JPS63268571A - Consumable electrode type arc welding machine - Google Patents

Abstract

PURPOSE:To improve an arc starting and to constrain the generation of a spatter by stopping the work of a short circuit detector by a 2nd time counter at the time of a welding actuation and performing the rise of an actuation current from the moment when a consumable electrode is short-circuited with the body to be welded. CONSTITUTION:A driving circuit 32 turns off 1st switching elements 3a, 3b, for instance, at the time of inputting the detection signal from a short-circuit start detector 30, i.e., at the time of starting the short-circuit. And no feeding of the outputs from all of the switching elements 3a, 3b, 4a, 4b is performed until receipt of the signal from a 1st time counter 31. The energy accumulated in a DC reactor 6 is released and a short-circuit current is slightly flowed. The driving circuit 32 then turns off the 2nd switching elements 4a, 4b when the signal from the 1st time counter 31 is inputted to feed the short-circuit current in the direction reverse to the polarity prior to the short-circuit. A rest time is provided for the change-over of the switching elements 3a, 3b, 4a, 4b of a polarity switch 29, the transfer of droplet is smoothly effected and the generation of spatters is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is a consumable electrode type in which welding is performed by switching the polarity of the welding output supplied from the consumable electrode to the workpiece between positive and reverse polarity during welding. This relates to arc welding machines.

Conventional technology Conventionally, this type of equipment has adopted a method in which the polarity is switched immediately when a short circuit is detected by a short circuit detector that detects a short circuit between the consumable electrode and the workpiece. The polarity switching inside was also done in the same way. Fifth
The figure shows an example of the configuration of a conventional consumable electrode type arc welding machine of this type. In FIG. 5, l is a DC voltage source that supplies power to the polarity switch 2. In FIG. Recently, an inverter has been used as the DC voltage source l.

The polarity switch 2 includes first switching elements 8a, 8b which supply a positive polarity output to the welding load, and second switching elements 4a, 4b which supply a reverse polarity output to the welding load.
and these first switching elements 8a.

8b and a drive circuit 5 for switching the second switching elements 4a and 4b, and the output of this polarity switch 2 is connected in series with a DC reactor 6, a power supply chip 7, and a consumable electrode 8 which is the welding load. and the workpiece 9 are connected. IO is a short circuit detector that detects a short circuit between the consumable electrode 8 and the workpiece 9 and outputs this detection signal to the drive circuit 5. With these configurations, when welding is started, the drive circuit 5 switches between the first switching elements 8a and 8b.
Alternatively, the second switching elements 4a and 4b are driven to supply welding output to the consumable electrode 8 and the workpiece 9, and as soon as the consumable electrode 8 is short-circuited with the workpiece 9 and the short circuit detector IO detects the short circuit. , the first switching element Ha a
sb and the second switching element 4a*4b are switched by the drive circuit 5 to switch the polarity of the welding output supplied to the consumable electrode 8 and the workpiece 9.

Problems to be Solved by the Invention However, in the conventional configuration, the polarity is immediately switched when a short circuit is detected, so there is a drawback that the consumable electrode 8 does not smoothly transfer the droplets melted by the arc to the melting boob. Ta. This will be explained with reference to FIG. FIG. 6 shows the behavior of the consumable electrode 8 immediately before and after a short circuit between the consumable electrode 8 and the workpiece 9,
This figure shows the relationship between droplet transfer, welding current, and welding voltage waveforms. In Figure 6, ll is a droplet, 12 is f
F3 shows the welding current and welding voltage waveforms, respectively, using a conventional device. As shown in FIG. 6, the droplet 11 of the consumable electrode 8 melts into the melting bubble
In the conventional device, the short-circuit current immediately rises rapidly at time A immediately after the short-circuit with The weld metal of the boule 12 was severely pierced, and a large amount of spatter was scattered and adhered to the surface of the workpiece 9, resulting in poor welding finish.

The present invention solves the above problems, and aims to provide a consumable electrode type arc welding machine that reduces the occurrence of spatter immediately after a short circuit and improves the welding finish.

Means for Solving the Problems In order to solve the above problems, the present invention provides a short circuit start detector that detects the point in time when the consumable electrode starts shorting to the workpiece, and a detection signal from the short circuit start detector. A first timer counts the time from the start of the short circuit until the droplet is securely transferred to the molten pool, and a timer counts the time from the start of welding startup.

a second timer that commands the short circuit start detector to stop operating from the start of welding until the arc start is completed;
Stopping or reducing the supply of welding output to the consumable electrode and the workpiece according to the detection signal of the short circuit start detector,
The apparatus is equipped with a polarity switching device that switches the polarity of the welding output and starts or increases the supply of the welding output based on the output signal after the time limit of the first timer.

Further, a second invention is the same as that of the first invention, by adding an output polarity ratio setting device for outputting a ratio setting signal of a positive polarity output and a reverse polarity output of the welding output to the polarity switch. .

Further, an eighth invention is a direct current 1! of the configuration of the first invention! an inverter connected to a commercial power source to perform frequency conversion; a welding isolation transformer to which the output of the inverter is connected to the primary side; and a welding isolation transformer connected to the secondary side of the welding isolation transformer to perform AC/DC conversion. In addition, an output polarity ratio setting device that sets the ratio of the positive polarity output and reverse polarity output of the welding output, and a polarity switching device that is connected to the polarity switching device and the output polarity ratio setting device and setting the polarity switching device. A synchronization circuit is added that outputs the output ratio signal of the output polarity ratio setter to the inverter in synchronization with the switching signal.

Effect: With the configuration of the first invention described above, at the start of startup, the second timer stops the operation of the short circuit start detector from the start of startup until the completion of arc start, eliminates polarity switching, and uses the polarity switch to The starting current is immediately raised to prevent a faulty arc start, and after the arc start is completed, the short circuit start detector is activated, and after the short circuit detection signal is input by the polarity switch, the output signal of the first timer is changed. is input, that is, until the consumable electrode and the workpiece are short-circuited and the droplets are reliably transferred to the molten boob V, the supply of welding output is stopped or reduced to reduce the occurrence of spatter,
The polarity of the welding output is switched by inputting the output signal of the first timer, and the supply of the welding output is restarted or increased.

In the second invention, in addition to the effect of the first invention, the ratio between the positive polarity output and the reverse polarity output is changed by the polarity switch according to the output polarity ratio setting signal of the output polarity ratio setting device.

In the eighth invention, in addition to the effect of the first invention, the output polarity ratio setting signal is synchronized with the polarity switching signal of the polarity switching device and according to the output polarity ratio setting signal of the output polarity ratio setting device.

The ratio of positive polarity output and reverse polarity output can be changed using an inverter.

Embodiment One embodiment of the present invention will be described below based on the drawings. Components that are the same as those in the conventional example are given the same numbers and descriptions thereof will be omitted.

FIG. 1 is a configuration diagram of a consumable electrode type arc welding machine showing an embodiment of the first invention. In FIG.

21 is a commercial power supply terminal, and an inverter 22 is connected to this commercial power supply terminal 21. The inverter 22 once converts alternating current into direct current using a diode 28 and a capacitor 24, and again converts the alternating current into direct current using a transistor 26 driven by a drive circuit 25 to a frequency different from that of the commercial power source, and outputs the frequency. The output of this inverter 2z is input to the rectifier 28 via the welding insulation transformer 27, and the rectifier 28
The voltage is converted into AC/DC and supplied to the polarity switch 29 as direct Llu power. A short circuit start detector 80 is connected in parallel to the welding output of the polarity switch 29 and detects a short circuit point in the welding load.
The detection signal is output to the drive circuit 82 of the polarity switch 29 and also to the first timer 31. This first timer 31 starts from the time when the detection signal is input.
That is, the time Td from the start of the short circuit until the droplets are reliably transferred to the molten pool is counted and output to the drive circuit 82 of the polarity switch z9. 88 is a timer @2, which outputs an operation stop signal to the short-circuit start detector 8o during the time Ta from the start of activation to the completion of arc start. 84 indicates a welding terminal.

The operation in the above configuration will be explained. From the start of welding, the drive circuit 25 of the inverter 22 drives the transistor 26 to transfer the voltage from the inverter 22 to the welding isolation transformer 27. DC power is supplied to the polarity switch z9 via the rectifier z8. First, the operation at the time of polarity switching will be explained with reference to FIG. In FIG. 6, A and A' indicate welding current and welding voltage waveforms in the apparatus according to the first embodiment of the invention. In the device according to the first embodiment of the invention, the drive circuit 82, at the time when the detection signal from the short circuit start detector 8° is inputted, that is, at the time A when the short circuit starts, drives the first switching elements 8a and 8b, for example. OFF L,, first clock 8
No output is supplied from any of the switching elements 8a, 8b, 4a, 4b during the time Td until the signal from the switching element 1 is received. Therefore, during one hour Td, the energy l stored in the DC reactor 1-A/6 is released, and a short circuit current flows slightly as shown in the waveform A.

Next, when the drive circuit 32 receives the signal from the first timer 81, the second
The switching elements 4a and 4b are ONL, and a short-circuit current having a polarity opposite to that before the short-circuit is supplied. in this way,
Switching elements 3a and 8b of polarity switch 29.

By providing a pause time of 1 hour Td for switching between 4a and 4b, the transfer of the droplet 11 is carried out smoothly, so the generation of spatter during short circuit can be reduced, and it is possible to obtain a welding result with a good welding finish. can.

Next, the operation at the time of starting welding will be explained with reference to FIG. FIG. 2 shows the relationship between the behavior of the consumable electrode and the welding current and welding voltage waveforms at the start of welding. In FIG. 2, the supply to the consumable electrode 8 starts from the welding start time C, and at the same time, the welding output is supplied from the polarity switch 29, but the consumable electrode 8 is not in contact with the workpiece 9. Therefore, no welding current flows and no-load voltage is applied. next,
When the consumable electrode 8 is fed and comes into contact with the object to be welded 9, the arc starts and the starting current begins to flow.

At this time, as shown in FIG.

If there is a delay time of time Td, the power will not be energized and it will be consumed W.
Since i8 is pressed against the workpiece 9, a large amount of starting current is required to start the arc, resulting in insufficient starting current and failure to start the arc. Therefore, the short-circuit start detector 80 is stopped by the timer 88 in the box 2 for a certain period of time Ta from the welding start point C to the arc start completion point E, and when the welding starts, the consumable electrode 8 is connected to the object to be welded. 9, the starting current is increased without immediately switching the polarity, and a good arc start is obtained. Regarding a short circuit after the arc start has been smoothly completed, the polarity is switched and the welding current is started up with a delay of time Td, similar to the waveforms in Fig. 6A and 6A.

Next, an embodiment of the second invention will be described based on FIG. 3. The embodiment of the invention @2 has a welding exit polarity ratio setting device 86 added to the configuration of the embodiment of the first invention shown in FIG. The welding output polarity ratio setting device 86 sets the output ratio of the positive polarity output and the reverse polarity output of the welding output, - output ratio setting signal is output to the drive circuit 87 of the polarity switch 86. Similar to the first embodiment, this drive circuit 87 raises the starting current at the start of startup to perform a smooth arc start, and after the completion of the arc start, the
2 switching element 8a @ 8b * 4a *
4b is provided with a pause time of time Td to ensure smooth droplet transfer, and the first switch which supplies a positive polarity output based on the welding output ratio setting signal from the welding output polarity ratio setting device 85 Switching elements 8a, 8b
to.

a second switching element 4a that supplies negative polarity output;
The ratio of the bus width output from 4b is changed and output. By changing the output ratio in this way, the advantage of welding performed with reverse polarity output, that is, the ability to penetrate deeply into the workpiece 9, and the advantage of welding performed with positive polarity output, that is, the ability of the consumable electrode 8 to be Welding is performed by selecting the optimal welding conditions according to the thickness of the workpiece 9 and the gap of the welding part by combining the advantages of increasing the amount of melting and suppressing the heat input to the workpiece 9. be able to.

Next, an embodiment of the eighth invention will be described based on FIG. 4. The third embodiment of the invention has the configuration of the first embodiment of the invention shown in FIG. The synchronous circuit 40 is connected to the drive circuit 82 of the polarity switch 29 and the welding output polarity ratio setter 89, and is connected to the welding output polarity ratio setter 89 in synchronization with the polarity switching signal of the drive circuit 82. The output ratio signal of 89 is outputted to the drive circuit 4z of the inverter 41. Polarity switch 29! The second invention performs the same operation as described in detail in the first invention, obtains a good arc start at startup, and further reduces spatter generation during short circuit. Drive circuit 4 of inverter device 41
2 drives the transistor 26 in accordance with the output signal of the synchronization circuit 40 and in synchronization with the polarity switching signal so that the pulse width varies depending on the output ratio. By changing the output ratio in this way, it is possible to select and weld the optimal welding conditions depending on the state of the workpiece 9, as explained in the embodiment of the second invention. Furthermore, the drive circuit 82 of the polarity switch 29 performs control of polarity switching having a time limit Td, and the drive circuit 42 of the inverter 41 performs control of the output ratio. In addition, it is possible to avoid the above two controls from interfering with each other in the drive circuit 82 of the polarity switch 29.

Effects of the Invention According to the first invention as described in 1, at the start of welding,
The second timer deactivates the short circuit detector and wears it out! By starting up the starting current immediately from the moment the pole shorts to the workpiece.

In addition to improving the arc start, during welding, instead of immediately switching the output polarity and starting the short-circuit current after the short-circuit starts, the short-circuit current is started after detecting the elapse of a certain period of time by the operation of the first timer. By standing up, it is possible to smoothly transfer the droplets during a short circuit, suppress the generation of spatter, and obtain a beautiful welding result.

According to the second invention, in addition to the effects of the first invention, the output polarity ratio is changed by the polarity switch, so that the advantages of the positive polarity output and the advantages of the reverse polarity output are combined, and the plate of the workpiece can be welded. Welding can be performed by selecting optimal welding conditions depending on the thickness, the gap of the n-junction, etc.

According to the eighth invention, in addition to the effect of the first invention, since the output polarity ratio is changed by the inverter, J:
Similar to the effect of the second invention, it is possible to select and weld the optimal welding conditions according to the object to be welded, and furthermore, the polarity switching with a fixed time limit can be controlled using a polarity switching device, and the output polarity ratio can be controlled by using a polarity switching device. % because control is shared by an inverter
This also avoids complicating the polarity switch circuit.

This makes it possible to avoid interference between the above two controls inside the polarity switch.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a consumable electrode type arc welding machine showing an embodiment of the first invention, and Fig. 2 shows a consumable electrode of the same consumable electrode type 7-way welding machine at the time of starting welding and immediately before and after a short circuit during welding. Fig. 8 is a diagram showing the configuration of a consumable electrode type arc welding machine showing an embodiment of the second invention; Fig. 5 is a block diagram of a conventional consumable electrode arc welding machine, and Fig. 6 is a consumable electrode arc welding machine according to an embodiment of the invention of Fill. FIG. 2 is an explanatory diagram showing the behavior of a consumable electrode during welding by a welding machine, the relationship between droplet transfer, welding current, and welding voltage □ waveform. 22, 40...inverter, 29, 86-i
gender switch, 80... short circuit start detector, 81... first timer, aa... second timer, 1115.8
9... Welding output polarity ratio setting device, 42... Synchronous circuit.

Claims (1)

[Claims] 1. A short-circuit start detector that detects when the consumable electrode starts short-circuiting to the workpiece; and a detection signal from the short-circuit start detector that causes droplets to form a molten pool after the short-circuit starts. a first timer that counts the time until the welding start is started, and a second timer that instructs the short-circuit start detector to stop operation from the start of the welding start until the arc start is completed. The supply of welding output to the consumable electrode and the workpiece is stopped or reduced based on the detection signal of the second timer and the short circuit start detector, and the welding output is stopped or reduced based on the output signal after the time limit of the first timer. 1. A consumable electrode type arc welding machine characterized by being equipped with a polarity switch that switches the polarity of the welding electrode and starts or increases the supply of welding output. 2. A short-circuit start detector that detects when the consumable electrode starts short-circuiting to the workpiece, and a detection signal from the short-circuit start detector that starts the short-circuit until the droplets are reliably transferred to the molten pool. a first timer that counts the time at the start of welding, and a second timer that instructs the short-circuit start detector to stop operating from the start of welding until the arc start is completed; The supply of welding output to the consumable electrode and the object to be welded is stopped or reduced according to the detection signal of the short circuit start detector, and the output signal of the welding output after a time limit is used to reverse the positive polarity of the welding output. and an output polarity ratio setting device that outputs a ratio setting signal between a positive polarity output and a reverse polarity output of the welding output to the polarity switching device. A consumable electrode type arc welding machine, characterized in that the welding output polarity ratio is adjusted by the polarity switch. 3. An inverter connected to a commercial power source to perform frequency conversion, an insulating transformer for welding to which the output of the inverter is connected to the primary side, and an AC/DC converter connected to the secondary side of the insulating transformer for welding. a short-circuit start detector that detects when the consumable electrode starts short-circuiting to the workpiece; and a detection signal from the short-circuit start detector that ensures that the droplets reach the molten pool after the short-circuit starts. a first timer that counts the time until the transition; and a second timer that counts a time limit upon the start of welding and instructs the short-circuit start detector to stop operating from the start of welding until the arc start is completed. The supply of the welding output to the consumable electrode and the workpiece is stopped or reduced according to the detection signal of the short-circuit start detector and the short circuit start detector, and the positive polarity of the welding output is determined according to the output signal after the time limit of the first timer. a polarity switch that switches between an output and a reverse polarity output and starts or increases the supply of welding output; an output polarity ratio setting device that sets a ratio between the positive polarity output and the reverse polarity output of the welding output; and the polarity switch and a synchronization circuit connected to the output polarity ratio setting device and outputting the output ratio signal of the output polarity ratio setting device to the inverter in synchronization with the polarity switching signal of the polarity switching device,
A consumable electrode type arc welding machine, characterized in that the welding output polarity ratio is adjusted by the inverter.