JP3443176B2 - Arc processing equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an arc processing apparatus used for arc welding or cutting.

[0002]

2. Description of the Related Art FIG. 1 is a diagram showing an example of a conventional apparatus in the case of arc welding when a high frequency high voltage is used for starting an arc. In FIG. 1, 10 is a welding power source, 1 to 3 are primary input lines, and 4 are electrodes which are held by a welding torch (not shown). Reference numeral 5 is a work piece, that is, a work piece, 6 is an electrode side cable, 7 is a work piece side cable, 8 is a start switch, and 9 is a remote output regulator. DR1 in the welding power source 10 is a primary rectifier circuit, TR1 is an inverter circuit, T1
Is an inverter transformer, DR2 is a secondary rectifier circuit, LD1
Is a reactor, C1 is a high frequency bypass capacitor, HF
Is a high frequency high voltage generator, CC is a coupling coil, C
T1 is an output current detector, CL1 is an output control circuit, Tm1 is an electrode-side output terminal, and Tm2 is a workpiece-side output terminal. Further, R1 and R2 are resistors, E1 and E2 are DC power supplies, PC1 is a photocoupler, CN1 is a start switch outlet, and CN2 is a remote output adjuster outlet.

In FIG. 1, when the start switch 8 is pressed,
A current flows through the light emitting diode of the photocoupler PC1 to turn on the phototransistor, and a voltage substantially equal to the voltage of the DC power source E1 appears across the resistor R1. The voltage across the resistor R1 is guided to the output control circuit CL1 as a start signal. The output control circuit CL1 drives a gas supply circuit (not shown) by the input of the activation signal. The gas supply circuit emits a shielding gas between the electrode 4 and the work piece 5. The output control circuit CL1 drives the inverter circuit TR1 and the high frequency high voltage generator HF in anticipation of when the shield gas reaches the electrode 4. Inverter circuit TR1
Performs a switching operation at a frequency of several tens of KHz, induces a voltage required for a welding arc on the secondary side of the inverter transformer T1, and is rectified by the secondary rectifier circuit DR2, so that the no-load voltage is the secondary winding of the coupling coil CC. It appears through the wire to the electrode-side output terminal Tm1 and the workpiece-side output terminal Tm2, and is applied between the electrode 4 and the workpiece 5. The high frequency generator HF applies a high frequency high voltage to the primary coil of the coupling coil CC, and the high frequency high voltage induced in the secondary coil is the output terminal Tm1 on the electrode side, the electrode side cable 6, the high frequency bypass capacitor C1, and the workpiece. It is applied between the electrode 4 and the workpiece 5 via the side output terminal Tm2. At this time, the electrode 4 and the workpiece 5
Spark discharge occurs when the distance between the two is short. Following this spark discharge, a welding arc is induced between the electrode 4 and the workpiece 5.

Further, without using a high frequency high voltage, an auxiliary power supply for starting an arc is used to bring the electrode 4 into contact with the work 5 to be released, and then a small arc is once generated by the auxiliary power supply, and then welding is performed. There is one that starts the arc by shifting to the arc.

FIG. 2 is a connection diagram showing an example of a conventional apparatus of a system of starting an arc by an auxiliary power source. In the figure,
Reference numeral 11 is an auxiliary power supply for starting the arc. In the auxiliary power supply 11 for arc starting, T2 is an auxiliary transformer, DR3 is a rectifier circuit, R3 is a resistor, and SW1 is a switch. S
D is a short-circuit detector, AN1 is an AND gate, CL2 is an output control circuit, and CT2 is a current detector, which detects the output current of the auxiliary power supply 11 for starting an arc. In the figure, other parts have the same reference numerals as those of FIG. 1 and the description thereof will be omitted. The output voltage of the rectifier circuit DR3 is 2
The auxiliary transformer T2 is selected so as to be slightly higher than the no-load voltage on the side of the next rectifier circuit DR2, for example, about 100V.
The output of the auxiliary power supply 11 for starting the arc is the electrode side output terminal T
It is connected between m1 and the object to be welded side output terminal Tm2.
The short circuit detector SD outputs a HIGH level signal when a short circuit or an arc occurs between the electrode 4 and the workpiece 5.

At the start of welding in FIG. 2, an operator pushes the start switch 8 with the electrode 4 lightly contacting the workpiece 5. The short circuit detector SD receives the start signal from the start switch 8 and starts the detection operation. Short circuit detector SD
When the short circuit between the electrode 4 and the workpiece 5 is detected, the HI
Send a GH level signal to the AND gate AN1. The AND gate AN1 receives the respective HIGH level signals from the activation switch 8 and the short circuit detector SD and sends the activation signal to the output control circuit CL2. The output control circuit CL2 receives the activation signal from the AND gate AN1 and closes the switch SW1. As a result, the output of the auxiliary power supply 11 is supplied to the electrode 4, and a small short-circuit current limited by the resistor R3 flows through the electrode 4 and the object to be welded 5. In this state, when the worker separates the electrode 4 from the work piece 5, an arc is generated between the electrode 4 and the work piece 5. At this time, the current is resistor R
Since it is limited by 3, the arc is limited to a small one. Thus, when the arc current is small, the arc voltage becomes high, so the output voltage of the secondary circuit of the auxiliary transformer T2 is set slightly higher than the no-load voltage on the secondary rectifier circuit DR2 side to stabilize a small arc. I want to leave it. The current of this small arc is detected by the current detector CT2, and the detection signal is sent to the output control circuit CL2.
Upon receiving the detection signal, the output control circuit CL2 causes the main power source 10
The inverter circuit TR1 of is started. As a result, main power is supplied from the inverter circuit TR1, the secondary rectification circuit DR2, and the DC reactor LD1 to grow into an arc required for welding, that is, a welding arc.

[0007]

In the conventional device for starting the arc by using the high frequency high voltage as described above, it is necessary to prepare a large and expensive high frequency generator, and the high frequency generated at the time of starting the arc. High voltage leaks to the adjacent cable or ground, or the cable or electrode serves as an antenna to radiate high-frequency electromagnetic waves into the air. As a result, it often caused a noise disturbance not only to the own device but also to other nearby devices, causing a malfunction.

Further, as shown in FIG. 2, the method of contacting the electrode and the workpiece with an auxiliary power source and then separating the electrodes and starting the arc, while avoiding the above-mentioned problem of high frequency noise, Since the output circuit is usually provided with a reactor, it takes time to increase from a small current of the auxiliary power supply to a large current for machining when the short circuit is resolved, and during this time, the electrode and the work piece If the distance is too large, the arc may not grow sufficiently and may break, resulting in failure to start the arc.

[0009]

SUMMARY OF THE INVENTION In order to solve the problems of the above conventional apparatus, the present invention short-circuits the electrode to the workpiece prior to the arc starting without using a high frequency high voltage and detects this short circuit. To activate the auxiliary power supply and the main power supply,
And while the short-circuit detection signal is present, the main power supply is placed in the short-circuit state via the reactor to force a current to flow through the reactor, and when the electrodes are separated, the short-circuit detection signal disappears to release this short-circuit portion. The current flowing in the reactor is taken over by the processing part to the processing part, and the transition from the small arc by the auxiliary power supply to the large arc for processing is improved.

[0010]

The present invention will be described below with reference to the illustrated embodiments.

FIG. 3 shows an embodiment of the arc welding apparatus of the present invention. In FIG. 3, T3 is an inverter transformer and D
R3 is a rectifier, DR4 is a reverse blocking diode, TR2 is a transistor, and CL3 is an output control circuit. The output control circuit CL3 also controls the transistor TR2 and the switch SW1. The transistor TR2 forms a short circuit. In the figure, other parts are attached with the same reference numerals to the parts or assemblies having the same functions as those of the conventional device shown in FIG. 1 or 2, and the description thereof will be omitted.

The inverter transformer T3 is a rectifier DR2.
It has a secondary winding separate from the side. The output of the rectifier DR3 is connected between the electrode side output terminal Tm1 and the workpiece side output terminal Tm2 via a series circuit of a resistor R3 and a switch SW1.

FIG. 4 shows an embodiment of the short circuit detector SD used in the embodiment of FIG. In the figure, E3 to E
5 is a DC power supply, R31 to R34 are resistors, and PC10
Is a photocoupler, DR6 is a diode, and TR6 is a transistor. The output voltage of the DC power source E4 is set so that the following operation can be obtained. That is, when the terminals to CN1 are short-circuited and the terminals to Tm1 and Tm2 are short-circuited, a current flows through the light emitting diode of the photocoupler PC10, the phototransistor is turned on, and the resistor R31 is turned on. The terminal voltage becomes HIGH level. Even if the terminals to CN1 are short-circuited, the resistor R3 is provided if the terminals to Tm1 and Tm2 are open or the normal arc voltage is applied.
The terminal voltage of 1 becomes LOW level. When the terminals to CN1 are open, the terminal voltage of the resistor R31 is LOW level. DR6 short-circuits the reverse voltage so that the terminal voltage of the resistor R31 is at the LOW level when the reverse voltage is applied.

In FIG. 3, at the start of welding, an operator short-circuits the electrode 4 to the workpiece 5 and presses the start switch 8.
When the start switch 8 is pressed, the light emitting diode of the photocoupler PC1 emits light, the phototransistor is turned on, and a HIGH level signal is generated in the resistor R1. Resistor R1
Signal of HIGH level enters the input terminal 2 of the AND gate AN1. On the other hand, when the electrode 4 and the workpiece 5 come into contact with each other, the output signal of the short-circuit detector SD becomes HIGH level and the output signal of the AND gate AN1 becomes HIGH level. In response to the HIGH level output signal of the AND gate AN1, the output control circuit CL3 causes the transistor TR2,
A start signal is sent to each of the switch SW1 and the inverter circuit TR1. As a result, the switch SW1 is closed, and the inverter circuit TR1 starts outputting. Further, this output is short-circuited via the reactor LD1 because the transistor TR2 is conducted by the output from the output control circuit CL3.

At this time, since the reverse blocking diode DR4 is provided between the reactor LD1 and the electrode side output terminal Tm1, no current flows from the short circuit detection circuit SD to the transistor TR2 regardless of the conduction of the transistor TR2. Similarly, the output current of the rectifier DR3 is also prevented from flowing to the transistor TR2 by the reverse blocking diode DR4 and is supplied only to the electrode 4 and the workpiece 5. Further, a current flows from the secondary rectifier DR2 to the series connection circuit of the reactor LD1 and the transistor TR2, and this current is the output control circuit C.
Controlled by L3. Next, when the short circuit between the electrode 4 and the workpiece 5 is opened while the start switch 8 is still pressed, a small arc is generated between the electrode 4 and the workpiece 5 due to the output current of the rectifier circuit DR3. To do. Further, the output signal of the short-circuit detector SD becomes LOW level, the output signal of the AND gate AN1 becomes LOW level, and the output control circuit CL3 cuts off the transistor TR2. As a result, the current flowing through the reactor LD1 immediately flows through the electrode 4 and the workpiece 5, and the welding current rises rapidly. As a result, the transition to the welding arc is favorably performed.

FIG. 5 shows another embodiment of the arc welding of the present invention. C2 and C3 are bypass capacitors, LD2
(1/2) and LD2 (2/2) are reactors, and GD is ground potential. In the figure, other than that, parts or assemblies having the same functions as those in FIG.
The reactor LD2 has two windings LD2 insulated from each other.
(1/2) and LD2 (2/2) consist of two reactors wound on one iron core and magnetically coupled, and the current of each winding magnetizes the iron core in the same direction. Reactor LD2
Each of the windings is between the negative output terminal of the secondary rectifier DR2 and the electrode side output terminal Tm1 via the reverse blocking diode DR4, and between the positive output terminal of the secondary rectifier DR2 and the work piece side output terminal Tm2. Connected. Bypass capacitors C2 and C
The series circuit with 3 is connected between the output terminals of the secondary rectifier DR2, and the connection point between the bypass capacitors C2 and C3 is connected to the ground potential GD, that is, grounded.

In FIG. 5, the number of turns of each winding of the reactor LD2 is half that of the reactor LD1 of FIG.
And When the current flowing in the reactor LD2 at the time of starting the arc shifts to the welded portion, a small current drop occurs instead of immediately changing from the small current flowing from the auxiliary power source to the large current flowing in the transistor TR2. However, for this reason, the reactor generates a voltage in a direction in which this current change is hindered. This voltage contains a lot of high frequency components, and it cannot be said that there is no noise. However, as shown in the figure, the secondary rectifier circuit D of the reactor LD2
When the R2 side is grounded via the bypass capacitors C2 and C3, the high frequency components of the electrode 4 side and the workpiece 5 side with respect to the ground have the same magnitude and opposite phase. Therefore, the electrode 4
The high-frequency components leaking from the side and the workpiece 5 side to the ground cancel each other out, so that the leakage of noise to the ground is extremely reduced.

In each of the above embodiments, the main circuit of the welding power source has been described using the inverter control type. However, in implementing the present invention, the main circuit system of the welding power source is not limited to the inverter control type. That is, thyristor control or DC chopper control on the secondary side of the transformer may be used. Further, as the auxiliary power source, a separately installed transformer may be used other than the above-mentioned embodiment in which electric power is obtained from the transformer of the main power source. Further, the output form of the main power source may be the direct current output or the alternating current output described above, or may be the one including a component that periodically pulsates in each waveform of direct current or alternating current or the pulse waveform.

Further, although each of the above-described embodiments has been described only in the case where the present invention is applied to arc welding, the present invention can be applied to any processing that uses arc discharge, for example, Besides welding, it can be applied to arc cutting, arc spraying, arc heating, arc melting, etc.

It can also be applied to plasma arc welding and plasma arc cutting without using a pilot arc.

[0021]

As described above, according to the present invention, without using the high frequency generated by the high frequency generator, the electrode and the work piece are brought into contact with each other in advance to allow a small current to flow from the auxiliary power source and the main circuit is provided. Since a current is forced to flow in the reactor that is being operated, when the electrode 4 is separated from the work 5 to be welded, the output current rises due to the electromotive force of this reactor when the small arc by the auxiliary power source shifts to the main arc. Since it becomes sudden, the failure to start the arc is almost eliminated.

[Brief description of drawings]

FIG. 1 is a connection diagram showing an example of a conventional device for starting an arc by a high frequency high voltage circuit.

FIG. 2 is a connection diagram showing an example of a conventional device in which an arc is started by an auxiliary power supply with a small current.

FIG. 3 is a connection diagram showing an embodiment when the present invention is applied to an arc welding device.

FIG. 4 is a line connection diagram showing an example of a short-circuit detector used in the embodiment of FIG.

FIG. 5 is a connection diagram showing another embodiment when the present invention is applied to an arc welding apparatus.

[Explanation of symbols]

4 electrodes 5 Objects to be welded 6 Electrode side cable 7 Cable to be welded 8 Start switch 9 Remote output regulator 10 Welding power source 11 Auxiliary power supply for starting arc SD short circuit detector AN1 AND Gate E1 to E5 DC power supply PC1, PC10 Photo coupler DR1 primary rectifier circuit DR2 secondary rectifier circuit DR3 rectifier DR4 reverse blocking diode DR6 diode TR1 inverter circuit TR2 transistor TR6 transistor T1, T3 inverter transformer T2 auxiliary transformer SW1 switch CT1 output current detector CL1 to CL3 output control circuit LD1 reactor LD2 (1/2), LD2 (2/2) reactor Tm1 electrode side output terminal Tm2 Workpiece side output terminal R1 to R3 resistors R31 to R34 resistors C2, C3 bypass capacitors CN1 start switch outlet CN2 Remote output adjuster outlet GD ground potential

Claims (2)

(57) [Claims] Claim: What is claimed is: 1. An arc welding apparatus of a type in which an electric power is turned on in a state where an electrode is in contact with a work piece in advance, and then an electrode is separated from the work piece to generate an arc, which has a reactor in an output circuit. A main power supply for supplying power for the main arc, a short circuit for short-circuiting the output of the main power supply via the reactor, an auxiliary power supply for supplying a small current for arc starting between the output terminals, and the short circuit And a reverse blocking diode provided between the output terminal, a short-circuit detector that detects a short circuit between the electrode and the workpiece provided between the output terminals, and the short-circuit detector detects a short circuit Then, the auxiliary power source and the main power source are started, and the short-circuit detector detects the opening between the electrode and the workpiece from when the short-circuit detector detects a short circuit between the electrode and the workpiece. Arc welding apparatus having to force the output control circuit to flow a current between the short circuit to the reactor was started in. 2. The reactor comprises two reactor windings provided at both ends of an output circuit and one core wound around each reactor winding and excited in the same direction by a current flowing through each winding. The arc processing apparatus according to claim 1, comprising: