JPS597480A - Automatic arc welding machine - Google Patents

Abstract

PURPOSE:To obtain a titled welding machine which prevents generation of a spherical lump to a wire tip part and starts satisfactorily an arc of the next time, by constituting so that a switching element is controlled by an output voltage detecting signal after welding is ended, and an output control signal at the time of steady welding. CONSTITUTION:In a welding machine for executing automatic arc welding by connecting a DC power source 1 to a welding wire 4 and a base metal 5 by interposing a transistor 2 which becomes a switching element and a welding reactor 3, an AND signal of an H level signal Tb during a fixed time from a timing circuit 13, a pulse signal CK from a pulse generating circuit 12 and a welding output voltage detecting signal Vx from an output voltage detecting output 10 is generated by an AND circuit 9, an OR signal of said signal and an output control signal from a steady time transistor controlling circuit 11 is derived so that it is supplied to a transistor driving circuit 7 from an OR circuit 8, and generation of a spherical lump at the tip of the wire 4 is prevented by controlling exactly the welding output stopping time.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic arc welding machine that performs arc welding by automatically feeding a welding wire. Conventionally, the control at the end of welding in an automatic arc welding machine has been difficult.

In order to prevent the welding wire from sticking to the workpiece, a so-called anti-stick time period is usually provided in which the welding output voltage is stopped by providing a delay time after the wire feeding is stopped. The conventional method is to set a fixed time limit as the unstick time limit regardless of the welded portion. However, if this anti-stick time period is too long, there is a risk of causing a puncture phenomenon or promoting the formation of a ball at the tip of the wire at the end of welding, which may impede the arc start characteristics at the start of the next welding. Therefore, it is very difficult to set the anti-stick time limit.

FIG. 1 shows a sequence of welding termination control of a conventional welding machine. The anti-stick time period tb in Fig. 1 is the time "b" until the wire feeding actually stops and the welding current is turned off.
It is set longer than r.

To be careful, the no-load voltage v0 of the welding machine is applied during the time tb-tl)r, which promotes the formation of a ball at the tip of the wire. Fig. 2 is an example of a conventional method developed from the method shown in Fig. 1).During the anti-stick time period t1), the output voltage is lowered to a value of VB during steady welding to generate a ball at the tip of the wire. This is a method to prevent this.

However, in both the methods shown in FIG. 1 and FIG. 2, it is difficult to manage the time limit of the capacitor and the voltage of VB, and a sufficient effect cannot be obtained.

Therefore, an object of the present invention is to provide the minimum necessary anti-stick time period for anti-stick, to prevent balls from forming at the tip of the wire at the end of welding, and to improve the next arc start. Our purpose is to provide an automatic arc welding machine.

An embodiment of this invention is shown in FIGS. 3 and 4. Third
In the figure, 1 is a DC power supply, 2 is a transistor serving as a switching element for output control, a 3-piece welding reactor,
4 is a welding electrode made of a wire, 5 is a base body, and 6 is a resistor connected between the collector and emitter of the transistor 2. Note that a mechanism (not shown) for automatically feeding the wire is provided. 7 is a transistor drive circuit, 8 is an OR circuit, 9 is an AND circuit, 1o is an output voltage detection circuit, 11 is a transistor drive circuit in steady state, and 12 is a transistor drive circuit shown in FIG. Pulse signal generation circuit, 1
3 is a timer circuit which outputs an H level signal for a certain period of time in response to a welding stop command.

Next, the operation of this automatic arc welding machine will be explained. Simultaneously with the welding stop command, the timer circuit 13 is activated for a certain period of time t.
Level 11. give a signal. When the wire feed stops and the welding current becomes 0, the output voltage becomes the heat load voltage V.
. When the time period ``br'' has elapsed, the output voltage detection signal vX of the output voltage detection circuit 1o becomes L level. Therefore, the output signal a of the AND circuit 9 remains at the fourth level only during the period ``br''.
The /list signal CK of F in the figure is output, and the transistor 2 is turned on through the OR circuit 8 and the transistor drive circuit 7. In this way, it is possible to stop the welding output with a delay of exactly tbr at the end of welding, thereby ensuring a good arc start the next time without wire sticking and without forming a ball at the wire tip. Obtainable.

Note that when the transistor 2 is off, the resistor 6
The output voltage detection circuit 10 is used to detect the no-load voltage (2), and a high resistance value is selected so as not to generate a welding arc and a ball at the tip of the wire at the end of welding. Therefore, in the output voltage signal diagram 00 in FIG. 4, the shaded portion is the voltage generated via the resistor 6.

As described above, the automatic arc welding machine of this invention detects a pulse signal and a welding output voltage value, and generates a welding output voltage detection signal which becomes H level when the voltage is less than a certain voltage value and becomes L level when the voltage value is above a certain voltage value. , creates an AND signal with a high level signal that is output for a certain period of time in response to a welding stop command, and turns on and off the welding output control switching element using this AND signal and the high V-pel and low level signals during steady welding. Since the logical sum signal with the output control signal during steady welding is supplied to the switching element drive circuit for controlling the welding output, the wire does not stick at the end of welding, and no balls are generated at the tip of the wire. The effect is that it is possible to obtain the minimum necessary anti-stick time period and to realize good arc start performance at the next arc start.

[Brief explanation of the drawing]

1 and 2 are timing diagrams of a welding sequence according to a conventional method, FIG. 3 is a circuit diagram of an embodiment of the present invention, and FIG. 4 is an operation timing diagram thereof. 1...DC power supply, 2...Output control transistor (
switching element), 3... welding reactor, 4.
... Solution chamber m (wire), 5... Work to be welded, 6...
Resistor, 7... Transistor drive circuit, 8... OR circuit, 9... AND circuit, 10-... Output voltage detection circuit, 11... Transistor control circuit during steady welding, 12...
...Pulse signal generation circuit, 13...Timer circuit, CK
... Pulse signal, Tl) ... Delay signal at welding stop (
High level signal) -Vx...Output voltage detection signal Figure 2

Claims (1)

[Claims] A mechanism that automatically feeds welding wire, a switching element that controls welding output, a drive circuit for this switching element, a resistor connected in parallel to the transistor, and a pulse signal generator that generates a pulse signal with a constant period. circuit and
An output voltage detection circuit that detects the welding output voltage value and outputs a welding output voltage detection signal that becomes high level when the voltage is below a certain voltage value and becomes low level when the voltage is above the certain voltage value, and an output voltage detection circuit that outputs a welding output voltage detection signal that becomes high level when the voltage is below a certain voltage value and becomes a low level when the voltage is above the certain voltage value, and in response to a welding stop command. a timer circuit that outputs a high level signal for a certain period of time, an AND circuit that outputs a signal of the logical product of the pulse signal, the welding output voltage detection signal, and the high level signal, and a steady welding output of high level and low level. a switching element control circuit during steady welding that outputs a control signal;
An automatic arc welding machine comprising: an OR circuit that provides an OR signal of the output control signal during steady welding and the AND signal to the transistor drive circuit.