JPH11138270A - Arc welding equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an arc welding equipment capable of preventing a molten part of a work from bursting and splashing at the time of welding. SOLUTION: A plasma power source 31 is controlled by a controller 59 from the starting of welding to the finishing of hole opening, and a prescribed duty ratio of pulse current is applied among a torch, filler and the work. During this period, a larger flow quantity of plasma gas than that after the finishing of hole opening is fed to a place to be welded by controlling a gas controller 32, the plasma power source 31 is controlled so that a constant current is outputted after the finishing of hole opening, and the gas controller 32 is controlled so that a rather small flow quantity of plasma gas is fed. A filler feeding device 28 is started so that filler immediately begins to be fed to a part to be welded. The feeding speed of the filler feeding device 28 is controlled so that a rather small quantity of filler is fed in the early stages of starting feeding and the quantity is increased as time passes. After welding, the filler feeding device 28 is controlled so that filler stops to be fed to the part to be welded, and the plasma power source 31 is controlled until finishing is completed so that a large value of constant current is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an arc welding apparatus. Hereinafter, a plasma arc welding apparatus will be described as an example.

[0002]

2. Description of the Related Art Plasma arc welding, for example, plasma arc spot welding, has the advantage that it can be applied to a work having a complicated shape or a large work because it can be welded from one side of a superposed metal work. Have been. 2. Description of the Related Art Conventionally, plasma arc spot welding has been performed using a plasma arc welding apparatus and using two steel sheets subjected to surface treatment by galvanization as a work.

[0003]

By the way, when a high-temperature plasma arc 3 as shown in FIG. 1A is generated between the plasma torch 1 and the steel plate (upper plate) 7 on the upper side of the work 5 at the start of welding, As shown in FIG. 1B, a hole 7a is formed in the upper plate 7 by the heat of the plasma arc 3 in parallel with the detection of the gap between the upper plate 7 and the lower plate 9. Then, the lower plate 9 is also heated through the holes 7a, and as shown in FIG. 1C, melting and joining of the upper plate 7 and the lower plate 9 are started, and the central portion is welded.

However, in the process of increasing the nugget diameter to increase the welding strength, if the molten portion of the upper plate 7 becomes too large, as shown in FIG. It may fall on the plate 9. In this case, when the molten portion falls so as to cover the lower plate 9, the molten portion
As shown in (e), the phenomenon of explosion, which blows away the covered molten portion, is likely to occur. Moreover, the exploded molten portion adheres to the plasma torch 1 and, in the worst case, penetrates into the nozzle 2 and closes the opening of the nozzle 2, so that the plasma arc 3 causes the plasma torch 1 and the work 5 There is a possibility that a problem that the problem will not occur in between will occur.

The cause of such explosion is that the melting point of the base steel material is relatively high at about 1500 ° C., whereas the boiling point of zinc coating the steel material is relatively low at 900 ° C. This is considered to be due to the fact that there is a gap between the upper plate and the lower plate, and that a wide range of the molten portion on the upper plate falls on the galvanized layer of the lower plate at once.

That is, when the molten portion of the upper plate 7 covers the galvanized layer covering the lower plate 9, the galvanized layer is rapidly vaporized and becomes zinc gas. It is presumed that the molten portion is blown off by the pressure of the confined zinc gas because the gas is confined in the gap 8 between the base material and the lower plate 9. Therefore, when a steel sheet surface-treated with a material having a relatively low boiling point such as zinc is used as an upper plate and a lower plate, and a gap is provided between the upper plate and the lower plate for welding, some countermeasures are taken. Unless applied, it can be said that it is difficult to avoid explosion.

Accordingly, an object of the present invention is to provide an arc welding apparatus capable of preventing a molten portion of a work from exploding during welding.

[0008]

An arc welding apparatus according to a first aspect of the present invention includes means for setting a workpiece and a filler supplied to a welding portion of the workpiece at the same potential.

An example of the same potential setting means is an electric wiring for connecting the filler and the work. Due to this electric wiring, most of the arc current flows to the filler side when the filler is supplied, so that the amount of heat input to the work is reduced. Therefore, it is possible to prevent a wide area including the welding portion of the upper plate of the work from dropping onto the lower plate of the work at one time. The work includes at least a base material coated with a substance having a boiling point lower than the melting point of the base material, such as a steel material whose surface is galvanized.

In a preferred embodiment according to the first aspect of the present invention, the filler is started to be supplied when a hole is formed in the upper plate of the work. The supply amount of the filler is controlled to be the smallest at the start of the supply and to increase over time. The reason is that the filler is not completely melted at the start of the supply because the filler is completely cooled. The supply amount of the filler is controlled by controlling the supply speed of the filler.

The arc welding apparatus according to the second aspect of the present invention includes means for reducing the amount of heat input to the work after the initial welding than in the initial welding.

According to this configuration, the amount of heat input to the work after the initial stage of welding is reduced, so that a wide area including the welded portion of the upper plate of the work is prevented from dropping onto the lower plate of the work at one time. it can.

In a preferred embodiment according to the second aspect of the present invention, a shielding gas supplied toward a welding portion of the work is applied as the heat input amount reducing means. As the shielding gas, a non-oxidizing gas having a relatively high thermal conductivity, for example, a hydrogen gas or a mixed gas of a helium gas and an argon gas is employed.

As a means for reducing the amount of heat input, means for cooling a welded portion of a work other than the above-mentioned shield gas is applied. As the cooling means, a member which is placed near the welding portion of the work and has higher thermal conductivity than the work is used. Further, as the heat input amount reducing means, a filler supplied to a welding portion of a work other than the above-mentioned shielding gas and cooling means can be mentioned. The supply of the filler is started when a hole is formed in the upper plate of the work.

[0015] The supply amount of the filler is minimized at the start of the supply, and is controlled so as to increase over time.
The reason is that, as described above, since the filler is completely cooled at the start of the supply, the filler is difficult to melt. It should be noted that the supply of the filler is controlled by controlling the supply speed of the filler, which is the same as described above.

Further, it is possible to use a filler as the heat input amount reducing means, and also include a means for vibrating the welding portion of the work. The vibrating means is activated when the supply of the filler to the welding portion of the workpiece is completed. This vibrating means is used for flattening the filler supplied to the welding portion of the workpiece, which is in a raised state at the welding portion and in the vicinity thereof, by applying vibration during finishing.

As an example of the vibration means, a means for supplying a pulse-like plasma gas to a welding portion of a work is used, for example. In this case, the peak value of the supply amount of the pulsed plasma gas is set to be larger than that at the time of supplying the filler. As another example of the vibration means, means for applying a pulsed arc current between the workpiece and the electrode is used. in this case,
The peak value of the supply amount of the pulsed arc current is set to be larger than that at the time of supplying the filler.

Here, the above-mentioned initial stage of welding is a period from the start of welding until a hole is formed in the upper plate of the work. The detection of a hole formed in the upper plate of the work is performed by determining whether or not a predetermined time has elapsed from the start of welding. It can also be performed by monitoring the arc voltage applied between the electrode for arc welding and the workpiece. The hole can be detected using an optical sensor, a heat sensor, a CCD camera, or the like as a detecting unit.

An arc welding apparatus according to a third aspect of the present invention includes a means for supplying a filler to a welding portion of a work, and a means for setting the filler supplied to the welding portion of the work to the same potential. The filler supply means is controlled to start supplying the filler when a hole is formed in the upper plate of the work.

According to a fourth aspect of the present invention, there is provided an arc welding apparatus comprising: means for supplying a filler to a welding portion of a workpiece; means for setting the filler supplied to the welding location of the workpiece to the same potential; Means for vibrating the welded portion of the workpiece, the filler supply means is controlled so that the supply of the filler is started when a hole is formed in the upper plate of the work, and the vibration means controls the supply of the filler to the welded part of the work. It is controlled to start when finished.

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 2 shows an overall configuration of an embodiment of the present invention implemented as a plasma arc spot welding apparatus. Plasma arc welding includes plasma arc spot welding and plasma arc wire welding, and as an apparatus for performing each of these, there are a plasma arc spot welding apparatus and a plasma arc wire welding apparatus.In one embodiment of the present invention, The plasma arc spot welding device will be described as an example.

As shown in FIG. 2, a plasma arc spot welding apparatus (welding apparatus) according to one embodiment of the present invention includes:
A plasma torch 21, a welding power source 23, a robot controller 24, a high-frequency unit 25, a filler nozzle 27, a filler feeding device 28, and a robot 30 are provided.

The plasma torch 21 is attached to the tip of an arm of the robot 30. Since the movement and posture of the robot 30 are controlled by the robot controller 24, the work 22 can be welded from all directions by the torch 21. The welding power source 23 is a power required to perform plasma arc welding,
The plasma gas and the shield gas are supplied to the plasma torch 21, and the welding conditions including the plasma gas flow rate, the shield gas flow rate, the welding current value, the welding time, and the like are also controlled.

The high-frequency unit 25 generates high-frequency power for causing dielectric breakdown when a pilot arc is generated. The filler nozzle 27 receives the wire-like filler (filler) sent from the filler feeder 28,
This is supplied to the front of the torch 21, and is attached near the tip of the plasma torch 21 so as to supply a filler into a plasma arc generated between the work 22 and the torch 21. The filler feeding device 28 is connected to the welding power source 23.
The filler is sent out or stopped in response to a command from the user.

FIG. 3 is a block diagram showing the configuration of the above-mentioned welding power source 23 and the elements related to the welding power source 23 together.

As shown in FIG. 3, the welding power source 23 includes a plasma power source 31, a gas controller 32, and a gap determining device 33.
And a welding controller 34.

The plasma power supply 31 is connected to the welding controller 3
4, constant current control is performed during welding so that the supply current (current of the plasma arc 40) matches the target value. That is, the plasma power supply 31 supplies the controlled electric power (voltage and current) necessary for generating and maintaining the plasma arc 40 to the torch 21 under the control of the welding controller 34.
The gas controller 32, under the control of the welding controller 34,
A plasma gas and a shield gas having a controlled pressure are supplied to the torch 21. The gap determination device 33 monitors the voltage generated by the plasma power supply 31 during welding (that is, the voltage between the torch 21 and the work 22, that is, the voltage drop at the plasma arc 40), and the upper plate 41 and the lower plate of the work 22. The size of the gap 43 between the base plates 42 (the upper plate 41 and the lower plate 42 are both steel plates) is determined.

The welding controller 34 includes, together with the components (plasma power supply 31, gas controller 32, and gap determination device 33) constituting the welding power supply 23 described above, the gas flow rate switch 26 attached to the gas inlet of the torch 21, The filler feeder 28 is also under its control.

Here, the gas flow rate switch 26 is configured to switch the flow rates of the plasma gas and the shield gas between large and small in response to a command from the welding power source 23. That is, a switchable open / close valve is provided in the gas flow rate switch 26. By switching the open / close valve, the flow rates of the plasma gas and the shield gas are respectively large and small.
The stage is switched. The reason why the gas flow switch 26 is attached to the gas inlet of the torch 21 is that there is no substantial time delay between the switching operation of the gas flow switch 26 and the actual change in the flow rate of the gas ejected from the torch 21. That's why.

The control operations of the welding controller 34 include driving and stopping the gas controller 32, giving an instruction to switch the flow rate to the gas flow rate switching device 26, and driving and stopping the filler feeding device 28. And stopping and driving the plasma power supply 31. Also,
Giving a current target value to the plasma power supply 31, monitoring the supply voltage of the plasma power supply 31, and acquiring welding conditions such as filler supply amount and welding time according to the size of the gap 43 from the gap determination device 33; This includes monitoring the supply voltage of the plasma power supply 31 and determining the timing of changing the welding process.

Further, in this embodiment, in order to make the potential between the filler 29 and the work 22 the same, an electric wiring 44 connecting the filler nozzle 27 and the work 22 is provided. Regarding the operation and effect of the electric wiring 44,
Details will be described later.

FIG. 4 is a block diagram showing the configuration of the welding controller 34 according to one embodiment of the present invention.

As shown in FIG. 4, the welding controller 34 includes a finishing processing determining section 51, a timer 53, a storage section 55, a drilling completion determining section 57, a control section 59, and a welding completion determining section 61. And an interface unit 63.

The storage unit 55 stores the driving time data of the timer 53, the time required for perforating the upper plate 41 (perforation time), and the time required for welding the upper plate 41 and the lower plate 42 by filler supply ( It stores data such as welding time) data and time (finish processing time) required for smoothing the swelling portion of the filler 29 at the welding location. These time data are based on so-called condition setting. The storage unit 55 also stores pulse current (welding current) value data of a predetermined duty ratio applied between the torch 21 and the work 22 at the time of drilling the upper plate 41 and while the filler 29 is being fed. It also stores constant current (constant current) value data applied as a welding current. The storage unit 55 further stores constant current value data that is applied at the time of finishing processing and has a larger value than the above constant current value data, plasma gas flow rate data supplied to a welding portion of the work 22, and feed of the filler 29. It also stores quantity data and the like. Here, the plasma gas flow rate data is set relatively large at the time of drilling, and set relatively small during the period from the end of drilling to the end of finishing. In addition, the feed amount data of the filler 29 is set to be small at the beginning of the feed and to gradually increase as time passes. Since the feed amount and the feed speed are in a proportional relationship, they are stored in the storage unit 55 in association with each other. It is also possible to set the feed amount data so as to be adapted to a two-stage switching control of the feed speed such that the feed speed is set to a low speed at the start of feeding and then set to a high speed after a lapse of a certain time.

The timer 53 is started when the current detector 65 detects the first rise of the continuous waveform of the pulse current (at the start of welding), and operates for a preset time (ie, at least from the start of welding to the start of welding). Time until finishing is completed), and continue the timing operation. The timer 53 outputs a pulse signal at predetermined time intervals during the time counting operation. The pulse signal output from the timer 53 is supplied to the finishing process determination unit 51, the drilling completion determination unit 57, and the welding completion determination unit 61 through the interface unit 63.

As in the case of the timer 53, the drilling end determination section 57 is activated at the start of welding and starts counting pulse signals from the timer 53. When the count value matches the drilling time data in the storage unit 55, it is determined that the drilling of the upper plate 41 has been completed (the end of the initial stage of welding), and the control unit 59 and the welding end determination unit 61 determine that. And the driving is stopped.

Receiving the above-mentioned notification from the drilling end determining section 57, the welding end determining section 61 starts up and counts the pulse signals from the timer 53. The count value is stored in the storage section 55.
The upper plate 41 and the lower plate 4
It is determined that the welding of No. 2 has been completed, the control unit 59 is notified of this fact, and the driving is stopped.

Upon receiving the above notification from the welding end determining unit 61, the finishing processing determining unit 51 starts up and counts the pulse signals from the timer 53, and the count value is stored in the storage unit 5.
When the finish processing time data in 5 is matched, it is determined that the finish processing has been completed, and that fact is notified to the control unit 59 and the driving is stopped.

The control section 59 places the plasma power supply 31, the gas controller 32, the gas flow rate switch 26, and the filler feeder 28 under the control thereof through the interface section 63.

During the period from the start of welding to the end of drilling of the upper plate 41, the control unit 59 performs the following based on the pulse current value data.
By controlling the plasma power supply 31, a pulse current having a predetermined duty ratio as a welding current is applied between the torch 21, the filler 29 and the work 22. In the above-mentioned period, the control unit 59 supplies the plasma gas having a larger flow rate than that after the end of the drilling to the welding portion of the workpiece 22 by controlling the gas controller 32 based on the plasma gas flow rate data. The recognition of the completion of the drilling by the control unit 59 is based on the notification from the drilling completion determination unit 57.

When receiving the notification of the completion of the drilling of the upper plate 41 from the drilling completion determining unit 57, the control unit 59 controls the plasma power supply 31 based on the constant current value data instead of the pulse current value data. At the same time, the gas controller 32 is controlled based on the relatively small plasma gas flow data instead of the relatively large plasma gas flow data. Then, the filler feeding device 28 is started to immediately start the filler feeding to the welding portion. In this filler feeding operation, the control unit 59 sets the filler feeding amount to a small value at the beginning of the feeding based on the filler feeding amount control data,
The feeding speed of the filler feeding device 28 is controlled so as to gradually increase as time passes.

Upon receiving notification of the end of welding of the upper plate 41 and the lower plate 42 from the welding end determining unit 61, the control unit 59 controls the filler feeding device 28 to immediately stop the filler feeding to the welded portion. . At the same time, the control section 59 controls the plasma power supply 31 based on the larger constant current value data to apply a constant current having a value larger than the current value at the time of welding between the torch 21 and the work 22. The application of the constant current having a large value is continued until the finish processing end determining unit 51 notifies that the finish processing has been completed.

FIG. 5 is a timing chart showing the operating states of the above-described plasma power supply 31, filler feeder 28, and gas controller 31.

In FIG. 5, when welding is started at time t 0, the control unit 5 of the plasma power supply 31 and the gas controller 32
9 is started.

That is, a pulse current having a predetermined duty ratio is applied between the torch 21 and the work 22 from the plasma power source 31 from the time t0 to the time t1 when the drilling of the upper plate 41 is completed, and the gas controller is operated. By controlling 32, a larger amount of plasma gas is supplied to the welding portion of the work 22 than after the end of the drilling.

Next, when it is confirmed at the time t1 that the drilling of the upper plate 41 has been completed, from the time t1 to the time t2 when the feeding of the filler 29 is completed, the above-mentioned constant current is supplied from the plasma power source 31 to the torch 21. And a relatively small amount of plasma gas flows by controlling the gas controller 32. Then, the filler supply to the welded portion from the filler supply device 28 is started immediately. The feed amount of the filler 29 is smallest at time t1 and gradually increases from time t1 to time t2. The reason why such a filler supply amount control is performed is that the filler 29 is hard to melt because the filler is completely cooled at the start of the supply. The small flow of the plasma gas is continued until the time t3 at which the finishing of the workpiece 22 is completed. The start of the supply of the filler 29 does not necessarily have to be immediately after the end of the perforation of the upper plate 41, and may be slightly before or after the end of the perforation.

If the plasma current (arc current) supplied from the plasma power supply 31 is IE, the filler 29 is supplied into the plasma arc 40 generated between the workpiece 22 and the torch 21. IE is diverted to the filler 29 side and the work 22 side through the electric wiring 44. Therefore, the current flowing to the filler 29 side is IF,
If the current flowing on the work 22 side is Iw, then naturally, IE =
IF + Iw is established. When the present inventors conducted experiments, most of the plasma current IE flows as the current IF to the filler 29 side during the filler feeding, and hardly flows to the work 22 side, and therefore, the current Iw is extremely small. It was confirmed that the amount of heat input to the work 22 (the upper plate 41) was also small. As described above, since the amount of heat input to the work 22 can be reduced, it is possible to restrict a wide range of molten portion from dropping from the upper plate 41 to the lower plate 42 at a time, so that the galvanized layer on the lower plate 42 side can be prevented. Explosion can be prevented.

Next, when the end of welding of the upper plate 41 and the lower plate 42 is confirmed at the time t2, the filler feed to the welded portion is immediately stopped by controlling the filler feeder 28. At the same time, by controlling the plasma power supply 31 based on the larger constant current value data, a constant current (arc current) larger than the constant current value during welding is applied between the torch 21 and the work 22. . The application of the constant current having a large value is continued until time t3 (at the time when finishing is completed) at which smoothing of the swelling portion of the filler 29 at the welding location ends. Here, the reason why the arc current value is set to a large value is that the pressure of the plasma gas blown to the welding portion of the work 22 is increased by setting the arc current value to a large value, thereby melting the swelling portion of the filler 29 and thereby forming a concave portion. Because you can do it.

In this manner, between the time t2 and the time t3, the raised portion of the filler 29 is smoothed. When the time t3 is reached, it is recognized that a series of finishing is completed, and the plasma power supply 31 and the gas The driving of the controller 32 is stopped.

FIG. 6 is an explanatory diagram showing the steps of plasma arc spot welding using the welding apparatus having the above configuration.

In FIG. 6, when a high-temperature plasma arc 40 as shown in FIG. 6A is generated between the plasma torch 21 and the upper plate 41 at the start of welding, a gap between the upper plate 41 and the lower plate 42 is detected. At the same time, a hole 41a is formed in the upper plate 41 by the heat of the plasma arc 40 as shown in FIG. Then, the lower plate 42 is also heated through the holes 41a.

In this state, the upper plate 41 is formed using a high-pressure plasma gas and a large value of arc current (plasma current).
Since the filler 29 has not been fed yet because of the necessity of drilling holes, the arc current I
E is all flowing to the work 22 side as the current IW. Therefore, the molten portion of the upper plate 41 is blown off by the high-pressure plasma gas as shown in FIG. And
When the hole 41a is formed in the upper plate 41, the molten portion of the upper plate 41 falls on the lower plate 42 through the hole 41a, and the lower plate 4
Although it comes into contact with the galvanized layer of No. 2, the explosion as shown in FIG. As described above, it is necessary to make a hole in the upper plate 41 at the initial stage of welding with a small melting diameter, and it is preferable that the drilling be completed in a short time, and supply of the filler 29 serving as a means for reducing the amount of heat input to the work 22. Is preferably performed after the completion of the perforation of the upper plate 41. In this step, a part of the lower plate 42 is melted.

Next, immediately after the completion of the above-described drilling, the feeding of the molten filler 29 from the filler feeding device 28 toward the hole 41a is started. This filler 29 is shown in FIG.
As shown in FIG. 4C, the hole 4a is stacked on the molten portion of the lower plate 42 through the hole 41a, so that
As shown in FIG. 6 (d), the hole 41a is gradually filled up.

Thus, the filler 29 in the molten state is
Is charged toward the hole 41a, the filler 29 and the work 22 are electrically connected to each other.
Most of the current becomes the current IF flowing on the filler 29 side, and as a result, the amount of heat input to the work 22 (the upper plate 41) is suppressed.

Thus, the upper plate 41 and the lower plate 42 can be welded while the amount of heat input to the upper plate 41 is minimized (that is, the melting range of the upper plate 41 is kept as narrow as possible). Therefore, there is no such a problem that an explosion occurs when the upper plate 41 falls over a wide area. In addition,
As shown in FIG. 6E, when the welded portion is raised by the filler 29, the raised portion is smoothed by the method described with reference to FIG. That is,
As the finishing process, the arc current value is set to a large value for a predetermined time to increase the pressure of the plasma gas blown to the welding portion of the work 22, thereby melting and smoothing the raised portion of the filler 29.

As described above, according to the embodiment of the present invention, when drilling a hole in the upper plate 41, a high-pressure plasma gas and a large arc current are used before the filler 29 is supplied. Drilling of the plate 41 can be reliably performed in a short time. After the end of drilling, most of the arc current IE flows as the current IF to the filler 29 side.
The amount of heat input to the work 22 (the upper plate 41) can be suppressed, whereby the melted portion of the upper plate 41 is narrowed, and the melted portion of the upper plate 41 falls on the lower plate 42 over a wide range, and explosion occurs. Can be prevented. Further, when the welded portion rises due to the filler 29, the pressure of the plasma gas blown to the welded portion of the work 22 is increased by setting the arc current value to a large value for a predetermined time as necessary, thereby increasing the height of the raised portion. Smoothing can also be performed.

FIG. 7 is a timing chart showing the operation states of the plasma power supply 31, the filler supply device 28, and the gas controller 31 according to a first modification of the embodiment of the present invention.

In this modification, a pulse current (arc current) having a peak value larger than a constant current applied at the time of filler feeding is applied in the finishing step shown at time t2 to time t3, thereby making the filler 29 It is characterized by smoothing the raised portion. In addition,
As for the plasma gas, the same flow rate as that at the time of filler supply is continuously supplied as in the above-described embodiment. Further, the arc current between the time t1 and the time t2 is not a constant value, but can be a slope-shaped current so that the value at the time t2 becomes small, so that the effect of reducing the amount of heat input to the work 22 can be enhanced. At this time, time t
The reason why the current value is set so that the value at 1 becomes larger than the value at time t2 is to improve the fusion between the melted filler 29 and the workpiece 22 immediately after the start of filler feeding.

As described above, by setting the arc current to a large value, the pressure of the plasma gas blown to the welding portion of the work 22 can be increased to smooth the raised portion of the filler 29. If the pressure is too high, a problem occurs that a hole is formed in the filler 29 portion. Therefore, in the present modification, the large current applied during the smoothing of the raised portion is generated in a pulse shape, thereby making it easy to adjust the pressure of the plasma gas by changing the pulse width and the number of pulses. is there. In addition, the fluctuation of the plasma gas pressure causes the molten pool to vibrate and promote smoothing.

FIG. 8 is a timing chart showing the operation states of the plasma power supply 31, the filler feeder 28, and the gas controller 31 according to a second modification of the embodiment of the present invention.

In this modification, while the constant current applied at the time of filler supply is continuously applied in the finishing process, the plasma gas flow rate having a peak value larger than the plasma gas flow rate supplied at the time of filler supply is maintained. Is supplied in the form of a pulse, thereby smoothing the raised portion of the filler 29.

In the first modification shown in FIG. 7, the arc current having a large peak value applied at the time of finishing is pulsed to smooth the swelling portion of the filler 29. In this modification, the plasma gas flow rate is set to be pulsed, so that the filler 2
9 were to be smoothed. Thereby, similarly to the first modification shown in FIG. 7, the pressure of the plasma gas blown to the welding portion of the work 22 can be adjusted.

The contents described above relate to one embodiment of the present invention and its modifications, and do not mean that the present invention is limited only to the above contents.

For example, in the above embodiment, the detection of the hole 41a formed in the upper plate 41 is performed in advance by the storage unit 5 from the start of welding.
5 is performed by checking whether the drilling time stored in the storage device 5 has elapsed. Alternatively, the arc voltage applied between the torch 21 and the work 22 (filler 29) may be monitored. Can be done,
Optical sensor, heat sensor, or CCD (solid-state image sensor)
It is also possible to detect a camera or the like as a detecting means.

In the above embodiment, as an example of the means for reducing the amount of heat input to the upper plate 41, the filler 29 fed to the welding location is used. However, the cap 37 provided on the outer periphery of the torch 21 of FIG.
In the case of welding by contacting the upper plate 41, a method of reducing the amount of heat input to the upper plate 41 by making the cap 37 a member having a higher thermal conductivity than the work 22 may be used. In this case, the member arranged in contact with the outer peripheral portion of the welded portion is cooled by cooling water since the amount of heat absorbed from the upper plate 41 decreases as the temperature increases due to repeated welding. Taking leads to stable welding. Further, a heat conductive member other than the cap 37 may be disposed on the work 22 on the outer peripheral portion of the welding portion to absorb heat. Further, the shield gas supplied toward the welding portion of the work 22 can be used as a means for reducing the amount of heat input to the upper plate 41. As the shielding gas, a non-oxidizing gas having a relatively high thermal conductivity, for example, a hydrogen gas or a mixed gas of a helium gas and an argon gas is preferable.

In the above description, the case where a base material coated with a substance having a boiling point lower than the melting point of the base material, such as a steel material whose surface is coated with a galvanized layer, is used as the work 22, has been described. Can naturally be applied to the case where a material other than the above-described steel material is used as a work. In addition, it is of course possible to use the above-described units in appropriate combinations.

[0068]

As described above, according to the present invention,
An arc welding apparatus capable of preventing a molten portion of a work from exploding during welding can be provided.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a blast generated in plasma arc spot welding.

FIG. 2 is a perspective view showing an overall configuration of an embodiment of the present invention implemented as a plasma arc spot welding apparatus.

3 is a block diagram showing both the configuration of the welding power source in FIG. 2 and elements related to the welding power source.

FIG. 4 is a block diagram showing a configuration of a welding controller of FIG. 2;

FIG. 5 is a timing chart showing an operation state of each part of the plasma arc spot welding apparatus according to the embodiment.

FIG. 6 is an explanatory view showing a plasma arc spot welding process using the plasma arc spot welding apparatus according to one embodiment.

FIG. 7 is a timing chart showing an operation state of each part of the plasma arc spot welding apparatus according to the first modification of the embodiment;

FIG. 8 is a timing chart showing an operation state of each part of the plasma arc spot welding apparatus according to a second modification of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 Plasma torch 22 Work 23 Welding power supply 24 Robot controller 25 High frequency unit 27 Filler nozzle 28 Filler feeding device 29 Filler 30 Robot 31 Plasma power supply 32 Gas controller 33 Clearance judging device 34 Welding controller 40 Plasma arc 41 Upper plate 42 Lower plate 43 Gap 44 Electric wiring 51 Finishing processing end determination unit 53 Timer 55 Storage unit 57 Drilling end determination unit 59 Control unit 61 Welding end determination unit 63 Interface unit 65 Current detector

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Iwao Kurokawa 1200, Manda, Hiratsuka-shi, Kanagawa Prefecture, Komatsu Ltd.

Claims (22)

[Claims] 1. An arc welding apparatus comprising: means for setting a work and a filler supplied to a welding portion of the work at the same potential. 2. The arc welding apparatus according to claim 1, wherein the supply of the filler is started when a hole is formed in an upper plate of the work. 3. The arc welding apparatus according to claim 1, wherein the supply amount of the filler is the smallest at the start of the supply,
An arc welding apparatus controlled to increase with time. 4. An arc welding apparatus comprising means for reducing the amount of heat input to a workpiece after the initial stage of welding compared to the initial stage of welding. 5. An arc welding apparatus according to claim 4, wherein said heat input amount reducing means is a shielding gas supplied toward a welding portion of said workpiece. 6. The arc welding apparatus according to claim 5, wherein the shielding gas is a non-oxidizing gas having a relatively high thermal conductivity. 7. The arc welding apparatus according to claim 4, wherein said heat input amount reducing means is means for cooling a welding portion of said work. 8. The arc welding apparatus according to claim 7, wherein said cooling means is a member placed near a welding portion of said work and having a higher thermal conductivity than said work. Welding equipment. 9. The arc welding apparatus according to claim 4, wherein said heat input amount reducing means is a filler supplied to a welding portion of a workpiece. 10. The arc welding apparatus according to claim 9, wherein the supply of the filler is started when a hole is formed in an upper plate of the work. 11. The arc welding apparatus according to claim 9, wherein the supply amount of the filler is smallest at the start of the supply,
An arc welding apparatus controlled to increase with time. 12. The arc welding apparatus according to claim 4, wherein the heat input amount reducing means is a filler supplied to a welding portion of the work, and further comprising means for vibrating the welding portion of the work. And arc welding equipment. 13. The arc welding apparatus according to claim 12, wherein the vibrating means is activated when the supply of the filler to the welding portion of the workpiece is completed. 14. The arc welding apparatus according to claim 12, wherein said vibration means is means for supplying a pulsed plasma gas to a welding portion of said workpiece. 15. The arc welding apparatus according to claim 14, wherein a peak value of the supply amount of the pulsed plasma gas is set to be larger than that at the time of filler supply. 16. The arc welding apparatus according to claim 12, wherein said vibration means is means for applying a pulsed arc current between said workpiece and said electrode. 17. The arc welding apparatus according to claim 16, wherein a peak value of the supply amount of the pulsed arc current is set to be larger than that at the time of filler supply. 18. The arc welding apparatus according to claim 4, wherein the initial stage of the welding is from a start of the welding to a time when a hole is formed in an upper plate of the work. 19. The arc welding apparatus according to claim 18, wherein the detection of the hole formed in the upper plate of the work is performed by determining whether a predetermined time has elapsed from the start of welding. Characteristic arc welding equipment. 20. The arc welding apparatus according to claim 18, wherein the detection of a hole formed in an upper plate of the work monitors an arc voltage applied between an electrode for arc welding and the work. An arc welding apparatus characterized by being performed by: 21. A means for supplying a filler to a welding portion of a work, and a means for setting the work and a filler supplied to the welding portion of the work to the same potential. An arc welding apparatus controlled to start supplying the filler when a hole is formed in an upper plate of a work. 22. A means for supplying a filler to a welding portion of the work, a means for setting the work and the filler supplied to the welding portion of the work to the same potential, and a means for vibrating the welding portion of the work. The filler supply means is controlled so that the supply of the filler is started when a hole is formed in the upper plate of the work, and the vibration means completes the supply of the filler to the welding portion of the work. Arc welding equipment that is controlled to start when.