JP2002045971A - Plasma welding torch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of defective welding due to spatter. SOLUTION: In this plasma welding torch 2, an outer circumferential surface 12s of a nozzle 12 for ejecting the plasma arc is surrounded by an outer cylindrical conductive body 14 and a conductive forward cylindrical body 20 connected to a tip of the outer cylindrical body 14, a shield gas passage 14t is formed around the nozzle 12, and a tip of the forward cylindrical body 20 is brought into contact with a work W during the welding. The nozzle 12 and the outer cylindrical body 14 are electrically connected to each other, and an insulating member 16 for electrically insulating these components is provided between the outer cylindrical body 14 and the tip cylindrical body 20. No defective welding is generated even when the spatter entering the shield gas passage 14t is stocked between the nozzle 12 and the outer cylindrical body 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nozzle for ejecting a plasma arc in which an outer peripheral surface is surrounded by a conductive outer cylinder and a conductive front cylinder connected to the tip of the outer cylinder. The present invention relates to a plasma welding torch having a structure in which a shield gas passage is formed around a nozzle, and a tip of the front cylindrical body contacts a workpiece during welding.

[0002]

2. Description of the Related Art A general plasma welding torch used in a plasma welding machine is shown in FIG. Plasma welding torch 5
0 has a nozzle 52 for ejecting a plasma arc. The nozzle 52 is made of metal, and the electrode 51 is housed in the center of the nozzle 52 via an insulating guide 52r. Note that a plasma gas passage 52t is formed between the electrode 51 and the nozzle 52. The outer peripheral surface of the nozzle 52 is surrounded by a metal outer cylinder 54, and a shield gas passage 5 is provided between the outer cylinder 54 and the outer peripheral surface of the nozzle 52.
4t is formed. An insulating ring 53 made of, for example, ceramic is set between the outer cylinder 54 and the outer peripheral surface of the nozzle 52, and the nozzle 52 is positioned coaxially with the outer cylinder 54, and the nozzle 52 and the outer Electrical insulation between the cylinder 54 is provided.

[0003] At the tip of the outer cylinder 54, a metal tip cylinder 56 is provided.
Are mounted coaxially. The front cylinder 56 is a cylindrical member that forms a shield gas passage 54t around the nozzle 52 together with the outer cylinder 54, and is brought into contact with the surface of the plate-shaped workpiece W during welding. Therefore, the front cylinder 56 and the outer cylinder 54 are electrically connected to the work W and are kept at the same potential. In the plasma welding, a pilot arc is first generated between the nozzle 52 and the electrode 51 while the tip cylinder 56 is in contact with the work W, and then the pilot arc is transferred to the main arc between the work W and the electrode 51. Then, the work W is welded. For this reason, between the nozzle 52 and the electrode 51, the work W
It is necessary to electrically insulate the electrode 51 and the nozzle 52 from the workpiece W (the front cylinder 56 and the outer cylinder 54).

[0004]

In the above-described plasma welding torch, the nozzle 52 and the outer cylinder 5 are connected by the insulating ring 53.
4. The tip cylinder 56 and the workpiece W are electrically insulated. However, when the spatter K generated by welding enters the shield gas passage 54t, the spatter K accumulates at the position of the insulating ring 53 disposed across the shield gas passage 54t, and short-circuits between the outer cylinder 54 and the nozzle 52. May be caused. In particular, when welding is performed on the vertical wall portion of the work W from the lateral direction, the spatter K is generated in the shielding gas passage 5.
Since a large amount of spatter K accumulates at the position of the insulating ring 53, a short circuit is likely to occur between the outer cylinder 54 and the nozzle 52 because the depth of the insulating ring 53 is large. When the outer cylinder 54 and the nozzle 52 are short-circuited, a part of the main arc current flows to the work W through the sputter K, and a welding failure occurs.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to prevent a short circuit from occurring between a nozzle constituting a shielding gas passage and an outer cylinder, and to prevent the occurrence of poor welding. Aim.

[0006]

The above-mentioned objects are attained by the present invention. According to the first aspect of the present invention, an outer peripheral surface of a nozzle for ejecting a plasma arc is surrounded by a conductive outer cylinder and a conductive front cylinder connected to a tip of the outer cylinder, and is provided around the nozzle. A plasma welding torch having a structure in which a shield gas passage is formed and a tip of the front cylindrical body contacts a workpiece during welding, wherein the nozzle and the outer cylindrical body are electrically connected to each other, An insulating member that electrically insulates the two is provided between the front cylinder and the front cylinder.

According to the present invention, since the nozzle and the outer cylinder are electrically connected to each other, even if spatters entering the shield gas passage accumulate between the nozzle and the outer cylinder, a conventional welding method is used. No defect problem occurs. Further, since the insulating member is provided between the outer cylinder and the front cylinder, the nozzle connected to the outer cylinder and the work in contact with the front cylinder are electrically insulated. Furthermore, since the insulating member is not disposed at a position blocking the shield gas passage, spatter hardly accumulates at the position of the insulating member, and no short circuit occurs between the outer cylinder and the front cylinder.

Here, as shown in the second aspect of the present invention, the fitting portion of the nozzle used for positioning the outer cylinder with respect to the nozzle is fitted to the fitted portion of the outer cylinder, so that the outer cylinder is fitted. The cylinder and the nozzle may be electrically connected. Further, when the insulating member is disposed at a position not facing the shield gas passage as in the invention of claim 3, it is not necessary to consider the adhesion of spatter, and the range of selecting the material of the insulating member is widened. For example, as a material of the insulating member, a resin or the like can be used. by this,
Processing of the insulating member is facilitated. Further, if the insulating member can be screwed to the distal end portion of the outer cylindrical body as in the invention of claim 5, replacement of the insulating member becomes easy. Further, if an insulating cylinder is provided inside the front cylinder as in the invention of claim 5, a short circuit between the outer cylinder and the front cylinder is more unlikely to occur.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A plasma welding torch according to one embodiment of the present invention will be described below with reference to FIGS. Here, FIG. 1 is a longitudinal sectional view of a tip portion of a plasma welding torch, FIG. 2 is a longitudinal sectional view of a tip portion of the plasma welding torch in a state where a front cylinder is separated, and FIG. 3 is a plasma welding machine having a plasma welding torch. 4 to 6 are schematic diagrams showing the operation principle of the plasma welding machine. Note that the following description will be made assuming that the axial direction of the plasma welding torch is the Z-axis direction, the vertical direction and the horizontal direction of a plane perpendicular to the axis are the X-axis direction and the Y-axis direction, respectively.

[0010] The plasma welding machine 1 generates a high-temperature plasma flow (plasma arc) using arc discharge, and uses the heat to generate, for example, a joint (hereinafter referred to as a workpiece W) in a vehicle body.
) And is attached to a hand of a welding robot (not shown). As shown in FIG. 3, the plasma welding machine 1 includes an apparatus gantry 3, and the plasma welding torch 2 and its attached units 42 and 44 are supported on the apparatus gantry 3. A reference surface 3s is formed on the device mount 3, and a torch escape cylinder 4 and a pressure cylinder 5 are arranged in series in the Z-axis direction at the center of the reference surface 3s.

A torch mount 4k is attached to a piston rod 4p of the torch escape cylinder 4, and a torch main body 10 of the plasma welding torch 2 is mounted on the torch mount 4k. Further, a pressurizing gantry 5k is attached to the piston rod 5p of the pressurizing cylinder 5, and the front cylinder 20 of the plasma welding torch 2 is fixed to the torch main body 10 coaxially with the pressurizing gantry 5k. When the pressurizing cylinder 5 operates in a direction to extend the piston rod 5p,
The pressurizing gantry 5k advances in the Z-axis direction, and the distal end surface 22 of the front cylindrical body 20 of the plasma welding torch 2 is pressed against the surface of the work W.

When the torch escape cylinder 4 is operated in a direction to accommodate the piston rod 4p, the torch mount 4k
The torch body 1 of the plasma welding torch 2 advanced in the axial direction
0 is fitted to the front cylinder 20 (see FIG. 1). Here, since the driving force of the torch escape cylinder 4 is set sufficiently smaller than the driving force of the pressurizing cylinder 5, the torch body 10
Does not displace even if it moves forward and fits with the front cylinder 20. In addition, since the torch escape cylinder 4 has a sufficient stroke in a state where the torch main body 10 is connected to the front cylinder body 20, even if the front cylinder body 20 moves forward by the force of the pressurizing cylinder 5, the torch main body 10 does not The robot can move forward following the front cylinder 20. When the torch escape cylinder 4 operates in a direction to extend the piston rod 4p, the torch mount 4
When k is retracted, the torch main body 10 is separated from the front cylindrical body 20 (see FIG. 2).

The plasma welding torch 2 is a part for actually generating a plasma arc in the plasma welding machine 1, and comprises the torch main body 10 and the front cylinder 20 as described above. As shown in FIG. 2, the torch main body 10 includes a nozzle 12 for ejecting a plasma arc. The nozzle 12 is made of metal, and the electrode 11 is housed in the center of the nozzle 12 via an insulating guide 12r. A plasma gas passage 12t is formed between the electrode 11 and the nozzle 12, and an opening 12k for discharging a high-temperature plasma flow and a plasma gas is formed at the tip of the nozzle 12.

An outer peripheral surface 12s of the nozzle 12 is surrounded by a tapered outer cylinder 14, and a shield gas passage 14t is formed between the outer cylinder 14 and the outer peripheral surface 12s of the nozzle 12. The outer cylinder 14 is made of metal, and a ring-shaped convex step 14 d is formed on the inner wall surface of the outer cylinder 14 in the circumferential direction of the outer cylinder 14. On the outer peripheral surface 12s of the nozzle 12, a ring-shaped concave step 12d in which the convex step 14d of the outer cylindrical body 14 fits is formed in the circumferential direction. When the concave step 12d of the nozzle 12 and the convex step 14d of the outer cylinder 14 are fitted to each other, the nozzle 12 and the outer cylinder 14 are held coaxially.
4 are electrically connected. That is, the convex step 14d and the concave step 12d correspond to the fitting portion and the fitted portion of the present invention. A plurality of shield gas passages 14t (see dotted lines) are formed in the fitting portion between the convex step 14d and the concave step 12d at intervals in the circumferential direction.

A ring-shaped concave portion 14a into which an insulating member 16 to be described later is fitted is formed outside the distal end portion of the outer cylindrical body 14. Ring-shaped steps 14c and 14e are formed at two places in the recess 14a so that the outer cylindrical body 14 gradually tapers, and a medium-diameter cylindrical surface 14b is formed between the ring-shaped steps 14c and 14e. Is formed. Medium diameter cylindrical surface 1
A ring-shaped groove 14m is formed in the center of 4b in the circumferential direction, and an O-ring 1 made of heat-resistant rubber is formed in the ring-shaped groove 14m.
5 is fitted. In the recess 14a, a small-diameter cylindrical surface 14h is formed between a ring-shaped step 14e near the front end and a front end surface 14f of the outer cylindrical body 14, and a male screw is formed on the small-diameter cylindrical surface 14h. .

The insulating member 16 is a ring-shaped member that electrically insulates between the outer cylindrical body 14 and a front cylindrical body 20 described later.
For example, it is formed of Teflon (registered trademark) resin. The insulating member 16 has an inner peripheral surface shape substantially equal to the shape of the concave portion 14 a of the outer cylindrical body 14, and is fitted outside the distal end portion of the outer cylindrical body 14 by being fitted into the concave portion 14 a.
That is, a large-diameter cylindrical surface 16t that covers the medium-diameter cylindrical surface 14b of the outer cylinder 14 and a small-diameter cylindrical surface 16h that covers the small-diameter cylindrical surface 14h of the outer cylinder 14 are formed on the inner peripheral wall surface of the insulating member 16. A ring-shaped receiving step 16d is formed between the large-diameter cylindrical surface 16t and the small-diameter cylindrical surface 16h to contact the ring-shaped step 14e of the outer cylinder 14.

On the small-diameter cylindrical surface 16h of the insulating member 16, there is formed a female screw to be screwed with a male screw provided on the small-diameter cylindrical surface 14h of the outer cylinder 14. Therefore, when the female screw of the insulating member 16 is screwed into the male screw of the outer cylinder 14,
Due to the screwing action, the insulating member 16 and the outer cylinder 14 are relatively moved in the axial direction, and the outer cylinder 14 has a medium-diameter cylindrical surface 14b,
The small-diameter cylindrical surface 14h is accommodated in the large-diameter cylindrical surface 16t and the small-diameter cylindrical surface 16h of the insulating member 16, respectively.

Then, the receiving step 16d of the insulating member 16 comes into contact with the ring-shaped step 14e of the outer cylinder 14, and the insulating member 1
6 at the stage where the rear end surface 16u abuts on the ring-shaped step 14a of the outer cylinder 14, attachment of the insulating member 16 to the outer cylinder 14 is completed. Is held at a position substantially continuous with the front end face 14f of the second member.

The O-ring 15 set in the ring-shaped groove 14m of the outer cylinder 14 is deformed by a pressing force from the outside in the radial direction by the insulating member 16. Therefore, the looseness between the female screw of the insulating member 16 and the male screw of the outer cylinder 14 is suppressed by the elastic force of the O-ring 15. The outer peripheral surface of the insulating member 16 is knurled in consideration of workability when screwing a female screw of the insulating member 16 with a male screw of the outer cylinder 14.

The front cylindrical body 20 of the plasma welding torch 2 is a cylindrical member having a function of pressing the surface of the work W during welding and a function of forming a shield gas passage 14t together with the outer cylindrical body 14 as described above. Is mounted on the tip side surface of the pressurizing gantry 5k which advances and retreats in the Z-axis direction. Tip cylinder 20
Is composed of a metal cylinder main body 21 and an insulating cylinder 24 fixed to the inner wall surface of the cylinder main body 21. Tube body 21
Is formed of, for example, an S45C quenching material that is resistant to impact, and the tip end surface 22 of the cylinder main body 21 abuts around the welding point of the workpiece W. The axial length of the cylinder body 21 is set to a value that allows the dimension between the tip surface 12f of the nozzle 12 and the workpiece W to be maintained at a constant value M during welding, as shown in FIG. . A plurality of openings 21a are provided at the end of the cylinder main body 21 along the circumferential direction to communicate the inside space surrounded by the cylinder main body 21 with the outside. From the outside.

The insulating cylinder 24 is a member that electrically insulates between the cylinder main body 21 and the outer cylinder 14 and between the cylinder main body 21 and the nozzle 12, and has an outer diameter substantially equal to the inner diameter of the cylinder main body 21. The insulating cylinder 24 is a ceramic cylindrical body, and a flange-like flange portion 24f is formed at the rear end of the insulating cylinder 24. In addition, the length of the insulating cylinder 24 is set to approximately の of the length of the cylinder main body 21.

A ring-shaped concave portion 21 into which the insulating member 16 of the outer cylindrical body 14 fits in the center of the rear end surface 21b of the cylindrical main body 21.
e is formed. Further, the ring-shaped concave portion 21e
A ring-shaped step 21d into which the flange portion 24f of the insulating tube 24 is fitted is formed on the inside in the radial direction of. Here, the thickness of the flange portion 24f of the insulating cylinder 24 is set substantially equal to the depth of the ring-shaped step 21d. For this reason, when the insulating tube 24 is fixed to the inner wall surface of the tube main body 21 and the flange portion 24f of the insulating tube 24 is fitted into the ring-shaped step 21d of the tube main body 21, the surface of the flange portion 24f of the insulating tube 24 ( The rear surface) is the ring-shaped recess 2 of the cylinder body 21.
It becomes continuous with the bottom surface of 1e.

When the torch main body 10 advances in the Z-axis direction by the function of the torch release cylinder 4, the distal end of the outer cylindrical body 14 of the torch main body 10 becomes a ring-shaped recess 21e of the front cylindrical body 20, as shown in FIG. And the tip portion of the nozzle 12 is housed inside the front cylindrical body 20. As a result, the outer peripheral surface 12s of the nozzle 12 is covered by the outer cylinder 14 and the front cylinder 20, and a shield gas passage 14t is formed around the nozzle 12. Here, since the insulating member 16 is attached to the outer end of the outer cylindrical body 14, the insulating member 16 does not face the shield gas passage 14t.

In a state in which the distal end of the outer cylinder 14 is fitted into the ring-shaped recess 21e of the front cylinder 20, the distal end face 14f of the outer cylinder 14 contacts the insulating cylinder 24 of the front cylinder 20, The front end face 16f of the insulating member 16 of the outer cylinder 14 contacts the insulating cylinder 24 of the front cylinder 20 and the ring-shaped recess 21e of the cylinder main body 21. Therefore, the insulating member 16 and the insulating tube 24 electrically insulate the outer tube 14 and the tube body 21 from each other. A wire guide 4 for guiding the welding wire T to a position closer to the tip than the insulating tube 24 is provided on the tube main body 21 of the front tube 20.
4w is connected.

Next, a procedure for welding the workpiece W using the plasma welding machine 1 having the above-described structure will be described. First, the torch escape cylinder 4 operates and the torch mount 4k
Moves forward, and the outer cylinder 14 of the torch main body 10 of the plasma welding torch 2 is connected to the front cylinder 20 (see FIG. 1). As described above, since the torch escape cylinder 4 has a sufficient stroke in a state where the torch main body 10 is connected to the front cylinder 20, even if the front cylinder 20 advances with the force of the pressurizing cylinder 5,
The torch main body 10 can move forward following the front cylindrical body 20.

When the plasma welding torch 2 is assembled in this manner, the plasma welding torch 2 is positioned near a welding point of the workpiece W by a robot (not shown). Next, the pressurizing cylinder 5 operates to advance the front cylinder body 20 of the plasma welding torch 2 in the Z-axis direction, and pressurizes the work W around the welding point as shown in FIG. As a result, the gap between the stacked plate-shaped works W is reduced to a value that enables plasma welding.

Next, a procedure until the work W is actually welded will be briefly described with reference to FIGS. First, a plasma gas and a shield gas are supplied to the plasma gas passage 12t and the shield gas passage 14t of the plasma welding torch 2, respectively. Further, a DC voltage is applied between the electrode 11 and the nozzle 12 by the plasma power supply 30 (see FIG. 4). Next, the high-frequency generation circuit 32 operates to apply a high-frequency high voltage between the electrode 11 and the nozzle 12, and a spark is generated between the electrode 11 and the nozzle 12.

When a spark is generated between the electrode 11 and the nozzle 12, the spark is used to form a pilot arc between the electrode 11 and the nozzle 12 (see FIG. 5). Then, when the high-temperature plasma generated by the pilot arc is ejected from the nozzle 12 and reaches the work W, a voltage is generated between the work W and the nozzle 12, and as shown in FIG. The transition occurs. After the shift to the main arc, the pilot line is cut off by the switch 33, and welding is performed in this state.

Here, the nozzle 1 of the plasma welding torch 2
2 and the outer cylinder 14 are fitted and electrically connected to each other at the positions of the concave step 12d and the convex step 14d. For this reason, even if spatters that enter the shield gas passage 14t accumulate between the nozzle 12 and the outer cylinder 14, problems such as poor welding do not occur. Since the insulating member 16 is provided between the outer cylinder 14 and the front cylinder 20, the outer cylinder 1
4 is electrically insulated between the nozzle 12 connected to the workpiece 4 and the workpiece W in contact with the front cylindrical body 20. Further, the insulating member 1
6 is not disposed at a position that blocks the shield gas passage 14t, so that spatter does not accumulate at the position of the insulating member 16 and no short circuit occurs between the outer cylinder 14 and the front cylinder 20.

The insulating member 16 is connected to the shielding gas passage 1.
Since it is arranged at a position not facing 4t, there is no need to consider adhesion of spatter, and the range of selection of the material of the insulating member 16 is widened. If a resin is used as the material of the insulating member 16 as in the present embodiment, the processing of the insulating member 16 becomes easy, and the manufacturing cost of the insulating member 16 can be reduced. Further, since the insulating member 16 can be screwed to the distal end portion of the outer cylindrical body 14, replacement of the insulating member 16 becomes easy.

In this embodiment, an example is shown in which Teflon resin is used as the insulating member 16, but it is of course possible to use a resin other than Teflon. In addition, it is also possible to use, for example, ceramic or the like other than the resin. Also, the example in which the insulating member 16 is disposed at a position not facing the shield gas passage 14t has been described. However, if the insulating member 16 is made of a material such as ceramics, the insulating member 16 can be disposed at a position facing the shield gas passage 14t. It is.

[0032]

According to the present invention, even if spatters entering the shield gas passage accumulate between the nozzle and the outer cylinder, a short circuit does not occur between the nozzle and the outer cylinder. The occurrence of defects can be prevented.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a tip portion of a plasma welding torch according to one embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a tip portion of a plasma welding torch in a state where a front cylinder is separated.

FIG. 3 is a side view of a plasma welding machine including the plasma welding torch.

FIG. 4 is a schematic view illustrating the operation principle of the plasma welding machine.

FIG. 5 is a schematic view illustrating an operation principle of the plasma welding machine.

FIG. 6 is a schematic view illustrating the operation principle of the plasma welding machine.

FIG. 7 is a longitudinal sectional view of a tip portion of a conventional plasma welding torch.

[Explanation of symbols]

 W Work 2 Plasma welding torch 11 Electrode 12 Nozzle 12d Concave step (fitting part) 14 Outer cylinder 14d Convex step (fitting part) 16 Insulating member 20 Front cylinder

Claims (6)

[Claims] An outer peripheral surface of a nozzle for jetting a plasma arc is surrounded by a conductive outer cylinder and a conductive front cylinder connected to a tip of the outer cylinder, and a shielding gas is provided around the nozzle. A passage is formed, the plasma welding torch having a structure in which a tip of the front cylinder contacts a workpiece during welding, wherein the nozzle and the outer cylinder are electrically connected,
A plasma welding torch characterized in that an insulating member for electrically insulating the outer cylinder and the front cylinder is provided between the outer cylinder and the front cylinder. 2. The plasma welding torch according to claim 1, wherein a fitting portion formed on an outer peripheral surface of the nozzle and a fitted portion formed on an inner wall surface of the outer cylinder are fitted. The positioning of the outer cylinder with respect to the nozzle is performed, and the outer cylinder and the nozzle are electrically connected. 3. The plasma welding torch according to claim 1, wherein the insulating member is formed in a cylindrical shape, and a step formed in the outer tube and a step formed in the front tube. And the distal end portion of the outer cylinder is disposed inside the insulating member, whereby the insulating member is disposed at a position not facing the shield gas passage. Plasma welding torch. 4. The plasma welding torch according to claim 3, wherein the insulating member is formed of a resin. 5. The plasma welding torch according to claim 3, wherein a female screw is formed on an inner wall surface of the insulating member, and the female screw is formed on an outer peripheral surface of a distal end portion of the outer cylindrical body. A plasma welding torch, wherein the insulating member is attached to a distal end of the outer cylinder by screwing with a screw. 6. The plasma welding torch according to claim 1, wherein an insulating cylinder is provided inside the front cylinder.