JPS61186168A - Tig pulse welder - Google Patents

Abstract

PURPOSE:To regulate the output current waveform of TIG pulse welder by providing the slope control part to vary the reference voltage level in slope shape at the change-over time of the reference voltage for pulse current setting and the reference voltage for base current setting. CONSTITUTION:A slope control part 12 is provided between change-over switches 7a, 7b of a pulse, base time control part 10 and errors amplifier 6. The reference voltage V3 varies in slope shape when the reference voltage V1 for pulse current setting and the reference voltage V2 for base current setting which are changed over alternately by the time set by the switches 7a, 7b are impressed on the control part 12. Accordingly the outputs of the amplifier 6 and output control part 3 are similarly changed and the output currents IP, IB of the transformer 2 for welding become in the pulse waveform of slope shape. The pulse TIG welder having the pulse current waveform of slope shape is thus obtd.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to TIG pulse welding, which is equipped with a current feedback control function that periodically changes the output current into a pulse current and a base current in order to control the heat input to the welding part. Regarding machines.

[Background of the Invention] FIG. 4 shows a control block diagram of a conventional TIG pulse welding machine, and FIG. 5 shows the waveforms of the reference voltage for current control and the output current.

In FIG. 4, an AC input from an input terminal 1 is applied as a voltage necessary for welding by a welding transformer 2 to an output control unit 3 that can switch between AC and DC, which is configured by control elements such as thyristors. The output current passes through the welding current detection section 4 and is supplied to the load from the output terminal 5. The output current of the output control section 3 is converted into a voltage proportional to the output current value by the welding current detection section 4, and is applied to one input terminal of the error amplifier 6 as a current feedback signal 4. error amplifier 6
When performing TIG pulse welding, this reference voltage V is applied to the other input terminal of the switch 7a, 7b of the pulse and base time control section 10.
The reference voltage V for pulse current setting from the reference voltage source 8 is
□ and reference voltage v2 for base current setting from reference voltage source 9
It is switched alternately at the set time. Then, the difference signal between this reference voltage V and the current feedback signal 4 is amplified by the error amplifier 6 and added to the phase shifter 11 for firing the thyristor, and the thyristor of the output control section 3 is controlled in phase. Current feedback control is performed so that the output current changes periodically into a pulse current and a base current.

In a TIG pulse welding machine using such a current feedback control system, the reference voltage V applied to the error amplifier 6
As shown in FIG. 5(a), the level changes rapidly from V□ to v2 and from ■2 to vl at pulse time tp and base time ta. The output of the error amplifier 6 changes in accordance with the change in the reference voltage v3, and in response to this, the output control section 3 controls the output current to increase or decrease. Since the change in the output current is delayed, the reference voltage applied to the error amplifier 6,
A time lag occurs between the current feedback signal v4 and the current feedback signal v4.

As a result, the output current waveform becomes as shown in Fig. 5 (b) and (c), and when switching from the base current IB to the pulse current IP, an overshoot portion A occurs, and conversely, from the pulse current IP to the base current IS When switching to , an undershoot portion B occurs. This phenomenon becomes more pronounced as the difference between the pulse and base currents increases.

When welding with a current with such a pulse waveform, (1)
The strong arc force at the overshoot portion A causes the molten pool to ripple, making the undulations of the bead uneven and deteriorating the appearance of the bead.

(2) In welding work using a filler rod, the strong arc force at the overshoot part A makes it difficult to insert the filler rod, making it difficult to penetrate the weld smoothly11.

(3) Electrodes wear out quickly due to large current.

(4) If the level difference between the pulse and base currents is large, arc breakage is likely to occur at the undershoot portion B.

Problems such as this occur.

[Object of the Invention] An object of the present invention is to solve the problems of the prior art described above, improve welding workability and welding quality of TIG pulse welding, and reduce electrode wear.

[Summary of the Invention] The present invention includes a welding current detection section, an error amplifier that amplifies a difference signal between a current feedback signal from the detection section and a reference voltage, and an output control section operated by the output of the amplifier. The pulse current setting base f! at the time when the reference voltage is set by the switch. ! In a tick pulse welding machine, the voltage and the reference voltage for setting the base current are alternately switched to periodically change the output current into the pulse current and the base current, and the reference voltage for controlling the pulse current and the reference voltage for setting the base current are alternately switched. The present invention is characterized in that it includes a slope control section that changes the reference voltage level in a slope shape when switching from the reference voltage.

[Embodiment of the Invention] Fig. 1 shows a control block diagram of an embodiment of the invention, Fig. 2 shows a circuit example of the slope control section, and Fig. 3 shows the waveforms of the reference voltage for current control and the output current. .

In Fig. 1, 1 to 11 are parts corresponding to Fig. 4,
The basic configuration of the control system is the same as the conventional example shown in Figure 4, but
In the present invention, a slope control section 12 is provided between the changeover switches 7a and 7b and the error amplifier 6, and the slope control section 12 is used for pulse current setting which is alternately switched at the time set by the changeover switches 7a and 7b of the pulse and base time control section 10. The slope control unit 12 controls the reference voltage V and the base current setting reference voltage v2.
This differs from the conventional example in that the reference voltage level is changed in a slope shape when switching between the pulse and base reference voltages.

For example, as shown in FIG. 2, the slope control unit 12 includes resistors R□ and R2 that divide the pulses and base reference voltages vi and v2 applied via the changeover switches 7a and 7b, and a slope fast/fast selector for the resistor R2. Comprising capacitors C1, C2, and C3 connected in parallel via a switch 13, and a resistor R2.
The terminal voltage is applied to the error amplifier 6 as a reference voltage v3.

This slope control section 12 controls the voltage level of the reference voltage V when switching between the pulse and base reference voltages V2 and V2 in a slope shape according to the time constant of the resistors R1 and R2 and the capacitor selected by the slope adjustment switch 13. Changes to

Here, if the capacitor capacity is C□<C2 × C3, then C
Depending on which of □, C2, or C1 is selected, the degree of slowness of the slope change of the reference voltage □ is determined by a in Figure 3 (A).
, b, c.

Since the output of the error amplifier 6 similarly changes according to the level change of the reference voltage V, by controlling the phase of the thyristor of the output control section 3 via the phase shifter 11, the output current can also be changed as shown in FIG. As shown in (b) and (c), the base current I
The pulse waveform changes in a slope from B to pulse current IP, and from pulse current IP to base current IB.

This slope change in output current is caused by capacitors C1 and C
, , Figure 3 (b) and (c) depending on which of C3 is selected.
a′.

b', C'.

In other words, if the reference voltage level is changed in a slope shape when switching between the pulse and base reference voltages V2 and 2, the output current will change due to a delay in the change in the output current, as in the case where the reference voltage level is suddenly changed. There is no overshoot or undershoot of the output current, and the output current is equal to the base current I.
There is a gradual change from Q to pulse current IP, and from pulse current IP to base current IQ.

The degree of speed of this current change can be selected depending on the material of the object to be welded, the shape of the joint, the appearance of the bead, etc. using the slope slope selection switch (3).

The slope control of the reference voltage described above can also be performed using an integrator.

[Effects of the Invention] The present invention is characterized in that an output current waveform that changes in a slope shape without overshoot or undershoot can be obtained when switching between pulse and base current without reducing the responsiveness of the control system to disturbances. Yes, from base current to pulse current.

The current change from the pulse current to the base current is gradual, there is no overshoot or undershoot, and the arc is soft, making it possible to obtain a clean bead with uniform waves, and it is also easy to insert the filler rod, resulting in smooth welding. able to work,
Welding workability and welding quality are improved by eliminating arc breakage even when there is a large level difference between the pulse and base currents, and electrode wear can also be reduced because excessive current due to overshoot is eliminated.

[Brief explanation of drawings]

FIG. 1 is a control block diagram showing one embodiment of the present invention, and FIG.
The figure is a circuit diagram of the slope control section in FIG. 1. Figures 3 (A), (B), and (C) are waveform diagrams of the reference voltage and output current, and Figure 4 is a control block diagram of the conventional example. FIGS. 5(a), (b), and (c) are waveform diagrams of the reference voltage and output current. 3... Output control section 4... Welding current detection section 6
...Error amplifier 7a, 7b...Selector switch 12...Slope control section vl...Reference voltage for pulse current setting v2...Reference voltage for base current setting v3...Reference voltage

Claims (1)

[Claims] It has a welding current detection section, an error amplifier that amplifies a difference signal between a current feedback signal from the detection section and a reference voltage, and an output control section operated by the output of the amplifier, and the reference voltage is set by a changeover switch. In a TIG pulse welding machine, the reference voltage for setting the pulse current and the reference voltage for setting the base current are alternately switched over time to periodically change the output current to the pulse current and the base current. A TIG pulse welding machine characterized by comprising a slope control section that changes the reference voltage level in a slope shape when switching between the voltage and the reference voltage for setting the base current.