JP2015001158A - Optical element sealing structure, manufacturing method therefor, and laser ignition device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical element sealing structure and a manufacturing method therefor having excellent airtightness and durability, and a highly reliable laser ignition device using the same.SOLUTION: An optical element sealing structure includes a holder 11 which is provided with: a protective glass engaging part 110 to which one end face of a protective glass 10 is abutted; a protective glass positioning groove part 111 which is bored such that a predetermined gap GP (0.01 mm or more and 0.05 mm or less) is formed between the outer periphery of the protective glass 10; and a sealing glass housing groove part 112 which is bored so as to cover a part or the whole of the outer periphery of the protective glass 10. A sealing glass 12 is formed by using low melting point glass having a glass transition temperature of 600°C or less, and an optical element 10 and the holder 11 are sealed in an airtight manner by fusing the sealing glass 12.

Description

  The present invention relates to a laser ignition device used for ignition of an internal combustion engine such as a vehicle, and in particular, an optical element sealing structure that hermetically seals at least optical elements such as a condenser lens and a protective glass, and the structure The present invention relates to a manufacturing method and a laser ignition device.

  In recent years, a laser including a Q-switch type laser medium as a light source for excitation, such as a flash lamp and a semiconductor laser, for ignition of a highly ignitable internal combustion engine such as a high supercharged engine, a high compression engine, a natural gas engine having a large cylinder inner diameter, etc. It irradiates the resonator, oscillates as a pulse laser that concentrates and emits energy with a short pulse width, and further condenses the pulse laser in the air-fuel mixture using an optical element such as a condenser lens. Various laser ignition devices that ignite an internal combustion engine by generating high flame nuclei have been proposed.

  For example, in Patent Document 1, in a laser device used for an ignition device of an internal combustion engine, a material having a higher thermal conductivity than the casing is used in the casing in order to improve heat discharge between the combustion chamber window and the casing. A laser ignition device provided with a charging portion is disclosed.

  Furthermore, in the conventional laser ignition device disclosed in Patent Document 1, in order to form a direct contact with the insertion portion provided inside the casing with the optical element that constitutes the combustion chamber window, a shape coupling such as press fitting or pinching, or Are connected in the axial direction and / or in the radial direction by material bonding such as bonding, bonding, and soldering.

Special table 2010-540822

However, as disclosed in Patent Document 1, when shape coupling such as press fitting or sandwiching is used, the thermal expansion coefficient of an optical material such as quartz glass, heat-resistant glass, or sapphire used for an optical element, and a casing are used. There is a risk that the airtightness between the optical element and the casing may be lost due to a difference from the thermal expansion coefficient of a metal material such as steel.
In the laser ignition device, such a decrease in airtightness is caused by the mixture in the combustion chamber entering the device, forming a coating on the inside of the combustion chamber window, affecting the progress of the laser beam, and causing normal ignition. There is a risk that it will not be possible.

Further, in the case where the optical element and the casing are directly connected as described above, it is extremely difficult to make the sealing pressure acting on the optical element uniform during pressing or sandwiching. There is a risk of cracking due to an unbalanced load.
Further, in the case of such a shape, since the residual stress is also increased, the thermal stress during use is also increased, and there is a possibility that the optical element is cracked.
In addition, optical materials such as heat-resistant glass, quartz glass, and sapphire used for optical elements have lower thermal conductivity than metal materials, and as disclosed in Patent Document 1, extremely high thermal conductivity such as copper is contained in the casing. When the material having the rate is disposed, the thermal stress is further increased, and the durability of the ignition device may be significantly reduced.

  On the other hand, in the case of the material bonding of Patent Document 1, the specific material is not necessarily clear, but when the optical element and the casing are bonded by soldering or brazing as in the past, the flux contained in the solder or brazing material Components and the like are evaporated and redeposited, which may contaminate the inside of the optical window and the surface of the condenser lens.

  The present invention has been made in view of such circumstances, and in sealing an optical element such as a protective glass and a condenser lens in an airtight manner, an optical element sealing structure excellent in airtightness and durability, and its manufacture It is an object of the present invention to provide a method and a reliable laser ignition device using them.

  The optical element sealing structure (1, 1a, 2, 2a, 2b, 2c) which is the main part of the present invention is obtained by replacing one or a plurality of optical elements (10, 10a, 20, 20a, 20b, 20c) with the optical element. An optical element sealing structure housed and sealed inside the housing case (11, 11a, 21, 21a, 21b, 21c), the optical element housing case (11, 11a, 21, 22a, 22b, 22c) are optical element locking portions (110, 210) with which one end face of the optical element (10, 10a, 20, 20a, 20b, 20c) abuts, and the optical element (10, 10a, 20). , 20a, 20b, 20c) with optical elements positioning groove portions (111, 111a, 211, 211a, 211b, 211c) drilled by providing a predetermined gap (GP) with respect to the outer periphery of the optical elements (10, 10a, 20, 20a, 20b, and 20c) a sealing glass accommodating groove portion that has been drilled so as to dispose the sealing glass (12, 12a, 22, 22a, 22b, and 22c) so as to cover a part or the entire periphery of the outer periphery. 112, 112a, 212, 212a, 212b, 212c), and the sealing glass (12, 12a, 22, 22a, 22b, 22c) is made of a low melting point glass having a glass transition temperature of 600 ° C. or less. , By sealing the sealing glass (12, 12a, 22, 22a, 22b, 22c), the optical element (10, 10, 20, 20a, 20b, 20c) and the optical element housing case (11, 11a, 21, 22 a, 22 b, 22 c) are hermetically sealed.

A laser ignition device (9) for condensing an optical element sealing structure (1, 1a, 2, 2a, 2b) of the present invention by condensing a high energy density laser beam in a combustion chamber (CMB) of an internal combustion engine. , 9a, 9a, 9b, 9c), the optical elements (10, 10a, 20, 20a, 20b, 20c) are formed by the sealing glass (12, 12a, 22, 22a, 22b, 22c) once heated and melted. ) And the optical element housing (11, 11a, 21, 22a, 22b, 22c) are ensured, and the intrusion of the air-fuel mixture in the combustion chamber (CMB) is reliably prevented, Contamination of the condensing lens can be prevented.
Moreover, since the thermal expansion coefficients of the sealing glass 12, 12a, 22, 22a, 22b, and 22c) and the optical elements (10, 10a, 20, 20a, 20b, and 20c) are close, even if they are exposed to thermal stress, The optical element (10, 10a, 20, 20a, 20b, 20c) is not damaged.

  In the method for producing an optical element sealing structure (1, 1a, 2, 2a, 2b) of the present invention, at least a low-melting glass powder having a glass transition temperature of 600 ° C. or lower is pressed and consolidated to form a sealed glass molded body (12MLD 22MLD), an optical element locking portion (110, 210) with which one end face of the optical element (10, 10a, 20, 20a, 20b, 20c) abuts, An optical element positioning groove (111, 111a, 211, 211a, 211b, 211c) provided with a predetermined gap (GP) with respect to the outer periphery of the optical element (10, 10, 20, 20a, 20b, 20c); Sealing glass accommodating grooves (112, 112a, 212, 212a, 212b, so as to cover part or all of the outer periphery of the element (10, 10a, 20, 20a, 20b, 20c) 12c), an optical element housing step (11, 11a, 21, 21a, 21b, 21c) and the sealing glass molded body (12MLD, 22MLD) are disposed in order. And the sealing glass molded body (12MLD, 22MLD) disposed in the sealing glass housing groove (112, 112a, 212, 212a, 212b, 212c) is heated and melted at a temperature of 600 ° C. or higher to obtain the optical element. (10, 10a, 20, 20a, 20b, 20c) and an optical element sealing step for hermetically sealing the optical element housing (11, 11a, 21, 21a, 21b, 21c). It is characterized by.

In addition, the laser ignition device (9, 9a, 9a, 9b, 9c) using the optical element sealing structure (1, 1a, 2, 2a, 2b) of the present invention has an excitation provided outside as an optical element. One or more excitation light lenses (50) that use one or more excitation light (LSR _PMP ) introduced from the light source (80, 80b) as parallel light, and excitation light (LSR) collimated by the excitation light lens (50) _PMP) and resonates amplified energy dense pulsed light _{(LSR PLS)} Q-switched laser resonator for emitting (and 40,40b), pulsed light emitted from the resonator _{(40,40b) (LSR PLS} ) and one or more expansion lenses extend (30, 30B), one also of the expansion lens (30, 30B) pulsed light expanded by _{(LSR PLS)} of an internal combustion engine combustion chamber (CMB) One or a plurality of condensing lenses (20, 20b, 20b) for condensing light at a plurality of predetermined positions (FP) and the combustion chamber (CMB) of the internal combustion engine, the condensing lenses (20, 20a, 20b, 20c) A protective glass (10, 10a), and at least one of these optical elements (10, 10a, 20, 20a, 20b, 20c, 30, 30b, 40, 40b, 50, 50b) The optical element sealing structure (1, 1a, 2, 2a) according to any one of claims 1 to 7, wherein the protective glass (10, 10a) and the condenser lens (0, 20a, 20b, 20c) are disposed. 2b, 2c), and a high energy density pulse light (LSR _PLS ) is collected in the air-fuel mixture introduced into the combustion chamber (CMB) as a single unit in the cylindrical housing (7). Ignition of the mixture is performed.
In the laser ignition device (9, 9a, 9a, 9b, 9c) of the present invention, the optical element (10, 10a, 20, 20a, 20b, 20c) and the respective optical element (10, 10a, 20, 20a, 20b). , 20c) sealing glass (12, 22, 22b, 22c) made of low-melting glass with a gap (GP) between the optical element housing (11, 11a, 21, 21a, 21b, 21c). By using the optical element structure (1, 1a, 2, 2a, 2b, 2c) according to any one of claims 1 to 7, which is fused by the above-described method, it is possible to form the casing by caulking or the like. Even if a strong compressive force is not applied to the protective glass 10, the airtightness of the optical element can be secured, the influence of the stress remaining in the casing is reduced, and the protective glass 10 is cracked when a thermal stress is applied. It is suppressed.
Even when used in high-temperature environments, it does not contain volatile components or organic components such as conventional adhesives used in material bonding and resins contained in brazing materials. The laser ignition device (9, 9a, 9b, 9c) having excellent reliability can be realized without contaminating the element.

Sectional drawing of the principal part of the laser ignition apparatus 9 containing the optical element sealing structures 1 and 2 in the 1st Embodiment of this invention. Partial sectional view showing an overall outline of the laser ignition device 9 Assembly and exploded view of laser ignition device 9 It is a figure for demonstrating the manufacturing method of the protective glass sealing structure 1 which seals and fixes the protective glass 10 as an optical element, Comprising: Sectional drawing which shows an arrangement | positioning process Sectional drawing which shows the fusion sealing process following FIG. 2A Sectional drawing which shows the winding-up process following FIG. 2B Sectional drawing of protective glass sealing structure 1 It is a figure for demonstrating the manufacturing method of the condensing lens sealing structure 2 which seals and fixes the condensing lens 20 as an optical element, Comprising: Sectional drawing which shows an arrangement | positioning process Sectional drawing which shows the fusion sealing process following FIG. 3A Sectional drawing of the condensing lens sealing structure 2 following FIG. 3B Plan view of the condensing lens sealing structure 2 shown in FIG. 3C The top view which shows the modification 2a of a condensing lens sealing structure Sectional drawing which shows the front-end | tip part assembly | attachment process of the laser ignition apparatus 1 following FIG. 3B Sectional drawing which shows the front-end | tip part welding process following FIG. 4A Sectional drawing which shows the principal part which shows the modification 9a of the laser ignition apparatus in the 1st Embodiment of this invention The top view which shows the outline | summary of the optical element sealing structure 2c in the 2nd Embodiment of this invention Sectional drawing along BB in FIG. 6A Sectional drawing of the principal part of the ignition device 9c containing the optical element sealing structure 2 in the 2nd Embodiment of this invention. Plan view of the laser ignition device 9b as seen from the combustion chamber side Partial sectional view showing the overall outline of the ignition device 9b The top view which shows the outline | summary of the modification 2c of the optical element sealing structure in the 2nd Embodiment of this invention Sectional drawing along BB in FIG. 8A The top view which is the modification 2d of the optical element sealing structure in the 2nd Embodiment of this invention, Comprising: The state before heating melting is shown in the left half part, and the state after heating melting is shown in the right half part 9A is a cross-sectional view of the optical element sealing structure of FIG. 9A before heating and melting. 9A is a cross-sectional view of the optical sealing structure of FIG. 9A after heating and melting.

With reference to FIG. 1A, the optical element sealing structures 1 and 2 in the first embodiment of the present invention will be described. The optical element sealing structures 1 and 2 in the present embodiment condense the pulsed light LSR _PLS at one condensing point FP in the combustion chamber CMB and ignite the air-fuel mixture in the combustion chamber CMB. 9 is used.
In the present embodiment, the optical element sealing structures 1 and 2 are formed by accommodating the optical elements 10 and 20 in the optical element holders 11 and 21, respectively.

First, the protective glass sealing structure 1 in which the protective glass 10 is sealed and fixed will be described as an optical element.
The protective glass sealing structure 1 has a structure in which the protective glass 10 is accommodated in the protective glass holder 11 and the gap between the protective glass holder 11 and the protective glass 10 is hermetically sealed with the sealing glass 12.

For the protective glass 10, a known heat-resistant optical material such as quartz, sapphire, ruby, CaF ₂ , BaF ₂ , MgF ₂ , LiF, YAG, or ZnSe is used, and the outer periphery is formed in a cylindrical shape.
Further, a light incident surface side surface of the protective glass 10 and an antireflection film 101 that suppresses reflection of the pulsed light LSR _PLS are formed.

The protective glass holder 11 is made of a metal having a thermal expansion coefficient close to that of the protective glass 10 such as iron-cobalt-nickel alloy (Kovar) or iron-nickel alloy (42 alloy), and is formed in a cylindrical shape having both ends opened.
The protective glass holder 11 includes, as an optical element locking portion, a protective glass locking portion 110 with which one end face of the protective glass 10 abuts, and an optical element positioning groove as an outer diameter of the protective glass 10 and a predetermined gap GP ( Protective glass positioning groove portion 111 provided with 0.01 mm ≦ GP ≦ 0.05 mm) and a sealing glass housing groove portion for disposing sealing glass 12 so as to cover a part or the entire periphery of protective glass 10 111 is formed in a stepped groove shape.

A winding tightening portion 113 is formed extending to the front end of the protective glass holder 11 on the combustion chamber side.
The winding portion 113 elastically presses the protective glass 10 via the backup ring 13.

The thickness of the sealing glass 12 varies depending on how the glass flows in the heating and melting step described later, and may not be constant.
Therefore, the pressure acting on the sealing glass 12 when the backup ring 13 is tightened varies, and the sealing glass 12 may be damaged when the winding portion 113 is formed.

On the other hand, since the protective glass 10 is fused to the protective glass holder 11 by the sealing glass 12, it is not necessary to exert a strong pressing force by the winding fastening portion 113.
Since the backup ring 13 only needs to prevent the protective glass 10 from falling into the combustion chamber when the adhesive strength of the sealing glass 12 is lowered, the backup ring 13 is slightly smaller than the protective glass 10 to the extent that the protective glass 10 can be prevented from coming off. In order to prevent the sealing glass 12 from being damaged, the inner diameter of the sealing glass 12 is made small and the sealing glass 12 is not in contact with the sealing glass 12.
The backup ring 13 is an elastic metal material having a thermal expansion coefficient close to that of the protective glass 10 and the sealing glass 12 (for example, stainless steel (NS-5), iron cobalt nickel alloy (Kovar), iron nickel alloy (42 alloy), etc.). Is used and is formed in a ring shape.

The sealing glass 12 becomes a molten state at a temperature of 600 ° C. or higher (that is, has a glass transition temperature of 600 ° C. or lower), borosilicate glass (for example, PBO—SiO ₂ —B ₂ O ₃ , PBO— P ₂ O ₅ —SnF ₂ etc.), aluminosilicate glass (for example, Li ₂ O—Al ₂ O ₃ —SiO ₂ , B ₂ O ₃ —Al ₂ O ₃ —SiO ₂ etc.) It is used.
The sealing glass 12 penetrates not only between the outer peripheral surface of the protective glass 10 and the sealing member housing groove 112 of the protective glass holder 11 but also into the protective glass positioning groove 111, and the protective glass 10 and the protective glass holder 11. And are airtightly joined.
A specific method for joining the protective glass 10 and the protective glass holder 11 through the sealing glass 12 will be described later with reference to FIGS. 2A to 2D.

Next, the condensing lens sealing structure 2 in which the condensing lens 20 is sealed and fixed as an optical element will be described.
The condenser lens sealing structure 2 has a structure in which the condenser lens 20 is accommodated in the condenser lens holder 21 and the gap between the condenser lens holder 21 and the condenser lens 20 is hermetically sealed by a sealing glass 22. It has become.

The condenser lens 20 is made of heat-resistant glass such as borosilicate glass, known heat-resistant optical material such as quartz, sapphire, ruby, CaF ₂ , BaF ₂ , MgF ₂ , LiF, YAG, and ZnSe, and has an outer periphery. It is formed in a cylindrical shape.
In the condensing lens 20, the curvatures of the incident surface and the exit surface are adjusted so that the pulsed light LSR _PLS is condensed at a predetermined condensing position FP in the combustion chamber.
An antireflection film (AR coating) that suppresses the reflection of the pulsed light LSR _PLS may be applied to the surface of the condenser lens 20.

The condensing lens holder 21 is made of a metal having a thermal expansion coefficient close to that of the condensing lens 20 such as stainless steel (NS-5), iron cobalt nickel alloy (Kovar), iron nickel alloy (42 alloy), and both ends are open. It is formed in a cylindrical shape.
The condensing lens holder 21 has a condensing lens locking portion 210 with which one end surface of the condensing lens 20 abuts, an outer diameter of the condensing lens 20 and a predetermined gap GP (0.01 mm ≦ GP ≦ 0.05 mm). And a condensing lens positioning groove 211 formed in an annular groove shape, and a sealing glass housing for disposing the sealing glass 22 so as to cover a part or the entire periphery of the condensing lens 20 A groove 211 is formed.
Further, the center of the condensing lens positioning groove 211 is formed so as to coincide with the optical axis of the condensing lens 20.

The sealing glass 22 becomes a molten state at a temperature of 600 ° C. or higher (that is, has a glass transition temperature of 600 ° C. or lower), borosilicate glass (for example, PBO—SiO ₂ —B ₂ O ₃ , PBO). -P ₂ O ₅ -SnF _2, etc.), aluminosilicate glass _{(e.g., Li 2 O-Al 2 O} 3 -SiO 2, B 2 O 3 -Al 2 O 3 low-melting glass selected from -SiO _2), etc. Is used. The sealing glass 22 is not only between the outer peripheral surface of the condensing lens 20 and the sealing member accommodating groove portion 212 of the condensing lens holder 21 but also between the condensing lens positioning groove portion 211 and the outer peripheral surface of the condensing lens 20. The condensing lens 20 and the condensing lens holder 21 are joined airtightly.
A specific method for joining the condenser lens 20 and the condenser lens holder 21 through the sealing glass 22 will be described later with reference to FIGS. 3A to 3D.

The protective glass sealing structure 1 and the condensing lens sealing structure 2 are disposed at the distal end of the housing 7 formed in a cylindrical shape of the laser ignition device 9, and the protective glass sealing structure 1 and the distal end of the housing 7. Are welded and fixed by the welded portion 14.
The distal end side of the housing 7 has a double cylinder structure of an inner cylinder 70 and an outer cylinder 71.

The proximal end surface of the condensing lens sealing structure 2 is in contact with the distal end of the inner cylinder 70, and the distal end surface of the condensing lens sealing structure 2 on the combustion chamber side and the proximal end surface of the protective glass sealing structure 1 are in contact with each other. In contact therewith, the axial position of the condenser lens 20 is fixed.
The housing outer cylinder 71 is formed with a screw portion for fixing to the cylinder head E / H or the like of the internal combustion engine, and is screwed and fixed.

In the present invention, the axial compressive force does not act on the protective glass 10 and the condenser lens 20 from any of the protective glass holder 11, the condenser lens holder 21, the housing inner cylinder 70, and the housing outer cylinder 71, There is no risk of optical axis distortion or cracks.
In addition, amorphous sealing glasses 12 and 22 made of low-melting glass are used as sealing members between the protective glass 10 and the condensing lens 20 and the protective glass holder 11 and the condensing lens holder 21 for accommodating them. Because it is interposed, when the sealing glass 12, 22 is exposed to thermal stress, it absorbs the difference between thermal expansion and contraction with the metal housing 7, protective glass holder 11, and condenser lens holder 21. The effect | action as a buffer member to perform can be exhibited.
Moreover, the sealing glass 12 and 22 completely penetrates into the gap between the protective glass 10 and the protective glass holder 11 and the gap between the condenser lens 20 and the condenser lens holder 21, so that the protective glass holder is protected from the protective glass 10. 11. Since heat dissipation from the condenser lens 20 to the condenser lens holder 21 is improved, the temperatures of the protective glass 11 and the condenser lens 20 can be effectively lowered, and deterioration of the antireflection film can be prevented.

Furthermore, since the optical element is uniformly cooled, the thermal stress is reduced, and the durability of the optical element can be improved.
In addition, since the optical element housing case such as the condensing lens holder 21 that accommodates the optical element such as the condensing lens 20 is made of metal, it can be easily processed with high dimensional accuracy, and the concentrating lens 20 can be collected. The degree of freedom in adjusting the light spot FP is high.

Next, an overview of a laser ignition device 9 using the protective glass sealing structure 1 and the condenser lens sealing structure 2 in the first embodiment of the present invention will be described with reference to FIG. 1B.
In the laser ignition device 9, an excitation light lens 50, a laser resonator 4, a pulsed light expansion lens 30, a condenser lens 20, and a protective glass 10 are disposed at predetermined positions, and are integrally accommodated in a cylindrical housing 7. The pumping light LSR _PMP is introduced through an optical fiber 60 from a pumping light source 80 that is fixed and provided outside.

The front end of the housing 7 is fixed to the engine head E / H of the internal combustion engine, the cylinder wall surface, or the like, and is in a state desired by the combustion chamber CMB via the protective glass 10.
The laser igniter 9 collimates the pumping light LSR _PMP introduced from the pumping light source 80 provided outside through the optical fiber 60 by the pumping light lens 50, irradiates the laser resonator 4, and the Q-switch type laser resonator. 4 oscillates as pulse light LSR _PLS having a high energy density, and once the beam diameter is expanded by the pulse light expansion lens 30, the light collection point FP in the combustion chamber CMB is again formed by the light collection lens 20. By condensing the light, the energy density of the pulsed light LSR _PLS is further increased, and the air-fuel mixture in the combustion chamber CMB is ignited.
The engine control unit ECU 81 transmits an ignition signal IGt in accordance with the ignition timing according to the engine operating condition.

As the excitation light source 80, a known excitation light source including a driver and a laser diode (not shown) is used, and the excitation light LSR _PMP is generated at a predetermined timing according to the ignition signal IGt transmitted from the ECU 81.
The pumping light LSR _PMP transmitted through the optical fiber 60 is collimated by the pumping lens 50 and irradiated to the laser resonator 4.

A known optical element material selected from optical glass, heat-resistant glass, quartz glass, sapphire glass, or the like is used for the excitation light lens 50, and AR that suppresses reflection of the excitation light LSR _PMP on the entrance surface and the exit surface. Coating is applied.
The excitation light lens 50 is accommodated in a cylindrical excitation light lens holder 51 and is sealed and fixed by a sealing glass 52.

Similar to the optical element sealing structures 1 and 2 in the above embodiment, the excitation light lens sealing structure 5 is configured by the excitation light lens 50, the lens holder 51, and the sealing glass 52.
The excitation light lens sealing structure 5 is accommodated on the proximal end side in the cylindrical rear cylinder 72 so that the optical axis thereof coincides with the optical axis of the condensing lens sealing structure 2.
The excitation light lens 50 is provided at a relatively low temperature position on the base end side of the laser ignition device 9 and is not exposed to thermal stress. Therefore, the excitation light lens 50 has a cylindrical shape via annular elastic members above and below the lens. It is good also as a sealing structure used for the general optical element hold | maintained so that it may be inserted | pinched from an up-down direction with a holder.

The laser resonator 4 is a so-called Q-switch type resonator, and an AR coating that suppresses reflection of the excitation light LR _PMP on one end surface of a known laser medium such as Nd: YAG, and excitation light LSR _{PMP with} a short wavelength. Is reflected, and a total reflection mirror that totally reflects long wavelength reflected light is provided.
A known partial reflecting mirror made of Cr: YAG or the like is disposed on the other end face of the laser medium. When the light in the laser medium is below a predetermined Q value, it is totally reflected and exceeds the Q value. A transparent Q switch is formed.
The resonator 4 is accommodated on the distal end side of the cylindrical housing 72.

The pulsed light LSR _PLS oscillated from the resonator 4 is expanded by the pulsed light expansion lens 30.
The pulsed light expansion lens 30 uses a known optical element material selected from optical glass, heat-resistant glass, quartz glass, sapphire glass, and the like, and AR that suppresses reflection of the excitation light LSR _PMP on the incident surface and the output surface. Coating is applied.
Furthermore, a known optical element material selected from optical glass, heat-resistant glass, quartz glass, sapphire glass, and the like is used for the pulse light expansion lens, and reflection of excitation light LSR _PMP is suppressed on the incident surface and the exit surface. AR coating is applied.
The pulsed light expansion lens 30 is housed in a cylindrical pulsed light expansion lens holder 31 and is sealed and fixed by a sealing glass 32.

Similar to the optical element sealing structures 1 and 2 in the above embodiment, the pulsed light expansion lens sealing structure 3 is configured by the pulsed light expansion lens 30, the lens holder 31, and the sealing glass 32.
The optical axis of the pulsed light expansion lens sealing structure 3 coincides with the optical axis of the pulsed light emitted from the resonator 4 and the distance from the light exit surface on the tip side of the resonator 4 is constant. Thus, it is accommodated on the proximal end side of the cylindrical housing inner cylinder 70.

The pulsed light LSR _PLS emitted from the resonator 4 is parallel light rich in straightness, and the beam diameter is expanded by the pulsed light expansion lens 30.
The condensing lens sealing structure 2 is accommodated on the front end side of the housing inner cylinder 70 with a certain distance from the pulsed light expansion lens sealing structure 3.
The beam diameter once expanded by the pulsed light expansion lens 30 is condensed again by the condenser lens 20, so that the energy density of the condensing point FP at a predetermined position in the combustion chamber CMB is increased and introduced into the combustion chamber. Ignition of the mixture is performed.

The protective glass 10 is disposed at the boundary with the combustion chamber CMB, introduces the pulsed light LSR _PLS that has passed through the condensing lens 20 into the combustion chamber CMB, and collects the condensing lens from the high temperature and high pressure in the combustion chamber CMB. 20 is protected.
The protective glass sealing structure 1 of the present invention can reliably prevent chemical components such as air-fuel mixture in the combustion chamber CMB from entering the laser ignition device 9.

Further, the laser ignition device 9 using the optical element sealing structures 1 and 2 according to the present invention includes a portion other than the protective glass sealing structure 1 welded and fixed to the tip of the housing outer cylinder 71 as shown in FIG. 1C. It may be easily disassembled.
When deposits are deposited on the surface of the protective glass 10, it can be easily disassembled and cleaned, and deterioration of the resonator 4, the condensing lens 20, the excitation light expansion lens 30, etc. can be caused by long-term use. Even if it is damaged, it can be replaced very easily.

Further, when the inner cylinder 70, the outer cylinder 71, and the rear cylinder 72 of the housing 7 are assembled and the rear optical element sealing structures 2, 3, and 5 are accommodated in the housing 7, the axial compressive force due to screw tightening. Are received by the optical element housings 21, 31, 51, respectively.
For this reason, even if the inner cylinder 70, the outer cylinder 71, and the rear cylinder 72 are tightened, the tightening pressure does not directly act on the optical elements 20, 30, and 50.

With reference to FIG. 2A, FIG. 2B, FIG. 2C, and FIG. 2D, the specific manufacturing method of the protective glass sealing structure 1 which is the principal part of this invention is demonstrated.
In the sealing glass molded body forming step, a low melting point glass powder constituting the sealing glass 12 is previously filled in a mold having a predetermined cavity and compressed to form a cylindrical sealing glass molded body 12MLD. Is molded.

In the optical element disposing step shown in FIG. 2A, the protective glass 10 processed into a predetermined outer diameter shape with high accuracy, the protective glass engaging portion 110, the protective glass positioning groove portion 111, and the sealing member accommodating groove portion 112 are formed. A protective glass holder 11 and a sealing glass molded body 12MLD are disposed.
The locking portion forming width W ₁₁₀ of the protective glass locking portion 110 may be such that the protective glass 10 does not come off from the protective glass holder 11 during the sealing process. In order to maintain 3 × 10 ¹² W / cm ² , which is a value that allows breakdown within the combustion chamber, for example, it is desirable to be 0.2 mm or less.
It can be changed as appropriate depending on the characteristics of the laser (output, laser quality, wavelength, pulse width) and the characteristics (aberration, focal length) of the condenser lens 20.

The depth T ₁₁₁ of the protective glass positioning groove 111 is not particularly limited as long as the protective glass 10 can be held at the center of the protective glass holder 11, and may be 0.5 mm or more, for example. A clearance GP of 0.01 mm or more and 0.05 mm or less is provided between the protective glass positioning groove 111 and the outer diameter of the protective glass 10.

In the optical element sealing step shown in FIG. 2B, the protective glass holder 11 provided with the protective glass 10 and the sealing glass molded body 12MLD is heated to 600 ° C. or more to melt the sealing glass molded body 12MLD.
The sealing glass 12 in a molten state penetrates into the gap GP between the outer peripheral surface of the protective glass 10 and the protective glass positioning groove 111 by capillary action.

When the sealing glass 12 once melted is cooled and solidified, the protective glass 10 and the protective glass holder 11 are completely joined.
Note that the metal material such as Kovar used for the protective glass holder 11 forms an oxide film when heated to 650 ° C. or higher, and this film melts with the sealing glass 12, thereby improving the one-phase and sealing properties.

Next, in the winding and tightening step shown in FIG. 2C, a metal backup ring 13 having a thermal expansion coefficient close to that of the protective glass such as Kovar in the protective glass holder 11 to which the protective glass 10 is sealed and fixed. Is disposed, and the tightening portion 113 is wound and the backup ring 13 is elastically pressed and fixed.
At this time, the tightening portion 113 is made to act on the starting point for bending the tightening portion 113 with a pressing force in the direction from the inside to the outside of the backup ring 13, and the winding tightening portion 113 is wound in the inner diameter direction using that position as a fulcrum. By bending in this way, it is possible to prevent the compressive force in the axial direction from acting on the protective glass 10 as much as possible.
The pressing force of the tightening portion 113 acts on part of the surface of the first application side of the protective glass 10 through the backup ring 13, but the airtightness is ensured by the sealing glass 12, and the protective glass 10 is dropped off. As long as it can be prevented, a strong pressing force is not required, and the protective glass 10 is not damaged by compression.
Moreover, since the backup ring 13 and the protective glass 10 abut on the inner side of the inner diameter of the sealing glass 12, the elastic pressing force of the backup ring 13 does not act on the sealing glass 12, and the sealing glass 12 is broken. Will not be invited.
Through the above steps, a protective glass sealing structure 1 as shown in FIG. 2D is completed.

With reference to FIG. 3A, FIG. 3B, FIG. 3C, and FIG. 3D, the manufacturing method of the condensing lens sealing structure 2 is demonstrated.
Basically, it is the same as the manufacturing method of the protective glass sealing structure 1.

In the present embodiment, a sealing glass molded body 22MLD in which sealing glass powder is formed in a cylindrical shape is prepared in advance, and in the optical element disposing step shown in FIG. 3A, the condenser lens 20 and the sealing glass molded body are prepared. 22MLD is disposed in the condensing lens holder 21 in which the predetermined condensing lens positioning groove 211 and the sealing glass housing groove 212 are formed.
In the sealing glass heating and fusing step shown in FIG. 3B, the sealing glass molded body 22MLD is heated and melted, and the condenser lens 20 and the condenser lens holder 21 are joined through the sealing glass 22.

As described above, as shown in FIGS. 3C and 3D, the condensing lens filled with the sealing glass 22 and sealed and fixed to the condensing lens holder 21 so as to cover the entire outer periphery of the condensing lens 20. The sealing structure 2 is completed.
The size of the locking portion forming width W _{210 of} the condensing lens locking portion ₂₁₀ , the groove portion forming depth T _{211 of} the condensing lens positioning groove portion 211, and the clearance GP are the same as in the case of the protective glass holder 11.

Since it is separated from the combustion chamber CMB by the protective glass sealing structure 1, the gas in the combustion chamber CMB does not enter the inside of the housing 7, and the heat in the combustion chamber CMB is also protected. Since it is blocked to some extent by the glass sealing structure 1, the condensing lens sealing structure 2 does not need to be as airtight and heat resistant as the protective glass sealing structure 1.
For this reason, it is not necessary to wind the backup ring around the condensing lens sealing structure 2.

Further, it is not always necessary to dispose the sealing glass 22 over the entire outer periphery of the condenser lens 20, and the outer periphery of the condenser lens 20 is not provided as in the condenser lens sealing structure 2a shown in FIG. 3E. Sealing glass 22a may be disposed at a plurality of locations and sealed and fixed.
In this case, the sealing glass molded body 22aMLD is formed in a pellet shape and placed in a plurality of sealing glass accommodation grooves provided in the condenser lens holder 21a.
Even if the sealing glass 22a is not provided over the entire outer periphery of the condenser lens 20, when the sealing glass molded body 22aMLD is heated and melted, the outer periphery of the condenser lens 20 and the condenser lens holder 21a. Can be sufficiently penetrated by capillary action.
In addition, the shape of the sealing glass moldings 22MLD and 22aMLD is not particularly limited. According to the shape of the sealing glass accommodating groove 212, a prismatic shape, a polygonal columnar shape, a columnar shape, a cylindrical shape, a fan column shape, and a semicircular shape. The columnar shape can be changed as appropriate.

Next, as shown in FIG. 4A, the condenser lens sealing structure 2 and the protective glass sealing structure 1 are accommodated from the front end side of the housing 7.
At this time, the distance between the front end surface 702 of the inner cylinder 70 and the protective glass sealing structure housing groove 712 provided in the outer cylinder 71 is set to a height at which the condensing lens sealing structure 2 just fits.
In such a state, the condensing lens sealing structure 2 is accommodated, and the protective glass sealing structure 1 is fixed, so that the axial compressive force does not act on the condensing lens sealing structure 2, and the position It can be fixed without causing displacement.

Further, as shown in FIG. 4B, the welded portion 14 is placed on the entire circumference of the distal end portion 713 using welding means such as laser welding between the distal end portion 713 of the housing outer cylinder 70 and the outer periphery of the protective glass sealing structure 1. The housing outer cylinder 71 and the protective glass sealing structure 1 are integrated.
The extended lens sealing structure 3, the laser resonator 4, and the excitation light lens sealing structure 5 are appropriately housed in the housing 7 in the order of the exploded view shown in FIG. 1C.
Thus, the laser ignition device 9 using the optical element sealing structures 1 and 2 of the present invention is completed.

Here, the test results conducted by the present inventors in order to confirm the effects of the present invention will be described.
As an evaluation sample, the protective glass sealing structure 1 and the condensing lens sealing structure 2 of the present invention prepared according to the above-described manufacturing method were housed and fixed in the housing 7, and the conventional protective glass was used as the housing. Comparative Example 1 fixed by crimping to the tip of each was prepared, and pressure resistance and heat resistance were evaluated.
In the pressure resistance evaluation method, a pressure vessel simulating a combustion chamber is prepared, attached so that the tip of the housing provided with the protective glass of each sample is exposed in the pressure chamber, and the pressure in the pressure chamber is changed from 0 to 30 MPa. The test was repeated 10 ⁶ times.

The thermal shock resistance evaluation method was evaluated by immersing the sample in a tin bath heated to 500 ° C. and observing the subsequent change.
As a result, in Example 1 of the present invention, no change was observed after the pressure resistance evaluation test and after the thermal shock resistance evaluation test.

On the other hand, in Comparative Example 1, the protective glass was loosened after the pressure resistance evaluation test, and pressure gas leaked into the housing.
Moreover, in the comparative example 1, as a result of the thermal shock resistance test, there were some which caused cracks in the protective glass.
In Comparative Example 1, a defect occurred in 1 out of 5 samples, but in Example 1, no defect occurred at all.

With reference to FIG. 5, the modified example 1a of the protective glass sealing structure in the first embodiment, the modified example 2a of the condensing lens sealing structure, the modified example 71a of the housing outer cylinder, and these were adopted. A modification 9a of the laser ignition device will be described.
In the above embodiment, the example in which the groove heights T ₁₁₁ and T ₂₁₁ of the optical element positioning grooves ₁₁₁ and ₂₁₁ are set to about 0.5 mm is shown. However, the upper limit is not particularly limited, and as shown in FIG. In addition, the groove heights T ₁₁₁ and T ₂₁₁ may be set to be half or more of the thickness of the optical elements 10 and 20, and the thickness of the sealing glass 12a and 22a may be reduced.

Even if it is such a structure, when sealing glass 12a, 22a is heat-melted, it will be the same as that of the said embodiment as long as it penetrate | infiltrates also into the clearance gap between optical element 10a, 20 and each holder 11a, 21a. The effect can be demonstrated. In the above embodiment, as shown in FIG. 1A, the surface of the protective glass 10 and the surface of the sealing glass 12 are substantially flush with each other. The surface of the protective glass 10a may be formed to be thick so that the surface of the protective glass 10a is flush with the tightening portion 113a or protrudes to the combustion chamber CMB side of the tightening portion 113a.
In the present embodiment, the winding tightening portion 113a tightens the backup ring 13a so as to press in the outer diameter direction, so that pressure is applied to the protective glass 10a during the manufacturing process, or the protective glass holder 11a. It is difficult to act on the pressure due to thermal expansion.

By adopting such a configuration, in addition to the above effects, no stagnation part of the airflow generated in the combustion chamber is formed between the surface of the protective glass 10a and the tightening part 113. Can be suppressed. Further, in the housing outer cylinder 71a, the screw portion 711a for fixing to the engine head E / H is formed only further to the base end side than the base end position of the condenser lens sealing structure 2a.
For this reason, the screw tightening pressure acting in the axial direction when the housing outer cylinder 71a is screwed and fixed to the engine head E / H does not act on the condensing lens sealing structure 2a and the protective glass sealing structure 1a at all. .
For this reason, in addition to the effect similar to the said embodiment, the shift | offset | difference of the optical axis by the influence of residual stress, etc. can be suppressed.

With reference to FIG. 6A, FIG. 6B, FIG. 7A, FIG. 7B, and FIG. 7C, the optical sealing structure 2b and the laser ignition device 9b in the 2nd Embodiment of this invention are demonstrated.
In the above-described embodiment, the optical sealing structures 1 and 2 and the laser ignition device 9 and its modifications 1a, 2a, and 9a for condensing the pulsed light LSR _PLS at one location in the combustion chamber CMB. As described above, the present embodiment is different in that the condensing points FP are formed at a plurality of locations in the combustion chamber CMB.

In the present embodiment, as an example of the laser ignition difference 9b, the example in which the condensing points FP are formed at three locations in the combustion chamber CMB is shown. However, in the present invention, the number of the condensing points FP is arbitrarily set. Is possible.
Since each optical element used in the present invention is formed in a cylindrical shape with a simple outer peripheral shape, the holder is provided with a locking portion, a positioning groove portion, and a sealing glass accommodating groove portion according to the number of each optical element. In addition, since the optical element and the sealed glass molded body can be accommodated, melted by heating, and sealed and fixed, the number of optical elements can be easily increased or decreased.

As shown in FIGS. 6A and 6B, in this embodiment, a plurality of condenser lenses 20b are accommodated in a condenser lens holder 21b, and each condenser lens 20b is sealed and fixed with a sealing glass 22b. I have to.
In the present embodiment, since the outer peripheral shape of the plurality of condensing lenses 20b is formed in a simple cylindrical shape, it is processed far more than when an integrated condensing lens having a plurality of condensing points is formed. Is easy.

Also in this embodiment, as in the above embodiment, a certain range of one end surface of the condenser lens 20b is locked to the condenser lens locking portion 210b and the condenser lens positioning groove portion 21b provided in the condenser lens holder 21b. Therefore, the condenser lens 20b can be fixed at a predetermined position in the condenser lens holder 21b with high accuracy.
Further, a positioning hole 213 for inserting the knock pin 24 is formed in the condenser lens holder 21b.

As shown in FIG. 7A, when the condensing lens sealing structure 2b is accommodated in the housing outer cylinder 71, the knock pin 24 is positioned in the positioning hole 213 of the condensing lens holder 21b and the positioning hole 703 provided in the housing inner cylinder 70b. And the optical axis centers C / L of the plurality of condenser lenses 20b held by the condenser lens holder 21b are respectively inserted into the optical axis centers of the pulsed light LS _RPL emitted from the laser resonator 4. It can be easily matched with C / L.
As shown in FIG. 7C, each of the plurality of pulsed light expansion lenses 30b, the accommodated expansion lens sealing structure 3b, and the excitation light lens sealing structure 5b that accommodates and fixes the plurality of excitation light lenses 50b are also knock pins. By using the same positioning method as that of the condensing lens sealing structure 2b, the optical axis centers C / L are provided so as to coincide with each other.

In the above embodiment, an example in which a plurality of pumping light LSR _PMPs are incident on one laser resonator 4 and the pulsed light LSR _PLS is emitted at the respective positions on the central axis is shown in FIG. As shown in FIG. 5, a plurality of laser resonators 40b may be provided independently for each pumping light LSRP _PLS .
At this time, the laser resonator 40b is formed in a cylindrical shape like other optical elements, and the laser resonator is provided with a laser resonator locking portion, a laser resonator positioning groove portion, and a sealing glass accommodating groove portion at a plurality of locations. After forming the laser resonator sealing structure 4b accommodated in the cavity holder 41b and sealed and fixed via the sealing glass 42b made of low melting point glass, the laser resonator sealing structure 4b is accommodated in the housing 72, and the knock pin 44 is used. Similarly to the other optical element sealing structures, the optical axis centers C / L of the laser resonators 40b may be matched.

According to the present embodiment, as shown in FIG. 7B, the pulsed light LSR _PLS having a high energy density can be condensed at a plurality of condensing points FP at the same time, and further stable ignition can be realized.
As shown in FIG. 7C, in the present embodiment, a plurality of excitation lights LSR _PMP are emitted from the excitation light source 80b and introduced into the laser ignition device 9b via the plurality of optical fibers 60b.

With reference to FIG. 8A and FIG. 8B, the modification 2c of the optical element sealing structure in the 2nd Embodiment of this invention is demonstrated.
In the embodiment 2c, the sealing glass molded body 22MLD formed in an annular shape is disposed so as to cover the outer periphery of the condenser lens 20c, and this is heated and melted to form the sealing glasses 22c and 210c. However, in this embodiment, the sealing glass molded body 22MLD formed in a pellet shape is disposed between the plurality of optical elements 20c, and this is heated and melted.

  Even if the sealing glass molded body 22MLD is not arranged so as to cover the entire circumference of the condensing lens 20c as in the present embodiment, when the sealing glass 22 is melted, the condensing occurs due to capillary action. By flowing into the gap GP between the lens 20c and the condenser lens holder 21c, the condenser lens 20c and the condenser lens holder 21c can be hermetically sealed.

With reference to FIG. 9A, FIG. 9B, and FIG. 9C, another modified example 2d of the condensing lens sealing structure will be described.
In the present embodiment, as shown in FIG. 9A, sealing glass disposition grooves 212d are formed at a plurality of locations.

Furthermore, as shown in the left half of FIG. 9A and FIG. 9B, sealing glass molded bodies 22MLDd formed in triangular prism shapes of different sizes are arranged, and as shown in the right half of FIG. 9A and FIG. The glass stop 22MLDd is heated and melted.
When the sealing glass molding 22MLDd is melted, it spreads in the sealing glass disposition groove 212d so as to cover the periphery of the condensing lens 20d, and the condensing lens 20d is integrated into the condensing lens holder 21d. Can be fixed to.

As shown in the present embodiment, molding the sealing glass molded body MLDd into triangular prism-shaped pellets facilitates the molding, and also facilitates the automation of the work that is disposed between the plurality of condenser lenses 20d. It becomes.
In the present embodiment, considering the ease of arrangement, ease of spreading when heated and melted, the sealing glass molded body 22MLDd is as high as the depth of the sealing glass disposing groove 212d. Although the example which formed in this triangular prism shape was shown, the magnitude | size and shape of sealing glass molded object 22MLDd can be changed suitably.

1 Protective glass sealing structure (optical element sealing structure)
10 Protective glass (optical element)
11 Protective Glass Holder (Optical Element Housing) 110 Protective Glass Locking Section (Optical Element Locking Section)
111 Protective glass positioning groove (optical element positioning groove)
112 sealing glass housing groove 113 winding fastening part 12 sealing glass 13 backup ring 14 laser welding part 2 condensing lens sealing structure (optical element sealing structure)
20 Condensing lens (optical element)
21 Condensing lens holder (optical element housing)
22 Sealing glass 3 Extended lens sealing structure (optical element sealing structure)
30 Expansion lens (optical element)
31 Extended lens holder (optical element housing)
32 Sealing glass 4 Resonator (Q switch)
5 Excitation light lens sealing structure (optical element sealing structure)
50 Excitation light lens (optical element)
51 Excitation light lens holder (optical element housing)
52 Sealing glass 60 Optical fiber 7 Housing 70 Inner cylinder 701 Pulse light passage hole 71 Outer cylinder 711 Outer cylinder screw part 72 Rear cylinder 73 Cooling cylinder 80 Excitation light source (LD)
81 Ignition control unit (ECU)
GP element housing gap LSR _PMP excitation light LSR _PLS pulse light FP Focusing point

Claims (10)

One or a plurality of optical elements (10, 10a, 20, 20a, 20b, 20c) are accommodated inside the optical element housing (11, 11a, 21, 21a, 21b, 21c) and sealed. A stop structure,
The optical element housing (11, 11a, 21, 22a, 22b, 22c)
An optical element locking portion (110, 210) with which one end face of the optical element (10, 10a, 20, 20a, 20b, 20c) abuts,
Optical element positioning groove portions (111, 111a, 211, 211a, 211b, 211c) formed by providing a predetermined gap (GP) with respect to the outer periphery of the optical elements (10, 10a, 20, 20a, 20b, 20c) )When,
In order to dispose sealing glass (12, 12a, 22, 22a, 22b, 22c) so as to cover a part or the entire periphery of the outer periphery of the optical element (10, 10a, 20, 20a, 20b, 20c), A sealed glass housing groove (112, 112a, 212, 212a, 212b, 212c) that has been drilled;
The sealing glass (12, 12a, 22, 22a, 22b, 22c) is made of a low melting point glass having a glass transition temperature of 600 ° C. or less,
By sealing the sealing glass (12, 12a, 22, 22a, 22b, 22c), the optical element (10, 10, 20, 20a, 20b, 20c) and the optical element housing case (11, 11a, 21). , 22a, 22b, 22c) are hermetically sealed (1, 1a, 2, 2a, 2b, 2c)   The optical element sealing structure (1, 1a, 2, 2a, 2b, 2c) according to claim 1, wherein the gap (GP) is in a range of 0.01 mm to 0.05 mm.   The optical element sealing structure (1, 1a, 2, 2a, 2b, 2c) according to claim 1 or 2, wherein an outer periphery of the optical element (10, 10a, 20, 20a, 20b, 20c) is formed in a cylindrical shape. ) The sealing glass is borosilicate glass (PBO—SiO ₂ —B ₂ O ₃ , PBO—P ₂ O ₅ —SnF ₂ ), aluminosilicate glass (Li ₂ O—Al ₂ O ₃ —SiO ₂ , B _{2 O 3 -Al 2 O 3 -SiO} 2) optical element sealing structure according to any one of claims 1 to 3 which is a low melting glass selected from either (1,1a, 2,2a, 2b 2c) The optical element (10, 10a) is a protective glass (10, 10a) that protects the condenser lens (20, 20a, 20b, 20c) from pressure, heat, and chemical components in a combustion chamber, and includes quartz and sapphire. , Ruby, CaF ₂ , BaF ₂ , MgF ₂ , LiF, YAG, ZnSe made of a heat-resistant optical material, and the optical element housing case is a protective glass holder that houses the protective glass 5. The optical device according to claim 1, wherein the optical material is made of a metal material selected from any one of an iron cobalt nickel alloy (Kovar) and an iron nickel alloy (42 alloy) having a thermal expansion coefficient close to that of the heat resistant optical material. Element sealing structure (1, 1a) The optical element is the condensing lens (20, 20a, 20b, 20c) that condenses the excitation light into a combustion chamber, and is made of heat-resistant glass such as borosilicate glass, quartz, sapphire, ruby, CaF ₂ , Condensation made of a heat-resistant optical material selected from BaF ₂ , MgF ₂ , LiF, YAG, and ZnSe, and the optical element housing housing the condenser lenses (20, 20 a, 20 b, and 20 c). A lens holder having a thermal expansion coefficient close to that of the heat-resistant optical material, selected from a metal material selected from any of stainless steel (NS-5), iron cobalt nickel alloy (Kovar), and iron nickel alloy (42 alloy) The optical element sealing structure (2, 2a, 2b, 2c) according to any one of claims 1 to 4 The protective glass sealing structure (1, 1a), wherein the protective glass holder (11, 11a) includes a tightening portion (113) extending to the combustion chamber side,
Between the tightening portion (113) and the sealing glass (12),
Elasticity selected from stainless steel (NS-5), iron-cobalt-nickel alloy (Kovar), or iron-nickel alloy (42 alloy), which has a thermal expansion coefficient close to that of the low-melting glass constituting the sealing glass (12) An annular backup ring (13) made of a metal material is provided, and the tightening portion (113) is tightened so as to be wound around the backup ring (13) to prevent the protective glass (10) from falling off. The optical element sealing structure (1, 1a, 1b, 1c) according to claim 5 A method for producing an optical element sealing structure (1, 1a, 2, 2a, 2b) according to any one of claims 1 to 7,
at least,
A sealing glass molded body forming step of forming a sealed glass molded body (12 MLD, 22 MLD) by pressing and hardening a low melting glass powder having a glass transition temperature of 600 ° C. or lower;
An optical element locking portion (110, 210) with which one end face of the optical element (10, 10a, 20, 20a, 20b, 20c) contacts, and the optical element (10, 10, 20, 20a, 20b, 20c) Of the optical element positioning grooves (111, 111a, 211, 211a, 211b, 211c) provided with a predetermined gap (GP) with respect to the outer periphery of the optical element (10, 10a, 20, 20a, 20b, 20c) Optical element housing cases (11, 11a, 21, 21a, 21b) provided with sealing glass housing grooves (112, 112a, 212, 212a, 212b, 212c) so as to cover a part or the entire circumference of the outer periphery. 21c) and the sealing glass molded body (12MLD, 22MLD), an optical element disposing step of disposing in order,
The sealing glass molded body (12MLD, 22MLD) disposed in the sealing glass housing groove (112, 112a, 212, 212a, 212b, 212c) is heated and melted at a temperature of 600 ° C. or higher to obtain the optical element (10 10a, 20, 20a, 20b, 20c) and an optical element sealing step for hermetically sealing the optical element housing (11, 11a, 21, 21a, 21b, 21c). Method for manufacturing optical element sealing structure As an optical element,
One or a plurality of excitation light lenses (50) that use one or a plurality of excitation light (LSR _PMP ) introduced from an excitation light source (80, 80b) provided outside as parallel light;
A Q-switch type laser resonator (40, 40b) for resonantly amplifying the excitation light (LSR _PMP ) collimated by the excitation light lens (50) and emitting pulsed light (LSR _PLS ) having a high energy density;
One or a plurality of expansion lenses (30, 30b) for expanding the pulsed light (LSR _PLS ) emitted from the resonator (40, 40b);
One or a plurality of condensing lenses (20) for condensing the pulsed light (LSR _PLS ) expanded by the expansion lenses (30, 30b) at one or a plurality of predetermined positions (FP) in the combustion chamber (CMB) of the internal combustion engine. 20b, 20b),
And a protective glass (10, 10a) for protecting the condenser lens (20, 20a, 20b, 20c), which is desired in the combustion chamber (CMB) of the internal combustion engine, and these optical elements (10, 10a, 20, 20a, 20b, 20c, 30, 30b, 40, 40b, 50, 50b)
At least the protective glass (10, 10a) and the condenser lens (0, 20a, 20b, 20c) are the optical element sealing structures (1, 1a, 2, 2a, 2b, 2c) as a single unit in a cylindrical housing (7),
Laser ignition devices (9, 9a, 9b, 9c) for condensing the air-fuel mixture by focusing pulsed light (LSR _PLS ) with high energy density on the air-fuel mixture introduced into the combustion chamber (CMB)   The laser ignition device (9, 9a, 9b, 9c) according to claim 9, wherein the protective glass sealing structure (1, 1a) and the housing (7) are hermetically sealed by laser welding.

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