JPS6247109B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a control device for gas-shielded arc welding, which is performed while shielding the electrode and the welding part from the atmosphere by supplying a shielding gas such as argon gas or carbon dioxide gas to the electrode and the welding part.

In gas-shielded arc welding using a consumable or non-consumable electrode, the electrode and workpiece are extremely hot immediately after welding, so if the shielding gas discharge is stopped at the same time as welding, the electrode and workpiece will be at a very high temperature. Can be severely damaged by oxidation or nitridation in the atmosphere. For this reason, it is necessary to provide a so-called shield gas afterflow period in which the shield gas is continuously discharged even after welding is normally completed until the electrode and the workpiece are sufficiently cooled to a temperature at which they are not contaminated by the atmosphere. Conventionally, a timer was set separately for this gas afterflow time, and the shielding gas was discharged for a certain period of time after the completion of welding. However, this gas afterflow time varies depending on the welding current; for example, if the welding current is small, the heating range of the welded object is narrow and the electrode temperature is low, so it is only necessary to discharge the shielding gas for a short time after welding is completed. . On the other hand, when the welding current is large, the molten pool is large and the heating range is wide, and the electrode temperature is also high, so shielding gas is discharged for a long time until the welding pool is no longer exposed to atmospheric contamination to shield them from the atmosphere. It is necessary to keep it.
Therefore, when shielding gas is supplied for a certain period of time after welding is completed regardless of the welding current as in the past, if it is too short it will contaminate the electrode and welding area, and if it is too long it will waste the shielding gas. Become. Furthermore, even if the timer's time limit is variable, each time the welding current used changes, it is necessary to set it again to the optimum time, which makes the operation complicated, and if the setting is incorrect, serious defects may occur in the welding result. Become.

The present invention focuses on the above points and provides a control device that automatically sets the shielding gas afterflow time to an optimal value according to the welding current to protect the electrode and the welded part from atmospheric contamination after welding is completed. This is what I did.

FIG. 1 is a diagram showing an embodiment in which the apparatus of the present invention is applied to a movable core type AC arc welding machine.
Figure a is a configuration diagram showing the main parts of a movable core type AC arc welding machine. 1 is a welding transformer, and the fixed core 1
Primary coil and secondary coil 1 wound around 01
02 and a movable iron core 104. The movable core 104 is moved as indicated by the arrow in the figure by rotating the current adjustment handle 104. 2 is a wire 20 fixed to the movable iron core 102
2 supporting rollers 201, 201', 201'',
This is an output current indicator consisting of a spring 203 that tensions the wire 202, a fixed piece 204 of the spring 203, and a pointer 205. 3 is a variable resistor for setting the gas afterflow time, and the slider shaft 3 is adjusted according to the rotation of the shaft of the wire support roller 201.
01 is mechanically coupled to rotate. Therefore, when the movable iron core 103 moves due to the rotation of the current adjustment handle 104, the wire 202 tensioned by the spring 203 moves, the wire support roller 201 rotates, and the sliding of the variable resistor 3 mechanically connected to this shaft moves. The moving element shaft 301 rotates.
As a result, the gas afterflow time changes automatically. At this time, the diameter of the support roller 201 should be made large so that the rotation angle of the slider shaft 301 is 300 degrees or less over the entire range of current adjustment, or the diameter of the support roller 201 should be made large.
When inserting the speed reduction mechanism between the shaft 01 and the slider shaft 301, a general variable resistor can be used. Further, when a multi-rotation type potentiometer (for example, one that shows a change in the entire resistance value range in 10 rotations) is used as the variable resistor 3, the support roller 201 can be made smaller and the speed reduction mechanism can be omitted.

FIG. 1b is a connection diagram of the embodiment shown in FIG. 1a. In the figure, 4 is an AC power supply and switch 5
Power is supplied to the movable core type welding transformer 1 via the movable core type welding transformer 1. 8 is a welding electrode, 9 is a workpiece to be welded, 11 is a timer for shielding gas afterflow time, and a coil 13 of a solenoid valve for shielding gas discharge, which is supplied with power from a power source 12, is connected to its output terminals c and d. ing. The timer 11 is an instantaneous action limited time return type timer, and a starting signal is given by the auxiliary contact 5' of the switch 5. When the switch 5 closes at the start of welding, the timer 11 closes the circuit between the output terminals c and d, and when the switch 5 opens at the end of welding, the timer 11 starts the timer and sets the timer 11 connected between the terminals a and b. After the time limit determined by the resistance value of the variable resistor 3,
Terminals c and d are opened. As a result, the shielding gas starts to be discharged when the switch 5 is closed, and stops after the time period set by the timer 11 after welding is completed. The time limit of this timer is set so that the slider of the variable resistor 3 is linked to the position of the movable core as shown in Figure 1a. can be automatically adjusted in the same direction at the same time as the adjustment. In FIG. 1, an example was explained in which the moving amount of the current adjusting movable iron core 103 is directly converted into the rotating amount of the slider shaft of the variable resistor, so that the two are mechanically interlocked. For example, if a synchro oscillator is connected to the shaft of the roller 201 in FIG. It can be mechanically separated from the afterflow timer.

Fig. 2 is a configuration diagram showing an example in which the output signal of a welding current regulator is used as a time limit setting signal of an afterflow timer in a welding machine that adjusts the output current using a control switching element such as a thyristor or transistor. It is. In Fig. 2, 6 is a welding transformer similar to the embodiment shown in Fig. 1, but in the case of the same figure, a transformer with a normal approximately constant voltage characteristic that steps down the AC power source 4 to a low voltage suitable for welding. It is a vessel. The output of the welding transformer 6 is sent to the welding torch 2 via a control switching element 21 such as a thyristor or transistor.
It is supplied to the electrode 8 of No. 2 and the workpiece 9 to be welded. On the other hand, the opening/closing and conduction amount of the control switching element 21 is controlled by the continuity control circuit 26, and the continuity control circuit 26 obtains a difference signal between the output signal of the current adjustment circuit 24 and the output signal of the welding current detector 23. Comparator 25
is controlled by the output signal of Therefore, in the device shown in FIG. 2, the output current from the welding transformer 6 is controlled so that the difference between the signal set by the current adjustment circuit 24 and the signal from the current detector 23 is always approximately zero. The amount of conduction of the device 21 is controlled to obtain constant current characteristics. Reference numeral 11 denotes a timer for gas afterflow time, which has an instantaneous operation time limit return function similarly to the embodiment shown in FIG. 1, and drives the electromagnetic valve 27 for shielding gas discharge. Reference numeral 28 denotes a shielding gas source, for example, a gas cylinder and a suitable pressure reduction mechanism and flow rate adjustment mechanism.
supply shielding gas to. The output signal of the current adjustment circuit 24 is supplied to the timer 11, and the time limit is determined according to this signal, so that the afterflow time of the shielding gas is automatically set according to the welding current. It's getting old. Also 7
A switch serves as a welding start signal, and is a trigger switch or a foot switch attached to the welding torch 22. With the switch 7 closed, the current regulation circuit 24 supplies an output signal to the comparator 25 and the timer 11. Comparator 25 is current detector 23
Since the output signal of the current adjustment circuit 24 is zero, the output signal of the current adjustment circuit 24 is directly transmitted to the continuity control circuit 26, and the continuity control circuit 26 controls the control switch 21 according to the input signal.
Determine the amount of conduction. Electricity is supplied to the torch 22 and the workpiece 9 by the conduction of the control switch 21, and arc welding is started. When the welding current starts to flow, the current value is fed back to the comparator 25 by the detector 23, and the amount of conduction of the control switch 21 is determined so that the welding current reaches the set value. On the other hand, when the output of the welding current adjustment circuit 24 is generated by the closing of the switch 7, this output is also supplied to the timer 11, so the timer 11 is instantaneously activated by the closing of the switch 7 and opens the gas solenoid valve 27 to supply the shielding gas to the torch. 22. Further, when the switch 7 is opened at the end of welding, there is no input to the timer 11, so a timer starts from the time when the switch 7 is opened, and after the timer ends, the gas solenoid valve 27 is closed. The time limit at this time is determined by the output signal of the welding current adjustment circuit 24, and the welding current is oriented for a long time when it is large.

A more detailed example of the embodiment shown in FIG. 2 will be explained with reference to the connection diagram in FIG. 3. In FIG. 3, numerals 4, 6, 7, 8, and 9 are an AC power source, a welding transformer, a welding start switch, an electrode, and an object to be welded, respectively, similarly to the embodiment shown in FIGS. 1 and 2. SCR1 and SCR2 are unidirectional thyristors connected in antiparallel and correspond to the control switch 21 in FIG. 2. Current transformer CT1, rectifier REC1 and capacitor C1 constitute a current detector 23,
The DC power source E1 and the variable resistor VR1 constitute a welding current adjustment circuit 24, and the variable resistor VR1 functions as a welding current regulator. R16 is a resistor, and the output of the current detector 23 is supplied to both ends of the resistor, forming a comparator 25 that obtains a voltage difference between this resistor and the output of the current adjustment circuit 24. Rectifier REC2, resistors R11, R12,
R13, R14, R15, constant voltage diode ZD
1. Diode D1, single junction transistor UJ
1, UJ2, capacitor C2, pulse transformer TP
The secondary windings TS1 and TS2 and the DC power supply E2 constitute a conduction control circuit for the thyristors SCR1 and SCR2. Reference numeral 11 is an instantaneous operation time-limited return type timer similar to the embodiment shown in FIG. 1, but it operates instantaneously in response to a voltage input signal, and when the voltage input signal disappears, it starts a time-limited operation with a length corresponding to each input voltage. This is a voltage set type timer. Further, 12 is an AC power supply, and 13 is a coil of a gas solenoid valve. When the switch 7 is closed at the start of welding, the DC power source E1 is applied to the variable resistor VR1, and the welding current adjustment circuit 24 generates a voltage corresponding to the position of the slider of the variable resistor VR1. This output voltage is supplied to one end of the resistor R16 of the comparator 25, and is also supplied to the input terminal of the timer 11.
The comparator 25 is connected to a capacitor C1 which is detected by the current transformer CT1 and converted to direct current by the rectifier REC1.
The output signal of the welding current detector 23 smoothed by the welding current detector 23 is also supplied, and the difference signal between the output signal of this detector and the output signal of the current adjustment circuit 24 is supplied to the conduction control circuit 26. The conduction control circuit 26 is a pulse oscillation circuit using a known single-junction transistor, and includes a resistor R14 connected to a DC power source E2, a single-junction transistor UJ2, a pulse transformer TP, and a capacitor connected to the emitter of the single-junction transistor UJ2. Therefore, tensile oscillation is performed. At this time, since the output voltage of the comparator 25 is applied to the capacitor C2 through the diode D1, the continuity control circuit 26 outputs a signal representing the difference between the two only when the output signal of the current detector 23 is smaller than the output signal of the current adjustment circuit 24. , the capacitor C2 is charged and outputs a pulse at a period corresponding to the charging speed, thereby making the thyristors SCR1 and SCR2 conductive through the secondary windings TS1 and TS2 of the pulse transformer PT. Of the continuity control circuit 26, the rectifier REC2,
Resistors R11, R12, R13, constant voltage diode ZD1, and single junction transistor UJ1 are a circuit for synchronizing the oscillation phase of single junction transistor UJ2 with the phase of AC power supply 4. This synchronous circuit rectifies the voltage of AC power supply 4 in both waves by rectifier REC2, then cuts the wavefront by voltage regulator diode ZD1 to obtain a trapezoidal wave voltage synchronized with the voltage of AC power supply 4, which is applied between the base of single junction transistor UJ1. supply to. At this time, single junction transistor UJ1
The oscillating peak point voltage of a single junction transistor
If it is set higher than that of UJ2, the oscillation period of single junction transistor UJ2 can be synchronized with the voltage phase of AC power supply 4. It is also supplied to the output voltage of the current adjustment circuit 24 or the input terminal of the timer 11. The timer 11 starts operating from this point on, and the circuit between its output terminals CD is closed. As a result, the coil 13 of the gas electromagnetic valve is energized and continues to supply shielding gas to the welding portion of the electrode 8 and workpiece 9 during welding. When the switch 7 is opened due to the completion of welding, the conduction control circuit 26 stops its operation and the thyristor
SCR1 and SCR2 are immediately cut off to stop supplying power to the welding area. On the other hand, the input voltage of the timer 11 also disappears, but as mentioned above, this timer has a time-limited recovery function, so the time period starts from the moment the input voltage is cut off, and the time period ends, which is determined according to the voltage value supplied to the input terminal during welding. Rear output terminal c,
The space between d is opened. As a result, the gas solenoid valve 13 is also closed and the gas discharge to the welding area is stopped. A timer that operates in this manner, for example, charges a capacitor with input voltage, and when the input voltage disappears, the capacitor's charge is discharged through a discharge circuit with a fixed time constant, so that the terminal voltage of this capacitor drops below a fixed value. It is possible to use a timer that uses the period of time until timer 11
Of course, the present invention is not limited to the above-mentioned timer as long as the time limit is set according to the output signal of the current regulator.

In this manner, when using the device shown in the connection diagram of FIG. 3, the necessary afterflow time is automatically set only by adjusting the variable resistor VR1, which is a welding current regulator.

Fig. 3 shows an example in which the present invention is applied to a constant current type welding machine, but in a constant voltage type welding machine, the welding current varies depending on the diameter of the consumable electrode wire and its feeding speed. Since it is determined secondarily, the output setting signal of the welding machine itself cannot be directly used as the time limit setting signal of the gas afterflow timer as shown in FIG. In such cases, it is recommended to directly detect the setting signal for the electrode wire feeding speed, the signal corresponding to the actually detected welding wire feeding speed, or the welding current, and set the time limit of the timer according to the detected signal. It may be configured as follows. Furthermore, it goes without saying that even in a welding machine with constant current characteristics, the timer time limit may be set in accordance with the detection signal of the welding current.

As described above, the control device of the present invention is configured to automatically set the afterflow time of shielding gas according to the value of the welding current, so the afterflow time is adjusted each time the welding current is changed. There is no need to change the settings, and there is no need to change the settings, and there is no need to cause welding defects or damage to the electrodes due to incorrect settings.In addition, there is no need to set a gas afterflow time longer than necessary for safety reasons, so there is no need to waste shielding gas discharge. There will be none.

[Brief explanation of the drawing]

1 to 3 are a configuration diagram and a connection diagram showing an embodiment of a control device of the present invention. 3...Timer time setter, 8...Electrode, 9...
Object to be welded, 11...Timer, 23...Current detection circuit, 24...Current adjustment circuit, 103...Movable iron core for current adjustment.

Claims (1)

[Scope of Claims] 1. A control device for gas-shielded arc welding in which welding is performed while shielding an electrode and a welding part with shielding gas, including a welding current regulator, a timer for setting a shielding gas discharge time after welding, and a welding current controller. and a coupling means for coupling the welding current regulator and the timer so that the welding current regulator and the timer time change simultaneously in the same direction. 2. The gas shielded arc welding control device according to claim 1, wherein the coupling means is a means for mechanically interlocking the welding current regulator and the time limit regulator of the timer. 3. The gas shielded arc welding control device according to claim 1, wherein the coupling means is means for electrically interlocking the welding current regulator and the time limit regulator of the timer. 4. The gas shielded arc according to claim 1, wherein the coupling means is a means for coupling the welding current regulator and the timer by using the output signal of the welding current regulator as a time limit setting signal for the timer. Welding control device. 5. The coupling means is means for coupling the welding current regulator and the timer by using a signal corresponding to the welding current value determined by the welding current regulator as a time limit setting signal for the timer. Gas shielded arc welding control device according to scope 1. 6. The gas-shielded arc welding control according to any one of claims 1 to 5, wherein the timer is an instantaneous time-limited return timer whose output contact is closed when welding starts and a time limit starts when welding ends. Device.