JP2009012061A - Laser-beam working machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser-beam working machine with which a compressed residual stress layer can be formed on the surface of a material to be worked under state of maintaining the precision of the surface roughness even to the material to be worked, having thin thickness while suppressing the removed quantity on the surface of the material to be worked. <P>SOLUTION: The laser beam working machine is provided with a laser-beam source 17 composed of 800 nm wave length, and outgoing 50fs (femto second) pulse width and the laser-beam of 6GM peak output. Further, this laser-beam working machine is provided with articulated arm 15 for displacing the laser-beam gathered on the surface of the material WK to be worked with respect to the material WK to be worked while maintaining the gathering density of 2.5 TW/cm<SP>2</SP>. The laser-beam L emitted from the laser beam source 17 is gathered on the surface of the material W to be worked through working liquid W. In this way, on the surface of the material WK to be worked gathered with the laser beam L, a plasma having the extremely high pressure is intermittently generated for extremely short time. In this result, on the surface of the material WK to be worked, small worked traces of plastically deformed quantity are infinitely formed to form the compressed residual stress layer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a laser processing machine that irradiates a surface of a workpiece with laser light to change the properties of the surface.

  Conventionally, so-called laser peening has been performed in which the surface of a workpiece made of a metal material is irradiated with pulsed laser light to change the property of the surface to improve the state of residual stress. Laser peening is a processing technique that improves the fatigue strength, wear resistance, and stress corrosion resistance of the surface of the workpiece by irradiating the surface of the workpiece with pulsed laser light. Specifically, the tensile residual stress layer is modified into a compressive residual stress layer by making the crystal constituting the surface of the workpiece finer, or plastically deforming the surface, or forming a hardened layer on the surface. The surface has improved fatigue strength, wear resistance and stress corrosion resistance.

In recent years, laser peening using a laser beam having a very short pulse width and a high peak output per pulse has been proposed. For example, Patent Document 1 below discloses a method of laser peening by irradiating a surface of a workpiece with laser light having a pulse width of ps (picoseconds: 10 ⁻¹² sec) under atmospheric pressure or vacuum. ing. Further, in Patent Document 2, laser peening is performed by irradiating a laser beam with a kW class output having a pulse width of fs (femtosecond: 10 ⁻¹⁵ sec) from an angle close to the surface of the workpiece in the atmosphere. A method is disclosed.
JP 2005-131704 A JP 2006-61966 A

However, in the laser peening disclosed in Patent Document 1, that is, laser peening using a laser beam having a pulse width of ps (picoseconds: 10 ⁻¹² sec), the amount of plastic deformation of the surface of the workpiece is increased. In addition, there is a problem that the accuracy of the surface roughness deteriorates due to melting of the surface. Here, the thin workpiece is a workpiece having a thickness of approximately several mm or less. According to the present inventors, it has been difficult to perform laser peening while maintaining the surface roughness of a thin workpiece by simply reducing the output level of laser light.

Further, in the laser peening shown in Patent Document 2, that is, laser peening using a laser beam of kW class output having a pulse width of fs (femtosecond: 10 ⁻¹⁵ sec), the surface of the workpiece is Since the formed compressive residual stress layer is positively removed, the finished dimension of the workpiece after laser peening changes. For this reason, when performing laser peening, it is necessary to perform pre-processing in consideration of a dimensional change of the workpiece, and there is a problem that the work is complicated. Further, a laser peening machine using a high-power laser light source has become a hindrance to the introduction of the laser peening machine because of the large apparatus configuration.

  Therefore, as a result of intensive research, the present inventors have suppressed the removal amount of the surface of the workpiece by laser peening and maintained the surface roughness of the thin workpiece satisfactorily in the same state. The present inventors have found a method capable of forming a compressive residual stress layer by changing the properties of the present invention and have reached the present invention.

  The present invention has been made to address the above problems, and its purpose is to reduce the amount of surface removal of a workpiece by laser peening and to improve surface roughness accuracy even for thin workpieces. An object of the present invention is to provide a laser processing machine capable of forming a compressive residual stress layer on the surface of the workpiece while maintaining the same.

In order to achieve the above object, a feature of the present invention is that in a laser processing apparatus that irradiates a surface of a workpiece with laser light to change the properties of the surface, laser light having a wavelength of not less than the visible region and not more than the near infrared region. A laser light source that emits light with a pulse width of fs (femtosecond: 10 ⁻¹⁵ sec), a condensing optical system that condenses the laser light emitted from the laser light source toward the surface of the workpiece, and the workpiece A transparent object that is disposed in contact with a portion where the laser beam is collected on the surface of the laser beam, and a transparent object that can transmit the laser beam, and a collection density of the laser beam on the surface of the workpiece are set to a predetermined density. Displacement means for displacing the laser beam condensed by the optical optical system relative to the workpiece is provided.

In this case, for example, the laser light source emits a laser beam having a pulse width of several fs or more and several hundred fs or less, and a peak output per pulse of several hundred MW or more and several hundreds GW or less. The density of the laser beam focused on the surface of the workpiece may be several hundred GW / cm ² or more and several hundred TW / cm ² . The condensing optical system may condense laser light from a direction substantially perpendicular to the surface of the workpiece. Further, the transparent object may be glass, for example. In this case, instead of the glass, for example, the laser processing apparatus further includes a processing liquid supply means for causing a liquid to exist in a portion where the laser beam on the surface of the workpiece is condensed, The liquid supplied by the processing liquid supply means may be used. In this case, the transparent liquid may be water, for example.

  According to the feature of the present invention configured as described above, the surface of the workpiece is irradiated with a laser beam having a pulse width of fs (femtosecond) through the transparent liquid object at a predetermined concentration. For this reason, extremely high pressure plasma is intermittently generated in a very short time in the portion irradiated with the laser beam on the surface of the workpiece. As a result, innumerable processing traces having a small amount of plastic deformation as compared with the prior art are formed on the surface of the workpiece, and a compressive residual stress layer having a thickness of several μm to several tens of μm is formed. As a result, the compressive residual stress layer can be formed in a state in which the accuracy of the surface roughness is maintained even for a workpiece having a thin thickness of several mm or less.

  Hereinafter, a laser beam machine according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram schematically showing the configuration of a laser beam machine according to the present invention. FIG. 1 schematically shows the configuration of the laser processing machine according to the present invention, and in order to facilitate understanding of the present invention, each component or the relationship between components is exaggerated as appropriate. ing. This laser processing machine is an apparatus that improves the fatigue strength, wear resistance, and stress corrosion resistance of the surface by forming a compressive residual stress layer by irradiating the surface of the workpiece WK with a pulsed laser beam. is there.

  The laser processing machine includes a processing tank 11. The processing tank 11 is a container for storing the processing liquid W when processing the workpiece WK, and is formed in a box shape having an open upper surface. A water supply / drainage pump 13 is connected to the lower part of one side surface (the left side surface in the drawing) of the processing tank 11 via a water supply / drainage pipe 12. The water supply / drainage pump 13 is controlled by a controller 20 described later to supply the processing liquid W from a processing liquid tank (not shown) into the processing tank 11 and drain the processing liquid W from the processing tank 11 to the processing liquid tank. The electric pump is connected to a power source (not shown). The processing liquid W supplied and discharged to the processing tank 11 is so-called ion-exchanged water obtained by removing ionic components from water, and is colorless and transparent. That is, the processing tank 11 corresponds to the processing liquid supply means according to the present invention, and the processing liquid W corresponds to the transparent object according to the present invention.

  A support table 14 for supporting the workpiece WK is provided at the bottom of the processing tank 11. The support table 14 is configured such that a flat plate-like upper plate 14 b is supported in a horizontal state on four leg portions 14 a provided in an upright state on the bottom of the processing tank 11. Among these, the upper plate 11b is a table for fixing the workpiece WK. A laser beam emission nozzle 16 is provided above the processing tank 11 while being supported by the articulated arm 15. The articulated arm 15 is a so-called vertical articulated robot configured with a displacement mechanism capable of three-dimensionally displacing the laser beam emitting nozzle 16 held at the tip of the arm. The operation of the displacement mechanism of the articulated arm 15 is controlled by an articulated arm control circuit 23 described later. That is, the multi-joint arm 15 and the multi-joint arm control circuit 23 correspond to the displacement means according to the present invention.

The laser beam emitting nozzle 16 collects laser light emitted from the laser light source 17 and guided through the pulse compressor 18 and the optical transmission cable 19 on the surface of the workpiece WK placed on the support table 14. It is an optical component provided with a condensing lens (not shown) capable of condensing at a density. In the present embodiment, an objective lens capable of condensing laser light on the surface of the workpiece WK with a condensing density of 2.5 TW / cm ² is used. That is, the laser beam emitting nozzle 16 corresponds to the condensing optical system according to the present invention. The laser light source 17 is a laser beam having a wavelength (λ) in the near-infrared region of 800 nm with a pulse width of fs (femtosecond: 10 ⁻¹⁵ sec) and a peak output per pulse in the range of several hundred MW to several hundred GW. It is an optical component composed of a laser medium to be emitted (for example, titanium sapphire crystal). The operation of the laser light source 17 is controlled by a laser drive circuit 22 described later. In the present embodiment, the laser light source 17 having an average output of 1 W is used.

  The pulse compressor 18 is a dispersion compensator for compensating for the extension of the pulse width due to dispersion of the laser light emitted from the laser light source 17. Specifically, in order to prevent the laser light emitted from the laser light source 17 from being dispersed mainly when passing through the machining liquid W and extending the pulse width, the pulse width of the laser light is made shorter in advance. To compensate. The optical transmission cable 19 is a cable for guiding the laser light emitted from the laser light source 17 to the laser light emitting nozzle 16, and the pulse width does not increase even if the laser light having a pulse width of fs (femtosecond) is transmitted. An optical fiber is used. Specifically, a metal film and a dielectric film are formed inside a hollow quartz glass tube, and air is used as a core.

  The laser processing machine includes a controller 20. The controller 20 includes a CPU, a ROM, a RAM, and the like, and controls the operations of the laser drive circuit 22 and the articulated arm control circuit 23 according to instructions from the input device 21. The input device 21 includes a plurality of push button switches, receives an input operation from an operator, and outputs a signal corresponding to the input operation to the controller 20. The laser drive circuit 22 controls the operation of the laser light source 17 in accordance with an instruction from the controller 20. The articulated arm control circuit 23 is a circuit that controls the operation of the displacement mechanism built in the articulated arm 15 in accordance with an instruction from the controller 20. A display device 24 is connected to the controller 20. The display device 24 is configured by a liquid crystal display, and displays information such as an operation state of the controller 20 and a processing result by the controller 20.

  Next, the operation of the laser beam machine configured as described above will be described. In the present embodiment, a workpiece WK is formed by forming an aluminum material into a flat plate shape having a thickness of 1 mm. First, the operator sets the workpiece WK on the support table 14. Specifically, the operator places the workpiece WK on the support table 14 in the machining tank 11 into which the machining liquid W has not been introduced and fixes the workpiece WK with a predetermined fixture. In this case, the operator sets the work surface of the workpiece WK on the support table 14 with the work surface facing upward. Then, the operator turns on a power switch (not shown) in the laser processing machine. As a result, the controller 20 enters a standby state waiting for an instruction input from the operator.

Next, the operator operates the input device 21 to instruct the controller 20 to introduce the machining liquid W into the machining tank 11. In response to this instruction, the controller 20 operates the water supply / drainage pump 13 to absorb the processing liquid W from a processing liquid tank (not shown) and introduce it into the processing tank 11. In this case, the controller 20 introduces the processing liquid W to such an extent that the workpiece WK in the processing tank 11 is completely immersed. Next, the operator operates the input device 21 and instructs the controller 20 to start processing on the workpiece WK. Specifically, the operator operates the input device 21 to input information such as a processing start position, a processing range, and processing conditions on the workpiece WK to the controller 20. Here, the processing conditions are the pulse width, peak output, condensing density at the condensing point, repetition frequency, and coverage of the laser light applied to the workpiece WK. In the present embodiment, the pulse width is 50 fs (femtosecond), the peak output per pulse is 6 GW, the condensing density is 2.5 TW / cm ² , and the repetition frequency is 1 kHz. The coverage is the number of irradiation laser spots per unit area, and is 500 spots / mm ² in this embodiment.

In response to this instruction, the controller 20 outputs information related to the position and orientation of the laser beam emitting nozzle 16 held by the articulated arm 15 to the articulated arm control circuit 23. Thereby, the articulated arm control circuit 23 controls the operation of the displacement mechanism built in the articulated arm 15 to position the laser beam emitting nozzle 16 at a predetermined position and orientation. In this case, the multi-joint arm 15 is positioned at a position where the concentration of the laser beam focused on the surface of the workpiece WK is 2.5 TW / cm ² (on the surface of the workpiece WK and the laser beam emitting nozzle 16). The laser beam emission nozzle 16 is positioned at a distance from the built-in objective lens.

Further, in this case, the laser light emitting nozzle 16 is positioned so that the portion from which the laser light is emitted (the tip portion of the laser light emitting nozzle 16) is positioned in the processing liquid W. This is because when the tip of the laser beam emitting nozzle 16 is located outside the processing liquid W, the emitted laser light is refracted on the surface of the processing liquid W, and the laser beam is reflected and the traveling direction is shifted. . Further, the laser beam emission nozzle 16 is positioned at a position where the concentration of the laser beam condensed on the surface of the workpiece WK is 2.5 TW / cm ² (on the surface of the workpiece WK and the laser beam emission nozzle 16). It is positioned at a distance from the built-in objective lens. The laser beam emitting nozzle 16 is positioned so that the optical axis of the laser beam guided to the surface of the workpiece WK is orthogonal to the surface of the workpiece WK. The optical axis is positioned with a slight inclination with respect to the surface of the workpiece WK. This is to prevent the laser light reflected by the workpiece WK from entering the laser light emitting nozzle 16 again and being guided to the laser light source 17 and damaging the laser light source 17.

Next, the controller 20 emits laser light L from the laser light source 17 via the laser drive circuit 22. As a result, the laser light L emitted from the laser light source 17 passes through the pulse compressor 18, the optical transmission cable 19, and the laser light emission nozzle 16 on the surface of the workpiece WK with a predetermined concentration density (2.5 TW / cm). ² ). The laser beam L condensed on the surface of the workpiece WK instantaneously ionizes and evaporates atoms in the extreme surface layer portion of the workpiece WK, and the laser beam L on the surface of the workpiece WK is condensed. Plasma P is generated in the part (this phenomenon is called “ablation”).

  In this case, the pressure in the plasma P reaches a very high state, specifically, about several hundred MPa to several hundred GPa because the volume expansion of the generated plasma P is suppressed by the inertial force of the machining liquid W. Thereby, the surface of the workpiece WK is plastically deformed by the pressure of the plasma P. That is, compressive residual stress is applied to the surface of the workpiece WK. On the other hand, since the laser beam L is irradiated with a pulse width of fs (femtosecond) for a very short time, the plasma P generated on the workpiece WK is also intermittently generated with a very short duration. For this reason, a plurality of machining traces having a very small range and depth of plastic deformation are formed on the surface of the workpiece WK.

  However, in this processing by ablation, since the output of the laser light source 17 is small and the laser beam L is irradiated substantially perpendicular to the surface of the workpiece, the surface of the workpiece WK is removed by ablation. The amount is small compared to the prior art. That is, in the laser processing machine according to the present invention, although a part of the surface of the workpiece WK is removed, the tensile residual stress layer on the surface of the workpiece WK is positively removed as in the prior art. The tensile residual stress layer on the surface of the workpiece WK is modified to a compressive residual stress layer.

  Then, the controller 20 controls the operation of the articulated arm 15 through the articulated arm control circuit 23 in a state where the surface of the workpiece WK is irradiated with the laser light L, whereby the laser light emitting nozzle 16 (laser light The displacement of L) is started. In this case, the controller 20 controls the operation of the articulated arm 15 so that the laser light irradiation nozzle 16, that is, the laser light L is displaced at a speed corresponding to the coverage. Thereby, the laser beam L condensed on the surface of the workpiece WK is continuously displaced on the surface of the workpiece WK at a speed corresponding to the coverage. In the process of displacement of the laser beam L, the controller 20 displaces the laser beam irradiation nozzle 16 so that the light spots formed on the surface of the workpiece WK overlap each other so that an unirradiated region by the laser beam L does not occur. To. Thereby, a compressive residual stress layer having a thickness of about 20 μm is formed on the surface of the workpiece WK through which the laser beam L has passed.

  When the controller 20 irradiates the entire region of the processing range instructed by the operator with the laser light L, the controller 20 stops the emission of the laser light L from the laser light source 17 and sets the laser light irradiation nozzle 16 to a predetermined value. Retreat to the standby position. Thereby, a compressive residual stress layer is formed in a uniform state on the entire surface within the processing range on the surface of the workpiece WK. On the other hand, when the laser beam irradiation nozzle 16 is retracted to a predetermined standby position, the operator operates the input device 21 to instruct the controller 20 to discharge the processing liquid W in the processing tank 11. In response to this instruction, the controller 20 controls the operation of the water supply / drainage pump 13 to discharge the machining liquid W in the machining tank 11 to a machining liquid tank (not shown). Then, the operator releases the chuck by the support table 14 and removes the workpiece WK. Thereby, the peening process of the workpiece WK is completed.

As can be understood from the above operation description, according to the above embodiment, a laser beam having a pulse width of 50 fs (femtosecond), a peak output per pulse of 6 GW, and a condensing density of 2.5 TW / cm ² is processed. The surface of the workpiece WK is irradiated through the liquid W. For this reason, extremely high pressure plasma P is intermittently generated in a very short time in the portion irradiated with the laser beam on the surface of the workpiece WK. As a result, innumerable machining traces having a smaller amount of plastic deformation than the prior art are formed on the surface of the workpiece WK, and a compressive residual stress layer having a thickness of about 20 μm is formed. As a result, a compression residual stress layer is formed in a state in which the surface roughness accuracy is maintained even for a workpiece WK having a thin thickness of about 1 mm while suppressing the amount of removal of the surface of the workpiece WK by laser peening. can do.

  Furthermore, in carrying out the present invention, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the object of the present invention.

In the above embodiment, the output condition of the laser light L emitted from the laser light source 17 is set such that the pulse width is 50 fs (femtosecond), the peak output per pulse is 6 GW, and the surface of the workpiece WK is set. The condensing density of the focused laser beam was 2.5 TW / cm ² . However, the output conditions of the laser light emitted from the laser light source 17 and the condensing density of the laser light condensed on the surface of the workpiece WK are formed on the type and shape of the workpiece WK and the workpiece WK. It is set as appropriate according to the thickness of the compressive residual stress layer to be performed, and is not limited to the above embodiment. According to the inventors of the present invention, the pulse width is several fs or more and several hundred fs or less, the peak output per pulse is several hundred MW or more and several hundred GW or less, and the light collection density is several TW / cm ² or more. Further, it has been found that the laser beam L under the condition of several tens of TW / cm ² or less is suitable. According to this, it is possible to form a compressive residual stress layer of approximately several μm to several tens of μm while suppressing the amount of removal of the surface of the workpiece WK by laser peening. Therefore, the present invention can be widely applied to fields in which a compression residual stress layer having a thickness of several μm to several tens of μm is required regardless of the thickness of the workpiece.

  In the present embodiment, the laser light L having a wavelength in the near-infrared region of 800 nm is used. However, the laser light is not limited to this as long as the laser light has a wavelength capable of transmitting the machining liquid W. That is, a laser beam having a wavelength in the near infrared (about 800 to about 2500 nm) may be used, or a laser beam having a wavelength in the visible wavelength range (about 400 to about 800 nm) may be used. Also by these, the same effect as the above embodiment can be expected.

  In the present embodiment, the size of the light spot of the laser beam L formed on the surface of the workpiece WK is constant, but the present invention is not limited to this. That is, the size of the light spot of the laser beam L formed on the surface of the workpiece WK may be changed in the displacement process of the laser beam L focused on the surface of the workpiece WK. . According to this, the rate at which the light spots formed on the surface of the workpiece WK overlap each other increases, and an unirradiated region due to the laser light L on the surface of the workpiece WK is less likely to occur. As a result, a uniform compressive residual stress layer can be formed on the surface of the workpiece WK with high accuracy.

  In the above embodiment, an aluminum material having a thickness of 1 mm is used as the workpiece WK. However, the workpiece WK is not limited to this as long as it can be plastically deformed. For example, an iron-based material, a non-ferrous material such as gold, silver, copper, or stainless steel, a resin material, or the like may be used as the workpiece WK. Further, since the plastic deformation is performed by the plasma P at an extremely high pressure, the compressive residual stress layer can be formed on a material having high hardness, for example, a material subjected to heat treatment such as cemented carbide, die steel, or quenching. Further, the thickness of the workpiece WK is not limited to the above embodiment, and can be widely applied to members having a thickness required to form a compression residual stress layer of several μm to several tens of μm.

  However, the present invention is particularly effective for the workpiece WK having a small thickness. Specifically, it is possible to form a compressive residual stress layer in a state in which the accuracy of the surface roughness is maintained for the workpiece WK having a thickness of 0.1 mm to several mm. Therefore, the present invention is particularly effective when a compressive residual stress layer is formed on a thin member / part. For example, components / parts such as micromachines or MEMS (Micro Electro Mechanical System), tips of injection needles and blades of surgical blades, leaf springs with a thickness of several millimeters, coil springs with a diameter of several millimeters or less, and fuel cells A compressive residual stress layer can be formed on each surface of a separator or the like, and the fatigue strength, wear resistance, and stress corrosion resistance properties of each surface can be improved.

  Moreover, in the said embodiment, it comprised so that a laser beam might be irradiated from the substantially perpendicular | vertical direction with respect to the surface of the workpiece WK. This is to give substantially uniform energy to the portion irradiated with the laser beam. In other words, when the laser beam is irradiated from a direction nearly parallel to the surface of the workpiece WK, the energy density in the portion irradiated with the laser beam becomes uneven, and the generation state of the plasma P becomes unstable. For this reason, it is preferable to irradiate a laser beam from a substantially perpendicular direction with respect to the surface of the workpiece WK. According to the present inventors, it is preferable to irradiate the surface of the workpiece WK with a laser beam from a substantially vertical direction. However, the laser beam is emitted from an angle of ± 45 ° with respect to the vertical direction. A compression residual stress layer can be formed even by irradiation.

  In the present embodiment, as described above, positioning is performed in a state where the optical axis of the laser beam is slightly inclined with respect to the surface of the workpiece WK. However, it is not always necessary to tilt the optical axis of the laser light as long as the reflected light may return toward the laser light source 17.

  Moreover, in the said embodiment, the laser light source 17 was comprised using the laser medium which consists of a titanium sapphire crystal. However, the laser light source is not limited to this as long as it can emit the laser light L having a pulse width of fs (femtosecond). For example, a laser light source using glass or crystals containing neodymium ions or ytterbium ions, or free electrons as a laser medium may be used. In addition, a YAG laser, a semiconductor laser, a copper vapor laser, an excimer laser, or the like can be used. Also by these, the same effect as the above embodiment can be expected.

  Moreover, in the said embodiment, the optical transmission cable 19 was comprised with the optical fiber. However, the present invention is not limited to this as long as the laser light L having a pulse width of fs (femtosecond) emitted from the laser light source 17 can be accurately transmitted. For example, the laser light L emitted from the laser light source 17 may be guided to the laser light irradiation nozzle 16 through a plurality of reflection mirrors. Also by this, the same effect as the above-mentioned embodiment can be expected.

  In the above embodiment, the pulse compressor 18 is used to compensate for the pulse width of the laser light emitted from the laser light source 17. However, when it is not necessary to compensate for the pulse width of the laser light emitted from the laser light source 17, the pulse compressor 18 is naturally unnecessary. Further, unlike the present embodiment, it is not necessary to provide the laser light source 17 and the pulse compressor 18 separately, and the laser light source 17 having the function of the pulse compressor 18 may be used. Also by these, the same effect as the above embodiment can be expected.

  Moreover, in the said embodiment, it was set as the structure which displaces the laser beam emitting nozzle 16, ie, the laser beam L, with respect to the workpiece WK by the multi-joint arm 15. However, the present invention is limited to this as long as the workpiece WK can be displaced with respect to the laser light L irradiated onto the workpiece WK while setting the laser beam condensing density on the surface of the workpiece WK to a predetermined density. It is not a thing. That is, the position of the workpiece WK may be displaced with respect to the laser light irradiation nozzle 16 (laser light L) while the position of the laser light irradiation nozzle 16 (laser light L) is fixed. Also by this, the same effect as the above-mentioned embodiment can be expected.

  In the above embodiment, ion-exchanged water is used as the processing liquid W. However, the laser light L guided to the workpiece WK can be transmitted, and the pressure in the plasma P is promoted and the plasma P is increased. However, the present invention is not limited to this as long as it is a transparent object that does not react such as ignition or explosion due to the occurrence of. For example, nonflammable or flame retardant oil can be used as the processing liquid W. Moreover, you may use objects other than a liquid. For example, a glass plate may be disposed in a portion of the workpiece WK that is irradiated with the laser light L, and the laser light may be irradiated through the glass plate. According to these, the compressive residual stress layer can be formed on the workpiece WK that dislikes water or the workpiece WK that dislikes liquid, and the scope of application of the present invention can be further expanded.

  Further, in the above embodiment, by storing the machining liquid W in the machining tank 11 in which the workpiece WK is set, the surface of the workpiece WK is irradiated with the laser light via the machining liquid W. Configured. However, the configuration is not limited to this as long as the machining liquid W exists on the surface of the workpiece WK irradiated with the laser light L. For example, the processing liquid W may be partially supplied (for example, sprayed) to the surface of the workpiece WK irradiated with the laser light L. According to this, the compression residual stress layer can be formed even on the workpiece WK that is difficult or inappropriate to be immersed in the processing liquid W in the processing tank 11, and the scope of application of the present invention is assured. It can be further expanded.

1 is a schematic configuration diagram schematically showing an overall configuration of a laser beam machine according to an embodiment of the present invention.

Explanation of symbols

WK ... workpiece, W ... working fluid, 11 ... processing tank, 12 ... water supply / drain pipe, 13 ... water supply / drainage pump, 14 ... support table, 15 ... articulated arm, 16 ... laser light irradiation nozzle, 17 ... laser light source, 18 DESCRIPTION OF SYMBOLS ... Pulse compressor, 19 ... Optical transmission cable, 20 ... Controller, 21 ... Input device, 22 ... Laser drive circuit, 23 ... Articulated arm control circuit, 24 ... Display device.

Claims (6)

In a laser processing apparatus that changes the properties of the surface by irradiating the surface of the workpiece with laser light,
A laser light source that emits a laser beam having a wavelength not less than the visible region and not more than the near infrared region with a pulse width of fs (femtosecond: 10 ⁻¹⁵ sec);
A condensing optical system for condensing laser light emitted from the laser light source toward the surface of the workpiece;
A transparent object that is disposed in contact with a portion where the laser beam is collected on the surface of the workpiece, and is capable of transmitting the laser beam;
Displacement means for displacing the laser beam condensed by the condensing optical system relative to the workpiece while setting the concentration of the laser beam on the surface of the workpiece to a predetermined density A laser processing machine comprising: In the laser beam machine according to claim 1,
The laser light source emits laser light having a pulse width of several fs or more and several hundred fs or less, and a peak output per pulse of several hundred MW or more and several hundred GW or less,
It said displacement means, the laser processing machine to a condenser density several hundred GW / cm ² or more and several hundred TW / cm ² the laser beam is focused on the surface of the workpiece. In the laser beam machine according to claim 1 or 2,
The condensing optical system is a laser processing machine that condenses the laser light from a direction substantially perpendicular to the surface of the workpiece. The laser processing apparatus according to any one of claims 1 to 3, further comprising:
A processing liquid supply means for causing a liquid to exist in a portion where the laser beam is condensed on the surface of the workpiece;
The laser processing machine, wherein the transparent object is a liquid supplied by the processing liquid supply means. In the laser beam machine according to claim 4,
The laser processing machine, wherein the liquid is water. In the laser beam machine according to any one of claims 1 to 3,
The transparent object is a laser processing machine in which glass is glass.

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