JPS6068162A - Arc welding machine - Google Patents

Abstract

PURPOSE:To simplify circuit and to improve arc welding by providing freewheeling diodes and a reactor, etc. and performing inversion of current polarity and control of current value only by controlling switching elements. CONSTITUTION:An arc welding machine consists of a DC power source 6, plural switching elements T1-4, a driving circuit 16 for driving said elements, freewheeling diodes D1-4 and a reactor 11. The elements T1-4 form a bridge circuit 13 and are connected to the power source 6. The diodes D1-4 are provided for each of the elements T1-4. The reactor 11 is connected to the output side of the circuit 13. The circuit is simplified by the above-mentioned welding machine and base metals 5 are satisfactorily welded by a torch 3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an AC arc welding machine that produces a difference in current values of positive and negative polarities. AC arc welding machines, such as TIG welding machines used for aluminum welding, alternately reverse the polarity of the negative electrode side (sp) and the positive electrode side (RP), so that both positive and negative waveforms are rectangular. The arc is sustained by being in a state of
This is desirable for stable welding. Furthermore, it is preferable to shorten the period of polarity of RP, which produces a cleaning action, and to lengthen the period of SP, which causes a large amount of base metal melting, from the viewpoint of increasing welding efficiency. FIG. 1 shows an example of this waveform. FIG. 2 shows one means for obtaining the preferable output waveform shown in FIG. 1. Reference numeral 1 indicates a DC power supply that is controlled by a thyristor or the like and outputs a predetermined constant output current. By using the switching elements 21 to 24 to alternately conduct the output of the DC power supply 1 to the diagonal elements 21 and 24 or 22 and 25, an AC voltage is applied between the torch 3, which is the load, and the base material 5. Generate arc 4.

In FIG. 3, reference numeral 6 denotes a rectified power supply which does not control the output current, but controls the output current by switching the transistor 8 and its pulse width.

The transistor TI-T4 is the switching element 2 in FIG.
It operates in the same way as 1 to 24. In the conventional power supply shown in Fig. 2, the DC power supply 1 is large because it includes a current control element, and the responsiveness is poor, making it difficult to adjust the positive and negative currents. Conventional power supplies require a large number of transistors, resulting in complex circuits and high costs.

The present invention is an arc welding machine that eliminates the drawbacks of the prior art and has a simple power supply circuit using fewer switching elements.

Practical examples of the present invention will be described in detail below with reference to the drawings. FIG. 4 is a circuit diagram showing an embodiment of an arc welding machine according to the present invention. In this figure, the same parts as in FIG. 3 are given the same reference numerals. 11 is a smoothing reactor connected to the output end of the bridge circuit on the torch 3 side. 12 is a current detection device connected to the output end of the bridge circuit on the base material 5 side. Transistor T1+ constituting the IJ circuit 13
Freewheel diodes DI and D2 +Da +D4 are connected to 72 + Ta and T4, respectively.

14 is a reference signal generation circuit for setting the welding current value;
Generates a signal or pulse signal indicating a voltage value according to a set current value. Reference numeral 15 denotes a comparison circuit to which the output of the reference signal generation circuit 14 and the output of the current detection device 12 are applied, and compares the setting signal and detection signal from both circuits. 16 is a drive circuit that drives the switching transistors of the bridge circuit 13, and depending on the magnitude of the difference signal from the comparison circuit 15, the pair of transistors T1*T4 and the transistors Ts++Ta
The rate at which the pairs are alternately turned on and off is changed.
``That is, the drive circuit 16 is as shown in FIG. 6, and includes a reference clock pulse generation circuit 17, a frequency dividing circuit 18,
NOT circuit 19, on-delay circuit 20° 21 AND circuits 22, 23, sawtooth wave generator 24 and comparison circuit 2
Consists of 5. The output terminal of the sawtooth wave generator 24 is connected to one side of the two long terminals of the comparator 24, and the output terminal of the comparison circuit 15 is connected to the other side. The output of the comparator circuit 25 is connected to one input terminal of the divider circuits 22 and 23.
The output of the frequency divider circuit 18 is connected to the other input of the ND circuit 22.
Signals are input via the 7 circuit 19 and the on-delay circuit 20. The output of the frequency divider circuit 1B is connected to the other input of the door circuit 21 so that a signal via the on-delay circuit 21 is input thereto.

When the pair of transistors T1e and T4 is ON, the welding current is
Transistor Tll base material 5, torch 3, reactor 11
, transistor T4, and transistor T4.
2s When the Ts pair is ON, the welding current is the transistor T
It spreads in the order of zs reactor 11, torch 3, base material 5, and transistor T3. Next, the operation will be explained using FIGS. 5 and 6. FIG. 5 is a waveform diagram showing the operation and current of each transistor. Transistor T1 is turned on at a relatively high frequency.

OFF t-<return, transistor T4 is ON during that time
Continue. At this time, transistors T11 and T3 are OFF.
maintains the state of When the transistor T1 and the door 51 are ON, the current 11 flows through the transistor T1% base material 5, the torch 3, the reactor 11, and the transistor T4 in this order, as shown in FIG. Then transistor TI is O
When it becomes FF, the energy stored in the reactor 11 is released and the current 12 flows through the transistor T4 and the diode Do.
s Base material 5. Torches are shed in the order of 3. Transistor T1
The arc 4 continues because currents 11 and 12 are alternately supplied between the torch 3 and the base metal 5 while the torch is repeatedly turned on and off.

The current at this time is similar to waveformer 1, and the current value is ON.

It is determined by changing the OFF interval or ratio.

Next, the transistors Tl + Ta are turned off, and the transistors T2 + T3 are turned on. transistor T
2 is a relatively high frequency (several KHz to several tens of Keg)
The transistor T3 continues to turn on during the ON and OFF cycles. Since the current flowing in the arc load flows in the opposite direction as shown by waveform I2, Table 1 is necessary for cleaning the base material 5! supply flow. The inversion frequency of this current is lower than the ON and OFF frequencies of the transistors Tl and 'I'2, approximately several tens of z to IKh, and the output of the clock pulse generator 17 is divided by the frequency dividing circuit 18. This is the repetition frequency of the square wave signal.

One of the outputs of this company circuit 18 is connected to the on-delay circuit 2.
This becomes a rectangular wave T4 whose rise is slightly delayed by 11 compared to 1 and is supplied to the phantom circuit 23.

, 23 are applied with pulses that are repeated at a high frequency, and drive the transistor T1 with a pulse train of 1 as a result of interpolating the rectangular wave T4.

Turn on to set the welding current value of pulse train T1 to a predetermined value.
, OFF ratio (duty) is t+! It is designed to be regulated. The detected current is compared with the base signal by comparator P5, and a difference signal corresponding to the difference is input to comparator 25. In comparison n25, a predetermined high frequency (number K 7
7g - a sawtooth waveform of several tens of degrees) and converted into a pulse signal. The welding current is set to increase as the ON time (H level) of this pulse signal becomes longer, and the result of interpolating the rectangular wave signal in circuits 22 and 23 is the transistor drive signal TiIT2. Square wave signal” *
Ts is transistors T1 and Tss and transistor T2
A slight delay time is provided by on-delay circuits 20 and 21, respectively, so that I4 and I4 do not turn on at the same time. Still welding current waveform ■1 e I2 beam actor 11
They become almost connected due to the function of This delay time can be determined by adjusting the clock pulse α and OFF without using a delay circuit.
It is also possible to make a decision taking into account the timing.

By changing the delay times of the on-delay circuits 20 and 21, the times of the welding currents II and I2 can be changed. However, it is possible to conduct the energization time of the currents If and I2 by connecting two on-delay circuits in series; in short, any circuit that can adjust the period of polarity reversal required during arc welding is sufficient. .

Figure 8 shows the transistor T4 p Ta
IT! FIG. 4 is a waveform diagram for explaining the operation when ON and OFF driving is performed at the same cycle as . In this case, the transistor drive signal is TI = Tj t I2 =T; Therefore, the drive signal output from the drive circuit 16 is
Only the signal Tl+I2 output from 2 and 23 is sufficient, and the signal Ta+I4 is not necessary. When the transistors T1 and I4 are in the ON state, 1! as shown in FIG. 9 (same as in the OFF state). When the L flow 11 flows and becomes OFF' state,
The energy stored in the reactor 11 is the diode Da +
Base material 5. A current 12 flows as it is emitted through the torch 3 and the diode D2. If the polarity is reversed, the diode D4. Torch 3. The energy stored in the reactor 11 is released via the base material 5 and the diode D1. Therefore, welding progresses due to the welding currents I2 and Ia. In this case, the current attenuation (depending on the impedance of the power source) is much higher than in the off-diagram embodiment, and the ripple of the current is much higher. An alternating current flows through the reactor 11, causing a voltage drop, but the necessary inductance value of the reactor only needs to be sufficient for a rectangular wave voltage with a high frequency. The influence of the reactor component can be reduced. The method of energizing a transistor is not limited to the above method, but as described above, the present invention provides a method in which the energy emitted by the reactor connected in series with the load is connected to the current. Since the arc welding machine has a freewheel diode connected to the output side of the bridge circuit and an adle, the current polarity can be reversed and the current value can be controlled only by controlling the switching element. The circuit becomes simpler. Furthermore, since the switching element was turned on and off by a high frequency switching signal, the response was good and arc breakage did not occur.

Further, according to the present invention, since the polarity ratio of the power source can be adjusted, good arc welding can be performed by increasing the ratio of positive polarity, which has deep penetration, and decreasing the ratio of reverse polarity, which has a cleaning effect. There is.

[Brief explanation of drawings]

Figure 1 is a waveform diagram showing the arc welding waveform, Figures 2 and 3
The figure is a block diagram showing a conventional arc welding machine. Fourth
The figure is a block diagram showing one embodiment of the present invention, and FIG.
FIG. 6 is a block diagram showing a specific example of the drive circuit of FIG. 5, and the OFF diagram is a partial diagram of FIG. 4. 8 and 9 are waveform diagrams and circuit diagrams illustrating the operation of another embodiment of the present invention. 1... DC power supply, 2... Bridge circuit, 21゜22
．． 23.24...Switching element, Tl lT2
1T31T4...Transistor (switching element)
, 3... Torch, 4... Arc, 5... Base material, 1
1... Smoothing reactor, 12... Current detection device, 1
3... Bridge circuit, DI, D2. D3. D4...
Freewheel diode, 14... reference signal generation circuit,
15... Comparison circuit, 16... Drive circuit, 17...
Clock pulse generation circuit, 18... Branch circuit, 19.
...NoT circuit, 20.21...On delay circuit, 22.23...N0 circuit, 24...Sawtooth wave generation circuit. Sai Z 7th Figure 7th Figure 8

Claims (3)

[Claims] (1) A DC power supply, a plurality of switching elements constituting a bridge circuit connected to the DC power supply, a drive circuit for driving this switching element, a freewheel diode provided for each of the switching elements, and the bridge circuit. An arc welding machine characterized by having an acdle connected to the output side of the arc welding machine. (2) Claims characterized in that the bridge circuit is characterized in that two pairs of alternately driven switching elements are driven in short cycles, and the other switching elements are driven in longer cycles than the one switching element. The arc welding machine according to item 1. (3) The bridge circuit consists of two pairs of switching elements that are driven alternately, and the switching elements of each pair are driven at the same period.
Arc welding machine described in section.