JP7109350B2 - plasma torch - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma torch that reduces consumption of an electrode and stabilizes a plasma arc generation point.

A plasma torch, which is mainly used to cut steel plates, has an electrode in which an electrode material is embedded in the center, a rotating member that rotates around the electrode to supply plasma gas composed of oxygen gas, and a plasma gas chamber between the electrode and the electrode. and a nozzle. This plasma torch is generally mounted on a cutting device controlled by a control device represented by a numerical control device (NC device) and configured to cut a preset shape.

When the material to be cut is cut by the plasma torch, a swirling plasma gas is supplied to the plasma gas chamber via the swirling member, and a pilot arc formed by electric discharge between the electrode and the nozzle is generated at the tip of the nozzle. It is jetted from an orifice provided in to the material to be cut. After the pilot arc comes into contact with the material to be cut, a plasma arc is formed by discharging between the electrode and the material to be cut. to form Furthermore, it is possible to cut the desired shape from the material to be cut by relatively moving along a preset cutting path while removing the combustion products and molten matter of the base material from the groove. .

The plasma gas supplied to the plasma gas chamber in a swirling state forms a strong swirling flow on the tip surface of the electrode, and this swirling has the effect of stabilizing the plasma arc generation point in the electrode. In addition, the formed plasma arc is narrowed by the swirling plasma gas and becomes thinner, contributing to the improvement of the cutting performance.

However, if the swirl of the plasma gas is strengthened in an attempt to stabilize the plasma arc generation point and improve the cutting performance, a strong negative pressure acts on the center of the tip surface of the electrode (electrode material). Therefore, when the plasma arc is stopped, the electrode material melt generated on the surface of the electrode material is attracted by the plasma gas ejected from the orifice and peels off from the electrode, which causes a problem that the consumption of the electrode progresses. Several proposals have been made to solve this problem.

For example, in the plasma torch described in Patent Document 1, a plurality of types of swirl holes having different angles are formed in the centering stone. A swirling plasma gas is supplied. For this reason, a small negative pressure is applied to the electrode material by weak swirling, and the plasma arc can be narrowed by strongly swirling the outer peripheral side, so that the cutting performance can be maintained and the consumption of the electrode can be suppressed. .

In the plasma arc disclosed in Patent Document 2, a three-way solenoid valve arranged in the plasma gas pipe is configured to discharge the plasma gas remaining in the plasma gas chamber to the atmosphere when the plasma arc is stopped. is doing. Therefore, when stopping the plasma arc, the pressure in the plasma gas chamber can be quickly brought to atmospheric pressure, and consumption of the electrode material can be reduced.

Japanese Patent Application Laid-Open No. 2014-007126 (Patent No. 6029869)

Japanese Patent Application Laid-Open No. 2016-198815

Even the inventions described in Patent Literature 1 and Patent Literature 2 are not perfect, and there are points to be further improved. That is, in the invention described in Patent Document 1, it is not easy to form a plurality of turning holes having different diameters and different angles in the centering stone. There is a point that it costs money to arrange a three-way valve in the piping system and control the opening and closing of each port.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a plasma torch in which electrode consumption is reduced and the plasma arc generation point is stabilized.

In order to solve the above problems, a plasma torch according to the present invention includes an electrode having an electrode material embedded in the center of the tip surface, and a plasma gas chamber formed including a part of the outer peripheral surface of the electrode and the tip surface. a plasma gas flow passage connected to the plasma gas chamber for circulating the plasma gas in the plasma gas chamber; a plurality of swirl holes for swirling and circulating in the plasma gas chamber; and a plurality of communicating holes having a total cross-sectional area smaller than the total cross-sectional area of the

In the plasma torch described above, it is preferable that the swirl hole is arranged to face the outer peripheral surface of the electrode.

In any one of the plasma torches described above, it is preferable that a start gas or a start gas and a plasma gas or a plasma gas is supplied to the plasma gas flow passage via a flow rate retaining member.

The plasma torch according to the present invention can reduce consumption of the electrode. That is, the plasma gas flow passage is formed with a plurality of swirl holes at a connecting portion with the plasma gas chamber, and a plurality of communication holes are formed upstream of the swirl holes. The total cross-sectional area of the plurality of communication holes formed upstream of the swirl hole formed in the plasma gas flow passage at the connecting portion with the plasma gas chamber. is smaller, the communicating hole acts as a resistance to the plasma gas flow.

Therefore, when the supply of the plasma gas is stopped when the plasma arc is stopped, the plasma gas between the communication hole and the swirl hole flows into the plasma gas chamber while maintaining the flow speed substantially the same as before the stop. The flow velocity of the plasma gas remaining in the plasma gas flow passage on the upstream side of the communication hole is reduced by the resistance of the communication hole. Accordingly, the flow rate of the plasma gas flowing into the plasma gas chamber is reduced, and the swirling flow in the plasma gas chamber is moderated along with this reduction, so that strong negative pressure does not act on the electrode material. As a result, it is possible to suppress exfoliation of the molten electrode material on the surface of the electrode material, and to reduce consumption of the electrode.

The plasma gas can be made into a strong swirl flow by arranging the swirl hole formed in the connecting portion of the plasma gas flow passage with the plasma gas chamber so as to face the outer peripheral surface of the electrode. That is, since the plasma gas is jetted at an angle to the outer peripheral surface of the electrode in the swirling direction, the plasma gas swirls along the outer peripheral surface of the electrode. Therefore, the plasma gas can reach the tip surface of the electrode while maintaining the swirl along the outer peripheral surface, and can cause a strong swirling flow to act on the tip surface. Therefore, the plasma arc generation point can be stabilized.

In addition, by supplying the start gas or the start gas and the plasma gas or the plasma gas to the plasma gas flow path through the flow rate holding member, the start gas or the plasma gas can be supplied to the plasma gas chamber with little fluctuation in the flow rate. can be done.

It is a figure explaining the structure of the principal part of the plasma torch based on 1st Example. FIG. 4 is a schematic diagram illustrating a configuration when using a plasma torch; FIG. 10 is a diagram for explaining the configuration of a main part of a plasma torch according to a second embodiment;

A plasma torch according to the present invention will be described below. The plasma torch according to the present invention reduces wear of the electrode by gradually decreasing the flow rate of the plasma gas into the plasma gas chamber when stopping the plasma arc.

For this reason, it has a total cross-sectional area smaller than the total cross-sectional area of the plurality of swirl holes upstream of the plurality of swirl holes formed at the connecting portion between the plasma gas flow passage for circulating the plasma gas and the plasma gas chamber. A plurality of communication holes are formed. When the plasma gas supply to the plasma gas flow passage is cut off, the plasma gas remaining between the swirl hole and the communication hole in the plasma gas flow passage has the same pressure as when forming the plasma arc, so It flows into the plasma gas chamber.

However, although the plasma gas remaining in the plasma gas flow passage has the same pressure as when forming the plasma arc, the plurality of communication holes act as resistance, and the flow speed toward the plasma gas chamber is reduced. Therefore, the pressure and flow velocity of the plasma gas in the plasma gas chamber gradually decrease, and the attraction effect of the plasma gas on the melted electrode material existing on the surface of the electrode material is reduced, thereby reducing wear of the electrode. becomes.

In the present invention, the value of the total cross-sectional area of the plurality of swirling holes and the value of the total cross-sectional area of the plurality of communication holes are not limited, and the current value set in the plasma torch and the plasma arc are formed. It is preferable to appropriately set the value corresponding to the specifications such as the plasma gas flow rate at the time.

First, the configuration of the plasma torch according to the first embodiment will be described with reference to the drawings. As shown in FIG. 1, at the center of the torch main body A, an electrode 1 having an electrode material 2 embedded in a tip surface 1a is arranged. This electrode 1 is configured to be attachable to and detachable from an electrode table 3 .

A tubular turning member 4 made of an insulating material is fitted to the electrode 1 , and an inner nozzle 5 is fitted to the turning member 4 . A space surrounded by the electrode 1, the turning member 4, and the inner nozzle 5 constitutes a plasma gas chamber 6. As shown in FIG. The electrode 1, swivel member 4, and inner nozzle 5 are attached to the plasma torch by fastening an inner cap 7 fitted to the inner nozzle 5 to the torch main body A. As shown in FIG.

A locking projection 1c is formed on the outer peripheral surface 1b of the electrode 1, and an engaging projection 4a is formed on the inner peripheral surface of the turning member 4. As shown in FIG. Further, the tip surface 4b of the turning member 4 is formed as an abutting portion against a stepped portion 5a formed on the inner peripheral surface of the inner nozzle 5. As shown in FIG. Further, a plurality of slits are formed in the outer peripheral surface of the inner nozzle 5, and step portions 5b are also formed in these plurality of slits.

Then, the electrode 1 is fitted to the electrode base 3, the turning member 4 and the inner nozzle 5 are fitted to the electrode 1 in this order, and a stepped portion 7a that abuts on the stepped portion 5b of the inner nozzle 5 is formed on the inner peripheral surface. The inner cap 7 is fitted into the inner nozzle 5 and fastened to the torch main body A.

When the electrode 1, swivel member 4, inner nozzle 5, and inner cap 7 are attached to the torch main body A as described above, the contact between the swivel member 4 and the inner nozzle 5 along the outer peripheral surfaces of the electrode base 3 and the electrode 1. A plasma gas flow path 8 leading to the contact portion is formed.

A partition wall 4c is formed between the engaging projection 4a and the tip surface 4b on the tip side of the turning member 4 (the downstream side in the flow direction of the plasma gas flowing through the plasma gas flow passage 8; the same shall apply hereinafter). The plasma gas flow path 8 and the plasma gas chamber 6 are separated by 4c. The length of the turning member 4 is not limited, and is preferably set appropriately based on the positional relationship with a communicating hole 11 formed in the communicating member 10, which will be described later.

A plurality of swirl holes 9 are formed in the partition wall 4 c of the swirl member 4 , and the plasma gas flow passage 8 and the plasma gas chamber 6 are connected through the swirl holes 9 . A hole axis of each of the plurality of turning holes 9 is formed in a plane substantially perpendicular to the central axis of the cylindrical turning member 4 and inclined with respect to the central axis. That is, the plurality of turning holes 9 are spirally arranged around the central axis of the turning member 4 .

Each turning hole 9 is formed at a position facing the outer peripheral surface 1b of the electrode 1 between the locking projection 4a and the tip surface 4b of the turning member 4. As shown in FIG. Therefore, the plasma gas flowing into the plasma gas chamber 6 from the swirling hole 9 is jetted obliquely against the outer peripheral surface 1b of the electrode 1, and the plasma gas inside the plasma gas chamber 6 realizes a strong swirling flow. It becomes possible to This swirling flow also acts on the electrode material 2 embedded in the tip surface 1a of the electrode 1, and it becomes possible to stabilize the plasma arc generation point in the electrode material 2. FIG.

The number and diameter of the swirl holes 9 are not limited, and need to be appropriately set based on the specifications including the arc current value set for the plasma torch. For example, in this embodiment, the diameter of the turning hole 9 is set to 1.3 mm, and six turning holes 6 are formed by dividing the circumference of the partition wall 4c of the turning member 4 at equal angles.

A cylindrical communication member 10 is fitted to the electrode base 3 and arranged upstream of the swirl member 4 in the plasma gas flow passage 8 . A shielding wall 10a for blocking the plasma gas flow passage 8 is formed on the distal end side of the communicating member 10, and a plurality of communication holes 11 are formed in the shielding wall 10a. In this manner, the plasma gas flow passage 8 is blocked by the shield wall 10a of the communication member 10, thereby being separated into the upstream flow passage 8a and the downstream flow passage 8b. A communication hole 11 formed in the blocking wall 10a communicates the upstream side flow path 8a and the downstream side flow path 8b, thereby forming the plasma gas flow path 8. As shown in FIG.

A plasma gas supply passage 12 is connected to the upstream flow passage 8 a of the plasma gas flow passage 8 . The plasma gas supply path 12 is formed at a position eccentric from the central axis of the torch body A, and as shown in FIG. connected via

Therefore, even when the start gas is supplied from the start gas supply system 14 to the plasma gas flow passage 8 and the cutting gas is supplied to the plasma gas flow passage 8 from the cutting gas supply system 15 at the same time, the plasma gas does not flow. Channel 8 can be supplied with a preset flow rate of gas.

The communication hole 11 formed in the shielding wall 10a of the communication member 10 is formed substantially parallel to the central axis of the communication member 10. As shown in FIG. Therefore, the plasma gas flows from the communication hole 11 to the downstream flow passage 8b without swirling.

The number and diameter of the communication holes 11 are not limited, and need to be appropriately set based on the specifications including the arc current value and plasma gas flow rate set for the plasma torch. For example, in this embodiment, the diameter of the communication hole 11 is 0.8 mm, and the circumference of the shielding wall 10a is equally angularly divided into three communication holes 11. As shown in FIG.

As described above, since the plasma gas is supplied to the plasma gas flow passage 8 from the plasma gas supply passage 12 formed in the torch main body A, the flow velocity of the plasma gas in the upstream side flow passage 8a is not uniform. There is fear.

In this embodiment, the communication hole 11 is formed at a position facing the rear end surface 4d of the turning member 4. As shown in FIG. Therefore, the plasma gas that has flowed into the downstream flow passage 8b from the communication hole 11 collides with the rear end surface 4d of the swirl member 4 and is diffused. As a result, the plasma gas flows in the downstream flow passage 8b. can be made more uniform.

A water pipe 17 is arranged in the center of the torch main body A, and a mutually continuous water channel 18 is formed between the water pipe 17 and the electrode 1 and the electrode base 3, and between the inner nozzle 5 and the inner cap 7. . A cooling water supply device 19 shown in FIG. , cools the inner cap 7 and is collected by the cooling water supply device 19 .

The electrode 1 and the inner nozzle 5 are arranged electrically insulated, and these electrode 1 and the inner nozzle 5 are connected to the plasma power source 20 shown in FIG.

When operating the plasma torch configured as described above and connected to the start gas supply system 14 and the cutting gas supply system 15 via the flow rate holding member 13 and further connected to the cooling water supply device 19 and the plasma power source 20 The procedure and the procedure for stopping the operation will be explained.

First, the supply of the start gas from the start gas supply system 14 is started, and the start gas is supplied to the plasma gas supply path 12 and the plasma gas flow path 8 via the flow rate holding member 13 . The supplied start gas is supplied to the plasma gas chamber 6 through the communication hole 11 formed in the communication member 10 and the swirl hole 9 formed in the swirl member 4 . In this state, by energizing the electrode 1 and the inner nozzle 5 from the plasma power source 20, electric discharge is caused between them to form a pilot arc.

When the pilot arc is jetted from the inner nozzle 5 to the outside and reaches the material to be cut (not shown), the plasma power source 20 causes discharge between the electrode 1 and the material to form a plasma arc. At the same time, the supply of the start gas from the start gas supply system 14 is cut off, and the supply of the cutting gas from the cutting gas supply system 15 is started. At this time, even if each gas is supplied from both supply systems 14 and 15 in a transient state, the flow rate as a whole is held by the flow rate holding member 13 .

The target material is cut by the plasma arc jetted from the inner nozzle 5 .

When the plasma arc is formed to perform the desired cutting, the plasma gas is supplied to the plasma gas chamber 6 in a swirling state from the swirling hole 9 of the swirling member 4, and strikes the outer peripheral surface 1b of the electrode 1 obliquely. As a result, it becomes a strong swirling flow and reaches the tip surface 1a. Therefore, a strong swirling flow acts on the surface of the electrode material 2, and it becomes possible to stabilize the plasma arc generation point.

Further, the plasma gas supplied from the plasma gas supply path 12 to the upstream side flow path 8a of the plasma gas flow path 8 flows from the communication hole 11 formed in the communication member 10 to the downstream side flow path 8b. It collides with the end face 4d and diffuses. Therefore, even if the flow velocity of the plasma gas is uneven in the upstream flow passage 8a, it is possible to make the flow velocity substantially uniform by the collision of the swirl member 4 against the rear end surface 4d.

After completing the desired cut on the material to be cut, the plasma arc is stopped. At this time, when the cutting gas supply system 15 is stopped, the plasma gas existing in the downstream side flow passage 8b of the plasma gas flow passage 8 is discharged from the swirl hole 9 to the plasma gas chamber 6 while maintaining the flow velocity at which the plasma arc is formed. flow to In addition, the plasma gas present in the plasma gas supply path 12 and the upstream flow path 8a is affected by the remaining pressure when forming the plasma arc, but no new pressure is applied. The open communication hole 11 acts as a resistance, and the speed when passing through the downstream flow path 8b is reduced.

Therefore, the flow velocity of the plasma gas in the plasma gas chamber 6 is maintained at the flow velocity for forming the plasma arc when the cutting gas supply system 15 is shut off, but the plasma gas existing in the downstream flow passage 8b is After flowing into the plasma gas chamber, it decreases as the flow rate of the plasma gas flowing from the communication hole 11 decreases.

That is, the speed of the swirling flow in the plasma gas chamber 6 decreases in an extremely short time after the cutting gas supply system 15 is shut off, and the pressure acting on the electrode material 2 changes from negative pressure to positive pressure. Therefore, it is possible to reduce the possibility that the molten electrode material on the surface of the electrode material 2 is sucked by the plasma gas flow.

Next, the configuration of the plasma torch according to the second embodiment will be described. The plasma torch according to this embodiment has a turning member 25 and a communicating member 27 having different shapes from the turning member 4 and the communicating member 10 of the plasma torch according to the first embodiment described above, but the other shapes are the same. . For this reason, the same parts or parts having the same functions as those in the first embodiment are assigned the same reference numerals, and the description thereof is omitted.

The diameter of the inner peripheral surface of the turning member 25 is formed to be equal to the diameter of the inner peripheral surface of the inner nozzle 5, and the inner peripheral surface of the turning member 25 is formed with an engagement step portion 25a. Further, the tip surface 25b of the turning member 25 is formed as an abutting portion against the stepped portion 5a formed on the inner peripheral surface of the inner nozzle 5. As shown in FIG.

A partition wall 25c is formed between the engagement stepped portion 25a and the tip surface 25b on the front end side of the turning member 25, and a fitting portion 25d having a large inner diameter is formed from the partition wall 25c to the rear end side. The downstream flow passage 8b (plasma gas flow passage 8) and the plasma gas chamber 6 are separated by the partition wall 25c. Moreover, it is configured such that the distal end side of the communication member 27 can be fitted into the fitting portion 25d.

A plurality of swirl holes 26 are formed in the partition wall 25c of the swirl member 25, and the plasma gas flow passage 8 and the plasma gas chamber 6 are connected through the swirl holes 26. As shown in FIG. A plurality of swirl holes 26 are spirally arranged around the central axis of the swivel member 25 and formed at positions facing the outer peripheral surface 1 b of the electrode 1 .

A cylindrical communication member 27 is fitted to the electrode 1 upstream of the swivel member 25 . The distal end side of the communicating member 27 is fitted in the fitting portion 25 d of the turning member 25 , and the distal end surface 27 a abuts against the engagement stepped portion 25 a of the turning member 25 . Further, the rear end side outer peripheral surface of the communicating member 27 is configured to be able to contact the rear end side inner peripheral surface of the inner nozzle 5 . When the communicating member 27 is fitted into the fitting portion 25d of the turning member 25, an oblique blocking wall 27b is formed slightly upstream of the fitting portion 25d. A hole 28 is formed.

Therefore, the communicating member 27 contacts the outer peripheral surface of the electrode 1 at the inner peripheral surface on the front end side, and the outer peripheral surface on the rear end side with the inner peripheral surface of the inner nozzle, thereby closing the plasma gas flow path by the blocking wall 27b. 8 is cut off to separate into an upstream flow passage 8a and a downstream flow passage 8b. The upstream flow passage 8a and the downstream flow passage 8b communicate with each other through a communication hole 28 formed in the blocking wall 27b to form the plasma gas flow passage 8. As shown in FIG.

The number and diameter of the turning holes 26 and the number and diameter of the communication holes 28 may be the same as or different from those of the first embodiment. However, it is essential that the total cross-sectional area of the plurality of communicating holes 28 is smaller than the total cross-sectional area of the plurality of turning holes 26 .

In the plasma torch configured as described above, it is possible to reduce the distance between the swirl hole 26 formed in the swirl member 25 and the communication hole 28 formed in the communication member 27 . Therefore, the volume of the downstream flow passage 8b is reduced, and the flow velocity of the plasma gas in the plasma gas chamber 6 after stopping the plasma arc can be quickly reduced. Therefore, the negative pressure acting on the electrode material 2 is quickly changed to a positive pressure, and consumption can be reduced.

INDUSTRIAL APPLICABILITY The present invention is advantageously applied to a plasma torch in which a plasma arc is formed by a swirling flow of plasma gas.

A torch body 1 electrode 1a tip surface 1b outer peripheral surface 1c locking projection 2 electrode material 3 electrode base 4, 25 turning member 4a engaging projections 4b, 25b tip surface 4c, 25c partition wall 4d rear end surface 5 inner nozzle 5a, 5b, 7a Step 6 Plasma gas chamber 7 Inner cap 8 Plasma gas flow passage 8a Upstream flow passage 8b Downstream flow passage 9, 26 Swivel hole 10, 27 Communication member 10a, 27b Shield wall 11, 28 Communication hole 12 Plasma gas supply passage 13 Flow holding member 14 Start gas supply system 15 Cutting gas supply system 17 Water pipe 18 Water channel 19 Cooling water supply device 20 Plasma power source 25a Engagement stepped portion 25d Fitting portion 27a Tip surface

Claims (3)

an electrode in which an electrode material is embedded in the center of the tip surface;
a plasma gas chamber formed including a portion of the outer peripheral surface of the electrode and a tip surface;
a plasma gas flow passage connected to the plasma gas chamber for circulating the plasma gas in the plasma gas chamber;
a plurality of swirling holes formed in a partition disposed at a connecting portion of the plasma gas flow passage with the plasma gas chamber, for swirling the plasma gas to flow into the plasma gas chamber;
a plurality of communication holes formed in a shielding wall arranged upstream of the plurality of swirl holes in the plasma gas flow passage and having a total cross-sectional area smaller than that of the plurality of swirl holes;
A plasma torch characterized by comprising: 2. A plasma torch according to claim 1, wherein said orbital hole is arranged to face the outer peripheral surface of said electrode. 3. The plasma torch according to claim 1, wherein the plasma gas flow passage is supplied with the start gas or the start gas and the plasma gas or the plasma gas through a flow rate holding member.

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