JPS60206572A - Arc welding device - Google Patents

Abstract

PURPOSE:To provide the titled device which improves arc starting by the constitution consisting in detecting the generation of a welding arc from the output voltage and current of a welding power source and feeding a welding wire at a low speed until the arc is generated then at a stationary speed after detection of the arc generation. CONSTITUTION:The arc welding device generates an arc load 14 by a constant voltage welding power source 11 between a welding wire 13 fed at a constant speed by a wire feed motor 16 provided with a motor speed regulator 18 and a base metal 15. The generation of the arc is detected from the welding voltage Va and current Ia by a means for detecting the arc generation consisting of a shunt resistor 21 for detecting electric current, an amplifier 22, a comparator 23, a reference voltage generating source 24, an AND circuit 25, a diode 26, etc. in the above-mentioned arc welding device. The welding wire 13 is fed at the low speed by a means 20 for commanding the low-speed feed until the arc generation is detected. Said means is changed over to a means 19 for commanding the stationary speed feed by a change-over means 27 to feed the wire 13 at the stationary speed after the arc detection. The plunging of the wire 13 to the base metal 15 is thus prevented.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an arc welding device that feeds welding wire at a constant speed, and particularly relates to means for improving arc start when the short-circuit current value of the welding power source cannot be sufficiently large. .

[Summary of the invention]

In arc welding equipment that feeds welding wire at a constant speed, in order to improve arc startability, (1) the wire feeding speed is reduced until the welding wire contacts the base metal and current begins to flow at the start of welding. Steady, about a fraction of the speed (Habo 2
m/min), and detects contact energization and increases the speed to a steady state.

(2) Speed up the rise of the output current at the start of welding. By taking one or both of the above measures (1) and (2), welding of the welding wire into the base metal was prevented, and 7-k was likely to occur as soon as the welding wire came into contact with the base metal. .

Measures (1) and (2) above are effective for arc welding equipment that uses a power source with constant voltage characteristics that has a large short-circuit current value, and usually the arc will break down within a short time of about 30 to 50 m5 after the current starts flowing. However, depending on the type of welding power source, good arc startability may not be obtained even if measures (1) and (2) are used together. A typical example is when an inverter is used to control the output of a welding power source.

As shown in Figure 1, a welding power source using an inverter first converts commercial AC voltage into AC with a frequency higher than the commercial frequency using a rectifier 1 and an inverter 2, then steps down the voltage using a transformer 3, and converts the secondary output to a rectifier. 4 and a DC reactor 5 to convert it into DC, smooth it, and supply it to the load. By controlling the switching period of the inverter 2 with negative feedback using the output voltage, a constant voltage characteristic as shown in Figure 2A is achieved. It has gained. This welding power source using an inverter was recently developed with the aim of making the power source smaller and lighter.However, in order to protect the switching elements (transistors, etc.) of the inverter 2, the inverter control circuit is equipped with a current limiter function. It is necessary to ensure that the output current does not exceed a certain value (point B in Figure 2), and the maximum value of the output current, that is, the short-circuit current value, is considerably lower than that of a normal constant voltage welding power source controlled by a thyristor (for example, about 500 A). However, with a normal constant voltage welding power source, it is difficult to suppress the current to 1,000 to 1,200 A).

If measures (1) and (2) above are implemented in an arc welding device that uses such an inverter-controlled constant voltage welding power source, the welding wire and base metal may Since the wire feeding speed increases from the moment of contact, (i) the short circuit time at the start of welding increases (
50 to 100 m5), it becomes difficult to transfer to arc.

(ii) The welding wire plunges into the base metal, giving a strong recoil to the torch.

(iii) As shown in FIG. 3, the welding wire 6 is welded to the matrix 7, and the wire, which has been softened by resistance heating, is greatly deformed and tends to melt and break at the thinner part (point 0).
If a large amount of the fused wire is scattered or an arc does not occur, the long cut end of the wire remains welded to the starting part, worsening the appearance of the bead.

There were problems such as.

[Purpose of the invention]

The object of the present invention is to provide a constant speed wire that enables a good arc start even when the short-circuit current value cannot be sufficiently large, and that does not cause recoil to the torch or deteriorate the appearance of the bead due to the welding wire thrusting into the base metal. An object of the present invention is to provide a feed type arc welding device.

[Summary of the invention]

If the short-circuit current value of the welding power source cannot be set sufficiently large, if the wire feeding speed is increased without releasing the short-circuit between the welding wire and the base metal, the wire will stick, causing the above-mentioned (i) to (
It has been found that this can lead to unfavorable results as described in (Blood). Therefore, the present invention provides an arc welding apparatus that includes a wire feeding motor and a motor speed governor for feeding welding wire at a constant speed, and a steady feeding system that instructs the motor speed governor to feed the wire at a steady speed. a command means, a low-speed feed command means that also commands wire feeding at a speed lower than the steady speed, an arc occurrence detection means that detects the occurrence of a welding arc from the output voltage and current of the welding power source, and the arc occurrence detection means. The output signal commands the motor speed governor to feed the wire at a speed lower than the steady speed until arc occurrence is detected at the start of welding. By providing a wire feeding speed switching means that selectively operates the steady feeding command means and the low speed feeding command means so as to command the wire feeding at a high speed, it is possible to prevent the welding wire from penetrating into the base metal. This is what I did.

(Embodiment of the invention) FIG. 4 shows an embodiment of the invention. Reference numeral 11 denotes an inverter-controlled constant voltage welding power source with a current limiter function to prevent the output current from exceeding a certain value, and its specific configuration is disclosed in Japanese Patent Application No. 57-124356, etc., so a description thereof will be omitted. do.

12 is a tip provided on the welding torch for energizing the welding wire 13; 14 is an arc load; 15 is a base material; 16 is a wire feed motor that drives the wire feed roller 17;
8 is a motor speed governor, 19 is a first potentiometer which is a steady feed command means, 20 is a second potentiometer which is a low speed feed command means, 21 is a shunt resistor for current detection, and 22 is an output to the shunt resistor 21. An amplifier 23 for detecting the flow of current Ia is a comparator, which compares the voltage vb of the reference voltage source 24 and the welding power source output voltage Va, and determines whether the output voltage Va is higher than the arc voltage. 25 is an AND circuit for detecting the occurrence of welding arc from the output of the amplifier 22 and the output of the comparator 23;
A diode 6 is provided between the comparator 23 and the AND circuit 25 to maintain the output of the AND circuit 25 during welding, and in this embodiment, the elements 21 to 26 constitute arc generation detection means. Reference numerals 27 and 28 denote buffer amplifiers, which are wire feeding speed switching means for selectively operating the first and second potentiometers 19 and 20 in accordance with the output of the AND circuit 25.

Potentiometer 19.20 determines the bias voltage Vc for motor governor 18 via diode 29.30. The motor speed governor 18 uses this bias voltage Vc
The wire feeding speed is controlled by controlling the rotational speed of the wire feeding motor 16 according to the wire feeding speed, and the armature voltage and bias voltage V of the wire feeding motor 16 are
If the configuration is such that the conduction phase of a thyristor or the like provided in the motor circuit is controlled by comparing the voltages C and the voltage difference, constant speed feeding can be maintained even if the power supply voltage fluctuates.

Next, the operation will be explained. FIG. 5 is a timing chart for explaining the operation, where (a) is the start signal and (b) is the output voltage Va.
, (C) shows the wire feeding speed, and (d) shows the change in the output current Ia.

At the start of welding, when a starting signal (FIG. 5(a)) is input from a starting switch (not shown), the constant voltage welding power source 11 initially generates a no-load voltage as shown in FIG. 5(b). At the same time, the motor speed governor 18 operates, and the wire feeding motor I6
starts to rotate, but since the welding power source 11 is in a no-load state at the beginning, only the output of the comparator 23 is HIGH (hereinafter referred to as 11 Hj+), and the output of the intensifier i' 22 is LOW.
(hereinafter referred to as ttL"), and therefore the AND circuit 25
The output of the buffer amplifier 27 is “L”, the output of the buffer amplifier 27 is “H”, and the output of the buffer amplifier 28 is “L”. The voltage is low. Therefore, the welding wire 13 is fed at a low speed of about a fraction of the steady speed (approximately 2 m/min or less).

Welding wire 13 fed at low speed touches base material 1 at point X in Figure 5.
5, the current Ia starts to flow as shown in FIG. 5(d), so the output of the amplifier 22 becomes it Hn.
Since the output voltage Va decreases due to a short circuit, comparator 2
The output of 3 becomes RL I+, so AND circuit 2
5. The outputs of the buffer amplifiers 27 and 28 remain unchanged, and the wire feeding speed remains low.

The output current Ia at this time is a low value as described above due to the current limiter function of the constant voltage welding power source 11 (Is in Fig. 5).
Therefore, the welding wire 13 does not melt immediately and remains short-circuited for a while. However, since the wire feeding speed is low, the welding wire 13 does not penetrate into the base material 15. When the welding wire 13 is eventually heated by the short-circuit current, melting occurs at or near the wire end, and a welding arc is generated (point Y in FIG. 5). Then, the output of the comparator 23 becomes (l H
I+, and the output of the amplifier 22 that detects the current is also 'H''
Therefore, the output of the AND circuit 25 is "H", the output of the buffer amplifier 27 is "L"', and the output of the buffer amplifier 28 is "H".
The output of the motor becomes rtH". As a result, the motor speed governor 1
Since the bias voltage Vc applied to 8 becomes a relatively high voltage determined by the first potentiometer 19, the wire feeding speed increases rapidly to the steady state speed, so that the arc length remains stable and the steady state enters the welding state. Once an arc occurs, the rrH'' output of the buffer amplifier 28 is input to the AND circuit 25 through the return path 31, and in order to maintain the AND circuit 25 in the state of output 11 HI+, the output is temporarily short-circuited during welding. Even if the voltage Va becomes lower than Vb, the wire feeding speed does not return to the low speed state at the start, and welding can be continued without any problem.

As described above, in this embodiment, even when the welding wire contacts the base metal and current begins to flow, the wire is fed at the low speed determined by the second potentiometer 20 until an arc is generated due to melting of the wire. As a result, the arc can be started with almost no recoil on the torch. In addition, since the welding wire does not penetrate into the base metal, arcing is more likely to occur, and the short-circuit time is shorter than when the wire feeding speed is set at a steady speed from the point of contact short circuit (point X in Figure 5). In experiments, the arc start performance can be improved by approximately 50 m5). In addition, because the amount of wire fed during a short circuit is small, there is less wire scattering when the wire is blown, and even if the wire is blown without causing an arc, the wire fragments remaining at the starting point are small, as shown in Figure 3. The long end of the wire will not be welded to the start part and cause the bead appearance to deteriorate.

FIG. 6 shows another embodiment of the invention.

In the above-mentioned embodiment, the wire was fed at the same low speed as at the beginning even during the short circuit, but better results may be obtained by further reducing the wire feeding speed during the short circuit. In order to realize this, this embodiment adds an analog switch 32 which is a low-speed feed command means during short circuit, a buffer amplifier 33 and an AND circuit 34 which are wire feed speed switching means, and the other configuration is the same as that of the previous example. This is the same as the previous embodiment.

In FIG. 6, at the beginning of welding, the output of the amplifier 22 is “
Since the output of the comparator 23 is LL I411, the outputs of the buffer amplifier 33 and AND circuit 34 are both II L II. At this time, the analog switch 32 is off and does not affect the bias voltage Vc, and the As in the previous embodiment, the welding wire 13 is fed at a low speed determined by the second potentiometer 20.

The welding wire 13 contacts the base metal 15, the output of the amplifier 22 is rrH'', and the output of the comparator 23 is LL L II
Then, the outputs of the buffer amplifier 33 and the AND circuit 34 both become LLH'', so the analog switch 32 is turned on by the output of the AND circuit 34, and the bias voltage V
Let c be OV. As a result, the motor speed governor 18 stops energizing the wire feed motor 16, and the welding wire 13 is fed at a low speed due to the inertia of the wire feed motor 16 during the short circuit.

When an arc occurs, the outputs of the amplifier 22 and comparator 23 are "H", and the outputs of the buffer amplifier 33 and AND circuit 34 are ((I, TI), so the analog switch 3
2 is turned off again and the wire feeding speed is at the steady speed determined by the first potentiometer 19.

As described above, the wire feeding speed during a short circuit can be reduced to generate an arc more quickly.

In each of the above embodiments, a case has been described in which a constant voltage power source controlled by an inverter is used as the welding power source, but a pulse source that feeds the welding wire at a constant speed using a power source with constant current characteristics that changes the output current waveform in a pulsed manner has been described. Even with arc welding equipment and the like, there are cases where the short circuit current value cannot be sufficiently large, so improvement in arc startability can be expected by implementing the present invention.

[Effects of the Invention] According to the present invention, even if the short-circuit current value of the welding power source cannot be set sufficiently high, it is possible to prevent the welding wire from plunging into the base metal at the time of starting welding, so that the welding wire can be prevented from penetrating the base metal, so that the welding wire can be prevented from thrusting into the base metal, so that the welding wire can be prevented from penetrating the base metal, so that the welding wire can be prevented from penetrating the base metal. The arc can be started quickly, and if a large amount of the wire is not scattered during fusing or arcing does not occur, the long end of the wire will not be welded to the starting part, and the bead appearance can be improved.

[Brief explanation of drawings]

Figure 1 is a block diagram of a welding power source controlled by an inverter.
Figure 2 is its external characteristic diagram, Figure 3 is a diagram showing how the welding wire melts when using conventional arc start control,
FIG. 4 is a circuit diagram showing one embodiment of the invention, FIG. 5 is a timing chart for explaining its operation, and FIG. 6 is a circuit diagram showing another embodiment of the invention. 11... Welding power source 13... Welding wire 14...
Arc load 16...Wire feed motor 18・Motor governor @19...Steady feed command means ZO132...Low speed feed command means 21-26...Arc occurrence detection means 27.28.33. 34...Wire feed speed switching means Patent attorney Junnosuke Nakamura

Claims (1)

[Claims] In an arc welding device having a wire feed motor and a motor speed governor for feeding welding wire at a constant speed, the steady feed command means for commanding the motor speed governor to feed the wire at a steady speed, A low-speed feed command means for commanding wire feeding at a speed lower than the steady speed, an arc occurrence detection means for detecting the occurrence of a welding arc from the output voltage and current of the welding power source, and an output signal of the above-mentioned arc occurrence detection means At the start of welding, the motor speed governor is commanded to feed the wire at a slower speed than the steady speed until the occurrence of an arc is detected, and from the time the arc is detected, the motor speed governor is instructed to feed the wire at a steady speed. An arc welding device characterized by comprising wire feed speed switching means for selectively operating the steady feed command means and the low speed feed command means so as to command wire feeding.