JPH0131990B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a welding power source that performs arc welding by automatically feeding a welding wire, which is a consumable electrode.

Conventional technology In conventional welding power sources of this type, so-called wire slowdown control is used to reduce the wire feed speed at the start of welding compared to during steady welding in order to smoothly generate an arc at the start of welding, and to reduce the welding output to steady welding. So-called hot-start control, in which the amount of heat is increased more than the time, has been a control method that has been used in the past. The trigger signal for switching from the wire slowdown or hot start state to the steady state has generally been based only on a welding current detection signal that detects the presence or absence of welding current. That is,
A conventional welding power source of this type had a configuration shown in FIG. In FIG. 4, 1 is a welding power input terminal, 2 is a welding transformer, 3 is a rectifier, 4 is a welding output control element, and 5 is a reactor for adjusting welding performance. 6 is a shunt, 7 is a welding power output terminal, 8 is a contact chip for energizing, 9 is a welding wire, 10 is a workpiece to be welded, 11 is a welding arc, 12
is a wire feeding motor, 13 is an output control circuit, 1
4 is a welding current detection circuit.

In the above configuration, the welding current detection circuit 14 detects the detection signal of the shunt 6 and determines the presence or absence of the welding current A.
The signal is outputted to the output control circuit 13, and the output control circuit 13 outputs the signal to the wire feed motor 12 according to the A signal.
outputs an M signal for switching between slow-down speed and steady welding speed, and at the same time outputs a V signal to switch between hot start output and steady welding output to welding output control element 4.
It was outputting a signal. FIG. 5 is a timing chart of each signal in FIG. 4. Note that, as shown at time td in FIG. 5, the V signal and the M signal may be switched to the steady state condition with a slight delay from the detection of the A signal.

Problems to be Solved by the Invention In the conventional example described above, only the welding current detection signal is relied upon as a signal for switching from the slow-down condition and the hot-start condition to the steady condition. It is not possible to detect variations in the time until arc occurrence due to differences in
As a result, wire breakage, wire burning, etc. occurred, and uniform arc starting performance could not be obtained. Further, there is a problem in that it is necessary to deal with differences in wire diameter and wire material by changing the slow-down conditions, hot-start conditions, and time td shown in FIG. 5. Even if such measures are taken, arc starting performance will not be uniform, especially if the wire is hard to melt due to its low resistivity, such as aluminum wire, and the wire will continue to be in a semi-molten state and no arc will occur. Or,
As a result, an excessive resistance force is applied to the wire, causing a wire buckling accident, or an excessive wire burnout causes the molten wire 9 to explode into the energized tip 8.
This has caused accidents such as melting and adhesion.

Means for Solving the Problems In order to solve the above conventional problems, the present invention provides a welding current detection circuit that detects the presence or absence of welding current and outputs a detection signal, and a welding current detection circuit that detects the presence or absence of welding current and outputs a detection signal. a wire short circuit detection circuit that determines whether a welding arc is generated in a non-contact manner and outputs a signal, and a welding output control element and a welding and an output control circuit that outputs a control output signal to the wire feeding motor, and the output control circuit is configured such that the output signal of the welding current detection circuit is in a state where welding current is present at the time of arc start to start welding; An AND operation section operates when both the output signals of the wire short circuit detection circuit detect non-contact arc generation, and the AND operation results in a wire feeding speed lower than that during steady welding. The welding output control element switches the control output signal to the wire feed motor so that the speed changes from a so-called slowdown speed to a steady welding speed, and changes the welding output from a hot start output, which is higher than that during steady welding, to a steady welding output. It consists of a switch that switches the control output signal to the output signal.

Effect In the above configuration, the output control circuit detects that the output signal of the welding current detection circuit is in a state where welding current is present at the time of arc start at the start of welding, and the output signal of the wire detection circuit is in a state in which a non-melting arc is generated. If so, the wire feed speed is controlled to be a so-called slowdown speed and steady welding speed, which is lower than that during steady welding, and the welding output is changed from hot start output, which is higher than that during steady welding, to steady welding. Since the output is controlled, the shape of the wire tip,
The slowdown condition and hot start condition are continued until a wire short circuit is detected regardless of the wire diameter, wire material, etc., and the wire is sufficiently heated and melted, resulting in smooth and uniform arc start performance.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 3.

In FIG. 1, the same components as those shown in FIG. 4 are designated by the same numbers, and their explanations will be omitted.

15 is a wire short circuit detection circuit connected between a pair of welding power source output terminals, which determines whether the welding output voltage is above or below a certain value, and based on this judgment result, the welding wire 9 comes into contact with the workpiece 10. It determines whether there is a short circuit or a non-contact welding arc is generated and outputs a signal S.

Welding current detection circuit 14 detects the presence or absence of welding current and outputs detection signal A.

The output control circuit 15 receives the detection signal A and the signal S, and outputs the signal V and the signal M to the welding output control element 4 and the welding wire feeding motor 12, respectively.

Next, the operation of the above configuration will be explained with reference to FIGS. 2 and 3. At the start of welding, the output control circuit 13
sends an output signal to the wire feed motor 12 with a slowdown condition lower than that during steady welding. At the same time, a hot start condition output signal is sent to the welding output control element 4 to command a higher output than during steady welding. Welding wire 1 fed under slowdown conditions
2 contacts the workpiece 10 (time t1 in FIG. 2), the welding current detection signal A outputs a welding current state. At the same time, the wire short circuit detection signal S outputs the wire short circuit state. The output control circuit 13 receives a signal indicating that welding current has been detected, but also receives a wire short circuit signal at the same time, so the command signal M to the wire feed motor 12 remains in the slowdown condition, and the welding output control element 4 The command signal V to remains in the hot start condition. As these control conditions continue, the welding wire is sufficiently heated and melted to generate an arc at time t2 in FIG.
As a result, the wire short circuit detection signal S is inverted to a non-contact state, so the output control circuit 13 outputs output signals M and V commanding steady welding conditions to the wire feed motor 12 and welding output control element 4, respectively. .
The above-mentioned effects realize a smooth and uniform arc start.

Note that the output control circuit 13 is constituted by, for example, a microcomputer, and controls the above operations according to the program shown in FIG.

Further, the welding current detection circuit 14 uses, for example, a comparator to determine whether or not a welding current is being applied, depending on whether the signal value from the shunt 6 is greater than or equal to a certain value or less than a certain value. Similarly, the wire short circuit detection circuit 15 uses, for example, a comparator to determine whether there is a wire short circuit based on whether the output voltage of the welding power source is above or below a certain value.

Effects of the Invention As is clear from the above explanation, according to the present invention, the slowdown and hot start conditions are continued until the wire short circuit is released, regardless of the wire tip shape, wire diameter, wire material, etc. It is sufficiently heated and melted to provide smooth and uniform arc starting performance.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a consumable electrode type welding power source showing an embodiment of the present invention, Fig. 2 is a signal waveform diagram of the main part of Fig. 1, and Fig. 3 is a flowchart of the main part of the same part.
FIG. 4 is a block diagram of a conventional consumable electrode type welding power source, and FIG. 5 is a signal waveform diagram of the main parts. 4... Welding output control element, 9... Welding wire, 10... Work to be welded, 12... Wire feeding motor, 13... Output control circuit, 14... Welding current detection circuit, 15... Wire Short circuit detection circuit.

Claims (1)

[Claims] 1 A welding current detection circuit that detects the presence or absence of welding current and outputs a detection signal, and a wire that outputs a signal after determining whether the welding wire is short-circuited by contact with the workpiece or a welding arc is generated without contact. comprising a short circuit detection circuit and an output control circuit that receives output signals from the welding current detection circuit and wire short circuit detection circuit and outputs a control output signal to a welding output control element and a welding wire feed motor, The output control circuit detects both that the output signal of the welding current detection circuit is in a state where welding current is present at the time of arc start at the start of welding, and that the output signal of the wire short circuit detection circuit is in a state that non-contact arc is generated. The logical product operation unit operates upon detection of the A consumable electrode characterized in that it is comprised of a switch that switches the control output signal to a welding output control element so that the welding output changes from hot start output, which is higher than that during steady welding, to steady welding output. Type welding power source.