JPS60250875A - Power source for welding - Google Patents

Abstract

PURPOSE:To execute smoothly a spray shift after concentrating a welding arc, and to prevent a magnetic blow arc instability by decreasing gradually a base current value from a pulse current value, in case of an alternate supply wire feed welding of a pulse current and a base current. CONSTITUTION:A reference clock circuit 15 outputs an H level and L level signal Vck of a pulse period If and a pulse width (tp) to a pulse controlling circuit 16 by a welding output setting device 13 signal and a welding voltage, and outputs a pulse high constant-current Ip by a transistor driving circuit 18. A transistor is driven 18 by operating a base controlling circuit 17 by a combined signal VB of a base current setting device 14 signal VBO and a signal of a charging and discharging circuit 19 by the signal Vck. A base current is decreased gradually from a pulse current and becomes a base current, a welding arc is concentrated, an arc cut and a magnetic blow arc instability of the time of a spray shift are prevented, and a smooth welding arc is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a welding power source that alternately supplies pulse and base currents to a welding arc section to weld a welding wire in the form of spray droplets. .

(Conventional configuration and its problems) FIG. 1 shows an example of a conventional welding power source.

As shown in the figure, in this conventional example, the welding power supply input terminal 1
Welding main transformer 2 equipped with a rectifier/smoothing circuit 3, welding output control element (transistor) 4, welding characteristic adjustment reactor 5, regeneration diode 6, welding current detection shunt 7
．． Welding power output terminal 8, energizing contact tip 9,
Welding wire 10, welded object part 11, welding output setting device 1
3. Consists of base electric etc.

In FIG. 1, the reference clock circuit 15 is a signal that inputs the signal of the welding output setting device [3] and the detection signal of the welding voltage v8, and reflects the information of the pulse period Tf and pulse width t with H level and L level signals. VCk is output to the pulse control circuit 16. The pulse control circuit 16 inputs the VCk signal and the signal of the shunt 7 that detects the welding current, and controls the VCk.
While the signal is at H level, a command signal is sent to the main transistor drive circuit 18 so that the pulse peak current value p is set depending on the welding material, wire diameter, etc. While the VCk signal is at the L level, the base control circuit 17, which receives the signal ■6° from the base electric tip setting device 14 and the signal from the shunt 7, controls the base peak current value set by the welding material, wire diameter, etc. A command signal is sent to the main transistor drive circuit 18 under feedback control so that the output voltage becomes 8. The main transistor drive circuit 18 receives signals from the pulse control circuit 16 and the base control circuit 17 and controls the ON-OFF operation of the welding output control main transistor 4. FIG. 2 shows the above control.

Here, the base current value (8) is mainly restricted by the following two points due to welding phenomena. In other words, in the pulse welding method in which the welding wire is welded in the form of spray droplets, in order to smooth the spray transfer and concentrate the welding arc, ■8
It is not desirable to make it large. However, in order to prevent arc instability from occurring due to the magnetic blow (arc blow) phenomenon of the welding arc, it is not preferable to reduce the value of .

Therefore, in the conventional example, when the arc is stable and stationary, the current value of IE is determined by a compromise between these two contradictory constraints.

(Purpose of the Invention) The present invention aims to solve the problems of the conventional example, without impairing the concentration of the welding arc and smoothing the spray transfer, and at the same time preventing the arc from becoming unstable due to the magnetic arc blow phenomenon. The purpose is to prevent this.

(Structure of the Invention) In order to achieve the above object, the present invention automatically feeds a welding wire to a predetermined peak value IP (for example, 250 to 70
A pulse part current that is constant current controlled to be 0 A) and a base part current that is constant current controlled to be a predetermined peak value In (for example, 50 to 200 A) are alternately supplied to the welding arc part. In a welding power source that welds a welding wire as a spray droplet, the input signal Vex, which reflects information about the welding output, is controlled so that it is in the pulse part when it is at the H level, and in the base part when it is at the L level. , in the pulse section, the predetermined pulse peak current value I
a pulse control circuit that performs constant current control so that the voltage becomes P, a charging/discharging circuit that outputs a charging/discharging voltage signal in synchronization with the H level and L level of the input signal VCX, and an output signal VIN of the charging/discharging circuit and a base. Setting signal VR by current setting device
a selection circuit that selects and outputs the signal with a higher value by comparing the values of 0 and 1, and controls a constant current so that the predetermined base peak current value 8 is reached according to the value of the output signal VB of the selection circuit. It is characterized by comprising a base control circuit.

(Description of Embodiment) FIG. 3 shows an embodiment of the welding power source according to the present invention, in which parts equivalent to those of the conventional one of the first JI are denoted by the same reference numerals. Output signal V of reference clock circuit 15
CK is input to the pulse control circuit 16 and also to the charging/discharging circuit 19 . In the charge/discharge circuit 19, the impedance is converted by open collector type comparators C, . . . P, and the output of C0 performs the same operation as VCk. The output V[11 of resistor R3 and R diode D:4.19 has the waveform shown in FIG. 4. That is, a substantially triangular wave with a rising waveform determined by the values of the resistor R3 and the capacitor C□ and a falling waveform determined by the values of the capacitor C1 and the resistor R4 is obtained. The signal VB□ having such a waveform is compared with the setting signal vIlo of the set value by the base current setter 14 in the selection circuit 20 by the diode D□lD2.
The higher value of the selected setting signal VBO and signal VB□ becomes the input signal v8 of the base control circuit 17. As a result, as shown in FIG. 4, the base control circuit 17 causes the welding current waveform (2) to become a base current that has a downward slope following the pulse portion, and then becomes a base current that has a constant peak value.

(Effects of the Invention) In pulsed arc welding, in which welding is performed by one-pulse droplet drop using a welding wire as spray droplets, the welding arc occurs immediately after droplet drop, that is, when the pulse portion ends and the base portion begins. is the time when the arc length is the longest and arc instability and arc breakage are likely to occur. At this time, the phenomenon of magnetic blowing (arc instability) in which the arc disappears and becomes unstable due to the influence of magnetism is most likely to occur.

The present invention prevents arc instability such as magnetic blowing by setting the base current value at the end of the pulse section, which is most likely to occur, to a value larger than the steady value, and sequentially increases the base current to the steady value over time. In terms of value, it simultaneously centralizes the welding arc and smoothes the spray transfer, and it will greatly contribute to industry by realizing a stable and smooth welding arc.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a conventional welding power source. Second
The figure is a diagram showing waveforms of various parts of the apparatus of FIG. 1. FIG. 3 is a diagram showing an embodiment of the present invention. FIG. 4 is a timing chart of the arc length and waveforms of various parts in FIG. 3. 1... Power supply input terminal for welding, 2... Main transformer for welding, 3... Rectification/smoothing circuit, 4... Welding output control element (transistor), 5... Reactor for adjusting welding characteristics , 6...Welding diode, 7
... Welding current detection shunt, 8... Welding power output terminal, 9... Contact tip for energizing, 10...
・Welding wire, 11... Workpiece part, 12... Welding arc, 13... Welding output setting device, 14... Base current setting device, 15... Base path, 19... Charging Discharge circuit, 20...Selection circuit, R□~R6...Resistor, D,~
D...Diode, C5...Capacitor, Cmp
...Open collector type comparator, ■...Control power supply, E...Control circuit ground, ■8...Welding current, ■
. . . . input signal of the pulse control circuit, VBo . . . setting signal of the base current setter, vnx . . . output of the charge/discharge circuit 19, VB . . . output of the selection circuit 20. Patent applicant: Matsushita Electric Industrial Co., Ltd. (branch) Figure 2 o -, t

Claims (1)

[Claims] The welding wire is automatically fed to the welding arc, and a pulse part current that is constant current controlled to have a predetermined peak value and a base part current that is constant current controlled to be a predetermined peak value are alternately applied to the welding arc part. In a welding power source that supplies the welding wire to weld in the form of spray droplets, when the input signal that reflects information about the welding output is at H level, it becomes a pulse part, and when it is at L level, it becomes a base part. and a pulse control circuit that performs constant current control so that the predetermined pulse peak current value is achieved in the /4 pulse portion, and outputs charging and discharging voltage signals in synchronization with the H level and L level of the input signal. a charging/discharging circuit; a selection circuit that compares an output signal of the charging/discharging circuit with a setting signal from a base current setting device and selects and outputs a signal with a higher value; and a selection circuit that selects and outputs a signal with a higher value; and a base control circuit that performs constant current control so that the predetermined base peak current value is achieved accordingly.