JPH07115181B2 - Consumable electrode arc welder - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a consumable electrode type in which the polarity of the welding output supplied from the consumable electrode to the object to be welded is switched to a positive polarity and a reverse polarity during welding. The present invention relates to an arc welder.

Conventional technology Conventionally, this type of device employs a method of immediately switching the polarity when a short circuit is detected by a short-circuit detector that detects that the consumable electrode has short-circuited with the workpiece. The polarity switching in the middle was also performed in the same way. Fifth
FIG. 1 shows an example of the structure of a conventional consumable electrode type arc welder of this type. In FIG. 5, reference numeral 1 is a DC voltage source, which supplies power to the polarity switch 2. Recently, a DC voltage source 1 using an inverter has been adopted.
The polarity switching device 2 includes first switching elements 3a and 3b for supplying a positive polarity output to the welding load, second switching elements 4a and 4b for supplying a reverse polarity output to the welding load, and these first switching elements 3a. , 3b and second switching elements 4a, 4b
And a drive circuit 5 for switching between the two, and a DC reactor 6, a power feed chip 7, a consumable electrode 8 and a workpiece 9 as the welding load are connected in series to the output of the polarity switcher 2.
And are connected. Reference numeral 10 denotes a short-circuit detector, which detects that the consumable electrode 8 and the workpiece 9 are short-circuited and outputs this detection signal to the drive circuit 5. With these configurations, when welding is started, the drive circuit 5 drives the first switching elements 3a, 3b or the second switching elements 4a, 4b to supply the welding output to the consumable electrode 8 and the workpiece 9. As soon as the consumable electrode 8 short-circuits with the object 9 to be welded and the short-circuit detector 10 detects a short circuit, the drive circuit 5 switches the first switching elements 3a, 3b and the second switching elements 4a, 4b to switch the consumable electrode. 8 and the polarity of the welding output supplied to the workpiece 9 are switched.

Problems to be Solved by the Invention However, in the conventional configuration, since the polarity is switched as soon as a short circuit is detected, the consumable electrode 8 has a drawback that the droplets melted by the arc cannot be smoothly transferred to the molten pool. . This will be described with reference to FIG. FIG. 6 shows the behavior of the consumable electrode 8 immediately before and after the short circuit between the consumable electrode 8 and the workpiece 9.
It shows the relationship between the transfer of droplets and the welding current and welding voltage waveforms. In FIG. 6, 11 is a droplet, 12 is a molten pool, and a and a'represent the welding current and welding voltage waveforms by the conventional device, respectively. As shown in FIG. 6, in the conventional apparatus, the short-circuit current immediately rises greatly at time A immediately after the droplet 11 of the consumable electrode 8 short-circuits with the molten pool 12, so that the droplet 11 is large due to the short-circuit current. Since it is pressed against the molten pool 12 by the pinch force, the droplet 11 and the deposited metal of the molten pool 12 are violently stimulated, a large amount of spatter scatters, adheres to the surface of the object 9 to be welded, and the weld finish is poor.

The present invention solves the above problems, and an object of the present invention is to provide a consumable electrode type arc welder that reduces the occurrence of such 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 uses a short circuit start detector that detects a time point when a consumable electrode starts a short circuit to a workpiece, and a detection signal of the short circuit start detector. A first timer that counts the time from the start of a short circuit to the time when the droplets reliably transfer to the molten pool, and the time limit is counted by starting the welding start, and the short circuit start detector for a fixed time from the start of the welding start. And a second timer for instructing the stop of the operation, and by stopping or reducing the supply of the welding output to the consumable electrode and the object to be welded by the detection signal of the short-circuit start detector, the time limit of the first timer. A polarity switching device for switching the polarity of the welding output and starting or increasing the supply of the welding output by a subsequent output signal is provided.

A second aspect of the invention is the addition of an output polarity ratio setting device for outputting a positive polarity output of welding output and a reverse polarity output ratio setting signal to the polarity switching device, in addition to the configuration of the first invention.

A third aspect of the present invention is, as the DC power source having the configuration of the first aspect of the invention, an inverter unit connected to a commercial power source for frequency conversion, and an insulation transformer for welding in which an output of the inverter unit is connected to a primary side. A configuration comprising a rectifier connected to the secondary side of the welding insulation transformer and performing AC / DC conversion, and further, an output polarity ratio setting device for setting the ratio of the positive polarity output and the reverse polarity output of the welding output, and the polarity. A switching circuit and an output polarity ratio setting device, and a synchronizing circuit for outputting the output ratio signal of the output polarity ratio setting device to the inverter device in synchronization with the polarity switching signal of the polarity switching device are added.

Action According to the configuration of the first invention, at the start of activation, the second timer stops the operation of the short circuit start detector for a certain period of time from the start of activation, the polarity switching is eliminated, and the polarity switching device immediately activates. Start up the current to prevent arc start failure, and activate the short circuit development detector after the certain time has passed,
Between the input of the short-circuit detection signal and the output signal of the first timer by the polarity switcher, that is, the consumable electrode and the work piece are short-circuited, and the droplets reliably move to the molten pool. Until then, the supply of welding output is stopped or reduced to reduce the occurrence of spatter, the polarity of the welding output is switched by the input of the output signal of the first timer, and the supply of welding output is resumed or increased.

Further, in the second invention, in addition to the operation of the first invention, the ratio of the positive polarity output and the reverse polarity output is changed by the polarity switcher according to the output polarity ratio setting signal of the output polarity ratio setting device.

In the third invention, in addition to the operation of the first invention, in accordance with the output polarity ratio setting signal of the output polarity ratio setting device in synchronization with the polarity switching signal of the polarity switching device, a positive output is produced by the inverter device. The ratio of reverse polarity output can be changed.

Embodiment An embodiment of the present invention will be described below with reference to the drawings. The same parts as those of the conventional example are designated by the same reference numerals and the description thereof will be omitted.

FIG. 1 is a configuration diagram of a consumable electrode type arc welder showing an embodiment of the first invention. In FIG. 1, reference numeral 21 is a commercial power supply terminal, and an inverter 22 is connected to the commercial power supply terminal 21. The inverter 22 once converts the alternating current into the direct current by the diode 23 and the capacitor 24, converts it into a frequency different from that of the commercial power source by the transistor 26 driven by the drive circuit 25 again, and outputs it. This inverter 22
Is input to the rectifier 28 via the welding insulation transformer 27, is AC-DC converted by the rectifier 28, and supplies the DC power to the polarity switch 29. Short circuit start detector that is connected in parallel to the welding output of the polarity switcher 29 and detects the point of short circuit of the welding load.
The detection signal of 30 is output to the drive circuit 32 of the polarity switch 29 and also to the first timer 31. The first timer 31 counts the time Td from the time when the detection signal is input, that is, from the start of the short circuit to the time when the droplet surely moves to the molten pool, and drives the polarity switch 29. Output to the circuit 32. 33 is a second timer, which outputs an operation stop signal to the short-circuit start detector 30 during the time Ta from the start of start to the completion of arc start. 34 indicates a welding output terminal.

The operation of the above configuration will be described. From the start of welding, the drive circuit 25 of the inverter 22 drives the transistor 26 and supplies DC power from the inverter 22 to the polarity switch 29 via the welding insulating transformer 27 and the rectifier 28. First, the operation when switching the polarity will be described with reference to FIG. In FIG. 6, a and a'show welding current and welding voltage waveforms in the apparatus according to the embodiment of the first invention. In the device of the first embodiment of the invention, the drive circuit 32 turns on the first switching elements 3a, 3b, for example, at the time when the detection signal from the short circuit start detector 30 is input, that is, at the time A when the short circuit starts. O
The output from all the switching elements 3a, 3b, 4a, 4b is not supplied during the time Td until FF is performed and the signal from the first timer 31 is received. Therefore, during the time Td, the energy accumulated in the DC reactor 6 is released, and a short-circuit current slightly flows like the waveform of B. Next drive circuit
When the signal from the first timer 31 is input, that is, at time B when the time Td has elapsed, 32 is the second switching element.
Turn on 4a and 4b to supply the short circuit current with the polarity opposite to the polarity before the short circuit. Thus, by providing the pause time of time Td for switching the switching elements 3a, 3b, 4a, 4b of the polarity switch 29, the droplet 11 can be smoothly transferred, so that the sputtering at the time of short circuit is performed. It is possible to reduce the occurrence of welding and obtain a welding result with a good welding finish.

Next, the operation at the time of starting welding will be described with reference to FIG. FIG. 2 shows the relationship between the behavior of the consumable electrode at the time of starting welding and the welding current and welding voltage waveforms. In FIG. 2, the feeding to the consumable electrode 8 is started from the welding start time C, and the welding output is supplied from the polarity switcher 29 at the same time, but the consumable electrode 8 is not in contact with the workpiece 9. Therefore, welding current does not flow and no-load voltage is applied. Next, when the consumable electrode 8 is fed and comes into contact with the object 9 to be welded, an arc start is started and a starting current starts to flow. At this time, as shown in FIG. 6, if there is a delay time of Td, the consumable electrode 8 is pressed against the object 9 to be welded without being energized, so a large starting current is required for arc start. Then, the arc start fails due to insufficient starting current. Therefore, the operation of the short-circuit start detector 30 is stopped by the second timer 33 during the fixed time Ta from the welding start start time C to the arc start completion time E, and the consumable electrode 8 is not covered when the welding start is started. At the time point D when the welding object 9 and the welding object 9 are short-circuited, the starting current is raised immediately without switching the polarity, and a good arc start is obtained. Regarding the short circuit after the arc start is smoothly completed, the polarity is switched and the welding current is started with the delay time of Td, as in the waveforms of FIGS. 6A and 6B.

Next, an embodiment of the second invention will be described with reference to FIG. The second embodiment of the present invention is obtained by adding a welding output polarity ratio setting device 35 to the configuration of the first embodiment of the present invention shown in FIG. The welding output polarity ratio setting device 35 sets the output ratio of the positive polarity output of welding output and the reverse polarity output, and outputs this output ratio setting signal to the drive circuit 37 of the polarity switching device 36. As in the case of the first embodiment, the drive circuit 37 immediately raises the starting current at the start of starting to smoothly perform the arc start, and after the completion of the arc start, the first and second switching elements 3a, 3b, 4a. , 4b is provided with a rest time of Td for smooth transition of droplets, and positive output is supplied based on a welding output ratio setting signal from the welding output polarity ratio setting device 35. Switching element
3a, 3b and the second switching elements 4a, 4b for supplying the negative output are changed in the ratio of the pulse widths and output. By changing the output ratio in this way, the merit of welding performed with reverse polarity output, that is, the point of deep penetration into the workpiece 9 and the merit of welding performed with positive output, that is, the melting amount of the consumable electrode 8 It is possible to select the optimum welding conditions according to the plate thickness of the object to be welded 9 and the gear gap of the welded part, and to perform welding by combining the fact that the heat input to the object to be welded 9 can be suppressed low.

Next, an embodiment of the third invention will be described with reference to FIG. The third embodiment of the present invention is the same as that of the first embodiment of the invention shown in FIG. 1, and is synchronized with a welding output polarity ratio setter 39 for setting the output ratio of the positive polarity output of welding output and the reverse polarity output. The circuit 40 is added, and the synchronizing circuit 40 has a polarity switching device 29.
Connected to the drive circuit 32 and welding output polarity ratio setter 39 of
In synchronization with the polarity switching signal of the drive circuit 32, the output ratio signal of the welding output polarity ratio setter 39 is transferred to the drive circuit 42 of the inverter 41.
Output to. The polarity switch 29 performs the same operation as described in the first embodiment of the invention to obtain a good arc start at the time of starting and further reduce the occurrence of spatter at the time of short circuit. The drive circuit 42 of the inverter 41 synchronizes with the polarity switching signal according to the output signal of the synchronizing circuit 40, and drives the transistor 26 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 optimum welding conditions depending on the state of the workpiece 9 as described in the second embodiment of the invention. further,
The drive circuit 32 of the polarity switch 29 shares the control of the polarity switching having the time period Td and the drive circuit 42 of the inverter 41 with the control of the output ratio.
It is possible to prevent the 32 from becoming complicated and prevent the above two controls from interfering with each other in the drive circuit 32 of the polarity switcher 29.

EFFECTS OF THE INVENTION As described above, according to the first invention, at the start of welding,
A second timer stops the operation of the short-circuit detector, and the starting current rises immediately from the moment when the consumable electrode short-circuits to the work piece. Does not switch the output polarity immediately after the start of the short circuit to raise the short-circuit current, but rather raises the short-circuit current after detecting the elapse of a fixed time period by the operation of the first timer, It is possible to smoothly transfer the droplets, suppress the generation of spatter, and obtain a welding result with a beautiful finish.

According to the second aspect of the invention, in addition to the effect of the first aspect of the invention, since the output polarity ratio is changed by the polarity switcher, the merits due to the positive polarity output and the merits due to the opposite polarity output are combined and the plate of the workpiece is welded. The optimum welding conditions can be selected and welded according to the thickness and gear gap of the welded portion.

According to the third aspect of the invention, in addition to the effect of the first aspect of the invention, the output polarity ratio is changed by the inverter. Therefore, similar to the effect of the second aspect of the invention, the optimum welding condition is set according to the workpiece. The polarity switcher controls the polarity switching with a fixed time, and the output polarity ratio is controlled by the inverter. It is possible to avoid complication and to prevent the above two controls from interfering with each other inside the polarity switcher.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a consumable electrode type arc welder showing an embodiment of the first invention, and FIG. 2 is a behavior of the consumable electrode immediately before and immediately after a short circuit during welding of the consumable electrode type arc welder. FIG. 3 is an explanatory view showing the relationship between droplet transfer and welding current and welding voltage waveforms, FIG. 3 is a configuration diagram of a consumable electrode type arc welder showing an embodiment of the second invention, and FIG. 4 is a third invention. Of the consumable electrode type arc welding machine showing the embodiment of FIG. 5, FIG. 5 is a block diagram of a conventional consumable electrode type arc welding machine, and FIG. 6 is a consumable electrode type arc welding machine of the conventional and the first invention. FIG. 5 is an explanatory diagram showing the relationship between the behavior of the consumable electrode during welding of the machine, the transfer of droplets and the welding current and welding voltage waveforms. 22,40 …… Inverter, 29,36 …… Polarity switch, 30 ……
Short-circuit start detector, 31 …… first timer, 33 …… second timer, 35,39 …… welding output polarity ratio setter, 42 …… synchronous circuit.

Claims (3)

[Claims] 1. A short circuit start detector for detecting a time point when a consumable electrode starts a short circuit to an object to be welded, and a droplet is surely deposited in a molten pool after a short circuit is started by a detection signal of the short circuit start detector. A first timer that counts the time until the transition, and a second timer that counts the time period by starting the welding start and commands the stop of the operation to the short-circuit start detector for a fixed time from the start of the welding start, The supply of the 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 polarity of the welding output is switched according to the output signal after the time limit of the first timer and welding is performed. A consumable electrode arc welding machine, comprising a polarity switching device for starting or increasing supply of output. 2. A short circuit start detector for detecting the time when the consumable electrode starts a short circuit to the object to be welded, and a droplet is surely deposited in the molten pool after the short circuit is started by the detection signal of the short circuit start detector. A first timer that counts the time until the transition, and a second timer that counts the time period by starting the welding start and commands the stop of the operation to the short-circuit start detector for a fixed time from the start of the welding start, The supply of the welding output to the consumable electrode and the object to be welded is stopped or reduced by the detection signal of the short-circuit start detector, and the positive polarity output of the welding output is reversed by the output signal of the first timer after the time limit. A polarity switcher for switching the polarity output and starting or increasing the supply of the welding output, and an output polarity ratio setter for outputting a positive polarity output of the welding output and a reverse polarity output ratio setting signal to the polarity switcher. And consumable electrode arc welder to adjust the welding output polarity ratio and performing by said polarity switching device. 3. An inverter connected to a commercial power source for frequency conversion, an insulation transformer for welding whose output is connected to the primary side, and a secondary side of the insulation transformer for welding. A rectifier that performs AC / DC conversion, a short circuit start detector that detects the time when the consumable electrode starts a short circuit to the work piece, and a droplet is melted after the short circuit is started by the detection signal of the short circuit start detector. To a first timer for counting the time until the start of the welding is started, and a second timer for counting the time limit by starting the welding start and for instructing the short-circuit start detector to stop the operation for a certain time from the start of the welding start. A vessel,
Stops or reduces the supply of welding output to the consumable electrode and the workpiece by the detection signal of the short circuit start detector,
A polarity switching device that switches between the positive polarity output and the reverse polarity output of the welding output and starts or increases the supply of the welding output by the output signal of the first timer after the time limit, and the positive polarity output of the welding output. An output polarity ratio setting device for setting a ratio of reverse polarity output, and an output ratio of the output polarity ratio setting device connected to the polarity switching device and the output polarity ratio setting device in synchronization with a polarity switching signal of the polarity switching device. A consumable electrode type arc welding machine, comprising: a synchronizing circuit for outputting a signal to the inverter unit, wherein the welding output polarity ratio is adjusted by the inverter unit.