JPH073871U - Plasma arc processing equipment - Google Patents

Abstract

(57) [Abstract] [Purpose] The present invention relates to improvement of plasma arc processing equipment. [Configuration] In a plasma arc processing apparatus, a torch has a protective cup attached to a position surrounding a tip electrode, two or more protective cup attachment detection electrodes provided on the body side of the torch, and a torch body provided to the protective cup. A short-circuit electrode that short-circuits the attachment detection electrode when attached to the
A series circuit including a mounting detection electrode, a short-circuit electrode, a power supply, a light emitting diode, and a contact for a start command switch,
The feature is that the output light of the light emitting diode is guided to the control circuit of the processing power source by the optical fiber cable.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a plasma arc processing apparatus for performing welding, cutting, spraying, etc. by a plasma arc, and when igniting a pilot arc between a tip electrode and a main electrode, a pilot arc is applied between the electrodes. The present invention relates to an improvement in a device that applies a voltage for arc and superimposes a high frequency high voltage on it to generate a spark discharge between both electrodes, thereby inducing a pilot arc.

[0002]

[Prior 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, processing is generally configured as shown in a partial sectional view and a connection diagram in FIG. Has been done. In the figure, reference numeral 1 denotes a torch main body, a main electrode 12 held inside by a chuck 11, a nozzle-shaped tip electrode 13 mounted in an insulating state at a position surrounding the main electrode, a tip electrode protection cup 14 and a starter. It includes a command push button switch 15. Although not shown, the working gas for plasma generation is supplied between the main electrode 12 and the tip electrode 13 and is ejected to the outside from an orifice portion provided at the tip of the tip electrode 13. Reference numeral 2 is a processing power supply device, which is an AC / DC converter that converts an AC power supply into a DC output having characteristics suitable for plasma processing, an output control unit 21 that controls start / stop, supply of working gas, etc. Device 22, current limiting element 23, high frequency generating means 24, coupling coil 25 for superimposing the output of high frequency generating means 24 on the pilot circuit reaching chip electrode 13, high frequency bypass capacitors 26a to 26c and high frequency blocking choke. It is composed of coils 27a and 27b. In addition, 3 is a workpiece.

The positive output of the output control unit 21 is directly connected to the work piece 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 control unit 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 activation command input terminal of the processing power supply device 2. In order to improve workability, each of these connection cables is integrated with the working gas supply hose (not shown) except the power cable (ground cable) that connects the workpiece 3 and the positive output terminal. They are usually bundled together and in close contact with each other to form a composite cable with 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 generator 24 generates a high frequency high voltage. Further, the switch 22 is closed by a start command from the push button switch 15, so that the positive output of the output control unit 21 reaches the tip 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 output from the high frequency generating means 24 is superimposed on this output voltage by the coupling coil, the disconnection between the tip electrode 13 and the main electrode 12 is destroyed by this. Spark discharge is generated, and this spark discharge triggers arc discharge (pilot arc).

The current of the pilot arc is limited to a relatively small value by the current limiting element 23. Some high-frequency generators are designed to stop the output by the generation of this pilot arc, but since the pilot arc is easily blown out by the working gas flowing at high speed, the main arc is usually It is often configured to operate continuously until it occurs and processing begins.

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 electrode 12 and the work piece 3 are mainly contacted with each other. An arc occurs. 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 is extinguished.

Here, the high frequency voltage supplied for starting and maintaining the pilot arc may cause an accident such as an electronic circuit inside the processing power supply device 2 malfunctioning due to induction or a component damage due to overvoltage mixing. Because of this, the capacitors 26a and 26b are connected inside the coupling 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 including the choke coils 27a and 27b and the capacitor 26c.

[0010]

[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 distributed capacitance is connected in parallel between the connection cable to the main electrode 12 and the tip electrode 13 on which the high-frequency voltage is superimposed and the control cable arranged in close contact, and each of these control cables is connected. Distribution capacity also exists between the cable and the earth. The high frequency voltage is bypassed and attenuated by these distributed capacitances. Furthermore, the insulation resistance in the torch is low, and the longer the time of use, the lower the insulation resistance between the tip electrode or main electrode and the pushbutton switch that is the control component.

In addition, an electrode for detection is provided between the cup 14 and the body of the torch 1 in order to detect that the protection cup 14 is securely attached to the tip electrode 13, and In a torch that detects a short circuit due to mounting and uses it as a work enable signal, it is extremely difficult and insufficient because the insulation between this tip electrode and the cup mounting detection electrode is a narrow place. Insulation resistance cannot be obtained. As a result, the high frequency voltage applied to the chip electrode may leak from these insulating parts 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 machining 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 cable and the ground, resulting in a large attenuation.

These attenuations become larger as the cable becomes longer, 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, the pilot arc It may disable ignition. Furthermore, a high-frequency voltage of several MHz is induced in an unnecessary cable, and this acts as an antenna, increasing the emission of radio waves into the air and causing radio interference.

[0013]

[Means for Solving the Problems]

 The present invention connects a chip electrode protective cup attachment detection electrode on the processing torch side, a power supply and a contact of a start switch in series to connect to a light emitting diode, and the output light of the light emitting diode is controlled by an optical fiber cable to control the processing power supply. The problem of the above-mentioned conventional device is solved by adopting a structure in which a photoelectric conversion circuit for guiding the input light into an electric signal is provided in the control circuit while being guided to the circuit.

[0014]

【Example】

 FIG. 1 shows an embodiment of the present invention. In the figure, the processing power supply 2 is provided with a phototransistor 29 in place of the choke coils 27a and 27b and the capacitor 26c, and the cable connecting the processing torch 1 and the processing power supply 2 is provided with an optical fiber 4b. There is.

Further, in the torch body 1, cup attachment detection electrodes 17a and 17b are provided on the torch body side, and a ring-shaped electrode 18 for short-circuiting the detection electrodes 17a and 17b at the time of attachment is provided on the cup 14 side. Has been. The detection electrodes 17a and 17b are connected in series with the contacts of the push button switch 15, the DC power source E, the resistor R and the light emitting diode 28, and only when the cup 14 is completely attached to the torch body. 15 is configured to be effective. Further, C1 and C2 are capacitors, respectively, which protect the light emitting diode 28 and the power supply circuit from being destroyed when high frequency high voltage applied between the chip electrode 13 and the main electrode 12 is induced or mixed in the light emitting diode circuit. It is a bypass capacitor for protection. Further, an optical fiber cable 4b is connected between the phototransistor 29 and the light emitting diode 28 of the processing torch 1 which is a start / stop command for the output control unit 21 of the processing power supply device 2.

The output optical signal of the light emitting diode 28 passes through the fiber 4b and is applied to the phototransistor 29 from the optical fiber connector 31b and the optical fiber 30b.

In the device shown in the figure, when the push-button switch 15 is pushed while the protection cup 14 is provided and the detection electrodes 17a and 17b are in conduction, the light emitting diode 28 emits light, and this output light is emitted. It is transmitted to the phototransistor 29 by the fiber 4b to make it conductive, and the output control circuit 21 is activated. When the push button switch 15 is released, the output light of the light emitting diode 28 disappears, the phototransistor 29 is also cut off, and the output control circuit 21 also stops operating.

[0018]

[Effect of device]

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

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a conventional device.

[Explanation of symbols]

 1 Torch Main Body 2 Processing Power Supply Device 4b Optical Fiber 12 Main Electrode 13 Chip Electrode 14 Protective Cup 15 Start Command Pushbutton Switch 17a, 17b, 18 Cup Mounting Detection Electrode 21 Output Control Section 24 High Frequency Generation Means 25 Coupling Coil 28 Photodiode 29 Phototransistor E Power supply

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 of a machining torch by superposing a high-frequency voltage on a pilot arc power supply circuit. The torch has a protection cup attached to a position surrounding the tip electrode, two or more protection cup attachment detection electrodes provided on the body side of the processing torch, and a protection cup provided on the protection cup and attached to the torch body. A short-circuit electrode for short-circuiting the attachment detection electrode when a short circuit occurs, and a series circuit composed of the attachment detection electrode, the short-circuit electrode, a power supply, a light-emitting diode and a contact of a start command switch, and the output of the light-emitting diode. The light is guided to the control circuit of the processing power source by an optical fiber cable, and the optical fiber cable is connected to the control circuit. A plasma arc processing device equipped with a photoelectric conversion circuit that converts the output light from these to an electrical signal.