JPS6247628B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for detecting wire stakes in arc welding.

Conventional automatic arc welding machines adjust the voltage and current to prevent welding between the welding wire and the welding base metal (hereinafter referred to as wire stay) at the end of welding. If the wire stick is caused, the welding torch will be moved to the next welding location, causing damage to the equipment, or the welding torch may be bent, which may cause the welding position to change. Welding defects sometimes occurred.

It takes a lot of time to restore equipment that has been damaged due to wire stays to its original state, which reduces the operating rate of automatic arc welding machines and makes it difficult to automate arc welding. It was becoming.

One object of the present invention is to propose a method for detecting the occurrence of wire stuck at the end of welding in arc welding.

The wire stay detection method in arc welding of the present invention involves applying a DC voltage lower than the welding voltage and having the opposite polarity to the welding voltage between the welding torch and the welding base material, and detecting the presence or absence of current based on the welding voltage. The present invention is characterized in that the presence or absence of wire stuck is detected by detecting the presence or absence of a current based on the DC voltage of opposite polarity after the completion of welding. be.

Another object of the present invention is to provide a device for detecting the occurrence of wire sticks at the end of welding in arc welding.

The wire stay detection device in arc welding of the present invention includes a DC voltage source that applies a DC voltage lower than the welding voltage and of opposite polarity to the welding voltage between the welding torch and the welding base material, and a DC voltage source that is based on the welding voltage. A first detection circuit that detects the completion of welding based on the presence or absence of current and generates a signal indicating the end of welding, and a second detection circuit that detects the presence or absence of current based on the DC voltage of opposite polarity after welding is completed. and an output circuit that outputs a signal indicating whether or not a wire stake is generated at the end of welding in response to the presence or absence of current based on the DC voltage of opposite polarity and the signal indicating the end of welding. The present invention is characterized in that it is provided in two detection circuits.

Hereinafter, the present invention will be explained based on the drawings. 1st
Figures a, b, and c are circuit diagrams for explaining the method and apparatus of the present invention.

In the figure, 1 is a welding voltage source that supplies welding voltage, and 2 is a start switch of the welding device. The arc between the welding torch and the welding base metal is shown by an equivalent circuit of a variable resistor 3 and a switch 4, and the presence or absence of wire sticking is shown by turning on or off the switch 5.

According to the present invention, a DC voltage E, which is smaller than the welding voltage V and has the opposite polarity to the welding voltage, is applied between the welding torch and the welding base material by the DC voltage source 6 through the resistor 7. Further, a first detection circuit 8 is connected between the welding torch and the welding base metal via a diode 9, which detects the completion of welding based on the presence or absence of current based on the welding voltage V and generates a signal indicating the completion of welding. , and a second detection circuit 10 that detects the presence or absence of current based on a DC voltage E of opposite polarity after welding is completed, are connected via a diode 11. The diode 9 is connected in a forward direction relative to the welding voltage V, and the diode 11 is connected in a reverse direction relative to the welding voltage V.

FIG. 1a shows a state in which the switch 2 is turned on and the welding voltage V is applied. In this case, arc welding is being performed, so switch 4 is on.
Switch 5 is off because the wire stake is not activated. Since the welding voltage V is sufficiently larger than the reverse polarity DC voltage E, the welding current _I1 flows from the welding wire to the welding base material to perform arc welding. During welding, reverse polarity DC voltage source 6 and resistor 7
A current I ₂ flows through the welding voltage V due to the welding voltage V, and since a forward voltage is applied to the diode 9, a current I ₃ flows through the first detection circuit 8 and the diode 9 due to the welding voltage V. On the other hand, since a reverse voltage is applied to the diode 11, no current flows through the second detection circuit 10.

FIG. 1b shows a state in which the switch 2 is turned off, welding is completed, and no wire stuck occurs, that is, a normal state. In this case, since there is no arc or wire stake, switches 4 and 5 are both off. Since switch 2 is turned off, currents I ₁ , I ₂ ,
I ₃ no longer flows. Further, since a reverse voltage is applied to the diode 9 due to the DC voltage E, no current based on the DC voltage E flows through the first detection circuit 8. Therefore, in the first detection circuit 8, the current
By detecting the presence or absence of _I3 , it is possible to determine the end of welding and generate a signal indicating the end of liquid contact.

Since a forward voltage is applied to the diode 11 due to the DC voltage E, a current I ₄ based on the DC voltage E flows through the second detection circuit 10 . On the other hand, as shown in FIG. 1c with switch 5 in the ON state, if a wire stuck occurs, current _I5 flows through switch 5, resulting in a voltage drop across resistor 7 corresponding to the magnitude of voltage E. Therefore, no voltage is applied to the diode 11 and no current I ₄ flows through the second detection circuit 10.

In this way, if no wire stake has occurred at the end of welding, current will flow through the second detection circuit 10, and if a wire stake has occurred, no current will flow through the second detection circuit 10. By detecting the presence or absence of this current in the circuit 10, it is possible to determine whether a wire stuck is occurring.

The first detection circuit 8 generates a signal indicating the end of welding, and in synchronization with this signal, an output circuit provided in the second detection circuit 10 can output a signal indicating the occurrence of wire stuck.

Next, an embodiment of the wire stake detection device for arc welding according to the present invention will be described with reference to FIG. In FIG. 2, circuit elements similar to those shown in FIG. 1 are designated by the same numbers.

A welding power source 1 of an automatic arc welding machine includes a transformer 12 that steps down a three-phase AC voltage, and thyristors 13 and 1.
It consists of a full wave rectifier using thyristors 4 and 15, and a phase control device 16 for each thyristor. Welding voltage V
is controlled by setting the variable resistor 17 in the phase control device 16. This controlled welding voltage V is applied between the welding torch 20 and the welding wire 21 and the welding base metal 22 via the welding voltage terminals 18 and 19, causing arc discharge between the wire and the welding base metal. The resulting base metal is welded. During this time, the wire 21 is fed by the feeding device 23.

The above is an overview of the automatic arc welding machine, but the wire stake that is a problem in the present invention occurs at the end of welding.

According to the present invention, the welding torch 20 and the welding base material 2
1, a DC voltage E smaller than the welding voltage V and having a polarity opposite to the welding voltage is applied by a DC voltage source 6 through a resistor 7. The DC voltage source 6 includes a single-phase transformer 24, a bridge rectifier 25, and a smoothing capacitor 26. The side output terminal of the DC voltage source 6 is connected to the side welding voltage terminal 19 via the resistor 7, and the side output terminal of the DC voltage source 6 is connected to the side welding voltage terminal 18. Welding voltage terminal 19,
Connected to the first detection circuit 8 via the Zener diode 27 and the diode 9, and the diode 1
1 to the second detection circuit 10. The second detection circuit 10 includes an output circuit 28 that outputs a signal indicating the occurrence of wire stuck in synchronization with the output signal from the first detection circuit 8.

Before welding starts, the starting switch 2 connected to the phase control device 16 is turned off (FIG. 3a), and a negative voltage is applied between the welding voltage terminals 18 and 19 by the DC voltage source 6. (Figure 3b,
c). Also, the transistor 29 of the second detection circuit 10
Since a positive voltage is applied from the DC voltage source 6 through the diode 11 and the resistor 30, the transistor 29 is turned on (FIGS. 3d and 3e).

When the switch 2 is turned on, the phase control device 16 controls the gates G ₁ of the thyristors 13, 14, 15,
When a trigger signal is input to G ₂ and G ₃ , a positive welding voltage V is applied to welding voltage terminals 18 and 19 (FIGS. 3b and 3c). When the wire 21 is sent by the wire feeding device 23 and comes into contact with the base material 22, the welding voltage _I1 flows and arc welding is started. During welding, welding voltage and wire feed are controlled to satisfy welding conditions.

When welding voltage is applied to terminals 18 and 19, terminal 18 → connection point 31 → bridge rectifier 25 → resistor 7 → connection point 32 → terminal 19 → neutral point 33 of the secondary winding of transformer 12 → thyristor 13 ,14,15→
Current I ₂ flows in the closed circuit of terminal 18 . At the same time, a forward voltage is applied to the diode 9 through the circuit consisting of the terminal 18 → connection point 31 → connection point 34 → bias power supply 35 → resistor 36 → resistor 37 → diode 9 → Zener diode 27 → terminal 19, and the forward voltage is applied to the Zener diode 27. As a result of the applied breakdown voltage, said circuit and terminal 19 → neutral point 3 of the transformer secondary winding
Current I ₃ flows through 3→thyristors 13, 14, 15→terminal 18, turning on transistor 40. For this reason, diode 41→transistor 4
0→The capacitor 43 is charged via the resistor 42, and as a result, the terminal voltage of the capacitor 43 is supplied to the base of the transistor 45 via the resistor 44, and the transistor 45 is turned on with a delay of time _t1 from the time when the transistor 40 is turned on ( Figure 3 f).

On the other hand, when the welding voltage is applied to the terminals 18 and 19, a reverse voltage is applied to the diode 11, so that no positive voltage is applied to the base of the transistor 29 of the second detector 10, and the transistor 29 is turned off. (Fig. 3 d, e).

The above is the state during welding. Welding ends when switch 2 is turned off and welding voltage V is no longer applied to welding voltage terminals 18 and 19. At this time, if there is no stay between the wire 21 and the base metal, that is, in a normal state, a DC voltage of opposite polarity is applied between the welding voltage terminals 18 and 19 by the voltage source 6, so that the welding voltage is negative. voltage (Figure 3b). Therefore, since a forward voltage is applied to the diode 11, the diode 11 is turned on, and as a result, the transistor 29 of the second detection circuit 10 is turned on (FIG. 3d). At this time, rectifier 25 → resistor 7 → diode 11 → resistor 30 → base of transistor 29 → emitter of transistor 29 → rectifier 25
Current I ₄ flows through . In addition, the transistor 29
is on, so the voltage at the collector terminal 46 of the transistor 29 is equal to the ground potential.

On the other hand, if wire stuck occurs, the rectifier 25 → resistor 7 → terminal 19 → base material 22 → wire 21 → welding torch 20 → terminal 18 → rectifier circuit 2
A current I 5 flows through the current I ₅ . As a result of the DC voltage E being canceled by the voltage drop caused by the resistor 7, the voltage between the welding voltage terminals 18 and 19 becomes zero (FIG. 3c). In this case, the transistor 29 is not turned on and remains off (FIG. 3e). Therefore, the current I ₄ does not flow. Also, since the transistor 29 is off, the collector terminal 4 of the transistor 29
6, a positive voltage is generated via a bias power supply 35 and a resistor 47.

In addition, the switch 2 connected to the phase control device 16
is turned off and the welding voltage V is no longer applied to the welding voltage terminals 18 and 19, the current _I3 does not flow in the first detection circuit 8 and the transistor 40 is turned off. When transistor 40 is turned off, capacitor 43 is discharged through resistor 50 and transistor 45 is turned off with a delay of time t ₂ from the time when transistor 40 is turned off (FIG. 3f). transistor 45
When the capacitor 53 is turned off, the capacitor 53 is charged through the resistors 51 and 52, so that the transistor 54 is turned on only for a period _t3 (FIG. 3g). During the ON period of the transistor 54, the potential of the connection point 57 between the resistors 55 and 56, that is, the collector terminal of the transistor 54 becomes the ground potential, indicating that welding is completed. This signal indicating the end of welding is supplied to the base of transistor 58 via resistor 56, turning off transistor 58, which has been on until now, for a period _t3 .

At the end of welding a wire stay has occurred and therefore the transistor 29 of the second detection circuit 10
If a positive voltage is generated at the collector terminal 46 of
This positive voltage is supplied via node 59 and resistor 60 to the base of transistor 61 for period _t3 .
Transistor 61 is turned on only during _t3 . When transistor 61 is turned on, latch relay 62 is turned on (FIG. 3h), turning on relay contact 63 and outputting a signal to output terminals 64 and 65 of output circuit 28 indicating the occurrence of wire stuck. This signal is synchronized with the signal indicating the end of welding. This signal can activate a display device or the like (not shown) and prevent the next welding process from starting. To release the latch relay 62,
This is done by turning on switch 66 and turning on reset relay 67. If no wire stuck occurs at the end of welding, the second detection circuit 10
No positive voltage is generated at the collector terminal 46 of the transistor 29, and even though the transistor 58 is turned off for the period _t3 , the transistor 61 is not turned on. does not occur.

As explained above, according to the method and device for detecting wire stakes in arc welding of the present invention, the occurrence of wire stakes can be easily detected, so that the operating rate of the welding equipment can be improved. Furthermore, the device of the present invention does not require any modification to the structure of the automatic arc welding machine itself, and has the advantage that it can be added to a conventional automatic arc welding machine to utilize the existing electrical system of the automatic arc welding machine. have.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram for explaining the method and device of the present invention, Fig. 2 is a circuit diagram showing an embodiment of the device of the present invention, and Fig. 3 is a voltage diagram for explaining the operation of the device of Fig. 2. Waveform diagram and on/off of transistors, etc.
FIG. 3 is a diagram showing an off state. 1... Welding voltage source, 2, 66... Switch, 6
...DC voltage source, 7, 37...Resistor, 8...1st
Detection circuit, 9, 11... Diode, 10... Second detection circuit, 12, 24... Transformer, 16... Phase control device, 18, 19... Welding voltage terminal, 20
...Welding torch, 21 ...Welding wire, 22...
...Base material, 28... Output circuit, 29, 40... Transistor, 35... Bias power supply, 43, 53...
...Capacitor, 62...Latch relay, 64,6
5...Output terminal.

Claims (1)

[Claims] 1. Applying a DC voltage lower than the welding voltage and having the opposite polarity to the welding voltage between the welding torch and the welding base material, and detecting the presence or absence of current based on the welding voltage to terminate welding. Detection of wire stay in arc welding, characterized in that the presence or absence of wire stay is detected by determining the presence or absence of a current based on the DC voltage of opposite polarity after welding is completed. Method. 2. A DC voltage source that applies a DC voltage lower than the welding voltage and of opposite polarity to the welding voltage between the welding torch and the welding base metal, and detecting the end of welding based on the presence or absence of current based on the welding voltage and welding. a first detection circuit that generates a signal indicating the end of welding, and a second detection circuit that detects the presence or absence of a current based on the DC voltage of opposite polarity after welding is completed, arc welding, characterized in that the second detection circuit is provided with an output circuit that outputs a signal indicating the presence or absence of a wire stay at the end of welding in response to the presence or absence of the welding and the signal indicating the end of the welding. Wire stake detection device.