JP2000170473A - Laser drilling method for ceramic structural body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress vibration and noise to the minimum extent and form a large and deep hole in a ceramic structural body by irradiating the ceramic structural body with laser beams obliquely and upward to drill the structural body. SOLUTION: Since laser beams 29 are applied obliquely and upward to a ceramic structural body, for example, a rock bed part 2, a hole 3 formed in the ceramic structural body 2 on the side close to an opening part is positioned at a lower position so that melted dross 35 of a ceramic substance caused due to irradiation of the laser beams 29 flows down toward the opening part 36 by its self-weight. As a result, since an innermost part (the deepest part or hole tip) of a hole 3 to be drilled in succession is exposed to the laser beams 29 over substantially whole diameter of the hole 3, it is possible to progress hole drilling surely. A part of a rock formation substance heated by the laser beam 29 is evaporated and is dissipated as an evaporated substance 39. Consequently, it is possible to drill a deep hole which has a large diameter and makes it difficult to neglect a flow of dross.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drilling method using a laser beam, and more particularly, to a laser drilling method for a ceramic structure.

[0002]

2. Description of the Related Art When there is a risk of rocks and rocks falling in an area adjacent to a road, a public structure, a private house, or the like, in order to safely remove the rocks and rocks in advance, a rock drill or the like is conventionally used. A mechanical construction method is used.

[0003]

However, mechanical methods involve impacts and the like, so that not only is it difficult to avoid noise, but also unknown cracks and the like in rocks increase due to vibrations caused by impacts such as impacts. Unintentional collapse or collapse may occur. Further, in the mechanical construction method, a large-scale device and a heavy object are indispensable for applying and supporting a load such as cutting and hitting, but it is difficult to transport the equipment to a high place such as a cliff. In the mechanical construction method, it is necessary to apply a mechanical load in contact with a rock, a rock, or the like, which is likely to fall, so that a person is forced to approach a place close to a dangerous place.

[0004] In order to avoid vibration and noise caused by a mechanical construction method, it has also been proposed to conduct high-power laser light to an excavation site with an optical fiber and perform excavation using thermal energy by the laser light (particularly). JP-A-9-242453).

However, this proposal is limited to the idea of using laser light from a high-power laser oscillator such as an iodine laser. That is, when the present inventors irradiate the rock surface with a high-power laser beam to pierce the rock, depending on the direction, the molten dross resulting from the melting of the rock in the pierced portion is deposited and solidified to form a glass dross. Thus, it was found that it is practically not easy to prevent the laser beam from being irradiated into the hole and efficiently drill a large and deep hole.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to provide a laser of a ceramic structure capable of forming a large and deep hole in the ceramic structure while minimizing vibration and noise. It is to provide a perforation method.

[0007]

In order to achieve the above object, a laser drilling method for a ceramic structure according to the present invention irradiates a laser beam obliquely upward on a ceramic structure to drill the ceramic structure. Consisting of

In the laser drilling method according to the present invention, the laser beam is radiated obliquely upward to the ceramic structure, so that the hole formed in the ceramic structure is located closer to the opening, so that the laser beam is located lower. The molten dross of the ceramic substance generated by the irradiation of the material may flow down toward the opening by its own weight. As a result, drilling (perforation) continues
Since the innermost part (the deepest part or the tip of the hole) of the hole to be formed can be exposed to the laser beam over almost the entire diameter of the hole, the drilling can be reliably advanced. Therefore, a large-diameter hole that is difficult to ignore the dross flow can be drilled deeply.

[0009] In the perforation method of the present invention, the ceramic material is melted by heat using the energy of the laser beam.
Perforation is performed by flowing, evaporating and dispersing, so it is essentially non-contact, does not actually generate noise or vibration, and supports the mechanical processing load unlike the mechanical construction method There is no need for heavy objects.

In this specification, a "ceramic structure" is a part of a natural structure such as a rock on a mountain surface (or a rock) or a rock (or a rock) forming a rock wall. Includes both objects (rocks) and man-made concrete structures, such as concrete columns and piers, used in seismic retrofitting of buildings. Here, the “concrete structure” includes a composite material such as so-called reinforced concrete or a mixture of different materials. In this specification, “rock”, “rock” and “rock” are used almost synonymously in the sense that they include huge stones, but depending on the context,
“Rock” refers to something larger than “rock”, and “rock” refers to something larger than “rock”. When referred to collectively, it is mainly referred to as "rock."

In the case where the ceramic structure is made of rock constituting a natural structure, it is often difficult to accurately detect the existence and distribution of cracks inside the rock. Since no cracks are given, there is no risk of spreading the cracks, and there is little risk of accidental collapse. Further, since the thermal conductivity of the ceramic material constituting the rock is low, the heating of the perforated portion by the laser beam becomes local heating, and the perforated portion can be perforated without generating new thermal stress in a peripheral portion away from the perforated portion.

When the ceramic structure is a structure made of a composite material such as reinforced concrete, when piercing a portion such as a reinforcing bar, if desired, the beam diameter is reduced by melting, or the beam is irradiated while blowing oxygen gas. May be performed to oxidize and cut or melt.

The oscillator of the laser beam to be irradiated on the ceramic structure has a high output, for example, an output (or an average output).
Is preferably capable of generating a laser beam on the order of kilowatts (kW) or more, and includes, for example, a YAG laser device or a carbon dioxide gas laser device. Note that an iodine laser device may be used. As long as the (average) output is of the kW class, a type that generates a continuous wave or a type that generates a pulse may be used. Depending on the type of ceramic material, a beam diameter of 1
In the case of about 0 to 20 mm, the output is typically 2
３3 kW or more, preferably 4 kW or more, more preferably 5 kW or more. From the viewpoint of easiness in transmitting a beam to a high place, a YAG laser capable of transmitting a beam using a glass fiber or the like is more preferable than a long-wavelength laser such as a carbon dioxide laser.

[0014] Preferably, the beam is a parallel ray or a near parallel ray. In this specification, “parallel rays” or “quasi-parallel rays” are collectively referred to as “substantially” parallel rays. "Pseudo-parallel rays" are typically
It consists of a convergent beam focused by a long focus lens. The term “long focal length” means that the focal length is sufficiently long as compared with a hole to be formed by drilling (for example, 15 to 20 cm). For example, the focal length is 2-3 times the depth of the hole. It means that it is at least twice, preferably at least 5 to 10 times. One reason for using substantially parallel rays as the beam is that when the ceramic structure to be irradiated is a natural rock or the like, its surface has considerable irregularities. That is, temporarily
When trying to focus the beam to a very small spot diameter, the allowable range in the depth direction becomes short, and if there is unevenness on the surface, the spot-shaped focusing part may shift from the surface, making it difficult to control the beam diameter on the surface. There is. On the other hand, by using a long focal length lens, the depth of focus is increased, and the lens is less affected by surface irregularities. Therefore, it is preferred that the beam not be of an overly convergent (focused) type. In addition, the surface of the ceramic structure to be irradiated with the laser beam (the innermost portion of the hole being drilled) withdraws as the drilling proceeds, so that the laser structure is covered from a laser light emitting housing such as a laser torch. In order to eliminate the need for adjusting the distance to the irradiation surface, the beam is preferably a substantially parallel light beam.
In addition, since the laser beam has high directivity, the distance between the beam exit housing and the ceramic structure can be greatly increased by bringing the beam closer to a parallel beam, and work can be performed even when an unexpected collapse of rock or the like occurs during drilling. There is little risk that the user or equipment will be damaged.

Under conditions where the dross does not impede the irradiation of the beam, that is to say when the entire beam cross-section is substantially evenly illuminated at the deepest part of the hole being drilled, the holes formed in the ceramic structure Is typically about the same as the beam diameter, and the depth of the hole formed by drilling depends on the energy density of the beam (beam output / beam cross-sectional area) and the irradiation time. The beam output is the beam energy per unit time. Therefore, for example, when it is desired to pierce with a hole diameter of about 10 to 20 mm, the beam diameter is also set to be about 10 to 20 mm on the irradiated surface. In the case of a quasi-parallel beam, a long focal length lens is selected so that the beam diameter on the surface to be illuminated matches the desired hole diameter. The beam diameter may be selected according to the application (diameter of the hole or the material of the ceramic structure), and may be, for example, smaller than 10 mm or conversely larger than 20 mm.

The upward tilt or elevation of the beam is such that the molten dross resulting from the melting of the ceramic material can flow under gravity to the opening side under its own weight so that the molten dross does not practically impede further drilling. The size can be any size (any number of times) in principle. The ease with which the molten dross flows out depends on the viscosity and density (specific gravity) of the molten dross and may depend on the type and temperature of the ceramic material (usually a mixture but may be a single material). Assuming that the elevation angle is taken numerically, it is typically 2 to 3 degrees or more, preferably about 5 degrees or more. For the flow of molten dross, a larger elevation angle is preferable, but the distance (depth) measured from the surface of the ceramic structure to the bottom of the hole in a direction perpendicular to the surface of the structure is sufficiently deep in a short time. In order to achieve this, it is preferable that the elevation angle is not so large, for example, about 45 degrees or less, and more preferably, for example, about 30 degrees.
It is less than degree.

In order to monitor the progress of perforation, it is preferable that imaging means such as a CCD camera be provided as a monitoring means in the laser light emitting housing.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment in which the laser drilling method according to the present invention is applied to the removal of a rock, a rock or a rock which may collapse will be described with reference to the accompanying drawings.

In FIG. 1, 1 is a mountain, and it is assumed that the mountain 1 has a rock part 2 which may collapse. In order to remove the rock part 2 before the collapse accident occurs, holes 3 (for example, having a diameter of about 2 cm and a depth of 10 to 20 c
m), the pores 3 are filled with a swelling agent that expands due to a chemical reaction, and the swelling force of the swelling agent cracks the rock part 2 around the holes 3 to form a rock or rock 4 of an appropriate size. Split and drop. In addition, in order to crack the rock part 2, instead of generating an expanding force chemically by an expanding agent, an expanding force may be physically generated by driving something like an arrow.

In the present invention, the hole 3 is opened by a laser beam. The laser beam oscillation equipment 10 has a vehicle 11 equipped with a laser-related device and a vehicle 12 equipped with a power supply device, which are arranged at a sufficient distance 6 from a collapse risk area 5 at the foot of the mountain 1. The vehicle 11 with a laser-related device is equipped with a laser oscillator 13 such as a YAG laser oscillator, a laser control panel 14 for controlling the laser oscillation of the oscillator 13, an air conditioner 15 around the oscillator 13, and the like. 12
A generator 16, a laser power supply 17 that receives electric energy from the generator 16 and supplies power to the oscillator 13,
Laser cooling water machine (chiller) that cools the oscillation section 3
18 etc. are mounted. The YAG laser oscillator 13
For example, it is composed of a continuous wave (CW) oscillator having an output of about 4 kW. The oscillator 13 includes a beam output monitor (not shown) that monitors the output of a beam emitted from the main body of the oscillator 13. A plurality of oscillators 13 and the like may be arranged in parallel.

At a height 7 near the rock mass 2 on the middle of the mountain 1,
An aerial work platform 19 is provided. The work cart 19 is
The crane unit 20 includes a crane unit 20 that is hydraulically controlled.
An electric / hydraulic control type or an electric control type articulated small robot 21 is attached to the tip of the robot. The small robot 21 is an aerial work platform 19
(Altitude) 7 may be remote-controlled, but preferably, the beam-related control is performed at the laser-related device-equipped vehicle 11 (at the foot of the vehicle) so that the beam output can be controlled simultaneously or in parallel. (Safety area) 6. A laser torch 23 for shaping and emitting a laser beam sent from the laser oscillator 13 via the optical fiber 22 is attached to the tip of the arm of the small robot 21, and the laser beam from the laser torch 23 is attached to the tip of the laser torch 23. A CCD camera 24 for monitoring the drilling operation by the camera is mounted.

Instead of arranging the high work cart 19 at the high place 7, a high place such as a work tower is assembled in the high place 7 or the safe area 6 at the foot of the vehicle, and the work is carried out along the stand. The small robot 21 having a high degree of freedom may be raised, and the robot 21 may support the laser torch 23 and the CCD camera 24 on the torch 23 to control the attitude of the torch 23. When a substantially parallel beam is used as the laser beam, the beam diameter of the laser beam emitted from the laser torch 23 can be kept within a predetermined range even if the horizontal distance from the torch 23 to the perforated portion 3 is considerably large.

An image of the perforated portion, that is, the hole 3 and its surroundings captured by the CCD camera 24 are displayed on a monitor display (not shown), and based on the display, the perforated portion (where the hole is to be formed) 3 is displayed. In order to irradiate the beam with a predetermined elevation angle, the attitude of the small robot 21, more specifically, the position and inclination of the laser torch 23 are controlled, and the beam output obtained by the beam output monitor unit of the oscillator 13 is controlled by the laser control panel 14. And a drilling operation is performed to open a hole 3 having a predetermined diameter and a predetermined depth. If desired, the attitude of the small robot 21 may be directly controlled based on image data captured by the CCD camera 24.

As shown in FIG. 2, for example, the laser torch 23 includes a collimating lens 26 having a short focal length for converting light from the emission end 25 of the optical fiber 22 into a parallel beam having a beam diameter corresponding to a desired hole diameter. Focal length is 1m, for example
An emission housing 28 having a focusing lens (condensing lens) 27 of about 10 m or more,
A laser beam 29 in the form of quasi-parallel light is emitted from the laser beam emission housing 28. In order to make the beam parallel, other optical components such as a compound lens may be used instead of a single convex lens. If desired, the beam is once made parallel by the lens 26 and then slightly turned by the lens 27. Instead of focusing, the beam may be converted to a quasi-parallel ray by a single lens or a compound lens. Further, instead of turning the beam into a quasi-parallel beam, the beam may be irradiated to the perforated portion of the bedrock 2 as it is. In order to adjust the beam diameter, for example, the focal length of the lens 26 may be changed, or another means such as an aperture means may be used.

In the above, one laser oscillator 13
Although the example using the laser beam from the above has been described, a plurality of laser oscillators 13 are provided.
The laser beams from the laser beams 3 are transmitted to the laser torch
The laser beam from the plurality of optical fibers 22, 22,... Is synthesized as shown by the imaginary line in FIG. 2 at the incidence part 30 of the laser torch 23, that is, the incidence part 30 of the laser emission housing 28, as a whole. A higher output laser beam 29 may be emitted and irradiated (the fiber 22
Is one, the input part 30 is the output end 25 of the fiber 22.
Matches). In this case, the housing 28 functions as a laser light combining housing. It should be noted that the beams are combined at the output portion of the optical fiber 22 (the input portion 3 of the laser torch 23)
Instead of performing the process at 0), the process may be performed at the entrance of the optical fiber 22. When a plurality of laser oscillators 13 are provided, the laser oscillators 13 may be oscillators having different characteristics or different types of lasers, if desired.

Next, the significance of inclining the irradiation beam 29 by the elevation angle α will be described with reference to FIG.
A description will be given based on (a) and (b).

When the irradiation beam 29 irradiates the rock part 2, the irradiation melts the rock material in the perforated part 3. When the depth of the hole 3 of the perforated portion is shallow, the molten rock material, that is, the molten dross 35 flows out of the opening 36 of the hole 3 by its own weight, and is cooled and hardened near the opening 36. However, as shown in FIG. 5A, when the irradiation beam is composed of a substantially horizontal beam 29a and the hole 3a formed by the irradiation beam 29a extends horizontally, if the hole 3a becomes deep, the molten dross It takes time for the 35 to flow to the opening 36. Therefore, the molten dross 35
5, the energy of the laser beam 29 is easily consumed for heating the retained molten dross, the beam energy is difficult to be efficiently used for drilling, and the drilling speed is apt to decrease. (Note that the fact that a part of the beam 29 is reflected on the surface of the dross (not shown) such as the lower edge of the opening 36 and does not enter the hole 3 also leads to a loss of beam energy). Further, among the molten dross 35 at the back of the hole 3, those that can quickly flow out of the opening 36 are limited to those located at a position higher than the bottom wall on the side close to the opening, and therefore, FIG. As schematically shown in FIG.
It gets thinner. As a result, there are surfaces on which it is difficult to form deep holes.

On the other hand, as shown in FIG. 5B, when the irradiation beam 29 irradiates the rock part 2 upward at the elevation angle α, the molten dross 35 generated by the irradiation Since it can flow out of the opening 36 along the bottom 37 which is formed in accordance with the generation of the dross and is inclined higher in the depth (lower in the opening 36), the hole 3
Is easily formed deep with a large diameter corresponding to the beam diameter D. Note that, in this example, the case where the beam 29 is substantially a parallel ray is described. Therefore, although the inclination angle of the beam center axis is evaluated as the elevation angle α, the range in which the beam 29 can be regarded as a quasi-parallel ray is described. In the case of a beam that is convergent to some extent, the lower edge of the beam that defines the bottom of the hole 3 may be inclined with an elevation angle α.
The elevation angle α may be evaluated not at the beam center axis but at the lower edge of the beam. The description here is limited mainly to the behavior of the dross inside the hole 3 formed by the perforation.

More specifically, as shown in FIG. 3, the hole 3 is formed by the irradiation of the laser beam 29 to the rock or the drilled portion of the bedrock portion 2 and flows along the bottom 37 of the hole 3. The molten layer, that is, the molten dross layer 35 is gradually deposited and solidified to finally become a solid glass dross layer 35, and the molten dross or the outflowed molten layer 38 flowing out from the opening 36 is solidified while being deposited and finally solidified. It becomes the outflow glass dross 38. A part of the rock forming substance heated by the laser beam 29 evaporates and evaporates 39
Dissipated as On the other hand, a glass dross layer 35 similar to the bottom glass dross layer 35 is formed on the inner wall on the upper side of the hole 3 although the thickness is small. Remains. That is, the hole 3 whose inner wall is covered with the glass dross layers 35 and 38 is
9 formed by perforation. Therefore, it is sufficient to fill the hole 3 with an expanding agent and break and remove the portion of the bedrock 2 adjacent to the hole 3. In FIG. 1, reference numeral 31 denotes a vehicle for removing rocks 4 that have been broken down to a transportable size and dropped.

[0030]

Next, embodiments of the present invention will be described.
In the following example, a continuous wave YAG laser beam from a high-power YAG laser device was used as a laser beam, and a water-cooled crushed rock block in Hokkaido was used as a ceramic structure.

[0031]

Embodiment 1 A laser beam from a continuous wave YAG laser device having an output of 4 kW is converted into a beam having a beam diameter of 20 mm and a substantially parallel light beam by a laser light emitting housing as shown in FIG. The surface of the block was irradiated at an elevation angle of about 5 degrees. The result is shown by a diamond and a curve 41 in FIG. Similarly, set the beam diameter to 10 mm
In FIG. 4, an example of perforation when the irradiation was performed for about 1.5 minutes is indicated by a triangle. In addition, a continuous wave YAG with an output of 4 kW
Laser light from laser device and continuous wave YAG with 2kW output
The laser beam from the laser device is combined at the incident end 30 in FIG. 2 and made incident on the laser light combining housing 23 to form a beam 29 having an output of 6 kW as a whole. The results obtained are shown by a square and a curve 42.

As can be seen from the curve indicated by reference numeral 41 in FIG. 4, in this case, the irradiation time is 2 to 10 minutes, and the depth is 100 to 100.
Perforations could be made up to about 180 mm. Therefore, it was confirmed that according to the method of the present invention, if the power was 4 kW, a hole having a size normally necessary for filling the expanding agent could be formed.
The output was 4 kW and the beam diameter was 10 mm and 20 mm.
It can be seen from the time required to drill a hole having a depth d of 100 mm in the case of (1) that the drilling speed can be increased by narrowing the diameter of the beam 29 and increasing the energy density (output per unit area) of the beam 29. Furthermore, from the curves 41 and 42,
The same can be confirmed, and it can be seen that the energy density of the beam 29 can be controlled to control the depth d of the hole to be drilled at a desired time. Further, from the curves 41 and 42 in FIG. 4, the depth (hole depth) d of the hole 3 increases with the elapse of the irradiation time t. Therefore, the depth d of the hole can be controlled by controlling the irradiation time t.
Can be controlled. One of the reasons why the slope of the curve 41 decreases as the irradiation time t increases is that the deeper the hole, the lower the ratio of the portion of the heat input by the laser beam directly used for perforation. it is conceivable that.

[0033]

Comparative Example 1 Example 1 was repeated except that the beam axis was horizontal using a beam exit housing having a focal length of 200 mm, and a convergent divergent beam (the beam diameter was 20 mm or 10 mm at the irradiated portion) was irradiated. When the average output of the beam 29 was 500 W, the irradiated part of the water-cooled crushed rock melted, but the molten dross did not flow out and, in practice, the hole could not be deeply drilled. Thus, in the case of water-cooled crushed rock or many other similarly-composed rocks based on silicon dioxide, the power of the laser light is sufficiently greater than 500 W to perforate holes of the order of 10 mm. You need to do that.

[0034]

Embodiment 2 A beam of 4 kW output was irradiated at an elevation angle of 5 ° of the main axis of the beam, and the focal point of the beam (therefore, the laser emission housing) was advanced toward the perforation at 20 mm / min for the first 5 minutes. Drilling was performed in the same manner as in Comparative Example 1 except that the hole was kept still and maintained for the next 5 minutes, and a hole having a depth d of about 140 mm was formed. The reason why the hole depth d was lower than in the case of Example 1 is that the narrowed part of the beam was located near the opening of the hole, so that the molten dross flowing out near the opening had a laser dross. It is considered that because the light was not irradiated, it was rapidly cooled and deposited, and the discharge of the molten dross was hindered.
On the other hand, since the beam diameter of the quasi-parallel beam or the parallel light beam is not small even near the opening, it is considered that cooling and solidification (deposition) of the molten dross near the opening can be minimized.

In the above, an example in which the present invention is applied to perforation for preventing rock collapse beforehand has been described. It can also be used for perforating composite materials based on ceramic materials, such as the removal of reinforced concrete columns. The iron part in the concrete is irradiated with a beam whose energy density is increased by narrowing the beam diameter as necessary, or as necessary, by blowing oxygen to promote oxidation. It may be melted or cut.

If desired, a high-power laser beam is irradiated on a relatively dense rock such as granite to heat and melt the material to form a hole. Cracks may be generated in the holes. In this case, the crushing of the dense rock can be controlled efficiently. Similarly, it is possible not only to perforate by melting / evaporation accompanying heating, but also to cause local thermal deterioration in the ceramic structure relatively deep (to the depth region of the hole) by local heating.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing an example in which a method of the present invention is applied to rock fall prevention as a preferred embodiment of a method for perforating a ceramic structure according to the present invention.

FIG. 2 is an explanatory view schematically showing how a laser beam is irradiated by the laser torch of FIG. 1;

FIG. 3 is an explanatory diagram specifically showing a state of perforation by laser beam irradiation in FIG. 1;

4 is a graph summarizing the experimental results of Example 1 by the method shown in FIG. 3, in which the horizontal axis represents the irradiation time t, and the vertical axis represents the depth d of a hole (hole) formed by laser drilling.

5A and 5B are schematic explanatory views for explaining the role of the elevation angle in laser beam irradiation in FIG. 3; FIG. 5A is an example of horizontal (zero elevation angle) irradiation for comparison; Is an example of irradiation with an elevation angle.

[Explanation of symbols]

1 Mountain 2 Rock mass 3 Hole (hole), perforated portion 3a Hole (hole) 4 Rock (rock) 5 Collapse accident danger area at foot 6 Safe place away from collapse accident danger area (Laser oscillation equipment installation location) 7 High Place 10 Laser beam oscillation equipment 11 Car equipped with laser related equipment 12 Car equipped with power supply device 13 Laser oscillator 14 Laser control panel 15 Air conditioning equipment 16 Generator 17 Laser power supply 18 Laser water chiller (chiller) 19 High work platform 20 Crane unit DESCRIPTION OF SYMBOLS 21 Small robot 22 Optical fiber 23 Laser torch 24 CCD camera 25 Emission end (Emission end) 26 Collimating lens 27 Focus lens (Condensing lens) 28 Laser light emission housing (Laser light synthesis housing) 29 High output laser beam 30 Incident part 35 Melting Dross (solid glass dross layer) 35a solid glass dross 36 Opening 37 Bottom 38 Outflowing molten layer 39 Evaporate 41 Irradiation time vs. hole depth relation curve (output 4 kW) 42 Irradiation time vs. hole depth relation curve (output 6 kW) d Hole depth (hole depth) t Irradiation time α Elevation angle of laser beam

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Mitamura 3-1-1-18, Hachiken 9-Johigashi, Nishi-ku, Sapporo, Hokkaido No. (72) Inventor Hisashi Konno 2-6-1, Nakanoshima, Toyohira-ku, Sapporo, Hokkaido, Japan (72) Inventor Kyo Sato, 2-3-6-7, Sumikawa, Minami-ku, Sapporo, Hokkaido, Japan Saiyu-so (72) Inventor, Mitsuru Yoshikawa 63-30 Yuyogaoka, Hiratsuka-shi, Kanagawa Prefecture, Sumitomo Heavy Industries Machinery Co., Ltd. Hiratsuka Works (72) Inventor Takashi Kurosawa 63-30 Yuyogaoka, Hiratsuka, Kanagawa Prefecture Sumitomo Heavy Industries Machinery Co., Ltd. Hiratsuka Plant F-term (reference) 4E068 AF01 CA09 DB12

Claims (4)

[Claims] 1. A laser drilling method for a ceramic structure, comprising irradiating a laser beam obliquely upward to the ceramic structure to bore the structure. 2. The method according to claim 1, wherein the laser beam applied to the ceramic structure is a substantially parallel beam. 3. The perforation method according to claim 1, wherein the elevation angle of the laser beam irradiation is about 5 degrees or more. 4. The perforation method according to claim 1, wherein the ceramic structure is a rock or a concrete structure.