JP5558871B2 - Arc welding equipment - Google Patents

Description

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

  In consumable electrode type or non-consumable electrode type gas shielded arc welding, shield gas such as carbon dioxide gas and argon gas is blown out to the arc and molten pool to shield it from the atmosphere, and the atmosphere enters the welding atmosphere. It is necessary to prevent. It is important that the flow rate of the shielding gas is within a certain allowable range. When the gas flow rate is small, the arc state becomes unstable due to the intrusion of the atmosphere into the welding atmosphere, so that blowholes are generated or a large amount of spatter is generated. Conversely, if the gas flow rate is too high, turbulent flow may occur, resulting in poor shielding or insufficient melting. As a result, the appearance of the weld bead may be deteriorated, resulting in poor welding.

  In a general arc welding apparatus in which the shield gas is turned ON / OFF with a solenoid valve, an excessive flow of shield gas is ejected during the preflow process required when the solenoid valve is opened, that is, when welding is started. This phenomenon is expressed as rush current below. The rush flow differs in peak flow rate and duration time depending on the pipe length, pressure, time elapsed since the last gas OFF, etc., and therefore the time from when the shield gas is jetted until the flow rate falls within the allowable range also differs. An example is shown below. Note that the elapsed time from the previous gas OFF means the elapsed time from the shield gas output stop in the previous welding section when there are a plurality of continuous welding sections.

  FIG. 5 is a diagram for explaining the state of the rush of shielding gas. The figure shows how the gas flow rate changes with time depending on how many seconds have elapsed since the last gas OFF when the set flow rate is 15 liters / minute. FIG. 4A shows the flow rate change when the elapsed time from the previous gas OFF is 4 seconds. Similarly, FIG. 7B shows the flow rate change at 3 seconds, FIG. 10C shows 2 seconds, FIG. 10D shows 1 second, and FIG. 9E shows 0.5 seconds. . As shown in the figure, for a while after opening the solenoid valve, an excessive flow of gas is ejected by rush flow, and with the passage of time, the set flow rate determined by the gas flow rate setting device (15 liter / Minutes). Assuming that the preflow time is set to 0.5 seconds, for example, in FIG. 5A, the arc start process is performed in a state where a shield gas of about 42 liters / minute is output. There is a possibility that poor welding as described above may occur.

  Patent Documents 1 and 2 disclose techniques for suppressing rush flow at a welding start portion. Patent Document 1 discloses an arc welding apparatus in which two electromagnetic valves are provided in series and are simultaneously turned ON / OFF (hereinafter referred to as Prior Art 1). Further, Patent Document 2 discloses a welding apparatus provided with a mechanical gas flow rate control means such as an orifice (hereinafter referred to as Prior Art 2). According to the prior arts 1 and 2, by suppressing the rush using mechanical means, it is possible to prevent the occurrence of poor welding and to save the consumption of shield gas. Yes.

  On the other hand, it is necessary not only to suppress the rush flow at the welding start portion but also to maintain the gas flow rate during arc welding at an optimum flow rate. As described with reference to FIG. 5, the gas flow rate becomes constant by approaching the set flow rate determined by the gas flow rate regulator after the rush flow at the welding start portion is settled. If it becomes constant at an appropriate gas flow rate, it will not lead to poor welding. However, for example, when welding is performed using an arc welding apparatus such as an arc welding robot, it is common that one workpiece has a plurality of welded portions, and the groove shape and the welding are determined depending on the welded portions. In many cases, the method and thickness are different. In such a case, it is desirable to change the set flow rate of the shielding gas in accordance with each welding site. For example, there is often no problem even if the set flow rate of the shield gas is reduced when the groove shape is a horizontal fillet than when the groove shape is a stacked fillet. However, since the gas flow rate is a fixed amount determined by the gas flow regulator, the gas flow rate during arc welding may be used with a large amount. In this case, there is a possibility that the shield gas is wasted.

  A technique for solving this problem is disclosed in Patent Document 3. Patent Document 3 discloses a gas processing apparatus that dynamically controls a gas flow rate using a mass flow controller (hereinafter referred to as Conventional Technology 3). In general, the mass flow controller can change the setting of the gas flow rate from the outside, and controls the actual gas flow rate to the set gas flow rate by the built-in gas flow rate detector and gas flow rate regulator, A gas flow controller alone can output and stop gas. According to the prior art 3, the optimum flow rate can be maintained by dynamically controlling the gas flow rate, and the consumption of shield gas can be saved.

  As described above, in the conventional techniques 1 and 2, it is possible to suppress the rush flow at the welding start portion, but the gas flow rate cannot be changed dynamically, so the gas flow rate during arc welding is set to an optimum value. It cannot be adjusted. On the other hand, in the prior art 3, by using a mass flow controller, it is possible to suppress the rush flow at the welding start portion and to adjust the gas flow rate during arc welding to an optimum value. However, there are problems to be described later.

Japanese Patent Laid-Open No. 62-207584 JP 2006-326677 A Japanese Patent Laid-Open No. 8-200434

  FIG. 6 is a diagram showing a change in the flow rate of the shield gas in the prior art. FIG. 4A is a timing chart of the gas control signal, which is turned from OFF to ON at time t1. FIG. 5B is a diagram showing how the gas flow rate changes with time as a result of turning on / off the gas control signal. In FIG. 6B, a waveform Ha shows a waveform when the shield gas is controlled by only one solenoid valve, and the waveform Hb is a gas flow rate controlled by the mass flow controller of the above-described prior art 3. The waveform is shown.

  In the prior art 3, as shown by the waveform Hb, the gas flow rate is gradually increased to the set flow rate during the period from time t1 to t2 (about 1 second, hereinafter referred to as set flow rate arrival time). Is reaching. The mass flow controller suppresses the rush flow by taking a certain amount of time until the actual gas flow rate reaches the set flow rate.

  If welding is started during the above-described set flow rate arrival time, a necessary gas flow rate is not ensured, which may cause a welding defect due to defective shielding. In order to secure the necessary gas flow rate at the start of welding, it is necessary to wait for the gas flow rate to reach the set flow rate, which causes a problem of causing a delay in cycle time. Although there is a high-performance mass flow controller with the above-described set flow rate arrival time of about 0.3 seconds, there is a problem that it is very expensive and difficult to introduce.

  Accordingly, an object of the present invention is to provide an arc welding apparatus that can immediately secure a necessary gas flow rate at the start of welding using a gas solenoid valve and a relatively inexpensive mass flow controller.

The first invention is
It has a mass flow controller that outputs, stops, and adjusts the flow of shield gas by external signal input, and has a gas passage for supplying the shield gas from a gas supply source to the welding torch via the mass flow controller In arc welding equipment,
A gas solenoid valve provided in a gas passage between the welding torch and the mass flow controller;
Gas control means for outputting an electromagnetic valve open / close signal to the gas electromagnetic valve to control the open / close operation and outputting a gas control signal to the mass flow controller,
When the shielding gas is stopped, the gas control means first closes the gas solenoid valve, then stops the gas output from the mass flow controller after a predetermined delay time has elapsed, and starts the next gas output. In some cases, the arc welding apparatus is characterized in that gas output is started from the mass flow controller simultaneously with opening the gas solenoid valve.

According to a second aspect of the present invention, in the arc welding according to the first aspect, the gas control means is a robot controller that drives and controls a manipulator equipped with the welding torch on the basis of teaching data prepared in advance. Device.

A third invention is the arc welding apparatus according to the second invention, wherein the delay time can be set by a teach pendant for creating the teaching data.

  According to the first aspect of the present invention, both the gas solenoid valve and the mass flow controller are provided. When the shield gas is stopped, the gas solenoid valve is first closed, and then a gas stop signal is output to the mass flow controller after a predetermined delay time has elapsed. The shield gas is stopped. As a result, the gas passage between the gas solenoid valve and the mass flow controller is filled with a shielding gas having a predetermined pressure or higher. At the next gas output, the gas is output from both the gas solenoid valve and the mass flow controller at the same time, so that the filled shield gas is released at once and a small rush current that does not affect the welding quality occurs. In addition, the gas flow rate required for starting welding can be secured immediately.

According to the second invention, the gas output control gas solenoid valve and for a mass flow controller, by which is adapted to perform a robot controller, without using a special control device, easily effect the first invention exhibited It can be demonstrated.

According to the third invention, since the delay time can be set by the teach pendant for creating the teaching data, in addition to the effect produced by the first and second inventions, the delay time is set to the gas pipe. It can be arbitrarily set according to the welding environment such as the diameter and gas pressure.

It is a block diagram of the arc welding apparatus which concerns on this invention. It is a connection diagram for demonstrating the gas passage of the arc welding apparatus which concerns on this invention. It is a functional block diagram which shows the internal structure of a robot controller. It is a figure for demonstrating the output control of the shield gas by this invention. It is a figure for demonstrating the mode of the rush of gas. It is a figure which shows the flow volume change of the shield gas in a prior art.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described based on examples with reference to the drawings.

  FIG. 1 is a configuration diagram of an arc welding apparatus 1 according to the present invention. As shown in the figure, the arc welding apparatus 1 is roughly constituted by a manipulator 14, a teach pendant 15, a robot controller 16, and a welding power source 3.

  In the figure, a manipulator 14 automatically performs arc welding on a workpiece 2, and includes a plurality of arm portions and a wrist portion, and a plurality of servo motors (not shown) for rotationally driving them. And is composed of. A welding torch 7 is attached to the tip of the upper arm of the manipulator 14. The welding torch 7 is for guiding a welding wire 13 having a diameter of about 1 mm wound around a wire reel (not shown) to a taught welding line on the workpiece 2.

  The teach pendant 15 inputs each teaching point and welding condition (welding current, welding voltage welding speed, etc.) of the section for welding as a work program Dw, or presets a gas flow rate set value Gv and a delay time Dt. These are input to the robot controller 16. The gas flow rate set value Gv is an optimum flow rate according to the welding location, and a desired value can be determined in advance by the teach pendant 15. The delay time Dt is a time for adjusting a timing for closing the gas solenoid valve 33 described later and a gas stop timing by the mass flow controller 31.

  The robot controller 16 interprets the work program Dw input from the teach pendant 15 and outputs an operation control signal Mc to the manipulator 14 at a predetermined timing based on the interpretation result. Similarly, a welding control signal Ws, a solenoid valve opening / closing signal Ds, a gas output signal Mg, and a gas flow rate setting signal Ms are output to the welding power source 3.

  The welding power source 3 inputs the welding control signal Ws from the robot controller 16 and supplies power between the welding torch 7 and the workpiece 2. Further, an electromagnetic valve opening / closing signal Ds from the robot controller 16 is input, and a command signal for opening / closing a gas electromagnetic valve 33 described later is output. Further, the gas output signal Mg and the gas flow rate setting signal Ms are input, and a command signal for outputting or stopping the shield gas or setting the flow rate of the shield gas is output to the mass flow controller 31 described later.

  The mass flow controller 31 is connected to the welding power source 3, and outputs or stops the supply of the shielding gas according to the input from the welding power source 3. Further, the flow rate of the shield gas supplied from the gas cylinder 30 is adjusted so that the gas flow rate set value Gv is set in advance. The gas solenoid valve 33 is also connected to the welding power source 3 and opens and closes the solenoid valve in response to an input from the welding power source 3.

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

  FIG. 2 is a connection diagram for explaining a gas passage of the arc welding apparatus according to the present invention. In the figure, the shield gas filled in the gas cylinder 30 is supplied to the mass flow controller 31 through the upstream gas passage 34a. The mass flow controller 31 adjusts the flow rate of the shield gas. The shield gas after the flow rate adjustment is supplied to the downstream gas passage 34 b through the airtight chamber 32. The downstream gas passage 34 b is disposed along the side surface of the manipulator 14, and is connected to a gas electromagnetic valve 33 provided in the vicinity of the welding torch 7. The gas solenoid valve 33 supplies the shielding gas to the welding torch 7 through a gas hose (not shown) provided inside the conduit cable 35 by opening / closing operation thereof. As a result, shield gas is ejected from the welding torch 7.

  FIG. 3 is a functional block diagram showing the internal configuration of the robot controller 16. The robot controller 16 includes a microcomputer, various memories, and the like. More specifically, the work program analysis unit 21, the hard disk 22, the trajectory planning unit 23, the RAM 8, the buffer 24, the servo control unit 25, and the servo drive unit 26. A current position monitoring unit 27 and a welding control unit 28 are provided.

  The hard disk 22 as a storage means is a non-volatile memory, and 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 the work program Dw stored in the hard disk 22 for each teaching step and analyzes the contents. For example, the work program analysis unit 21 reads a movement command (consisting of data such as coordinates and speed information) included in the work program and notifies the trajectory planning unit 23 of the movement command. Further, the timing for starting and ending the gas output is obtained and notified to the trajectory planning unit 23.

  The trajectory planning unit 23 stores various movement commands sent from the work program analysis unit 21 in the buffer 24. This movement command is also given gas output / stop timing and the like. Further, the trajectory planning unit 23 reads out the movement command stored in the buffer 24, makes a trajectory plan for the welding torch 7 based on the command, and servo-controls information such as the rotation angle and rotation speed of each motor of the manipulator 14. Notify the unit 25.

  The buffer 24 includes a so-called first-in first-out (FIFO) memory, and stores a movement command sent from the trajectory planning unit 23.

  The servo control unit 25 sends a drive signal to the servo drive unit 26 to rotationally drive each motor of the manipulator 14 based on the track plan sent from the track planning unit 23. The servo control unit 25 acquires an output from an encoder (not shown) and sends the information to the current position monitoring unit 27.

  The servo drive unit 26 outputs an operation control signal Mc to each motor based on a command from the servo control unit 25.

  The current position monitoring unit 27 monitors the current position of the welding torch 7 based on a detection signal from an encoder (not shown) provided in each motor of the manipulator 14.

  The welding control unit 28 outputs various commands from the current position monitoring unit 27 to the welding power source 3 at an appropriate processing timing, thereby causing welding by the welding torch 7 and ejection of shield gas. More specifically, the welding control unit 28 requires the electromagnetic valve opening / closing signal Ds and the gas output signal Mg, which are necessary for injecting the shielding gas to the welding power source 3 at the processing timing specified by the current position monitoring unit 27. And a gas flow rate setting signal Ms. Further, the welding control unit 28 outputs a welding control signal Ws for performing 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 sends an operation control signal Mc to each motor of the manipulator 14 based on a drive command from the servo control unit 25.

  Next, the operation of the arc welding apparatus 1 will be described. When an activation signal is input to the robot controller 16, the work program analysis unit 21 interprets the work program Dw, performs a calculation such as a trajectory plan, and outputs an operation control signal Mc to each motor of the manipulator 14 based on the calculation result. At the same time, a welding control signal Ws, a solenoid valve opening / closing signal Ds, a gas output signal Mg, a gas flow rate setting signal Ms, and the like are output to the welding power source 3. As a result, the welding torch 7 reaches the welding start position, and the shield gas corresponding to the gas flow rate set value Gv is output. After starting the welding, the welding torch 7 is moved to the welding end position, and then the welding is ended, and the afterflow control is performed. A series of operations so far are the same as those of the above-described conventional technology.

  When a plurality of welding sections to be welded are taught in the work program Dw, the above-described series of steps are sequentially executed for each of the plurality of welding sections. The following processing is performed when the shield gas is stopped and when the output of the shield gas is started in the next welding section so that a necessary gas flow rate can be secured immediately at the start of welding.

  FIG. 4 is a diagram for explaining output control of shield gas according to the present invention. FIG. 4A shows a timing chart of ON / OFF (open / close) of the gas solenoid valve 33, and FIG. 2B shows an ON / OFF (gas output / stop) of the mass flow controller 31. The figure (c) shows how the gas flow rate changes with time at the start of the next welding when the shielding gas is stopped and output at the timings of the figures (a) and (b). It is the figure shown with the waveform Hc. In FIG. 4D, a waveform Ha and a waveform Hb indicated by dotted lines are waveforms in the prior art and are shown for comparison with the waveform Hc according to the present invention. The waveform Ha is a waveform when the shield gas is controlled by only one solenoid valve, and the waveform Hb is a waveform when the gas flow rate is controlled by the mass flow controller of the conventional technique 3.

(1. Time t1)
Time t1 is the timing when the afterflow process is completed. As shown in FIG. 5A, the robot controller 16 outputs a closing operation signal only to the gas electromagnetic valve 33 via the welding power source 3 (turns the electromagnetic valve opening / closing signal Ds OFF). Since the gas electromagnetic valve 33 is closed by this process, the shielding gas is not supplied to the gas passage between the gas electromagnetic valve 33 and the welding torch 7.

(2. Period of time t1 to t2)
During the period from time t1 to time t2, the gas electromagnetic valve 33 is closed, while the mass flow controller 31 continues to output the shield gas. As a result, the gas passage between the mass flow controller 31 and the gas solenoid valve 33 is filled with a shielding gas having a pressure equal to or higher than a predetermined pressure (more than a pressure when supplied in normal time). At this time, by providing the airtight chamber 32, it is possible to prevent the gas passage from being filled with more shielding gas than necessary.

(3. Time t2)
Time t2 is a time at which a predetermined delay time Dt has elapsed from time t1. The robot controller 16 outputs a gas stop signal to the mass flow controller 31 via the welding power source 3 (turns the gas output signal Mg OFF) at the timing of this time t2. By this process, the supply of the shielding gas is completely stopped.

(4. Time t3)
Time t3 is a timing at which the output of shield gas is started in order to perform welding in the next welding section. The robot controller 16 turns on the electromagnetic valve open / close signal Ds to open the gas electromagnetic valve 33). At the same time, the gas output signal Mg is turned ON in order to cause the mass flow controller 31 to start outputting gas.

(5. Time t3 to t4)
By simultaneously turning on the mass flow controller 31 and the gas electromagnetic valve 33, the shielding gas filled in the gas passage between the mass flow controller 31 and the gas electromagnetic valve 33 is released at a stroke. The flow rate change at this time is like a waveform Hc. In the prior art 3 in which the mass flow controller 31 is used alone, the change in the flow rate becomes like the waveform Hb, and there is a fear that the flow rate is insufficient. On the other hand, in the present invention, as shown by the waveform Hc, a small rush current that does not affect the welding quality is generated, and the flow rate (shaded portion) that is insufficient in the prior art 3 can be compensated. .

  Here, the delay time Dt will be supplemented. The flow rate of the shield gas depends on various factors in the welding environment, such as the pipe length 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, and the volume of the chamber 32. Naturally, the delay time Dt also depends on these factors, but it is desirable that the delay time Dt is a time during which a rush current that does not affect the welding quality occurs. As a result of the applicant preparing tens of patterns of the welding environment and repeatedly experimenting with trial and error, the delay time Dt is preferably about 0.5 to 0.6 seconds (hereinafter referred to as a reference value). Is done. Naturally, in the case of a welding environment not included in the pattern, the reference value may not be suitable as the delay time Dt. In this case, the delay time corresponding to the welding environment may be obtained by experiment, or the reference value may be reconsidered according to the actual welding execution result, and adjusted with the teach pendant 15.

  As described above, both the gas electromagnetic valve 33 and the mass flow controller 31 are provided, and when the shield gas is stopped, the gas electromagnetic valve 33 is first closed, and then a gas stop signal is sent to the mass flow controller 31 after a predetermined delay time Dt has elapsed. Is output to stop the shielding gas. As a result, the gas passage between the gas solenoid valve 33 and the mass flow controller 31 is filled with a shielding gas having a predetermined pressure or higher. At the next gas output, the gas is output from both the gas solenoid valve and the mass flow controller at the same time, so that the filled shield gas is released at once and a small rush current that does not affect the welding quality occurs. In addition, the gas flow rate required for starting welding can be secured 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.

  In addition, since an airtight chamber 32 for sealing the shield gas is provided in the middle of the gas passage between the mass flow controller 31 and the gas solenoid valve 33, the gas passage is filled with more shield gas than necessary. Can be prevented.

  In addition, since the robot controller 16 performs the gas output control for the mass flow controller 31, the above-described effects can be exhibited without using a special control device.

  Further, since the delay time Dt can be set by the teach pendant 15, the delay time can be arbitrarily set according to the welding environment such as the diameter of the gas pipe and the gas pressure.

  In the above-described embodiment, the mass flow controller 31 and the gas electromagnetic valve 33 are connected to the welding power source 3. Furthermore, an electromagnetic valve opening / closing signal Ds for causing the gas electromagnetic valve 33 to open / close, a gas output signal Mg for causing the mass flow controller 31 to output / stop the shielding gas, and a flow rate setting for the shielding gas are performed. The robot controller 16 outputs the gas flow rate setting signal Ms to the welding power source 3. Instead of this configuration, the mass flow controller 31 and the gas electromagnetic valve 33 are connected to the robot controller 16, and the robot controller 16 directly outputs the above-described electromagnetic valve opening / closing signal Ds, gas output signal Mg, and gas flow rate setting signal Ms. It is good also as a form which controls by outputting to 31 and the gas solenoid valve 33. FIG.

DESCRIPTION OF SYMBOLS 1 Arc welding apparatus 2 Work 3 Welding power supply 7 Welding torch 13 Welding wire 14 Manipulator 15 Teach pendant 16 Robot controller 21 Work program analysis part 22 Hard disk 23 Trajectory plan part 24 Buffer 25 Servo control part 26 Servo drive part 27 Current position monitoring part 28 Welding control unit 30 Gas cylinder 31 Mass flow controller 32 Chamber 33 Gas electromagnetic valve 34a Upstream gas passage 34b Downstream gas passage 35 Conduit cable Ds Electromagnetic valve open / close signal Dt Delay time Dw Work program Gv Gas flow rate set value Ha Waveform Hb Waveform Hc Waveform Mc Operation control signal Mg Gas output signal Ms Gas flow rate setting signal Ws Welding control signal

Claims (3)

It has a mass flow controller that outputs, stops, and adjusts the flow of shield gas by external signal input, and has a gas passage for supplying the shield gas from a gas supply source to the welding torch via the mass flow controller In arc welding equipment,
A gas solenoid valve provided in a gas passage between the welding torch and the mass flow controller;
Gas control means for outputting an electromagnetic valve open / close signal to the gas electromagnetic valve to control the open / close operation and outputting a gas control signal to the mass flow controller,
When the shielding gas is stopped, the gas control means first closes the gas solenoid valve, then stops the gas output from the mass flow controller after a predetermined delay time has elapsed, and starts the next gas output. Sometimes the gas solenoid valve is opened to start gas output from the mass flow controller at the same time. It said gas control means according to claim 1 Symbol placement of arc welding apparatus characterized in that it is a robot controller for the drive control of the manipulator equipped with welding torch on the basis of the teaching data created in advance. 3. The arc welding apparatus according to claim 2 , wherein the delay time can be set by a teach pendant for creating the teaching data.

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