JPS6039470B2 - arc welding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to an arc welding machine using a consumable electrode that performs arc welding by shielding the welding part with a gas mainly composed of an inert gas. This invention relates to an arc welding machine that quickly returns the arc length to a predetermined length by changing the wire feeding speed.

In general, arc welding machines that use consumable electrodes such as MIO welding have a constant current output, so that even if the welding voltage fluctuates due to the constant movement of the cathode point across the base in a steady state, , since the welding current remains unchanged, the melting speed of the wire is constant, and if the wire is fed at a constant speed, the apparent arc length, which corresponds to the distance between the wire tip and the motherboard surface, will remain constant. , the penetration of the welded part is uniform, and good welding results can be obtained.

FIG. 1 shows this type of conventional arc welding machine, in which 1 is an AC power source, and 2 is an output control consisting of a transformer connected to the AC power source 1 and a control rectifier element 2' such as a sirensor. It is a section that performs controlled rectification on AC input and outputs it.

3 and 4 are welding loads connected to the output control section 2, such as a feed wire and the base metal; 5 is a current detector that detects the output current of the output control section 2; Convert to proportional voltage and output.

6 is an output regulator that sets the output current of the output control unit 2; 7
is a first comparison amplifier, which compares the detection signal of the current detector 5 with the reference signal of the output regulator 6, amplifies the error, and outputs the result.

8 is a first phase shifter for ignition that outputs a gate signal for controlling the phase of the control rectifying element 2' of the output control section 2 based on the output of the first comparison amplifier 7; 9 is a motor for feeding the wire 3; 10
This is a motor control unit that drives the motor and controls its rotational speed, and consists of a transformer connected to the AC power supply 1 and a control rectifier element 9' such as a thyristor.

11 is a signal converter that converts the output voltage of the output regulator 6 into a voltage at a constant ratio, and 12 is a second comparison amplifier that detects the output signal of the signal converter 11 and the output voltage of the motor controller 9. The detected signal is compared with the detected signal, and the error is amplified and output.

13 is a second phase shifter that outputs a gate signal for controlling the phase of the control rectifier 9' of the motor control section 9 based on the output of the second comparator amplifier 12; This is a variable motor rotation speed fine adjuster.

Next, the operation of the arc welding machine will be explained.
The commercial alternating current of the alternating current power supply 1 is controlled and rectified by the output control section 2,
A direct current is supplied to the wire 3 and the base material 4, this current is detected by the current detector 5, and the detection signal is input to the first comparison amplifier 7. The detection signal is compared with the reference signal of the output regulator 6, and the difference is amplified and output. moreover,
A gate signal is output from the first phase shifter 8 based on the output signal of the first comparator amplifier 7, and the phase of the control rectifier 2' of the output control section 2 is controlled. The welding current supplied to the base material 4 is controlled to be a constant current, and the wire 3 is melted at a constant speed. on the other hand,
When the DC voltage obtained by controlling and rectifying the commercial alternating current by the motor control unit 9 is energized to the wire feeding motor 101, the motor 0
rotates and the wire 3 is fed.

At this time, the reference signal of the output regulator 6 is converted into a signal of a predetermined ratio by the signal converter 11 according to the input/output characteristics shown by the solid line in FIG. In other words, the signal is converted into a signal that conforms to the reference signal of the feedback control system of the motor controller 9 that controls the feeding speed of the wire 3, and the output signal of the converted signal converter 11 and the output signal of the motor controller 9 are The detection signal that detects the output voltage is compared with the second comparator amplifier 12, and the difference is amplified and output.
The control rectifying element 9 of the motor controller 9 via the phase shifter 13 of
' is controlled in phase, the output voltage of the motor controller 9 is controlled to a constant voltage, the rotational speed of the motor 10 is constant, and the wire feeding speed is also constant. Here, since the welding current and wire feeding speed are switched by one output regulator 6, when changing the welding conditions by operating the output regulator 6, the signal converter is changed accordingly. 11 by operating the motor rotation speed fine adjuster 14 to adjust the ratio of input and output. However, with the above-mentioned arc welding machine, if the arc length changes for some reason during welding, for example, if there is a step 4'' in the welded part 4' of the main village 4 as shown in Fig. 3, When the torch T moves from the position indicated by the one-dot chain line to the position indicated by the two-dot chain line where the stepped portion 4'' is located, the current flowing through the base material 4 and the wire 3 is - constant, the wire 3 melting speed is constant, and the wire Since the feeding speed of wire 3 is also constant, the protruding length of wire 3 does not change, and therefore the arc length is equal to 1 shown in the figure.
1 to 12, and when the torch T is further moved and reaches the position indicated by the solid line, the feeding motor 0 is rotated at a constant speed by the constant voltage output of the motor control section 9, and the wire 3 is fed. Therefore, the arc length becomes 11 again, but when the arc length increases to 12, penetration is insufficient and sealing of the shielding gas is insufficient, resulting in poor shielding effect and poor welding results.

Such a change in arc length occurs not only when there is a stepped portion in the welding part 3', but also due to camera shake during manual welding, resulting in a change in penetration and poor welding quality. In addition, arc starting in an arc welding machine using a consumable electrode is performed by transitioning to an arc when the wire 3 comes into contact with the base metal 4 and then separates from the base metal 4, but an arc is generated and an excessive When the current begins to flow, this current is detected by the current detector 5, and the control rectifier 2' of the output control section 2 is phase-controlled, and the output current of the output control section 2 reaches the set current in a very short time, causing an overcurrent. The arc may fail to start due to the suppression of the arc.

This invention takes into account the above-mentioned conventional problems, and is designed to quickly return to the original arc length when the arc length fluctuates during welding. This will be explained in detail with reference to the drawings from FIG. 4 onwards.

The circuit configuration in FIG. 4 differs from that in FIG. 1 in that the following symbols are added. That is, 15 is a voltage converter connected in parallel to the first comparison amplifier 7, which converts the output of the output regulator 6 into a constant voltage or a proportional voltage as shown by the solid line or broken line in FIG. do. 16 is a voltage setting device for setting a constant output voltage or minimum output voltage of the voltage converter 15; 17 is a voltage detector for detecting the output voltage of the output control section 2, that is, the welding voltage; and 18 is provided in the voltage detector 17. This is a detection signal fine adjuster that varies the ratio of the detection signal output from the voltage detector 17 to the detection voltage of the voltage detector 17 in accordance with the shielding gas used.

An adder 19 adds the reference signal of the feedback control system of the motor control unit 9 output from the signal converter 11 and the detection signal of the voltage detector 7, and performs feedback control on the second comparison amplifier 16. Outputs system command signals.

Next, the operation of the above embodiment will be explained in detail with reference to FIGS. 5 to 7.

The basic operation is almost the same as that shown in FIG. 1, and only the different points will be explained.

During steady state when welding is being performed due to arc generation, a feedback control system consisting of a current detector 5, an output regulator 6, a first comparator amplifier 7, and a first phase shifter 8
The output current of the output control section 2 is constant current controlled to a preset current value by the output regulator 6. By the way, the voltage converter 15 has a voltage setter 16 that sets the output voltage of the first comparison amplifier 7 in a steady state due to arc generation to 4.
・It is set to output a constant voltage. Therefore, in steady state, since welding is performed with a constant arc length, the output voltage of the first comparator amplifier 7 is
, and the output of the output control section 2 is controlled at a constant current by the feedback control system as shown in the characteristics between the two dotted and dashed lines in the curves A to C shown in FIG. , if the arc length becomes short for some reason, the welding voltage decreases, the output voltage of the first comparison amplifier 7 becomes lower than the output voltage of the voltage converter 15, and the first phase shifter 8
is controlled by a constant output voltage of the haze pressure converter 15, and the control rectifying element 2' of the output control section 2 is conducted at a constant phase, so that the output of the output control section 2 is controlled by the constant current characteristic as shown in FIG. A
The quasi-constant voltage characteristic or constant voltage characteristic shown by the curve C is obtained. Therefore, for example, when the torch T is moved in the opposite direction of the arrow in FIG. 7 from the position indicated by the two-dot chain line to the position indicated by the one-dot chain line, arc breakage is less likely to occur because the welding voltage is maintained constant. , In addition, the re-arc characteristics in the event of arc breakage are also improved, and an even greater advantage is that
The current at the time of contact between the wire 3 and the base material 4 at the time of arc start is large, and the arc start becomes good.
Furthermore, if the input/output characteristics of the voltage converter 15 are set as shown by the broken line in FIG. It can be changed depending on the reference position. on the other hand,
The two sets of feedback control system reference signals outputted from the output regulator 6 are converted by the signal converter 11 into signals with a constant ratio as shown by the solid line in FIG. 2 mentioned above, and then input to the adder 19. A detection signal from the voltage detector 17 that detects the output voltage of the output control section 2, that is, the welding voltage, is input to the other input terminal of the adder 19.
At 9, the reference signal of the signal converter 11 and the detection signal of the voltage detector 17 are added, and this added output is sent to the second comparator amplifier 12 as a command signal that becomes a control reference for the feedback control system of the motor control section 9. is input.

Therefore, when the arc length becomes shorter and the welding voltage decreases, the detection signal of the voltage detector 17 and the command signal of the adder 19 become smaller, and the motor control section 9 is feedback-controlled based on this reduced command signal. ,
As a result, the output voltage of the motor control unit 9 becomes low, the rotational speed of the wire feeding motor 0 becomes small, and the wire 3
The feeding speed is decreased by 4.0 mm, the arc length is lengthened, the welding voltage is increased, and feedback control is performed so that the arc length becomes a predetermined length. Conversely, when the welding voltage becomes high, for example, when the torch T is moved in the direction of the arrow from the position indicated by the one-point silver line in FIG. When the arc length becomes longer due to the stepped portion 4'' and the welding voltage becomes higher, both the detector signal of the voltage detector 7 and the command signal of the adder 19 become larger. The output voltage of the wire feeding motor 0 is controlled to be high, the rotational operation of the wire feeding motor 0 is increased, the feeding speed of the wire 3 is increased, the arc length is shortened, and the wire is returned to the one point training position 11. In addition, by operating the detection signal characteristic adjuster 18, the ratio of the detection signal to the detection voltage in the voltage detector 17 is varied, the command signal of the adder 19 is varied, and the wire 3
The feeding amount per hour can be varied, and the position of the one-dot solid line in FIG. 6 can be adjusted. In the above embodiment, the input/output characteristics of the signal converter 11 were set as shown by the solid line in FIG. 2, but as the set current of the output compensator 6 increases, the feeding speed of the wire 3 increases If necessary, the signal converter 11 may be configured with a well-known two-way circuit consisting of a transistor or a diode and an operational amplifier, and the input/output characteristics of the signal converter 11 may be made as shown by the dotted line in FIG.

As described above, the arc welding machine of the present invention includes an output control section that controls and rectifies an AC input and outputs it, a current detector that detects the output current of the output control section, and a current detector that detects the output current of the output control section. a first comparator amplifier that compares and amplifies the output with the output of an output regulator that adjusts the output current of the output control section; and a first comparator amplifier that is connected in parallel to the first comparator amplifier and adjusts the output of the output regulator to a predetermined voltage. a voltage converter for converting the voltage; a first phase shifter for controlling the phase of the control rectifying element of the output control section according to the output of the voltage converter or the output of the first comparison amplifier; a motor control unit that controls driving; a signal converter that converts the output signal of the output regulator into a signal at a fixed ratio and outputs the signal; and an addition that adds the output of the signal converter and the output of the voltage detector. a second comparator amplifier that compares and amplifies the output signal of the adder and a detection signal obtained by detecting the output voltage of the motor control unit; and control of the motor control unit based on the output of the second comparator amplifier. By being equipped with a second phase shifter that controls the phase of the rectifying element, the wire feeding speed can be varied in response to changes in the welding voltage due to changes in the arc length, and can be maintained constant with the arc length. Uniform welding can be performed even when there is a stepped portion.

Furthermore, since the reference signal for the feedback control system that keeps the welding current constant and the reference signal for the feedback control system that keeps the wire feeding speed constant can be set with one output regulator, operability is good. In addition, "When the welding voltage becomes low, it is possible to shift from constant current control to quasi-constant voltage control or constant voltage control, so it is possible to maintain a large current due to contact between the wire and the base metal during arc heating. The arc start characteristics become good, and the re-arc start characteristics also become good.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the secondary arc welding machine, Figure 2 is a diagram of the relationship between the input voltage and output voltage of the signal converter in Figure 1, and Figure 3 is a diagram of the relationship between the input voltage and output voltage of the signal converter in Figure 1.
The figure is an explanatory diagram of welding a welded part having a stepped part using the arc welding machine shown in Fig. 1. Fig. 4 and the following show one embodiment of the arc welding machine of the present invention. Fig. 4 is a block diagram; Figure 5 is a diagram of the relationship between the input voltage and output voltage of the voltage converter, Figure 6 is a diagram of the relationship between the output current and output voltage of the output control section, and Figure 7 is an explanatory diagram when welding a welded part with a step. It is. 2... Output control section, 2'... Control rectifier, 3... Wire, 5... Current detector,
6... Output regulator, 7... First comparison amplifier, 8... First phase shifter, 9... Motor control unit, 10...・・Wire feeding motor, 11・・
...Signal converter, 12...Second comparison amplifier, 13...Second phase shifter, 15...
Voltage converter, 17... Voltage detector, 19...
...adder. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] 1. An output control unit that performs controlled rectification of AC input and outputs the output, a current detector that detects the output current of the output control unit, and an output regulator that adjusts the output of the current detector and the output current of the output control unit. a first comparison amplifier that compares and amplifies the output of the
a voltage converter connected in parallel to the first comparison amplifier and converting the output of the output regulator into a predetermined voltage; and controlling the output control unit by the output of the voltage converter or the output of the first comparison amplifier. a first phase shifter that controls the phase of the rectifying element; a motor control section that controls the drive of the wire feeding motor; and a signal converter that converts the output signal of the output regulator into a signal at a fixed ratio and outputs the signal. an adder that adds the output of the signal converter and the output of the voltage detector; and a second adder that compares and amplifies the output signal of the adder and a detection signal that detects the output voltage of the motor control unit. An arc welding machine comprising: a comparison amplifier; and a second phase shifter that controls the phase of a control rectifying element of the motor control section based on the output of the second comparison amplifier.