JPS62224478A - Control circuit for pulse arc welding machine - Google Patents

Abstract

PURPOSE:To reduce generation of heat of an output semiconductor element and to prevent the service life from shortening by reducing a peak value of a pulse current when it is detected that a frequency detection means attains more than preset frequency. CONSTITUTION:A wire feed circuit 2 feeds a wire to a weld zone according to the feed speed set with a feed speed setter 1. Next, a pulse frequency setter 3 outputs a signal with the corresponding frequency to an output control circuit 5 and a converter 7 and a voltage comparator 8 compares the analog signal voltage with the reference voltage. When the analog signal voltage is larger than the reference voltage, an analog switch 9 is made on and a subtracter 10 subtracts the analog signal voltage from a peak inputted from a pulse peak value setter 4. Next, an output control circuit 5 outputs an output control signal as a waveform control signal of the pulse current having the prescribed peak value, the prescribed pulse width and the prescribed frequency. Next, the output semiconductor element 6 performs a switching action and controls an output current and supplies the pulses current in accordance with the waveform control signal and the welding is performed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a control circuit for a pulse arc welding machine, and more particularly to a method for protecting a semiconductor element that controls the output current of a control circuit for a pulse arc welding machine from thermal damage. This invention relates to a control circuit for a pulse arc welding machine.

[Prior Art] FIG. 4 is a block diagram of a control circuit of a conventional pulse arc welding machine. In Fig. 4, (1) is a feed speed setting device that sets the feed speed of the consumable electrode (hereinafter referred to as wire), and (2) is a wire feed motor (not shown) that rotates at the set feed speed. Wire feeding circuit, (3) is a pulse frequency setter that outputs a frequency signal of a frequency corresponding to the set feeding speed, (4) is a pulse peak value setter that sets the peak value, (5) is a peak (6) an output control circuit that outputs an output control signal based on the value and frequency signal output;
is an output semiconductor element that performs switching operation according to an output control signal.

Next, the operation of the control circuit of the conventional pulse arc welding machine will be explained. ° First, the wire feeding circuit (2) rotates the wire feeding motor according to the feeding speed set by the feeding speed setting device (1), and feeds the wire to the welding part (not shown). do. Next, when the pulse frequency setter (3) outputs a frequency signal of a frequency corresponding to the setting value of the feed rate setter (1) to the output control circuit (5), the output control circuit (5)
) according to the frequency signal and peak value, the predetermined peak value,
An output control signal is output as a pulse current waveform control signal having a predetermined pulse width and a predetermined frequency.

Next, the output semiconductor element (6) performs a proper switching operation according to the waveform control signal to control the output current, and supplies a pulsed current according to the waveform control signal between the wires to be welded (not shown). Perform welding.

Next, FIG. 5 is a diagram showing signal waveforms of various parts of the control circuit of the conventional pulse arc welding machine shown in FIG. 4. The control circuit of this pulse arc welding machine has a period TI, a peak value I'
Waveform control signal a of P or period T2 (period T 1 >
72), for the waveform control signal C (see Fig. 5 (a) or (c)) with the peak value I'p, the pulse current with the period TI% peak value IP or the pulse current with the period T2% peak value Ip. d (see FIG. 5(b) or (d)).

In this case, the pulse current S, d has a ripple R1 at the pulse peak and a ripple R2 with respect to the base current due to the switching operation of the output semiconductor element (6).

Furthermore, the pulse currents S and d have slopes S and S2 at the rise and fall of the pulse current due to the electromagnetic energy corresponding to the inductance contained in the output section of the welding machine. Therefore, the waveform of the pulse current is generally slightly different from the waveform of the waveform control signal.

The critical current value is set much higher than the critical current value of the wire used. This is because the pulse frequency is low, especially when welding with a low current, and the wire is spray-transferred between the time when the pulse current b (see FIG. 5(b)) falls and then rises. Increasing the experimental value, for a mild steel wire of 1.2 Φ in a shielding gas atmosphere of 80% Ar and 20% C, the critical current value for spray transfer is reached when the pulse current value is about 35 OA. The actual peak value is 450 A.
It is set before and after. If the peak value is like this,
Even if the protruding length between the wires to be welded changes, safe spray transfer can be ensured and welding can be performed with very little spatter.

[Problems to be Solved by the Invention] By the way, in the conventional pulse arc welding machine control circuit having the above configuration, when the output current is increased and used at a value close to the rated current, the pulse frequency must be increased considerably. be.

Therefore, the peak value is originally set high and the pulse current is used to output semiconductor! 7 of 6. tree·
Therefore, there was a problem in that the control circuit of a pulse arc welding machine generated much more heat than the control circuit of a welding machine with pure DC output characteristics. .

FIG. 6 is a diagram showing the pulse current IX of the pulse arc welding machine at the rated output and the output current IY of the welding machine having pure DC output characteristics. In the case of the same rated output, even if the average output current value is the same as the pulse current (1) and the 8 output current (ry), the pulse arc welding machine has a poor waveform rate. Therefore, the pulse arc welding machine generates much more heat in the output semiconductor element (6) than a welding machine having pure DC output characteristics. In particular, switching loss at pulse peak current increases rapidly when its peak value is high. For this reason, the cooling of the output semiconductor element (6) of a pulse arc welding machine needs to be much more efficient than that of a welding machine with pure DC output characteristics, and it must be forced by large cooling fins and a large fan with a large air volume. Must be air cooled. for example,
Even if you try to make the pulse arc welding machine smaller and lighter by using a high-frequency inverter in the output semiconductor element (6) and making the main circuit transformer (not shown) smaller and lighter, the cooling fins and large fan are too large. ,Can not. Moreover, if cooling fins and a large fan are provided, the price of the pulse arc welding machine will increase.

The present invention has been made to solve the above problems,
An object of the present invention is to provide a control circuit for a pulse arc welding machine that can suppress heat generation of an output semiconductor element.

[Means for Solving the Problems] Therefore, the present invention includes a feeding speed setting device for setting the feeding speed of the consumable electrode, a wire feeding circuit for rotating the wire feeding motor at the feeding speed, and a feeding speed setting device for setting the feeding speed of the consumable electrode. A pulse frequency setter that outputs a frequency signal with a frequency corresponding to the speed, a pulse peak value setter that sets the peak value of the pulse current, and an output control circuit that outputs an output control signal based on the peak value and the frequency signal. , switching operation is performed by the output control signal,
an output semiconductor element that outputs a pulse current; a frequency detection means that detects when the frequency of the frequency signal has exceeded a preset frequency; and a frequency detection means that detects when the frequency of the frequency signal has exceeded the set frequency. When this is detected, a control circuit for the pulse arc welding machine is constructed from a subtraction means that outputs a value obtained by subtracting a value corresponding to the frequency of the frequency signal from the peak value as the peak value to the output control circuit.

[Function] In the control circuit of the pulse arc welding machine having the above configuration, the wire feeding circuit feeds the wire at the feeding speed set by the feeding speed setting device. When the frequency detection means detects that the frequency of the frequency signal output from the pulse frequency setter has exceeded the preset frequency, the subtracter subtracts the value corresponding to the frequency of the frequency signal from the peak value output from the pulse peak value setter. The output control circuit outputs the output control signal based on the peak value and frequency signal output from the subtracter, and the output semiconductor element outputs the value subtracted from the subtracter as the peak value.
n + 'ノ、su7M11 rights 1. Parref Yukiteru is the power of the field.

[Example 1] Hereinafter, an example of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram of a control circuit for a pulse arc welding machine according to the present invention. In Figure 1, (1) is a feed speed setting device that sets the wire feed speed, (2) is a wire feed circuit that rotates the wire feed motor at the set feed speed, and (3) is a wire feed circuit that rotates the wire feed motor at the set feed speed. (7) is a pulse frequency setter that outputs a frequency signal with a frequency corresponding to the set feeding speed; (7) is a converter that converts the frequency signal into an analog signal voltage; (8)
is a voltage comparator that compares the analog signal voltage with a preset reference voltage, (9) is an analog switch that is turned on and off by the voltage comparator (8), and (4) is used to set the peak value of the pulse current. Pulse peak value setter, (lO) is a subtractor that subtracts a predetermined value from the set peak value, (5)
(6) is an output control circuit that outputs an output control signal based on the subtracted peak value and frequency signal output, and (6) is an output semiconductor element that performs a switching operation based on the output control signal.

Next, the overall operation of the control circuit for the pulse arc welding machine according to the present invention will be explained. First, the wire feeding circuit (2
) rotates the wire feed motor according to the feed speed set by the feed speed setting device (1) to feed the wire to the welding part. Next, when the pulse frequency setter (3) outputs a frequency signal with a frequency corresponding to the set feeding speed to the output control circuit (5) and the converter (7), the converter (7)
converts the frequency signal into an analog signal voltage, and a voltage comparator (8) compares the analog signal voltage with a reference voltage.

The voltage comparator (8) is based on the analog signal voltage when comparing voltages! ! When the lightning voltage is low, it does not operate at all.

Also, when the analog signal voltage is greater than the reference voltage,
Turn on the analog switch (9). When the analog switch (9) is turned on, the subtracter (10) subtracts the analog signal voltage input as a subtraction input from the peak input from the pulse peak value setter (4) as an input to be subtracted. Therefore, if the analog switch (9) is off, that is, if the frequency of the frequency signal is below the frequency, the set value of the pulse peak value setter (4) is output as is to the output control circuit (5). It turns out. If the analog switch (9) is on, that is, if the frequency of the frequency signal is higher than that frequency, the peak value of the pulse peak value setter (4) will decrease even if the frequency of the frequency signal becomes higher than that. I will do it.

Next, the output control circuit (5) generates a pulsed current waveform control signal having a predetermined peak value, a predetermined pulse width, and a predetermined frequency according to the frequency signal and the set peak value or the subtracted peak value. Outputs the output control signal. Next, the output semiconductor element (6) performs a proper switching operation based on the waveform control signal to control the output current, and a pulse current according to the waveform control signal is supplied between the wires to be welded to perform welding. .

Note that when the control circuit for the pulse or arc welding machine according to the present invention is used near the rated output, the peak value will be smaller than the set peak value, so the subtracted value of the subtracter (lO) will be the value at the rated output. The peak value of the output pulse current is set to be equal to or higher than the critical current of the fixed wire.

Next, FIG. 2 is a diagram showing the relationship between the wire feed amount W and the peak value IP of the output pulse current. The wire feed amount W is W
When 1, the output pulse current has a predetermined pulse frequency. When the wire feed amount W exceeds WI, the peak value IP of the output pulse current gradually decreases, and the wire feed amount W exceeds WI.
When becomes the wire feeding amount WMA x at the rated output, it becomes minimum. Here, if the critical current is IPS, the wire feeding amount W is O<W<W.

In the range of , the peak value IP becomes IPI, and when the wire feed amount W is in the range of WH<W<WMAX, the peak value 2 becomes Tps<IP2<rp<Ipr. Therefore, the frequency f=1/T2 is set so that the pulse frequency of the output pulse current disappears. If the frequency is higher than this, the pulse energy for one pulse of the pulse arc welding machine's Norse current ■8 at the rated output will be greater than when the base current is clearly visible, so it will be applied to the wire. There will be too much heat. If the pulse frequency of the output pulse current is set to f = 1/T2, even if the peak value is lowered, as long as the value is greater than or equal to the critical current value, safe spray transfer can be performed, and the influence of protrusion length variation can be achieved. I don't receive it. If the pulse peak value is decreased as the average output current is increased, heat loss, ie, heat generation, of the output semiconductor element (6) at the rated output is reduced. As a result, the cooling fins and forced air cooling fan for the output semiconductor element (6) can be made smaller and lighter.

Next, FIG. 3 is a block diagram showing another embodiment of a control circuit for a pulse arc welding machine according to the present invention. In addition, the third
In the figure, parts that perform the same functions as in Figure 1 are given the same reference numerals, and in this embodiment, the analog signal voltage output from the converter (7) is In addition to the cathode of (11), the anode of Zener diode (11) is connected to the resistor (
12) to the subtractor (10) as a subtraction input. By selecting an appropriate Zener voltage, an effect substantially similar to that of the embodiment shown in FIG. 1 can be obtained. That is, when the analog signal voltage corresponding to the frequency signal of the pulse frequency setter (3) is smaller than the Zener voltage, the Zener diode (11) is off, so the peak of the pulse peak value setter (4) is The value will be output as is to the output control circuit (5). Also, when the analog signal voltage becomes larger than the Zener voltage, the Zener diode (11) is turned on, and the analog signal voltage is input to the subtracter (9) via the resistor (12), and the pulse peak value setter (4) ) is subtracted and output to the output control circuit (5).

[Effects of the Invention] As explained above, according to the present invention, when the frequency detection means detects that the frequency of the frequency signal becomes equal to or higher than the preset frequency, the subtracter changes the frequency of the frequency signal from the peak value. Since the value is output as the peak value and the peak value of the pulse current is reduced, the effect of reducing heat loss, that is, heat generation of the output semiconductor element is obtained.

Furthermore, by suppressing heat generation, it is possible to protect the output semiconductor element from thermal damage and prevent the life of the output semiconductor element from being shortened due to thermal fatigue.

Furthermore, by reducing the heat generation of the output semiconductor element,
The cooling fins for the output semiconductor element and the cooling fan for forced air cooling can be made smaller and lighter, and the control circuit for the pulse arc welding machine can be manufactured at low cost.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a control circuit of a pulse arc welding machine according to the present invention, FIG. 2 is a diagram showing the relationship between the wire feed amount and the peak value of the output pulse current, and FIG. 3 is a diagram showing the pulse arc welding machine according to the present invention. A block diagram showing another embodiment of the control circuit of the arc welding machine, Fig. 4 is a block diagram of the control circuit of the conventional pulse arc welding machine, and Fig. 5 shows the conventional pulse arc welding machine shown in Fig. 4. FIG. 6 is a diagram showing the pulse current of a pulse arc welding machine at the rated output and the output current of a welding machine having pure DC output characteristics. In each figure, 1 is a feed speed setting device, 2 is a wire feed circuit, and 3
is a pulse frequency setter, 4 is a pulse peak value setter, 5
is an output control circuit, 6 is an output semiconductor element, 7 is a converter, 8
is a voltage comparator, 9 is an analog switch, and lO is a subtracter. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent: Patent Attorney Tadashi Sato Figure 2, Figure 3

Claims (4)

[Claims] (1) A feeding speed setting device that sets the feeding speed of the consumable electrode, a wire feeding circuit that rotates the wire feeding motor at the feeding speed, and outputs a frequency signal with a frequency corresponding to the feeding speed. a pulse frequency setter that sets the peak value of the pulse current; an output control circuit that outputs an output control signal based on the peak value and the frequency signal; and a switching operation based on the output control signal. and an output semiconductor element that outputs the pulsed current, and changes the frequency of the pulsed current according to the feed rate of the consumable electrode, wherein the frequency of the frequency signal is set in advance. a frequency detection means for detecting that the frequency of the frequency signal has become equal to or higher than the set frequency; and when the frequency detection means detects that the frequency of the frequency signal has become equal to or higher than the set frequency, the frequency is determined from the peak value. 1. A control circuit for a pulse arc welding machine, comprising: subtraction means for outputting a value obtained by subtracting a value corresponding to the frequency of a signal as a peak value to the output control circuit. (2) The value obtained by subtracting the value corresponding to the frequency of the frequency signal from the peak value is such a value that the peak value of the pulse current does not become at least a critical current value specific to the consumable electrode. A control circuit for a pulse arc welding machine according to item 1. (3) The frequency detection means includes a converter that converts the frequency signal into an analog signal voltage corresponding to the frequency of the frequency signal, and a voltage comparator that compares the analog signal voltage with a preset reference voltage. The subtraction means includes an analog switch that is turned on when the voltage comparator detects that the analog signal voltage is larger than the reference voltage, and an analog switch that is turned on when the analog switch is turned on. , and a subtracter for subtracting the analog signal voltage from the peak value. (4) The frequency detection means is comprised of a converter that converts the frequency signal into an analog signal voltage corresponding to the frequency of the frequency signal, and a Zener diode to which the analog signal voltage is applied. A control circuit for a pulse arc welding machine according to scope 1.