JP5908802B2 - Plasma arc welding method and plasma arc welding system - Google Patents

Description

  The present invention relates to a plasma arc welding method and a plasma arc welding system.

  Conventionally, plasma arc welding methods are known. The torch used in the plasma arc welding method has various structures according to the application. As the torch used in the plasma arc welding method, there are a single-structure torch and a double-structure torch.

  Patent Document 1 discloses a plasma arc welding method using a single structure torch. The single structure torch (plasma torch) disclosed in the document 1 includes an electrode and a nozzle. The nozzle surrounds the electrode. In the plasma arc welding method of the literature 1, a high frequency voltage is applied between the electrode and the nozzle. As a result, a pilot arc is generated between the electrode and the nozzle. Next, in a state where a pilot arc is generated between the electrode and the nozzle, a main arc is generated between the electrode and the object to be heated (workpiece). When the main arc is generated, the pilot arc is extinguished. Then, immediately before extinguishing the main arc, a pilot arc is generated again by applying a voltage (not a high-frequency voltage) between the electrode and the nozzle. In such a method, a pilot arc can be regenerated without applying a high frequency voltage between the electrode and the nozzle.

  Patent Document 2 discloses a plasma arc welding method using a double structure torch. The double-structure torch (plasma arc torch) disclosed in the literature 2 includes a cathode bar, a first nozzle, and a second nozzle. The first nozzle surrounds the cathode bar and the second nozzle surrounds the first nozzle.

Japanese Unexamined Patent Publication No. 63-5875 Japanese Patent No. 3066933

  In the double-structure torch disclosed in Patent Document 2, the first nozzle is interposed between the second nozzle and the cathode bar. Therefore, even if a voltage (not a high frequency voltage) is applied between the cathode bar and the second nozzle while the main arc is generated, the first nozzle is connected to the cathode bar and the second nozzle. Prevents dielectric breakdown from occurring. Therefore, in the method disclosed in Patent Document 2, it is difficult to regenerate a pilot arc between the cathode bar and the second nozzle immediately before extinguishing the main arc without using a high-frequency voltage. Then, a high frequency voltage is applied between the cathode bar and the first nozzle every time the pilot arc is regenerated. If such application of voltage is repeated, there is a risk of failure of a device that performs plasma arc welding and failure of equipment around the device.

  The present invention has been conceived under the above circumstances, and even when a torch having a double structure is used, a plasma arc welding method and plasma arc welding capable of avoiding the application of a high frequency voltage as much as possible. Providing a system is the main challenge.

  According to a first aspect of the present invention, using a torch comprising a non-consumable electrode, an inner nozzle surrounding the non-consumable electrode, and an outer nozzle surrounding the inner nozzle, the non-consumable electrode and the first base material Between the step of energizing the first main arc current between and the step of energizing the first main arc current between the tip of the non-consumable electrode in the first direction toward the first base material and the inner nozzle A first moving step of relatively moving the non-consumable electrode, a step of starting energization of an intermediate pilot arc current between the non-consumable electrode and the outer nozzle after starting the first moving step; After the step of starting energization of the pilot arc current, the step of stopping energization of the first main arc current and the non-consumable electrode and the second while the intermediate pilot arc current is flowing And a step of starting the energization of the second main arc current between the wood, plasma arc welding method is provided.

  Preferably, the method further includes a second movement step of moving the non-consumable electrode relative to the inner nozzle in a second direction opposite to the first direction, and the second movement step includes the second main arc current. This is performed after the step of starting energization.

  Preferably, the step of stopping energization of the first main arc current is performed after the end of the first movement step.

  Preferably, in the first movement step, the non-consumable electrode is moved relative to the inner nozzle so that the tip of the non-consumable electrode moves from the first area to the second area, and the second movement is performed. In the step, the non-consumable electrode is moved relative to the inner nozzle so that the tip of the non-consumable electrode moves from the second region to the first region, and the first region is the inner nozzle The second region is a region located on the first direction side with respect to the opening.

  Preferably, the method further includes a step of continuously maintaining the position of the tip of the non-consumable electrode in the second region from the end of the first moving step to the start of the second moving step.

  Preferably, in the first moving step, a tip of the non-consumable electrode is brought close to the first base material.

  Preferably, the method further includes a step of supplying a start pilot arc current between the non-consumable electrode and the outer nozzle, wherein the step of supplying the first main arc current is performed during the step of supplying the start pilot arc current. To start.

  Preferably, the method further includes a step of supplying an initial pilot arc current between the non-consumable electrode and the inner nozzle, and the step of supplying the initial pilot arc current includes a high frequency between the non-consumable electrode and the inner nozzle. The step of applying the voltage and applying the start pilot arc current is shifted from the step of supplying the initial pilot arc current.

  Preferably, the method further comprises an initial moving step of moving the non-consumable electrode relative to the inner nozzle in a second direction opposite to the first direction, and the step of energizing the start pilot arc current includes the non-consumable step It is started by applying a high frequency voltage between the electrode and the outer nozzle, and the initial movement step is performed after the start of the step of applying the first main arc current.

  According to a second aspect of the present invention, a plasma arc welding system for performing a plasma arc welding method using a torch comprising a non-consumable electrode, an inner nozzle surrounding the non-consumable electrode, and an outer nozzle surrounding the inner nozzle. A main arc power circuit for supplying a main arc current between the non-consumable electrode and the base material, and a first movement instruction signal while the main arc power circuit is passing the main arc current. An electrode position control circuit to generate, and a pilot arc power supply circuit that starts energization of an intermediate pilot arc current between the non-consumable electrode and the outer nozzle after the first movement instruction signal is generated, and The first movement instruction signal is a signal for moving the non-consumable electrode in a first relative movement with respect to the inner nozzle. From the tip of the Worn electrodes in a first direction toward the base material, the non-consumable electrode with respect to the inner nozzle is to move relative plasma arc welding system is provided.

  Preferably, a main arc current energization detection circuit that generates a main arc current energization detection signal upon detection of energization of the main arc current is further provided, and the electrode position control circuit generates the main arc current energization detection signal. Later, a second movement instruction signal is generated, and the second movement instruction signal is a signal for moving the non-consumable electrode in a second relative movement with respect to the inner nozzle, and the second relative movement is performed in the first relative movement. The non-consumable electrode moves relative to the inner nozzle in a second direction opposite to the direction.

  Preferably, the main arc power supply circuit stops energization of the main arc current after the end of the first relative movement.

  Preferably, the apparatus further includes a position defining mechanism that defines a position of the non-consumable electrode with respect to the inner nozzle, and the position defining mechanism receives the first movement instruction signal from the electrode position control circuit. The non-consumable electrode is moved relative to the first.

  Preferably, the position defining mechanism moves the non-consumable electrode relative to the inner nozzle so that the tip of the non-consumable electrode moves from the second region to the first region in the first relative movement. In the second relative movement, the non-consumable electrode is moved relative to the inner nozzle so that the tip of the non-consumable electrode moves from the first region to the second region, The region is a region located on the second direction side with respect to the opening of the inner nozzle, and the second region is a region located on the first direction side with respect to the opening.

  Preferably, the position defining mechanism always maintains the state where the tip of the non-consumable electrode is positioned in the second region from the end of the first relative movement to the start of the second relative movement.

  Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

It is a block diagram which shows the structure of the plasma arc welding system concerning 1st Embodiment of this invention. It is an expanded sectional view which mainly shows the torch in the plasma arc welding system concerning 1st Embodiment of this invention. It is a block diagram which shows the internal structure of the pilot arc power supply circuit in the plasma arc welding system shown in FIG. It is a timing chart of each signal etc. in the plasma arc welding method using the plasma arc welding system of FIG. 5 is a timing chart of signals and the like in a process subsequent to the process shown in FIG. It is a block diagram which shows the structure of the plasma arc welding system concerning 2nd Embodiment of this invention. It is a block diagram which shows the internal structure of the pilot arc power supply circuit in the plasma arc welding system shown in FIG. It is a timing chart of each signal etc. in the plasma arc welding method using the plasma arc welding system of FIG. FIG. 9 is a timing chart of signals and the like in a step that follows the step shown in FIG.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.

<First Embodiment>
1st Embodiment of this invention is described using FIGS.

  FIG. 1 is a block diagram showing the configuration of the plasma arc welding system according to the first embodiment of the present invention.

  A plasma arc welding system A1 shown in FIG. 1 includes a welding robot 1, an operation control circuit 2, a pilot arc circuit 3, and a main arc circuit 4.

  The welding robot 1 automatically performs plasma arc welding on the base material W. The base material W of this embodiment is a thin plate, and the thickness of the base material W is, for example, 0.1 to 0.5 mm. The welding robot 1 includes a manipulator 11, a torch 12, and a position defining mechanism 14.

  The manipulator 11 is, for example, an articulated robot. The torch 12 can move freely up and down, front and rear, left and right by driving the manipulator 11. As shown in FIGS. 1 and 2, the torch 12 includes a non-consumable electrode 121, an inner nozzle 122, an outer nozzle 123, and a shield gas nozzle 124. The torch 12 of this embodiment has a double structure having an inner nozzle 122 and an outer nozzle 123. The shield gas nozzle 124 is not essential for the torch 12. In the torch having a double structure, the wear of the non-consumable electrode 121 is small, and the life of the non-consumable electrode 121 can be greatly prolonged.

  Non-consumable electrode 121 is a metal rod made of tungsten, for example. This metal bar has, for example, a cylindrical shape with a diameter of about 2.4 to 3.2 mm. As shown in FIG. 2, the direction from the tip 121a of the non-consumable electrode 121 toward the base material W is defined as a first direction X1. On the other hand, the direction opposite to the first direction X1 is defined as a second direction X2. Note that the first direction X1 and the second direction X2 coincide with the extending direction of the metal rod constituting the non-consumable electrode 121.

  The inner nozzle 122 is a cylindrical member. The inner nozzle 122 surrounds the non-consumable electrode 121. The center gas CG flows in the inner nozzle 122. A pilot arc Pa1 is generated between the inner nozzle 122 and the non-consumable electrode 121 using the center gas CG as a medium. When the pilot arc Pa 1 is generated between the inner nozzle 122 and the non-consumable electrode 121, a pilot arc current Ip 1 flows between the inner nozzle 122 and the non-consumable electrode 121. An opening 122 a is formed in the inner nozzle 122. The opening 122a of the inner nozzle 122 is open in the first direction X1. That is, in FIG. 2, the opening 122a of the inner nozzle 122 is opened downward. The opening 122a has a circular shape with a diameter of 2.5 to 4 mm, for example. The shape of the opening 122a is not limited to a circle, and may be another shape such as a rectangle. A region located on the second direction X2 side with respect to the opening 122a of the inner nozzle 122 is defined as a first region 191. On the other hand, a region located on the first direction X1 side with respect to the opening 122a of the inner nozzle 122 is defined as a second region 192.

  The outer nozzle 123 is a cylindrical member. The outer nozzle 123 surrounds the inner nozzle 122. Plasma gas PG flows between the outer nozzle 123 and the inner nozzle 122. A pilot arc Pa2 is generated between the outer nozzle 123 and the non-consumable electrode 121 using the plasma gas PG as a medium. When the pilot arc Pa <b> 2 is generated between the outer nozzle 123 and the non-consumable electrode 121, a pilot arc current Ip <b> 2 flows between the outer nozzle 123 and the non-consumable electrode 121. An opening 123 a is formed in the outer nozzle 123. The opening 123a of the outer nozzle 123 is open in the first direction X1. That is, in FIG. 2, the opening 123a of the outer nozzle 123 is opened downward. The opening 123a has a circular shape with a diameter of 2.5 to 3 mm, for example. The shape of the opening 123a is not limited to a circle, and may be another shape such as a rectangle.

  The shield gas nozzle 124 is a cylindrical member. The shield gas nozzle 124 surrounds the outer nozzle 123. The shield gas SG flows between the shield gas nozzle 124 and the outer nozzle 123. A main arc Ma is generated between the non-consumable electrode 121 and the base material W. When the main arc Ma is generated, the main arc current Im flows between the non-consumable electrode 121 and the base material W. As the main arc current Im, either direct current or alternating current is selected according to the material of the base material W. The main arc current Im may be a direct current pulse current or an alternating current pulse current.

  The position defining mechanism 14 defines the position of the non-consumable electrode 121 with respect to the inner nozzle 122 in the second direction X2. The position defining mechanism 14 can move the non-consumable electrode 121 relative to the inner nozzle 122 such that the tip 121a of the non-consumable electrode 121 moves from the first region 191 to the second region 192. Further, the position defining mechanism 14 can move the non-consumable electrode 121 relative to the inner nozzle 122 so that the tip 121a of the non-consumable electrode 121 moves from the second region 192 to the first region 191. For example, the position defining mechanism 14 may be a solenoid or a motor as a drive source.

  The operation control circuit 2 has a microcomputer and a memory (both not shown). The memory stores a work program in which various operations of the welding robot 1 are set. The operation control circuit 2 controls the robot moving speed Vr. The robot moving speed Vr is the speed of the non-consumable electrode 121 with respect to the base material W in the welding progress direction Dr along the base material W. The operation control circuit 2 sends an operation control signal Ms to the welding robot 1 based on the work program, the coordinate information from the encoder in the welding robot 1, the robot moving speed Vr, and the like. The welding robot 1 receives the operation control signal Ms, drives the manipulator 11, and the torch 12 moves to a predetermined welding start position on the base material W or moves along the in-plane direction of the base material W. The operation control circuit 2 sends a welding start signal St and a welding end signal En. On the other hand, the operation control circuit 2 receives a pilot arc current conduction detection signal Dip.

  The pilot arc circuit 3 includes a pilot arc power supply circuit 31, a pilot arc current detection circuit 33, a pilot arc current energization detection circuit 35, and an electrode position control circuit 38.

  The pilot arc power supply circuit 31 causes a pilot arc current Ip1 to flow between the non-consumable electrode 121 and the inner nozzle 122. Further, the pilot arc power supply circuit 31 causes a pilot arc current Ip2 to flow between the non-consumable electrode 121 and the outer nozzle 123. Pilot arc power supply circuit 31 receives main arc current energization detection signal Dim from main arc current energization detection circuit 45 (described later).

  FIG. 3 is a block diagram showing an internal configuration of pilot arc power supply circuit 31 in plasma arc welding system A1 shown in FIG.

  As shown in FIG. 3A, the pilot arc power supply circuit 31 includes a power generation unit Pw, a high frequency generation unit HF, a pilot arc switch Sw1, a nozzle switch Sw2, and a high frequency switch Sw3.

  The power generation unit Pw performs output control such as inverter control and thyristor phase control with a commercial power supply such as three-phase 200V as an input.

  The high frequency generator HF is for generating a high frequency voltage. The frequency of the voltage generated by the high frequency generator HF is, for example, 1 to 10 MHz. Moreover, the voltage value of the voltage generated by the high frequency generator HF is, for example, 1 to 10 kV, which is very large.

  The power generation unit Pw and the non-consumable electrode 121 are connected via the pilot arc switch Sw1. The pilot arc switch Sw1 switches between a state where the power generation unit Pw and the non-consumable electrode 121 are connected and a state where the power generation unit Pw and the non-consumable electrode 121 are not connected. When the pilot arc switch Sw1 is in the on state, the power generation unit Pw and the non-consumable electrode 121 are connected. On the other hand, when the pilot arc switch Sw1 is in the off state, the power generation unit Pw and the non-consumable electrode 121 are not connected.

  The nozzle switch Sw2 switches between a state where the power generation unit Pw and the inner nozzle 122 are connected and a state where the power generation unit Pw and the outer nozzle 123 are connected. When the nozzle switch Sw <b> 2 is connected to the terminal 311, the power generation unit Pw and the inner nozzle 122 are connected. On the other hand, when the nozzle switch Sw2 is connected to the terminal 312, the power generation unit Pw and the outer nozzle 123 are connected.

  The high frequency switch Sw3 switches between a state in which the high frequency generator HF and the inner nozzle 122 are connected and a state in which the high frequency generator HF and the inner nozzle 122 are not connected. When the high frequency switch Sw3 is connected to the terminal 316, the high frequency generator HF and the inner nozzle 122 are connected. On the other hand, when the high frequency switch Sw3 is connected to the terminal 317, the high frequency generator HF and the inner nozzle 122 are not connected.

  The pilot arc power supply circuit 31 takes the following four modes (mode A, mode B, mode C, and mode H) depending on the switching mode of the pilot arc switch Sw1, the nozzle switch Sw2, and the high frequency switch Sw3.

  FIG. 3A shows a case where the mode of the pilot arc power supply circuit 31 is mode A. When the mode of the pilot arc power supply circuit 31 is mode A, the pilot arc switch Sw <b> 1 is on, the nozzle switch Sw <b> 2 is connected to the terminal 311, and the high frequency switch Sw <b> 3 is connected to the terminal 317. In this case, a pilot arc current Ip1 flows between the non-consumable electrode 121 and the inner nozzle 122.

  FIG. 3B shows a case where the mode of the pilot arc power supply circuit 31 is mode B. When the mode of the pilot arc power supply circuit 31 is mode B, the pilot arc switch Sw <b> 1 is on and the nozzle switch Sw <b> 2 is connected to the terminal 312. In this case, a pilot arc current Ip2 flows between the non-consumable electrode 121 and the outer nozzle 123.

  FIG. 3C shows a case where the mode of the pilot arc power supply circuit 31 is mode C. When the mode of the pilot arc power supply circuit 31 is mode C, the pilot arc switch Sw1 is in an off state, and between the non-consumable electrode 121 and the inner nozzle 122 and between the non-consumable electrode 121 and the outer nozzle 123. In either case, no current flows.

  FIG. 3D shows a case where the mode of the pilot arc power supply circuit 31 is mode H. When the mode of the pilot arc power supply circuit 31 is mode H, the pilot arc switch Sw1 is on, the nozzle switch Sw2 is connected to the terminal 311 and the high frequency switch Sw3 is connected to the terminal 316. In this case, a pilot arc current Ip1 flows between the non-consumable electrode 121 and the inner nozzle 122. Further, a high frequency voltage is applied between the non-consumable electrode 121 and the inner nozzle 122 by the high frequency generator HF.

  The pilot arc current detection circuit 33 shown in FIG. 1 is for detecting the current value of the pilot arc current Ip2 flowing between the non-consumable electrode 121 and the outer nozzle 123. The pilot arc current detection circuit 33 sends a pilot arc current detection signal Idp corresponding to the current value of the pilot arc current Ip2.

  The pilot arc current energization detection circuit 35 is for detecting the start of energization of the pilot arc current Ip2. The pilot arc current energization detection circuit 35 sends a pilot arc current energization detection signal Dip when detecting energization of the pilot arc current Ip2. Pilot arc current energization detection circuit 35 detects the start of energization of pilot arc current Ip2, for example, by comparing the current value of pilot arc current Ip2 with a certain threshold value.

  The electrode position control circuit 38 is for controlling the position of the non-consumable electrode 121 with respect to the inner nozzle 122 in the second direction X2. The electrode position control circuit 38 receives the welding end signal En from the operation control circuit 2 and the main arc current energization detection signal Dim from the main arc current energization detection circuit 45. The electrode position control circuit 38 generates a position defining signal Sp. Then, the electrode position control circuit 38 sends the generated position defining signal Sp to the position defining mechanism 14. The position defining signal Sp corresponds to the position of the non-consumable electrode 121 with respect to the inner nozzle 122 in the second direction X2. In the present embodiment, when the position defining signal Sp is at the high level, the tip 121a of the non-consumable electrode 121 is located in the first region 191. On the other hand, when the position defining signal Sp is at the Low level, the tip 121a of the non-consumable electrode 121 is located in the second region 192.

  The main arc circuit 4 includes a main arc power supply circuit 41, a main arc current detection circuit 43, and a main arc current conduction detection circuit 45.

  The main arc power supply circuit 41 performs output control such as inverter control and thyristor phase control using a commercial power supply such as a three-phase 200 V input as an input. As a result, the main arc power supply circuit 41 causes the main arc current Im to flow between the non-consumable electrode 121 and the base material W. The main arc power supply circuit 41 controls the current value of the main arc current Im to be a set value.

  Main arc power supply circuit 41 receives welding start signal St from operation control circuit 2 and pilot arc current energization detection signal Dip from pilot arc current energization detection circuit 35. When receiving the welding start signal St, the main arc power supply circuit 41 starts energizing the main arc current Im. On the other hand, when main arc power supply circuit 41 receives pilot arc current energization detection signal Dip, it stops energization of main arc current Im.

  The main arc current detection circuit 43 is for detecting the current value of the main arc current Im flowing between the non-consumable electrode 121 and the base material W. The main arc current detection circuit 43 sends a main arc current detection signal Idm corresponding to the current value of the main arc current Im.

  Main arc current conduction detection circuit 45 receives main arc current detection signal Idm. The main arc current energization detection circuit 45 is for detecting the start of energization of the main arc current Im. When the main arc current energization detection circuit 45 detects the start of energization of the main arc current Im, it sends a main arc current energization detection signal Dim to the pilot arc power supply circuit 31 and the electrode position control circuit 38. The main arc current energization detection circuit 45 detects the start of energization of the main arc current Im, for example, by comparing the current value of the main arc current Im with a certain threshold value.

  Next, the arc welding method using plasma arc welding system A1 is demonstrated further using FIG. 4, FIG.

  FIG. 4 is a timing chart of signals and the like in the plasma arc welding method using the plasma arc welding system A1 of FIG. In this figure, (a) is the current value of the pilot arc current Ip1, (b) is the current value of the pilot arc current Ip2, (c) is the welding start signal St, (d) is the main arc current Im, and (e) is The position defining signal Sp, (f) is the main arc current conduction detection signal Dim, (g) is the welding end signal En, (h) is the pilot arc current conduction detection signal Dip, (i) is the robot movement speed Vr, (j). Indicates the respective change states of whether or not a high-frequency voltage is applied. The mode of the pilot arc power supply circuit 31 is described at the bottom of the figure.

  Note that during time t1 to time t9 (strictly, from time t5 to time t9), welding is performed on the first base material W1 as the base material W by the plasma arc welding system A1.

<Period during which pilot arc power supply circuit 31 is in mode H (time t1 to time t3)>
At time t1, a pilot arc current energization start signal (not shown) is sent to the pilot arc power circuit 31 so that the mode of the pilot arc power circuit 31 becomes mode H. As shown in FIG. 4 (j), when the mode of the pilot arc power supply circuit 31 becomes mode H, the pilot arc power supply circuit 31 applies a high-frequency voltage between the non-consumable electrode 121 and the inner nozzle 122. Thereby, the pilot arc Pa1 is generated between the non-consumable electrode 121 and the inner nozzle 122 at time t2. When pilot arc Pa1 occurs, energization of pilot arc current Ip1 starts as shown in FIG. That is, energization of the initial pilot arc current ip1 starts between the non-consumable electrode 121 and the inner nozzle 122 as the pilot arc current Ip1. The current value of initial pilot arc current ip1 is, for example, 3 to 20A.

  As shown in FIG. 4E, the electrode position control circuit 38 sends a high level position defining signal Sp to the position defining mechanism 14 from time t1. That is, from time t1, the electrode position control circuit 38 sends a position defining signal Sp for positioning the tip 121a of the non-consumable electrode 121 in the first region 191 to the position defining mechanism 14. Therefore, the tip 121a of the non-consumable electrode 121 is located in the first region 191 from time t1. The length of time t1 to time t3 is, for example, 1 to 3 seconds.

<Period during which pilot arc power supply circuit 31 is in mode A (time t3 to time t4)>
At time t3, the mode of the pilot arc power supply circuit 31 becomes mode A. As shown in FIG. 4 (j), when the mode of the pilot arc power supply circuit 31 becomes mode A, the pilot arc power supply circuit 31 stops applying the high-frequency voltage. As shown in FIG. 5A, after time t3, the pilot arc power supply circuit 31 continues energization of the initial pilot arc current ip1. The length of time t2 to time t4 is, for example, 4 to 5 seconds.

<Period during which pilot arc power supply circuit 31 is in mode B (time t4 to time t6)>
At time t4, the mode of pilot arc power supply circuit 31 becomes mode B. When the mode of the pilot arc power supply circuit 31 is set to mode B, the pilot arc Pa1 generated between the non-consumable electrode 121 and the inner nozzle 122 becomes a pilot arc Pa2 between the non-consumable electrode 121 and the outer nozzle 123. And migrate. Thereby, as shown to Fig.4 (a), electricity supply of the pilot arc current Ip1 between the non-consumable electrode 121 and the inner side nozzle 122 stops. Then, as shown in FIG. 5B, energization of the pilot arc current Ip2 starts between the non-consumable electrode 121 and the outer nozzle 123. That is, at time t4, energization of start pilot arc current ip21 starts between non-consumable electrode 121 and outer nozzle 123 as pilot arc current Ip2. The current value of start pilot arc current ip21 is, for example, 3 to 20A.

  As shown in FIG. 4C, a welding start signal St is sent from the operation control circuit 2 to the main arc power supply circuit 41 at time t5. When receiving the welding start signal St, the main arc power supply circuit 41 applies a voltage between the non-consumable electrode 121 and the first base material W1. In the space near the tip 121a of the non-consumable electrode 121, a plasma atmosphere is formed by the pilot arc Pa2. Therefore, the main arc Ma is induced between the non-consumable electrode 121 and the first base material W1 by being induced by the pilot arc Pa2. As a result, as shown in FIG. 6D, energization of the main arc current Im starts at time t5. Hereinafter, the main arc current Im flowing between the non-consumable electrode 121 and the first base material W1 is referred to as a first main arc current im1. The current value of the first main arc current im1 is, for example, 5 to 7A.

  As shown in FIG. 4F, at time t5, the main arc current energization detection circuit 45 detects the start of energization of the first main arc current im1, and the main arc current energization detection signal Dim is sent to the pilot arc power supply circuit 31. Send to. Thereby, the pilot arc power supply circuit 31 recognizes that energization of the first main arc current im1 has started.

  As shown in FIG. 4 (i), at time t5, the operation control circuit 2 sends an operation control signal Ms for setting the robot moving speed Vr to a predetermined speed to the welding robot 1. Thereby, at time t5, the movement of the non-consumable electrode 121 with respect to the first base material W1 in the welding progress direction Dr starts. Thus, from time t5, the plasma arc welding system A1 performs steady welding while energizing the first main arc current im1 between the non-consumable electrode 121 and the first base material W1. The movement of the non-consumable electrode 121 relative to the first base material W1 in the welding progress direction Dr does not have to be simultaneously with the start of energization of the first main arc current im1. For example, even when the first main arc current im1 is energized (after time t5) or before energization (before time t5), the movement of the non-consumable electrode 121 relative to the first base material W1 in the welding progress direction Dr is started. Good. The length of time t4 to time t6 is, for example, 1 to 2 seconds.

<Period during which pilot arc power supply circuit 31 is in mode C (time t6 to time t8)>
When pilot arc power supply circuit 31 receives main arc current energization detection signal Dim at time t5, the mode of pilot arc power supply circuit 31 becomes mode C at time t6. When the mode of the pilot arc power supply circuit 31 becomes mode C, the pilot arc power supply circuit 31 stops energization of the start pilot arc current ip21 as shown in FIG. Thereby, the pilot arc Pa2 between the non-consumable electrode 121 and the outer nozzle 123 is extinguished. After time t6, the plasma arc welding system A1 performs steady welding of the first base material W1. The length of time t6 to time t7 is, for example, several minutes to several hours.

  As shown in FIG. 4 (e), after the time (time t6) when the pilot arc Pa2 between the non-consumable electrode 121 and the outer nozzle 123 is extinguished, the electrode position control circuit 38 has the tip 121a of the non-consumable electrode 121. Is sent to the position defining mechanism 14 for positioning the signal in the first area 191. Therefore, after time t6, the tip 121a of the non-consumable electrode 121 is located in the first region 191.

  As shown in FIG. 4G, the operation control circuit 2 sends a welding end signal En for ending the steady welding to the electrode position control circuit 38 at time t7. As shown in FIG. 4E, when the electrode position control circuit 38 receives the welding end signal En, the electrode position control circuit 38 generates a first movement instruction signal sp1 and sends the generated first movement instruction signal sp1 to the position defining mechanism 14. send. In the present embodiment, the electrode position control circuit 38 changes the position defining signal Sp from High level to Low level. The position defining signal Sp changing from the High level to the Low level corresponds to the first movement instruction signal sp1. The first movement instruction signal sp1 is a signal for causing the inner nozzle 122 to move the non-consumable electrode 121 in a first relative movement (described later).

  2 receives the first movement instruction signal sp1 and moves the non-consumable electrode 121 relative to the inner nozzle 122 in the first relative direction. The first relative movement of the non-consumable electrode 121 with respect to the inner nozzle 122 is that the non-consumable electrode 121 moves relative to the inner nozzle 122 in the first direction X1. In the first relative movement, the position defining mechanism 14 moves the non-consumable electrode 121 relative to the inner nozzle 122 so that the tip 121a of the non-consumable electrode 121 moves from the first region 191 to the second region 192. . In the present embodiment, in the first relative movement, the non-consumable electrode 121 moves relative to the inner nozzle 122 while the inner nozzle 122 and the outer nozzle 123 are fixed to each other. Further, in the present embodiment, in the first relative movement, the non-consumable electrode 121 is brought closer to the first base material W1. It is preferable that the tip 121a of the non-consumable electrode 121 moves to the vicinity of the opening 123a of the outer nozzle 123 by the first relative movement. As described above, the process of moving the non-consumable electrode 121 relative to the inner nozzle 122 in the first direction X1 during the process of performing steady welding while energizing the first main arc current im1 (first movement process). )I do. As shown in FIG. 4E, the relative movement (first relative movement) of the non-consumable electrode 121 with respect to the inner nozzle 122 ends at time t8.

  FIG. 5 is a timing chart of signals and the like in a process following the process shown in FIG.

<Period during which pilot arc power supply circuit 31 is in mode B (time t8 to t11)>
As shown in FIGS. 4 and 5, the mode of pilot arc power supply circuit 31 becomes mode B at time t8. When the mode of the pilot arc power supply circuit 31 becomes mode B, a voltage (not a high-frequency voltage) is applied between the non-consumable electrode 121 and the outer nozzle 123. The value of the voltage applied at this time is, for example, 70 to 80V. In the vicinity of the tip 121a of the non-consumable electrode 121, a plasma atmosphere is formed by the main arc Ma. Therefore, the pilot arc Pa <b> 2 is generated between the non-consumable electrode 121 and the outer nozzle 123 by being induced by the main arc Ma. Thereby, energization of pilot arc current Ip2 starts between non-consumable electrode 121 and outer nozzle 123 at time t8. That is, at time t8, energization of the intermediate pilot arc current ip22 is started between the non-consumable electrode 121 and the outer nozzle 123 as the pilot arc current Ip2. In this way, the pilot arc power supply circuit 31 starts energization of the intermediate pilot arc current ip22 between the non-consumable electrode 121 and the outer nozzle 123 after starting the first movement step described above.

  Starting the energization of the intermediate pilot arc current ip22 between the non-consumable electrode 121 and the outer nozzle 123 is not limited to the time t8. For example, the intermediate pilot arc current ip22 may start to flow during the above-described first movement process (time t7 to time t8). Alternatively, the intermediate pilot arc current ip22 may start to flow after a certain period from time t8.

  As shown in FIGS. 4 (h) and 5 (h), at time t8, the pilot arc current energization detection circuit 35 detects the start of energization of the intermediate pilot arc current ip22, and generates a pilot arc current energization detection signal Dip. To the operation control circuit 2 and the main arc power supply circuit 41. Thereby, the operation control circuit 2 and the main arc power supply circuit 41 recognize that the energization of the intermediate pilot arc current ip22 has started.

  When main arc power supply circuit 41 receives pilot arc current energization detection signal Dip at time t8, main arc power supply circuit 41 energizes first main arc current im1 flowing between non-consumable electrode 121 and first base material W1 at time t9. Stop. Thereby, the main arc Ma between the non-consumable electrode 121 and the first base material W1 is extinguished. Note that the energization of the first main arc current im1 is stopped after the end of the first movement process.

  When the operation control circuit 2 receives the pilot arc current energization detection signal Dip at time t9, the operation control circuit 2 sends an operation control signal Ms for setting the robot moving speed Vr to 0 to the welding robot 1. Thereby, at time t8, the movement of the non-consumable electrode 121 with respect to the first base material W1 in the welding progress direction Dr is stopped. Note that the movement of the non-consumable electrode 121 with respect to the first base material W1 does not have to be the same as the timing at which the energization of the first main arc current im1 is stopped. For example, the movement of the non-consumable electrode 121 to the first base material W1 may be stopped at the time (time t7) at which the first movement process described above is started. Alternatively, the movement of the non-consumable electrode 121 to the first base material W1 may be stopped after the time when the energization of the first main arc current im1 is stopped (time t9).

  At time t9, the welding of the first base material W1 by the plasma arc welding system A1 is finished. From time t10, welding to the second base material W2 as the base material W is performed by the plasma arc welding system A1. The period from time t9 to time t10 is a standby period for performing welding to the second base material W2. The length of time t9 to time t10 is, for example, several minutes to several tens of minutes.

  As shown in FIG. 5C, a welding start signal St is sent from the operation control circuit 2 to the main arc power supply circuit 41 at time t10. When the main arc power supply circuit 41 receives the welding start signal St, the main arc power supply circuit 41 applies a voltage between the non-consumable electrode 121 and the second base material W2. In the space near the tip 121a of the non-consumable electrode 121, a plasma atmosphere is formed by the pilot arc Pa2. Therefore, the main arc Ma is induced between the non-consumable electrode 121 and the second base material W2 by being induced by the pilot arc Pa2. As a result, as shown in FIG. 6D, energization of the main arc current Im starts at time t10. The current value of the main arc current Im is, for example, 5 to 7A. Hereinafter, the main arc current Im flowing between the non-consumable electrode 121 and the second base material W2 is referred to as a second main arc current im2. The current value of the second main arc current im2 is, for example, 5-7A.

  As shown in FIG. 5 (f), at time t10, the main arc current energization detection circuit 45 detects the start of energization of the second main arc current im2, and the main arc current energization detection signal Dim is sent to the pilot arc power supply circuit 31. Send to. As a result, the pilot arc power supply circuit 31 recognizes that energization of the second main arc current im2 has started.

  As shown in FIG. 5 (i), at time t 10, the operation control circuit 2 sends an operation control signal Ms for setting the robot moving speed Vr to a predetermined speed to the welding robot 1. Thereby, at time t10, the movement of the non-consumable electrode 121 with respect to the second base material W2 in the welding progress direction Dr starts. Thus, from time t10, the plasma arc welding system A1 performs steady welding while energizing the second main arc current im2 between the non-consumable electrode 121 and the second base material W2. The movement of the non-consumable electrode 121 relative to the second base material W2 in the welding progress direction Dr does not have to be simultaneously with the start of energization of the second main arc current im2. For example, the movement of the non-consumable electrode 121 relative to the second base material W2 in the welding progress direction Dr may be started after energization of the second main arc current im2 (after time t10).

  As shown in FIG. 5E, the position defining signal Sp always remains at the low level between time t8 and time t11. Therefore, between time t8 and time t11, the position defining mechanism 14 does not move the non-consumable electrode 121 relative to the inner nozzle 122 in the second direction X2. In this manner, the position defining mechanism 14 continues the state where the tip 121a of the non-consumable electrode 121 is positioned in the second region 192 between time t8 and time t11. In order for the position defining mechanism 14 to continue the state in which the tip 121a of the non-consumable electrode 121 is positioned in the second region 192, it is not always necessary to fix the non-consumable electrode 121 at a certain position. For example, when a motor is used as the drive source of the position defining mechanism 14, the non-consumable electrode 121 may be moved relative to the inner nozzle 122 within a range where the tip 121 a of the non-consumable electrode 121 is located in the second region 192. Good.

  Unlike the present embodiment, the non-consumable electrode 121 may be moved with respect to the inner nozzle 122 so that the tip 121a of the non-consumable electrode 121 is positioned in the first region 191 between time t8 and time t11. .

<Period during which pilot arc power supply circuit 31 is in mode C (time t11 to t14)>
When pilot arc power supply circuit 31 receives main arc current energization detection signal Dim at time t10, the mode of pilot arc power supply circuit 31 becomes mode C at time t11. When the mode of the pilot arc power supply circuit 31 becomes mode C, the pilot arc power supply circuit 31 stops energization of the intermediate pilot arc current ip22 as shown in FIG. Thereby, the pilot arc Pa2 between the non-consumable electrode 121 and the outer nozzle 123 is extinguished.

  At time t11, upon receiving the main arc current energization detection signal Dim, the electrode position control circuit 38 generates a second movement instruction signal sp2. The electrode position control circuit 38 sends the generated second movement instruction signal sp2 to the position defining mechanism 14. In the present embodiment, the electrode position control circuit 38 changes the position defining signal Sp from Low level to High level. The position defining signal Sp changing from the Low level to the High level corresponds to the second movement instruction signal sp2. The second movement instruction signal sp2 is a signal for causing the inner nozzle 122 to move the non-consumable electrode 121 in a second relative movement (described later).

  When the position defining mechanism 14 shown in FIG. 2 receives the second movement instruction signal sp2, the non-consumable electrode 121 is moved relative to the inner nozzle 122 by the second relative movement. The second relative movement of the non-consumable electrode 121 with respect to the inner nozzle 122 is a relative movement of the non-consumable electrode 121 with respect to the inner nozzle 122 in the second direction X2. In the second relative movement, the position defining mechanism 14 moves the non-consumable electrode 121 relative to the inner nozzle 122 so that the tip 121a of the non-consumable electrode 121 moves from the second region 192 to the first region 191. . In the present embodiment, in the second relative movement, the non-consumable electrode 121 moves relative to the inner nozzle 122 while the inner nozzle 122 and the outer nozzle 123 are fixed to each other. Further, in the present embodiment, in the second relative movement, the non-consumable electrode 121 is separated from the second base material W2. As described above, after the energization of the second main arc current im2 is started, the step of moving the non-consumable electrode 121 relative to the inner nozzle 122 in the second direction X2 (second movement step) is performed. As shown in FIG. 5E, the relative movement (second relative movement) of the non-consumable electrode 121 with respect to the inner nozzle 122 ends at time t12.

  After time t12, the same process as the process from time t6 to time t12 is performed one or more times.

  Next, the effect of this embodiment is demonstrated.

  In the present embodiment, during the step of applying the first main arc current im1, the non-consumable electrode 121 with respect to the inner nozzle 122 in the first direction X1 from the tip 121a of the non-consumable electrode 121 toward the first base material W1. The 1st movement process which moves relative is performed. After starting the first movement process (after time t7), energization of the intermediate pilot arc current ip22 is started between the non-consumable electrode 121 and the outer nozzle 123 (see FIG. 5B). According to such a configuration, while the first main arc current im1 is energized (while the main arc Ma is generated), the region between the non-consumable electrode 121 and the inner nozzle 122 is likely to break down. The inner nozzle 122 can begin to retract. As a result, it is possible to more reliably cause dielectric breakdown between the non-consumable electrode 121 and the outer nozzle 123 while avoiding application of a high-frequency voltage. As a result, energization of intermediate pilot arc current ip22 can be started more reliably. That is, it is possible to generate the pilot arc Pa2 between the non-consumable electrode 121 and the outer nozzle 123 more reliably while avoiding the application of the high frequency voltage. Therefore, even when the torch 12 having a double structure is used, application of a high frequency voltage can be avoided as much as possible.

  In the present embodiment, a second movement process is performed in which the non-consumable electrode 121 is moved relative to the inner nozzle 122 in the second direction X2 opposite to the first direction X1. The second movement process is performed after the process of starting energization of the second main arc current im2. According to such a configuration, energization of the second main arc current im2 can be started when the tip 121a of the non-consumable electrode 121 is located further in the first direction X1. Then, energization of the second main arc current im2 can be started when the inner nozzle 122 is retracted as much as possible from the region where the dielectric breakdown between the non-consumable electrode 121 and the inner nozzle 122 tends to break down. Thereby, it is possible to prevent the pilot arc Pa2 from being extinguished before the energization of the second main arc current im2 is started (that is, before the main arc Ma is generated).

  In the present embodiment, the tip 121a of the non-consumable electrode 121 is always positioned in the second region 192 from the end of the first movement process (time t8) to the start of the second movement process (time t11). To continue. According to such a configuration, it is possible to prevent the pilot arc Pa2 from extinguishing between the end of the first movement process (time t8) and the start of the second movement process (time t11).

  Usually, the non-consumable electrode 121 is lightweight and easy to move. In the present embodiment, in the first movement process, the tip 121a of the non-consumable electrode 121 is brought close to the first base material W1. Such a configuration is easy to realize.

Second Embodiment
A second embodiment of the present invention will be described with reference to FIGS.

  In the following description, the same or similar components as those described above will be denoted by the same reference numerals as those described above, and description thereof will be omitted as appropriate.

  FIG. 6 is a block diagram showing a configuration of a plasma arc welding system according to the second embodiment of the present invention.

  A plasma arc welding system A2 shown in FIG. 1 includes a welding robot 1, an operation control circuit 2, a pilot arc circuit 3, and a main arc circuit 4.

  Since the welding robot 1, the operation control circuit 2, and the main arc circuit 4 are the same as those in the plasma arc welding system A1, description thereof will be omitted.

  The pilot arc circuit 3 includes a pilot arc power supply circuit 31, a pilot arc current detection circuit 33, a pilot arc current energization detection circuit 35, and an electrode position control circuit 38.

  The pilot arc circuit 3 has the same configuration as that of the plasma arc welding system A1 except for the pilot arc power supply circuit 31. Therefore, descriptions of the pilot arc current detection circuit 33, the pilot arc current energization detection circuit 35, and the electrode position control circuit 38 are omitted.

  The pilot arc power supply circuit 31 is different from that in the plasma arc welding system A1 in that a current is not supplied to the inner nozzle 122 but a current is supplied only to the outer nozzle 123. This will be specifically described below.

  The pilot arc power supply circuit 31 passes a pilot arc current Ip2 between the non-consumable electrode 121 and the outer nozzle 123. Pilot arc power supply circuit 31 receives main arc current energization detection signal Dim from main arc current energization detection circuit 45.

  FIG. 7 is a block diagram showing an internal configuration of pilot arc power supply circuit 31 in plasma arc welding system A2 shown in FIG.

  As shown to Fig.7 (a), the pilot arc power supply circuit 31 has the electric power generation part Pw, the high frequency generation part HF, the pilot arc switch Sw1, and the high frequency switch Sw4.

  The power generation unit Pw, the high frequency generation unit HF, and the pilot arc switch Sw1 are the same as those in the plasma arc welding system A1, and thus description thereof is omitted.

  The high frequency switch Sw4 switches between a state where the high frequency generator HF and the outer nozzle 123 are connected and a state where the high frequency generator HF and the outer nozzle 123 are not connected. When the high frequency switch Sw4 is connected to the terminal 316, the high frequency generator HF and the outer nozzle 123 are connected. On the other hand, when the high frequency switch Sw4 is connected to the terminal 317, the high frequency generator HF and the outer nozzle 123 are not connected.

  The pilot arc power supply circuit 31 takes the following three modes (mode B, mode C, and mode H) depending on the switching mode between the pilot arc switch Sw1 and the high-frequency switch Sw4.

  FIG. 7A shows a case where the mode of the pilot arc power supply circuit 31 is mode B. When the mode of the pilot arc power supply circuit 31 is mode B, the pilot arc switch Sw <b> 1 is on and the high frequency switch Sw <b> 4 is connected to the terminal 317. In this case, a pilot arc current Ip2 flows between the non-consumable electrode 121 and the outer nozzle 123.

  FIG. 7B shows a case where the mode of the pilot arc power supply circuit 31 is mode C. When the mode of the pilot arc power supply circuit 31 is mode C, the pilot arc switch Sw1 is in an off state, and between the non-consumable electrode 121 and the inner nozzle 122 and between the non-consumable electrode 121 and the outer nozzle 123. In either case, no current flows.

  FIG. 7C shows a case where the mode of the pilot arc power supply circuit 31 is mode H. When the mode of the pilot arc power supply circuit 31 is mode H, the pilot arc switch Sw <b> 1 is on and the high frequency switch Sw <b> 4 is connected to the terminal 316. In this case, a pilot arc current Ip2 flows between the non-consumable electrode 121 and the outer nozzle 123. In addition, a high frequency voltage is applied between the non-consumable electrode 121 and the outer nozzle 123.

  Next, the arc welding method using plasma arc welding system A2 is demonstrated further using FIG. 8, FIG.

  FIG. 8 is a timing chart of signals and the like in the plasma arc welding method using the plasma arc welding system A2. FIG. 9 is a timing chart of each signal and the like in a process following the process shown in FIG.

  FIGS. 8A to 8J show the same signals and the like as FIGS. 4A to 4J, and FIGS. 9A to 9J show the same signals and the like as FIGS. 5A to 5J, respectively.

  The arc welding method of the present embodiment is different from the arc welding method of the first embodiment in steps from time t21 to time t26. The process after time t26 of the present embodiment is the same as the process after time t6 of the first embodiment. This will be described below.

<Period during which pilot arc power supply circuit 31 is in mode H (time t21 to time t23)>
At time t21, a pilot arc current energization start signal (not shown) is sent to the pilot arc power supply circuit 31, so that the mode of the pilot arc power supply circuit 31 becomes mode H. As shown in FIG. 8 (j), when the mode of the pilot arc power supply circuit 31 becomes mode H, the pilot arc power supply circuit 31 applies a high-frequency voltage between the non-consumable electrode 121 and the outer nozzle 123. As a result, a pilot arc Pa2 is generated between the non-consumable electrode 121 and the outer nozzle 123 at time t22. When the pilot arc Pa2 is generated, energization of the pilot arc current Ip2 starts as shown in FIG. That is, energization of the start pilot arc current ip21 is started between the non-consumable electrode 121 and the outer nozzle 123 as the pilot arc current Ip2. The current value of start pilot arc current ip21 is, for example, 3 to 20A.

  In the present embodiment, as shown in FIG. 8 (e), the electrode position control circuit 38 sends a Low level position defining signal Sp to the position defining mechanism 14 from time t 21. That is, from time t21, the electrode position control circuit 38 sends a position defining signal Sp for positioning the tip 121a of the non-consumable electrode 121 in the second region 192 to the position defining mechanism 14. Therefore, the tip 121a of the non-consumable electrode 121 is located in the second region 192 from time t21.

<Period during which pilot arc power supply circuit 31 is in mode B (time t23 to time t25)>
At time t23, the mode of the pilot arc power supply circuit 31 becomes mode B. As shown in FIG. 8 (j), when the mode of the pilot arc power supply circuit 31 becomes mode B, the pilot arc power supply circuit 31 stops applying the high-frequency voltage. As shown in FIG. 5B, after time t23, the pilot arc power supply circuit 31 continues energization of the start pilot arc current ip21.

  As shown in FIG. 8C, a welding start signal St is sent from the operation control circuit 2 to the main arc power supply circuit 41 at time t24. When receiving the welding start signal St, the main arc power supply circuit 41 applies a voltage between the non-consumable electrode 121 and the first base material W1. In the space near the tip 121a of the non-consumable electrode 121, a plasma atmosphere is formed by the pilot arc Pa2. Therefore, the main arc Ma is induced between the non-consumable electrode 121 and the first base material W1 by being induced by the pilot arc Pa2. As a result, as shown in FIG. 4D, energization of the main arc current Im starts at time t24. The main arc current Im flowing between the non-consumable electrode 121 and the first base material W1 is referred to as a first main arc current im1. The current value of the first main arc current im1 is, for example, 5 to 7A.

  As shown in FIG. 8F, at time t24, the main arc current energization detection circuit 45 detects the start of energization of the first main arc current im1, and the main arc current energization detection signal Dim is sent to the pilot arc power supply circuit 31. Send to. Thereby, the pilot arc power supply circuit 31 recognizes that energization of the first main arc current im1 has started.

  As shown in FIG. 8 (i), at time t 24, the operation control circuit 2 sends an operation control signal Ms for setting the robot moving speed Vr to a predetermined speed to the welding robot 1. Thereby, the movement of the non-consumable electrode 121 with respect to the first base material W1 in the welding progress direction Dr starts at time t24. Thus, from time t24, the plasma arc welding system A2 performs steady welding while energizing the first main arc current im1 between the non-consumable electrode 121 and the first base material W1. The movement of the non-consumable electrode 121 relative to the first base material W1 in the welding progress direction Dr does not have to be simultaneously with the start of energization of the first main arc current im1. For example, after energization of the first main arc current im1 (after time t24), the movement of the non-consumable electrode 121 relative to the first base material W1 in the welding progress direction Dr may be started.

<Period during which pilot arc power supply circuit 31 is in mode C (after time t25)>
When pilot arc power supply circuit 31 receives main arc current energization detection signal Dim at time t24, the mode of pilot arc power supply circuit 31 becomes mode C at time t25. When the mode of the pilot arc power supply circuit 31 becomes mode C, the energization of the start pilot arc current ip21 flowing between the non-consumable electrode 121 and the outer nozzle 123 is stopped as shown in FIG. Thereby, the pilot arc Pa2 between the non-consumable electrode 121 and the outer nozzle 123 is extinguished.

  In the present embodiment, as shown in FIG. 8E, when receiving the main arc current energization detection signal Dim at time t24, the electrode position control circuit 38 generates an initial movement instruction signal sp3 at time t25. The electrode position control circuit 38 sends the generated initial movement instruction signal sp3 to the position defining mechanism 14. In the present embodiment, the electrode position control circuit 38 changes the position defining signal Sp from Low level to High level. The position defining signal Sp changing from the Low level to the High level corresponds to the initial movement instruction signal sp3. The initial movement instruction signal sp3 is a signal for initial relative movement (described later) of the non-consumable electrode 121 with respect to the inner nozzle 122.

  When receiving the initial movement instruction signal sp3, the position defining mechanism 14 moves the non-consumable electrode 121 to the inner nozzle 122 in an initial relative movement. The initial relative movement of the non-consumable electrode 121 with respect to the inner nozzle 122 is that the non-consumable electrode 121 moves relative to the inner nozzle 122 in the second direction X2. In the initial relative movement, the position defining mechanism 14 moves the non-consumable electrode 121 relative to the inner nozzle 122 so that the tip 121a of the non-consumable electrode 121 moves from the second region 192 to the first region 191. Since the initial relative movement is the same as the second relative movement described in the first embodiment, description thereof is omitted. As shown in FIG. 8E, the relative movement of the non-consumable electrode 121 with respect to the inner nozzle 122 ends at time t26.

  As shown in FIGS. 8 and 9, after time t26, the same process as the process after time t6 of the first embodiment is performed, and thus the description thereof is omitted.

  Next, the effect of this embodiment is demonstrated.

  According to this embodiment, in addition to the same effect as 1st Embodiment, there exist the following effects.

  In the present embodiment, an initial movement process is performed in which the non-consumable electrode 121 is moved relative to the inner nozzle 122 in the second direction X2 opposite to the first direction X1. The process of flowing the start pilot arc current ip 21 is started by applying a high frequency voltage between the non-consumable electrode 121 and the outer nozzle 123. The initial movement process is performed after the process of starting energization of the first main arc current im1. According to such a configuration, the pilot arc Pa2 can be generated between the non-consumable electrode 121 and the outer nozzle 123 without generating the pilot arc Pa1 between the non-consumable electrode 121 and the inner nozzle 122. . Therefore, energization of the start pilot arc current ip21 can be started earlier between the non-consumable electrode 121 and the outer nozzle 123.

  The present invention is not limited to the embodiment described above. The specific configuration of each part of the present invention can be changed in various ways.

  In the above description, the example in which the non-consumable electrode 121 is moved relative to the base material W (the first base material W1 to the second base material W2) in the first relative movement, the second relative movement, and the initial relative movement is shown. However, the present invention is not limited to this. For example, in the first relative movement, the second relative movement, and the initial relative movement, the distance between the non-consumable electrode 121 and the base material W (the first base material W1 to the second base material W2) is kept constant, and the inner nozzle The non-consumable electrode 121 may be moved relative to 122.

  In the above description, an example in which the non-consumable electrode 121 is moved while the inner nozzle 122 and the outer nozzle 123 are fixed to each other in the first relative movement, the second relative movement, and the initial relative movement has been described. Is not limited to this. For example, the non-consumable electrode 121 may be moved relative to the inner nozzle 122 while the non-consumable electrode 121 and the outer nozzle 123 are fixed to each other.

1 welding robot 11 manipulator 12 torch 121 non-consumable electrode 121a tip 122 inner nozzle 122a opening 123 outer nozzle 123a opening 124 shield gas nozzle 14 position defining mechanism 191 first region 192 second region 2 operation control circuit 3 pilot arc circuit 31 pilot arc Power supply circuit 311, 312, 316, 317 Terminal 33 Pilot arc current detection circuit 35 Pilot arc current conduction detection circuit 38 Electrode position control circuit 4 Main arc circuit 41 Main arc power supply circuit 43 Main arc current detection circuit 45 Main arc current conduction detection Circuit A Mode A1 Plasma arc welding system A2 Plasma arc welding system B Mode C Mode CG Center gas Dim Main arc current conduction detection signal Dip Pilot arc electricity Energization detection signal Dr Welding direction En Welding end signal H Mode HF High frequency generator Idm Main arc current detection signal Idp Pilot arc current detection signal Im Main arc current im1 First main arc current im2 Second main arc current Ip1 Pilot arc current ip1 Initial pilot arc current Ip2 Pilot arc current ip21 Start pilot arc current ip22 Intermediate pilot arc current Ma Main arc Ms Operation control signal Pa1 Pilot arc Pa2 Pilot arc PG Plasma gas Pw Electric power generation part SG Shielding gas Sp Position regulation signal sp1 First movement instruction Signal sp2 Second movement instruction signal sp3 Initial movement instruction signal St Welding start signal Sw1 Pilot arc switch Sw2 Nozzle switches Sw3 and Sw4 Pitch Vr robot moving speed W matrix W1 first base material W2 second preform X1 first direction X2 second direction

Claims (15)

Using a torch comprising a non-consumable electrode, an inner nozzle surrounding the non-consumable electrode, and an outer nozzle surrounding the inner nozzle,
Passing a first main arc current between the non-consumable electrode and the first base material;
A first moving step of moving the non-consumable electrode relative to the inner nozzle in a first direction from the tip of the non-consumable electrode toward the first base material during the step of applying the first main arc current. When,
After starting the first movement step, starting energization of an intermediate pilot arc current between the non-consumable electrode and the outer nozzle;
After the step of starting energization of the intermediate pilot arc current, stopping the energization of the first main arc current;
And a step of starting energization of a second main arc current between the non-consumable electrode and the second base material while the intermediate pilot arc current is flowing. A second moving step of moving the non-consumable electrode relative to the inner nozzle in a second direction opposite to the first direction;
The plasma arc welding method according to claim 1, wherein the second moving step is performed after a step of starting energization of the second main arc current.   The plasma arc welding method according to claim 1 or 2, wherein the step of stopping energization of the first main arc current is performed after the end of the first moving step. In the first moving step, the non-consumable electrode is moved relative to the inner nozzle so that the tip of the non-consumable electrode moves from the first region to the second region,
In the second moving step, the non-consumable electrode is moved relative to the inner nozzle so that the tip of the non-consumable electrode moves from the second region to the first region,
The first region is a region located on the second direction side with respect to the opening of the inner nozzle,
The plasma arc welding method according to claim 2, wherein the second region is a region positioned on the first direction side with respect to the opening.   5. The method according to claim 4, further comprising a step of continuously maintaining a state where a tip of the non-consumable electrode is positioned in the second region from the end of the first moving step to the start of the second moving step. Plasma arc welding method.   The plasma arc welding method according to any one of claims 1 to 3, wherein, in the first moving step, a tip of the non-consumable electrode is brought close to the first base material. Further comprising the step of energizing a start pilot arc current between the non-consumable electrode and the outer nozzle;
The plasma arc welding method according to any one of claims 1 to 6, wherein the step of energizing the first main arc current is started during the step of energizing the start pilot arc current. Energizing an initial pilot arc current between the non-consumable electrode and the inner nozzle;
The step of energizing the initial pilot arc current is started by applying a high frequency voltage between the non-consumable electrode and the inner nozzle,
The plasma arc welding method according to claim 7, wherein the step of energizing the start pilot arc current is shifted from the step of energizing the initial pilot arc current. An initial movement step of moving the non-consumable electrode relative to the inner nozzle in a second direction opposite to the first direction;
The step of energizing the start pilot arc current is started by applying a high frequency voltage between the non-consumable electrode and the outer nozzle,
The plasma arc welding method according to claim 7, wherein the initial movement step is performed after the start of the step of applying the first main arc current. A plasma arc welding system for performing a plasma arc welding method using a torch comprising a non-consumable electrode, an inner nozzle surrounding the non-consumable electrode, and an outer nozzle surrounding the inner nozzle,
A main arc power circuit for energizing a main arc current between the non-consumable electrode and the base material;
An electrode position control circuit that generates a first movement instruction signal while the main arc power supply circuit passes the main arc current;
A pilot arc power supply circuit that starts energization of an intermediate pilot arc current between the non-consumable electrode and the outer nozzle after the first movement instruction signal is generated,
The first movement instruction signal is a signal for moving the non-consumable electrode in a first relative movement with respect to the inner nozzle, and the first relative movement is a first direction from the tip of the non-consumable electrode toward the base material. A plasma arc welding system in which, in a direction, the non-consumable electrode moves relative to the inner nozzle. A main arc current energization detection circuit that generates a main arc current energization detection signal when detecting energization of the main arc current;
The electrode position control circuit generates a second movement instruction signal after the main arc current energization detection signal is generated,
The second movement instruction signal is a signal for moving the non-consumable electrode in a second relative movement with respect to the inner nozzle, and the second relative movement is performed in a second direction opposite to the first direction. The plasma arc welding system according to claim 10, wherein the non-consumable electrode is moved relative to an inner nozzle.   The plasma arc welding system according to claim 10, wherein the main arc power supply circuit stops energization of the main arc current after the end of the first relative movement. The torch;
A position defining mechanism for defining a position of the non-consumable electrode with respect to the inner nozzle,
The plasma arc according to any one of claims 10 to 12, wherein the position defining mechanism moves the non-consumable electrode in the first relative movement when receiving the first movement instruction signal from the electrode position control circuit. Welding system. The position defining mechanism is:
In the first relative movement, the non-consumable electrode is moved relative to the inner nozzle so that the tip of the non-consumable electrode moves from the second region to the first region,
In the second relative movement, the non-consumable electrode is moved relative to the inner nozzle so that the tip of the non-consumable electrode moves from the first region to the second region,
The first region is a region located on the second direction side with respect to the opening of the inner nozzle,
The plasma arc welding system according to claim 13, wherein the second region is a region located on the first direction side with respect to the opening.   The position defining mechanism always keeps the state where the tip of the non-consumable electrode is positioned in the second region from the end of the first relative movement to the start of the second relative movement. The plasma arc welding system described in 1.

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