JPH01181974A - Arc welding power source - Google Patents

Abstract

PURPOSE:To prevent the occurrence of defective welding by providing a leak current detection circuit in parallel to a main power source circuit connected to an arc welding power source to detect a leak of a welding current before performing welding. CONSTITUTION:The main power source circuit 12 and an auxiliary power source circuit 13 are provided to the inside of the welding power source 1 and a power source 20, the leak current detection circuit 21, an amplifier circuit 22 and an input-output interface circuit 23 are provided to the inside of the auxiliary power source circuit 13. A switch 26 is closed to form the leak current detection mode and a welding torch is moved. When the leak current is generated due to damage, etc., of coatings of feeding cables 5 and 6, and conduit tubes 7 and 8, this is detected by the detection circuit 21 and this signal is amplified by the amplifier circuit 22 and inputted to the input-output interface circuit 23. Said signal is transferred to a robot controller 27 as a leak current detection signal 30 and an action to stop robot operation, etc., is carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a welding power source used for arc welding, and more particularly to an arc welding power source capable of detecting leakage of welding current.

[Conventional technology]

When arc welding a welded member using a consumable electrode such as a welding wire, power is normally supplied as shown in FIG. In the figure, power supply cables 5 and 6 are connected to both terminals of a welding power source 1, one end of which is connected to a power supply tip 4 provided on a member to be welded 2 and a welding torch 3, respectively. A conduit tube 7.8 is connected to one end of the welding torch 3 opposite to the end where the power supply tip 4 is provided, and a wire feed motor 9 is provided between these conduit tubes 7.8. ing.

The welding wire 10 passes through the conduit tubes 8 and 7, is fed by a wire feeding motor 9, and is projected to the outside from the power feeding tip 4 of the welding torch 3. On the other hand, welding current is supplied from the positive terminal of the welding power source 1 to the welding wire 10 through the power supply cable 6 and power supply tip 4, generates an arc between it and the workpiece 2, and passes through the power supply cable 5 to the welding power source 1. The current flows through a closed circuit returning to the negative terminal of the terminal.

A voltage necessary for arc generation and maintenance is applied between the welding wire 10 and the welded member 2.

Further, in the automatic arc welding equipment, the welding torch 3 is supported by an arm of a robot (not shown), and is moved by a carrier of the robot in accordance with the shape of the workpiece 2 to be welded.

In addition, as a device attached to this type of automatic arc welding equipment, as described in JP-A-55-114463, when the main contact does not open due to a failure of the main contact opening device, an indicator light is activated. An electric shock prevention device that lights up and activates a warning buzzer to prevent electric shock accidents, and Japanese Patent Application Laid-Open No. 57-4446
As described in Publication No. 9, there is a damage prevention device that detects when the torch approaches the workpiece to be welded abnormally and cuts off the power supply to prevent damage or damage to the torch due to series arc occurrence. It is publicly known.

[Problem to be solved by the invention]

In the conventional automatic arc welding equipment described above, the torch 3 moves as described above, so that the power supply cables 5, 6 and the conduit tube 7.8 connected to the torch 3 are bent. During this bending operation, they come into contact with the jig for holding the member to be welded 2, and if this bending and contact continues repeatedly, the insulating member covering the power supply cables 5, 6 and the conduit tube 7.8 is damaged.

When used with the coating damaged in this way, if the positive power supply cable 6 comes into contact with a part of the jig or the like to which the negative power supply cable 5 is connected during arc welding,
Current leaks from that part and the voltage supplied to the actual arcing point drops. As a result, there was a problem in that a normal arc could not be maintained, resulting in poor welding quality.

In order to prevent this quality defect from occurring, conventionally the power supply cables 5, 6 and the conduit tube 7.8 were periodically inspected visually and defective products were replaced. However, since it is a visual inspection, it is not possible to discover defects, and when the torch 3 is controlled in a complex manner using a robot, leaks occur only in specific areas, so the current may not be detected after welding quality defects occur. Very often I found out that it was leaking. As a result, the production line has to be stopped due to product repair or during operation, and furthermore, there have been problems such as fires caused by heat generated by the power supply cables 5 and 6, damage to unused welding wires, and other damages.

In addition, an ammeter or the like is usually installed in the closed circuit through which the welding current flows, but even if current leakage occurs, the path only changes; Since current appears to be flowing normally, current leakage cannot be detected using the ammeter or the like. In addition, the means described in the two bulletins mentioned above are:
None of these methods takes into account the detection of damage to the insulation coating of power cables and conduit tubes.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an arc welding power source that can detect leakage of welding current before welding and prevent the occurrence of welding defects.

[Means to solve the problem]

In order to achieve the above object, the present invention includes a main power supply circuit that applies a voltage necessary for resistance welding between a consumable electrode and a member to be welded, and a main power supply circuit that is connected in parallel to the main power supply circuit via a changeover switch. a sub-power supply circuit, a detection circuit provided in the sub-power supply circuit to detect leakage current generated in the main power supply circuit, an amplification circuit that amplifies the output of the detection circuit, and an output amplified by the amplification circuit. The arc welding power source is equipped with an input/output interface circuit that inputs the leakage current detection signal and outputs the leakage current detection signal to the outside.

[Effect]

According to the above configuration, the internal resistance of the closed circuit formed by the main power supply circuit is high to some extent, so if the power capacity of the sub power supply circuit is made small, even if voltage is applied from this sub power supply circuit, the internal resistance of the closed circuit formed by the main power supply circuit is high. Almost no current flows through. However, if current leaks due to damage to the insulation coating, the internal resistance becomes extremely small, and a corresponding current flows into the sub power supply circuit. This current is detected by the detection circuit, amplified by the amplifier circuit, and transferred to the input/output interface circuit, which then outputs a leak detection signal according to the specifications of the receiving side, such as displaying a lamp or activating an alarm buzzer. can do.

〔Example〕

EMBODIMENT OF THE INVENTION Hereinafter, one embodiment of the arc welding power source according to the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. In the figure, parts that are the same or equivalent to those of the conventional example shown in FIG. 3 are denoted by the same reference numerals, and explanations thereof will be omitted.

Welding torch 3 is supported by robot 11.

A main power supply circuit 2 and a sub power supply circuit 13 are provided in the welding power source 1, and a positive terminal 14 and a negative terminal 15 on the output side of the main power source circuit 12 are connected to the positive terminal 1 of the welding power source 1.
6 and the negative terminal 17 by wires 18 and 19, respectively.

The sub power supply circuit 13 includes a power supply 20 and a leak current detection circuit 2.
1. Amplification circuit 22 and input/output interface circuit 23
is provided. The wiring 24 connected to the negative electrode of the power source 20 is connected to the wiring 19, and the wiring 25 connected to the positive electrode is connected to the wiring 18 through the switch 26.
The detection circuit 2 is connected through the wiring 25.
1 or more are connected. Further, the detection circuit 21 is sequentially connected to an amplifier circuit 22 and an input/output interface circuit, and the input/output interface circuit 23 is connected to a robot control device 27 equipped with an external controller 5). Furthermore, this robot control device 27 has an indicator light 2 that displays leakage current.
8 is provided and b.

Next, the operation of this embodiment will be explained. First, when the switch 26 is closed to enter the leakage current detection mode, the power supply 20 in the sub power supply circuit 12 connects the power supply cable 18.6 and the power supply chip 4.
, welding wire 10, member to be welded 2, power supply cables 5, 1
A voltage is applied to a closed circuit composed of the main power supply circuit 9 and the main power supply circuit 12 . In this state, the welding torch 3 is moved along the movement trajectory b) previously taught in the control device 27 of the welding robot 11 that supports the welding torch 3.

If the switch 26 is closed at this time, an interlock is set so that the welding start command signal 29 from the robot control device 27 is invalidated (v).

During the above moving operation, if the coatings of the power supply cables 5, 6 and conduit tubes 7.8 are not damaged and arc welding is not performed, the internal resistance of the main power circuit 12 is generally about 5 OKΩ. Since the internal resistance of the closed circuit consisting of the welding power source 1, the power supply cables 5 and 6, and the welding torch 3 is about the same, the switch 26 is closed and the power source 2
0, even if a voltage is applied from the sub power supply circuit 13, almost no current flows through the closed circuit connected to the main power supply circuit 12. However, if the coatings of the power supply cables 5, 6 and conduit tubes 7.8 are damaged for some reason and a leakage current occurs, this leakage current is transmitted to the detection circuit 2.
1 and the signal detected by the detection circuit 21 is sent to the amplifier circuit 22.

The current is amplified to the amount of current necessary for the operation of the input/output interface circuit 23 and enters the input/output interface circuit 23. Input/output interface circuit 23 receiving this signal
transfers this signal as a leakage current detection signal 30 to the robot control device 27, and upon receiving this signal, the robot control device 27 turns on the indicator light 28 and takes measures such as stopping the operation of the robot 11.

FIG. 2 shows fluctuations in the current value of the auxiliary power supply circuit 13 when a leakage current generation site exists in the middle of the robot operation cycle. Detection current level 31 while no leakage current occurs
a is extremely low, and the difference from the detected current level 31b when leakage current occurs is obvious. For this reason, power supply 2
By setting the determination level 32 that takes into account the fluctuation in the circuit of 0, the leak current generation site can be clearly discovered according to this embodiment.

Note that in the example shown in FIG. 2, the operation of the robot 11 is not stopped when leakage current is detected. Further, the operation of the sub power supply circuit 13 is not performed while the main power supply circuit 12 is in actual operation, but is carried out without welding during a periodic system failure inspection.

According to this embodiment, leakage of welding current can be automatically and accurately detected in advance during system failure inspection that is carried out periodically, and leakage of welding current can be detected in advance during system failure inspection, and the power supply cables 5, 6 and conduit tubes 7. It is possible to prevent the replacement of parts or repairs due to the occurrence of welding defects in the product, and it is possible to improve productivity and welding quality. Furthermore, it is possible to prevent fires caused by heat generated by the power supply cables and damage to unused wires.

In the above embodiment, the leak current detection circuit 21 is connected to the welding power source 1.
Although the case where the detection circuit 21 is provided inside the welding power source 1 has been described, the detection circuit 21 may be provided separately outside the welding power source 1 or may be provided inside an external control box such as the robot control device 27. Further, an alarm buzzer may be activated in addition to the indicator light 28.

〔Effect of the invention〕

As described above, according to the present invention, a leakage current detection circuit is provided in parallel with the main power supply circuit connected to the arc welding power source, so that welding current leakage can be automatically and accurately detected during system failure inspection. be able to. As a result, it is possible to prevent the production line in operation from being stopped and the product to be repaired, and it is possible to improve productivity and welding quality.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of an arc welding power source according to the present invention, FIG. 2 is a graph showing a leak detection current according to this embodiment, and FIG. 3 is a block diagram showing a power supply mechanism in resistance welding. . 1... Welding power source, 2... Welded member, 10.
...Welding wire (consumable electrode), 12... Main power circuit, 13... Sub-power circuit, 2
DESCRIPTION OF SYMBOLS 1... Leak current detection circuit, 22... Amplification circuit, 23... Input/output interface circuit, 26... Switch.

Claims (1)

[Claims] (1) A main power supply circuit that applies the voltage necessary for arc welding between the consumable electrode and the workpiece to be welded, a sub-power supply circuit connected in parallel to the main power supply circuit via a changeover switch, and the sub-power supply circuit. A detection circuit provided in the circuit to detect leakage current generated in the main power supply circuit, an amplifier circuit to amplify the output of the detection circuit, and a leakage current to the outside by inputting the output amplified by the amplifier circuit. An arc welding power source characterized by being provided with an input/output interface circuit that outputs a detection signal.