JP7040033B2 - Laser device and internal combustion engine - Google Patents

Description

The present invention relates to a laser device and an internal combustion engine.

Laser devices that use semiconductor lasers as excitation light sources are expected to be applied to various fields such as ignition devices, laser processing machines, and medical equipment. In particular, a method of using such a laser device as an ignition device in an internal combustion engine such as an automobile is being studied.

In such an ignition device, a laser beam (excitation light) oscillated from a semiconductor laser is applied to a Q-switch type laser resonator to oscillate a pulsed laser beam having a high energy density. The oscillated pulsed laser light is focused in the air-fuel mixture introduced into the combustion chamber through the focusing lens in the cylinder head and the transparent combustion chamber window (optical window) for incident light. As a result, plasma is generated in the combustion chamber, and the fuel injected into the combustion chamber is ignited.

Further, since the optical window is exposed to the combustion chamber, it is fixed to the optical window holding member provided in the housing by using a brazing material so that the combustion chamber can withstand high temperature and high pressure due to combustion. (See, for example, Patent Document 1).

However, in the conventional ignition device, the brazing material is exposed in the combustion chamber. Therefore, during combustion in an internal combustion engine, the temperature in the combustion chamber rises to several hundred degrees Celsius, and momentarily to several thousand degrees Celsius, so the surface of the brazing material on the combustion chamber side may be oxidized and deteriorated. .. When the brazing material deteriorates, the surface of the brazing material may be cracked or the brazing material may be chipped, and the optical window may not be stably fixed to the housing.

One aspect of the present invention is to provide a laser device capable of stably fixing an optical window.

The laser device according to one aspect of the present invention includes a light source, an optical system that collects light emitted from the light source, a housing in which the optical system is housed, and the optical system provided in the housing. In a laser apparatus having a window member through which light is incident, the window member includes an optical window through which light passes through the optical system, an optical window holding member that holds the optical window, and the optical window. And a joint portion for joining the optical window holding member, and a protective layer is provided on the emission side surface of the joint portion adjacent to the emission side end surface of the optical window holding member .

The laser device according to one aspect of the present invention can stably fix the optical window.

It is a figure which shows typically the main part of the internal combustion engine which includes the laser apparatus which concerns on embodiment. It is a figure which shows an example of the structure of a laser apparatus. It is sectional drawing which shows concretely the structure of a window member. It is sectional drawing which shows an example of another structure of a window member.

Hereinafter, embodiments will be described in detail.

A case where the laser device according to the embodiment is applied to an internal combustion engine will be described with reference to the drawings. In this embodiment, a case where an engine is used as an internal combustion engine will be described.

<Internal combustion engine>
FIG. 1 is a diagram schematically showing a main part of an internal combustion engine including a laser device according to an embodiment. As shown in FIG. 1, the engine 10 includes a laser device 11, a fuel ejection mechanism 12, an exhaust mechanism 13, a combustion chamber 14, and a piston 15.

The operation of the engine 10 will be briefly described. The fuel ejection mechanism 12 ejects a flammable air-fuel mixture containing fuel and air into the combustion chamber 14 (intake). After that, the piston 15 rises and the flammable air-fuel mixture is compressed (compression). The laser device 11 concentrates the laser light in the compressed air-fuel mixture in the combustion chamber 14 to generate plasma. The generated plasma ignites the fuel in the air-fuel mixture (ignition). Combustion gas expands in the combustion chamber 14 due to combustion (explosion) of the air-fuel mixture due to ignition. As a result, the piston 15 descends (combustion). After that, the exhaust mechanism 13 exhausts the combustion gas to the outside of the combustion chamber 14 (exhaust).

As described above, in the engine 10, a series of steps including intake, compression, ignition, combustion, and exhaust are repeated. Then, the piston 15 moves in response to the change in the volume of the gas in the combustion chamber 14 to generate kinetic energy. As the fuel, for example, natural gas or gasoline is used.

The laser device 11 is electrically connected to a drive device 16 provided outside the engine 10, and the laser light emitted from the laser device 11 is emitted from the drive device 16 based on an instruction from the engine control device 17. Is controlled by.

<Laser device>
The laser device 11 will be described. FIG. 2 shows an example of the configuration of the laser device 11. As shown in FIG. 2, the laser apparatus 11 includes a surface emitting laser (light source) 21, a first condensing optical system 22, an optical fiber (transmission member) 23, a second condensing optical system 24, a laser resonator 25, and a second. 3 It has a condensing optical system 26, a window member 27, and a housing 28. In FIG. 2, the laser beam is indicated by a two-dot chain line. Further, in this specification, the XYZ three-dimensional Cartesian coordinate system is used, and the emission direction of the laser beam from the surface emitting laser 21 is described as the + Z direction.

The surface emitting laser 21 is an excitation light source and has a plurality of light emitting units. Each light emitting unit is a vertical cavity type surface emitting laser (VCSEL: Vertical Cavity Surface Emitting Laser). When the surface emitting laser 21 emits the laser light, the plurality of light emitting units emit light at the same time, and when the surface emitting laser 21 does not emit the laser light, the plurality of light emitting units are turned off at the same time. The wavelength of the laser beam emitted from the surface emitting laser 21 is, for example, about 808 nm.

The surface emitting laser 21 is electrically connected to the driving device 16, and the driving device 16 drives the surface emitting laser 21 based on the instruction of the engine control device 17, and the laser light is emitted from the surface emitting laser 21. Will be done.

By the way, as a semiconductor laser, an end face emitting laser is known. However, the wavelength of the laser beam emitted from the end face emitting laser tends to fluctuate greatly with respect to the temperature. Since the laser device 11 is used in a high temperature environment around the engine 10, when the end face emitting laser is used as an excitation light source, a precise temperature control mechanism for keeping the temperature of the end face emitting laser constant is required. Become. Therefore, the size and cost of the laser device 11 are increased.

On the other hand, the fluctuation of the wavelength of the laser light emitted from the surface emitting laser 21 is about 1/10 of the fluctuation of the wavelength of the laser light emitted from the end face emitting laser. Since the laser device 11 uses the surface emitting laser 21 as the excitation light source, the laser device 11 does not require a precise temperature control mechanism. Therefore, the laser device 11 can be made small and low in cost. Further, since the surface emitting laser 21 has a light emitting region inside the semiconductor, there is no concern about end face destruction, and the surface emitting laser 21 can emit light stably.

Further, the surface emitting laser 21 has a very small wavelength shift of the emitted laser light due to temperature. Therefore, the surface emitting laser 21 is a Q-switch type laser resonator whose characteristics greatly change due to wavelength shift, and is an advantageous light source for increasing the energy density of the laser light. Therefore, if the surface emitting laser 21 is used as an excitation light source, the temperature control of the environment can be simplified.

The first condensing optical system 22 condenses the laser light emitted from the surface emitting laser 21 to the central portion of the −Z side end surface of the optical fiber 23. The first condensing optical system 22 has at least one condensing lens. In the present embodiment, the first condensing optical system 22 has a microlens 221 and a condensing lens system 222.

The microlens 221 is arranged on the optical path of the laser beam emitted from the surface emitting laser 21. The microlens 221 has a plurality of lenses corresponding to a plurality of light emitting portions of the surface emitting laser 21. For each lens, the laser light emitted from the corresponding light emitting portion is regarded as substantially parallel light. That is, the microlens 221 collimates the laser beam emitted from the surface emitting laser 21.

The distance between the surface emitting laser 21 and the microlens 221 in the Z-axis direction is determined according to the focal length of the microlens 221.

The condenser lens system 222 concentrates the laser light through the microlens 221.

An appropriate condenser lens system 222 is selected according to the cross-sectional area of the laser beam passing through the microlens 221, the core diameter of the optical fiber 23, and the numerical aperture (NA). The condenser lens system 222 may be composed of a plurality of optical elements.

The first condensing optical system 22 may have at least one condensing lens, and may be composed of a plurality of optical elements.

The optical fiber 23 is arranged so that the center of the end face on the −Z side of the core is located at a position where the laser beam is focused by the first condensing optical system 22. In the present embodiment, as the optical fiber 23, for example, an optical fiber having a core diameter of 1.5 mm is used.

The laser light incident on the optical fiber 23 propagates in the core and is emitted from the + Z side end surface of the core.

By providing the optical fiber 23, the surface emitting laser 21 can be placed at a position away from the laser resonator 25. This increases the degree of freedom in arranging the surface emitting laser 21 and the first condensing optical system 22. Further, since the surface emitting laser 21 can be kept away from the high temperature region around the engine 10, the range of cooling methods for the engine 10 can be widened. Further, since the surface emitting laser 21 can be provided at a position away from the engine 10 which is a vibration source, it is possible to prevent the laser light emitted from the surface emitting laser 21 from being shaken.

The second condensing optical system 24 is arranged on the optical path of the laser light emitted from the optical fiber 23, and condenses the light emitted from the optical fiber 23. The laser light focused by the second condensing optical system 24 is incident on the laser resonator 25. In the present embodiment, the second condensing optical system 24 has a first lens 241 and a second lens 242.

The first lens 241 is a collimated lens, and the laser light emitted from the optical fiber 23 is regarded as substantially parallel light.

The second lens 242 is a condensing lens, and condenses the laser light which is substantially parallel light by the first lens 241.

The second condensing optical system 24 may be composed of one optical element or may have three or more lenses as long as it has a condensing lens.

The laser cavity 25 is a Q-switch type laser cavity. In this embodiment, the laser cavity 25 has a laser medium 251 and a saturable absorber 252. In the laser resonator 25, the energy density of the incident laser light is increased, and the laser light having a wavelength of, for example, about 1064 nm is emitted with a short pulse width.

The laser medium 251 is a substantially rectangular parallelepiped Nd: YAG crystal, and Nd is doped with 1.1%.

The saturable absorber 252 is a Cr: YAG crystal having a substantially rectangular parallelepiped shape. The transmittance of the saturable absorber 252 changes depending on the amount of laser light absorbed, and the initial transmittance is about 0.50 (50%). When the amount of laser light absorbed is small, it functions as an absorber, and when the amount of laser light absorbed is saturated, it becomes transparent. When the saturable absorber 252 becomes transparent, Q-switch oscillation occurs.

Since both the Nd: YAG crystal and the Cr: YAG crystal are ceramics, the production cost is lower and the cost is lower than that of the single crystal. Further, the Nd: YAG crystal and the Cr: YAG crystal are joined to form a so-called composite crystal. Therefore, since the boundary between the Nd: YAG crystal and the Cr: YAG crystal is not separated, the laser resonator 25 can obtain the same characteristics as a single crystal.

Further, the surface (incident surface) 251a on the incident side (-Z side) of the laser medium 251 and the surface (exit surface) 252b on the exit side (+ Z side) of the saturable absorber 252 are optically polished. There is. This can act as a mirror.

Further, the incident surface 251a and the emitting surface 252b correspond to the wavelength of the light emitted from the surface emitting laser 21 (for example, 808 nm) and the wavelength of the laser light emitted from the laser resonator 25 (for example, 1064 nm). A dielectric layer is formed. For example, a dielectric layer is formed on the incident surface 251a, which exhibits high transmittance for laser light having a wavelength of 808 nm and high reflectance for laser light having a wavelength of 1064 nm. A dielectric layer having a reflectance of about 50% with respect to a laser beam having a wavelength of 1064 nm is formed on the emission surface 252b.

When the laser light focused by the second condensing optical system 24 is incident on the laser resonator 25, the laser beam resonates and is amplified in the laser resonator 25. Further, the laser medium 251 is excited by the laser light incident on the laser medium 251. The wavelength of the laser beam emitted from the surface emitting laser 21 (for example, 808 nm) is the wavelength having the highest absorption efficiency in the YAG crystal. Further, the laser light emitted from the surface emitting laser 21 and incident on the laser medium 251 through the first condensing optical system 22 and the optical fiber 23 is also referred to as “excitation light”.

The energy density of the laser beam increases because the laser beam resonates and is amplified in the laser resonator 25. When the amount of laser light absorbed by the saturable absorber 252 is saturated, Q-switch oscillation occurs in the saturable absorber 252. As a result, the laser beam having a high energy density is emitted from the laser resonator 25 by concentrating the energy with a short pulse width. The laser light emitted from the laser resonator 25 is also referred to as a pulse laser light. The wavelength of the pulsed laser light is, for example, about 1064 nm.

The laser beam amplified by the laser resonator 25 is incident on the third condensing optical system 26.

The third condensing optical system 26 is arranged on the optical path of the laser beam emitted from the laser resonator 25. The third condensing optical system 26 condenses the laser light emitted from the laser resonator 25 and obtains a high energy density at the condensing point. When the focused laser light exceeds a certain energy density, the molecules constituting the gas contained in the combustible air-fuel mixture in the combustion chamber 14 are ionized and separated into cations and electrons, resulting in plasma formation (break). Down).

In the present embodiment, the third condensing optical system 26 is composed of a third lens 261, a fourth lens 262, and a fifth lens 263.

The third lens 261 is an optical element for increasing the divergence angle of the laser light emitted from the laser resonator 25, and a concave lens is used in the present embodiment.

The fourth lens 262 is an optical element for collimating the divergent light from the third lens 261, and in the present embodiment, the collimating lens is used.

The fifth lens 263 is an optical element for condensing the laser light from the fourth lens 262, and in the present embodiment, the condensing lens is used.

The laser beam is focused by the fifth lens 263, and a high energy density can be obtained at the focusing point. When the focused laser light exceeds a certain energy density, the molecules constituting the gas in the combustible mixture in the combustion chamber 14 are ionized, and plasma is generated.

The third condensing optical system 26 is the light emitted from the laser apparatus 11 depending on the position of the lens constituting the third condensing optical system 26 in the optical axis direction and the combination of the lenses constituting the third condensing optical system 26. The light collection position can be adjusted in the Z-axis direction.

Although the third condensing optical system 26 is composed of three lenses, it may be composed of at least one lens, may be composed of one optical element, or may be composed of a plurality of optical elements. It may be composed of.

The configuration of the window member 27 will be described. The configuration of the window member 27 is specifically shown in FIG. As shown in FIG. 3, the window member 27 has an optical window (window body) 271, an optical window holding member 272, a dielectric layer 273, and a protective layer 274.

The optical window 271 is arranged on the optical path of the laser beam emitted from the third condensing optical system 26. The optical window 271 is made of a transparent or translucent material and has an entrance surface 271a and an emission surface 271b of laser light. The optical window 271 is fixed to the inner surface of the optical window holding member 272 by a brazing portion 29 formed by using a brazing material (joining material) as a joining portion. The optical window 271 is arranged so as to be located in an opening formed on the surface of the housing 28 on the combustion chamber 14 side. The laser light emitted from the third condensing optical system 26 passes through the optical window 271 and is condensed in the combustion chamber 14.

The shape of the optical window 271 in a plan view is not particularly limited, and may be, for example, a rectangular shape, a circular shape, an elliptical shape, a rectangular shape, a polygonal shape, or the like.

As the material of the optical window 271, for example, optical glass, heat-resistant glass, quartz glass, sapphire glass and the like can be used. In particular, the optical window 271 needs to have sufficient compressive strength in order to protect the optical member inside the housing 28 from the combustion pressure generated in the combustion chamber 14. Therefore, it is conceivable to increase the thickness of the optical window 271. However, when the thickness of the optical window 271 is increased, a part of the laser beam incident on the emission surface of the optical window 271 is reflected, and it becomes easy to collect the light inside the optical window 271. Therefore, in order to suppress the focusing inside the optical window 271, it is necessary to lengthen the focal length of the third focusing optical system 26.

When the focal length of the third focusing optical system 26 is lengthened, the numerical aperture (NA) of the lens is reduced, so that the focusing intensity is lowered and the ignitability is lowered. Therefore, the thickness of the optical window 271 is preferably as thin as possible. Therefore, as the material of the optical window 271, it is preferable to use sapphire glass having excellent durability in a high temperature and high pressure environment.

The optical window holding member 272 is attached so as to cover the housing 28 around an opening formed on the surface of the housing 28 on the combustion chamber 14 side. The optical window holding member 272 is fixed to the housing 28 by a welded portion 30 formed by laser welding or the like. The optical window holding member 272 may be fixed to the housing 28 by, for example, screwing, shrink fitting, or bonding, in addition to welding such as laser welding.

The optical window holding member 272 fixes and holds the optical window 271 on the inner surface thereof by a brazing portion 29. Examples of the brazing material include Au, Ag, Cu, Pd, Al, Mg, Pt, P, Ti, W, Sn, Ni, Zn, Si, B, Cd, Li, Mn, Cr, or Zr, or stainless steel. Can be used. One of the above may be used alone, or two or more thereof may be used in combination. Further, another additive may be mixed with any of the above as a main component.

As the material for forming the optical window holding member 272, for example, a heat-resistant metal material such as iron, nickel, Ni—Fe alloy, Ni—Cr—Fe alloy, Ni—Co—Fe alloy, or stainless steel can be used. .. Examples of the Ni—Cr—Fe alloy include Inconel and the like. Examples of the Ni—Co—Fe alloy include Kovar and the like.

The exit side end surface 272b of the optical window holding member 272 is substantially flush with the end surface 28b of the second housing 28-2. As a result, when the welded portion 30 is formed by laser welding or the like, the laser beam can be easily collected on the welded portion 30, so that welding is performed between the optical window holding member 272 and the second housing 28-2. The portion 30 can be stably and reliably provided. Therefore, the optical window holding member 272 can be stably fixed to the second housing 28-2.

The dielectric layer 273 is provided on the surface of the optical window 271 on the third condensing optical system 26 side, that is, on the incident surface 271a of the laser beam of the window member 27. The dielectric layer 273 functions as an antireflection (AR) film (AR film). The dielectric layer 273 has a high transmittance for a laser beam having a wavelength of 1064 nm.

Examples of the material forming the dielectric layer 273 include Si, Na, Al, Ca, Mg, B, C, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, and Sr. , Zr, Nb, Ru, Pd, Ag, In, Sn, Hf, Ta, W, Ot, Au, and Bi as a main component, or a nitride, oxide, or carbide of the main component. And materials containing at least one of fluorides can be used.

Specifically, for example, MgF, Si _{3N 4, or SiO 2 can be} used. Further, when the difference in refractive index between the dielectric layer 273 and the optical window 271 is small, the antireflection characteristics can be improved.

The thickness of the dielectric layer 273 is not particularly limited as long as it can have a high transmittance for a laser beam having a wavelength of 1064 nm. For example, when the optical window 271 is made of sapphire glass, the refractive index of sapphire is about 1.74, so that the thickness of the dielectric layer 273 is preferably about 202 nm and the refractive index is preferably about 1.32. ..

The dielectric layer 273 can be formed, for example, on the surface of the optical window 271 on the third condensing optical system 26 side after the optical window 271 is fixed to the optical window holding member 272 by brazing. As a method for forming the dielectric layer 273 on the optical window 271, for example, thin-film deposition, sputtering, thermal spraying, coating, or a sol-gel method can be used.

Further, since it is possible to reduce the influence of the reflected light generated by the optical window 271 on the optical member coaxial with the surface emitting laser 21 as return light, it is possible to reduce fluctuations in the intensity of the laser light. ..

In the present embodiment, the dielectric layer 273 is a single layer, but the dielectric layer 273 is not limited to this, and may be a multilayer layer.

The protective layer 274 is provided on the surface of the brazing portion 29 and the optical window holding member 272 on the combustion chamber 14 side, that is, the surface on the side where the laser beam is emitted from the window member 27.

_The material of the protective layer 274 may be, for example, a metal such as Ni, Au, Pt, Ti, Ag, Cu, Al, Pd, Rh, W, Mo, Zr, Ta, Nb _, or Ir; ₄ , or metal oxides such as Al ₂ O ₃ ; carbon materials such as Ketjen black, acetylene black, carbon black, graphite, or carbon nanotubes can be used. These types may be used alone or in combination of two or more. Above all, it is preferable to use Ni because it has high oxidation resistance. Further, Au, Pt, or Ti may be used because it has high oxidation resistance and corrosion resistance.

The protective layer 274 is formed on the surface of the brazing portion 29 and the optical window holding member 272 on the combustion chamber 14 side after the optical window 271 is fixed to the optical window holding member 272 and the brazing portion 29. As a method for forming the protective layer 274 on the brazing portion 29 and the optical window holding member 272, for example, electroplating, sol-gel method, thin film deposition, sputtering, thermal spraying, coating, or the like can be used. Above all, it is preferable to use electroplating from the viewpoint that the protective layer 274 is stably formed on the brazed portion 29 and the optical window holding member 272 without affecting the optical window 271. Ni has high oxidation resistance and corrosion resistance, and is suitable as a material for a protective layer in that it can be electrolytically plated.

By providing the protective layer 274 on the brazing portion 29 and the optical window holding member 272, oxidation of the brazing portion 29 can be suppressed. Therefore, even if the temperature inside the combustion chamber 14 rises to several hundred degrees Celsius, or momentarily several thousand degrees Celsius, during combustion in the internal combustion engine, the surface of the brazed portion 29 is prevented from being oxidized and deteriorated. be able to. This makes it possible to prevent cracks from occurring on the surface of the brazed portion 29 and the brazing portion 29 from being missing. Therefore, the optical window 271 can be stably fixed by the optical window holding member 272 for a long period of time.

The average thickness of the protective layer 274 is not particularly limited as long as the protective layer 274 can stably cover the brazed portion 29 and does not obstruct the passage of the laser beam emitted from the optical window 271. From the viewpoint that the protective layer 274 stably covers the brazed portion 29, it is preferable that the average thickness of the protective layer 274 is formed to be, for example, at least several μm.

In the present embodiment, as shown in FIG. 3, the exit surface 271b on the exit side of the optical window 271 is substantially on the same plane as the exit side end surface (emission side end surface) 272b of the optical window holding member 272. There is. As a result, the protective layer 274 with a small variation in thickness can be stably formed on the brazed portion 29 and the optical window holding member 272.

Regarding the positions of the emission surface 271b of the optical window 271 and the emission side end surface 272b of the optical window holding member 272, for example, the emission surface 271b of the optical window 271 is located on the incident side of the emission side end surface 272b of the optical window holding member 272. May be. In this case, when the protective layer 274 is formed on the brazing portion 29 and the optical window holding member 272 by, for example, electrolytic plating, current tends to concentrate in the vicinity of the end portion of the brazing portion 29, which tends to be a starting point of abnormal precipitation. Therefore, there is a possibility that the protective layer 274 is formed in a state of protruding near the end of the brazed portion 29. Further, when the protective layer 274 is formed, if there is a portion where abnormal precipitation is likely to occur, the denseness of the protective layer 274 may decrease. Further, when the protruding portion of the protective layer 274 is irradiated with the laser beam, the laser beam is reflected, which may cause a decrease in the output of the laser beam.

Therefore, in the present embodiment, the exit surface 271b on the exit side of the optical window 271 is substantially flush with the exit side end surface 272b of the optical window holding member 272, and the thickness of the brazing portion 29 and the optical window holding member 272 is increased. A protective layer 274 with small variation is formed. Further, when the protective layer 274 is formed on the brazed portion 29 and the optical window holding member 272 by, for example, electrolytic plating, the protective layer 274 can have high density. Further, it is possible to prevent the laser beam emitted from the optical window 271 from being irradiated to the protective layer 274 and reflected. Therefore, it is possible to suppress a decrease in the output of the laser beam emitted from the third condensing optical system 26.

As shown in FIG. 2, the housing 28 houses the second condensing optical system 24, the laser resonator 25, the third condensing optical system 26, and the window member 27. In the present embodiment, the housing 28 is composed of a first housing 28-1 and a second housing 28-2. The first housing 28-1 houses the second condensing optical system 24 and the laser resonator 25. The second housing 28-2 houses the third condensing optical system 26 and the window member 27.

For the housing 28, for example, a heat-resistant metal such as iron, Ni—Fe alloy, Ni—Cr—Fe alloy, Ni—Co—Fe based alloy, or stainless steel is used. Examples of the Ni—Cr—Fe alloy include Inconel and the like. Examples of the Ni—Co—Fe alloy include Kovar and the like.

As described above, the laser device 11 according to the present embodiment has the protective layer 274 on the surface of the brazing portion 29 and the optical window holding member 272 on the combustion chamber 14 side. As a result, deterioration of the brazed portion 29 can be prevented, so that the optical window 271 can be stably fixed to the optical window holding member 272. Therefore, the laser device 11 according to the present embodiment can prevent the optical window 271 from falling off and can be used stably, so that a highly reliable laser device can be provided. In the present embodiment, the laser device has been described as an example of the laser device, but the present invention is not limited to this. In other laser devices as well, the presence of the protective layer can protect the joint from the influence of the environment in which the laser device is used, and can provide a highly reliable laser device.

Since the engine 10 includes the laser device 11 according to the present embodiment, it can be stably burned. As a result, the engine 10 can be used stably and continuously.

In the present embodiment, the protective layer 274 is provided on the surface of the brazing portion 29 and the optical window holding member 272 on the combustion chamber 14 side, but is provided only on the surface of the brazing portion 29 on the combustion chamber 14 side. It may be provided on the surface of the brazing portion 29, the optical window holding member 272, and the housing 28 on the combustion chamber 14 side.

In the present embodiment, the brazed portion 29 formed by using the brazing material which is the joining material is used as the joining portion, but the present invention is not limited to this. The joining portion may be made of a material capable of joining the optical window 271 and the optical window holding member 272 in the environment in which the laser device is used.

In the present embodiment, as shown in FIG. 3, the exit surface 271b of the optical window 271 is set to be substantially on the same plane as the exit side end surface 272b of the optical window holding member 272, but the present invention is not limited to this. For example, as shown in FIG. 4, the exit surface 271b may be projected toward the combustion chamber 14 in the emission direction from the emission side end surface 272b of the optical window holding member 272. Even in this case, the brazed portion 29 and the optical window holding member 272 do not have an end portion on which the current tends to concentrate when the protective layer 274 is formed by, for example, electrolytic plating. Therefore, the brazing portion 29 and the optical window holding member 272 can be stably formed with the protective layer 274 having a small variation in thickness. Further, in the brazing portion 29 and the optical window holding member 272, when the protective layer 274 is formed by, for example, electrolytic plating, there is no place where the protective layer 274 is likely to abnormally precipitate, so that the protective layer 274 has high density. Can have. Further, since the laser light emitted from the optical window 271 is irradiated to the protective layer 274 and the laser light can be prevented from being reflected, it is possible to suppress a decrease in the output of the laser light.

In the present embodiment, the housing 28 houses the second condensing optical system 24, the laser resonator 25, the third condensing optical system 26, and the optical window 271, but further, the first condensing optical system 22. , And the optical fiber 23 may be accommodated.

In the present embodiment, the first housing 28-1 has a second condensing optical system 24 and a laser cavity 25, and the second housing 28-2 has a third condensing optical system 26 and a window member 27. Each is housed, but not limited to this. For example, the first housing 28-1 may accommodate only the second condensing optical system 24, and the second housing 28-2 may further accommodate the laser cavity 25. Further, the first housing 28-1 further houses the third condensing optical system 26 in addition to the second condensing optical system 24 and the laser resonator 25, and the second housing 28-2 further houses the window member 27. May contain only.

In the present embodiment, the case where the surface emitting laser 21 is used as the excitation light source has been described, but the present invention is not limited to this, and other light sources may be used.

In the present embodiment, if it is not necessary to place the surface emitting laser 21 at a position away from the laser resonator 25, the optical fiber 23 may not be provided.

In the present embodiment, the dielectric layer 273 is provided on the surface of the optical window 271 on the third condensing optical system 26 side, that is, the incident surface on which the laser beam is incident on the window member 27. If there is no such thing, it is not necessary to provide it.

In the present embodiment, the case where the laser device 11 according to the present embodiment is used as an internal combustion engine for the ignition device of the engine 10 in which the piston is moved by the combustion gas has been described, but the present invention is not limited thereto. The laser device 11 can be used, for example, for a rotary engine, a gas turbine engine, a jet engine, or the like, which burns fuel to generate combustion gas. Further, the laser device 11 may be used for cogeneration, which is a system that extracts power, heat, or cold heat by utilizing waste heat and enhances energy efficiency comprehensively. Further, the laser device 11 may be used for an image forming device (for example, a laser copier, a laser printer, etc.), an image projection device (for example, a projector), a laser processing machine, a laser peening device, a terahertz generator, or the like.

As described above, the embodiments have been described, but the above embodiments are presented as examples, and the present invention is not limited to the above embodiments. The above embodiment can be implemented in various other embodiments, and various combinations, omissions, replacements, changes, and the like can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

10 Engine (internal combustion engine)
11 Laser device 21 Surface emitting laser 22 1st condensing optical system 23 Optical fiber 24 2nd condensing optical system 25 Laser resonator 26 3rd condensing optical system 27 Window member 271 Optical window (window body)
271a Incident surface 271b Emission surface 272 Optical window holding member 272b Emission side end surface (emission side end surface)
273 Dielectric layer 274 Protective layer 28 Housing 29 Brazed part

Japanese Patent No. 5873689

Claims (9)

Light source and
An optical system that collects the light emitted from the light source and
The housing in which the optical system is housed and
In a laser device provided in the housing and having a window member to which light is incident through the optical system.
The window member has an optical window through which light passes through the optical system, an optical window holding member that holds the optical window, and a joint portion that joins the optical window and the optical window holding member. ,
A laser device characterized in that a protective layer is provided on the emission side surface of the joint portion adjacent to the emission side end surface of the optical window holding member . The laser device according to claim 1, wherein the protective layer is provided on the surface of the optical window holding member, or on the surface of the optical window holding member and the housing. The first or second aspect of the present invention, wherein the emission side end surface of the optical window holding member and the emission side surface of the joint portion are coplanar, and the protective layer is provided on the emission side end surface and the emission side surface. Laser device. The protective layer includes Ni, Au, Pt, Ti, Ag, Cu, Al, Pd, Rh, W, Mo, Zr, Ta, Nb, Ir, SiO ₂ , Si ₃ N ₄ , Al ₂ O ₃ , and carbon. The laser apparatus according to any one of claims 1 to 3, which comprises any one or more of the materials. One of claims 1 to 4 , wherein the emission surface of the optical window is on the same plane as the emission side end surface of the optical window holding member, or the light is projected from the emission side end surface in the emission direction. The laser device according to the section. The laser device according to any one of claims 1 to 5 , wherein the emission side end surface of the optical window holding member is flush with the end surface of the housing. The laser device according to any one of claims 1 to 6 , wherein the joint portion is formed of a brazing material. The laser device irradiates a laser beam into a combustion chamber that burns fuel, and the laser device irradiates the combustion chamber.
The laser device according to any one of claims 1 to 7, wherein the protective layer is formed on the surface of the joint portion on the combustion chamber side. In an internal combustion engine that burns fuel to generate combustion gas
The laser apparatus according to any one of claims 1 to 8 is provided.
An internal combustion engine, characterized in that the laser device ignites the fuel.

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