JPH04309466A - Consumable electrode type arc welding power source unit - Google Patents

Abstract

PURPOSE:To obtain the consumable electrode type arc welding power source unit which can execute welding with high quality and with high work efficiency by adjusting automatically a welding output in accordance with a variation of a distance (wire extension) between a welding base metal which is being welded and an electric conduction electrode. CONSTITUTION:From a welding voltage value detected by a voltage detecting part 16, a short circuit state is detected in a short circuit detecting part 21, and also, a time setting part 20 for the purpose of eliminating the first stage of a short circuit being a period in which a resistance value is not proportional to the wire extension since a necking part is generated between a molten pool and a wire is provided, and by providing a current control, part 17, a short circuit current is controlled to a prescribed value in a period containing the time set by the time setting part 20, and also, an output adjusting part 19 for adjusting a welding output in accordance with a voltage value in its period is provided, by which in accordance with the wire extension, the welding output is adjusted automatically.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a consumable electrode type arc welding power supply device that automatically adjusts welding output in accordance with changes in the distance between a welding base material and a current-carrying electrode (hereinafter referred to as protrusion length).

0002

[Prior art] C as a representative of the consumable electrode type arc welding method
The O2 welding method will be explained as an example. In this CO2 welding method, the protrusion length is normally set to 10 to 20 mm. However, when welding structures with complex shapes or large structures, the tip of the welding torch may not be able to approach the welding location, such as when welding a narrow gap or a narrow part. In such a case, welding is unavoidably performed with a long protrusion length, and the protrusion length may be about 50 mm.

[0003] When the protrusion length becomes long, the arc becomes unstable, and as a result, the bead breaks, resulting in poor bonding at that part, and even if the bead does not break, the bead width becomes uneven and the average bead width becomes small. As a result, the margin for aiming at the weld line becomes extremely small.

[0004] In order to prevent such adverse effects on the welding results and working conditions, when welding with a long protrusion length, the output is adjusted so that the welding voltage is higher than usual, for example. However, in such a state where the output of a high welding voltage is adjusted, if the protrusion length is short, troubles such as the wire being fused to the current-carrying electrode occur. Therefore, it was necessary to readjust the output every time the protrusion length changed.

[0005]

[Problem to be Solved by the Invention] In order to adjust the output as described above, in semi-automatic welding, it is necessary to stop welding each time, which not only makes the welding work extremely complicated and inefficient, but also reduces the welding process. Quality problems also occur. Furthermore, it is extremely difficult to externally measure the protrusion length currently being welded or the protrusion length for the next weld, and output adjustment must therefore be done through trial and error, increasing problems in work efficiency. , There is also the problem of deterioration of welding quality due to poor adjustment.

[0006] The present invention aims to solve the above-mentioned problems and achieves improvements in welding work efficiency and welding quality by automatically calculating the protrusion length during welding and automatically adjusting the output accordingly. The object of the present invention is to provide a consumable electrode type arc welding power supply device.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the consumable electrode type arc welding power supply device according to the present invention includes a voltage detecting section for detecting welding voltage, and a preset value for the output of the voltage detecting section. A short-circuit detection section that detects a short-circuit condition by comparing it with a reference voltage, and a time period that receives the output of the short-circuit detection section and outputs a signal after the set time has elapsed if the short-circuit condition continues for the set time from the start of the short circuit occurrence. a setting section; a current control section that controls the short-circuit current to a constant value during a period including at least the signal output period of the time setting section; and an output that adjusts the output based on the output of the voltage detection section at the time when the time setting section outputs the signal. It is composed of an adjustment section.

[0008]

[Operation] The principle of calculating the protrusion length according to the present invention will be explained with reference to FIG. FIG. 3(a) is a schematic diagram of a welded part in a state where an arc is generated during welding. Also, Figure 3
(b) and (c) are schematic diagrams of a welded part in a short-circuit state, and an arc state and a short-circuit state occur alternately during welding. The protrusion length e is the distance between the current-carrying electrode 1 and the welding base material 4. In FIG. 3(a), the wire portion 2, which is a portion constituting the protrusion length, and the arc portion 3, which is the other portion, have greatly different characteristics as a conductor portion. That is, while the wire portion is a pure resistor, the arc portion is a conductor portion having a constant potential gradient as shown by the following equation.

va=α+Xea In the above equation, va is the voltage drop at the arc portion, X is the potential gradient of the arc column, ea is the length of the arc portion, and α is a constant.

However, since va in the above equation cannot be measured, the relationship between measurable welding voltage v, welding current i, and protrusion length e is derived from the following equation, assuming v=va+vw, e=ea+ew. .

v=α+Xea+βiew=α+(X−β
i) ea+βie In this formula, vw is the voltage drop in the wire portion, ew is the length of the wire portion, and β is the average resistance value per unit length of the wire. Here, the length ea of the arc part is not constant and changes with time, so in order to calculate the protrusion length e, it is necessary to measure the length ea of the arc part by some means in addition to the welding voltage and welding current. However, it is difficult to install sensors externally due to restrictions such as interfering with welding work. Note that βiew in the above equation indicates the voltage drop value of the wire portion 2.

On the other hand, in the short-circuited state shown in FIG. 3(b), the entire protrusion length is occupied by the wire portion 2, so the following relationship is obtained.

v=vw=βiew=βieUsing this relationship and assuming that the current is a known constant value, the protrusion length e can be easily calculated by measuring the voltage.

In this way, in the present invention, the protrusion length is calculated from the voltage during the short circuit period when a known constant current flows, but as shown in FIG. 3(c), in the initial stage of the short circuit, the droplet and The contact area of the base material 4 with the molten pool 5 is extremely small, resulting in a so-called constriction 6. Therefore, this part has a high resistance and the protrusion length is calculated as a larger value than the actual value, so it is excluded from the calculation during this period.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the consumable electrode type arc welding power supply device of the present invention will be described below with reference to the drawings.

In FIG. 1, 10 is a power transistor for output adjustment, 11 is a welding transformer, 12 is a secondary rectifier, 13 is a current detection section for detecting the welding current, and 14 is a welding device whose details are shown in FIG. part, 15 is the base material to be welded, 16
is a voltage detection section, 17 is a current control section, 18 is an output control section,
19 is an output adjustment section, 20 is a time setting section, 21 is a short circuit detection section, 22 is a reference voltage generation section, 23 is a voltage value holding section, 24
25 is a shunt for detecting the welding current, and 25 is an analog switch for selecting the voltage input to the voltage value holding section 23.

The operation of the consumable electrode type arc welding power supply device constructed as described above will be explained below.

First, the voltage value applied to the welded portion 14 is detected by the voltage detection section 16. The reference voltage generation unit 22 generates a reference voltage signal that serves as a criterion for determining whether a short circuit state or an arc state exists. The short circuit detection section 21 determines whether the current state of the weld is a short circuit or an arc by comparing the reference voltage signal of the reference voltage generation section 22 and the voltage value of the weld section inputted from the voltage detection section 16. The time setting section 20 starts measuring time in response to the short circuit start signal from the short circuit detection section 21 and continues the measurement during the period of the short circuit state, but outputs a pulse signal when the measured value reaches a preset value. Further, since the measured value is reset by the arc start signal, if the short circuit ends before reaching the set value, no pulse signal will be output. In this way, the time setting section 20 has a function of outputting a signal after a certain period of time regarding a short circuit that continues for a certain period of time or more. Therefore, the voltage value holding section 23 receives only the voltage value at the time of short circuit selected by the time setting section 20 from the voltage detecting section 16 . The voltage value holding section 23 has a function of holding and outputting the previous input signal value until a new input signal is received. The output adjustment section 19 outputs the adjustment amount of the welding output according to the signal from the voltage value holding section 23 to the output control section 18 that controls the welding output.

Further, the current control section 17 performs current control during the short circuit period, and outputs a signal to the output control section 18 so that the short circuit current waveform detected by the current detection section matches the model current waveform set internally. It has a feedback control function. FIG. 2 is a schematic diagram of an example of a model current waveform from the start of the short circuit to the end of the short circuit in the current control section 17. In FIG. 2(a), waveform portions (1) and (3) are waveforms determined from the viewpoint of suppressing the amount of spatter generation and ensuring arc stability by quickly releasing the short-circuit condition. Therefore, the type of shielding gas, It varies depending on construction parameters such as wire diameter and wire feed amount. On the other hand, the waveform portion (2) is a portion that outputs a constant current value that is not dependent on the construction parameters during the period T that includes the pulse signal period of the time setting section 20 described above. Therefore, the voltage value corresponding to the protrusion length is input to the voltage value holding unit 23 as a value that is not dependent on the construction parameters. In addition, in FIG. 2(b), which is another example of the model current waveform, the current levels of waveform parts (4), (5), and (6) are the same as those in (1) and (3) of FIG. 2(a). Waveform part (5) that includes period T, depending on the parameters
is a known constant current value. Therefore, the input to the voltage value holding section 23 is a value that depends on the construction parameters, but by combining it with the signal from the current control section 17 in the output control section 18, control corresponding to the protrusion length can be performed.

In this way, by measuring the voltage value under the condition that the current value is constant, the welding output is automatically adjusted in accordance with the protrusion length.

[0021]

[Effects of the Invention] As described above, according to the present invention, the overhang length can be represented by the voltage value under the condition that the current value is constant in a short circuit that continues for a certain time or more, and the welding output can be determined from the voltage value. Can be adjusted automatically. This eliminates the need for the operator to readjust the output each time welding when the overhang length fluctuates, and also eliminates the problem of welding quality deteriorating due to poor output adjustment and the need to suspend welding temporarily to readjust the output. Therefore, it is possible to prevent welding quality from deteriorating due to such problems, and it is possible to efficiently weld complex-shaped structures and large-sized structures.

[Brief explanation of drawings]

[Fig. 1] A block diagram of an embodiment of the consumable electrode type arc welding power supply device of the present invention.

FIG. 2(a) is a schematic diagram showing an example of a model current waveform of the current controller 17; FIG. 2(b) is a schematic diagram showing another example of the model current waveform of the current controller 17;

[Figure 3] (a) is a schematic diagram of a welded area where an arc is generated during welding (b) is a schematic diagram of a welded area where the wire is short-circuited to the base metal (c) is a schematic diagram of the welded area where the wire is short-circuited to the base metal Schematic diagram of the weld in other conditions

[Explanation of symbols] 16 Voltage detection section 17 Current control section 19 Output adjustment section 20 Time setting section 21 Short circuit detection section

Claims (1)

[Claims] [Claim 1] A voltage detection section that detects welding voltage, a short circuit detection section that detects a short circuit state by comparing the output of the voltage detection section and a preset reference voltage, and an output of the short circuit detection section. a time setting section that outputs a signal after the set time has elapsed if the short circuit state continues for a set time from the start of the short circuit occurrence; and a time setting section that controls the short circuit current to a constant value during a period that includes at least the signal output period of the time setting section. A consumable electrode type arc welding power supply device comprising: a current control section that adjusts a welding output based on the output of a voltage detection section at the time when a signal from a time setting section is output;