JP7181780B2 - Laser processing equipment - Google Patents

Description

The present invention relates to a laser processing apparatus.

In recent years, the output of laser processing apparatuses has been increasing. A laser processing method called laser peening is one of the application techniques of high-output lasers. Laser peening is a processing technique in which plasma is generated on the surface of a workpiece such as metal by irradiating it with laser light, and the surface is plastically deformed by shock waves generated by the plasma pressure. This plastic deformation imparts a compressive residual stress to the surface of the workpiece, which is expected to have the effect of hardening the surface of the workpiece and improving the wear resistance of the surface of the workpiece. Therefore, laser peening is expected as a processing technique for increasing the strength of parts in the field of transportation equipment such as automobiles and aircraft.

Patent Literature 1 and Patent Literature 2 describe a laser processing apparatus for performing such laser peening. In the laser processing apparatus described in Patent Literature 1, the surface of the workpiece is processed by laser peening in a state where the portion of the surface of the workpiece irradiated with laser light is covered with liquid. Patent Literature 2 describes that a workpiece can be placed in the air or in a vacuum when performing laser peening.

Japanese Patent Publication No. 2016-515475 JP 2017-189815 A

For example, as in the laser processing apparatus described in Patent Document 1, when the surface of the workpiece is placed in a liquid and the surface of the workpiece is irradiated with a laser beam, the plasma generated on the surface of the workpiece is Increases the confinement effect. Therefore, in this case, a sufficient compressive residual stress can be easily imparted to the surface of the workpiece as compared with the case where the workpiece is placed in the atmosphere. However, when laser peening is performed while the workpiece is placed in the liquid, for example, processes such as a liquid spraying process, a liquid recovery process, and a workpiece drying process are required, resulting in poor processing efficiency. decreases.

On the other hand, in recent years, a technique has been discovered in which compressive residual stress is imparted to the surface of a workpiece by irradiating the surface of the workpiece with a laser beam having a high peak intensity without confining the plasma with liquid. However, when the above method is applied to a work piece placed in the air, if the peak intensity of the laser beam becomes high to some extent, ionization occurs in the air before the laser light reaches the surface of the work piece. A phenomenon (breakdown) is more likely to occur. When such an ionization phenomenon occurs in the atmosphere, the resulting heat can cause problems such as an increase in surface roughness of the workpiece and a decrease in compressive residual stress imparted to the surface of the workpiece. In addition, when laser peening is performed without placing the workpiece in the liquid as described above, the droplets of the workpiece generated by the irradiation of the laser beam tend to float, and the irradiation of the floating droplet with the laser beam causes Problems such as plasmification of droplets and scattering of laser light tend to occur. As a result, it becomes increasingly difficult to apply sufficient compressive residual stress to the surface of the workpiece, making it difficult to obtain the effects of hardening the surface of the workpiece and improving the wear resistance of the surface of the workpiece. can be.

The present invention has been made to solve the above problems, and is a laser processing apparatus capable of continuously irradiating the surface of a workpiece with a laser beam having a high peak intensity while suppressing a decrease in processing efficiency. intended to provide

A laser processing apparatus according to one embodiment of the present invention is a laser processing apparatus that performs processing by irradiating a laser beam onto a surface of a workpiece, wherein an inner space is defined by an inner surface and a surface, and the inner space is defined by an inner surface and a surface. At least part of the optical path of the laser light between the light source that emits the laser light and the surface, including the portion irradiated with the laser light on the surface, is in the internal space. A droplet adsorber is provided in the inner space for adsorbing droplets of the workpiece generated from the irradiated portion.

In this laser processing apparatus, at least part of the optical path of the laser beam emitted from the light source, including the irradiated portion of the surface of the workpiece, is located in the internal space of the container, and the internal space is at atmospheric pressure. maintained at a reduced pressure. In such a reduced pressure internal space, the threshold value of the peak intensity of the laser beam, which is a condition for the occurrence of the ionization phenomenon, is higher than in the case of the atmospheric pressure state, and the occurrence of the ionization phenomenon is suppressed. Therefore, even when a laser beam having a high peak intensity is irradiated onto the surface of the workpiece, the laser beam reaches the surface of the workpiece by reducing the pressure at least in part of the optical path of the laser beam. It is possible to suppress the occurrence of the ionization phenomenon before the As a result, problems such as an increase in surface roughness of the workpiece and a decrease in compressive residual stress applied to the surface of the workpiece can be suppressed. It becomes possible to apply sufficient compressive residual stress to the surface. Furthermore, in the laser processing apparatus described above, the internal space defined by the inner surface of the container and the surface of the workpiece is in a decompressed state. According to this configuration, the reduced pressure state can be maintained on the surface of the workpiece without housing the entire workpiece in the container, so the volume of the internal space to be reduced in pressure can be reduced. As a result, it is possible to reduce the time required to depressurize the internal space. Furthermore, according to the above-described configuration, sufficient compressive residual stress can be applied to the surface of the workpiece without confining the plasma with the liquid, so that it is possible to suppress the reduction in processing efficiency due to the use of the liquid. Furthermore, in the laser processing apparatus described above, a droplet adsorber is provided in the interior space of the container for adsorbing droplets of the workpiece generated from the irradiated portion of the surface of the workpiece. By providing this droplet adsorbent in the internal space, droplets floating in the internal space can be reduced. As a result, it is possible to suppress the occurrence of problems such as plasmification of the droplets and scattering of the laser beam due to irradiation of the floating droplets with the laser beam. As a result, it is possible to continuously irradiate the surface of the workpiece with a laser beam having a high peak intensity, and to suppress a decrease in compressive residual stress imparted to the surface of the workpiece. Therefore, according to the laser processing apparatus described above, it is possible to easily generate sufficient compressive residual stress on the surface of the workpiece by continuously irradiating the surface of the workpiece with a laser beam having a high peak intensity while suppressing a decrease in processing efficiency. can be given to

In the laser processing apparatus described above, the container may maintain the internal space in a vacuum state. In this case, a laser beam having a higher peak intensity can be used to apply a greater compressive residual stress to the surface of the workpiece.

The laser processing apparatus described above may further include a light source, and the light source may be a femtosecond laser light source. In this case, it is possible to suitably realize a configuration in which sufficient compressive residual stress is applied to the surface of the workpiece using a laser beam having a high peak intensity.

In the laser processing apparatus described above, the droplet adsorbent may contain the same material as the material of the workpiece. In this case, droplets of the workpiece are more likely to be adsorbed by the droplet adsorber, so the droplets floating in the internal space of the container can be effectively reduced.

In the laser processing apparatus described above, the container may move relative to the workpiece in the direction along the surface. According to this configuration, it is possible to move the irradiated portion of the surface of the workpiece to an arbitrary position while maintaining the decompressed state of the internal space.

In the laser processing apparatus described above, the light source may be arranged outside the container, and the container may have an optical window arranged on the optical path of the laser beam and transmitting the laser beam. In this case, droplets floating in the inner space of the container are adsorbed by the droplet adsorber, whereby adhesion of the droplets to the optical window on the optical path of the laser beam can be suppressed. That is, it is possible to suppress the droplets from remaining on the optical path of the laser beam. As a result, continuous irradiation of the laser beam onto the surface of the workpiece can be realized more reliably, and reduction in compressive residual stress imparted to the surface of the workpiece can be more reliably suppressed. Furthermore, according to the above configuration, since the light source is arranged outside the container, it is possible to suppress an increase in the outer dimensions of the container and avoid an increase in the size of the laser processing apparatus. Furthermore, according to this configuration, the volume of the internal space to be decompressed can be reduced. As a result, it is possible to reduce the time required to depressurize the internal space.

In the laser processing apparatus described above, the container has a wall portion extending in a direction that intersects with one direction along the surface, the optical window is provided in the wall portion, and the laser beam is directed to the outside of the wall portion. A mirror may be provided in the internal space for reflecting the laser light that has passed through the optical window toward the irradiated portion of the surface. In this configuration, the laser light emitted from the light source is incident on the optical window along one direction along the surface. can be suppressed. This makes it possible to improve the safety of workers.

In the laser processing apparatus described above, the mirror may be arranged in a direction inclined from the normal direction of the surface of the workpiece with the irradiated portion as a starting point. The droplets of the workpiece generated from the irradiated portion tend to float more in the normal direction of the surface of the workpiece. Therefore, by adopting a configuration in which the mirrors on the optical path of the laser light are not arranged in the normal direction as described above, adhesion of droplets to the mirrors can be suppressed. That is, it is possible to suppress the droplets from remaining on the optical path of the laser beam. As a result, continuous irradiation of the laser beam onto the surface of the workpiece can be realized more reliably, and reduction in compressive residual stress imparted to the surface of the workpiece can be more reliably suppressed.

In the laser processing apparatus described above, the droplet adsorbent may face the irradiated portion in the normal direction of the surface. As described above, droplets of the workpiece generated from the irradiated portion tend to float in the normal direction of the surface of the workpiece. Therefore, the floating of the droplets in the internal space of the container can be effectively reduced by placing the droplet adsorbent in the normal direction opposite to the irradiated portion.

In the laser processing apparatus described above, the container has a main body portion provided with an opening and a lid portion that closes the opening. It is provided to be openable and closable, and the droplet adsorbent may be detachably attached to a portion of the inner surface of the lid. According to this configuration, it is possible to periodically replace the droplet adsorbent that has adsorbed the droplets in the internal space of the container. By periodically replacing the droplet adsorbent in this way, it is possible to continuously adsorb droplets by the droplet adsorbent over a long period of time.

In the laser processing apparatus described above, the inner space is provided with a shielding plate that faces the irradiated portion in the normal direction of the surface and shields the droplets, and the optical window is provided with the irradiated portion in the normal direction with respect to the shielding plate. is arranged on the opposite side, and a lens is provided on the optical path between the light source and the shielding plate to condense the laser beam toward the irradiated portion. Including holes, the area of the through holes may be smaller than the area of the optical window. By condensing the laser light passing through the through-hole of the shielding plate with the lens in this way, the area of the through-hole can be reduced according to the focused diameter of the laser light. By making the area of the through-hole smaller than the area of the optical window, it is possible to reduce droplets that pass through the through-hole from the irradiated portion and travel toward the optical window, effectively suppressing adhesion of the droplets to the optical window. can. As a result, continuous irradiation of the laser beam onto the surface of the workpiece can be realized more reliably, and reduction in compressive residual stress imparted to the surface of the workpiece can be more reliably suppressed.

In the laser processing apparatus described above, the through hole may be arranged at the focal position of the laser beam by the lens. In this case, the area of the through-hole through which the laser beam from the light source passes can be minimized, so that droplets from the irradiated portion that pass through the through-hole toward the optical window can be further reduced. As a result, adhesion of droplets to the optical window can be more effectively suppressed.

In the laser processing apparatus described above, the droplet attracting body may be a shielding plate. In this case, since the droplet attracting body also serves as a shielding plate, the configuration of the laser processing apparatus can be simplified.

An object of the present invention is to provide a laser processing apparatus capable of continuously irradiating the surface of a workpiece with a laser beam having a high peak intensity while suppressing a decrease in processing efficiency.

FIG. 1 is a schematic configuration diagram showing a laser processing apparatus according to one embodiment. FIG. 2 is a schematic cross-sectional view of the laser processing apparatus shown in FIG. FIG. 3 is a diagram showing how a droplet adsorbent is attached to the lid portion of the container shown in FIG. FIG. 4 is a graph showing the relationship between the threshold of the peak intensity of the laser beam and the pressure, which is the plasma generation condition. FIG. 5 is a graph showing the relationship between the intensity of laser light and the half width of a workpiece. FIG. 6 is a schematic configuration diagram showing a laser processing apparatus according to a first modified example. FIG. 7 is a schematic configuration diagram showing a laser processing apparatus according to a second modification. FIG. 8 is a diagram showing how a droplet adsorbent is attached to the cover of the container of the laser processing apparatus according to the third modification. FIG. 9 is a diagram showing how a droplet adsorber is attached to the lid portion of the container of the laser processing apparatus according to the fourth modification.

Hereinafter, a laser processing apparatus 1 according to an embodiment of the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and overlapping descriptions are omitted as appropriate.

FIG. 1 is a schematic configuration diagram showing a laser processing apparatus 1 according to this embodiment. FIG. 1 shows an XYZ orthogonal coordinate system for easy understanding. The laser processing apparatus 1 is an apparatus that irradiates a surface 2a of a workpiece 2 with a laser beam L to generate plasma on the surface 2a and plastically deform the surface 2a by shock waves generated by the plasma pressure. The workpiece 2 is, for example, a part used in transportation equipment such as automobiles or aircraft, and is made of a metal material such as copper, aluminum, steel plate, titanium, or alloys thereof. The surface 2a of the workpiece 2 is subjected to surface processing such as polishing. The surface 2a is smoothed by this surface processing. In the following description, each of the X direction and the Y direction indicates the direction along the surface 2a, and the Z direction indicates the normal direction of the surface 2a.

As shown in FIG. 1, the laser processing apparatus 1 includes a light source 10 that emits a laser beam L and a container 20 that is placed on the surface 2a of the workpiece 2. As shown in FIG. The light source 10 is, for example, a femtosecond laser light source, and emits laser light L in the Y direction. The peak intensity of the laser beam L is set within a range of, for example, 1.0×10 ¹⁴ W/cm ² or more and 1.0×10 ¹⁵ W/cm ² or less on the surface 2a of the workpiece 2 (after condensing). be done. The pulse width and repetition frequency of the laser light L are set to such an extent that the roughness of the surface 2a is not increased within the above range of peak intensity. The pulse width of the laser light L is, for example, 200 fs or less. The light source 10 is arranged outside the container 20 and, in one example, faces the container 20 in the Y direction. The laser beam L emitted from the light source 10 is applied to the surface 2 a of the workpiece 2 through the container 20 . Note that the light source 10 is not limited to the femtosecond laser light source, and may be another light source. For example, light source 10 may be a nanosecond laser light source or a picosecond laser light source.

The container 20 is a hollow container that airtightly holds a portion of the surface 2a, and is made of a metal material such as copper, aluminum, or steel plate. The container 20 has a hollow rectangular parallelepiped shape with one side in the Z direction, that is, the surface 2a side, open. It has a rectangular shape extending in both directions. The length d1 of the container 20 in the Y direction is, for example, 500 mm, the width d2 of the container 20 in the X direction is, for example, 300 mm, and the height d3 of the container 20 in the Z direction is, for example, 150 mm. The height d3 in the Z direction of the container 20 is smaller than the length d1 in the Y direction and the width d2 in the X direction. The container 20 is arranged so as to be relatively movable with respect to the surface 2a by sliding with respect to the surface 2a in the X direction and the Y direction.

FIG. 2 is a schematic cross-sectional view showing the laser processing device 1 cut along the YZ plane including the optical axis of the laser beam L. As shown in FIG. 2, the light source 10 is omitted. As shown in FIGS. 1 and 2, the container 20 includes a rectangular tubular main body 21 having openings 21a and 21b at both ends in the Z direction, and a rectangular plate-like lid 25 closing the opening 21a. and The opening 21b is provided on the surface 2a side of the body portion 21 in the Z direction, and the opening 21a is provided on the side opposite to the opening 21b. The body portion 21 includes four side wall portions 22 forming openings 21a and 21b. Each side wall portion 22 has a rectangular plate shape extending along the XZ plane or the YZ plane, and is arranged between the surface 2a and the lid portion 25 in the Z direction. Each side wall portion 22 includes an inner surface 22a facing the inside of the body portion 21 . The inner surface 22a extends along the Z direction from the opening 21a to the opening 21b. A side wall portion 22A, which is one of the four side wall portions 22, is arranged on the side of the light source 10 in the Y direction of the main body portion 21 and extends along the XZ plane. The side wall portion 22A faces the light source 10 in the Y direction.

The side wall portion 22A includes an optical window 23 through which the laser light L is transmitted. The optical window 23 is made of a glass material such as quartz glass. The optical window 23 is arranged on the optical path of the laser light L between the light source 10 and the surface 2a. Specifically, the optical window 23 is fitted in an opening formed in a portion of the side wall portion 22A near the opening 21a. A light incident surface and a light exit surface of the optical window 23 extend along the XZ plane and have, for example, a circular shape when viewed from the Y direction. The area of the optical window 23 viewed from the Y direction is larger than the optical path area of the laser light L when passing through the optical window 23 . A laser beam L emitted from the light source 10 enters the optical window 23 in the Y direction.

An end surface 22c of each side wall portion 22 on the side of the surface 2a in the Z direction is provided with an annular groove 22d extending so as to surround the opening 21b of the body portion 21. As shown in FIG. 22 d of groove|channels are exhibiting rectangular shape in the cross section orthogonal to the extending direction of 22 d of groove|channels. A sealing member 30 for hermetically sealing the internal space V of the container 20 is arranged in the groove 22d. The sealing member 30 is an annular member that extends along the groove 22d and is made of an elastic material such as rubber. The sealing member 30 has, for example, a circular shape in a cross section perpendicular to the extending direction of the sealing member 30 .

The outer diameter of the sealing member 30 in a cross section orthogonal to the extending direction of the sealing member 30 is larger than the depth of the groove 22d (specifically, the distance in the Z direction from the bottom surface of the groove 22d to the end surface 22c), The sealing member 30 is in contact with both the bottom surface of the groove 22 d and the surface 2 a of the workpiece 2 . The sealing member 30 is elastically deformed by being pressed by the bottom surface of the groove 22d and the surface 2a. As a result, the opening 21b of the body portion 21 is closed by the surface 2a, and the internal space V is hermetically sealed. Each side wall portion 22 is provided with a lubricant supply pipe 31 for supplying a lubricant such as grease or oil from the outside of the container 20 to the sealing member 30 . The lubricant supply pipe 31 extends from the outside of the container 20 through the inside of the side wall portion 22 and reaches the bottom surface of the groove 22d. The lubricant supplied from the lubricant supply pipe 31 reduces the frictional resistance between the sealing member 30 and the surface 2a. This makes it possible to easily perform relative movement by sliding between the container 20 and the workpiece 2 .

By supplying the lubricant to the sealing member 30 before processing the surface 2a with the laser beam L, thermal damage to the sealing member 30 and the surface 2a due to frictional heat can be suppressed, and the sealing member 30 and the surface 2a can be suppressed. can keep the internal space V sealed. Thereby, the pressure in the internal space V can be maintained. Further, the container 20 moves relative to the surface 2a while the lubricant from the lubricant supply pipe 31 is supplied to the surface 2a through the sealing member 30, so that a thin film of the lubricant is formed on the surface 2a. be. In the coating formed on the surface 2a in this way, if the lubricant is transparent to the laser light, the confinement effect of the plasma generated on the surface 2a by the irradiation of the laser light L is exhibited. This makes it possible to reduce the peak intensity of the laser light L required for processing. That is, even when the surface 2a is irradiated with the laser beam L whose peak intensity is suppressed to some extent, it is possible to apply sufficient residual compressive stress to the surface 2a. On the other hand, when the lubricant absorbs the laser light, when the coating formed on the surface 2a is irradiated with the laser light L, the lubricant absorbs the laser light L to generate plasma. Thereby, the roughness of the surface 2a can be suppressed.

Furthermore, after processing the surface 2a with the laser beam L, by forming a film of a lubricant on the surface 2a, it is possible to suppress the occurrence of oxidation (rust) on the surface 2a. In addition, by including carbon particles in the lubricant, it is possible to further reduce the frictional resistance between the sealing member 30 and the surface 2a. Furthermore, when a coating of a lubricant containing carbon particles is formed on the surface 2a, the coating further increases the amount of light absorption of the laser light L and increases the Young's modulus of the lubricant, resulting in a plasma confinement effect. improves. This makes it possible to further reduce the peak intensity of the laser light L required for processing.

A lid portion 25 of the container 20 is provided so as to be openable and closable with respect to the main body portion 21 . Specifically, the lid portion 25 is attached to the body portion 21 by being fitted into the opening 21a of the body portion 21 via an elastic body such as rubber (for example, an O-ring). Alternatively, the lid portion 25 may be attached to the body portion 21 by being screwed via an elastic body such as rubber (for example, an O-ring). The lid portion 25 includes an inner surface 25 a facing the inside of the container 20 . The inner surface 25a extends along the XY plane and faces the surface 2a in the Z direction. The inner surface 25a is in contact with one end of each side wall portion 22 on the side of the opening 21a in the Z direction. The inner surface 25 a and each inner surface 22 a form an inner surface 20 a of the container 20 .

The internal space V of the container 20 is a substantially rectangular parallelepiped airtight space defined by the inner surface 20 a of the container 20 and the surface 2 a of the workpiece 2 . A portion La of the optical path of the laser light L between the light source 10 and the surface 2a, which includes the irradiated portion P of the laser light L on the surface 2a, is located in the internal space V. That is, the internal space V includes a portion La of the optical path of the laser beam L. As shown in FIG. A portion La is an optical path from the transmission of the laser light L through the optical window 23 to the irradiated portion P. FIG. In addition, the internal space V may include all optical paths of the laser light L between the light source 10 and the surface 2a.

The internal space V is maintained in a state where the pressure is reduced below the atmospheric pressure by an exhaust mechanism 35 provided in the lid portion 25 . In this embodiment, the internal space V is maintained in a vacuum state. A vacuum state refers to a state in which the pressure in the internal space V is, for example, 0.1 MPa or less. The exhaust mechanism 35 includes an exhaust hole 36 that penetrates the lid portion 25 in the Z direction and communicates with the internal space V, an exhaust pump 37 that is arranged outside the container 20 and exhausts the internal space V, and an exhaust hole 36. It includes an exhaust pipe 38 that connects the exhaust pump 37 to each other, and a valve 39 that is provided in the exhaust pipe 38 and adjusts the exhaust amount of the internal space V. As shown in FIG.

In the internal space V, there is a concave mirror 40 having a concave reflecting surface 40a (mirror) that reflects the laser light L transmitted through the optical window 23 toward the irradiated portion P of the surface 2a and condenses the light toward the irradiated portion P. is provided. The concave mirror 40 is provided at a corner formed by an inner surface 22a of the side wall portion 22 facing the side wall portion 22A in the Y direction and an inner surface 25a of the lid portion 25 . The reflecting surface 40a has a parabolic shape whose focal position is set to coincide with the irradiated portion P of the surface 2a of the workpiece 2, faces the optical window 23 in the Y direction, and faces the optical window 23 in the Z direction. It faces the surface 2a. The reflecting surface 40a is provided in a direction inclined from the Z direction with the irradiated portion P as a starting point. That is, the reflecting surface 40a is provided at a position other than the position facing the irradiated portion P in the Z direction. The laser beam L that has entered the internal space V through the optical window 23 is reflected toward the irradiated portion P and condensed toward the irradiated portion P on the reflecting surface 40a. At this time, the irradiated portion P is irradiated with the laser beam L from a direction inclined with respect to the Z direction with the irradiated portion P as a starting point. The angle between the optical axis of the laser beam L extending from the reflecting surface 40a to the irradiated portion P and the tangent plane to the irradiated portion P of the surface 2a is, for example, 60° or less.

In the internal space V of the container 20, a droplet adsorber (droplet adsorption unit) 50 that adsorbs the droplets S of the workpiece 2 generated from the irradiated portion P is further provided. The droplets S of the workpiece 2 are ion species in plasma that are generated by plasmatization in the irradiated portion P of the surface 2a. The droplet adsorbent 50 is a plate-like member extending along the XY plane. The droplet adsorbent 50 includes, for example, glass, resin, ceramics, or a metal material such as a pure metal or an alloy. In this embodiment, the droplet adsorbent 50 is configured including the same material as the material of the workpiece 2 . That is, the droplet adsorbent 50 is configured including a metal material such as copper, aluminum, or steel plate. The surface of the droplet adsorbent 50 is subjected to surface treatment such as sanding, optical polishing, plating, or application of an adhesive.

The droplet adsorbent 50 is arranged, for example, so as to face the irradiated portion P of the surface 2a in the Z direction. That is, the droplet adsorbent 50 is arranged so as to overlap the irradiated portion P when viewed from the Z direction. In this embodiment, the droplet adsorbent 50 is arranged on the inner surface 25 a of the lid portion 25 . The droplet adsorbent 50 includes a surface 50a facing the irradiated portion P in the Z direction, and a back surface 50b positioned opposite to the surface 50a and facing (in one example, contacting) the inner surface 25a. Each of the front surface 50a and the back surface 50b extends along the XY plane. The area of the surface 50a of the droplet adsorbent 50 viewed from the Z direction is sufficiently large relative to the area of the irradiated portion P viewed from the Z direction, and the thickness of the droplet adsorbent 50 in the Z direction (i.e., the surface 50a and the back surface 50b ) is thin enough not to reach the part La of the optical path of the laser light L in the internal space V.

Specifically, the droplet adsorber 50 is detachably attached to the inner surface 25 a of the lid portion 25 . FIG. 3 is a view showing how the droplet adsorbent 50 is attached to the inner surface 25a of the lid portion 25. As shown in FIG. As shown in FIG. 3, the lid portion 25 has a plurality (three in this embodiment) of rails 26A, 26B, and 26C for attaching the droplet adsorbent 50 to the inner surface 25a. Each of the rails 26A and 26B extends along the Y direction and faces each other along the X direction near the center of the inner surface 25a. It is considered movable.

The rail 26A has a first protrusion 26a that protrudes from the inner surface 25a in the Z direction and extends along the Y direction, and a second protrusion 26b that protrudes in the X direction from the tip of the first protrusion 26a in the Z direction. It is bent in an L shape by the first projecting portion 26a and the second projecting portion 26b. Similarly, the rail 26B has a first protrusion 26c that protrudes from the inner surface 25a in the Z direction and extends along the Y direction, and a second protrusion that protrudes in the X direction from the tip of the first protrusion 26c in the Z direction. 26d, and is bent into an L shape by the first protrusion 26c and the second protrusion 26d.

The first protrusions 26a and 26c face each other with a predetermined distance in the X direction, and the distance in the X direction between the first protrusions 26a and 26c is the same as the width of the droplet adsorbent 50 in the X direction. or slightly larger. The second protruding portions 26b and 26d are opposed to each other in the X direction and protrude in the mutually opposing direction. The second protrusions 26b and 26d face the inner surface 25a in the Z direction, and the distance between the second protrusions 26b and 26d and the inner surface 25a is the same as the thickness of the droplet adsorbent 50 in the Z direction. or slightly larger.

The rail 26C extends along the X direction near the center of the inner surface 25a and functions as a stopper that defines the position in the Y direction of the droplet adsorbent 50 that is slid in the Y direction by the rails 26A and 26B. The rail 26C is arranged at a position spaced apart from the rails 26A and 26B in the Y direction when viewed from the X direction. The rail 26C has a first protrusion 26e that protrudes from the inner surface 25a in the Z direction and extends along the X direction, and a tip of the first protrusion 26e in the Z direction that protrudes in the Y direction toward the rails 26A and 26B. It is bent in an L shape by the first protrusion 26e and the second protrusion 26f. The second projecting portion 26f faces the inner surface 25a in the Z direction, and the distance between the second projecting portion 26f and the inner surface 25a is the same as or slightly larger than the thickness of the droplet adsorbent 50 in the Z direction.

When attaching the droplet adsorbent 50 to the inner surface 25a of the lid portion 25, the droplet adsorbent 50 is attached to the L-shaped inner portion of the rails 26A and 26B from the opposite side of the rails 26A and 26B in the Y direction to the rail 26C. Plug in. After that, the droplet attracting body 50 is slid in the Y direction along the inner portions of the rails 26A and 26B until it abuts against the first projecting portion 26e of the rail 26C. When removing the droplet adsorbent 50 from the inner surface 25a, the droplet adsorbent 50 is slid on the rails 26A and 26B on the side opposite to the rail 26C. As a result, the droplet attracting body 50 is removed from the rails 26A, 26B, and 26C, and the droplet attracting body 50 is removed from the inner surface 25a.

In the laser processing apparatus 1 having the above configuration, the laser beam L emitted from the light source 10 travels along the Y direction and then passes through the optical window 23 to enter the internal space V of the container 20 . The laser light L that has entered the internal space V travels along the Y direction and then enters the reflecting surface 40 a of the concave mirror 40 . After that, the laser light L is reflected toward the irradiated portion P of the surface 50a and condensed toward the irradiated portion P by the reflecting surface 40a. When the irradiated portion P is irradiated with the laser beam L, the irradiated portion P of the surface 2a of the workpiece 2 is instantly vaporized by the laser beam L having a high peak intensity, and high-pressure plasma is generated at the irradiated portion P. Inflate.

At this time, the irradiated portion P is plastically deformed due to reaction when the high-pressure plasma expands, and compressive residual stress is applied to the irradiated portion P. After that, while moving the container 20 relative to the workpiece 2 in the X and Y directions, compressive residual stress is sequentially applied to a desired region (for example, the entire surface 2a) of the surface 2a of the workpiece 2. , the laser peening process for the workpiece 2 is completed. When the irradiated portion P is irradiated with the laser beam L, droplets S of the workpiece 2 are generated from the irradiated portion P. As shown in FIG. Most of the droplets S generated from the irradiated portion P float in the Z direction and are adsorbed on the surface 50a of the droplet adsorber 50 attached to the inner surface 25a of the lid portion 25 .

Effects obtained by the laser processing apparatus 1 according to the present embodiment described above will be described. In the laser processing apparatus 1, a portion La of the optical path of the laser light L emitted from the light source 10 is located in the internal space V of the container 20, and the internal space V is in a state where the pressure is reduced below the atmospheric pressure (this is maintained in a vacuum state in the embodiment). In the internal space V thus depressurized, the threshold of the peak intensity of the laser light L, which is a condition for the occurrence of the ionization phenomenon, is higher than in the case of the atmospheric pressure state, and the occurrence of the ionization phenomenon is suppressed. be. FIG. 4 is a graph showing the relationship between the threshold of the peak intensity of the laser beam L and the pressure, which is the condition for generating the ionization phenomenon. In FIG. 4, the vertical axis indicates the peak intensity (W/cm ² ) of the laser light L, and the horizontal axis indicates the pressure (Pa). A graph G10 shows the threshold of the peak intensity of the laser light L, which is the condition for generating the ionization phenomenon.

In FIG. 4, when the peak intensity of the laser light L under a certain pressure is located on the lower side of the graph G10 (the hatched portion), the peak intensity of the laser light L is the condition for generating the ionization phenomenon. It means that the peak intensity threshold has not been reached. Conversely, when the peak intensity of the laser beam L under a certain pressure is located on the upper side of the graph G10, it means that the peak intensity exceeds the threshold of the peak intensity of the laser beam L, which is the condition for generating the ionization phenomenon. means. Therefore, when the workpiece 2 is processed using the laser beam L having a high peak intensity, the ionization phenomenon in the internal space V is caused by reducing the pressure in the internal space V so as to be positioned below the graph G10. It is possible to suppress the occurrence of

For example, when the workpiece 2 is processed using a laser beam L having a pulse width of 100 fs and a peak intensity of 1.0×10 ¹⁵ W/cm ² , the peak intensity of the laser beam L, which is a condition for generating an ionization phenomenon, is By reducing the pressure in the internal space V so that it is located on the left side of the plot P10 showing the threshold of , that is, 1.0 × 10 ⁴ Pa or less, the occurrence of the ionization phenomenon in the internal space V is suppressed. becomes possible. As described above, even when the surface 2a of the workpiece 2 is irradiated with the laser beam L having a high peak intensity, a part La of the optical path of the laser beam L is positioned in the internal space V in a decompressed state. It is possible to suppress the occurrence of the ionization phenomenon before reaching the surface 2 a of the workpiece 2 .

As a result, using the laser beam L having a peak intensity about four to five orders of magnitude higher than when the workpiece 2 is processed under atmospheric pressure, sufficient compressive residual stress is generated on the surface 2a of the workpiece 2. can be imparted, and the hardness of the surface 2a of the workpiece 2 can be improved. Here, the relationship between the peak intensity of the laser beam L and the hardness of the surface 2a of the workpiece 2 will be described with reference to FIG. FIG. 5 is a graph showing the relationship between the peak intensity of the laser beam L and the half width of the workpiece 2 irradiated with the laser beam L. As shown in FIG. In FIG. 5, the horizontal axis indicates the peak intensity (W/cm ² ) of the laser light L on the surface 2a, and the vertical axis indicates the half width (°) of the surface 2a. The half width indicates the width of the X-ray diffraction peak at half the intensity of the X-ray diffraction peak obtained by irradiating the workpiece 2 with X-rays, and increases as the hardness of the surface 2a of the workpiece 2 increases. Become. Note that FIG. 5 illustrates a case in which high-strength steel is used as the material of the workpiece 2 .

Therefore, whether or not the hardness of the surface 2a of the workpiece 2 has improved can be determined by measuring the size of this half-value width. In FIG. 5, a half-value width A indicates the original half-value width of the workpiece 2 . The original half width of the workpiece 2 is the half width of the workpiece 2 before the laser beam L is applied to the workpiece 2 and the workpiece 2 is not processed such as surface processing. The value width (that is, the half value width of the material of the base material of the workpiece 2) is shown. If the measured half-value width of the workpiece 2 is larger than the half-value width A, it means that the hardness of the surface 2a of the workpiece 2 is higher than that of the original workpiece 2 . In FIG. 5, the plot indicated by black circles indicates the half-value width of the surface 2a after the surface 2a is irradiated with the laser beam L (hereinafter simply referred to as "after irradiation"), and the plot indicated by white circles is , shows the half width of the surface 2a before the surface 2a is irradiated with the laser light L (hereinafter simply referred to as "before irradiation").

As shown in FIG. 5, the half-value width of the surface 2a before irradiation is smaller than the original half-value width A of the surface 2a of the workpiece 2. As shown in FIG. This is because when the surface 2a of the workpiece 2 is subjected to surface processing such as polishing, the surface 2a is affected by frictional heat and the like. On the other hand, the half-value width of the surface 2a after irradiation is larger than the half-value width of the surface 2a before irradiation. The magnitude of the variation (increase width) of the half-value width of the surface 2a after irradiation with the laser beam L with respect to the surface 2a before irradiation depends on the magnitude of the peak intensity of the laser beam L with which the surface 2a is irradiated. As shown in FIG. 5, when the peak intensity of the laser light L is set as low as about 1.0×10 ⁸ W/cm ² to 1.0×10 ¹⁰ W/cm ² , the irradiated surface 2a The increase in the half-value width of the surface 2a before irradiation is small, and the half-value width of the surface 2a after irradiation is lower than the half-value width A of the original surface 2a of the workpiece 2. there is

On the other hand, when the peak intensity of the laser beam L is set to a high value of about 1.0×10 ¹⁴ W/cm ² to 1.0×10 ¹⁵ W/cm ² , the half-value width of the surface 2a after irradiation is The increase from the half-value width of the surface 2 a before irradiation is large, and the half-value width of the surface 2 a after irradiation exceeds the original half-value width A of the surface 2 a of the workpiece 2 . Thus, it can be seen that the hardness of the surface 2a of the workpiece 2 can be improved by machining the workpiece 2 using the laser beam L having a high peak intensity. Also, if the peak intensity of the laser beam L is greater than 1.0×10 ¹⁵ W/cm ² , the surface roughness of the workpiece 2 tends to increase (for example, 10 μm or more). Therefore, in order to improve the hardness of the surface 2a of the workpiece 2 while suppressing an increase in surface roughness, the peak intensity of the laser beam L should be set to 1.0×10 ¹⁴ W/cm ² to 1.0×10 W/cm 2 . It is desirable to set it to about ¹⁵ W/cm ² (range of region R surrounded by a dashed line in FIG. 5).

Furthermore, according to the laser processing apparatus 1 according to the present embodiment, sufficient compressive residual stress can be applied to the surface 2a without confining the plasma with a liquid, so it is possible to suppress a decrease in processing efficiency due to the use of liquid. . Furthermore, in the laser processing apparatus 1, the internal space V defined by the inner surface 20a of the container 20 and the surface 2a of the workpiece 2 is in a decompressed state. According to this configuration, the reduced pressure state can be maintained on the surface 2a of the workpiece 2 without containing the entire workpiece 2 in the container 20, so the volume of the internal space V to be reduced in pressure can be reduced. can be done. As a result, the time required to decompress the internal space V can be reduced. Further, in the laser processing apparatus 1, a droplet attracting body 50 is provided in the internal space V for absorbing the droplets S of the workpiece 2 generated from the irradiated portion P of the surface 2a. By providing the droplet adsorbent 50 in the internal space V, the droplets S floating in the internal space V can be reduced. As a result, it is possible to suppress the occurrence of problems such as plasmification of the droplets S and scattering of the laser beam L due to the irradiation of the laser beam L to the floating droplets S. As a result, it is possible to continuously irradiate the surface 2a with the laser beam L having a high peak intensity, and to suppress a decrease in compressive residual stress applied to the surface 2a. Therefore, according to the laser processing apparatus 1 according to the present embodiment, by continuously irradiating the surface 2a with the laser beam L having a high peak intensity while suppressing a decrease in processing efficiency, sufficient compressive residual stress is applied to the surface 2a. can be easily given. As a result, it is possible to easily obtain the effects of hardening the surface 2a and improving the wear resistance of the surface 2a.

In the laser processing apparatus 1, the container 20 maintains the internal space V in a vacuum state. Thereby, a larger compressive residual stress can be applied to the surface 2a by using the laser beam L having a higher peak intensity.

In the laser processing apparatus 1, the light source 10 is a femtosecond laser light source. Thereby, it is possible to suitably realize a configuration in which sufficient compressive residual stress is applied to the surface 2a by using the laser beam L having a high peak intensity.

In the laser processing apparatus 1 , the droplet adsorbent 50 contains the same material as the material of the workpiece 2 . This makes it easier for the droplets S of the workpiece 2 to be adsorbed by the droplets adsorber 50, so that the droplets S floating in the internal space V of the container 20 can be effectively reduced.

In the laser processing apparatus 1, the container 20 moves relative to the workpiece 2 in the X and Y directions. According to this configuration, the irradiation portion P on the surface 2a of the workpiece 2 can be moved to an arbitrary position while maintaining the internal space V in a decompressed state (a vacuum state in this embodiment). That is, it is possible to avoid a situation in which the container 20 is removed from the surface 2a and the internal space V is brought into a vacuum state every time the irradiated portion P is moved to an arbitrary position. As a result, it is possible to save time and effort when moving the irradiated portion P to an arbitrary position, and to shorten the processing time by reducing the number of times of depressurization.

In the laser processing apparatus 1, the light source 10 is arranged outside the container 20, and the container 20 is arranged on the optical path of the laser beam L and has an optical window 23 through which the laser beam L is transmitted. As a result, the droplets S floating in the internal space V of the container 20 are absorbed by the droplets adsorbent 50, so that adhesion of the droplets S to the optical window 23 on the optical path of the laser beam L can be suppressed. That is, it is possible to suppress the droplets S from remaining on the optical path of the laser light L. As a result, continuous irradiation of the laser beam L onto the surface 2a can be realized more reliably, and reduction in compressive residual stress imparted to the surface 2a can be more reliably suppressed. Furthermore, according to the above configuration, since the light source 10 is arranged outside the container 20, an increase in the external dimensions of the container 20 can be suppressed, and an increase in the size of the laser processing apparatus 1 can be avoided. Furthermore, according to this configuration, the volume of the internal space V to be depressurized can be reduced. As a result, the time required to decompress the internal space V can be reduced.

In the laser processing apparatus 1, the optical window 23 is provided in the side wall portion 22A, and the laser light L enters the optical window 23 along the Y direction from the outside of the side wall portion 22A. A concave mirror 40 having a reflecting surface 40a for reflecting the laser light L transmitted through the window 23 toward the irradiated portion P of the surface 2a is provided. In this configuration, the laser light L emitted from the light source 10 is incident on the optical window 23 along the Y direction along the surface 2a. can be suppressed from facing the worker. This makes it possible to improve the safety of workers. Further, when the container 20 is moved relative to the workpiece 2 in the X and Y directions, the direction (Y direction) in which the optical path of the laser light L from the outside of the container 20 toward the optical window 23 extends. By moving the container 20 along, it is possible to irradiate each position of the surface 2a along the Y direction with the laser light L without moving the position of the light source 10 . After that, after moving the light source 10 and the container 20 in the X direction as necessary, the container 20 is moved again in the Y direction while irradiating each position along the Y direction on the surface 2a with the laser light L. By repeating the above, it is possible to more reliably irradiate the laser light L onto a desired region along the X direction and the Y direction of the surface 2a with a simple operation.

In the laser processing apparatus 1, the reflecting surface 40a of the concave mirror 40 is arranged in a direction inclined from the Z direction. A large amount of droplets S of the workpiece 2 generated from the irradiated portion P tends to float in the Z direction. Therefore, by arranging the reflective surface 40a on the optical path of the laser beam L not in the Z direction as described above, adhesion of the droplets S to the reflective surface 40a can be suppressed. That is, it is possible to prevent the droplets S from remaining on the optical path of the laser light L. As a result, continuous irradiation of the laser beam L onto the surface 2a can be realized more reliably, and reduction in compressive residual stress imparted to the surface 2a can be more reliably suppressed.

In the laser processing apparatus 1, the droplet adsorbent 50 faces the irradiated portion P in the Z direction. As described above, the droplets S of the workpiece 2 generated from the irradiated portion P tend to float in the Z direction. Therefore, the floating of the droplets S in the internal space V of the container 20 can be effectively reduced by making the droplet adsorbent 50 face the irradiated portion P in the Z direction.

In the laser processing apparatus 1, the container 20 has a body portion 21 provided with an opening 21a and a lid portion 25 that closes the opening 21a. It includes an inner surface 25a and is provided to be openable and closable with respect to the main body 21, and the droplet adsorber 50 is detachably attached to the inner surface 25a. According to this configuration, the droplet adsorber 50 that has adsorbed the droplets S in the internal space V of the container 20 can be periodically replaced. By periodically replacing the droplet adsorbent 50 in this manner, the droplet adsorbent 50 can continue to adsorb the droplets S over a long period of time.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and various modifications can be made. For example, various modifications shown in FIGS. 6 to 9 may be adopted.

FIG. 6 is a schematic cross-sectional view showing a laser processing apparatus 1A according to the first modified example. The difference between this modified example and the above-described embodiment is that a gas supply mechanism 60 is further provided on the lid portion 25A of the container 20A. A gas supply mechanism 60 is provided to supply the gas G to the internal space V of the container 20A. Gas G is a gas containing carbon. In this modified example, the gas G is acetylene gas and the workpiece 2 is a steel plate. The gas supply mechanism 60 includes a supply hole 61 that penetrates the lid portion 25A in the Z direction and communicates with the internal space V, a supply pipe 62 that is connected to the supply hole 61 and into which the gas G flows, and a supply pipe 62 that flows into the supply pipe 62. and a valve 63 for adjusting the flow rate of the gas G. The gas G that has flowed into the supply pipe 62 is supplied to the internal space V through the supply hole 61 after the flow rate is adjusted by the valve 63 .

In the laser processing apparatus 1A according to this modified example, first, similarly to the embodiment described above, the irradiated portion P is irradiated with the laser beam L to apply compressive residual stress to the irradiated portion P. After that, the gas supply mechanism 60 supplies the gas G into the internal space V, and then the irradiated portion P is irradiated with the laser light L again. The peak intensity and pulse width of the laser light L irradiated at this time are the temperature at which the acetylene gas is decomposed into carbon and hydrogen without melting the irradiated portion P, and the temperature at which the decomposed carbon is diffused into the irradiated portion P. is set to be This temperature is, for example, 900° C. when the workpiece 2 is a steel plate as in this modified example. When the irradiated portion P is irradiated with the laser beam L set in this way while the gas G (that is, acetylene gas) is supplied to the internal space V, the acetylene gas is decomposed into carbon and hydrogen, and decomposed. The carbon is diffused into the irradiated portion P and embedded in the irradiated portion P. That is, the irradiated portion P is carburized.

When the irradiated portion P is carburized as described above, the hardness of the irradiated portion P is increased. Therefore, according to the laser processing apparatus 1A according to this modified example, it is possible to further improve the hardness of the surface 2a of the workpiece 2. FIG. The gas G is not limited to acetylene gas, and may be other gas containing carbon. Examples of other gases containing carbon include gases such as methane, ethylene, or propane. Instead of using the gas G, the surface 2a of the workpiece 2 may be carburized by applying a welding graphite paste material to the surface 2a. Alternatively, the gas G may be a mixed gas in which a carbon-containing gas is mixed with a nitrogen-containing gas. For example, the gas G may be a mixed gas in which acetylene gas is mixed with ammonia gas. In this case, the irradiated portion P is carburized by the carbon contained in the acetylene gas, and the irradiated portion P is nitrided by the nitrogen contained in the ammonia gas. As a result, the hardness of the surface 2a of the workpiece 2 is expected to be further improved. Alternatively, after nitrogen is introduced into the internal space V, the surface 2a of the workpiece 2 may be irradiated with the laser beam L to convert the nitrogen molecules on the surface 2a into plasma, thereby nitriding the surface 2a.

FIG. 7 is a schematic cross-sectional view showing a laser processing apparatus 1B according to a second modification. In this modified example, the optical window 23 is provided in the lid portion 25B of the container 20B, and the droplet adsorbent 50A is provided in the internal space V of the container 20B instead of the droplet adsorbent 50. FIG. 50 A of droplet adsorption bodies are arrange|positioned between the cover part 25B and the irradiation part P in a Z direction. The optical window 23 is arranged on the side opposite to the irradiated portion P with respect to the droplet adsorbent 50A in the Z direction. That is, the optical window 23 is arranged at a position facing the irradiated portion P in the lid portion 25B.

Further, the concave mirror 40 is not provided in the internal space V of the container 20B, and a lens 70 is provided on the optical path of the laser light L between the light source 10 and the droplet adsorbent 50A. The lens 70 is a condensing lens that condenses the laser light L. As shown in FIG. The lens 70 is arranged, for example, outside the container 20</b>B and arranged on the optical path of the laser light L between the light source 10 and the optical window 23 . In this modification, the lens 70 is arranged at a position facing the optical window 23 in the Z direction. The laser light L emitted from the light source 10 is incident on the optical window 23 along the Z direction while being condensed by the lens 70 . The laser light L incident on the optical window 23 passes through the optical window 23 and travels in the internal space V along the Z direction.

The droplet adsorbent 50A differs from the droplet adsorbent 50 of the above-described embodiment in that it has a function as a shielding plate for shielding the droplets S in addition to the function of adsorbing the droplets S. The droplet attracting body 50A is arranged at a position apart from the optical window 23 and the irradiated portion P in the Z direction, and extends along the XY plane so as to block the floating of the droplet S to the optical window 23. there is The droplet adsorbent 50A is held by a holding portion (not shown) provided on the inner surface 22a of the side wall portion 22, for example. In addition, the droplet adsorbent 50A has a through hole 50c penetrating in the Z direction from the surface 50a to the back surface 50b.

The through-hole 50c is provided near the center of the droplet adsorbent 50A, for example, and has a circular shape when viewed from the Z direction. The through hole 50c allows the laser light L, which passes through the optical window 23 and travels along the Z direction, to pass therethrough. The through hole 50c is arranged at the focal position F of the laser light L by the lens 70, for example. Specifically, the through hole 50c is arranged so as to overlap the focal position F when viewed from the X direction and the Y direction. That is, the through hole 50c is arranged so that the focal position F is located inside it (for example, on the central axis). The area of the through-hole 50c seen from the Z direction is smaller than the area of the optical window 23 seen from the Z direction. In this modification, the area of the through-hole 50c seen in the Z direction is smaller than the area of the irradiated portion P seen in the Z direction and slightly larger than the optical path area of the laser light L at the focal position F.

The laser beam L that has entered the internal space V through the optical window 23 passes through the through hole 50c of the droplet adsorbent 50A along the Z direction, and then irradiates the irradiated portion P of the surface 2a. Most of the droplets S of the workpiece 2 generated from the irradiated portion P float in the Z direction. Here, since the area of the through hole 50c is smaller than the area of the optical window 23 as described above, part of the droplets S heading toward the optical window 23 is blocked by the portion of the droplet adsorbent 50A excluding the through hole 50c. It is adsorbed together with the By making the area of the through-hole 50c smaller than the area of the optical window 23 in this way, it is possible to reduce the droplets S directed from the irradiated portion P toward the optical window 23, thereby preventing the droplets S from adhering to the optical window 23. can be effectively suppressed. As a result, continuous irradiation of the laser beam L onto the surface 2a can be realized more reliably, and reduction in compressive residual stress imparted to the surface 2a can be more reliably suppressed.

Furthermore, in the laser processing apparatus 1B, the droplet adsorbent 50A is arranged at the focal position of the laser light L by the lens 70. As shown in FIG. As a result, the area of the through hole 50c through which the laser beam L from the light source 10 passes can be minimized, so that the droplets S traveling from the irradiated portion P to the optical window 23 can be further reduced. Thereby, adhesion of the droplets S to the optical window 23 can be suppressed more effectively. Furthermore, since the droplet attracting body 50A also functions as a shielding plate, the configuration of the laser processing apparatus 1B can be simplified.

In the laser processing apparatus 1B, a droplet adsorber that adsorbs droplets S and a member (shielding plate) having through holes 50c may be provided separately. In this case, the shielding plate has the same shape and arrangement as the droplet adsorbent 50A, while the droplet adsorbent does not have the through holes 50c and includes the same material as the droplet adsorbent 50A. Furthermore, in this case, the droplet attracting body is provided in the internal space V at a position excluding the optical path of the laser light L between the optical window 23 of the lid portion 25B and the irradiated portion P. In addition, the shielding plate may include, for example, the same material as that of the droplet adsorbent 50A. In this case, the shield plate is made of, for example, glass, resin, ceramics, or a metal material such as a pure metal or an alloy.

Further, even when only the shielding plate is provided in the internal space V out of the droplet adsorbing member and the shielding plate, the same effects as in this modified example can be obtained. That is, most of the droplets S generated from the irradiated portion P are shielded by the portion of the shielding plate excluding the through-holes, so that the droplets S can be suppressed from floating on the optical window 23, and the optical window 23 It is possible to suppress the adhesion of droplets S to. As a result, continuous irradiation of the laser beam L onto the surface 2a can be realized more reliably, and reduction in compressive residual stress imparted to the surface 2a can be more reliably suppressed.

FIG. 8 is a diagram showing how a droplet adsorber 50B is attached to the inner surface 25a of the lid portion 25C of the laser processing apparatus according to the third modification. In this modification, the droplet adsorbent 50B is fastened with a plurality of (four in this modification) screws 80 to the inner surface 25a of the lid portion 25C. In this modification, the droplet adsorbent 50B has a plurality of (four in this modification) through-holes 50d penetrating in the Z direction from the front surface 50a to the back surface 50b. , and 26C, it has a plurality of (four in this modification) screw holes 27 respectively corresponding to the plurality of through holes 50d. 50 d of several through-holes are each provided in the four corner|angular parts of the droplet adsorption body 50B, for example. The plurality of screw holes 27 extend from the inner surface 25a in the thickness direction (Z direction) of the lid portion 25C, and are screwed into the plurality of screws 80, respectively.

When attaching the droplet adsorbent 50B to the inner surface 25a, each screw 80 is inserted into each through hole 50d from the front surface 50a side of the droplet adsorbent 50B. screw into. The droplet adsorber 50B is detachably attached to the inner surface 25a by the screwing action of each screw 80 and each screw hole 27. As shown in FIG. Even in such a form, the droplet adsorber 50B that has adsorbed the droplets S in the internal space V can be periodically replaced, and the droplets S can be continuously adsorbed by the droplet adsorber 50B for a long period of time. becomes possible.

FIG. 9 is a diagram showing how a droplet adsorber 50C is attached to the inner surface 25a of the lid portion 25D of the laser processing apparatus according to the fourth modification. In this modification, the droplet adsorbent 50C has a pair of through-holes 50e extending in the Z direction from the front surface 50a to the back surface 50b. has a pair of fittings 28 respectively corresponding to the through holes 50e. The pair of through-holes 50e are arranged, for example, on both sides of the center of the droplet adsorbent 50C in the Y direction. Each through-hole 50e includes a circular hole portion 50g and a hole portion 50f protruding from a portion of the hole portion 50g, and the hole portions 50g and 50f form a keyhole shape as a whole.

Each metal fitting 28 has a round rod-shaped protrusion 28a that protrudes in the Z direction from the inner surface 25a, and a disk-shaped flange that protrudes in the X and Y directions from the tip of the protrusion 28a in the Z direction. 28b. The length of the projecting portion 28a in the Z direction is the same as or slightly longer than the thickness of the droplet adsorbent 50C in the Z direction. The outer diameter of the projecting portion 28a is the same as or slightly smaller than the width of the hole portion 50f in the X direction. The flange portion 28b is provided continuously along the circumferential direction at the distal end portion of the projecting portion 28a, and is arranged coaxially with the projecting portion 28a. The outer diameter of the flange portion 28b is larger than the width in the X direction of the hole portion 50f and smaller than the inner diameter of the hole portion 50g.

When attaching the droplet adsorbent 50C to the inner surface 25a, each metal fitting 28 is attached to the inner surface 25a until the entire flange portion 28b of each metal fitting 28 protrudes from the surface 50a through the hole 50g of each through hole 50e. The through-hole 50e is made to penetrate in a Z direction. Thereafter, by moving the droplet attracting body 50C in the Y direction relative to the lid portion 25D, the projecting portions 28a of the metal fittings 28 are fitted into the hole portions 50f of the through holes 50e. As a result, the flange portion 29 protruding from the surface 50a is caught by the portion around the hole portion 50f of the droplet adsorbent 50C. Thereby, the droplet adsorbent 50C is attached to the inner surface 25a.

When removing the droplet adsorbent 50C from the inner surface 25a, the projecting portion 28a of each metal fitting 28 is removed from the hole portion 50f of each through hole 50e by moving the droplet adsorbent 50C relative to the lid portion 25D in the Y direction. Then, while inserting the flange portion 28b of each metal fitting 28 into the hole portion 50g of each through hole 50e, the droplet adsorbent 50C is separated from the inner surface 25a in the Z direction. Thereby, the droplet adsorbent 50C is removed from the inner surface 25a. Even in such a form, the droplet adsorber 50C that has adsorbed the droplets S in the internal space V can be periodically replaced, and the droplet adsorber 50C can continuously adsorb the droplets S over a long period of time. becomes possible.

Various other modifications are possible for the present invention. For example, the embodiments and modifications described above may be combined with each other according to the desired purpose and effect. Further, in the above-described embodiments, the internal space of the container is maintained in a vacuum state, but the internal space may be depressurized below the atmospheric pressure, and does not need to be maintained in a vacuum state. In the embodiments described above, the light source is arranged outside the container, but it may also be arranged in the interior space of the container. In the above-described embodiments, the container viewed from the Z direction has a rectangular shape, but may have other shapes. For example, the container viewed from the Z direction may have a polygonal shape such as a triangular shape or a pentagonal shape, or may have a circular shape or an elliptical shape.

In the above-described embodiments, the container is arranged so as to be movable relative to the surface of the workpiece, but it may be arranged so as to be immovable relative to the surface of the workpiece. Also, the lid portion of the container may be fixed to the main body portion so as not to be opened and closed. Alternatively, the lid portion of the container may be formed integrally with the body portion. That is, the lid portion of the container may be at least one of the top plate and the side wall portion that constitute a part of the main body portion. In the above-described embodiment, the reflecting surface of the concave mirror reflects the laser beam toward the irradiated portion and converges the laser beam toward the irradiated portion. may In this case, a lens for condensing the laser light may be separately provided on the optical path between the light source and the irradiated portion. This lens may be provided outside the container or may be provided in the interior space of the container.

In the above-described embodiments, the droplet adsorbent is detachably attached to the inner surface of the lid, but it may be fixed to the inner surface of the lid in a non-removable manner, for example, with an adhesive or the like. Also, the droplet adsorbent may be arranged at a position other than the position facing the irradiated portion of the surface in the Z direction. For example, the droplet adsorbent may be arranged on the inner surface of the lid portion other than the portion facing the irradiation portion in the Z direction, or may be arranged on the inner surface of the side wall portion of the container. Also, the droplet adsorber may be made of a material different from the material of the workpiece. Also, the droplet adsorbent may be made of the same material as the container. Also, the droplet adsorbent may be integrated with the container. That is, the droplet adsorbent may be part of the container. In this case, the droplet adsorbent may be, for example, the inner surface of the lid of the container or the inner surface of the side wall of the container.

DESCRIPTION OF SYMBOLS 1, 1A, 1B... Laser processing apparatus, 2... Workpiece, 2a... Surface, 10... Light source, 20, 20A, 20B... Container, 20a... Inner surface, 21... Body part, 21a, 21b... Opening, 22, 22A Side wall portion 22a Inner surface 22c End surface 22d Groove 23 Optical window 25, 25A, 25B, 25C, 25D Lid portion 25a Inner surface 30 Sealing member 31 Lubricant supply pipe , 35... Exhaust mechanism, 36... Exhaust hole, 37... Exhaust pump, 38... Exhaust pipe, 39... Valve, 40... Concave mirror, 40a... Reflective surface, 50, 50A, 50B, 50C... Droplet adsorbent, 50a... Surface, 50b... back surface, 70... lens, L... laser beam, La... part, P... irradiation part, R... region, S... splash, V... internal space.

Claims (12)

A laser processing device that performs processing by irradiating a laser beam onto the surface of a workpiece,
A container defining an interior space with an inner surface and the surface, and maintaining the interior space in a state of reduced pressure below atmospheric pressure,
At least part of an optical path of the laser light between the light source for emitting the laser light and the surface, including a portion irradiated with the laser light on the surface, is located in the internal space;
The internal space is provided with a droplet adsorber that adsorbs droplets of the workpiece generated from the irradiated portion ,
A laser processing apparatus, wherein the droplet adsorbent includes the same material as the material of the workpiece. 2. The laser processing apparatus according to claim 1, wherein said container maintains said internal space in a vacuum state. further comprising the light source;
3. The laser processing apparatus according to claim 1, wherein said light source is a femtosecond laser light source. The laser processing apparatus according to any one of claims 1 to 3 , wherein the container moves relative to the workpiece in a direction along the surface. The light source is arranged outside the container,
5. The laser processing apparatus according to claim 1 , wherein said container has an optical window arranged on said optical path of said laser beam and transmitting said laser beam. the container has a wall extending in a direction intersecting one direction along the surface;
The optical window is provided on the wall,
the laser light enters the optical window along the one direction from the outside of the wall,
6. The laser processing apparatus according to claim 5 , wherein said internal space is provided with a mirror for reflecting said laser beam transmitted through said optical window toward said irradiated portion of said surface. 7. The laser processing apparatus according to claim 6 , wherein said mirror is arranged in a direction inclined from a normal direction of said surface with said irradiated portion as a starting point. The laser processing apparatus according to any one of claims 1 to 7 , wherein the droplet adsorber faces the irradiated portion in the normal direction of the surface. The container has a body portion provided with an opening and a lid portion closing the opening,
The lid includes a part of the inner surface that forms the inner space, and is provided to be openable and closable with respect to the main body,
The laser processing apparatus according to any one of claims 1 to 8 , wherein said droplet adsorber is detachably attached to a portion of said inner surface of said lid. The internal space is provided with a shielding plate that faces the irradiated portion in the normal direction of the surface and shields the droplets,
The optical window is arranged on the opposite side of the shielding plate to the irradiated portion in the normal direction,
A lens is provided on the optical path between the light source and the shielding plate for condensing the laser beam toward the irradiated portion,
The shielding plate includes a through hole that allows the laser beam to pass through,
6. The laser processing apparatus according to claim 5 , wherein an area of said through hole is smaller than an area of said optical window. 11. The laser processing apparatus according to claim 10 , wherein said through-hole is arranged at a focal position of said laser beam by said lens. 12. The laser processing apparatus according to claim 10 , wherein said droplet attracting body is said shielding plate.

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