JP3768394B2 - Laser / plasma composite processing equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laser processing apparatus that performs processing such as welding, cutting, drilling, heating, and melting, and more particularly, to a processing apparatus that combines laser and plasma.
[0002]
[Prior art]
For example, laser welding is capable of low distortion and high-speed welding, but since laser light has a small spot diameter, gap tolerance is small in butt welding, and high butting accuracy of the welding material is required. In Japanese Patent Laid-Open No. 2-52183, laser welding using plasma arc combined with plasma welding of an abutting portion prior to CO2 laser irradiation in order to realize butt welding with a CO2 laser even if the butt accuracy is rough. A method is disclosed.
[0003]
According to this method, the gap tolerance is increased and the quality of laser butt welding is improved. However, the efficiency of laser welding does not improve much. Here, the efficiency is the thickness of the material to be welded x the welding speed with respect to the laser power.
[0004]
JP-A-10-180479 discloses a plasma generating ring-shaped or conical cylindrical plasma electrode and a nozzle member at the tip of a laser torch, and allows laser light to pass through the central opening of the plasma electrode. A welding torch for irradiating a plasma jet and a laser beam simultaneously on the same point of a material to be welded is disclosed. The explanation is that the laser beam focused through the center of the plasma jet acts to constrict it to the plasma jet, increasing the plasma jet density (energy density) acting on the material to be welded and improving the welding efficiency. Has been.
[0005]
However, the ring-shaped or cylindrical plasma electrode can generate an arc at all points in one round, but the arc stays at one point and is consumed, and the shape of the electrode is disturbed and the discharge characteristics are likely to be unstable. it is conceivable that. That is, it is assumed that the stable operation time of the plasma electrode is short.
[0006]
In Japanese Patent Application Laid-Open No. 10-216979, a conical space connected to a nozzle at the lower end is formed at the tip of a laser torch, and a ring-shaped or conical cylindrical cathode electrode and an anode electrode are provided on the upper and lower sides. A laser machining head using a non-transfer type plasma is disclosed in which a plasma arc current is passed between the two. However, even in this case, it is considered that the arc remains at one point and is consumed, the electrode shape is disturbed, and the discharge characteristics are likely to be unstable. That is, it is assumed that the stable operation time of the plasma electrode is short. Further, since non-transfer type plasma generation, it is considered that the distance tolerance between the head and the material to be welded is very small.
[0007]
Japanese Patent Application Laid-Open No. 5-69165 discloses a TIG used in combination with a laser that includes a cylindrical electrode for TIG welding at the tip of a laser torch, and irradiates a welding target material with laser light through an opening in the center of the electrode. A welding torch is disclosed. Even in this case, it is considered that the arc remains at one point and is consumed, the electrode shape is disturbed, and the discharge characteristics are likely to be unstable.
[0008]
Japanese Laid-Open Patent Publication No. 9-122950 discloses a composite welding head in which a TIG welding electrode is disposed at the optical axis position of a laser light condensing lens group. This TIG welding electrode is a solid rod-like electrode of a round pencil, and it is assumed that the TIG arc is concentrated at the tip of the lower end thereof and the arc is stable. However, the lower end of the TIG is exposed to the outside of the torch, and the laser beam is focused just below the tip of the electrode. Therefore, it is assumed that the laser is blocked by the welding fume and the improvement in welding efficiency is low.
[0009]
By the way, YAG laser welding to aluminum has problems such as generation of blowholes and reflection of laser light on the surface. That is, the return light of the reflected light may damage the lens system of the laser processing head and the optical fiber. Although it is an extreme example, the YAG laser rod may be damaged. In order to avoid this, the machining head is tilted to prevent direct reflected light from returning into the machining head. However, by tilting the machining head, the amount of reflection of the laser beam on the aluminum surface increases, and the laser beam energy cannot be effectively applied. In addition, since the oxide film on the aluminum surface has a high melting point, high-speed welding is difficult.
[0010]
[Problems to be solved by the invention]
The present invention, machining efficiency is high and plasma generation les stable - to provide a processing apparatus for The / plasma complexed with the first object, equivalent to YAG laser of a high output YAG laser of low output A second object is to obtain machining performance.
[0011]
[Means for Solving the Problems]
(1) A small-diameter cylinder with a cooling water channel (4 ) on the circumferential surface protrudes upward from the outer flange at the lower end, and the optical axis (22) of the laser beam (21) opens through the lower end surface of the outer flange. A nozzle member (1) having a space (3) which is continuous with the nozzle (2) and has an opening larger than the nozzle (2) and which is open on an upper end surface of the small-diameter cylinder ;
An insulating member (6) having a round hole and receiving the small-diameter cylinder therein to support the nozzle member (1 ) ;
A solid rod-shaped plasma electrode (18) having a point ;
An opening (13) through which a laser beam (21) toward the nozzle (2) passes , and the plasma electrode (18) is inclined with respect to the optical axis (22) and the optical axis ( 22) an electrode support member (12, 14) coupled to the insulating member (6) , which is held in a posture and position in which the tip is directed to the nozzle (2 ) through the space (3) from a position retracted from the position;
Said insulating member (6) and the electrode support member (12, 14) means for supplying a plasma gas be in the space (3) of the nozzle member (1) between the (8-11); and,
Means (16) for coupling the electrode support members (12, 14) to a laser head (17) that emits the laser beam (21);
A laser / plasma composite processing apparatus.
[0012]
In addition, in order to make an understanding easy, the code | symbol of the corresponding element or the corresponding matter of the Example shown in drawing and mentioned later is added in the parenthesis for reference. The same applies to the following.
[0013]
According to this, the laser beam converged through the nozzle (2) passes through and acts on the plasma jet generated at the lower part of the plasma electrode, and the plasma jet density (energy density) acting on the material to be welded is increased. This improves welding efficiency. Since the plasma electrode (18) has a solid rod shape having a sharp tip, the plasma arc concentrates on the sharp tip and stays there and is stabilized. Therefore, the stable operation time of plasma irradiation is long. Since the plasma jet eliminates the fumes, there is little interruption of energy by them, and this also improves the welding efficiency .
[0014]
DETAILED DESCRIPTION OF THE INVENTION
(2) The cooling water flow path (4) is at the neck of the small-diameter cylinder; the laser / plasma composite processing apparatus according to (1) above .
[0015]
(3) wherein the means for supplying to the space (3) (8-11) of the plasma gas the nozzle member (1), the Le - inner circumferential surface of the laser light beam (21) has an opening through which opening A laser gas port (8) having a plasma gas flow path (9) opened in a direction along the circumference ; the laser / plasma composite processing apparatus according to (1) or (2) above . According to this, the plasma gas blown from the plasma gas flow path (9) enters the space (3) of the nozzle member (1) while swirling and is ionized by the arc of the electrode (18), and the nozzle (2 ) from Dell become a plasma jet of the small diameter of the swirling flow. Since it turns in a cyclone around the optical axis, the direction stability of plasma jet injection is high.
[0016]
(4) The space (3 ) of the nozzle member (1 ) is surrounded by a conical surface (3) between a large opening opened at the upper end surface of the small-diameter cylinder and a small opening connected to the nozzle (2). The laser / plasma composite processing apparatus according to (3) above . According to this, the plasma gas converges on a small-diameter turn along the conical surface (3), is ionized by the arc of the electrode (18), and exits from the nozzle 2 as a plasma jet. Since converges centrally pivoted to the cyclone-shaped around the optical axis, higher directional stability of the plasma jet.
[0017]
(5) the electrode supporting member (12, 14), said opening for passing the laser beam (21) (13), the smaller in diameter than the opening of the plasma gas inlet (8); the (3 Or the laser / plasma composite processing apparatus according to (4) . Accordingly, the electrode support member (12, 14) is, the swirling flow of the plasma gas, Runode shielding the moving direction of returning to the laser light source, the force of the orbiting convergence is strong.
[0018]
( 6 ) The laser is a YAG laser. Since the YAG laser has a light absorption rate of the metal material several times that of the CO2 laser, efficient welding is possible. Moreover, since the wavelength is 1/10 of the CO2 laser, it is not easily affected by plasma generated during welding. Since the YAG laser can be transmitted by a flexible optical fiber, it can be handled easily and an articulated robot can be used. Moreover, transmission to a distant place up to about 100 m is possible. On the other hand, the YAG laser has a high initial cost, so when introducing multiple facilities as in the automobile production line, the equipment cost becomes enormous. However, the laser light is time-divided (time sharing), With space division (power sharing), it can be distributed and transmitted to a plurality of processing stations and used for processing, and high utilization efficiency can be obtained.
[0019]
Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.
[0020]
【Example】
FIG. 1 shows the main part of one embodiment of the present invention. The outer flange of the nozzle member 1 having the nozzle 2 centered on the optical axis 22 of the YAG laser beam 21 of the YAG laser head 17 has a plurality of screws (not shown) (four distributed at a 90-degree pitch around the optical axis 22). Is fixed to the nozzle receiver 6. The small diameter cylinder of the nozzle member 1 is inserted into the round hole of the nozzle receiver 6, and the outer peripheral surface of the cylinder compresses the O-ring 7. The outer flange of the nozzle member 1 compresses the O-ring 5 by a plurality of screws (not shown). A ring-shaped cooling water flow path 4 is provided at the neck of the small-diameter cylinder of the nozzle member 1, and the flow path 4 is hermetically sealed with O-rings 5 and 7. The nozzle receiver 6 has an injection port for supplying cooling water to the flow path 4 and a discharge port for draining cooling water from the flow path 4, but these are not shown.
[0021]
On the inner end surface of the small-diameter cylinder of the nozzle member 1, there is a conical surface 3 with the nozzle 2 as a bottom and continuous therewith, which defines a conical space.
[0022]
A ring-shaped groove is formed on the inner end face of the nozzle receiver 6, and a substantially small-diameter ring-shaped plasma gas port 8 is fitted into the groove, and a substantially large-diameter ring-shaped gasket 10 is provided radially outward. Thus, a ring-shaped plasma gas flow space 23 is defined between the outer peripheral surface of the gas port 8. A plurality of plasma gas injection nozzles 9 that open to the outer peripheral surface and the inner peripheral surface and penetrate the gas port 8 in the tangential direction of the inner peripheral surface are opened in the gas port 8. The gasket 10 has a plasma gas injection port 11 communicating with the plasma gas flow space 23.
[0023]
Above the plasma gas port 8 and the gasket 10, there is an electrode holder 12, and the diameter of the center hole 13 is smaller than the diameter of the inner peripheral surface of the gas port 8. Thus, the upward diffusion of the plasma gas entering the inner space of the gas port 8 from the plasma gas injection nozzle 9 and turning is suppressed, and the turning force is increased.
[0024]
As shown in the figure, the electrode holder 12 has a solid rod-shaped (round pencil-shaped) plasma electrode 18 having a pointed tip, which is inclined with respect to the optical axis (torch axis) 22 and retracted from the optical axis 22. There is a through hole that accepts the position directed to the nozzle 2 from the position, and the plasma electrode 18 passes through the hole. The electrode holder 12 has a screw hole extending from the outer peripheral surface thereof to a through hole, and the plasma electrode 18 is fixed to the electrode holder 12 by tightening a set screw 19 screwed into the screw hole. Reference numeral 20 denotes a lock nut.
[0025]
An insulating table 14 is placed on the electrode holder 12. The insulating base 14, the electrode holder 12, the bracket 10 and the nozzle receiver 6 are integrated with a plurality of bolts 15 (three distributed at a 120-degree pitch around the optical axis 22) that pass through them and are screwed into the nozzle receiver 6. It is fixed to.
[0026]
A female screw cylinder 16 with a flange is screwed to a male screw on the outer periphery of the lower end of the YAG laser head 17, and a plurality of screws (lights) that pass through the threaded hole of the flange and are screwed into the insulating base 14. The insulating table 14 is fixedly attached to the shaft 22 at three intervals distributed at a 120-degree pitch.
[0027]
In this embodiment, the electrode holder 12 is made of a conductor (copper) so that the electric field of the arc discharge is concentrated on the pointed tip of the plasma electrode 18 and the electrolytic concentration to other than the tip of the electrode is avoided. In order to insulate the electrode holder 12, the nozzle receiver 6, the plasma gas port 8, the gasket 10, and the base 14 are used as insulators (ceramics). The nozzle member 1 is a conductor (made of copper).
[0028]
The plasma electrode 18 and the nozzle member 1 are connected to a pilot power source circuit including a pilot power source PSp, a high-frequency high-voltage trigger circuit HF, and a pilot switch SWp, and the plasma electrode 18 and the butt welding target material OB1 are transferred to each other. A main plasma power supply circuit including an AC power supply PSm and a main switch SWm is connected.
[0029]
Supply of cooling water and plasma gas is started, and if necessary, supply of gas for purging the lens for laser focusing is also started in the laser head 17, the pilot switch SWp is turned on, and the trigger circuit HF is driven. An electric discharge is triggered between the nozzle member 1 and the plasma electrode 18. Thus, when the pilot plasma is ignited, the trigger circuit HF is turned off and the main switch SWm is turned on. As a result, a transitional AC plasma arc is generated between the welding object OB1 / the plasma electrode 18, and a plasma welding operation state is set. When the emission of the YAG laser beam 21 is started, a laser / plasma composite high-efficiency butt welding operation state is set .
[0030]
In the AC plasma arc, the positive electrode and the reverse polarity arc are alternately switched in a short cycle and each shifts to the workpiece material, that is, the base material. The reverse polarity arc forms a cathode spot on the surface of the base material, and the base material, for example, aluminum The oxide film (alumina) on the surface is melted and removed. As a result, the aluminum surface is roughened in a satin state, the laser light is irregularly reflected, and the directly reflected light does not return into the head. The surface of the aluminum that has been satin-finished improves the absorption rate of laser light. In the case of laser welding of aluminum, energy concentration is high and high-speed deep penetration welding is possible. However, since the thermal conductivity is high, the molten pool is quickly solidified, and the shield gas is easily trapped and blowholes are easily generated. In the YAG laser welding to which the AC plasma is added in the above embodiment, the molten pool formed by the plasma is larger than the molten pool by the laser, and gas is easily released by stirring the plasma molten pool, so that blowholes are not easily generated. The laser beam has a small spot diameter, so there is little gap tolerance in butt welding. Especially in aluminum welding, solidification of the molten pool is fast, and close butt is required, cutting the work piece and restraining the welded part. The method is severely required, but the gap tolerance is reduced by combining with plasma welding.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a main part of one embodiment of the present invention.
[Explanation of symbols]
1: Nozzle member 2: Nozzle 3: Conical surface 4: Cooling water flow path 5: O-ring 6: Nozzle receiver 7: O-ring 8: Plasma gas port 9: Gas injection nozzle 10: Gasket 11: Gas injection port 13: Center hole 14: Insulation base 15: Bolt 16: Female screw cylinder 17: YAG laser head 18: Plasma electrode 19: Set screw 20: Lock nut 21: YAG laser beam 22: Optical axis 23: Gas flow space

Claims (6)

A small-diameter cylinder having a cooling water passage on its circumferential surface protrudes upward from the outer flange at the lower end , and there is a nozzle at the lower end surface of the outer flange through which the optical axis of the laser beam passes. A nozzle member having a larger opening and an open space on an upper end surface of the small-diameter cylinder ;
An insulating member having a round hole and receiving the small diameter cylinder to support the nozzle member;
A solid rod-shaped plasma electrode having a point ;
An opening through which the laser beam toward the nozzle passes, and the plasma electrode is inclined with respect to the optical axis and the tip is directed to the nozzle through the space from a position retracted from the optical axis And an electrode support member coupled to the insulating member for holding in position;
Means for supplying a plasma gas to the space of the nozzle member between the insulating member and the electrode support member; and
Means for coupling the electrode support member to a laser head that emits the laser beam;
A laser / plasma composite processing apparatus. The cooling water flow path is in the neck portion of the small-diameter cylinder; according to claim 1 Le - The / flop plasma processing apparatus of the composite. Means for supplying to the space of the nozzle member the plasma gas, the Le - the inner peripheral surface of the opening has an opening through which the laser light beam, a plasma gas having a plasma gas flow path open in the direction along the circumference mouth, the comprises; according to claim 1 or 2 Les - the / flop plasma processing apparatus of the composite. Wherein the space of the nozzle member is surrounded by the conical surface between a large opening open to the upper end surface of the small diameter cylinder with a small opening communicating with the nozzle; according to claim 3, Le - The / flop plasma Compound processing equipment. Said electrode support member, said apertures for transmitting the laser beam, the than the opening of the plasma gas inlet is a small diameter; according to claim 3 or 4 Les - The / flop plasma processing apparatus of the composite. Lasers are YAG lasers, claims 1 to according to any one of 5 Les - The / flop plasma processing apparatus of the composite.

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