JPS6119339B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an arc welding machine equipped with an arc start detection device.

Conventionally, arc welding machines detect arc start and perform various controls based on this detection signal. Control is required, for example, in the following cases. (1) After arc start,
Performs self-holding of the torch switch circuit. (2) In the case of arc spot welding, the arc spot welding time is counted from the moment the arc starts.
(3) In the case of TIG welding, a high frequency voltage is applied at the start, but in DC TIG welding, the high frequency voltage is cut off after arc start, and in AC TIG welding, the high frequency voltage is attenuated after arc start. (4) In the case of consumable electrode arc welding, at the start, the electrode feeding speed is set to a low slowdown speed, and after the electrode contacts the base metal and welding current begins to flow, the feeding speed is switched to the feeding speed during welding. (5) In the case of automatic welding, start running the cart after starting the arc. The arc start detection signal is also used for special controls such as hot start and cold start. Conventionally, magnetic amplifiers, current transformers, diodes, relays, etc. were used to obtain this detection signal. A combination of these is used. However, such a configuration requires a separate power source to operate the relay, and the device itself is large, resulting in high cost.

On the other hand, in an arc welding machine, an auxiliary power supply circuit is connected in parallel with the main power supply circuit, and a part of the welding current is supplied from this auxiliary power supply circuit. For example, TIG welding requires a high no-load voltage in order to maintain a stable arc even when the arc starts and the arc length increases during welding. Since this voltage is about 3 to 4 times the arc voltage, making a welding machine with one power transformer would be uneconomical and large. For this reason, an auxiliary power supply circuit with a high no-load voltage is connected in parallel to the main power supply circuit with a low no-load voltage, and the main output current is supplied from the main power supply circuit, and the auxiliary power supply circuit stabilizes the arc at arc start and during welding. A system has been proposed that supplies voltage for this purpose. Furthermore, when output is controlled by phase control using a thyristor or the like in the main power supply circuit, when the output is adjusted to a low output, the output pulsates greatly and is likely to cause arc breakage. In order to prevent this, a portion of the welding flow is supplied from an auxiliary power supply circuit whose no-load voltage is higher than the arc voltage and whose short-circuit current is small, as described above. Additionally, an auxiliary power supply circuit may be used to switch the welding current during welding, and welding may be performed using both the main power supply circuit and the auxiliary power supply circuit, and crater filler treatment may be performed using only one of them after welding is complete. be. Furthermore, an auxiliary power supply circuit may be used to perform a hot start or cold start, and is particularly effective in AC arc welding machines that use a leakage transformer such as a moving iron type or a moving coil type. I understand.

As an arc start detection device, a device has been proposed in which a relay winding is connected in parallel with a current limiting resistor in this auxiliary power supply circuit and the relay is operated by the voltage generated in the resistor. However, this device is prone to breakage of the relay winding, poor connection, poor contact of the relay contacts, etc. When this happens, an arc occurs and even if current flows through the auxiliary power circuit, the relay does not operate and the arc starts. Since it cannot be detected, it cannot be said to be a highly reliable device. Additionally, even if current begins to flow in the auxiliary power circuit at arc start, since the relay winding has inductance, it takes time for the current in the relay winding to increase to the relay's operating current, resulting in a delay in arc start detection. There is also a drawback. This device is TIG
It can be used when the no-load voltage of the auxiliary power circuit is considerably higher than the arc voltage, such as in a welding machine, but if the no-load voltage of the auxiliary power circuit is slightly higher than the maximum arc voltage, the relay winding may be damaged by the arc voltage. The applied voltage changes widely, and when the voltage applied to the relay is low, the relay does not operate, and when the voltage applied to the relay is high, it burns out the relay winding, making it unusable.

Furthermore, devices are used that operate relays using the magnetic flux generated by the output current of the main power circuit, but the range of main output current is wide, especially TIG
In welding, the output current is adjusted over a wide range of 10 to 500 A, and malfunctions such as failure to operate at small currents and failure to return due to residual magnetic flux at large currents have become a problem.

The present invention was made for the purpose of solving the above-mentioned problems, and the present invention has been made for the purpose of solving the above-mentioned problems. The present invention provides an arc welding machine that detects arc start by operating a reed switch using magnetic flux.

FIG. 1 is an electrical connection diagram showing a basic embodiment of the present invention. Two output terminals 1a of the main power circuit 1,
1b is connected to the electrode 2 and the base material 3, respectively. One of the two output terminals 5a of the auxiliary power supply circuit 5
is connected to the base material 3, and the other 5b is connected to the electrode 2 through an inductance element 6 for current limiting. An arc 4 is generated between the electrode 2 and the base material 3 by the power supplied from the main power circuit 1 and the auxiliary power circuit 5. Reference numeral 7 designates a known reed switch whose contacts open and close in response to surrounding magnetic flux, and this reed switch is installed near the inductance element 6 so that the contact opens and closes using the magnetic flux generated from the inductance element 6. The reed switch 7 is shown in FIG. 1 as a normally open contact, which closes when magnetic flux is generated, that is, a normally open contact. The reed switch 7 can be installed by using the inductance element 6 as an air-core coil and inserting the reed switch 7 inside the coil, or by using the inductance element 6 as a coil with an iron core and placing the reed switch 7 near the end of the iron core. There are ways to do this. Further, when the output current of the auxiliary power supply circuit 5 is limited using the inductance of a leakage transformer, the reed switch 7 can be placed at a position where leakage flux of the leakage transformer is generated. Furthermore, when the output current of the auxiliary power supply circuit 5 is limited by a reactor, a reed switch may be arranged so as to be operated by the magnetic flux of the reactor.

If the output current of the auxiliary power supply circuit 5 is used as the magnetic flux for operating the reed switch 7 as described above, the situation where an arc start is not detected even though an arc is occurring will occur unless the reed switch 7 is malfunctioning. I don't get it. Since the reed switch 7 has very few failures as is well known, the detection of arc start according to the invention is extremely reliable. Furthermore, when current begins to flow through the inductance element 6, magnetic flux is generated from the inductance element 6 at the same time, and since reed switches generally operate at a high speed, arc start detection can be performed with a high response speed.

As mentioned above, in conventional devices that operate relays using the magnetic flux generated by the output current of the main power circuit, the range of the main current is wide, and
In TIG welding, the output current is adjusted over a wide range of 10 to 500A, and there was a problem that it would not work at small currents and would not return due to residual magnetic flux at large currents, but with the present invention, the current adjustment range is very narrow. Since the reed switch is operated by the magnetic flux generated by the output current of the auxiliary power supply circuit, the reed switch can be operated stably and reliably. Moreover, since the auxiliary output current is as small as several A to several + A, the inductance element can be made small.

The reed switch used in the present invention generally operates with an extremely low magnetic flux density, so it has a simpler structure and requires less driving power than a general electromagnetic relay that moves a movable iron core using an electromagnet, and the current flowing through the inductance element 6 is small. It works reliably in any case. In addition, it operates without problems even when the magnetic flux density is quite high, and unlike electromagnetic relays, it is not damaged by excessive current, so it is possible to reliably detect arc start even when the fluctuation range of the current flowing through the inductance element 6 is large. can.

Furthermore, compared to conventional arc start detection methods that combine magnetic amplification and relays, the conventional method requires a power source for the relay, but the present invention does not require this. The start detector is characterized by being relatively small and inexpensive.

FIG. 2 is an electrical connection diagram of an embodiment showing in detail the main power supply circuit 1 and the auxiliary power supply circuit 5 of the embodiment shown in FIG. This shows the case where current power is supplied between base materials. The main power circuit 1 has a first secondary winding 8a of a transformer 8 and two thyristors 9, 9', and both terminals of the first secondary winding 8a are connected to the thyristors 9, 9', respectively. The cathodes of the thyristors 9 and 9' are both connected to the electrode 2. The auxiliary power supply circuit 5 includes a second secondary winding 8b of the transformer 8, two thyristors 11, 11', and a resistor 12, and both terminals of the second secondary winding 8b are connected to the thyristors. 11 and 11'. The cathodes of the thyristors 11 and 11' are both connected to one terminal of a resistor 12, and an inductance element 6 is inserted between the other terminal of the resistor 12, that is, one of the output terminals of the auxiliary power supply circuit 5, and the electrode 2. has been done. Note that the reed switch 7 is arranged near the inductance element 6, as in the case of FIG. 1st
The middle tap of the secondary winding 8a and the second secondary winding 8
The middle taps of b are both connected to the base material 3,
Both terminals of the primary winding 8c of the transformer 8 are connected to an AC power source (not shown). Thyristor 9, 9',
Appropriate control signals are applied to 11 and 11', but a detailed explanation thereof will be omitted.

FIG. 3 shows the electrical connections of another specific embodiment of the present invention, in which the main power circuit 1 and the auxiliary power circuit 5 each consist of only a transformer, and both provide AC output between the electrode base materials. supply One input terminal of the transformer constituting the main power supply circuit 1 is connected to the first terminal 16a of a suitable AC power supply, and the other input terminal is connected to the second terminal 16a of the AC power supply via a switch 31.
connected to b. One input terminal of the transformer constituting the auxiliary power supply circuit 5 is connected to the first terminal 16a of the AC power supply, and the other terminal is connected to one AC side terminal of the bridge rectifier circuit 15. The other AC side terminal of the bridge rectifier circuit 15 is connected to the second terminal 16b of the AC power source via the switch 14. The two DC side terminals of the bridge rectifier circuit 15 are respectively connected to both terminals of an inductance element 6, and a reed switch 7 is arranged near this inductance element. Output terminals of the main power circuit 1 and the auxiliary power circuit 5 are connected to the electrode 2 and the base material 3, respectively. In the circuit of FIG. 3, if there is no rectifier 15, the direction of the magnetic flux of the inductance element 6 changes every half cycle, so the magnetic flux becomes zero every half cycle, and the reed switch 7 opens and closes each time. The rectifier 15 is provided to prevent such a situation from occurring, and is not necessary when the current flowing through the inductance element 6 is large.

Although the inductance element 6 is connected to the input side of the auxiliary power supply circuit 5 in the figure, it may be connected to the output side of the auxiliary power supply circuit 5.

In the case of the embodiment shown in FIG. 3, the excitation current of the transformer of the auxiliary power supply circuit 5 flows even during non-welding when the electrode 2 and the base metal 3 are in an open state. Furthermore, if the no-load voltage of the auxiliary power circuit 5 is higher than that of the main power circuit 1, the main power is supplied from the output side of the auxiliary power circuit 5 to the secondary winding of the transformer of the main power circuit 1 even when not welding. A current flows to excite the core of the transformer of circuit 1. Therefore, in the embodiment shown in FIG. 3, it is necessary to lower the operating sensitivity of the reed switch 7 to such an extent that the reed switch 7 does not operate with such a current.

In addition, when the auxiliary power supply circuit 5 is used for improving arc starting or stabilizing the arc, the switch 1
3 and 14 may be opened and closed at the same time. In addition, when performing crater filler treatment, welding is started by closing switches 13 and 14 at the same time, and when welding is complete, either one of switches 13 or 14 is opened first, and the other one that remains closed is It is sufficient to supply the crater filler current only from the circuit.

In any of the cases shown in FIGS. 1, 2, and 3, the coil of the inductance element 6 may be provided with a tap, or two coils, one for large current and one for small current, may be provided. By the way,
The inductance can also be changed depending on the output current value of the auxiliary power supply circuit 5, etc.

The present invention can be applied to various arc welding machines regardless of the welding method, and the detected arc start detection signal can be used for the aforementioned self-holding control, arc spot time control, high frequency voltage control, slowdown control, etc. It can be used for various controls.

As described above, the present invention has the advantage that an arc welding machine that operates reliably, has high reliability, and detects arc start with a fast response speed can be realized at low cost with a simple structure.

[Brief explanation of the drawing]

FIG. 1 is an electrical connection diagram schematically showing an example of the configuration of the present invention, FIG. 2 is an electrical connection diagram showing a specific embodiment of the invention, and FIG. 3 is another specific embodiment of the invention. It is an electrical connection diagram showing an example. 1...Main power supply circuit, 5...Auxiliary power supply circuit, 6...
...Inductance element, 7...Reed switch.

Claims (1)

[Claims] 1. In an arc welding machine having a main power supply circuit and an auxiliary power supply circuit connected in parallel to the power supply circuit and supplying a part of the welding current, an inductance element provided in the auxiliary power supply circuit, and the inductance element 1. An arc welding machine comprising a reed switch operated by magnetic flux generated from the reed switch, and detecting an arc start based on the operation of the reed switch.