WO2018079138A1 - Lens barrel-integrated lens for ignition plug and production method therefor - Google Patents

Abstract

The present invention provides a lens barrel-integrated lens that is capable of stably fixing a glass lens within a metal holder even when exposed to high temperatures while an internal combustion engine is being driven. This lens barrel-integrated lens for a combustion-based internal combustion engine is characterized by being provided with a cylindrical metal holder having openings at both ends; and a glass lens fixed within the metal holder by a clamping force of the metal holder, wherein the metal holder has a heat expansion coefficient higher than that of the glass lens.

Description

Lens barrel-integrated lens for spark plug and manufacturing method thereof

The present invention relates to a spark plug mirror used for optically igniting an air-fuel mixture by concentrating high energy light on the air-fuel mixture filled in a combustion chamber in a combustion internal combustion engine such as an automobile engine. The present invention relates to a cylinder-integrated lens.

Conventionally, an ignition plug of an internal combustion engine such as an automobile engine has been used to ignite with electric discharge or red hot metal. However, with such a spark plug, the ignition position cannot be controlled, and ignition is performed toward the upper end of the air-fuel mixture, so that it is difficult to efficiently burn.

Therefore, laser spark plugs are attracting attention as a method for improving the fuel efficiency of internal combustion engines. Since the laser beam can control the condensing position, it can control the ignition position, and it can also ignite a plurality of places instead of one place, so that the combustion efficiency is increased. Here, use of a lens barrel-integrated lens has been studied as a member for condensing laser light (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 2015-1158

In the lens barrel-integrated lens of Patent Document 1, in order to fix the glass lens in the metal holder, the glass lens and the metal holder are joined with low melting point glass. Of course, in the lens barrel-integrated lens, the air-fuel mixture burns and is exposed to high temperatures while the internal combustion engine is driven. When exposed to high temperatures, the low-melting glass is softened, and the position (optical axis) of the glass lens is shifted, resulting in a problem that desired ignition performance cannot be obtained.

The present invention has been made in view of such circumstances, and a spark plug barrel that can stably fix a glass lens in a metal holder even when exposed to high temperatures during driving of an internal combustion engine. An object is to provide an integrated lens.

A lens barrel-integrated lens for a spark plug according to the present invention includes a cylindrical metal holder having openings at both ends, and a glass lens fixed in the metal holder by a clamping force of the metal holder. The coefficient is higher than the thermal expansion coefficient of the glass lens. The lens barrel-integrated lens for a spark plug of the present invention is excellent in heat resistance because it does not use a low melting point sealing material. In the present invention, “the tightening force of the metal holder” means a force that the metal holder tends to contract in the axial direction (inward).

In the lens barrel-integrated lens of the present invention, the thermal expansion coefficient (30 to 300 ° C.) of the metal holder is 1 to 150 × 10 ⁻⁷ / ° C. higher than the thermal expansion coefficient (30 to 300 ° C.) of the glass lens. Is preferred.

In the lens barrel-integrated lens for a spark plug of the present invention, it is preferable that the glass lens has a thickness of 1 mm and an internal transmittance of 90% or more in a wavelength range of 400 to 1500 nm. If it does in this way, it will become easy to permeate | transmit a laser beam efficiently.

In the lens barrel-integrated lens for a spark plug of the present invention, the glass lens preferably has a strain point of 400 ° C. or higher. In this way, the lens shape is difficult to change even when exposed to high temperatures.

In the lens barrel-integrated lens for a spark plug according to the present invention, the glass lens preferably has a refractive index (nd) of 1.45 to 2.30 and an Abbe number (νd) of 35 to 45.

In the lens integrated with a spark plug of the present invention, the glass lens ^{preferably has} ΔT = (temperature at 10 ^0.5 poise−liquidus temperature) of 20 ° C. or more.

In the spark plug barrel-integrated lens of the present invention, the glass lens is preferably made of B ₂ O ₃ —ZnO—La ₂ O ₃ —Gd ₂ O ₃ glass.

In the lens barrel-integrated lens of the present invention, the glass lens has a composition of B ₂ O ₃ 5 to 45%, ZnO 10 to 45%, La ₂ O ₃ 5 to 25%, Gd ₂ O by mass%. ₃ It is preferable to contain 0.5 to 24%.

The lens barrel-integrated lens of the present invention has a La ₂ O ₃ , Gd ₂ O _3, and ZnO content of 0.1 ≦ (La ₂ O ₃ + Gd ₂ O ₃ ) / ZnO on a mass% basis. It is preferable that the relationship is ≦ 5.0.

The method for manufacturing a lens barrel-integrated lens for a spark plug according to the present invention includes a step of placing and heating a glass lens glass material having an outer diameter smaller than the inner diameter of the metal holder in the metal holder, and the glass lens glass material is in close contact with the metal holder. And a step of pressing the glass lens glass material so as to have a predetermined lens shape and a step of cooling to room temperature.

A lens barrel-integrated lens for a spark plug according to the present invention includes a cylindrical metal holder having openings at both ends, and a glass lens fixed in the metal holder.

According to the present invention, it is possible to provide a lens barrel-integrated lens capable of stably fixing a glass lens in a metal holder even when exposed to a high temperature during driving of an internal combustion engine.

It is typical sectional drawing which shows the basic structure of a laser spark plug. 1 is a schematic cross-sectional view showing an embodiment of a lens barrel-integrated lens for a spark plug according to the present invention. It is typical sectional drawing which shows the manufacturing process of the lens-barrel integrated lens for ignition plugs of this invention.

First, the principle and structure of the laser spark plug will be described with reference to FIG. The laser light is introduced into the collimating lens 1 as diffused light via, for example, an optical fiber. The introduced diffused light is collimated by the collimating lens 1. The collimated light transmitted through the collimating lens 1 is emitted after being amplified by resonance by the resonator 2 and is diffused by the diffusion lens 3. The diffused light that has passed through the diffusion lens 3 is condensed by the condenser lens 4 and ignited to the air-fuel mixture in the fuel chamber of the internal combustion engine. The cover glass 5 protects the condenser lens 4 and the like from heat, dirt, and the like. For the cover glass 5, a heat-resistant material such as quartz or sapphire can be used. The lens-integrated lens for a spark plug of the present invention can be used for any of the collimating lens 1, the diffusion lens 3, and the condenser lens 4.

Hereinafter, embodiments of a lens barrel-integrated lens for a spark plug according to the present invention will be described.

FIG. 2 is a schematic cross-sectional view showing an embodiment of a lens barrel-integrated lens for a spark plug according to the present invention.

In this embodiment, a lens barrel-integrated lens 10 for a spark plug includes a cylindrical metal holder 12 having openings at both ends, and a glass lens 11 fixed in the metal holder 12 by the tightening force of the metal holder 12. It has. The metal holder 12 may have a flange portion in order to stably store the glass.

The following explains each component.

(Glass lens 11)
The glass lens 11 has a lens shape. The lens shape is not particularly limited, but considering a light collecting ability, a biconvex shape (for example, a spherical shape), a plano-convex shape, and a meniscus shape are preferable.

The glass lens 11 is preferably made of B ₂ O ₃ —ZnO—La ₂ O ₃ —Gd ₂ O ₃ glass. B ₂ O ₃ —ZnO—La ₂ O ₃ —Gd ₂ O ₃ glass has a high refractive index and excellent devitrification resistance.

B ₂ O ₃ —ZnO—La ₂ O ₃ —Gd ₂ O ₃ glass has a composition of B ₂ O ₃ 5 to 45% by mass, ZnO 10 to 45%, La ₂ O ₃ 5 to 25% by mass, It preferably contains 0.5 to 24% of Gd ₂ O ₃ . The reason for limiting the glass composition range in this way will be described below. In the description of the content of each component below, “%” means “% by mass” unless otherwise specified.

B ₂ O ₃ is a skeletal component of glass and is effective in improving devitrification resistance. B ₂ O ₃ also has an effect of lowering the basicity of the glass, and is effective in preventing fusion between the glass and the mold in mold press molding. The content is preferably 5 to 45%, 8 to 29%, 10 to 24%, particularly 12 to 21%. When B ₂ O ₃ exceeds 45%, the chemical durability of the glass is lowered, and the weather resistance is remarkably deteriorated. If it is less than 5%, the Abbe number among the optical constants cannot be sufficiently secured, the devitrification resistance is lowered, and it becomes difficult to obtain glass stably.

ZnO is a component that can increase the refractive index and chemical durability. Further, glass containing a large amount of B ₂ O ₃ and La ₂ O ₃ tends to devitrify, but ZnO has an effect of suppressing this. Its content is 10 to 45%, preferably 15.5 to 30%, more preferably 16 to 21%, and still more preferably 16 to 20%. If ZnO exceeds 45%, the phase separation tendency of the glass becomes strong, and it becomes difficult to obtain a homogeneous glass. If it is less than 10%, the refractive index is lowered, the devitrification suppressing effect cannot be obtained, the liquidus temperature rises, and the working temperature range cannot be sufficiently secured.

La ₂ O ₃ is a component for securing a sufficient working temperature range, and has an effect of increasing the refractive index. Furthermore, there is an effect of improving weather resistance. However, if a large amount is added in order to obtain a high refractive index, devitrification increases, so that it is necessary to partially replace it with Gd ₂ O ₃ or the like. The content of La ₂ O ₃ is 5 to 25%, preferably 7 to 24.5%, more preferably 9 to 24.2%. When La ₂ O ₃ exceeds 25%, the devitrification becomes high and the liquidus temperature rises, so that workability is greatly reduced. If it is less than 5%, the refractive index tends to decrease and the weather resistance tends to deteriorate.

Since Gd ₂ O ₃ is a component that increases the refractive index, it is not necessary to contain a large amount of La ₂ O _3, which is effective in improving devitrification resistance. Gd ₂ O ₃ also has an effect of improving devitrification resistance, and is a component that can expand the working temperature range. However, when it is contained in a large amount, the phase separation tendency of the glass becomes strong, and a homogeneous glass is obtained. It becomes difficult, that is, the working temperature range is reduced. The content of Gd ₂ O ₃ is 0.5 to 24%, preferably 1 to 21%, 1 to 20%, 1 to 15%, 2 to 10%, more preferably 3 to 9.5%.

In addition, the content of La ₂ O ₃ and Gd ₂ O ₃ is limited for the purpose of maintaining high devitrification resistance and ensuring a wide working temperature range, while ZnO is used for the purpose of ensuring a high refractive index. Contains a large amount. In order to achieve both high devitrification resistance and a high refractive index, it is important to keep the contents of La ₂ O ₃ , Gd ₂ O ₃ and ZnO in an appropriate balance. From this point of view, the values of (La ₂ O ₃ + Gd ₂ O ₃ ) / ZnO are 0.1 to 5.0, 0.1 to 4.5, 0.2 to 4.0, 0.3 on a mass% basis. It is preferable to adjust to be in the range of -3.0, particularly 0.5-2.5. By setting this value to 0.1 to 5.0, high devitrification resistance can be maintained without lowering the refractive index. When this ratio increases, the devitrification resistance decreases, and when it decreases, the refractive index tends to decrease.

In addition to the above components, the following components can be contained.

SiO ₂ is a component constituting the skeleton of the glass, and has the effect of improving the devitrification resistance and expanding the working range. It also has the effect of improving weather resistance. The content is preferably 0 to 20%, 1 to 15%, particularly preferably 2 to 10%. When SiO ₂ exceeds 20%, the refractive index is remarkably lowered and the strain point tends to be high.

Li ₂ O is effective in improving devitrification resistance, and its content is preferably 0 to 10%, 0.1 to 5%, particularly preferably 0.5 to 4%. When Li ₂ O exceeds 10%, the liquidus temperature is remarkably increased, the working temperature range is narrowed, and the mass productivity is adversely affected. Moreover, there exists a tendency for a weather resistance to deteriorate remarkably.

Ta ₂ O ₅ has an effect of increasing the refractive index, chemical durability and resistance to devitrification, and its content is preferably 0 to 20%, 0.5 to 15%, particularly preferably 1 to 10%. . If Ta ₂ O ₅ exceeds 20%, the Abbe number decreases, making it difficult to obtain desired optical characteristics and increasing the cost.

ZrO ₂ is a component that increases the refractive index. Moreover, since glass is formed as an intermediate oxide, there is an effect of improving devitrification resistance and chemical durability. However, when the content of ZrO ₂ increases, the strain point increases and the press formability deteriorates. The content of ZrO ₂ is preferably 0 to 15%, 0.5 to 10%, particularly 1 to 8%.

Y ₂ O ₃ is a component that increases the refractive index. For this reason, devitrification resistance can be improved by substitution with La ₂ O ₃ . Further, by adding an appropriate amount, there is an effect of suppressing phase separation that tends to occur in the B ₂ O ₃ —ZnO—La ₂ O ₃ glass. The content is preferably 0 to 15%, 1 to 10%, particularly 2 to 8%. When Y ₂ O ₃ exceeds 15%, devitrification becomes high and the working temperature range becomes narrow.

WO ₃ has the effect of increasing the refractive index. Further, since glass is formed as an intermediate oxide, there is an effect of improving devitrification resistance. The content of WO ₃ is preferably 0 to 5%, 0.5 to 4%, particularly 1 to 3.5%. If WO ₃ exceeds 5%, the Abbe number decreases, making it difficult to obtain desired optical characteristics. Excessive addition causes a decrease in transmittance, increases the affinity with a press die, and causes fusion with the die during pressing.

The content of Nb ₂ O ₅ which is a component for increasing the refractive index is preferably 0 to 15%, 0.5 to 10%, particularly 1 to 8%. When Nb ₂ O ₅ exceeds 15%, devitrification becomes high and the working temperature range becomes narrow.

In addition to the above, various components can be added. For example, Sb ₂ O ₃ can be added as a fining agent. Note To avoid excessive coloring to the glass, the content of Sb ₂ O ₃ is preferably 1% or less.

The content of Fe ₂ O ₃ is preferably 5 to 1000 ppm. When the content of Fe ₂ O ₃ is too large, there is a possibility of damage by heat generated by absorbing the laser light irradiated. Therefore, it is preferably 10,000 ppm or less, 500 ppm or less, 300 ppm or less, 200 ppm or less, 100 ppm or less, 80 ppm or less, and particularly preferably 50 ppm or less. On the other hand, considering the cost of the raw material used, it is preferably 5 ppm or more, 10 ppm or more, particularly 15 ppm or more.

The glass having the above composition has a thermal expansion coefficient (30 to 300 ° C.) of 40 to 140 × 10 ⁻⁷ / ° C., 50 to 130 × 10 ⁻⁷ / ° C., particularly 60 to 120 × 10 ⁻⁷ / ° C. It tends to be ℃.

The glass lens preferably has a thickness of 1 mm and an internal transmittance of 90% or more, 92% or more, particularly 95% or more in a wavelength range of 400 to 1500 nm. If the internal transmittance is low, there is a risk of damage due to heat generated by absorption of laser light.

The glass lens preferably has a strain point of 400 ° C. or higher, 450 ° C. or higher, particularly 500 ° C. or higher. If the strain point is too low, the shape of the lens may change when exposed to high temperatures, and the optical axis may shift.

The glass lens has a refractive index of 1.45 or more, 1.46 or more, 1.47 or more, 1.48 or more, 1.49 or more, 1.50 or more, 1.51 or more, particularly 1.52 or more. Is preferred. If the refractive index is too low, the focal length tends to be large, and it is difficult to reduce the size of the spark plug. The upper limit of the refractive index is not particularly limited, but considering the stability of the glass, it is preferably 2.30 or less, 2.25 or less, 2.20 or less, 2.15 or less, particularly 2.10 or less.

The glass lens preferably has an Abbe number of 35 or more, 37 or more, particularly 39 or more. However, it is preferable that the Abbe number is high because the wavelength dispersion of the refractive index is small. However, considering the maintenance of the high refractive index and the stability of the glass, it is preferably 45 or less, 43 or less, particularly 42.5 or less.

If the glass lens has ΔT = (temperature at 10 ^0.5 poise−liquidus temperature) of 20 ° C. or more, 30 ° C. or more, particularly 40 ° C. or more, a sufficient working temperature can be secured. Preform glass can be manufactured with high yield. ΔT is preferably as large as possible, and the upper limit of the ΔT is not particularly limited, but in practice, it is preferably 300 ° C. or less, particularly 200 ° C. or less. The temperature corresponding to 10 ^0.5 poise corresponds to the molding temperature when the droplet forming method is adopted. Since glass is most easily devitrified when performing droplet forming, if the difference ΔT between the temperature at 10 ^0.5 poise and the liquidus temperature is 20 ° C. or more, all including the droplet forming method In this molding method, molding can be performed without causing devitrification.

It is preferable that the basicity of the glass lens is 11 or less, particularly 9.5 or less. If the basicity is low, it is possible to prevent the glass and the press mold from being fused at the time of molding by the mold press. In the present invention, the basicity is defined as (total number of moles of oxygen atoms / total number of positive field strength) × 100. Field Strength (hereinafter referred to as FS) in the equation is obtained by the following equation.

F. S. = Z / r ² Z represents the ion valence, and r represents the ion radius. The coordination number and ionic valence of the elements in the glass change depending on the glass composition, and the numerical value of the ion radius changes accordingly. Therefore, in calculating an accurate basicity, it is desirable to appropriately select the ionic valence and ionic radius of each element for each composition system. The numerical values of Z and r may be determined by referring to “Chemical Handbook Basic Edition 2nd edition (published by Maruzen Co., Ltd., 1975)”. In the present invention, it is appropriate to use the values shown in Table 1 determined with reference to this document.

The basicity of glass is an index indicating how much oxygen electrons in glass are attracted to cations in glass. In a glass having a high basicity, the attraction of oxygen electrons by cations in the glass is weak. Therefore, when a glass having a high basicity is in contact with a cation (mold component) that has a strong tendency to demand electrons, a cation from the mold is more likely to enter the glass than a glass having a low basicity. . When the cation which is a mold component penetrates (diffuses) into the glass, the mold component concentration in the glass phase near the interface increases. Thereby, since the difference in composition between the glass phase and the mold phase is reduced, the affinity between the two is increased, and the glass is easily wetted by the mold. It is considered that the glass and the mold are fused by such a mechanism. Therefore, as the basicity is lowered, the mold components are less likely to enter the glass, and the glass and the mold are not fused.

(Metal holder 12)
The metal holder 12 has a cylindrical shape and has openings at both ends. The material of the metal holder is not particularly limited, but is preferably Hastelloy (registered trademark), Inconel (registered trademark), SUS or the like in view of heat resistance and workability.

The above metal has a coefficient of thermal expansion (30 to 300 ° C.) of 70 to 200 × 10 ⁻⁷ / ° C., 80 to 190 × 10 ⁻⁷ / ° C., particularly 90 to 180 × 10 ⁻⁷ / ° C. Cheap.

FIG. 3 is a schematic cross-sectional view showing the manufacturing process of the lens barrel-integrated lens for a spark plug according to the present invention. Hereinafter, the manufacturing method of the lens barrel-integrated lens for a spark plug according to the present invention will be described with reference to FIG. However, the present invention is not limited to this.

First, glass raw materials prepared to have a desired composition are melted to obtain molten glass. Next, molten glass is dropped from the nozzle tip and formed into droplets (droplet forming) to obtain a glass material. Further, after the molded glass material is polished or molded without being polished, a glass lens glass material 11 having a predetermined shape is obtained. Instead of performing droplet forming, it is also possible to adopt a method in which molten glass is formed into an ingot, the glass material cut out to an appropriate size is polished, and then mold pressing is performed.

Subsequently, after the glass lens glass material 11 having an outer diameter smaller than the inner diameter of the metal holder 12 is accommodated in the metal holder 12 having a higher thermal expansion coefficient than the glass lens glass material 11, the pressing jig 13 is installed. After heating to near the glass transition point in this state, the glass lens glass material 11 is pressed with a pressing jig 13 and cooled to fix the glass lens glass material 11 in a state where the optical axis coincides with the metal holder 12. The Specifically, the glass lens glass material 11 is softened and deformed and is brought into close contact with the metal holder 12 by pressing the glass lens glass material 11 in the heating process. Further, the glass lens glass material 11 becomes a glass lens 14 having a predetermined shape by pressing. Thereafter, by cooling the glass lens 14 and the metal holder 12 in close contact with each other, the metal holder 12 clamps the glass lens 14 due to the difference in thermal shrinkage between the metal holder 12 and the glass lens 14, and the glass lens 14 is fixed. .

It should be noted that the heating temperature is preferably higher than the temperature to which the glass lens 11 is exposed when the internal combustion engine is driven. Specifically, the heating temperature is preferably 250 ° C. or higher, 280 ° C. or higher, 300 ° C. or higher, 320 ° C. or higher, particularly 340 ° C. or higher. When the heating temperature is too low, the metal holder 12 cannot sufficiently tighten the glass lens 11 when exposed to a high temperature when the internal combustion engine is driven, and the glass lens 11 is not easily fixed.

Here, the thermal expansion coefficient (30 to 300 ° C.) of the metal holder 12 is 1 to 150 × 10 ⁻⁷ / ° C. and 5 to 130 × 10 ⁻⁷ / from the thermal expansion coefficient (30 to 300 ° C.) of the glass lens 11. 10 ° C., 10 to 120 × 10 ⁻⁷ / ° C., 20 to 110 × 10 ⁻⁷ / ° C., 30 to 100 × 10 ⁻⁷ / ° C., 40 to 90 × 10 ⁻⁷ / ° C., especially 50 to 70 × 10 ⁻⁷ / C is preferably high. If the difference in thermal expansion coefficient is too small, the metal holder 12 is difficult to fasten the glass lens 11, and the glass lens 11 is difficult to be fixed. On the other hand, if the difference in thermal expansion coefficient is too large, the stress applied to the glass lens 11 is increased, and the glass lens 11 may be damaged.

Hereinafter, the present invention will be described based on examples, but the present invention is not limited to the following examples.

(Example)
By mass%, B ₂ O ₃ 21%, La ₂ O ₃ 24%, ZnO 19%, Gd ₂ O ₃ 9%, SiO ₂ 5%, Li ₂ O 1%, Ta ₂ O ₅ 7%, ZrO ₂ 6% Glass raw materials were prepared so as to be 2% WO ₃ and 6% Nb ₂ O ₅ and melted at 1100-1500 ° C. for 1-4 hours using a platinum crucible to obtain a glass melt. Next, a glass melt was dropped into a mold from a platinum nozzle to obtain a preform glass (glass transition point 554 ° C., softening point 635 ° C.). Preform glass is put into a precision-processed mold and pressed while heating at the softening point, and the surface shape of the mold is transferred to the preform glass. The front curvature radius is 20 mm, the rear curvature radius is 20 mm, A biconvex glass lens glass material having a height of 1 mm was obtained. The obtained glass lens glass material (thermal expansion coefficient (30 to 300 ° C.) 68 × 10 ⁻⁷ / ° C.) is placed in a metal holder made of SUS405 (thermal expansion coefficient (30 to 300 ° C.) 108 × 10 ⁻⁷ / ° C.). After storage, a pressing jig was installed. In this state, the glass lens was heated to the glass transition point, the glass lens glass material was pressed with a pressing jig, and then cooled to obtain a lens-integrated lens. In the obtained lens barrel-integrated lens, the glass lens was fixed at a predetermined position in the metal holder.

DESCRIPTION OF SYMBOLS 1 Collimating lens 2 Resonator 3 Diffusing lens 4 Condensing lens 5 Cover glass 10 Lens-integrated lens 11 Glass lens glass material 12 Metal holder 13 Jig for pressing 14 Glass lens

Claims (11)

1. A cylindrical metal holder having openings at both ends;
   With a glass lens fixed in the metal holder by the tightening force of the metal holder,
   A lens barrel-integrated lens for a spark plug, wherein the thermal expansion coefficient of the metal holder is higher than that of the glass lens.
2. 2. The spark plug according to claim 1, wherein the thermal expansion coefficient (30 to 300 ° C.) of the metal holder is 1 to 150 × 10 ⁻⁷ / ° C. higher than the thermal expansion coefficient (30 to 300 ° C.) of the glass lens. A lens barrel integrated lens.
3. 3. The lens barrel-integrated lens for a spark plug according to claim 1, wherein the glass lens has a thickness of 1 mm and an internal transmittance of 90% or more in a wavelength range of 400 to 1500 nm.
4. 4. The lens barrel-integrated lens for a spark plug according to claim 1, wherein a distortion point of the glass lens is 400 ° C. or more.
5. 5. The spark plug barrel according to claim 1, wherein the glass lens has a refractive index (nd) of 1.45 to 2.30 and an Abbe number (νd) of 35 to 45. Body lens.
6. 6. The lens barrel-integrated lens for a spark plug according to claim 1, wherein ΔT = (temperature at 10 ^0.5 poise−liquidus temperature) of the glass lens is 20 ° C. or more. .
7. 7. The lens barrel-integrated lens for a spark plug according to claim 1, wherein the glass lens is made of B ₂ O ₃ —ZnO—La ₂ O ₃ —Gd ₂ O ₃ glass.
8. Wherein the glass lens is a _{composition, B 2 O 3 5 ~ 45} % by _{mass%, ZnO 10 ~ 45%,} La 2 O 3 5 ~ 25%, in that it contains Gd 2 O 3 0.5 ~ 24% The lens barrel-integrated lens for a spark plug according to claim 7.
9. The contents of La ₂ O ₃ , Gd ₂ O ₃ and ZnO are in a relationship of 0.1 ≦ (La ₂ O ₃ + Gd ₂ O ₃ ) /ZnO≦5.0 on a mass% basis. The lens barrel-integrated lens for a spark plug according to claim 7 or 8.
10. Placing and heating a glass lens glass material having an outer diameter smaller than the inner diameter of the metal holder in the metal holder;
    A step of pressing the glass lens glass material so that the glass lens glass material is in close contact with the metal holder and has a predetermined lens shape;
    And a step of cooling to room temperature. A method of manufacturing a lens barrel-integrated lens for a spark plug.
11. A cylindrical metal holder having openings at both ends;
    A lens barrel-integrated lens for a spark plug, comprising: a glass lens fixed in a metal holder.

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