JPH02187269A - Welding output controller - Google Patents

Abstract

PURPOSE:To reduce the quantity of spatter generation without deteriorating external appearance of a weld bead by detecting the short-circuit start from the welding voltage, setting the time from the short-circuit start and outputting an operation signal to an output by-pass circuit in the set time in receipt of the output of time setting. CONSTITUTION:A voltage detector 17 detects the welding voltage. In receipt of this output, a short-circuit detector 18 detects the short-circuit start. A time setter 19 sets the time from the short-circuit start in receipt of the output of the short-circuit detector 18. The output by-pass circuit 16 is arranged in parallel with a reactor 11 on a welding circuit. A short-circuit output controller 20 outputs the operation signal to the output by-pass circuit 16 in the set time in receipt of the output of the time setter 19. An output attenuating circuit connected in series with the reactor is provided in place of the output by-pass circuit. By this method, a short-circuit transfer current is reduced without controlling low a current during arcing.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a welding output control device for a consumable electrode arc welder that repeats short-circuit and arc cycles.

(Prior art) Welding machines that repeat short-circuit and arc cycles, such as CO2 welding, generate a large amount of spatter. This poses major problems, such as complicating equipment maintenance and management, and causing paint to peel off after welding.

It is known that this spatter mainly occurs when transitioning from an arc to a short circuit and from a short circuit to an arc, and various reports have also been made that it can be reduced by suppressing the output current during the transition.

The relationship between the output current during transition from arc to short circuit (hereinafter referred to as short circuit transition current) and spatter generation, which is the problem of the present invention, is generally considered to be the following process. That is, as shown in FIG. 3(a), the molten metal 2 that has melted and accumulated at the end of the wire 1 (consumable electrode) in an arc state approaches the base material 4 as the wire 1 is fed, and eventually reaches the third A part of it comes into contact with the base material 4 as shown in Figure (b). If the short-circuit transfer current 18 (Fig. 4) is relatively high, the contact part will heat up at a high speed and blow off, and the molten metal at the end of the wire 1 will turn into an arc again in a short time. It cannot be transferred to the base material 4 and remains as shown in FIG. 3 (C1). In this state, the molten metal becomes spatter 5 and scatters because it is subjected to a strong dynamic pressure due to the arc force accompanying the re-arcing.

On the other hand, when the short-circuit transfer current i is relatively low, the contact area expands smoothly due to surface tension and the like.

Most of the molten metal at the end of the wire 1 transfers to the base material 4, and transfers to the arc with almost no remaining at the end of the wire 1, as shown in FIG. 3 (C2). Therefore, it is stable against the dynamic pressure of the arc, and there is no scattering of spatter 5.

As described above, from the viewpoint of suppressing the short-circuit transfer current to a low level in order to reduce the amount of spatter generated, two types of methods have been adopted in the past.

The first method will be explained with reference to FIG. The three-phase input is converted to DC by a rectifier 6 and smoothed by a capacitor 7, and then input to a power transistor 8, where the welding output is converted from DC to AC.The welding output is adjusted by the power transistor 8 controlled by a PWM controller 15. , a transformer 9, a rectifier 10, and a reactor 11 for removing ripples before being outputted from an output terminal 12.

Note that 13 is a feeding motor for the wire 1. When a short circuit occurs in the welding part 21, it is detected by a short circuit detector 14 that inputs the welding output voltage, and then the signal is converted into PWM for a certain period of time.
Output to controller 15. While receiving the signal for the certain period of time, the PWM controller 15 turns the power transistor 8 off.
Outputs F signal. Therefore, during this time, there is no output from power transistor 8, and short-circuit transition current 18 decreases.

A second method for suppressing the short circuit transfer current is to adjust the output of the power transistor 8 in advance to lower the output current before the short circuit occurs, that is, in the latter stage of the arc.

As such a method, for example, Japanese Patent Application Laid-Open No. 59-202173
There are some that have been disclosed.

(Problem to be Solved by the Invention) Regarding the conventional methods as described above, in the first method, the reactor 1.1 is required to improve the characteristics during arcing and to remove the oscillation ripple of the power transistor 8. Furthermore, in a short circuit state, the resistance value of the welding circuit is extremely small, so the current decay time constant determined by L/R becomes large.

For this reason, even when the power transistor 8 is in the OFF state, the short-circuit transfer current due to the self-induced electromotive force of the reactor 11 cannot be reduced completely, resulting in a problem that spatter generation cannot be effectively reduced.

In addition, in the second method, the bead appearance deteriorates if the output current is reduced during the arcing period, so the parameter settings are limited to a very narrow range that does not deteriorate the bead appearance and is effective in reducing spatter. It ends up.

Therefore, external fluctuation factors such as on-site welding (base material ~
Distance between electrodes 2 Condition of base material, type of wire.

In situations where the welding position, joint shape, etc.) is thick (which affects the appearance of the bead), the parameters must be reset each time according to the variable factors, which is very complicated.

An object of the present invention is to provide a welding output control device that significantly reduces spatter without deteriorating the bead appearance or being influenced by external fluctuation factors.

(Means for Solving the Problems) In order to achieve the above objects, the present invention provides a voltage detector that detects welding voltage, a short circuit detector that receives the output of the voltage detector and detects the start of a short circuit, and A time setting device that receives the output from the detector and sets the time from the start of the short circuit, and a welding circuit.
: An output bypass circuit arranged in parallel with the reactor,
The present invention is characterized by comprising a short-circuit output controller that receives the output of the time setter and outputs an operation signal to the output bypass circuit within a set time.

Further, for the same purpose, the present invention is characterized in that it includes an output attenuation circuit arranged in series with the reactor instead of the output bypass circuit.

(Function) According to the present invention, the current caused by the self-induced electromotive force of the reactor 11 is bypassed by the output bypass circuit at the same time as the short circuit starts, so that the short circuit transfer current can be significantly reduced. Furthermore, by connecting the resistor in the output attenuation circuit arranged in series with the reactor at the same time as the start of the short circuit, the current attenuation time constant determined by L/R can be reduced, so the short circuit transfer current can be significantly reduced.

As described above, the present invention can significantly reduce the short-circuit transfer current, so that re-arcing does not occur in a short period of time, and therefore, as shown in Figure 3 (C1), the wire ends are melted. No metal remains and becomes spatter.

Moreover, the current is reduced only after the short circuit has started, and is maintained at the normal high current during the arc period.
There is no deterioration in the bead appearance and there is no influence from external fluctuation factors.

(Embodiment) FIG. 1 shows a block diagram of an embodiment of the present invention. In the figure, reference numeral 16 denotes an output bypass circuit composed of a power transistor, which is connected in parallel with the reactor 11. The secondary circuit (welding circuit) of the welding machine includes the bypass circuit 16,
It is composed of a secondary rectifier 10 and a reactor 11, and is connected to a welding part 21 via an output terminal 12. 17 is a voltage detector that detects the welding voltage v0 from the output terminal 12;
8 is a short circuit detector composed of a comparator that compares the detected voltage v1 of the voltage detector 17 with a reference level and outputs a short circuit start signal; 19 is a short circuit detector for a preset time starting from the short circuit start signal; The time setter 20 that outputs the transition period signal is a short-circuit output controller that outputs an operation cancellation signal to the output bypass circuit 16 based on the output of the time setter 19. Other numbers that are the same as those in the blocks shown in Figure 4 have the same functions, so explanations will be omitted.
A direct current that has been rectified and smoothed from the phase input is input.

Next, to explain the operation, the power transistor 8 adjusts the welding output under the control of the PWM controller 15, and the welding voltage v0 is introduced from the output terminal 12 to the voltage detector 17, and is used in the subsequent control system. It is converted to a matching voltage voltage. The short circuit detector 18 outputs a short circuit start signal at the timing when the voltage v1 is inverted from a high level to a low level with respect to the reference level. The time setter 19 outputs a short circuit transition period signal for a preset time starting from the short circuit start signal. While this short-circuit transition period signal is being output, the power transistor 8 is turned off by the PWM controller 15.

On the other hand, the short circuit output controller 20 outputs an operation signal to the output bypass circuit 16. When the output of this short-circuit transition period signal ends, the PWM controller 15 controls the power transistor 8 with another control signal not shown in the figure, and the short-circuit output controller 20 sends an operation cancellation signal to the output bypass circuit 16. put out.

Next, the short circuit transition current i while the short circuit transition period signal is being outputted will be explained. During this period, the power transistor 8 is in the OFF state, so the current flowing out from the reactor 11 is only iL due to the self-induced electromotive force. if,
If the output bypass circuit 16 is not operating, the short-circuit transition current 18 is i,l:j.

However, when the output bypass circuit 16 is operated, a bypass current i flows, so that i, :=i1. -iB. In other words, the short-circuit transition current i is reduced by 111 minutes by the output bypass circuit, and the purpose of significantly reducing the short-circuit transition current can be achieved.

Next, FIG. 2 shows a block diagram of another embodiment of the present invention. In this embodiment, instead of the output bypass circuit 16 shown in FIG. 1, an output attenuation circuit 22 composed of a power transistor and a resistor is connected in series to the reactor 11. Further, other components not shown in the drawings and their functions are the same as those of the embodiment shown in FIG.

The short-circuit output controller 20 outputs a signal that turns off the power transistor in the output attenuation circuit 22 while the short-circuit transition period signal is output from the time setting device I9, and conversely outputs a signal that turns off the power transistor in the output attenuation circuit 22 during other periods. is turned on ('B is output. That is, during the short-circuit transition period, the resistor in the output attenuation circuit 22 is connected in series to the reactor 11.

Since the other resistances in the welding circuit are extremely small under short-circuit conditions, by adding a new resistance like this, the current decay time constant determined by L/R can be dramatically reduced. can. Therefore, the purpose of significantly reducing the short-circuit transition current i can be achieved.

Furthermore, if the setting time of the time setting device 19 is too long, the temperature of the molten metal on the base metal will drop, making it difficult to re-arc and cause arc instability. Therefore, the upper limit is determined by the heat capacity of the molten metal. Since the heat capacity of the molten metal changes depending on the welding current and welding speed, the set time can be appropriately set depending on the welding current setting value and the W4 welding speed setting value.

(Effects of the Invention) As described above, according to the present invention, it is possible to significantly reduce the short-circuit transfer current without suppressing the current in the arc. However, the amount of spatter generated can be significantly reduced without deteriorating the appearance of the bead, which is extremely useful in practice.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG. 2 is a block diagram of another embodiment of the present invention. Figure 3 is a diagram for explaining the process of spatter generation.
FIG. 4 is a block diagram showing a conventional example. 8... Power transistor, 9... Transformer, lO... Secondary rectifier, 11... Reactor, 1
2... Output terminal, 13... Wire feeding motor, 1
5...PWM controller 516...output bypass circuit,
17...Voltage detector, 1B...Short circuit detector, 1
9... Time setting device, 20... Short circuit output controller, 22
...Output attenuation circuit. Patent applicant: Matsushita Electric Industrial Co., Ltd. Representative: Kouji Hoshino”゛′l′rPaper 1, Figure 1, Figure 2, Figure 2 (cl) Figure

Claims (2)

[Claims] (1) A voltage detector that detects the welding voltage, a short circuit detector that receives the output of the voltage detector and detects the start of a short circuit, and a time that receives the output of the short circuit detector and sets the time from the start of the short circuit. A setting device, an output bypass circuit arranged in parallel with the reactor on the welding circuit, and a short circuit output controller that receives the output of the time setting device and outputs an operating signal to the output bypass circuit within a set time. A welding output control device characterized by: (2) Instead of the output bypass circuit, an output attenuation circuit is provided which is connected in series with the reactor of the welding circuit, and when the short-circuit output controller connected in series with the output attenuation circuit is within the set time of the time setting device, the output attenuation circuit 2. The welding output control device according to claim 1, wherein the welding output control device outputs an operation signal to the welding output control device.