JP5147445B2 - Laser processing equipment using laser light guided into the jet column - Google Patents

Description

  The present invention relates to a laser processing apparatus using a laser beam guided into a jet liquid column, and in particular, a laser beam guided into a jet liquid column capable of improving the propagation efficiency of the laser beam and ensuring stable processing quality. Relates to a laser processing apparatus.

  2. Description of the Related Art Conventionally, there is known an apparatus for performing plating or etching on a substrate by irradiating laser light into a jet liquid column of an electrolytic solution for plating or etching by using laser light guided by the jet liquid column. . There is also known a treatment apparatus that performs incision of a treatment site with a water jet and laser light by irradiating the water jet with laser light and propagating the laser light by totally reflecting it within the water jet.

As described above, the technology for guiding the laser beam while totally reflecting the laser beam in the liquid column has been applied in various fields. In the laser processing field, the required laser is irradiated by irradiating the laser beam at the same time. With regard to a laser processing apparatus that performs processing, a nozzle block in which a nozzle passage for injecting a liquid column beam (jet liquid column) is formed at the tip of a processing head is provided, and a laser beam is condensed at an entrance opening of the nozzle passage by a focus lens. Thus, there is known one that guides a laser beam to a liquid column beam ejected from a nozzle passage (for example, Patent Document 1).
Conventionally, a laser beam used in a laser processing apparatus is mainly a YAG laser (wavelength 1064 nm), a CO ₂ laser (wavelength 10.6 μm), or the like.

Japanese National Patent Publication No. 10-500903 (FIG. 2)

Here, since the YAG laser (wavelength 1064 nm) and the CO ₂ laser (wavelength 10.6 μm) are easily absorbed by water that is usually used as a jet liquid column, the propagation efficiency of laser light is low. In addition, since the thermal lens action is induced by heat generation when the laser light is absorbed by water, there is a problem that it is difficult to efficiently guide the laser light to the water jet (jet liquid column). Furthermore, when the thermal lens action is induced, the laser light is refracted, and the refracted laser light may hit the nozzle inlet opening and damage the nozzle.
In order to solve this problem, in the laser processing apparatus described in Japanese Patent Laid-Open No. 10-500903 (Patent Document 1), the height of the liquid supply space, which is a water passage that guides water to the nozzle that injects the water jet, is set. By making it low, the distance that the laser beam crosses the water passage is shortened, and the absorption of the laser beam by water is suppressed. In addition, in this apparatus, by reducing the height of the liquid supply space, the flow rate of the water flowing in the liquid supply space is increased, the temperature increase of the water in the liquid supply space that has absorbed the laser light is suppressed, and the heat is reduced. The generation of lenses is suppressed.

  However, when the flow rate of water in the liquid supply space that guides water to the nozzles to suppress the temperature rise is increased, there is a problem that the shape of the water jet tends to fluctuate and the surface of the water jet is disturbed. That is, when the water jet is disturbed, the laser beam guided by the water jet is also affected, so that the processing quality of the laser processing apparatus is degraded. In particular, depending on the material and dimensions of the work piece, the time required for a single processing with a laser processing device becomes very long, so the water jet is required to have high stability so that it will not be disturbed over the entire period. Is done. In addition, if the surface of the water jet is disturbed, the laser beam may jump out of the water jet without being totally reflected at the surface of the water jet, and the propagation efficiency of the laser beam is reduced due to the disturbance of the water jet. There is also a problem.

The present invention has been made in view of such a background, and an object thereof is to provide a laser processing apparatus capable of stably generating a water jet for guiding laser light.
Another object of the present invention is to provide a laser processing apparatus using laser light guided into a jet liquid column that can improve the propagation efficiency of laser light and ensure stable processing quality.

  In order to solve the above problems, an invention according to claim 1 of the present invention includes a laser oscillator that generates laser light, a nozzle that jets a jet liquid to a work, and a liquid supply unit that supplies the jet liquid to the nozzle. And a laminar flow forming channel for supplying the jet liquid to the nozzle in a laminar flow state. The laminar flow forming channel includes a distribution channel formed with a cavity for annularly distributing the jet liquid supplied from the liquid supply means around the nozzle axis, and the distribution on the downstream side in the axial direction of the nozzle. A communication flow path provided in communication with the flow path, a flow path narrower than the distribution flow path and having an annular cavity formed around the axis, and provided adjacent to the upstream side in the axial direction of the nozzle, Stores jet liquid And a liquid storage chamber for supplying to said using a nozzle, the outer peripheral edge of the liquid storage chamber, it is passed through the communication channel and communication over the entire circumference of the ring shape, and wherein.

  According to the first aspect of the present invention, the laminar flow forming flow path for supplying the jet liquid to the nozzle in a laminar flow state is provided, and a stable laminar flow state (a state in which the Reynolds number is small) is created in front of the nozzle. Thus, it is possible to eject the jet liquid column from the nozzle which is less likely to be disturbed on the surface of the jet liquid column and has no fluctuation.

  Specifically, the jet liquid supplied at a high pressure is once distributed annularly around the axis of the nozzle by the distribution flow path. Then, the jet liquid is introduced into the liquid storage chamber in a state where turbulent flow is suppressed by flowing through the communication channel formed in an annular shape with a channel narrower than the distribution channel. Since the flow of the jet liquid introduced into the liquid storage chamber is decelerated here, the Reynolds number of the flow of the jet liquid is reduced, and the jet liquid is guided to the nozzle in a laminar flow state.

  Further, since the outer peripheral edge of the liquid storage chamber communicates with the communication channel over the entire circumference of the ring shape, the liquid storage chamber is uniformly introduced into the outer peripheral edge of the liquid storage chamber from the entire periphery of the communication channel. Thus, the flow velocity of the jet liquid is reduced and stored in the liquid storage chamber in a stable laminar flow state.

  In this way, by providing a laminar flow forming flow path that creates a stable laminar flow state by reducing the flow velocity in front of the nozzle, a stable jet liquid column that does not easily disturb the surface of the jet liquid column and that does not fluctuate. It can spray from a nozzle, and can prevent the fall of processing quality by this. Furthermore, the propagation efficiency of the laser light guided into the jet liquid column can be improved.

The invention according to claim 2 is the laser processing apparatus according to claim 1, wherein the laser light has an absorption coefficient of 0.01 [cm ⁻¹ ] or less when passing through the jet liquid. Features.
The invention according to claim 3 is the laser processing apparatus according to claim 2, wherein the jet liquid is water, and the laser light is a green laser or a UV laser.

  According to such a configuration, the attenuation of the laser beam when passing through the jet liquid can be reduced, so that a sufficiently strong laser beam is introduced into the jet liquid column even when the thickness of the liquid storage chamber is increased. can do. When the jet liquid is water, the laser light is not easily absorbed by water and has a high transmittance, such as a green laser (double wave (SHG) YAG laser, wavelength 532 nm), or UV laser (for example, wavelength 355 nm or 266 nm), the propagation efficiency of laser light can be improved. Further, by using laser light that is difficult to be absorbed by the jet liquid, generation of a thermal lens is suppressed, and it becomes easy to accurately guide the laser light to the inlet opening of the nozzle. For this reason, it is possible to prevent the nozzle from being damaged and to ensure stable processing quality.

  The invention according to claim 4 is the laser processing apparatus according to any one of claims 1 to 3, wherein the jet liquid is water, and the laser beam has a wavelength range of 200 to 700 nm. It is characterized by being.

  According to such a configuration, the attenuation of the laser beam when passing through the water can be reduced, so that a sufficiently strong laser beam can be introduced into the water even when the liquid storage chamber is made thick. it can. Further, by using a laser beam having a wavelength range of 200 to 700 nm that is not easily absorbed by water, generation of a thermal lens is suppressed, and it becomes easy to accurately guide the laser beam to the inlet opening of the nozzle. For this reason, it is possible to prevent the nozzle from being damaged and to ensure stable processing quality.

  The invention according to claim 5 is the laser processing apparatus according to any one of claims 1 to 4, wherein the liquid storage chamber has a depth in the axial direction of the nozzle of 2 mm or more. It is connected to the connecting channel on the upstream side in the axial direction of the outer peripheral edge.

According to such a configuration, the depth of the nozzle in the liquid storage chamber in the axial direction is secured to 2 mm or more, and the flow velocity of the jet liquid is increased by communicating with the communication channel on the upstream side in the axial direction of the outer peripheral edge. The jet liquid is decelerated in the depth direction, and the jet liquid is stored in the liquid storage chamber in a more stable laminar flow state on the upstream side of the nozzle.
For this reason, it is possible to inject a jet liquid column that is less likely to be disturbed on the surface of the jet liquid column and has no fluctuation from the nozzle, and to improve the propagation efficiency of the laser light guided into the jet liquid column.

  In addition, since the depth in the axial direction of the nozzle in the liquid storage chamber is 2 mm or more, the optical system device such as the introduction window and the lens can be isolated from the laser condensing point of the nozzle inlet opening. While avoiding thermal distortion of the apparatus to ensure stable optical performance, durability can be improved and stable processing quality can be ensured.

  The invention according to claim 6 is the laser processing apparatus according to any one of claims 1 to 5, wherein the liquid supply means is configured to transmit the laser light when the jet liquid is water. A processing device for enhancing the homogeneity of the jet liquid as a propagation medium is provided.

According to this configuration, for example, dissolved gas and particles present as impurities in the jet liquid and ions that cause ion emission are removed, and the jet liquid column is homogeneous as glass using a laser light propagation medium. Can increase the sex.
For this reason, the stable jet liquid column can be ejected from the nozzle, and the propagation efficiency of the laser light guided into the jet liquid column can be improved.

  The invention according to claim 7 is the laser processing apparatus according to any one of claims 1 to 6, wherein the laser processing apparatus introduces an assist gas along the jet liquid column. A gas supply chamber provided downstream of the nozzle and configured to accommodate the jet liquid column; and an introduction flow for introducing the assist gas into the gas supply chamber. The introduction flow path is a spiral introduction flow path configured so as to follow a spiral shape from the outer periphery of the jet liquid column, or a cone configured to approach the axis of the jet liquid column It is a shape introduction flow path.

According to this configuration, the assist gas is introduced along the jet liquid column, and the assist gas is guided to the outer periphery of the jet liquid column so that the biased liquid does not act on the jet liquid column, thereby disturbing the surface of the jet liquid column. Therefore, it is possible to eject a jet liquid column that does not easily cause fluctuations from the nozzle, and the propagation efficiency of laser light guided into the jet liquid column can be improved.
Moreover, the workability can be improved by efficiently removing the jet liquid unnecessary at the time of processing accumulated on the workpiece upper surface and the jet liquid rebounding from the work surface.

  The invention according to claim 8 is the laser processing apparatus according to any one of claims 1 to 7, wherein the liquid storage chamber has a volume larger than a volume of a cavity of the communication channel. It is characterized by this.

  According to this configuration, the jet liquid supplied from the cavity of the communication channel flows into the liquid storage chamber having a larger volume. For this reason, the flow velocity of the jet liquid in the liquid storage chamber is reduced, and it becomes easy to create a laminar flow state in the liquid storage chamber, and a stable jet liquid column can be ejected from the nozzle and guided into the jet liquid column. The propagation efficiency of the laser beam can be improved.

  The invention according to claim 9 is the laser processing apparatus according to any one of claims 1 to 8, wherein the jet liquid from the liquid supply means is introduced into the distribution channel. A pipe is connected, and the communicating part of the communication channel with the distribution channel is arranged at a position off the axis of the introduction tube.

  According to such a configuration, since the communication portion of the communication channel with the distribution channel is located away from the axis of the introduction pipe, the jet liquid introduced from the introduction pipe to the distribution channel directly flows into the communication channel. Can be suppressed. For this reason, the jet liquid from the distribution channel can be uniformly supplied to the communication channel from the direction around the axis of the nozzle, and a laminar flow state of the jet liquid in the liquid storage chamber can be easily created.

  The invention according to claim 10 is the laser processing apparatus according to any one of claims 1 to 9, wherein the outer peripheral surface of the communication channel and the outer peripheral surface of the liquid storage chamber have no step. It is characterized by forming a continuous surface.

  According to such a configuration, the jet liquid that moves along the outer peripheral surface of the communication channel moves next along a continuous surface without a step on the outer peripheral surface of the liquid storage chamber, and flows into the liquid storage chamber. For this reason, since the flow of the jet liquid from the communication channel to the liquid storage chamber can be made smooth, it is possible to easily create a laminar flow state of the jet liquid in the liquid storage chamber.

The invention according to claim 11 is the laser processing apparatus according to any one of claims 1 to 10, wherein the liquid storage chamber has a depth in the axial direction of the nozzle of the diameter of the nozzle. It is configured to be 20 times or more.
According to such a configuration, a sufficient flow path area in the liquid storage chamber can be ensured with respect to the jet flow rate of the jet liquid from the nozzle, so that the flow velocity in the liquid storage chamber can be sufficiently slowed, No flow can be generated easily.

  The laser processing apparatus using laser light guided into the jet liquid column according to the present invention can improve the propagation efficiency of laser light and ensure stable processing quality.

A laser beam processing apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings as appropriate.
In the drawings to be referred to, FIG. 1 is a side sectional view showing an overall configuration of a laser processing apparatus according to an embodiment of the present invention. FIG. 2 is an enlarged view of a main part for explaining another example of the optical device according to the embodiment of the present invention, and shows a mode in which a laser light introduction window is not mounted. FIG. 3 is a perspective view showing the shape of the laminar flow forming flow path according to the embodiment of the present invention. 4 is a cross-sectional view taken along the line AA of FIG. 1 showing the configuration of the spiral introduction flow path in the assist gas supply device according to the embodiment of the present invention, and FIG. 5 is a cone according to another example in the assist gas supply device. It is side surface sectional drawing which shows the structure of a shape introduction flow path.

  In addition, although the up-down direction in FIG. 1 is described as the up-down direction of the laser processing apparatus 1 in this embodiment, the direction of the processing head 4 is not limited to the up-down direction, and the processing head 4 is inclined with respect to the up-down direction. You may have done.

  As shown in FIG. 1, a laser processing apparatus 1 according to an embodiment of the present invention includes a green laser oscillator 2 that generates a laser beam L made of a green laser, and a nozzle 3 that injects high-pressure water that is a jet liquid onto a workpiece W. , The optical device 5 for guiding the laser light L to the nozzle 3, the liquid supply means 6 for supplying high-pressure water to the nozzle 3, and the high-pressure water provided adjacent to the upstream side of the nozzle. Is supplied to the nozzle 3 in a laminar flow state, a processing device 9 for enhancing the homogeneity of the jet liquid as a propagation medium of the laser light L, and the assist gas along the jet liquid column F And an assist gas supply device 11 for introducing AS.

  With this configuration, the table T or the processing head 4 is moved by a moving means (not shown) while irradiating the workpiece W with the laser light L guided into the jet liquid column F (water jet) ejected from the nozzle 3. Laser processing.

  The green laser oscillator 2 is a device that generates a green laser as the laser light L, as shown in FIG. Then, the laser light L is guided from the green laser oscillator 2 into the optical fiber cable 21, and condensed from the top of the processing head 4 toward the nozzle 3 disposed below.

The green laser is a double wave (SHG) YAG laser and has a wavelength of 532 nm. Unlike the YAG laser (wavelength 1064 nm) and the CO ₂ laser (wavelength 10.6 μm), the green laser has a characteristic that it easily passes through water. Therefore, when using water that is inexpensive and easily available as a jet liquid, The propagation efficiency of the laser beam L can be improved. Further, since it is difficult to be absorbed by water, it is easy to accurately guide the laser light L to the inlet opening 31 of the nozzle 3 by suppressing the generation of the thermal lens. For this reason, it is possible to prevent the nozzle 3 from being damaged and to ensure stable processing quality.

The processing head 4 includes a housing 41 formed in a substantially cylindrical shape, an optical device 5 accommodated in an upper portion of the housing 41, a laminar flow forming flow path 8 disposed below the optical device 5, a laminar flow A nozzle 3 disposed below the formation flow path 8 and an assist gas supply device 11 disposed below the nozzle 3 are provided.
The laser light L emitted downward from the top of the housing 41 is collected by the optical device 5 into the inlet opening 31 of the nozzle 3 and guided into the jet liquid column F ejected from the nozzle 3. Then, the light is guided to the workpiece W while repeating total reflection in the jet liquid column F, and irradiated onto the workpiece W.

  The optical device 5 includes a collimator lens 51 that converts the laser light L emitted from the top of the housing 41 into parallel light, and a condensing light that condenses the parallel light converted by the collimator lens 51 at the inlet opening 31 of the nozzle 3. A lens 52 and an introduction window 53 that is disposed adjacently above the laminar flow forming channel 8 (liquid storage chamber 83) and introduces the laser light L into the laminar flow forming channel 8 are provided.

  In this embodiment, as shown in FIG. 1, the introduction window (window) 53 for the laser beam L is provided above the liquid storage chamber 83, but the present invention is not limited to this, and is shown in FIG. Instead of the introduction window 53, a condensing lens 52 ′ may be disposed at the position of the introduction window 53 (see FIG. 2).

The liquid supply means 6 includes a high-pressure water pump 61 that sucks water from a water supply tank (not shown) and increases the pressure, and a high-pressure pipe 62 that supplies the increased high-pressure water to the laminar flow forming channel 8.
The high-pressure water pump 61 employs a servo-driven pump, detects the pump discharge pressure, and performs feedback control so that the discharge pressure is constant. It is configured to extrude water.
With this configuration, a stable high-pressure water flow can be generated and sent out to the laminar flow forming channel 8.

The laminar flow forming channel 8 includes a distribution channel 81 in which a cavity for annularly distributing the high-pressure water, which is a jet liquid supplied from the liquid supply means 6, around the nozzle axis G, and the direction of the nozzle axis G. A communication channel 82 provided on the downstream side in communication with the distribution channel 81 and having a narrower channel than the distribution channel 81 and having an annular cavity around the nozzle axis G, and an upstream side in the direction of the nozzle axis G And a liquid storage chamber 83 that stores high-pressure water and supplies the high-pressure water to the nozzle 3.
The communication channel 82 and the liquid storage chamber 83 communicate with each other over the entire circumference of the ring-shaped communication channel 82 at the outer peripheral edge 83 a of the liquid storage chamber 83.

  Here, in the present embodiment, the communication channel 82 is provided in a cylindrical shape in which the upstream side in the direction of the axis G of the nozzle communicates with the distribution channel 81 and the downstream side in the direction of the axis G of the nozzle is smaller in diameter than the upstream side. It is formed as a flow path. On the other hand, the liquid storage chamber 83 is formed in an inverted truncated cone shape in which the downstream side in the direction of the axis G of the nozzle is smaller in diameter than the upstream side.

  And the outer peripheral surface 82a of the communication flow path 82 and the outer peripheral surface 83b of the liquid storage chamber 83 are extended so that there may be no level | step difference and on the same surface. The direction along the outer peripheral surfaces 82a and 83b is inclined inward (nozzle side) with respect to the nozzle axis G direction.

  With this configuration, the high-pressure water stored in the distribution flow path 81 is introduced from the communication flow path 82 so as to be transmitted along the inclination of the outer peripheral surface 83b of the liquid storage chamber 83, whereby the fluid flow is adjusted and the stable laminar flow is achieved. In this state, the liquid is stored in the liquid storage chamber 83 and high-pressure water is supplied to the nozzle 3.

The liquid storage chamber 83 has a depth (height H) in the direction of the nozzle axis G of 3 mm, and communicates with the communication channel 82 on the upstream side of the outer peripheral edge 83a in the direction of the axis G of the nozzle.
The depth (height H) of the nozzle of the liquid storage chamber 83 in the direction of the axis G is preferably 2 mm or more. As will be described later, the velocity of the jet liquid in the liquid storage chamber 83 increases as the depth increases. descend. For this reason, increasing the depth of the liquid storage chamber 83 is advantageous for forming a laminar flow in the upper portion of the nozzle 3 in the liquid storage chamber 83. Further, when the depth of the liquid storage chamber 83 is increased, the laser light before being condensed into a small spot passes through the introduction window 53, so that the energy density of the laser light that passes through the introduction window 53 is reduced, and the introduction window 53 is reduced. Can be protected. Therefore, it is preferable that the depth (height H) of the nozzle of the liquid storage chamber 83 in the axis G direction is appropriately set between 2 and 40 mm in consideration of space restrictions and responsiveness.

[Detailed shape of laminar flow forming channel according to this embodiment]
Next, the preferable shape of the laminar flow formation path 8 according to the present embodiment will be described in more detail.
FIG. 6 is a cross-sectional view along the axis G direction of the laminar flow forming flow path 8 according to the present embodiment. The laminar flow forming channel 8 temporarily retains the high-pressure water supplied from the high-pressure pump in the liquid storage chamber 83 while suppressing generation of vortex and the like to form a laminar flow state, and the surface from the nozzle 3 is not disturbed. It is shaped so that the jet liquid column F can be ejected.

Specifically, as shown in the cross-sectional view of FIG. 6, the distribution flow path 81 of the laminar flow formation flow path 8 includes an outer peripheral side wall surface 114 to which an introduction pipe 112 into which water from a high pressure pump is introduced, It is formed in an annular shape having a substantially rectangular cross section having an inner peripheral side wall surface 116 provided to face the outer peripheral side wall surface 114. The dimension h in the direction along the axis G of the outer peripheral side wall surface 114 is set to be larger than the diameter dimension c of the introduction pipe 112. The introduction pipe 112 is connected on the upstream side in the axis G direction of the outer peripheral side wall surface 114. The inner peripheral side wall surface 116 is disposed so as to intersect the axis M of the introduction pipe 112.
Here, the distribution flow path 81 has a flow rate of water in the distribution flow path 81 such that the water in the distribution flow path 81 is guided to the liquid storage chamber 83 from all directions. A shape having a cross-sectional area that is 2 to 1/10 of the flow rate is preferable.

  The communication channel 82 is disposed such that the upstream communication portion 118 is connected to the downstream side in the axis G direction of the inner peripheral side wall surface 116 of the distribution channel 81. Thereby, the communication part 118 of the communication flow path 82 is disposed at a position deviated from the axis M of the water introduction pipe 112. The communication channel 82 is formed so as to be inclined inward and downstream in the axis G direction from the distribution channel 81 toward the liquid storage chamber 83, and flows between the distribution channel 81 and the liquid storage chamber 83. Form a narrow passage that narrows the path.

The diameter D of the annular end portion on the downstream side of the communication channel 82 is set in consideration of the size of the processing head 4, the capability of the laser processing apparatus 1, and the like, and can be set to 10 mm to 40 mm, for example.
Further, the length p of the communication channel 82 can be appropriately selected according to the shape and size of the processing head 4 and the degree of freedom of space. Since the inner and outer peripheral surfaces of the communication channel 82 have a function of suppressing vortices in the water flow from the distribution channel 81, the length p of the communication channel 82 is set so that the function can be effectively exhibited. Specifically, specifically, it is preferably set to about 1 to 20 times the gap dimension s between the inner and outer peripheral surfaces of the communication channel 82.

  Furthermore, the gap dimension s of the communication channel 82 is constant regardless of the value, provided that the diameter D of the communication channel connected to the liquid storage chamber 83 and the flow rate Q of the liquid flowing out from the nozzle 3 are constant. The Reynolds number does not change. Therefore, the gap dimension s of the communication channel 82 is such that the distribution channel 81 is dimensioned and the pressure of the supplied water is such that water can be introduced into the liquid storage chamber 83 from all directions of the distribution channel 81. These conditions can be set in consideration of the above conditions, and is usually set to 0.3 mm to 2 mm.

  As described above, the depth of the liquid storage chamber 83 in the direction of the axis G is set to be larger than that of the conventional structure described in, for example, the above-described Patent Document 1, and specifically set to 2 mm or more. preferable. Further, the volume of the liquid storage chamber 83 is set to be larger than the volume of the communication channel 82.

  In the laminar flow forming flow path 8 having such a structure, when water is supplied from the introduction pipe 112 by the high pressure pump, the water proceeds toward the inner peripheral side wall surface 116 and reaches the entire circumference of the distribution flow path 81. Here, since the inner peripheral side wall surface 116 is disposed on the axis M of the introduction pipe 112 and the communication channel 82 is not disposed on the axis, water from the high-pressure pump directly enters the communication channel 82. Without being distributed, it is once distributed over the entire circumference of the distribution channel 81. Accordingly, the momentum of the high-pressure water from the introduction pipe 112 is suppressed by the distribution flow path 81.

Water from the distribution channel 81 flows into the communication channel 82 from all directions. The communication flow path 82 suppresses the vortex in the water flow generated by the high pressure pump in the distribution flow path 81 at the inner and outer peripheral surfaces, decelerates the water flow, and makes the liquid storage chamber 83 supply water from all directions. Distribution function.
The water that has flowed into the communication channel 82 flows into the liquid storage chamber 83. As described above, the liquid storage chamber 83 retains water therein, and adjusts the flow rate of the water mainly by the depth to adjust the laminar flow state.
By such an operation, the jet liquid column F ejected from the nozzle 3 is less likely to be disturbed on the surface and does not fluctuate. Therefore, the loss of the propagation efficiency of the laser light L guided by the jet liquid column F is also reduced.

  In addition, as shown in FIG. 5, the nozzle 3 has a disk shape, an inlet opening 31 on which the laser beam L is condensed is formed on the upper surface, and the diameter is gradually increased below the inlet opening 31. A mouth 32 is formed. Then, the laser beam L is guided into the jet liquid column F ejected downward from the ejection port 32 and is ejected onto the workpiece W.

  The treatment device 9 is a device that removes dissolved gas and particles present as impurities in the jet liquid that is water, and ions that cause ion emission. For example, the water treatment device 91 (deaeration device, ion exchange resin) ) Or a high-pressure filter 92.

As shown in FIG. 1, the assist gas supply device 11 includes an air controller 11 a that adjusts the pressure of the assist gas AS, and a gas supply chamber that is provided on the downstream side of the nozzle 3 and accommodates the jet liquid column F. 11b and a spiral introduction flow path 11c for introducing the assist gas AS into the gas supply chamber 11b.
As shown in FIG. 4, the spiral introduction flow path 11 c is introduced at a position shifted with respect to the direction toward the axis of the jet liquid column F, and is introduced so as to follow the spiral shape from the outer periphery of the jet liquid column F. It is a flow path.

  Further, as another embodiment of the introduction flow path, as shown in FIG. 5, it is configured as a cone-shaped introduction flow path 11e configured so as to approach the axis of the jet liquid column F accommodated in the gas supply chamber 11d. You can also. The cone-shaped introduction channel 11e has a distribution channel 11f that distributes the assist gas AS in an annular shape around the gas supply chamber 11d, and the axis of the jet liquid column F extends downward from the distribution channel 11f. The assist gas AS is supplied so as to gradually approach.

The operation and effect of the laser processing apparatus 1 according to this embodiment configured as described above will be described mainly with reference to FIG.
As shown in FIG. 1, the laser processing apparatus 1 is provided with a laminar flow forming flow path 8 for supplying high pressure water to the nozzle 3 in a laminar flow state, and a stable laminar flow state (with a small Reynolds number) in front of the nozzle 3. In this state, the jet liquid column F is ejected from the nozzle 3 so as not to be disturbed on the surface of the jet liquid column F.

  That is, as shown in FIG. 3, the high-pressure water supplied is once distributed annularly around the nozzle axis G by the distribution flow path 81 (flow of R1 to R2). Here, the flow passage cross-sectional area of the distribution flow path 81 is sufficiently larger than the water flow path that guides the high-pressure water to the distribution flow path 81, so the flow rate of the high-pressure water introduced when flowing into the distribution flow path 81 Is sufficiently lowered, and the turbulence of the flow that occurs when flowing into the distribution flow path 81 is removed. Further, the high-pressure water is introduced into the liquid storage chamber 83 in a state in which turbulent flow is suppressed by flowing through the communication channel 82 formed in an annular shape with a channel narrower than the distribution channel 81.

  Further, since the outer peripheral surface 83 b at the outer peripheral edge of the liquid storage chamber 83 is in communication with the communication channel 82 over the entire circumference of the ring shape, the outer peripheral edge of the liquid storage chamber 83 is evenly distributed from the entire periphery of the communication channel 82. (R3 flow). Here, since the height H of the liquid storage chamber 83 is configured to be larger than the height of the communication channel 82, when the liquid storage chamber 83 flows into the liquid storage chamber 83 from the communication channel 82, the channel cross-sectional area of the high-pressure water is wide. Thus, the flow rate of the high-pressure water is reduced and stored in the liquid storage chamber 83 in a stable laminar flow state.

  In this way, by providing the liquid storage chamber 83 that creates a stable laminar flow state in front of the nozzle 3, the jet liquid column F that does not easily disturb the surface of the jet liquid column F and that does not fluctuate is ejected from the nozzle 3. Can do. For this reason, the propagation efficiency of the laser beam L guided into the jet liquid column F can be improved.

[Propagation efficiency of green laser according to this embodiment]
Next, the propagation efficiency of the laser light passing through the liquid storage chamber 83 will be described with reference to FIGS. FIG. 7 is a graph showing the output of laser light emitted when 19 W and 24 W laser light is incident on a liquid storage chamber having various depths (height H, introduction window-nozzle distance). FIG. 8 is a graph showing the propagation efficiency of laser light when the laser light is transmitted through a liquid storage chamber having various depths (height H, introduction window-nozzle distance).

  In FIG. 7, when the nozzle diameter is 100 μm, the injection pressure is 10 MPa, and the frequency of the laser beam L is 10 kHz, the output of the laser beam L (measured at a position 20 mm below the nozzle 3) is taken on the vertical axis, and the horizontal axis The relationship between the two is displayed by taking the distance between the introduction window and the nozzle.

  As shown in FIG. 7, when the distance between the introduction window and the nozzle is 3 mm, when the input is 24 W, an output of about 17.2 W can be obtained, and thereafter, the output gradually increases. Further, when the input is 19 W, an output of about 14.2 W can be obtained, and thereafter, the output gradually increases. As a result, as the distance between the introduction window and the nozzle increases, the laser beam power decreases due to transmission through the liquid even though the distance through which the incident laser beam passes through the entire liquid becomes longer. It shows that it will decrease.

  Here, the output of the laser beam L means the propagation efficiency of the laser beam L propagating through the jet liquid column F. That is, the jet liquid column F indicates the degree of suitability as a laser light propagation medium, and it is recognized that the higher the output of the laser light L, the more stable the jet liquid column F is. In this regard, if a large distance between the introduction window and the nozzle is taken, it is recognized that a stable laminar flow state is formed and the laminar flow state is maintained.

Thus, by ensuring the depth of the nozzle G in the liquid storage chamber 83 in the direction of the axis G of 3 mm, which is 2 mm or more, the flow rate of the high-pressure water is decelerated in the depth direction, and a more stable laminar flow on the upstream side of the nozzle 3 In the state, it is stored in the liquid storage chamber 83.
For this reason, the jet liquid column F that is less likely to be disturbed on the surface of the jet liquid column F and that does not fluctuate can be ejected from the nozzle 3, and the propagation efficiency of the laser light L guided into the jet liquid column F is improved. (See FIG. 7).

Next, the propagation efficiency when a green laser is used as the laser light will be described with reference to FIG.
FIG. 8 is a graph showing the propagation efficiency of the green laser with respect to the distance d from the inlet opening of the nozzle when the green laser is passed through the jet column of water. Here, the output of the green laser was 24 W, the nozzle diameter was 100 μm, and the water pressure was 10 MPa.

  As shown in FIG. 8, the propagation efficiency of the green laser gradually increases as the height H of the liquid storage chamber increases. As described above, when the height H of the liquid storage chamber is increased, the distance that the laser light passes through the liquid is increased, so that the laser light is absorbed by the liquid and the propagation efficiency of the laser light should be reduced. Actually, propagation efficiency increases. This is presumably because the turbulence of the flow in the liquid storage chamber and the jet liquid column is reduced by increasing the height H of the liquid storage chamber. Therefore, when the green laser is used, as shown in FIG. 8, the effect of reducing the flow disturbance is increased and the propagation efficiency is improved until the height H of the liquid storage chamber is about 4 mm. I understand that.

  On the other hand, when the height H of the liquid storage chamber is small, the propagation efficiency of the laser beam is not reduced by the influence of the thermal lens, but by the height H of the liquid storage chamber being reduced, This is probably because the flow upstream of the inlet opening of the nozzle has become unstable. That is, since the height H of the liquid storage chamber is reduced, the flow of water in the region upstream of the inlet opening of the nozzle becomes turbulent, disturbing the jet liquid column and guiding the laser beam well. It is thought that it was because it was not possible.

From the above, when a green laser having a low heat absorption rate with respect to water is used as the laser light, the influence of the thermal lens is very little or almost no influence. Therefore, when laser light having a low absorption rate for water is used, as in the apparatus described in Patent Document 1, the height H of the liquid storage chamber is decreased to increase the flow velocity in the liquid storage chamber, There is no need to suppress the thermal lens. Conversely, by setting the height H of the liquid storage chamber to be large, the flow velocity in the liquid storage chamber is reduced and the flow disturbance in the liquid storage chamber and the jet liquid column is suppressed, thereby improving the propagation efficiency of the laser beam. Can be improved.
As described above, the larger the distance between the introduction window and the nozzle (the height H of the liquid storage chamber), the more advantageous the protection of the introduction window and the laminar flow formation above the nozzle 3 are. In consideration of the properties, it is preferable to set appropriately between 2 and 40 mm and between 20 and 400 times the nozzle diameter in relation to the diameter of the nozzle 3.

  Further, by securing a depth of 2 mm or more in the axial direction of the nozzle 3 in the liquid storage chamber 83 from the laser condensing point of the inlet opening 31 of the nozzle 3 to the introduction window 53 (in the embodiment of FIG. 2) Since the condenser lens 52) can be isolated, it is possible to avoid the thermal distortion of the introduction window 53 and the like to ensure stable optical performance, and to improve durability and ensure stable processing quality. it can.

  In the present embodiment, the depth of the nozzle 3 in the axial direction in the liquid storage chamber 83 is 3 mm. However, in consideration of the nozzle diameter, it may be 20 times or more the nozzle diameter. That is, as the nozzle diameter increases, the flow rate ejected from the nozzle 3 increases, so that the laminar flow state is more easily formed when the depth of the nozzle 3 in the axial direction is increased. For example, if the nozzle diameter is φ150 μm, the depth of the nozzle 3 in the liquid storage chamber 83 in the axial direction is preferably 3 mm or more, for example, 4 to 5 mm.

[Relationship between height of liquid storage chamber according to this embodiment and flow velocity of liquid in liquid storage chamber]
Next, referring to FIG. 9, the laser light is irradiated in the liquid flow path having the conventional structure and the flow velocity in the region peripheral surface where the laser light L is irradiated in the liquid storage chamber 83 according to the present embodiment. Compare the flow velocity at the peripheral surface.

  FIG. 9 is a diagram schematically showing the structure of the liquid storage chamber (liquid supply path) around the nozzle. In FIG. 9, the region U irradiated with the laser light L in the liquid storage chamber 120 is a truncated cone formed between the introduction window 122 and the inlet opening 126 of the nozzle 124. The average flow velocity of the liquid passing through the peripheral surface (side surface) of the truncated cone region U is determined using the liquid storage chamber 83 according to this embodiment and the liquid supply path of the device described in Patent Document 1. Calculate and compare each case.

  Here, in the liquid storage chamber 83 according to the present embodiment, the depth H of the nozzle in the axis G direction is set to H = 2 mm, which is the minimum value of the preferred depth dimension range. In the liquid supply flow path described in Patent Document 1 as a conventional structure, H = 0.5 mm. Other conditions are set to common values. Specifically, water is used as the jet liquid, the nozzle diameter is 150 μm, and the water supply pressure is 80 bar (8 MPa). In addition, the angle θ with respect to the axis of the side surface of the truncated cone region U can be totally reflected in the water column, and is usually used at around 10 ° in order to obtain a light collection diameter smaller than the nozzle diameter. Here, it is set to 10 °.

Under the above conditions, the flow rate Q of water is 1700 mm ³ / s according to the following equation 1.

  Further, the side surface area A of the truncated cone region U is obtained by the following equation 2. Here, r is the circular radius of the top surface of the truncated cone region U, which is equal to the radius of the nozzle, and r = 75 μm. R is the circular radius of the bottom surface of the truncated cone region U, and is obtained by R = H · tan θ. L is the length along the side surface of the truncated cone region U, and is obtained by L = H / cos θ.

  Therefore, since the average flow velocity of the liquid passing through the peripheral surface (side surface) of the truncated cone region U in the liquid storage chamber is calculated by Q / A, the average flow velocity V1 when the liquid storage chamber 83 according to the present embodiment is used. And the ratio R of the average flow velocity V2 of the apparatus described in Patent Document 1 is obtained by the following Equation 3.

From the above formula, when the ratio R is obtained, R = 1 / 10.5. Further, in the liquid storage chamber 83 according to the present embodiment, the average flow velocity is calculated as 623.3 mm / sec, and in the apparatus described in Patent Document 1, the average flow velocity is calculated as 6542 mm / sec. It can be seen that the device has a very slow average flow rate compared to conventional devices.
That is, when the liquid storage chamber 83 according to the present embodiment is used, the flow rate of water in the liquid storage chamber 83 is about 1/10 of the flow rate of water in the liquid supply path of the conventional structure. In addition, if the depth of the liquid storage chamber 83 according to the present embodiment is set to a more preferable 4 mm, the average flow velocity is further reduced, and the average flow velocity ratio R is about 1/38.

  As described above, the depth of the liquid storage chamber 83 in the direction of the axis G is increased, more specifically, 2 mm or more, more preferably 4 mm or more, so that the liquid supply channel of the conventional structure is used. It can be seen that the flow rate of water in the storage chamber 83 can be significantly reduced. Thus, retaining water in the liquid storage chamber 83 to reduce the flow velocity is effective in creating a stable laminar flow state of water before the nozzle 3 as described above.

  That is, in the apparatus described in Patent Document 1, the main point is to suppress the generation of the thermal lens in the truncated cone region U, and the depth of the liquid supply path is set small to increase the flow rate of water in the liquid supply path. It had a structure. For this reason, the water in the liquid supply path tends to be turbulent, and the jet liquid column is disturbed. Therefore, even if the generation of the thermal lens is suppressed, the propagation efficiency of the laser beam cannot be increased so much. On the other hand, in the liquid storage chamber 83 according to the present embodiment, by setting the depth of the liquid storage chamber 83 to be large, water is retained in the liquid storage chamber 83 to reduce the flow velocity, thereby forming a laminar flow state. can do. Thereby, the turbulent jet liquid column F can be formed, and the propagation efficiency of laser light can also be improved.

[Reynolds number of water in the liquid storage chamber according to the present embodiment]
Next, referring to the example of FIG. 9, the Reynolds number of the water in the truncated cone region U in the liquid storage chamber 83 according to the present embodiment and the Reynolds of the water in the truncated cone region U in the liquid supply path according to the conventional structure. Compare the number.
In the schematic diagram shown in FIG. 9 described above, the Reynolds in the case of the structure of the liquid storage chamber 83 according to this embodiment in which the depth H is 2 mm and 4 mm and the apparatus described in Patent Document 1 in which the depth H is 0.5 mm. Calculate the number.

The Reynolds number is expressed by the following equation 4, where V is the average flow velocity, L is the length between the nozzle and the introduction window along the peripheral surface in the truncated cone region U, as shown in FIG. Is the kinematic viscosity of water at 20 ° C. For the average velocity V, a value calculated using Equation 3 is used. In the liquid storage chamber 83 according to the present embodiment, when the depth H = 2 mm, 0.623 m / s, and when the depth H = 4 mm, Is 0.171 m / s, and 6.542 m / s when the depth H of the liquid supply passage having the conventional structure is 0.5 mm. The kinematic viscosity coefficient ν of water is 1.01 × 10 ⁻⁶ m ² / s.

  The Reynolds number Re under each condition obtained by the above calculation was Re = 11252 when the depth H = 2 mm, Re = 688 when the depth H = 4 mm, and 3288 when the depth H = 0.5 mm. . Here, in the structure such as the machining head 4 surrounded by the parallel plane of the nozzle 3 and the introduction window 53, the minimum critical Reynolds number that becomes the boundary between the turbulent flow and the laminar flow is the minimum pipe line in the parallel wall flow. It is considered to be equivalent to the minimum critical Reynolds number, and Re = 1000. Therefore, in the liquid supply path having the conventional structure, the Reynolds number is 3288, which is a numerical value significantly exceeding the minimum critical Reynolds number, and it can be understood that the turbulent flow is easily generated in the liquid supply path.

  Even when the depth H is 2 mm, the Reynolds number Re exceeds the minimum critical Reynolds number. This is a numerical value when the nozzle diameter is 150 μm. When the nozzle diameter is made smaller, the flow rate of the liquid flowing through the nozzle is reduced, so that the Reynolds number Re is also reduced. Therefore, when a nozzle having a smaller diameter is used, it is possible to create a condition that does not cause turbulence even at a depth H = 2 mm. Therefore, the depth dimension depends on a set value such as a nozzle diameter to be used. It is necessary to set appropriately. In this regard, if the depth H is 4 mm or more, the nozzle diameter range that can be used without causing turbulent flow is increased. Therefore, if the depth H is set to 4 mm or more when the liquid storage chamber is designed, processing is performed. Generality can be given by the head.

[Distribution of flow velocity of liquid in liquid storage chamber according to this embodiment]
As described above, in the laser processing apparatus of this embodiment, it can be seen that the average flow velocity in the liquid storage chamber 83 is very slow compared to the apparatus described in Patent Document 1.
Here, the flow rate distribution in the liquid storage chamber 83 according to the present embodiment and the flow rate distribution in the liquid supply path according to the conventional structure are compared in more detail using a fluid simulation by numerical calculation. In addition, the liquid supply path by the conventional structure described in Patent Document 1 has a liquid storage chamber 83 according to this embodiment in that the depth in the axial direction of the nozzle is smaller than that of the liquid storage chamber 83 according to this embodiment. And very different.

  FIG. 10 shows a model 100 of the liquid storage chamber 83 used for calculating the flow velocity distribution in the liquid storage chamber 83 according to the present embodiment. The model 100 is formed in a substantially cylindrical shape having a diameter of 10 mm and a height of 4 mm, and a hole 102 having a diameter of 100 μm corresponding to the nozzle 3 is formed at the center of the bottom surface. The flow velocity distribution simulation was performed under the condition that the fluid uniformly flows from the peripheral surface of the model 100 at a velocity of 6.25 mm / s and flows uniformly from the hole 102 at a velocity of 100 m / s.

  On the other hand, FIG. 11 shows a model 104 of the liquid supply path used for calculating the flow velocity distribution in the liquid supply path of the conventional structure. The model 104 is formed in a substantially cylindrical shape having a diameter of 10 mm and a height of 0.5 mm, and a hole 106 having a diameter of 100 μm corresponding to the nozzle is formed at the center of the bottom surface. In the flow velocity distribution simulation, the inflow velocity from the peripheral surface of the model 104 was set to 50 mm / s so that the outflow velocity of the fluid from the hole 106 was 100 m / s which was the same as the calculation condition in the present embodiment.

  12 and 13 show the simulation results of the flow velocity distribution of water when the model 100 that is the liquid storage chamber according to the present embodiment is used, and FIGS. 14 and 15 show the model 104 that is a model of Patent Document 1. FIG. The simulation result of the flow velocity distribution of water when using is shown. Here, FIG.12 and FIG.14 is the flow-velocity distribution in the cross section along the axis line of the hole of each model. These figures show the flow velocity at each point in the models 100 and 104 by the direction and size of the vector extending from that point, and the larger the vector length, the larger the flow velocity. FIG. 13 and FIG. 15 show the flow lines of the liquid in the liquid storage chamber and the liquid supply space and the distribution of the flow velocity in each part roughly divided for each region having substantially the same flow velocity. 13 and 15, region I represents a region having a flow velocity of about 0.125 m / sec or less, region II represents a region having a flow velocity of about 0.125 to 0.25 m / sec, and region III represents a flow velocity of about 0.25. Represents an area of ~ 0.75 m / sec, area IV represents an area with a flow velocity of about 0.75 to 0.875 m / sec, and area V represents an area with a flow velocity greater than about 0.875 m / sec. . In addition, in FIG. 15, the area | region (area | regions I and II) used as the flow velocity about 0.25 m / sec or less was hardly seen.

As shown in FIGS. 12 and 13, the water in the model 100 according to the present embodiment moves little and has a low flow velocity except in the vicinity of the hole 102. Also, the flow velocity is very small over a wide area above the hole 102.
On the other hand, as shown in FIGS. 14 to 15, in the model 104 which is a model of Patent Document 1, the flow rate of water is larger than that of the model 100 over the entire liquid supply space, and particularly in the upper part of the hole 106. In this region, it is recognized that the flow velocity is very large up to the upper end of the liquid supply space. Further, the water flow moves from the outer peripheral side of the hole 106 toward the center hole 106 in a direction perpendicular to the axial direction of the hole 106, and the direction of the flow is in the axial direction of the hole 106 above the hole 106. It changes rapidly from the vertical direction to the direction along the axial direction.

  From the above, the height of the cylinders of the models 100 and 104, that is, the depth in the direction along the axis G of the nozzle 3 of the liquid storage chamber and the liquid supply space is set as in the liquid storage chamber 83 according to the present embodiment. It can be seen that the flow rate of water in the liquid storage chamber 83 can be made smaller than that in the conventional structure by setting water larger than that in the conventional structure and retaining water in the liquid storage chamber 83. Thereby, a laminar flow state is formed on the upstream side of the nozzle 3 in the liquid storage chamber 83, and the occurrence of turbulence on the surface of the jet liquid column F ejected from the nozzle 3 can be effectively suppressed.

[Distribution of Turbulent Energy of Liquid in Liquid Storage Chamber According to this Embodiment]
Next, the turbulent energy in the liquid storage chamber 83 according to the present embodiment is compared with the turbulent energy in the liquid supply path in the structure described in Patent Document 1. The turbulent energy is an amount calculated by dividing the time average of the square sum of the fluctuation velocity component in each direction of the turbulent flow by 2, and represents the degree of turbulent flow.

Using the models 100 and 104 of FIGS. 10 and 11 described above, the distribution of turbulent energy in a plane perpendicular to the axis of the cylinder at a distance of 0.01 mm from the surface in which the holes 102 and 106 are formed is expressed numerically. Calculation is performed by fluid simulation.
16 schematically shows the simulation result of the turbulent energy distribution of the model 100 corresponding to the liquid storage chamber 83 according to the present embodiment, and FIG. 17 shows the model 104 corresponding to the liquid supply path having the conventional structure. The simulation result of the distribution of turbulent energy is schematically represented. Note that the value of turbulent energy increases in the order of XI, XII, XIII, XIV, and XV.

As shown in FIG. 16, the turbulent energy of the model 100 is uniformly small in most ranges except for the vicinity of the hole 102, and the relatively high part of the turbulent energy in the vicinity of the hole 102 is approximately symmetrical. It is recognized as a circle.
On the other hand, as shown in FIG. 17, the turbulent energy of the model 104 shows higher turbulent energy than that of FIG. 16 in a wide range around the hole 106, and its distribution is asymmetric. This indicates that the flow in the model 104 is not uniform, and non-uniform flow (disturbance) such as entrainment occurs.

From the above, in the model 100 corresponding to the liquid storage chamber 83 according to the present embodiment, the height H of the liquid storage chamber, that is, the depth in the direction along the axis G of the nozzle 3 of the liquid storage chamber 83 is the conventional structure. It can be seen that the liquid flow can be made uniform and less turbulent in the direction perpendicular to the axis G of the liquid storage chamber 83 by setting a larger value.
Further, the maximum value of the turbulent energy in the flow field in the models 100 and 104 shown in FIGS. 10 and 11 is 124 m ² / s ² in the model shown in FIG. 10 and 307 m ² / s in the model shown in FIG. ² . This also shows that the structure of the liquid storage chamber 83 of the present embodiment corresponding to the model 100 can more effectively suppress the occurrence of turbulence than the conventional structure corresponding to the model 104.

[About the movement path of water near the nozzle according to the present embodiment]
Next, the water movement path in the vicinity of the nozzle according to the present embodiment and the water movement path in the vicinity of the conventional structure are compared by experiments.

  In order to actually confirm the simulation results shown in FIGS. 12 to 17, an actual model similar to that shown in FIGS. 10 and 11 is prepared, and water mixed with paint particles is flowed as observation particles. Were each shot with a high-speed video camera. At this time, the diameter of the hole corresponding to the nozzle was 200 μm, the spray pressure of water was 2 MPa, and the particle diameter of the paint particles was 20 to 60 μm. The high-speed video was shot using the Phototron FASTCAM-MAX model 120k with a shooting frame number of 6000 fps in the model of FIG. 10 and a shooting frame number of 4000 fps in the model of FIG.

18 is a diagram schematically showing an image of water movement in the actual model of FIG. 10 corresponding to the structure of the liquid storage chamber 83 of the present embodiment, and FIG. 19 is a conventional liquid supply channel. It is a figure showing the movement of the water in the actual model of FIG. 11 corresponding to the structure of FIG. These drawings show the movement paths of observation particles by superimposing observation particle images taken at different times.
As shown in FIG. 18, in the model corresponding to the structure of the liquid storage chamber 83 of the present embodiment, the observation particle draws a streamline from above the hole 108 along the arrow and moves toward the hole 108. Has moved.
On the other hand, as shown in FIG. 19, in the model corresponding to the conventional structure, the observation particles move around the hole 110 with respect to the hole 110, that is, while causing a vortex.
These coincide with the simulation results shown in FIGS.

  As described above, in the structure of the liquid storage chamber 83 according to this embodiment, the depth along the nozzle axis G direction is set larger than that in the conventional structure, thereby preventing water entrainment and uniform water. It turns out that it can be made to flow into a nozzle by a simple flow.

[Thermal effect of laser light on water according to this embodiment]
Next, using the fundamental wave with a wavelength of 1064 nm used in the apparatus of Patent Document 1 and the second harmonic with a wavelength of 532 nm used in the laser processing apparatus of this embodiment, Explain the thermal effects on water.
First, the IR laser and the green laser are compared with respect to the temperature rise of water due to absorption of laser light.

  FIG. 20A is a diagram schematically showing a region in the vicinity of the nozzle 3. As shown in FIG. 20 (a), the laser beam L travels through the water in the liquid storage chamber 83 through the introduction window 53 while being collected by the condenser lens 52, and is collected at the inlet opening 31 of the nozzle 3. Shine. Therefore, the region N irradiated with the laser light L in the water in the liquid storage chamber 83 has a conical shape. Therefore, the temperature rise of water in this conical region N is calculated.

  FIG. 20B schematically shows a conical region N irradiated with the laser light L. In FIG. 20B, the temperature rise ΔT of the water in the region up to the apex B corresponding to the position of the inlet opening 31 of the nozzle 3 away from the point A at the bottom center of the conical region N by the distance d is expressed by the following equation: 5 is required.

Here, P is the output (W) of the laser beam, α is the absorption coefficient (cm ⁻¹ ) of the laser beam with respect to water, α _FM = 1.44 × 10 ⁻¹ for the IR laser, and α _SHG = 4 for the green laser. .47 × 10 ⁻⁴ . D is the distance from point A (mm), C is the specific heat of water, 4.18 (J / g · K), ρ is the density of water, 1 (g · cm ⁻³ ), J is the nozzle The flow rate of water at a diameter of 150 μm and an injection pressure of about 4 MPa is 1.7 (cm ³ / sec), θ is the angle of the peripheral surface of the conical region N with respect to the axis G, as shown in FIG. = 0.1.

FIG. 21 is a diagram showing the temperature rise ΔT of water due to the absorption of the laser light L with respect to the distance d from point A to B when the output P = 10 (W). As shown in FIG. 21, when the IR laser is irradiated, the temperature of water rises proportionally as the distance d increases, and when the distance d is 4 mm, the temperature rise ΔT is 16.2. It becomes ℃. On the other hand, when the green laser is irradiated, the temperature of water hardly rises even when the distance d increases, and the temperature rise ΔT is 0.05 ° C. even when the distance d is 4 mm. At this time, the refractive index change Δn due to the temperature rise of water is Δn _FM = 1.3 × 10 ⁻³ for the IR laser and Δn _SHG = −4 × 10 ^{−6 for the} green laser. Therefore, it can be seen that when the green laser is used, the refractive index does not change as much as when the IR laser is used, and is hardly affected by the thermal effect on the transmission of the laser light.

  In order to suppress the temperature rise to the same level as that of the green laser by using the IR laser, the distance d from the point A to B needs to be about 13 μm. However, on the other hand, if the distance d from the point A is set to be so small, the flow disturbance in the liquid storage chamber 83 occurs as described above. This also shows that the use of a green laser is advantageous for minimizing thermal effects while enabling the formation of a turbulent jet column.

  From the above, when the green laser is used, even if the distance d is 4 mm, the temperature of the water hardly rises. Therefore, the influence of the thermal lens due to the change in the refractive index of the water accompanying the temperature rise is It is possible to suppress much more than when using. Further, when the green laser is used, since the thermal influence in the conical region N is small, it is not necessary to set a large flow rate of water so as to prevent an increase in the temperature of the water. It becomes possible to reduce the flow velocity of water by setting the depth large. Thereby, the water in the liquid storage chamber 83 can be maintained in a laminar flow state, and the jet liquid column F without any turbulence can be ejected.

Next, the relationship of the amount of change in water temperature with respect to the output when an IR laser and a green laser are used will be described.
FIG. 22 is a diagram showing the relationship between the temperature change amount ΔT of the water in the conical region N with respect to the output P of the IR laser and the green laser when the distance d from the point A to B is set to 4 mm. The nozzle diameter was 150 μm, the injection pressure was 4 MPa, and the condensing angle θ of the laser beam L was 5.7 °. As shown in FIG. 22, when the IR laser is used, the temperature change amount ΔT of the water increases proportionally as the output P of the laser light increases. On the other hand, when the green laser is used, the temperature change ΔT hardly changes even if the output P of the laser beam increases.
From the above, compared to the case of using an IR laser, the use of a green laser suppresses the generation of a thermal lens not only for the distance d but also for the output P of the laser beam. It turns out that it is advantageous.

Next, a first example of the machining head according to the embodiment of the present invention will be described with reference to FIG. FIG. 23 is a sectional side view showing the structure of the machining head according to the first embodiment of the present invention.
In FIG. 23, the same components as those of the machining head 4 according to the above-described embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

As shown in FIG. 23, the machining head 44 according to the first embodiment of the present invention aligns the axial height of the condensing point of the laser light L with the alignment adjusting mechanism 45 that aligns the position of the central axis of the laser light L. An axial adjustment mechanism 46 is provided.
In the processing head 44, the housing 441 that houses the optical device 5 has a bent crank shape, and the nozzle head 442 is attached to the distal end portion of the housing 441 via the axial adjustment mechanism 46. The laser beam L1 emitted downward from the top of the processing head 44 is reflected in the horizontal direction by the beam splitter 511. The laser beam L2 reflected in the horizontal direction is reflected again downward by the beam splitter 512 in parallel with the laser beam L1. The reflected laser light L3 is condensed by the condenser lens 52 at the inlet opening 31 of the nozzle 3.

The beam splitters 511 and 512 have a function of reflecting the laser light L and transmitting visible light other than the vicinity of green. A CCD camera 513 is disposed behind the beam splitter 511 (right side in FIG. 23), and an LED light 514 is disposed as a light source behind the beam splitter 512 (upper side in FIG. 23).
With this configuration, the LED light 514 can irradiate the entrance opening 31 of the nozzle 3 and the CCD camera 513 can confirm the focal position of the laser light L.

The alignment adjustment mechanism 45 includes an adjustment screw 45a disposed at three positions orthogonal to each other on the circumference and a spring 45b that holds the beam splitter 512, and is adjusted by pushing and pulling the adjustment screw 45a. The angle of the beam splitter 512 is configured to be adjustable.
With this configuration, the position of the central axis of the laser light L is adjusted by adjusting the angle of the beam splitter 512 with the adjusting screw 45a while confirming the focal position of the laser light L at the entrance opening 31 of the nozzle 3 with the CCD camera 513. Can be matched to the inlet opening 31 of the nozzle 3.

  The axial adjustment mechanism 46 includes an adjustment nut 46a that is screwed to the tip of the housing 441 and holds the nozzle head 442, a lock nut 46b that is screwed to the tip of the housing 441 and holds the upper side of the adjustment nut 46a, A lock nut 46c that is screwed onto the outer periphery of the adjustment nut 46a and holds the nozzle head 442. The lock nuts 46b and 46c are respectively provided with springs 46d and 46e that are urged in the axial direction to remove backlash. Built in.

  With this configuration, by rotating the adjustment nut 46a with the lock nuts 46b and 46c loosened, the axial position of the nozzle head 442 is adjusted, and the axial height of the condensing point of the laser light L can be easily adjusted. It can be adjusted to the inlet opening 31 of the nozzle 3. Further, the structure can be firmly fixed by the lock nuts 46b and 46c, and the backlash is removed by the springs 46d and 46e, so that the structure is strong against vibration and impact. For this reason, it becomes possible to guide the laser beam L efficiently and stably into the jet liquid column F.

Next, a second example of the machining head according to the embodiment of the present invention will be described with reference to FIG. FIG. 24A is a partial cross-sectional side view showing a configuration around a nozzle in a processing head according to a second embodiment of the present invention, and FIG. 24B shows a case where a sealing member is attached in FIG.
In FIG. 24, the same components as those of the machining head 4 according to the above-described embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

The machining heads 48 and 48 ′ according to the second embodiment of the present invention are provided with a centering mechanism 49 that aligns the center axis of the housing 445 with the axis G of the nozzle.
As shown in FIGS. 24 (a) and 24 (b), the aligning mechanism 49 engages a tapered portion 491 formed on the nozzle side with a tapered portion 492 formed on the housing side. The center axis G of 445 and the axis line G of the nozzle can be automatically aligned. The nozzles 30 and 30 ′ can be fixed to the housings 445 and 446 by screwing the nozzle cap 30 a into the housings 445 and 446.
Further, as shown in FIG. 24 (b), the processing head 48 ′ has an O-ring 32 as a sealing member disposed on the outer peripheral surface of the nozzle 30 ′ to further improve the sealing performance.

With this configuration, the alignment mechanism 49 is provided, so that the nozzles 30 and 30 ′ can be stably held, and the center position and perpendicularity of the nozzles 30 and 30 ′ can be changed each time the nozzles 30 and 30 ′ are replaced. It is possible to solve the problem that the jet liquid column F is not stable due to the deviation.
Further, since the nozzle cap 30a for fixing the nozzles 30 and 30 ′ to the housings 445 and 446 is provided, the replacement work of the nozzles 30 and 30 ′ is facilitated.

  Next, a modification of the laminar flow forming channel according to the present invention will be described with reference to FIGS. FIG. 25 is a perspective view showing the shape of a first modification of the laminar flow forming flow channel according to the present invention, and FIG. 26 is a perspective view showing the shape of the second modification of the laminar flow forming flow channel according to the present invention. FIG. 27 is a perspective view showing the shape of a third modification of the laminar flow forming flow channel according to the present invention.

  First, as shown in FIG. 25, in the laminar flow forming flow path 200 according to the first modified example of the present invention, the inner peripheral wall surface 204 of the distribution flow path 202 is inclined toward the inner side and the downstream side of the axis G. An inclined surface is formed. In addition, the inner peripheral surface 208 of the communication channel 206 also forms an inclined surface that is inclined inward and toward the downstream side of the axis G, and the inner peripheral surface 208 and the inner peripheral side wall surface 204 are continuous. It is the same plane. With the laminar flow forming flow path 200 having such a shape, the high pressure water introduced from the high pressure pump through the introduction pipe 210 is guided by the inclined surface of the inner wall surface 204 and the inclined surface of the communication flow channel 206. It flows into 206. Therefore, the flow of water in the laminar flow forming flow path 200 becomes smooth, and the generation of turbulent flow and vortices can be further suppressed.

  Next, in the second modified example shown in FIG. 26, the outer peripheral surface 224 of the connecting flow path 222 of the laminar flow forming flow path 220 and the outer peripheral face 228 of the liquid storage chamber 226 are curved inwardly in an arc shape. In the second modification, the outer peripheral surface 224 of the communication channel 222 and the outer peripheral surface 228 of the liquid storage chamber 226 form a continuous curved surface. With the laminar flow forming flow path 220 having such a shape, the flow of water from the communication flow path 222 to the liquid storage chamber 226 becomes smooth, and generation of turbulence and vortices can be further suppressed.

Next, in the third modified example shown in FIG. 27, the cross sections of the distribution flow path 242 and the liquid storage chamber 244 of the laminar flow forming flow path 240 are each formed in a substantially rectangular shape. The communication flow path 246 of the laminar flow forming flow path 240 is connected to the axis G so that the inside of the distribution flow path 242 and the downstream side of the axis G communicate with the outside of the liquid storage chamber 244 and the upstream side of the axis G. It is formed along the direction. In the laminar flow forming flow path 240 having such a shape, the water flowing into the distribution flow path 242 hits the inner peripheral side wall surface 248 and spreads over the entire circumference of the distribution flow path 242 and changes its direction to the downstream side in the axis G direction. Then, it proceeds along the inner peripheral side wall surface 248 and flows into the communication channel 246. Water from the communication channel 246 flows along the outer peripheral side wall surface 250 of the liquid storage chamber 244. According to the laminar flow forming channel 240 having such a shape, the water moves along the inner wall surface 248 of the distribution channel 242 and the outer wall surface 250 of the liquid storage chamber 244, thereby suppressing water vortex on the wall surface. can do. This is particularly effective when the communication channel 246 cannot be formed long due to its structure.
The communication channel is not limited to the shape shown in FIG. 3 and FIGS. 25 to 27 described above, and any shape can be used as long as the jet liquid flows into the liquid storage chamber from the entire circumference. .

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and can be implemented with appropriate modifications.
For example, in the present embodiment, a green laser is employed as the laser light L, but the present invention is not limited to this, and a UV laser having a shorter wavelength that is difficult for the laser light L to be absorbed by water can be employed. . Preferably, a laser beam having an absorption coefficient of 0.01 [cm ⁻¹ ] or less when passing through the jet liquid is employed.
In this embodiment, water is used as the jet liquid. However, the present invention is not limited to this, and silicon oil or the like that is difficult to absorb the laser light L can be used as the jet liquid. The laser beam L is not limited to the green laser or the UV laser, and a CO ₂ laser or a YAG laser can be used. However, when water is used as the jet liquid, the laser beam is absorbed by the water. It is preferable to employ a laser that is difficult to be applied. Here, a laser having a wavelength range of 200 to 700 nm is an example of a laser that is not easily absorbed by water. In the case of using a jet liquid in which laser light is hardly absorbed, good propagation efficiency of laser light can be obtained even if a CO ₂ laser or a YAG laser is used.

It is side surface sectional drawing which shows the whole structure of the laser processing apparatus which concerns on embodiment of this invention. It is a principal part enlarged view for demonstrating the other Example of the optical apparatus which concerns on embodiment of this invention, and shows the form which does not mount | wear with the introduction window of a laser beam. It is a perspective view which shows the shape of the laminar flow formation flow path which concerns on embodiment of this invention. It is AA sectional drawing of FIG. 1 which shows the structure of the spiral introduction flow path in the assist gas supply apparatus which concerns on embodiment of this invention. It is side surface sectional drawing which shows the structure of the cone-shaped introduction flow path which concerns on the other Example in an assist gas supply apparatus. It is sectional drawing along the axial direction of the laminar flow formation flow path which concerns on this embodiment. It is a graph which shows the relationship between the depth (height H, introduction window-nozzle distance) of the axis line G direction of a nozzle, and the propagation efficiency of a laser beam. The propagation efficiency of the green laser with respect to the height H of the liquid storage chamber when the green laser is passed through the liquid column beam of water is shown. It is a figure which shows typically the structure of the liquid storage chamber (liquid supply path) in the nozzle periphery which concerns on embodiment of this invention. It is a figure which shows the model of the liquid storage chamber used in order to calculate the flow velocity distribution in the liquid storage chamber which concerns on this embodiment. It is a figure which shows the model of the liquid supply path used in order to calculate the flow velocity distribution in the liquid supply path of the conventional structure. It is the figure which represented the flow velocity in each point in a liquid storage chamber with the vector. It is the figure which divided and represented the space in a liquid storage chamber for every area | region of the substantially same flow velocity. It is the figure which represented the flow velocity in each point in a liquid supply path with the vector. It is the figure which divided and represented the space in a liquid supply path for every area | region of the substantially same flow velocity. It is the figure which represented typically the simulation result of distribution of the turbulent energy of the model corresponding to the liquid storage chamber which concerns on this embodiment. It is the figure which represented typically the simulation result of distribution of the turbulent energy of the model corresponding to the liquid supply path of the conventional structure. It is a schematic diagram showing the movement of the fluid in the model corresponding to the structure of the liquid storage chamber of this embodiment. It is a schematic diagram showing the movement of the fluid in the model corresponding to the structure of the conventional liquid supply path. 3 schematically shows a conical region irradiated with laser light above a nozzle. It is the figure which showed the temperature rise of the water by absorption of a laser beam with respect to the distance from the point A in the case of output P = 10 (W). It is the figure which showed the relationship of the temperature rise (DELTA) T of the water of a cone area with respect to the output P of IR laser and a green laser when the distance d from the point A is set to 4 mm. 1 is a cross-sectional side view illustrating a configuration of a machining head according to a first embodiment of the present invention. (a) is a fragmentary sectional side view which shows the structure around the nozzle in the processing head based on 2nd Example of this invention, (b) shows the case where a sealing member is mounted | worn in (a). It is a perspective view which shows the shape of the 1st modification of the laminar flow formation flow path which concerns on this invention. It is a perspective view which shows the shape of the 2nd modification of the laminar flow formation flow path which concerns on this invention. It is a perspective view which shows the shape of the 3rd modification of the laminar flow formation flow path which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser processing apparatus 2 Green laser oscillator 3 Nozzle 4 Processing head 5 Optical apparatus 6 Liquid supply means 8 Laminar flow formation flow path 9 Processing apparatus 11 Assist gas supply apparatus 11c Spiral introduction flow path 11e Conical introduction flow path 11f Distribution flow path 31 Inlet opening 32 Injecting port 81 Distribution channel 82 Communication channel 83 Liquid storage chamber 83a Outer peripheral edge 91 Water treatment device (treatment device)
92 High pressure filter (processing equipment)
AS assist gas F Jet liquid column L (L1, L2, L3) Laser light W Workpiece

Claims (9)

A laser oscillator for generating laser light; a nozzle for injecting a jet liquid to a workpiece; and a liquid supply means for supplying the jet liquid to the nozzle, and is guided into a jet liquid column ejected from the nozzle. A laser processing device using laser light,
A laminar flow forming channel for supplying the jet liquid to the nozzle in a laminar flow state;
The laminar flow forming channel is a distribution channel in which a cavity for annularly distributing the jet liquid supplied from the liquid supply means around the axis of the nozzle is formed,
A communication channel that is provided in communication with the distribution channel on the downstream side in the axial direction of the nozzle and in which an annular cavity is formed around the axis in a channel narrower than the distribution channel;
A liquid storage chamber provided on the upstream side in the axial direction of the nozzle, storing the jet liquid and supplying the liquid to the nozzle;
Axial depth of the nozzle of the liquid storage chamber, Ri 2~40mm der,
The average flow velocity in the liquid storage chamber is 0.623 m / s or less,
The jet liquid is water, and
The wavelength range of the laser light is 200 to 700 nm,
The laser processing apparatus, wherein an outer peripheral edge portion of the liquid storage chamber communicates with the communication channel over the entire circumference of the ring shape. The laser processing apparatus according to claim 1, wherein the laser beam is a green laser or a UV laser, and has an absorption coefficient of 0.01 [cm ^-1 ] or less when passing through the jet liquid. .   3. The laser processing apparatus according to claim 1, wherein the liquid supply unit includes a processing device for increasing the homogeneity of the jet liquid as the propagation medium of the laser light. The laser processing device has an assist gas supply device introduced along the jet liquid column,
The assist gas supply device includes a gas supply chamber provided on the downstream side of the nozzle and formed to accommodate the jet liquid column, and an introduction flow path for introducing the assist gas into the gas supply chamber,
The introduction flow path is a spiral introduction flow path configured so as to follow a spiral shape from the outer periphery of the jet liquid column, or a conical introduction flow path configured so as to approach the axis of the jet liquid column. The laser processing apparatus according to any one of claims 1 to 3, wherein:   The laser processing apparatus according to any one of claims 1 to 4, wherein the liquid storage chamber has a volume larger than a volume of a cavity of the communication channel.   An introduction pipe into which the jet liquid from the liquid supply means is introduced is connected to the distribution flow path, and a communication portion of the communication flow path with the distribution flow path is located at a position off the axis of the introduction pipe. It arrange | positions, The laser processing apparatus of any one of Claims 1-5 characterized by the above-mentioned.   The laser processing apparatus according to any one of claims 1 to 6, wherein an outer peripheral surface of the communication channel and an outer peripheral surface of the liquid storage chamber form a continuous surface without a step. .   The outer peripheral surface of the communication channel and the outer peripheral surface of the liquid storage chamber form a continuous surface without a step, and the inner peripheral side wall surface of the distribution channel and the inner peripheral surface of the communication channel are the inner side and the axis line. 7. The laser processing apparatus according to claim 1, wherein the laser processing apparatus forms an inclined surface inclined toward the downstream side, and is a continuous same plane.   The outer peripheral surface of the communication channel and the outer peripheral surface of the liquid storage chamber form a continuous surface without a step, and the outer peripheral surface of the communication channel and the outer peripheral surface of the liquid storage chamber are curved in an arc shape inward. The laser processing apparatus according to any one of claims 1 to 6, wherein the laser processing apparatus is provided.