JPS638873B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an arc welding sequence control circuit, and more particularly to an improved arc welding sequence control circuit capable of controlling switching between normal arc welding and crater welding.

Devices for sequence control of welding power supply, wire feeding, shielding gas control, etc. in arc welding are well known, and various sequences are used to control switching from normal welding conditions to crater welding conditions at the final stage of the welding process. The control circuit has been put into practical use.

FIG. 1 shows an example of a conventional arc welding sequence control circuit, in which sequence control is performed using switching elements such as transistors. In the figure, a first relay 10 is provided to control the supply of welding power and wire feeding,
A second relay 12 is also provided to switch between normal welding conditions and crater welding conditions. Furthermore, a solenoid valve 14 is provided to supply shielding gas to the welding area. For switching between each sequence, the device includes a trigger switch 16, and a DC power supply 18 is provided for supplying a control voltage to the sequence control circuit.

The first relay 10 has one end connected to a power source 18 and the other end connected to a trigger switch 16 via a diode 20. A series circuit of a capacitor 22 and a resistor 24 is connected in parallel to the relay 10, and a series circuit of resistors 26 and 28 is connected in parallel to the relay 10. The base of a transistor 30 is connected to the connection point between the resistors 26 and 28, the emitter of the transistor 30 is connected to the power supply 18, and the collector is connected to one end of the electromagnetic valve 14. The other end of the solenoid valve 14 is grounded.

On the other hand, the second relay 12 has one end connected to the power supply 18 via the collector-emitter of the transistor 32.
The other end is grounded via the diode 34, the normally open contact 12a of the relay 12, and the normally open contact 10a of the relay 10. transistor 3
The base of thyristor 3 is connected to the anode of thyristor 38 through resistor 36, and the base of thyristor 3
The connection point between the anode 8 and the anode is connected via a resistor 40 and a diode 42 to the connection point between the diode 34 and the normally open contact 12a described above. The anode of the thyristor 38 is further connected to the power supply 18 via a resistor 44.
The cathode thereof is connected to the anode of the diode 20 mentioned above, and the normally closed contact 12b of the relay 12 is connected to the connection point between the contacts 12a and 10a. The gate of the thyristor 38 is connected to the trigger switch 16 via a resistor 46 and a diode 48;
is connected via a resistor 50 to the power supply 18 and via a resistor 52. A diode 54 is connected between the other end of the second relay 12 and the trigger switch 16.

The conventional sequence control circuit has the above configuration, and its operation will be explained below.

Arc welding is started by turning on the trigger switch 16, and the relay 10,
An exciting current flows through the diode 20 and the trigger switch 16, and the first relay 10 is excited,
By turning on a welding power source relay contact and a wire feeding relay contact (not shown), welding power is supplied to the arc welder and welding wire is fed. At the same time, current flows from the power supply 18 to the resistors 26 and 28, and as a result, the transistor 30 is turned on, supplying a driving current to the solenoid valve 14, and the shielding gas is supplied to the welding part by driving the solenoid valve 14. Begins. Furthermore, relay 10
The relay contact 10a is turned on by the excitation, and the first relay 10 is self-held. At this time, the gate of the thyristor 38 is connected to the trigger switch 16.
Since the transistor 32 is grounded through the OFF state, the transistor 32 is also turned OFF and the relay 12 is not energized. As described above, by turning on the trigger switch 16, the welding power supply, wire feeding, and shielding gas supply are started, and normal arc welding is started.

After the above-mentioned welding is started, the trigger switch 16 is turned off, but the above-mentioned normal welding conditions are continuously maintained even with this off-operation. That is, by turning off the trigger switch 16, the gate potential of the thyristor 38 changes to the resistance 5.
It rises to the potential determined by the partial pressure ratio of 0.52,
At this time, since the cathode of the thyristor 38 is grounded via the relay contacts 12b and 10b,
Thyristor 38 becomes conductive. Therefore,
The base potential of the transistor 32 decreases, and the transistor 32 enters a state where it can be turned on. However, since the collector side of the transistor 32 has a high impedance, almost no current flows to the transistor 32, and for this reason, the relay
2 is never excited. Since the first relay 10 is self-held by the relay contact 10a, the welding power source and wire feeding continue.
Also, the supply of shielding gas is continued by the solenoid valve 14.

Next, the trigger switch 16 is turned on again to switch from normal welding conditions to crater welding conditions. Even in this ON state, the first relay 10 continues to be energized and the solenoid valve 14 continues to be driven. However, since the collector of transistor 32 is grounded via second relay 12, diode 54 and trigger switch 16, the second
The relay 12 is energized, and its relay contact 12a
is turned on and 12b is turned off. Therefore, the second relay 12 is self-held by the relay contact 12a, but the self-holding state of the first relay 10 is released by turning off the relay contact 12b. When the relay 12 is turned on, a relay contact (not shown) is activated, and the welding conditions of the welding machine are switched from normal welding to Creta welding.
Although the first relay 10 is released from self-holding, its energized state is maintained while the trigger switch 16 is turned on, and the welding machine continues welding the arc according to the crater welding conditions.

Next, the trigger switch 16 is turned off again to complete the welding. When the trigger switch 16 is turned off, the excitation of the relay 10 is canceled, and the supply of welding power and wire feeding are stopped. relay 10
The relay contact 10a is turned off by de-energization, and as a result, the excitation of the second relay 12 is also de-energized, and since the cathode side of the thyristor 38 also becomes high impedance, the thyristor 38 also becomes non-conductive. Then, the current flowing from the power source 18 to the resistors 26 and 28 also disappears, but the electric charge of the capacitor 22 flows to both resistors 26 and 28, and the transistor 30 is delayed in turning off for a certain period of time determined by this discharge current, and during this time the electromagnetic The valve 14 remains in the driven state, and after this fixed period of time has elapsed, the transistor 30 turns off, causing the electromagnetic valve 14 to be deactivated, and as a result, the supply of shielding gas to the welding area is also stopped. As described above, a series of welding processes in which the normal welding conditions are switched to the crater welding conditions is completed, and the circuit returns to the same state as before welding started.

Conventional sequence control circuits have the above configuration and function, but since the control circuit uses semiconductor switching elements such as transistors or thyristors, it is extremely easy to prevent noise from entering the base circuit of these control elements. However, this method had the disadvantage of causing sequence malfunctions. or,
The operating point of each semiconductor element mentioned above has a significant temperature dependence, and even if circuit constants are selected to obtain stable operation at a certain temperature, variations in the characteristics of each element may occur at other temperatures. The disadvantage was that stable operation could not be obtained due to this. Furthermore, conventional devices have the disadvantage that they require a lot of time to assemble due to the large number of parts, and that maintenance and inspection cannot be easily performed.

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide an improved arc welding sequence control circuit that can obtain a reliable sequence control function without malfunction without using semiconductor switching elements. It is in.

In order to achieve the above object, the present invention features a control circuit that performs arc welding sequence control using a relay and its contacts using a charging/discharging circuit including a capacitor.

Preferred embodiments of the present invention will be described below based on the drawings.

FIG. 2 shows a first preferred embodiment of the sequence control circuit according to the present invention, which includes a first relay 10 that controls the supply of welding power and the feeding of welding wire;
The second relay 12 that controls switching between normal welding conditions and crater welding exclusion conditions, the solenoid valve 14 that limits the supply of shielding gas, and the trigger switch 16 are the same as conventional ones, and the control circuit is controlled from a power source 18. Voltage is supplied. One end of the trigger switch 16 is connected to the first relay 10 and the solenoid valve 14 through diodes 56 and 58, and to the second relay 12 through a capacitor 60. A characteristic feature of the present invention is that the relay contact of the current detection relay that detects arcs in the welding part is used for sequence control, and in FIG. 2, the current control relay is the first relay contact. A normally open contact 62a and a second relay contact, normally closed contact 62b, are shown. One end of the normally open contact 62a is connected to the power supply 18,
The other end is connected to the first relay 10 via the normally closed contact 12b of the relay 12 and the diode 64, and is connected to the solenoid valve 14 via the diode 66, and to the second terminal via the normally open contact 12a of the relay 12. is connected to the relay 12 of. On the other hand, one end of the normally closed contact 62b of the current detection relay is connected to the power source, and the other end is connected to the second relay 12 via a resistor 68, which is a first resistor. Connection point between normally closed contact 62b and resistor 68 and trigger switch 1
A resistor 70, which is a second resistor, is connected to the connection point between the capacitor 6 and the capacitor 60.

The first embodiment of the present invention has the above configuration, and its operation will be explained below.

Before starting welding when the trigger switch 16 is in the OFF state, an excitation current flows from the power supply 18 to the relay 12 via the contact 62b and the resistor 68, but this excitation current must be set to a large resistance value of the resistor 68. Therefore, the excitation current is limited to an extremely small value, and the relay 12 is not driven by this exciting current. At this time, substantially the voltage of the power supply 18 is applied to both ends of the capacitor 60.

Trigger switch 1 to start arc welding
6 is turned on, and as a result, trigger switch 1
Excitation current is supplied from 6 to the first relay 10,
As in the conventional case, welding power supply and wire feeding are performed by relay contacts (not shown). Similarly, an exciting current is supplied from the trigger switch 16 to the solenoid valve 14 via the diode 58, and shielding gas is supplied to the welding section by driving the solenoid valve 14. FIG. 3 shows a sequence diagram in the first embodiment, showing a state in which the trigger switch 16 is turned on at time _t1 , and the first relay 10 and the solenoid valve 14 are driven at the same time. . Therefore, due to this state, an arc is generated in the welding part, and normal arc welding is started.

At time t ₂ in Fig. 3, the current detection relay is activated due to arc generation in the weld, and each relay contact 6
2a and 62b are operated in reverse. As a result, an exciting current is supplied to the first relay 10 through the current detection relay contact 62a, the contact 12b, and the diode 64, and similarly, the current detection contact 6 is supplied to the solenoid valve 14.
Since the excitation current is supplied through 2a and the diode 66, the relay 10 and the solenoid valve 14 continue to be driven even when the trigger switch 16 is turned off. Therefore, even if the trigger switch 16 is turned off at time _t3 , the above-described normal arc welding continues. In addition,
As described above before starting welding, the capacitor 60 is charged to almost the power supply voltage, so even when the trigger switch 16 is turned on, the second relay 1 is
No excitation current for driving the relay 12 flows through the second relay 12, and the second relay 12 maintains the state before welding starts.

The OFF operation of the trigger switch 16 at time _t3 does not reverse the states of the relays 10, 12 and the solenoid valve 14, but at the time of this OFF operation, since the current detection contact 62b is open, the capacitor The charge at 60 is discharged by a discharge circuit formed by resistors 68 and 70.

Next, at time _t4 , the trigger switch 16 is turned on again to switch between the welding condition and the crater welding condition. As described above, when the trigger switch 16 is in the ON state, the first relay 10 and the solenoid valve 14 are kept in the driven state, and the above-mentioned welding is continued, but in this state, the capacitor 60 is in the discharged state, so A charging current flows from the trigger switch 16 to the second relay 12 through the capacitor 60, and the relay 12 is excited and driven. Therefore, the relay contact 12a turns on and the relay 12
Self-holding is performed, and the welding conditions are switched to crater conditions by a relay contact (not shown).

The trigger switch 16 is turned off again at time _t5 , and since the relay contact 12b is opened by the excitation drive of the second relay 12 at this time, the self-holding of the first relay 10 is released and the welding power source is turned off. The supply and wire feed are stopped. Therefore, the arc at the welding part is extinguished, and as a result, the current detection relay is also de-energized and the relay contact 62a is opened. Therefore, the solenoid valve 14
The excitation drive is also stopped, and the supply of shielding gas is stopped. Further, by opening the current detection relay contact 62a, the self-holding of the second relay 12 is also released. When the current detection relay contact 62b is closed, the power supply voltage is applied to the capacitor 60, and the voltage across the capacitor 60 is charged to approximately the voltage of the power supply 18. Of course, this charging current is set to a relatively small value so that the relay 12 is not excited and driven, and for this purpose, the resistance value of the resistor 70 is set to an appropriate value. As above, the time
At t ₅ , the series of arc welding sequence operations is completed and the circuit can return to the same state as before welding started.

As described above, according to the embodiment of the present invention, a reliable sequence operation can be obtained by the charging/discharging operation of the capacitor and the current detection relay without using semiconductor switching elements, and malfunctions due to noise contamination or temperature changes can be obtained. It is possible to reliably prevent this.

FIG. 4 shows a second preferred embodiment of the present invention, in which the same members as those in the first embodiment are given the same reference numerals and their explanations will be omitted.

A characteristic feature of the second embodiment is that crater welding can be disabled if necessary, and for this purpose, the current detection relay contact 62a and each relay 1
A changeover switch 72 is provided between 0 and 12. The first contact 72a of the changeover switch is connected to the relay contacts 12a and 12b of the second relay 12, and the second contact 72b is connected via a diode 74 to the connection point between the current detection relay contact 62b and the resistor 68. There is.

When the changeover switch 72 is connected to the first contact 72a side, the circuit is exactly the same as that shown in FIG. 2, and switching control between the normal welding conditions and the arc welding conditions described in the first embodiment is performed. On the other hand, when the changeover switch 72 is connected to the second contact 72b side, the second relay 12 is not excited and driven even by the on/off operation of the trigger switch 16, and the crater welding conditions can be selected. First, only the sequence control of the normal welding operation is performed. Therefore, according to the second embodiment, crater welding can be arbitrarily selected.

A third embodiment of the present invention is shown in FIG.
The same members as those in the embodiment are given the same reference numerals, and the description thereof will be omitted.

The third embodiment is suitable for welding using a non-consumable electrode, and the magnitude of the welding voltage can be controlled by turning on/off the trigger switch 16. In the third embodiment, the first relay 10 is directly connected to a current detection relay contact 62a via a diode 64,
Further, a second relay 12 for switching and controlling the power supply voltage is connected to a trigger switch 16 via a relay contact 12a.

3 while referring to the sequence diagram in Figure 6 below.
The operation of the embodiment will be explained.

In the third embodiment, the first relay 10 is excited and driven by turning on the trigger switch 16a, and as a result, when arc welding is started, it is self-held by turning on the current detection relay contact 62a, and this self-holding is released. This is done by pulling the welding torch away from the base metal when the trigger switch 16 is in the OFF state, and forcibly extinguishing the arc. When the trigger switch 16 is turned on and off during the arc welding described above, the second relay 12 is excited and driven only in the on state, and during this time it is possible to obtain a separate welding voltage set arbitrarily. In the sequence diagram of FIG. 6, the shaded areas indicate the driving states of each relay, switch, and solenoid valve.

As explained above, according to the present invention, it is possible to obtain a sequence control effect without using conventional semiconductor switching elements, and it is possible to perform stable operation even in the presence of noise or temperature changes, and to prevent malfunctions. Therefore, it is possible to obtain a sequence control circuit with a small number of components.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a conventional arc welding sequence control circuit, Fig. 2 is a circuit diagram showing a preferred first embodiment of the arc welding sequence control circuit according to the present invention, and Fig. 3 is a circuit diagram showing the sequence of Fig. 2. 4 is a circuit diagram showing a second embodiment of the invention, FIG. 5 is a circuit diagram showing a third embodiment of the invention, and FIG. 6 is a sequence diagram in the third embodiment. The same members in each figure are given the same reference numerals, and 10 is a first relay for controlling the supply of welding power and wire feeding;
2 is a second relay for switching control between normal welding conditions and crater welding conditions, 14 is a solenoid valve that controls the supply of shielding gas, 16 is a trigger switch, 60 is a capacitor, and 62a and 62b are current detection relays. It is a point of contact.

Claims (1)

[Claims] 1. A trigger switch connected to a DC power source, which starts arc welding with the first operation and switches the welding conditions with the second operation; a first relay that supplies power and feeds the wire; an excitation circuit that excites the first relay by operating the trigger switch; and an excitation circuit that detects the occurrence of an arc in the welding part and operates the first relay during the arc occurrence period. a first current detection relay contact that maintains the trigger switch in an excited state; a capacitor connected to the trigger switch; a series circuit of a first resistor and a second resistor connected in parallel to the capacitor; A second current detection device connected to the connection point of the two resistors, charges the capacitor before the first operation of the trigger switch, detects the occurrence of an arc in the welding part, and maintains the capacitor in a discharged state during the arc occurrence period. A relay contact, a second relay that switches from normal welding conditions to crater welding conditions by controlling excitation, and when a charging current flows to the capacitor due to the second operation of the trigger switch, the charging current flows through the capacitor. energizing said second relay and then through said first current sensing relay contacts and self-holding contacts while the welding current is flowing or through said self-holding contacts during a second operation of said trigger switch; a circuit that maintains a second relay in an excited state, and performs sequence control of arc welding by operating the first and second current detection relay contacts and the capacitor in response to the operation of the trigger switch. Arc welding sequence control circuit.