JP2614523B2 - Arc welding machine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an inverter type arc welding machine.

2. Description of the Related Art FIG. 4 shows a configuration example of a conventional inverter type arc welding machine. In FIG. 4, 1 is an input terminal of an arc welding machine to which an AC power supply is connected, 2 is a rectifier on the primary side for converting AC to DC, 3 is a smoothing capacitor, and 4 is a full bridge configuration of four transistors. And corresponds to a welding output control element. 5 is a main transformer for stepping down to a voltage required for arc welding, 6 is a rectifier on the secondary side, 7 is a reactor for smoothing, 8 is an output terminal of the arc welding machine, 9 is a base material which is an object to be welded, Numeral 10 denotes a welding wire, 11 denotes a current-carrying contact tip, and 12 denotes a drive circuit for driving the output control element 4.

Next, the operation of the conventional example will be described. The AC power input to the input terminal 1 of the arc welding machine is rectified to DC by the rectifier 2, then smoothed by the smoothing capacitor 3, and converted to high frequency AC by the welding output control element 4. This high-frequency AC voltage is converted into a low voltage suitable for welding by the main transformer 5, rectified by a rectifier 6, smoothed by a smoothing reactor 7, output from an output terminal 8, and output from a welding wire. An arc is generated between 10 and the base material 9.

The switching frequency of the transistors constituting the output control device 4 by the drive circuit section 12 is set in consideration of the losses due to switching of the transistors, as shown in FIG. 5, the startup t ₀ to arcing during t ₁ and, the same frequency f ₂ has been used from the arc generated at the time t ₁ until the arc at the end of t _2.

In such a configuration, in order to increase the switching frequency of the transistor, it has been conventionally dealt with by increasing the capacity by connecting the transistors in parallel.

However, in such a conventional arc welding machine,
If the switching frequency f ₂ of each of the transistors included in the output control device 4 is set to an audible frequency range, raspy inverter sound is a problem that occurs after activation.
In particular, when there is no load from the start to the generation of an arc sound due to the generation of an arc, only the inverter sound is generated, and there is a problem that the user feels harsh.

SUMMARY OF THE INVENTION An object of the present invention is to solve such a conventional problem, and an object of the present invention is to provide an arc welding machine that prevents generation of an unpleasant inverter sound when no load is applied from starting to generation of an arc.

Means for Solving the Problems In order to achieve the above object, the present invention detects a case where a welding current is flowing and a case where a welding current is not flowing, and controls welding output when a welding current is not flowing. the switching frequency of the transistors of the elements in the frequency f ₁ of the audible frequency outside, when the welding current is flowing, in which the switching frequency of the transistors is configured to set the frequency f1 frequency f2 lower than the .

Effect of the Invention With the configuration described above, the switching frequency of the transistor can be set to the frequency f1 outside the audible frequency range at the time of no load from the start to the occurrence of the arc because of the above configuration. Can be prevented.

Embodiment FIG. 1 shows an embodiment of the present invention, and the same elements as those of the conventional example shown in FIG. 4 are denoted by the same reference numerals. In FIG. 1, 1 is an input terminal of an arc welding machine to which an AC power supply is connected, 2 is a rectifier on the primary side for converting AC to DC, 3
Is a smoothing capacitor, and 4 is an inverter circuit composed of four transistors in a full bridge configuration, and corresponds to a welding output control element. 5 is a main transformer for stepping down to a voltage required for arc welding, 6 is a rectifier on the secondary side, 7 is a reactor for smoothing, 8 is an output terminal of the arc welding machine, 9 is a base material which is an object to be welded, Numeral 10 denotes a welding wire, 11 denotes a current-carrying contact tip, and 12 denotes a drive circuit for driving the output control element 4. 13 is a current shunt connected between the intermediate tap of the main transformer 5 and the negative side of the output terminal 8, 14 is a current value detecting unit connected to the current shunt 13 to detect a welding current value, and 15 is a current value detecting unit. The welding current presence / absence determining unit 16 determines whether the current is flowing or not flowing based on the welding current value.The driving circuit unit 16 determines whether the welding current is flowing or not flowing. 12 is a frequency command signal setting circuit that outputs different frequencies to 12.

FIG. 2 shows a configuration example of the welding current presence / absence determining unit 15 and the frequency command signal setting circuit unit 16. Reference numeral 151 denotes a comparator which compares the current value output signal Iao detected by the current value detection unit 14 with the reference current value signal Ias. 161 comparator 151 output Vc of the frequency switching selector to be switched by the value of the, 162 and 163 by applying a reference voltage Vcc min f ₁ Hz command signal Vf ₁ frequency setting resistor for generating, 164 and
165 is a frequency setting resistor for dividing the reference voltage Vcc to generate an f ₂ Hz command signal Vf ₂ .

Next, the operation of the above embodiment will be described with reference to the timing chart of FIG. First, the arc welding machine, starts at time t _0, the arc is generated at time t _1. Since between start time t ₀ ~t ₁ until the arc occurs (no load) is not welding current flows, the output signal Iao of the current value detection unit 14 does not reach a predetermined value, the output Signal I
The output Vc of the comparator 151 of the welding current presence / absence determination unit 15 receiving ao
Is at the L level, and the frequency switching selector 161 of the frequency command signal setting circuit unit 16 outputs the f ₁ Hz command signal Vf ₁ outside the audible frequency range.
Choose the side. Then, when the arc is generated at the time t _1,
The welding current flows, the output signal Iao of the current value detection unit 14 exceeds a predetermined value, and the welding current presence / absence determination unit 1 receiving the output signal Iao
Since the output Vc of the comparator 151 of FIG. 5 turns to the H level, the frequency switching selector 161 of the frequency command signal setting circuit 16 is set to f ₁ Hz.
Select the smaller f ₂ Hz command signal Vf ₂ side. The f ₁ Hz command signal Vf ₁ and the f ₂ Hz signal command signal Vf ₂ output from the frequency command signal setting circuit section 16 are input to the drive circuit section 12, respectively. The switching of the switching frequency of No. 4 is performed.

As described above, according to the embodiment, the current value detection unit 14 detects the welding current value, and the welding current presence / absence determination unit 15 determines the presence or absence of the welding current based on the detected value. At the time of no load until an arc is generated, the frequency command signal setting circuit section 16 outputs a frequency command signal outside the audible frequency range.
Since the vf ₁ is output to the drive circuit unit 12 drives the transistor of welding output control device 4, it is possible to prevent the occurrence of no-load of the inverter noise.

Advantageous Effects of the Invention As is clear from the above embodiments, according to the arc welding machine of the present invention, the switching frequency of each transistor in the welding output control element, at the time of no load from the start of low switching loss to the time of arc generation, Since it can be set to a high frequency outside the audible frequency range, it is possible to eliminate the unpleasant inverter noise at the time of no load, which was conventionally generated, and realize this without increasing the capacity by parallel connection of transistors etc. Therefore, the number of parts and the number of assembling steps can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of an arc welding machine showing one embodiment of the present invention, FIG. 2 is a circuit diagram showing a configuration of a welding current presence / absence determining section and a frequency command signal setting circuit section in one embodiment of the present invention, FIG. 3 is a timing chart showing an operation in one embodiment of the present invention, FIG. 4 is a schematic block diagram showing a configuration example of a conventional arc welding machine, and FIG. 5 shows a transition of a switching frequency of a transistor in a conventional example. It is a timing chart. 1 ... input terminal of arc welding machine 2 ... rectifier 3 ...
Smoothing capacitor, 4 ... welding output control element, 5 ... main transformer, 6 ... rectifier, 7 ... smoothing reactor, 8 ...
Output terminal, 9: base material, 10: welding wire, 11: current-carrying contact tip, 12: drive circuit unit, 13: current divider, 14: current value detection unit, 15: welding current Presence / absence determination unit,
16: Frequency command signal setting circuit section, 151: Comparator, 161
... frequency selector, 162, 163, 164, 165 ... frequency setting resistor.

Claims (1)

(57) [Claims] 1. A welding output control element constituted by a bridge circuit of transistors, a drive circuit section for driving each transistor of the welding output control element, and a welding current value controlled by the welding output control element is detected. A current value detection unit that outputs a current value signal, and a welding current presence / absence determination unit that outputs a welding current presence / absence determination signal by discriminating a case where a welding current is flowing and a case where the welding current is not flowing with the current value signal as an input. The switching frequency of each transistor of the welding output control element to a frequency f1 outside the audible frequency range when the welding current is not flowing with the welding current presence / absence determination signal as an input, and when the welding current is flowing, the respective transistors are switched. The switching frequency of the frequency lower than the frequency f1
a frequency command signal setting circuit for outputting a frequency command signal to the drive circuit when the frequency is set to f2.