TWI511829B - Arc welding apparatus - Google Patents

Description

Arc welding device

The present invention relates to an improved arc welding apparatus for gas shielded arc welding.

In the gas-shielded arc welding of the consumable electrode type or the non-consumption electrode type, it is necessary to spray a protective gas such as carbon dioxide or argon gas into the arc and the molten pool to prevent the atmosphere from intruding into the welding atmosphere. In this regard, it is important to limit the flow of protective gas within a certain tolerance. When the gas flow rate is small, the atmosphere intrudes into the welding atmosphere, and the state of the arc becomes unstable. Therefore, a blow hole sometimes occurs, and a large amount of spatter is sometimes generated. Conversely, when there is too much gas flow, turbulence occurs, so that poor protection sometimes occurs, and weld penetration is sometimes insufficient. As a result, the appearance of the solder beads may deteriorate and the soldering may be poor.

A general arc welding device uses a solenoid valve to control the discharge and stop of a protective gas. In this case, in the pre-flow process when the solenoid valve is opened to start the welding, an excessive flow of the protective gas is ejected. Hereinafter, this phenomenon is expressed as a spurt. The peak flow rate and duration of the outflow vary depending on the length of the pipe, the pressure, the elapsed time since the last gas stop. Therefore, the time until the flow rate falls within the allowable range after the protective gas is ejected is also different. The elapsed time from the last gas stop refers to the elapsed time after the protective gas is stopped in the last welding interval in the case where the plurality of welding intervals are continuously present.

The fifth figure shows the elapsed time from the last gas stop. Time varies between different gas flows. The set flow rate of the gas is 15 liters/min. (a) of the fifth figure shows the time variation of the gas flow rate when the elapsed time from the last gas stop is 4 seconds. (b) to (e) of the fifth figure respectively show flow changes when the elapsed time from the last gas stop is 3 seconds, 2 seconds, 1 second, and 0.5 seconds. As shown in the fifth figure, during a short period of time after the solenoid valve is opened, the outflow causes the gas flowing through the helium flow to be ejected. In addition, the gas flow rate approaches the set flow rate (15 liters/min) as time passes. When the forward flow time is set to 0.5 second, in the case of (a) of the fifth diagram, the protective gas is subjected to an arc start process at a flow rate of about 42 liters/minute. In this case, the above-mentioned welding failure may occur.

A technique for suppressing a spurt at the start of welding is disclosed in Japanese Laid-Open Patent Publication No. SHO-62-207584 and No. 2006-326677. Japanese Laid-Open Patent Publication No. SHO-62-207584 discloses an arc welding apparatus in which two electromagnetic valves provided in series are simultaneously turned ON or OFF (Prior Art 1). JP-A-2006-326677 discloses a welding device having a mechanical gas flow rate control means such as a restriction orifice (Prior Art 2). According to the prior art 1, 2, mechanical means are used to suppress the outflow, thereby preventing occurrence of welding defects and saving the consumption of protective gas.

In addition, it is necessary not only to suppress the outflow at the start of welding, but also to maintain the flow rate of the gas in the arc welding at an optimum flow rate. As described above, after the spurt is calm at the start of welding, the gas flow rate approaches the set flow rate determined by the gas flow regulator, and thereafter, it is maintained at a constant value. When the gas flow rate is maintained at a certain value, poor soldering does not occur. However, if an arc welding device such as an automatic arc welding machine is used for welding, a workpiece often has a plurality of welding portions. Further, the groove shape, the welding method, the plate thickness, and the like are often different depending on the welded portion. In this situation, hope The gas flow rate of the protective gas is changed according to the welded portion. For example, the case of horizontal fillet can be used with a smaller set flow rate of protective gas than when the shape of the groove is an overlapping fillet. However, the gas flow rate is maintained at a certain value by the gas flow regulator. Therefore, in arc welding, a large amount of gas is sometimes used at a constant flow rate, and a protective gas is wasted.

A technique for solving this problem is disclosed in Japanese Laid-Open Patent Publication No. Hei 8-200634. Japanese Laid-Open Patent Publication No. Hei 8-200634 discloses a gas processing apparatus that uses a mass flow controller to dynamically control a gas flow rate (Prior Art 3). In general, the mass flow controller can set the gas flow from the outside. A gas flow detector and a gas flow regulator are mounted in the mass flow controller. The gas flow rate detector and the gas flow rate adjuster control the actual gas flow rate to a set value. In addition, even the mass flow controller unit can output or stop the gas. According to the prior art 3, the gas flow rate is dynamically controlled and maintained at an optimum flow rate, thereby saving the consumption of protective gas.

As described above, in the prior art 1 and 2, although the jet flow at the start of welding is suppressed, the gas flow rate cannot be dynamically changed, so that the gas flow rate cannot be adjusted to an optimum value during arc welding. On the other hand, in the prior art 3, the mass flow controller is used to suppress the outflow at the start of welding, and the gas flow rate can be adjusted to an optimum value in the arc welding. However, it has the subject mentioned later.

(a) of the sixth figure shows a timing chart of the gas control signal. As shown in the sixth figure, at time t1, the gas control signal is turned from OFF to ON. (b) of the sixth figure shows the time variation of the gas flow caused by turning on/off the gas control signal. The waveform Ha is a waveform in which the flow rate of the protective gas is controlled by only one solenoid valve; the waveform Hb is a waveform after the gas flow is controlled by the mass flow controller of the prior art 3.

In the prior art 3, as indicated by the waveform Hb, the period from time t1 to time t2 (about 1 second, hereinafter referred to as the set flow rate arrival time), the gas flow rate is gradually increased to reach the set flow rate. The mass flow controller spends some time waiting for the actual gas flow to reach the set flow, thereby suppressing the outflow.

If welding is started before the set flow arrival time, the necessary gas flow rate is not ensured, so welding defects may occur due to poor protection. It takes some time for the gas flow to reach the set flow rate. Therefore, the cycle time becomes long. Although it is possible to utilize a high-performance mass flow controller that sets a flow arrival time of about 0.3 seconds, it is very expensive, so the equipment cost becomes high.

It is an object of the present invention to provide an arc welding apparatus that can use a gas solenoid valve (Gas Solenoid Valve) and a relatively inexpensive mass flow controller to ensure the necessary gas flow rate immediately at the start of welding.

In order to achieve the above object, according to a first aspect of the present invention, an arc welding apparatus having a mass flow controller and a gas passage for performing output and stop of a protective gas after inputting a signal from the outside is provided Flow adjustment, the gas passage is used to supply a protective gas from the gas supply source to the welding torch via the mass flow controller. The arc welding device has a gas solenoid valve disposed between the welding torch and the mass flow controller; and a gas control means for outputting a solenoid valve opening and closing signal to the gas solenoid valve to open and close the gas solenoid valve, and outputting a gas control signal to the mass flow controller . The gas control means first closes the gas solenoid valve when the protective gas is stopped, and then stops outputting the gas from the mass flow controller after a predetermined delay time, and turns on the gas power at the next gas output. The magnetic valve simultaneously outputs gas from the mass flow controller.

As shown in the first figure, the arc welding apparatus 1 is provided with a manipulator 14, a teach pendant 15, an automaton controller 16, and a welding power source 3. The robot 14 automatically performs arc welding on the workpiece 2. The robot 14 has a plurality of arms and a wrist, and a plurality of servo motors for rotationally driving the portions. A welding torch 7 is attached to the end of the front arm of the robot 14. The welding rod 7 of about 1 mm in diameter wound around the electrode reel is guided by the welding torch 7 to the welding line taught on the workpiece 2.

The teaching tray 15 is operated when the welding conditions such as the teaching points, the welding current, the welding voltage, and the welding speed in the section where the welding is performed are input as the work program Dw, or when the gas flow rate setting value Gv and the delay time Dt are set. The operation program Dw, the gas flow rate set value Gv, the delay time Dt, and the like are output from the teaching tray 15 and input to the automaton controller 16 and the gas flow rate set value Gv is an optimum gas flow rate set according to the weld. The gas flow rate setting value Gv is set to a desired value by the prior operation teaching tray 15. The delay time Dt is a timing for adjusting the timing at which the gas solenoid valve 33 to be described later is turned off and the timing at which the mass flow controller 31 stops the gas.

The automaton controller 16 interprets the work program Dw that has been input from the teaching tray 15. The automaton controller 16 outputs the motion control signal Mc to the robot 14 at a timing based on the predetermined interpretation result. Similarly, the automaton controller 16 outputs the welding control signal Ws, the solenoid valve opening and closing signal Ds, the gas output signal Mg, and the gas flow rate setting signal Ms to the welding power source 3.

The welding power source 3 supplies electric power between the welding torch 7 and the workpiece 2 in accordance with the welding control signal Ws from the automatic machine controller 16. Furthermore, The welding power source 3 outputs a command signal for opening and closing the gas solenoid valve 33 to be described later based on the solenoid valve opening/closing signal Ds from the automatic machine controller 16. Further, the welding power source 3 outputs another command signal to the mass flow controller 31 according to the gas output signal Mg and the gas flow rate setting signal Ms, and the other command signal is used to output or stop the protective gas for output, or To set the flow rate of the protective gas.

The welding power source 3 is connected to the mass flow controller 31 and the gas solenoid valve 33. The mass flow controller 31 supplies a protective gas based on a command signal from the welding power source 3, or stops the supply of the protective gas. Further, the mass flow controller 31 adjusts the flow rate of the protective gas supplied from the gas cylinder 30 to the gas flow set value Gv which has been set in advance. The gas solenoid valve 33 is opened and closed based on a signal from the welding power source 3.

Next, the positions of the gas solenoid valve 33 and the mass flow controller 31 will be described.

As shown in the second figure, the gas cylinder 30 is filled with a protective gas. The shielding gas is supplied to the mass flow controller 31 through the upstream side gas passage 34a. The mass flow controller 31 adjusts the flow rate of the protective gas. The flow rate-adjusted protective gas is supplied to the downstream side gas passage 34b through the airtight chamber 32. The downstream side gas passage 34b is disposed along the side surface of the robot 14. The downstream side gas passage 34b is connected to a gas solenoid valve 33 provided in the vicinity of the welding torch 7. The gas hose of the inside of the conduit cable 35 is supplied to the welding torch 7 by the opening and closing of the gas solenoid valve 33. Thus, the protective gas is ejected from the welding torch 7.

As shown in the third figure, the automaton controller 16 is provided with a microcomputer, various memories, and the like. Specifically, the automaton controller 16 includes a work program analysis unit 21, a hard disk drive 22, a track plan unit 23, a RAM 8, a buffer 24, a servo control unit 25, a servo drive unit 26, and current position monitoring. The portion 27 and the welding control unit 28. The hard disk drive 22 as a means of memory is a non-volatile memory. The hard disk unit 22 stores a work program Dw, a delay time Dt, a gas flow rate setting value Gv, and the like in advance.

The work program analysis unit 21 reads out the work program Dw already stored in the hard disk drive 22 in each teaching step, and analyzes the contents. For example, the work program analysis unit 21 reads a movement command composed of data such as coordinates and speed information included in the work program, and notifies the track plan unit 23 of the command. Furthermore, the work program analysis unit 21 obtains the timing of starting and ending the output of the gas, and notifies the track plan unit 23 of the timing.

The track plan unit 23 stores various movement commands sent from the work program analysis unit 21 in the buffer 24. The movement command is also given to the timing of gas output and stop timing. The track planing unit 23 reads the movement command already stored in the buffer 24. The track planing unit 23 creates a track plan of the welding torch 7 based on the movement command, and notifies the servo control unit 25 of information such as the rotation angle and the rotation speed of each of the motors of the robot 14.

The buffer 24 is composed of a memory for so-called first-in first-out (FIFO). The movement command sent from the track planning unit 23 is stored in the buffer 24. The servo control unit 25 transmits a drive signal to the servo drive unit 26 to rotationally drive the motors of the robot 14 based on the track plan sent from the track plan unit 23. The servo control unit 25 acquires an output signal from the encoder and transmits the information to the current position monitoring unit 27.

The servo drive unit 26 outputs an operation control signal Mc to each of the motors in accordance with an instruction from the servo control unit 25. The position monitoring unit 27 now monitors the current position of the welding torch 7 by a detection signal from an encoder provided in each motor of the robot 14. Welding control unit 28 will be from the current position The various commands of the monitoring unit 27 are output to the welding power source 3 at appropriate processing timings. Therefore, welding by the welding torch 7 or a protective gas is ejected. Specifically, the welding control unit 28 outputs the solenoid valve opening/closing signal Ds, the gas output signal Mg, and the gas flow rate setting signal Ms necessary for discharging the protective gas to the welding power source at the processing timing specified by the current position monitoring unit 27. 3. The welding control unit 28 outputs a welding control signal Ws for welding by the welding power source 3 based on the welding control command from the current position monitoring unit 27. The servo drive unit 26 transmits an operation control signal Mc to each of the motors of the robot 14 in accordance with a drive command from the servo control unit 25.

Next, the operation of the arc welding apparatus 1 will be described. When the start signal is input to the automaton controller 16, the work program analysis unit 21 interprets the work program Dw and calculates a track plan or the like. The work program analysis unit 21 outputs an operation control signal Mc to each of the motors of the robot 14 based on the calculation result, and outputs a welding control signal Ws, a solenoid valve opening and closing signal Ds, a gas output signal Mg, and a gas flow rate setting signal to the welding power source 3. Ms et al. As a result, the welding torch 7 moves to the welding start position, and the protective gas is output based on the amount of the gas flow rate setting value Gv, and the welding starts. Thereafter, when the welding torch 7 is moved to the welding end position, the welding is finished, and after-flow control is performed. The above-described series of operations are performed in the same manner as the above-described conventional techniques.

If the operating program Dw teaches a plurality of welding intervals, the above-described series of programs sequentially executes each of the plurality of welding intervals. However, one of the objects of the present invention is to ensure the necessary gas flow rate immediately at the start of welding in the next welding zone. Therefore, the following processing is performed at the time of stopping the protective gas and at the start of the protective gas output in the next welding section.

The fourth diagram (a) shows the timing chart of ON/OFF (opening and closing) of the gas solenoid valve 33, and the fourth diagram (b) shows the timing of ON/OFF (gas output/stop) of the mass flow controller 31. Figure. The waveform Hc indicated by the solid line in the fourth diagram (c) shows the time of the gas flow rate in the case where the protective gas is stopped and outputted at the timings shown in the fourth (a) and fourth (b) diagrams. Variety. For comparison with the waveform Hc according to the present invention, the waveform Ha and the waveform Hb of the prior art are indicated by the dotted line of the fourth diagram (c). The waveform Ha is a waveform in which the flow rate of the protective gas is controlled by only one electromagnetic valve, and the waveform Hb is a waveform obtained by controlling the flow rate of the gas by the mass flow controller of the prior art 3.

[1. Time t1]

At time t1, the timing of the completion of the downstream processing is completed. As shown in the fourth diagram (a), the automaton controller 16 outputs a closing actuation signal only to the gas solenoid valve 33 via the welding power source 3. That is, the automaton controller 16 turns off the solenoid valve opening and closing signal Ds. Therefore, the gas solenoid valve 33 is closed, so the protective gas is not supplied to the gas passage between the gas solenoid valve 33 and the welding torch 7.

[2. Period of time t1~t2]

During the period from time t1 to time t2, on the one hand, the gas solenoid valve 33 is closed, and on the one hand, the protective gas continues to be output from the mass flow controller 31. Therefore, the gas passage between the mass flow controller 31 and the gas solenoid valve 33 is filled with the protective gas at a pressure higher than that at the time of normal supply. At this time, since the airtight compartment 32 is provided, it is prevented that the gas passage is filled with a protective gas or more.

[3. Time t2]

The time t2 is a time after the predetermined delay time Dt has elapsed from the time t1. The automaton controller 16 outputs a stop signal of the gas to the mass flow controller 31 through the welding power source 3 at the timing of time t2. That is, the automaton controller 16 turns off the gas output signal Mg. Therefore, the supply of protective gas is completely stopped.

[4. Time t3]

Time t3 is the timing at which the protective gas output starts in the next welding zone. The automaton controller 16 turns on the solenoid valve opening/closing signal Ds in order to open the gas solenoid valve 33. At the same time, in order to cause the mass flow controller 31 to start outputting the gas, the automaton controller 16 causes the gas output signal Mg to be ON.

[5. Time t3~t4]

The mass flow controller 31 and the gas solenoid valve 33 are simultaneously turned on, so that the previously filled protective gas in the gas passage between the mass flow controller 31 and the gas solenoid valve 33 is released at a time. The waveform Hc shows the change in gas flow rate at this time. In the prior art 3 in which the mass flow controller 31 is used alone, the flow rate change as indicated by the waveform Hb may cause insufficient flow. In contrast, in the present invention, as shown by the waveform Hc, a small outflow which does not affect the degree of welding quality occurs, and the insufficient portion (hatched portion) of the gas flow rate in the prior art 3 is supplemented.

Here, the explanation is added for the delay time Dt. The flow rate of the protective gas is limited by the length of the pipe from the mass flow controller 31 to the gas solenoid valve 33, the pipe diameter, the set pressure of the gas cylinder 30, the set flow rate, the volume of the compartment 32, and the like in the welding environment. influences. Of course, the delay time Dt is also affected by these factors, but the delay time Dt is preferably set to a time when the turbulence does not affect the degree of welding quality. The applicant prepared dozens of types of the above-mentioned welding environment, and tried to repeat the experiment while trying to make a mistake. As a result, the Applicant has found that the expected delay time Dt is about 0.5 to 0.6 seconds. Of course, in the case of a welding environment not containing the above-described type, the above values may not be suitable as the delay time Dt. In this case, the delay time based on the welding environment is determined experimentally, or the reference value is re-evaluated based on the actual welding construction result, and then adjusted by the teaching tray 15.

According to the above embodiment, the following effects can be exhibited.

(1) The arc welding device includes a gas solenoid valve 33 and a mass flow controller 31. When the protective gas is stopped, the gas solenoid valve 33 is first closed, and then, after a predetermined delay time Dt elapses, the mass flow controller 31 outputs a gas stop signal to stop the protective gas. Therefore, the gas passage between the gas solenoid valve 33 and the mass flow controller 31 is filled with a protective gas having a predetermined pressure or more. In addition, at the next gas output, the gas is simultaneously output from both the gas solenoid valve and the mass flow controller. Therefore, the protective gas filled in the gas passage between the gas solenoid valve 33 and the mass flow controller 31 is discharged at a time. Therefore, a small outflow does not affect the degree of welding quality, so that the gas flow rate necessary for the start of welding can be ensured immediately. In addition, since it is not necessary to wait for the gas flow rate to reach the set flow rate, the cycle time can be shortened.

(2) A gas passage between the mass flow controller 31 and the gas solenoid valve 33 is provided with a hermetic compartment 32 for enclosing the protective gas. Therefore, the gas passage is prevented from filling the necessary protective gas.

(3) Since the automatic machine controller 16 controls the gas output by the mass flow controller 31, the above effects can be exhibited without lifting a special control device.

(4) The delay time Dt can be set by the teaching tray 15. Therefore, the operator can arbitrarily set the delay time Dt according to the welding environment such as the diameter of the gas pipe and the gas pressure.

The above embodiment can also be changed as follows.

In the above embodiment, the mass flow controller 31 and the gas solenoid valve 33 may be directly connected to the automaton controller 16. In this case, the solenoid valve opening and closing signal Ds, the gas output signal Mg, and the gas flow rate setting signal Ms are directly output from the automaton controller 16 to the mass flow controller 31 and the gas solenoid valve 33, respectively.

1‧‧‧Arc welding device

2‧‧‧Workpiece

3‧‧‧ welding power supply

7‧‧‧ welding torch

13‧‧‧ welding rod

14‧‧‧ Robot

15‧‧‧Training disk

16‧‧‧Automatic machine controller

30‧‧‧ gas cylinder

31‧‧‧Quality Flow Controller

32‧‧‧ Compartment

33‧‧‧ gas solenoid valve

34a‧‧‧ upstream side gas path

34b‧‧‧ downstream side gas path

The first figure shows a block diagram of the arc welding apparatus of the present invention.

The second figure is a schematic diagram for explaining the gas path of the arc welding device.

The third figure shows a block diagram of the automaton controller.

The fourth figure is a timing diagram for explaining the control of the protective gas output.

The fifth figure is a graph for explaining the gas outflow.

The sixth figure is a graph showing the variation of the conventional protective gas flow rate.

1‧‧‧Arc welding device

2‧‧‧Workpiece

3‧‧‧ welding power supply

7‧‧‧ welding torch

13‧‧‧ welding rod

14‧‧‧ Robot

15‧‧‧Training disk

16‧‧‧Automatic machine controller

30‧‧‧ gas cylinder

31‧‧‧Quality Flow Controller

32‧‧‧ Compartment

33‧‧‧ gas solenoid valve

Claims (4)

An arc welding device having a mass flow controller and a gas passage for performing output, stop, and flow adjustment of a protective gas after inputting a signal from the outside, the gas passage for supplying the protective gas from the gas The source is supplied to the welding torch via the mass flow controller, and the arc welding device is characterized by: a gas solenoid valve, the gas passage provided between the welding torch and the mass flow controller; and a gas control means The gas solenoid valve outputs a solenoid valve opening and closing signal to open and close the gas solenoid valve, and outputs a gas control signal to the mass flow controller; the gas control means first closes the gas solenoid valve when the protective gas stops, and then passes the prescribed After the delay time, the output of the gas from the mass flow controller is stopped, and the gas solenoid valve is opened at the next gas output while the gas is output from the mass flow controller. An arc welding apparatus according to claim 1, wherein said gas passage between said mass flow controller and said gas solenoid valve is provided with a hermetic compartment for enclosing said protective gas. An arc welding apparatus according to claim 1 or 2, wherein the gas control means is an automatic machine controller that drives and controls a robot on which the welding torch is mounted based on teaching materials prepared in advance. The arc welding apparatus of claim 3, wherein the delay time is set by a teaching tray for making the aforementioned teaching materials.