which a pilot is provided between a chip electrode and a main electrode. When the arc was ignited, a voltage for pilot arc was applied between both electrodes, and a high frequency high voltage was superposed on this to generate a spark discharge between both electrodes, thereby inducing a pilot arc. It relates to an improvement of the device.

[Conventional technology]

2. Description of the Related Art In a plasma arc processing apparatus of the type in which a plasma arc is generated between a work piece and a main electrode with the help of a pilot arc to perform processing, generally, a partial sectional view and a connection diagram are shown in FIG. Is configured. In the figure, reference numeral 1 is a torch main body, a main electrode 12 held inside by a chuck 11, a nozzle-shaped chip electrode 13 mounted in an insulating state at a position surrounding the main electrode, a chip electrode protection cup 14 and a starter. Command push button switch 15
Is included. Although not shown, the working gas for plasma generation is supplied between the main electrode 12 and the chip electrode 13 and is ejected to the outside from the orifice portion provided at the tip of the chip electrode 13. Reference numeral 2 is a processing power supply device, which converts an AC power supply into a DC output having characteristics suitable for plasma processing.
AC / DC converter, output control unit 21 for controlling start / stop, supply of working gas, switch 22, current limiting element 23,
High frequency generating means 24, a coupling coil 25 for superposing the output of the high frequency generating means 24 on a pilot circuit reaching the chip electrode 13, and a high frequency bypass capacitor 26.
a to 26c and high-frequency blocking chiyoke coil 27
It is composed of a and 27b. In addition, 3 is a workpiece.

The positive output of the output control unit 21 is directly connected to the workpiece 3 and is also connected to the chip electrode 13 through the switch 22, the current limiting element 23 and the coupling coil 25. The negative output of the output controller 21 is directly connected to the main electrode 12 of the torch 1. Further, the push button switch 15 of the torch 1 is connected to the start command input terminal of the machining power supply device 2. In order to improve the workability, each of these connection cables is integrated with the working gas supply hose (not shown) except for the power cable (ground cable) that connects the workpiece 3 and the positive output terminal. Usually, they are bundled and closely adhered to each other to produce a composite cable having a length of several meters to several tens of meters.

In the conventional apparatus of FIG. 2, when the push button switch 15 of the torch 1 is pressed, working gas is supplied and the output control section 21 outputs a predetermined output voltage between the positive and negative terminals, and the high frequency generating means. 24 generates a high frequency high voltage. Further, since the switch 22 is closed by a start command from the push button switch 15, the positive output of the output control unit 21 reaches the chip electrode 13 of the torch 1 via the switch 22, the current limiting element 23, and the coupling coil 25. Since the high frequency high voltage which is the output of the high frequency generating means 24 is superposed on this output voltage by the coupling coil, the insulation between the chip electrode 13 and the main electrode 12 is broken by this and the spark is generated. Electric discharge occurs, and this spark discharge serves as a trigger to induce arc discharge (pilot arc). The current of the pilot arc is limited to a relatively small value by the current limiting element 23. The high-frequency generating means may be configured to stop its output due to the generation of this pilot arc, but since the pilot arc is likely to be blown out by the working gas flowing at high speed, it is usually Is often configured to operate continuously until the main arc occurs and machining is initiated. When the torch 1 is brought close to the work piece 3 in this state, when the ionized portion of the working gas by the pilot arc comes into contact with the work piece, the main arc is generated between the main electrode 12 and the work piece 3. Occur. When the generation of this main arc is detected, the high frequency generating means 24 stops its output, and the switch 22 is opened, so that the pilot arc disappears. The high-frequency voltage supplied for starting and maintaining the pilot arc causes malfunction of the electronic circuit inside the machining power supply device 2 due to induction or causes accidents such as damage of parts due to mixing of overvoltage. Capacitors 26a and 26b are connected inside the ring coil 25 to bypass the high frequency voltage. Further, the high frequency voltage induced in the signal cable from the start push button switch is also prevented from entering from the outside by pushing in the low pass filter composed of the chike yoke coils 27a and 27b and the capacitor 26c.

[Problems to be solved by the device]

In the above conventional device, the high frequency voltage can be prevented from entering the processing power supply device, but the high frequency voltage cannot be prevented from leaking. That is, the main electrode 12 on which the high frequency voltage is superimposed
Further, the distributed capacitance is connected in parallel between the connection cable to the chip electrode 13 and the control cable arranged in close contact, and the distributed capacitance also exists between these control cables and the ground. . The high frequency voltage is bypassed and attenuated by these distributed capacitances. Furthermore, the insulation resistance in the torch is low, and the insulation resistance between the chip electrode or main electrode and the push button switch, which is a control component, becomes low as the usage time increases. Therefore, the high frequency voltage applied to the chip electrode may leak from these insulating portions and flow into the signal line. If this happens, the high frequency voltage will be transmitted through a long cable to the terminals of the processing power supply. For this reason, the high-frequency voltage is applied to a plurality of long cables and is bypassed by the distributed capacitance between the ground of the power supply cable and
It will be greatly attenuated.

The amount of attenuation increases as the cable length increases, and the voltage applied between the tip electrode and the main electrode in the torch decreases due to this, weakening the spark discharge and, in extreme cases, igniting the pilot arc. It can be disabled. Furthermore, a high-frequency voltage of several MHz is induced in an unnecessary cable, and this acts as an antenna to increase the emission of radio waves into the air and become a source of radio interference.

[Means for Solving the Problems]

The present invention provides a photoelectric conversion circuit in at least one of a control circuit for a processing torch or a processing power supply, and connects the processing torch and the control circuit with an optical fiber to solve the problems of the conventional device. It has been resolved.

[Action]

Since the signal is transmitted and received between the processing torch and the control circuit of the processing power supply not by the conductive cable but by the optical fiber, the high frequency voltage does not leak even if the cable becomes long, and the power supply The high frequency voltage from the circuit is effectively transmitted to the processing torch.

〔Example〕

FIG. 1 shows an embodiment of the present invention. In the figure, the processing power source 2 is provided with a light emitting diode 28 and a phototransistor 29 in place of the chain yoke coils 27a and 27b and the capacitor 26c, and the cable connecting the processing torch 1 and the processing power source 2 is provided with the optical fiber 4a. , 4b
Is provided. The output light of the light emitting diode 28 is an optical fiber 4a in a cable connected from the optical fiber connector 31a to the processing torch 1 by the optical fiber 30a.
Be derived to. Also, from the processing torch 1 to the optical fiber 4b
The optical signal returned through the optical fiber connector is the optical fiber connector 31b.
Then, the light is irradiated onto the phototransistor 29 through the optical fiber 30b. The output signal of the phototransistor 29 is connected to the output control section 21 and becomes the same activation signal as the ON / OFF of the pushbutton switch 15 in the conventional apparatus of FIG. Here, the light emitting diode 28 is driven by the output control unit 21, but is driven by a pulse current of a specific frequency in order to prevent malfunction due to external light, and a drive pulse is output in the output signal processing circuit of the phototransistor 29. It is configured to detect in synchronization with.

In the processing torch 1, instead of the electric push-button switch, the end faces of both optical fibers are arranged at a position where the output light of the optical fiber 4a is projected onto the optical fiber 4b. The optical fiber 4a is located between the end faces of both optical fibers.
Operation rod 1 for blocking and switching the output light from the
9a is provided, and the lever 19b allows the optical fiber 4a, 4b to enter and retract in the middle of both end surfaces thereof.

Other than the above, those having the same functions as those of the conventional apparatus shown in FIG. Next, the operation of the apparatus shown in FIG. 1 will be described.

In FIG. 1, the output light from the light emitting diode 28 reaches the end face in the torch 1 through the optical fiber 4a until the lever 19b is pushed, but is blocked by the operating rod 19a and reaches the incident end face of the optical fiber 4b. Does not reach. Therefore, the phototransistor 29 is in the OFF state, and the output control circuit 21 is configured not to generate any processing output at this time. (This is the same as the state in which the push button switch 15 in the device shown in FIG. 2 is not pressed.) Next, when the operator pushes the lever 19b, the operation rod 19a is pushed in and the output light of the optical fiber 4a is output. To reach the input end face of. As a result, the phototransistor 29 becomes conductive. As a result, the output control circuit 21 outputs a predetermined output voltage between the positive and negative output terminals, and the high frequency generating means 2
4 generates a high frequency high voltage. Since the opening / closing means 22 is also closed, the positive output of the output control unit 21 reaches the chip electrode 13 via the current control element 23 and the coupling coil 25. As a result, a spark discharge due to a high frequency and high voltage is generated between the chip electrode 13 and the main electrode 12 as in the prior art device, and the spark arc is ignited by the spark discharge. The operation after the occurrence of the pilot arc is the same as that of the conventional device shown in FIG. Next, the lever 19
When the button b is released, the operating rod 19a is returned to the optical fibers 4a, 4b.
Cut off the space. As a result, the output light of the light emitting diode 28 does not reach the phototransistor 29, whereby the start signal is released and the initial state is restored.

[Effect of device]

As described above, in the present invention, the processing torch and the control circuit of the processing power supply are connected by the optical fiber cable to exchange the control signal, so that the control signal can be transmitted or received in the middle of a long cable or for processing. Since the high frequency voltage does not leak to the control cable inside the torch, there is no attenuation of the high frequency and the ignition of the pilot arc does not fail. Further, since the high frequency does not leak to the signal line, the high frequency radiation from the signal line is reduced even if a long cable is used, and the radio interference can be greatly reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing an example of a conventional device. 1 ... Torch body, 2 ... Processing power supply device, 3 ... Workpiece,
4a, 4b ... Optical fiber, 12 ... Main electrode, 13 ... Chip electrode, 14 ... Protective cup, 15 ... Start command push button switch, 19a ... Operating rod, 19b ... Lever, 21 ... Output control section, 24 ... High frequency generation Means, 25 ... Coupling coil, 28 ... Light emitting diode, 29 ... Phototransistor

Claims (1)

[Scope of utility model registration request] 1. A plasma arc machining apparatus in which a pilot arc is ignited between a main electrode and a tip electrode by superimposing a high-frequency voltage on a pilot arc power supply circuit, and a control circuit for the machining power supply apparatus. In addition to providing a light emitting diode driven by a pulse current of a specific frequency predetermined in advance and a photoelectric conversion circuit for detecting the output light of the light emitting diode in synchronization with the frequency of the pulse current and converting it into an electric signal, A first optical fiber cable for guiding the output light of the light emitting diode to a processing torch, and a light input end is fixed so as to face the light output end of the first optical fiber cable, and the input light is converted into a photoelectric conversion circuit of the control circuit. A second optical fiber cable leading to the optical fiber, an optical output end of the first optical fiber cable of the processing torch, and Plasma arc processing apparatus provided the operating rod for transmitting and blocking light when required is provided between the light input end of the second optical fiber cable.