JPS6247108B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pulse arc welding machine, and more particularly to a pulse arc welding machine that can automatically track and weld irregularities on a base metal surface.

Conventionally, when welding with a pulse arc welder,
There was no means to directly detect the position of the welding torch, that is, the distance from the molten pool of the workpiece (base metal) to the welding torch. Therefore, when welding something with a complicated shape (for example, something like the one shown in FIG. 5), it was necessary to resort to manual welding by holding a welding torch in one's hand. However, when performing manual welding, the welding torch must be moved smoothly and at a constant speed according to the shape of the base metal, which requires highly skilled workers.

The purpose of this invention is to eliminate the drawbacks of the conventional device described above.The present invention detects the arc length, that is, the variation in the distance between the wire electrode and the base metal using the arc discharge voltage (hereinafter referred to as welding voltage), and uses this detected value and the above-mentioned Standard welding voltage value when the arc length is the preset standard length
The amount of variation is calculated by comparing with V ₀ , and the amount of charge of the pulsed current is adjusted in the direction in which the detected value approaches V ₀ using this amount of variation, so that the arc length maintains the reference length. , detects the amount of charge Q of the pulse current, and moves the welding torch back and forth so that the detected amount of charge Q becomes a reference charge amount Q ₀ corresponding to the distance from the welding point of the base material to the welding torch set in advance. By doing so, the distance from the welding point of the base metal to the welding torch is maintained at a predetermined value, thereby making the welding apparatus unmanned.

Note that, as shown in FIG. 2, the amount of charge Q of the pulse current is expressed as the product of the peak value Ip of the pulse current and the pulse width τ. In other words, the amount of charge Q corresponds to the area of the pulse current waveform, or in other words, corresponds to the average value of the welding current.

An embodiment of this invention will be described below.

FIG. 1 is a block diagram of an embodiment of this invention.
In this example, the peak value of the pulse current is kept constant, and the amount of charge Q is adjusted by changing the pulse width τ.

In the figure, 1 is a DC power supply circuit, 2 is a switch group, 3 is a control circuit for controlling conduction of switch group 2,
4 is an auxiliary power supply that supplies an arc sustaining current (hereinafter referred to as base current); 51 and 52 are flywheel diodes; 61 and 62 are reactors; 7 is a welding wire winding frame; and 8 is a welding wire that is fed in the direction of arrow A. 9 is a welding torch, and a shielding gas is supplied from a shielding gas supply device (not shown) to insulate the arc discharge portion formed between the wire electrode 10 and the base material 11 from air. 12 is a voltage detector that detects the arc voltage Va (hereinafter referred to as welding voltage) between the wire electrode 10 and the base material 11; 13 is a current detector that detects the welding current Ia; and 14 is the welding torch 9 connected to the base material 11. 15 is an operation panel that includes a welding current setting device 16a for setting a reference welding current _I0 , and a welding current setting device 16a for setting a reference welding current I0;
It has a welding voltage setting device 16b for setting V ₀ . The controller 3 also includes a base current setting device 16 that sets the base current I _B supplied from the auxiliary power source 4.
b. A pulse frequency setter 18 that receives a reference welding current _I0 and sends out a pulse current frequency signal f; a pulse peak current value setter 19 that sets a peak value Ipo of the pulse current; a reference welding voltage Vo and a welding voltage Va;
The comparator 20 outputs a difference signal Vs (=Vo−Va), sets the reference pulse width τo of the pulse current, and receives the difference signal Vs and outputs a correction signal τ
s, and the corrected pulse width signal τ (=τo
+τs), a pulse width setting circuit 21 that sends out a pulse frequency command signal f, a peak value signal Ipo,
It is comprised of a switch command device 22 which controls conduction of the switch element group 2 in response to a pulse width signal τ and operates to supply a pulse current having a commanded peak value and pulse width at a frequency f. 23 is a wire feed speed control device that receives a reference welding current signal Io and sends out a welding wire feed speed signal V that matches this current value to drive the feed motor 8; 24 is a welding current
A pulse width detector 25 detects the width τa of the pulse current in the welding current Ia from Ia, and when the distance from the welding point of the base metal to the welding torch is set, the distance is maintained to ensure a stable welding condition. A reference pulse width setter 26 is a comparator that sends out the pulse width τo necessary for sustaining the pulse width, and a comparator 26 compares the pulse width signal τa of the pulse width detector 24 with the reference pulse width signal τo of the reference pulse width setter 25. and the difference signal Q ₁ (=τa
-τo). Upon receiving the signal _Q1, the torch position control device 15 moves the welding torch away from the base metal 11, depending on whether _the signal _Q1 is positive or negative and its magnitude _or small. When it is negative, the drive is controlled so that it moves forward and backward toward the base material 11.

Note that the detected welding current Ia is
2, and the peak value of Ia is controlled to be equal to Io.

Next, the operation of this embodiment will be explained.

First, a reference welding current value Io, a reference welding voltage Vo, a base current I _B , a pulse peak value Ipo, and a pulse width τo are determined from a combination of the plate thickness and material of the base material 11, the type of shielding gas, the diameter of the wire electrode 10, etc. , respectively. With this setting operation, this welding machine can set the wire feeding speed V, the welding torch tip 9
The arc length at this time is the set distance Lo between a and the base metal, the base current I _B of the welding current (hereinafter referred to as the set distance of the welding torch), the peak value Ipo of the pulse current, the pulse width τo, and the pulse frequency f. la=lo, welding voltage Va=Vo, and welding current Ia=Io.

Now, suppose that the distance La between the base metal and the tip of the welding torch (hereinafter referred to as welding torch distance) becomes La>Lo due to the uneven surface shape of the base metal 11, and as a result, the arc length la becomes la>lo. , Va>Vo. This Va is detected by the voltage detector 12 and input to the comparator 20. The comparator 20 compares the reference welding voltage Vo and the welding voltage Va, and produces a difference signal Vs (=
Vo−Va), that is, a negative signal is output as the difference signal Vs. The pulse width setter 21 inputs this difference signal Vs, calculates a correction signal τs, and outputs a pulse width signal τ
(=τo+τs) is output. Now, since Vs is negative, τs proportional to Vs also becomes negative, and the pulse width τ becomes smaller than the reference pulse width τo. This pulse width signal τ is sent to the switch element group 2, and the pulse width of the pulse current flowing between the wire electrode 10 and the base material 11 is set to τ (τ<τo). As the current pulse width becomes smaller, the droplet transfer speed of the wire electrode becomes smaller, but since the wire feeding speed V is constant, the amount of protrusion of the wire electrode increases, and the arc length la decreases. It is quickly corrected in the direction of decreasing, and stabilizes at the pulse width τa of the pulse current where the arc length la=lo. The state at this time is shown in FIG. The pulse width τa of this modified pulse current
is detected by the pulse width detector 24, and since this pulse width τa satisfies τa<τo, that is, the amount of charge Q
has decreased. Difference signal Q ₁ of comparator 26
(=τa - τo) is negative. Therefore, upon receiving this difference signal Q ₁ , the torch position control device 14 moves the welding torch 9 closer to the base metal 11 until the difference signal Q ₁ becomes zero, that is, τa = τo.

In addition, when the welding torch distance La becomes La<Lo due to the unevenness of the surface shape of the base material 11, this device is operated in the opposite direction to the above case, that is, the pulse width τa is
a>τo, then the difference signal _Q1 becomes positive, and the torch position control device 14 moves the welding torch 9 away from the base metal until the difference signal _Q1 becomes zero, that is, τa=τo. Drive it until it becomes .

Figure 4 is a characteristic diagram showing the actual measurement results of the pulse width τo that maintains the optimum arc length lo and a stable welding state when the welding torch setting distance Lo is set appropriately. The wire is
Comparison steel of 1.2mmφ, shielding gas is Ar/Co ₂ =8/
2, the mixed gas, wire feeding speed V, and pulse frequency f are constant values determined by the welding current Io,
The pulse peak current value Ipo was set to a constant value of 400A, which is sufficient for spray transfer. As can be seen from this characteristic diagram, when the welding torch distance La was set to 3 cm, τa = 2.8 ms, when it was set to 2 cm, τa = 3.3 ms, and when it was set to 1 cm, τa = 4 ms. Set distance Lo to 2cm
In the case of
If deviates from τo (=3.3ms), the torch position control device moves the welding torch from τa to τ as described above.
If controlled in the direction of o, the arc length will always be maintained at lo, and the welding torch distance will be maintained at lo, as shown in Figure 5, while welding can be performed along the unevenness of the base metal surface, resulting in good welding. You can get beads.

In the above embodiment, the width τa of the pulse current is detected by the welding current detected by the current detector 13.
Although it is detected from Ia, it may be detected from welding voltage Va.

Furthermore, in the above embodiment, the amount of charge supplied to the wire electrode is changed by keeping the peak value constant and changing the pulse current width τ, but the peak value of the pulse current may be changed.

FIG. 6 is a block diagram of an example of this configuration, and FIG. 7 is a characteristic diagram showing the relationship between Ipo and Lo under the experimental conditions of the characteristic diagram shown in FIG. 4, with τo constant. 191 is a pulse peak current estimator, which calculates a preset reference pulse peak value Ipo,
The pulse peak value Ip is corrected by calculating the correction value Ips according to the output signal Vs (=Va−Vo) of the comparator 20.
(=Ipo+Ips) to correct the pulse peak value Ip. 241 is a pulse peak current value detector; 2
51 is the seventh line corresponding to the set distance Lo of the welding torch.
A reference pulse peak current setter 26 outputs the reference peak value signal Ipo shown in the figure, and a comparator 26 compares the detection signal Ipa of the pulse peak current detector 241 with the reference peak value signal Ipo, and outputs a difference signal Q ₂ ( =Ipa−
Ipo). The torch position control device 14 that receives the difference signal Q ₂ controls the welding torch to move forward or backward relative to the base material in the direction where the difference signal Q ₂ becomes zero, depending on whether the difference signal Q ₂ is positive or negative. . In this way, the arc length lo is maintained as in the previous embodiment, and at the same time, the position of the welding torch 9 is controlled so as to maintain the set distance Lo.

In the above embodiment, a configuration in which the welding torch is moved is shown, but it goes without saying that a configuration in which the base metal side is moved may also be used.

As described above, the device of the present invention supplies an arc current consisting of a base current and a pulse current that can be superimposed on the base current between the wire electrode and the base material, and melts the wire electrode. In a pulse arc welding machine that welds base metal with droplets, there is a welding torch that holds a welding wire that is placed opposite to the base metal and is fed at a predetermined speed toward the base metal, and a A voltage detector detects the welding voltage Va detected by the voltage detector, and a welding voltage Va detected by the voltage detector.
and a preset reference voltage Vo.
A comparator, a pulse width or pulse peak current setting device that changes and sets the pulse width or pulse peak current value of the pulse current according to the output from the first comparator, and a pulse width or pulse peak current setting device that changes and sets the pulse width or pulse peak current value. a second comparator that compares the preset pulse width or pulse peak current value with a preset reference pulse width or reference pulse peak current value; The welding torch is equipped with a control device that controls the relative distance, so even when welding base metals whose shapes have changed significantly, the welding torch automatically moves up and down according to the shape of the base metal to always maintain the optimal This has the effect of allowing welding to be performed at a suitable welding torch position.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a schematic diagram showing the welding current waveform of this embodiment,
Fig. 3 is an enlarged schematic diagram of the arc portion between the welding torch and the base metal, and Fig. 4 shows the width τa of the pulse current and the welding torch distance La when the peak current value Ipo of the pulse current in this embodiment is constant. FIG. 5 is a diagram showing the relationship between the shape of the base material of the welding machine to which this invention is applied and the movement trajectory of the welding torch, and FIG. 6 is a diagram showing the configuration of another embodiment of the invention. FIG. 7 is a characteristic diagram showing the relationship between the pulse peak current Ipa and the welding torch distance La when the pulse current width τo of this embodiment is constant. In the figure, 1 is a DC power supply circuit, 2 is a switch element group, 3 is a control device, 4 is an auxiliary power supply, 51, 5
2 is a flywheel diode, 61 and 62 are DC reactors, 8 is a wire feed motor, 9 is a welding torch, 9a is a chip, 10 is a wire electrode 11 is a base material, 12 is a voltage detector, 13 is a current detector, 1
4 is a torch position control device, 15 is an operation panel, 16a
is a welding current dial, 16b is a welding voltage dial, is a switch command circuit, 17 is a base current setter, 18 is a pulse frequency setter, 19 and 191 are pulse peak current value setters, 20 is a comparator, 21
is a pulse width setting device, 22 is a switch command device, 23
24 is a pulse width detector, 241 is a pulse peak current value detector, 25 is a reference pulse width setter, and 251 is a reference pulse peak current setter. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. An arc current consisting of a base current and a pulse current that can be superimposed on the base current is supplied between the wire electrode fed toward the base metal and the base metal, and the base metal is welded with the droplets of the wire electrode. In the pulse arc welding machine, a welding torch that is arranged opposite to the base metal and holds a welding wire that is fed at a predetermined speed toward the base metal, and a welding voltage Va that is applied between the wire electrode and the base metal. a first comparator that compares the welding voltage Va detected by the voltage detector with a preset reference voltage Vo; and a voltage detector that detects the welding voltage Va detected by the voltage detector and a preset reference voltage Vo; A pulse width or pulse peak current setting device for changing and setting the current pulse width or pulse peak current value, and a preset standard for the pulse width or pulse peak current value changed and set by the pulse width or pulse peak current setting device. A second comparator that compares the pulse width or a reference pulse peak current value, and a control device that controls the relative distance between the welding torch and the base metal according to the output from the second comparator. Characteristic pulse arc welding machine.