JPH0671658B2 - Consumable electrode arc welding equipment - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an arc welding apparatus using a consumable electrode wire.

Conventional technology A method of starting an arc in automatic arc welding using consumable electrode wires is to start feeding at a relatively low speed with a high output for welding applied to the electrode wires, so that the electrode wires come into contact with the workpiece. A high-frequency high voltage is applied between the electrode wire and the work to be welded in addition to the welding power output, in which the tip of the electrode wire is melted and scattered by a large short-circuit current that flows to move to an arc. Then, a method of destroying the insulation of the gap between the two and performing an arc start is used. However, of these, the former has a poor success rate of arc start, especially when using a thick electrode wire such as submerged arc welding or when using a wire such as aluminum that has a small specific resistance and a small resistance heating due to a short-circuit current. Was extremely difficult. In addition, the latter method not only requires strengthening of the dielectric strength of the equipment, but it is unavoidable for its own malfunction due to the mixing of high frequency noise and inductive interference to peripheral equipment, resulting in many practical problems. Therefore, as a remedy for these problems, the electrode wire is fed until it comes into contact with the object to be welded, and by reversely feeding the electrode in the state where a short-circuit current flows, the two are forcibly separated once and the short-circuit is eliminated. A so-called retract start method has been proposed in which the electrode wire is forward-fed and transferred to normal arc welding while waiting for the growth of the generated minute arc. With this method, the success rate of arc start is relatively high. In particular, a system that supplies power from a power supply that supplies a small short-circuit current until the first short-circuit is detected, and that detects the contact between the electrode and the workpiece by the presence or absence of output current from this power supply, Since an excessive short-circuit current does not flow, there is no risk that the electrodes will be welded to the object to be welded, and relatively good results can be obtained. But,
Even when this method is used, there is some kind of insulator on the tip of the electrode wire or on the surface of the object to be welded, and the solution is when no electrical contact is detected despite mechanical contact between the two. Was not provided. That is, if there is an insulator such as slag, mill scale, or rust on the tip of the electrode wire or on the surface of the object to be welded, electrical contact will not be detected even if they are mechanically contacted. For this reason, the feeding is continued without the generation of an arc and the melting of the wire. Due to this continuous feeding of the electrode wire, the electrode wire buckles or slips occur in the feeding mechanism, and if neither of these occurs, the wire feeding force causes the welding torch to receive a reaction force and weld. The entire device will fall or be damaged. Moreover, in carbon dioxide arc welding and sub-aged arc welding, slag and oxides are always attached to the tip of the electrode wire at the end of the previous welding, and slag, spatter or spatter is also spread on the surface of the workpiece. There is an insulator such as a flat disk, and the above-described insulating state between the two is always in a state that can occur. For this reason, the inspection of the tip of the electrode wire and the surface of the object to be welded cannot be omitted prior to the start of welding, and complete unmanned operation was not possible.

An object of the present invention is to solve the above-mentioned drawbacks of the conventional apparatus, and even if an insulating state between the electrode and the object to be welded occurs during the feeding of the electrode wire, the welding apparatus is not hindered. The operation is safely stopped without coming, so that the welding device is not destroyed even if unmanned operation is performed.

SUMMARY OF THE INVENTION The present invention provides a wire touch detection circuit for detecting electrical contact between an electrode wire and an object to be welded, and a wire feed amount detector to detect a wire touch even when the feed amount reaches a predetermined amount. The above-mentioned problems are solved by providing a means for judging that the operation is abnormal when not performed.

Embodiment FIG. 1 is a connection diagram showing an embodiment of the apparatus of the present invention, FIG. 1 (a) shows the control unit of the welding power source and wire feeding / feeding motive, and FIG. 1 (b) is the same figure (a). The relay sequence connection diagram for control of is shown. In the figure, 1 is a welding power source, the output of which is determined by the output setters VR4 and VR5. 2 is a consumable electrode wire (hereinafter simply referred to as wire), 3
Is an object to be welded, 4 is a wire feeding electric motor, and 5 is a feeding roll driven by the wire feeding electric motor 4. 6 is a voltage detector, which is a contact signal AVR that is closed when the voltage between the wire 2 and the work piece 3 exceeds a certain level.
Reference numeral 7 is a current detector having a contact signal WCR which is activated when a small amount of current flows through the welding circuit. Reference numeral 8 denotes a control circuit for the wire feeding electric motor 4 so that the electric motor 4 is welded to the wire 2 when a command signal is input to the F terminal so that the rotational speed is determined by the setters VR1 to VR3. Controlling the speed and rotation direction so that the wire is rotated toward the object 3 (forward direction), and when the wire is input to the R terminal, the wire is pulled up (reverse direction). Is. CR1 to CR5 are relays, CR1a to CR5a are normally open contacts of these relays, and CR2b to CR5b are normally closed contacts. TD1 to TD3 are delay operation type timers, and TD1a and TD3a are timers TD1
And TD3 normally open contact, TD2b shows the timer TD2 normally closed contact. PB1 is a push button switch for starting welding, PB2 is a push button switch for stopping welding, and PB3 is a push button switch for resetting contact failure detection. PL is an indicator light that lights up when a contact failure is detected, and can be changed to a blinking display for alarms or a buzzer. 9 is an AC power supply and E is a DC power supply. Also, the output setting device VR5 is wire 2
Is to set the output voltage or output current so that a small current that does not melt the wire 2 when it contacts the object to be welded 3 is selected, and the setting target is selected according to the characteristics of the welding power source 1. The output setter VR4 sets the output at the time of welding, and as the welding output setter, a setter for reducing the output at the end of welding is also required, but the gist of the present invention is It is omitted for the sake of simplicity because it is not directly related. The setting device VR1 sets the wire feeding speed when the wire 2 is fed at a low speed toward the workpiece 3 at the start of welding.
2 is a setting device for setting the wire feeding speed during welding. The setting device VR3 is a setting device for giving a weak driving force to the electric motor 4 that does not substantially feed the wire 2 backward, and unlike the other two setting devices VR1 and VR2, the electric motor 4 is set.
The torque that is generated is set. Also the setting device VR
2 is the speed setter when the output of the welding power source is made high after this weak reversing operation and at the same time the wire is substantially fed backward, and the speed at which the wire is reversed to pull up the wire when contact failure is detected. It is also used as a setter.

In the embodiment shown in the figure, the welding start pushbutton switch PB
When 1 is pressed, relay CR1 is excited. The normally open contact CR1a closes due to the excitation of the relay CR1, and the output setter VR5 and setter V
R1 is connected to the welding power source 1 and the motor control circuit 8, respectively. As a result, an output capable of flowing a small short-circuit current is supplied between the wire 2 and the workpiece 3. Also electric motor 4
Rotates at a relatively low speed determined by the setting device VR1, and the wire 2
Is fed toward the work piece 3 to be welded. Wire 2
A short-circuit current flows when there is no insulator interposed when it contacts the object 3 to be welded. This short-circuit current is detected by the current detector 7 and the output contact WCR operates. Relay CR2 is excited by the operation of this contact WCR, and the normally closed contact of this relay CR2
The setter VR1 is disconnected by CR2b, and the setter VR3 is connected to the R terminal of the motor control circuit 8 by the normally open contact CR2a. For this reason, the electric motor 4 stops normal rotation, rotates in reverse according to the set value of the setting device VR3, and rotates in the direction of pulling up the wire 2. However, since the setting value of the setting device VR3 is set to a value that gives a weak driving force as described above, the electric motor 4 is inertial at the time of forward feeding of the backlash and the wire 2 of the reduction mechanism connected to the electric motor 4. Therefore, the reverse rotation is performed only during a very light load state until the force pressed against the workpiece 3 is canceled, and when the wire is actually fed back, a large driving force is required, so the electric motor 4 The wire does not rotate more than the above, and the wire is not substantially pulled up, and the wire is kept in very light contact with the object to be welded. Meanwhile relay
Since the normally open contact CR2a of CR2 also excites the timer TD3, the timer TD3 also starts the time limit at the same time as the reverse rotation command of the electric motor 4.
Relay C when contact TD3a is closed due to the expiration of timer TD3
R4 is excited, and the contacts CR4a and CR4b of the relay CR4 switch the output setter from VR5 to VR4 and also the setter of the motor control circuit 8 from VR3 to VR2.
As a result, the output of the welding power source 1 becomes a high output required for welding, and the feeding speed of the wire 2 is rapidly increased to the high speed determined by the setting device VR2. By this back feeding, the contact between the wire 2 and the work piece 3 is eliminated, and an arc is generated by the high output of the welding power source 1 supplied at this time. At this time, the contact pressure between the wire 2 and the object to be welded 3 is almost zero due to the weak reverse drive, and since there is no backlash in the feeding mechanism, the supply power is not changed. The delay of the wire pulling operation is extremely small, and the tip portion of the wire 2 is easily melted and transferred to the arc. The arc grows when the reverse feed continues in this state, and when the arc voltage at this time becomes higher than the set voltage of the voltage detector 6, the contact AVR is closed. As a result, the relay CR5 is excited, and the input of the motor control circuit 8 is switched from R to F by the contacts CR5a and CR5b.
As a result, the rotating direction of the electric motor 4 is reversed, the wire 2 is forwardly fed at a speed determined by the setting device VR2, and normal welding is started.

The apparatus of the embodiment shown in FIG. 1 operates as described above in the normal state, but if the wire 2 is fed at the first low speed wire feeding,
If the wire and the work piece 3 are insulated from each other for some reason, the contact WCR of the current detector 7 does not work because the short-circuit current cannot flow even if the wire mechanically contacts the work piece. Become. For this reason, the wire will continue to be fed, but when the contact TD1a closes due to the end of the timer TD1 that was excited at the same time as the closing of the welding start pushbutton switch, relay CR3 is excited and relay CR3 Normally open contact
Self-held by CR3a. At the same time, contact CR
The input signal to the F terminal of the electric motor control circuit is cut off by 3b, and the electric motor 4 stops the forward feeding of the wire.
An indicator PL connected in parallel with the relay CR3 displays a warning of poor wire contact. Further, the output of the setting device VR2 is supplied to the R terminal through the relay contact CR3a to the electric motor control circuit 8 until the time limit of the timer TD2 ends, the electric motor 4 reverses at high speed, and the wire 2 is pulled up. Once a poor wire contact is detected, the relay CR3 is held by itself, and other operations cannot be performed until the reset pushbutton switch PB3 is pressed. Therefore, after the operator inspects and corrects the wire tip and the surface condition of the work piece, the reset push button switch PB3
After pressing, the welding start push button switch PB1 will be pressed again to restart. As can be easily understood from the above operation, the time period of the timer TD1 is set to be slightly longer than the time from the wire feeding start to the contact (usually about 0.3 to 3 seconds), and the time period of the timer TD2 is set to the wire in the contact state. The time required to return the to approximately the original position (usually 0.
The timer TD3 may be set to 0.5 seconds to several seconds, as long as it is longer than the time required to eliminate the backlash of the feeding mechanism, and a strict timer is not necessary. These timers are respectively for obtaining the required wire feeding amount or the driving amount of the wire feeding mechanism, and their respective settings require changing the time period according to the corresponding wire feeding speed. is there. Instead of these timers, if the actual wire feeding amount is obtained by comparing the number of rotations of the wire feeding mechanism and the feeding speed with the feeding time, and it is compared with the preset value, more accurate control is possible. It will be possible.

In the embodiment shown in FIG. 1, when the timer TD2 is provided and the wire contact failure is detected, the wire is automatically pulled up for a predetermined time. However, when the timer TD2 is not provided, the wire contact failure is detected. At times, the wire feeding mechanism stops immediately and maintains the state at the time of detection. Therefore, it becomes easier to determine the cause of poor wire contact, and when the operator can easily see the weld, the timer
In some cases, it may be better not to perform automatic pulling except for TD2. In this case, the operator may manually reverse the wire by a push button switch (not shown) by manual operation. In addition, the timing of wire feeding, reverse feeding, speed change, output switching of welding power source, etc. is arbitrary, and processes such as temporary stop and confirmation restart command and automatic restart after temporary stop are added during each operation. Alternatively, other operations necessary for welding such as release of shield gas, sprinkling of flux, and movement of welding torch may be performed in conjunction with these operations.

In the embodiment shown in FIG. 1, the arc start operation is interrupted as soon as the wire contact failure is detected. However, the insulation state between the wire and the workpiece is not affected by a relatively slight impact. In many cases, this is due to the insulator being destroyed. Therefore, when a wire contact failure is detected, the arc start operation is not immediately interrupted, but if the wire is pulled up and the arc start operation is restarted from the beginning, the insulation state will be canceled by the impact of the wire contact again. And good arc start may be performed. A second invention of the present invention proposes a device provided with a repeating circuit for repeating an arc start operation when a defective wire contact is detected. FIG. 2 shows a connection diagram of the embodiment. The apparatus shown in FIG. 1 has a preset counter CU1 which counts the number of occurrences of wire contact failure and a relay CR6 which is excited when the count value of the preset counter reaches the preset value in the embodiment shown in FIG. In addition, the relay CR3 and the self-holding circuit of timer TD2 are removed, and the excitation of timer TD1 is interrupted by the normally closed contact of timer TD2. It is provided with a repetitive circuit that is designed to be performed from the beginning.

In the operation of the embodiment shown in FIG. 10, the operation when the wire contact is normally made is exactly the same as that of the embodiment shown in FIG. The operation will be described. When the pushbutton switch PB1 is pressed to excite the relay CR1 and the wire 2 is fed toward the workpiece 3 at the low speed determined by the setter VR1, even if the time limit of the timer TD1 is reached. If the current detector 7 still does not detect any current and the contact WCR is not operating, the relay CR3 and the timer TD2 are excited because of the wire contact failure. As a result, the input of the control circuit 8 is switched from the F terminal to the R terminal and the setting device is also changed from VR1 to VR2, and the wire 2 is pulled up at a speed determined by the setting device VR2. When the normally closed contact TD2b opens due to the end of the timer TD2, the timer TD1 is de-energized and the normally open contact TD1a is immediately opened to deactivate the relay CR3 and the timer TD2. Therefore, the normally closed contact of the timer TD2 is restored, the timer TD1 is excited again, and the state returns to the initial state in which the push button switch PB1 is pushed. At this time, due to the return of the relay CR3, the input of the control circuit 8 is again supplied with the output of the setting device VR1 to the F terminal, and the low speed normal feeding is performed. If the contact WCR of the current detector 8 does not operate within the time limit of the timer TD1 due to this re-forward feed, the relay CR3 and the timer TD2 are excited again and the pulling up and re-feeding of the wire 2 are repeated. .
At this time, each time the relay CR3 is excited, the preset counter CU1 counts by the contact CR3a, and when this count value matches the preset number, the relay CR6 connected to the output terminal is excited and the relay CR1 Is de-energized and the subsequent operation is interrupted.

Since the embodiment shown in FIG. 2 operates as described above, even if a wire contact failure is detected, the wire is automatically pulled up and the arc start operation is repeated a predetermined number of times, so that a slug is attached to the tip of the wire. In the case where the insulation state is relatively weak, as in the case described above, the arc start is performed without interrupting the welding. Also, if this insulation state is due to a strong insulator, it stops after a predetermined number of trials, so excessive repetition can be prevented, the tip of the wire can be deformed, and the wire feeding mechanism can be overloaded. There is no risk to

In each of the above-described embodiments, it is more effective to swing the wire parallel to the surface of the object to be welded with a slight width at the time of contact detection during wire feeding. In particular, when the present invention is applied to the arc welding robot of the teaching play back system, the movement path of the welding torch can be arbitrarily taught, so that the optimum swing locus can be drawn and the effect of the present invention can be more effectively exhibited. Is.

Further, the device of the present invention is not limited to the one having a contact relay as shown in the drawing, but may be a logic circuit using a semiconductor integrated circuit or the like.

As described above, in the present invention, in the consumable electrode type arc welding apparatus that performs the retract start method in which the wire is once brought into contact with the object to be welded and then forcibly pulled up to generate the arc, the wire is fed by a predetermined amount. Since a judgment circuit is provided to judge contact failure when no contact is detected despite the fact that the wire is supplied, the tip of the wire and the surface of the work to be welded, such as with conventional equipment, are made of an insulating material such as slag, rust, or flux. Even if there is a wire, it is no longer necessary to continue feeding the wire as a process for contact detection, and it is possible to prevent the occurrence of wire buckling and tipping or damage of the welding equipment. Welding can be performed safely in a narrow space where it is difficult to see, and accidents at the start of an arc can be prevented, so complete unmanned operation is possible.

[Brief description of drawings]

1 (a) and 1 (b) are connection diagrams showing an embodiment of the device of the present invention, and FIGS. 2 (a) and 2 (b) are connection diagrams showing another embodiment of the present invention. 1 ... Welding power source, 2 ... Wire, 3 ... Workpiece, 4 ...
... motor, 6 ... voltage detector, 7 ... current detector, 8 ...
… Motor control circuit, CU1 …… Preset counter

Claims (12)

[Claims] 1. A wire touch detection circuit for detecting electrical contact between a consumable electrode wire and an object to be welded, and a signal for detecting that a predetermined amount of the consumable electrode wire has been fed from a welding start command. The feed amount detecting means for outputting and the wire contact failure when only the output of the feed amount detecting means is outputted at the time of welding start and the contact detection signal between the electrode wire of the wire touch detecting circuit and the workpiece is not outputted. Consumable electrode type arc welding device with a judgment circuit for judging. 2. The wire feed amount detecting means determines the feed length from the start of wire feed as the wire feed time, the rotation speed of the wire feed mechanism or the wire feed speed and feed time. Claim 1 which is means for detecting by any of the products
The consumable electrode type arc welding apparatus as described in the paragraph. 3. The wire touch detection circuit, after detecting the electrical contact between the consumable electrode wire and the object to be welded, pulls up the consumable electrode wire once to generate a wire back-feed command signal for generating an arc. The consumable electrode type arc welding device according to claim 1, which is an output circuit. 4. The wire touch detection circuit supplies electric power for flowing a small short-circuit current between the consumable electrode wire and an object to be welded so as not to melt the consumable electrode wire by adjusting an output of a welding power source. The consumable electrode type arc welder according to claim 1, which is a circuit for detecting contact between the consumable electrode wire and the object to be welded by circulating a short-circuit current. 5. The wire back-feeding command signal includes a first command signal that causes a wire feeding mechanism to perform a back-feeding operation that does not substantially feed back the consumable electrode wire for a certain period of time; 4. The consumable electrode type arc welding device according to claim 3, which is a signal including a second command signal that causes the consumable electrode wire to be substantially back-fed for a certain period of time after the end of the command signal of. 6. The electric power supplied between the consumable electrode wire and the object to be welded is such a short circuit current that does not melt the consumable electrode wire until the second command signal is supplied. The consumable electrode type arc welding device according to claim 5, which is electric power and is switched to electric power having a value suitable for arc welding after the second command signal is supplied. 7. A wire touch detection circuit for detecting electrical contact between a consumable electrode wire and an object to be welded, and a signal for detecting that a predetermined amount of the consumable electrode wire has been fed from a welding start command. The feed amount detecting means for outputting and the wire contact failure when only the output of the feed amount detecting means is outputted at the time of welding start and the contact detection signal between the electrode wire of the wire touch detecting circuit and the workpiece is not outputted. A consumable electrode having a judging circuit for judging, and a repeating circuit for resetting the feed amount detecting means by a contact failure output of the judging circuit and for feeding back the consumable electrode wire by a predetermined amount and then forward-feeding again. Type arc welding equipment. 8. The circuit according to claim 3, wherein the repeating circuit is a circuit for stopping the arc starting operation when a defective wire contact is still detected even after repeating the arc starting operation a predetermined number of times. The consumable electrode type arc welding device described. 9. The wire touch detection circuit, after detecting the electrical contact between the consumable electrode wire and the object to be welded, temporarily pulls up the consumable electrode wire to generate a wire reverse feed command signal for generating an arc. The consumable electrode type arc welding device according to claim 7 or 8, which is an output circuit. 10. The wire touch detection circuit supplies electric power for flowing a small short-circuit current between the consumable electrode wire and an object to be welded so as not to melt the consumable electrode wire by adjusting an output of a welding power source. The consumable electrode type arc welder according to claim 7, which is a circuit for detecting contact between the consumable electrode wire and the object to be welded by flowing a short-circuit current. 11. The wire back-feeding command signal includes a first command signal that causes a wire feeding mechanism to perform a back-feeding operation that does not substantially feed back the consumable electrode wire for a certain period of time. 10. The consumable electrode type arc welding device according to claim 9, which is a signal including a second command signal that causes the consumable electrode wire to be substantially back-fed for a certain period of time after the end of the command signal. 12. The electric power supplied between the consumable electrode wire and the object to be welded is such a short circuit current that does not melt the consumable electrode wire until the second command signal is supplied. 12. The consumable electrode type arc welding apparatus according to claim 11, which is electric power and is switched to electric power of a value suitable for arc welding substantially at the same time as the supply of the second command signal.