JPH1177298A - Arc spot welding control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To arbitrarily set the current waveform of arc. SOLUTION: This arc spot welding control device is provided with a current detection circuit 20, a reference waveform generation circuit 18, a comparison circuit 19, and a current control circuit 15. The waveform of the current flowing in a power supply circuit of an arc torch is detected by the current detection circuit 20, and the reference waveform of the arc current is generated by the reference waveform generation circuit 18 under the predetermined condition. The detected waveform by the current detection circuit 20 is compared with the reference waveform by the comparison circuit 19, and the error signal to compensate the deviation between both waveforms is inputted in the current control circuit 15 to match the waveform of the current flowing through the power supply circuit of the arc torch with the reference waveform.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arc spot welding machine and, more particularly, to an arc spot welding control device for precisely welding small parts in a non-contact manner.

[0002]

2. Description of the Related Art Since an arc spot welding machine can be constructed without bringing an electrode into contact with a workpiece, it is possible to weld parts having complicated shapes and curved surfaces, parts that are easily deformed, and the like. In addition, since local welding is performed in a very short time, there is little thermal influence and thermal distortion on portions other than the welded portion, and thus it is suitable for welding precision parts and small parts. For this reason, the pulse arc spot welding machine is widely used for welding thin plates and wires such as electronic components, electric components, electric wire components, and mechanical components.

[0003]

However, in the conventional pulse arc spot welding machine, the welding time is controlled by a digital timer, so that the welding time is 60 ms in units of 10 ms.
It can be set only in the range of ~ 600 ms, and it was considered difficult to set the minimum pulse width to 60 ms or less.

[0004] Further, regarding the arc current, the rise and fall of the current are not controlled, and when the arc current is changed, the current value is reduced after the end of the main current, called a crater control, to change the arc torch. Since this is performed by two-stage control of energization, there is a problem that a special material or a plated material is easily affected by heat. Furthermore, in the conventional pulsed arc spot welding machine, even if the arc is misfired during welding, it cannot be detected, and there is an accident that the workpiece comes into contact with the arc torch before the arc torch starts and the workpiece is welded to the electrode. Often occurred.

An object of the present invention is to provide an arc spot welding control device which can freely set the pulse width of an arc and therefore can perform arc welding in a short time and can arbitrarily set an arc current waveform. Another object of the present invention is to provide an arc spot welding control device capable of coping with a misfire of an arc current or a short circuit accident of an arc torch.

[0006]

In order to achieve the above object, an arc spot welding control apparatus according to the present invention provides an arc spot welding apparatus having a current detection circuit, a reference waveform generation circuit, a comparison circuit, and a current control circuit. In the welding control device, the current detection circuit detects a waveform of a current flowing through a power supply circuit of the arc torch and outputs the detected waveform to a comparison circuit, and the reference waveform generation circuit includes a predetermined reference waveform. And outputs the reference waveform to a comparison circuit. The comparison circuit compares the detected waveform with the reference waveform, and outputs an error signal for compensating for a difference between the two waveforms to the current control circuit. The current control circuit is connected to a power circuit of the arc torch, and receives an error signal as an input and matches a current waveform flowing through the power circuit of the arc torch with a reference waveform.

The reference waveform generated by the reference waveform generating circuit has a current value, a rise time, a welding time, and a fall time which are arbitrarily set.

In addition, a short detection circuit is provided, which receives a detection waveform output from the current detection circuit as an input,
Before the arc start, an arc start stop command is output when an energizing current of the power circuit of the arc torch is detected.

In addition, a misfire determination circuit is provided for outputting a welding failure signal when the current value of the power supply circuit of the arc torch is detected to be zero during the energization time after the arc start.

The misfire determination circuit determines whether or not a misfire has occurred based on the current value of the detected waveform at the end of the welding time.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an arc spot welding control device according to the present invention will be described below with reference to the drawings. In FIG. 1, a welding control device 1 of an inert gas arc spot welding machine includes a gas hose 3 leading to a gas cylinder 2 of an inert gas, an output cable 6 of a base material 4 and a torch 5,
7, a gas hose 8 leading to the torch 5, and a power supply input line 9 are connected.

At the time of welding work, the switches on the control panel 10 are handled, an AC voltage of 200 V is inputted from the input line 9, and an inert gas is provided on the arc torch 5 as shown in FIG. An arc is generated between the electrode 11 and the base material 4 while emitting from the base material 12, and the work is welded by melting only the base material 4 and the filler rod or the base material 4 in the space shielded by the inert gas. FIG. 3 shows a control circuit built in the welding control device 1. In the figure, the power circuit of the arc torch includes a step-down circuit 13, a rectifier circuit 14, a current control circuit 15, and a series trigger circuit 16.

The 200 V AC voltage of the power supply is supplied to the step-down circuit 13.
The DC voltage is rectified by the rectifier circuit 14 and then rectified by the rectifier circuit 14. Then, the arc current is controlled by the current control circuit 15 and input to the series trigger circuit 16.

The series trigger circuit 16 applies a high voltage to the arc torch 5 to generate an arc between the electrode 11 and the base material 4. When starting the arc discharge, a high voltage pulse is supplied from the auxiliary high voltage circuit 17. Is input to generate a trigger pulse. In the present invention, the welding current of the arc torch is
The control is performed based on the reference waveform generated by the reference waveform generation circuit 18. In FIG. 3, the reference waveform generation circuit 18
The reference waveform is created using the current value, the rise time, the welding time, and the fall time as setting conditions. The created reference waveform is input to the comparison circuit 19. On the other hand, the waveform of the current flowing through the power circuit of the arc torch is represented by the current detection circuit 2
The detected waveform is input to the comparison circuit 19.

The comparison circuit 19 detects the input detection waveform,
The signal is compared with a reference waveform and output as an error signal for compensating for a difference between the two waveforms. The signal is amplified by the error amplifier circuit 21 and input to the current control circuit 15. Current control circuit 15
Makes the welding current waveform flowing through the arc torch match the shape of the reference waveform based on the input error signal.

In FIG. 4, the rise time t ₁ of the reference waveform is shown.
Is, for example, 0 to 49 ms, and the welding time t ₂ -t ₁ is _{1 to} 49 ms.
9 ms, the fall time t ₃ -t ₂ is arbitrarily set within a range of 0 to 499 ms, and the current value is freely determined within a range of 1 to 50 A.

The control circuit further includes a short-circuit detection circuit 22,
And a misfire determination circuit 23. Short circuit detection circuit 22
Is to check whether a current is flowing to the arc torch 5 before impressing the triker pulse on the arc torch 5. The detection waveform output from the current detection circuit 20 is input and the power is supplied before the arc starts. When the current is detected, an arc start stop command is output.

The misfire determination circuit 23 includes an electrode 11 and a base material 4
To detect the misfire of the arc once generated during
The determination is made based on the output signal of the current detection circuit 20, and the point of the determination is as follows. That is, the welding current has a rising region (t ₀ ~t ₁₎ as shown in FIG. 4, a weld region (t ₁ ~t _2), trapezoidal waveform consisting of a rising region (t ₂ ~t ₃₎ There, the weld area (t ₁ ~t ₂₎ the welding current is constant.

The determination of misfire is made when the detection signal of the current detection circuit 20 is input and the time t ₂ has elapsed from the beginning, and flows into the circuit of the arc torch 5 when the time t ₃ has elapsed from the beginning. Judgment is made based on whether the current maintains a certain value. Current flowing through the circuit of the arc torch 4 when elapsed time t ₂ is determined to be misfiring when zero, and outputs a signal of poor weld from the beginning. The detection waveform of the current detected by the current detection circuit 19 is
The current is displayed on the current display circuit 24.

In the present invention, when the auxiliary high voltage circuit 17, the series trigger circuit 16 and the reference waveform generation circuit 18 are activated and stopped, a short-circuit detection circuit 22, a misfire determination circuit 23, and an error amplification circuit 21 are operated by an input / output circuit 25. Are executed based on a series of sequences set by the sequence circuit 26 on the basis of the signal from. FIG. 5 shows a time chart based on the sequence.

[0021]

As described above, according to the present invention, since the welding current is controlled based on the reference current waveform generated by the reference waveform generation circuit, the time for applying the arc current can be set arbitrarily. Arc welding can be performed in a time (2 to 50 ms in units of 1 ms), the magnitude of the arc current can be set freely, and the rise time and fall time can be set arbitrarily to perform welding work. it can.

Further, since the current of the power circuit of the arc torch is detected and the short-circuit detection circuit and the misfire determination circuit are operated by the current detection output, for example, when the torch comes into contact with the workpiece, the arc start is started. It is possible to stop and stop the misfiring during the welding work by informing and outputting the occurrence of an abnormal situation, thereby preventing the welding of the electrode and the work and the occurrence of poor welding.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an inert gas arc spot welding machine.

FIG. 2 is a diagram showing a structure of a torch.

FIG. 3 is a block diagram showing a control circuit of the welding control device.

FIG. 4 is a diagram showing a waveform of a fork current.

FIG. 5 is a time chart illustrating an operation of the control circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Welding control device 2 Gas cylinder 3 Gas hose 4 Base material 5 Arc torch 6 Output cable 7 Output cable 8 Gas hose 9 Input line 10 Control panel 11 Electrode 12 Nozzle 13 Step-down circuit 14 Rectifier circuit 15 Current control circuit 16 Series trigger circuit 17 Auxiliary high voltage circuit 18 Reference waveform generation circuit 19 Comparison circuit 20 Current detection circuit 21 Error amplification circuit 22 Short circuit detection circuit 23 Misfire determination circuit 24 Current display circuit 25 Input / output circuit 26 Sequence circuit

Claims (5)

[Claims] A current detection circuit, a reference waveform generation circuit,
An arc spot welding control device having a comparison circuit and a current control circuit, wherein the current detection circuit detects a waveform of a current flowing through a power supply circuit of the arc torch and outputs the detected waveform to the comparison circuit. The reference waveform generation circuit generates a predetermined reference waveform and outputs the reference waveform to a comparison circuit.The comparison circuit compares the detected waveform with the reference waveform and compensates for a deviation between the two waveforms. Output to the current control circuit, the current control circuit is connected to the power circuit of the arc torch,
An arc spot welding control device wherein a current waveform flowing through a power supply circuit of an arc torch with an input of an error signal matches a reference waveform. 2. The arc according to claim 1, wherein the reference waveform generated by the reference waveform generation circuit has a current value, a rise time, a welding time, and a fall time that are arbitrarily set. Spot welding control device. 3. A short-circuit detection circuit, which receives a detection waveform output from a current detection circuit as an input and detects an arc start when a current supplied to a power supply circuit of an arc torch is detected before the arc start. The arc spot welding control device according to claim 1 or 2, which outputs a stop command. 4. A misfire determination circuit for outputting a welding failure signal when a current value of a power supply circuit of an arc torch is detected to be zero during an energization time after an arc start. The arc spot welding control device according to claim 1, 2 or 3, wherein 5. The arc spot welding control device according to claim 4, wherein the misfire determination circuit determines whether or not a misfire has occurred based on the current value at the end of the welding time of the detected waveform.