JP2012047110A - Internal combustion engine - Google Patents

Internal combustion engine Download PDF

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JP2012047110A
JP2012047110A JP2010190408A JP2010190408A JP2012047110A JP 2012047110 A JP2012047110 A JP 2012047110A JP 2010190408 A JP2010190408 A JP 2010190408A JP 2010190408 A JP2010190408 A JP 2010190408A JP 2012047110 A JP2012047110 A JP 2012047110A
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internal combustion
combustion engine
combustion chamber
particles
base material
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Hidemasa Kosaka
英雅 小坂
Yoshifumi Wakizaka
佳史 脇坂
Minaji Inayoshi
三七二 稲吉
Shinya Iida
晋也 飯田
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Toyota Central R&D Labs Inc
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
    • F05C2251/00—Material properties
    • F05C2251/04—Thermal properties
    • F05C2251/048—Heat transfer

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Abstract

PROBLEM TO BE SOLVED: To maintain an insulation property in an internal combustion engine having insulative films with a porous structure.SOLUTION: The insulative films 40, 42 having thermal conductivity lower than thermal conductivity of a combustion chamber base material and a heat capacity per unit volume lower than the heat capacity per unit volume of the combustion chamber base material, wherein each element forming the combustion chamber 26 is set as a combustion chamber base material, are formed on a wall surface facing to a combustion chamber 26 of the internal combustion engine 10. The insulative films 40, 42 are formed from an anode oxide film having the porous structure including numerous pores, and a plurality of filler particles are charged into the pores so as to make a gap between neighboring particles set to be a predesignated size. For example, the size of the designated gap is set to be smaller than an mean free path of gaseous molecules under high temperature and high pressure in the combustion chamber 26.

Description

本発明は、内燃機関に係り、特に燃焼室内壁に断熱膜を有する内燃機関に関する。   The present invention relates to an internal combustion engine, and more particularly to an internal combustion engine having a heat insulating film on a combustion chamber wall.

内燃機関の熱損失を低減するために、燃焼室内壁に断熱膜を設けることが行われる。例えば、特許文献１には、内燃機関の燃焼室内に臨む壁面に形成する断熱膜として、粒状に形成された多数の断熱材と、膜状に形成された断熱材とを含み、膜状の断熱材は、燃焼室の母材の熱伝導率以下の熱伝導率を有し、粒状の断熱材は、燃焼室の母材の熱伝導率より低い熱伝導率と、母材の単位体積あたりの熱容量より低い単位体積あたりの熱容量を有し、さらに膜状の断熱材の熱伝導率より低い熱伝導率と、膜状の断熱材の単位体積あたりの熱容量より低い単位体積あたりの熱容量を有する構成が開示されている。   In order to reduce the heat loss of the internal combustion engine, a heat insulating film is provided on the combustion chamber wall. For example, Patent Document 1 includes a large number of granular heat insulating materials as a heat insulating film formed on a wall surface facing the combustion chamber of an internal combustion engine and a heat insulating material formed in a film shape. The material has a thermal conductivity equal to or lower than the thermal conductivity of the combustion chamber base material, and the granular heat insulating material has a thermal conductivity lower than the thermal conductivity of the combustion chamber base material and per unit volume of the base material. A structure having a heat capacity per unit volume lower than the heat capacity, a heat conductivity lower than the heat conductivity of the film-like heat insulating material, and a heat capacity per unit volume lower than the heat capacity per unit volume of the film-like heat insulating material Is disclosed.

また、非特許文献１には、内燃機関におけるクランク角度位相、燃焼室壁温度振幅等の、熱伝達特性の熱力学的効率への影響を調べた結果が報告されている。ここでは、エンジンサイクルの燃焼行程に熱伝達を抑制することが効率向上に最も効くこと、プラズマスプレー法によるジルコニア薄膜コーティングまたはセラミックスラリー薄膜コーティングの最適膜厚は、０．２５ｍｍから０．５ｍｍであること等が述べられている。   Non-Patent Document 1 reports the results of examining the influence of heat transfer characteristics on thermodynamic efficiency, such as crank angle phase and combustion chamber wall temperature amplitude in an internal combustion engine. Here, suppression of heat transfer in the combustion stroke of the engine cycle is most effective in improving efficiency, and the optimum film thickness of the zirconia thin film coating or ceramic slurry thin film coating by the plasma spray method is 0.25 mm to 0.5 mm. That is stated.

特開２００９−２４３３５２号公報JP 2009-243352 A

Victor W. Wong et.al.，Assessment of Thin Thermal Barrier Coating for I.C. Engines，1995 Society of Automotive Engineers, Inc.，950980，p1-11Victor W. Wong et.al., Assessment of Thin Thermal Barrier Coating for I.C. Engines, 1995 Society of Automotive Engineers, Inc., 950980, p1-11

このように、内燃機関において、燃焼室壁面に断熱膜を形成すると、燃焼中に高温となった燃焼ガスの温度に追従して断熱膜の表面温度が変化し、ガスとの温度差が小さくなって、内燃機関の熱損失の低減を図ることが可能となる。   Thus, in an internal combustion engine, when a heat insulation film is formed on the wall surface of the combustion chamber, the surface temperature of the heat insulation film changes following the temperature of the combustion gas that becomes high during combustion, and the temperature difference from the gas becomes small. Thus, it is possible to reduce the heat loss of the internal combustion engine.

固体材料に比べ、気体である空気は、熱伝導率、単位体積当り熱容量がともに非常に小さいため、例えば、ポーラス構造を有する膜を用いると、熱伝導性が小さく、また単位体積当り熱容量の小さい断熱膜となる。このようなポーラス構造の膜として、エンジンの母材がアルミニウムであることから、その陽極酸化膜を用いることが考えられる。   Compared with solid materials, air, which is a gas, has a very low thermal conductivity and heat capacity per unit volume. For example, if a film having a porous structure is used, the thermal conductivity is low and the heat capacity per unit volume is low. It becomes a heat insulating film. Since the base material of the engine is aluminum, it is conceivable to use the anodic oxide film as such a porous structure film.

ところで、陽極酸化膜のポーラス構造は、表面に向かって繋がった空孔となっているので、エンジンの燃焼室内のような高圧雰囲気の内壁面に形成すると、その高温高圧の気体がその空孔内に入り込み、断熱効果が低下する恐れがある。   By the way, since the porous structure of the anodic oxide film is a hole connected to the surface, if it is formed on the inner wall surface of a high-pressure atmosphere such as the combustion chamber of the engine, the high-temperature and high-pressure gas is contained within The heat insulation effect may be reduced.

本発明の目的は、ポーラス構造の断熱膜の断熱性を維持することができる内燃機関を提供することである。   The objective of this invention is providing the internal combustion engine which can maintain the heat insulation of the heat insulation film | membrane of a porous structure.

本発明に係る内燃機関は、内燃機関の燃焼室を構成する各要素を燃焼室母材として、燃焼室母材の燃焼室に面する壁面に形成され、燃焼室母材の熱伝導率よりも低い熱伝導率と、燃焼室母材の単位体積当り熱容量よりも低い単位体積当り熱容量とを有し、多数の空孔を含むポーラス構造を有する陽極酸化膜から構成される断熱膜と、断熱膜の空孔の内部に封入される複数の粒子であって、隣接する粒子の間の隙間が予め設定される大きさの空隙となるように封入される複数の封入粒子と、を備えることを特徴とする。   The internal combustion engine according to the present invention is formed on a wall surface of the combustion chamber base material facing the combustion chamber, with each element constituting the combustion chamber of the internal combustion engine as a combustion chamber base material, and more than the thermal conductivity of the combustion chamber base material. A heat insulating film having a low thermal conductivity and a heat capacity per unit volume lower than the heat capacity per unit volume of the combustion chamber base material, and comprising a porous structure including a large number of pores; and a heat insulating film A plurality of encapsulated particles encapsulated in such a manner that a gap between adjacent particles is a gap having a predetermined size. And

また、本発明に係る内燃機関において、封入粒子は、中空構造を有する中空粒子であることが好ましい。   In the internal combustion engine according to the present invention, the encapsulated particles are preferably hollow particles having a hollow structure.

また、本発明に係る内燃機関において、封入粒子は、陽極酸化膜の空孔の大きさよりも小さい外形で、１０ｎｍ以上１５０ｎｍ以下の粒子径を有することが好ましい。   In the internal combustion engine according to the present invention, the encapsulated particles preferably have a particle size of 10 nm or more and 150 nm or less with an outer shape smaller than the size of the pores of the anodized film.

また、本発明に係る内燃機関において、封入粒子は、ナノ中空体ビーズまたはナノ多孔体またはナノチューブで構成されることが好ましい。   In the internal combustion engine according to the present invention, the encapsulated particles are preferably composed of nano hollow beads, nano porous bodies, or nanotubes.

また、本発明に係る内燃機関において、粒子を空孔内に封入することで形成される空隙は、内燃機関の燃焼室における気体分子の平均自由行程よりも小さいことが好ましい。   In the internal combustion engine according to the present invention, it is preferable that the void formed by enclosing the particles in the pores is smaller than the mean free path of gas molecules in the combustion chamber of the internal combustion engine.

上記構成により、内燃機関は、燃焼室母材の熱伝導率よりも低い熱伝導率と、燃焼室母材の単位体積当り熱容量よりも低い単位体積当り熱容量とを有し、多数の空孔を含むポーラス構造を有する陽極酸化膜から構成される断熱膜が設けられる。そして、断熱膜の空孔の内部には、隣接する粒子の間の隙間が予め設定される大きさの空隙となるように複数の封入粒子が封入される。これにより、ポーラス構造として表面に向かって繋がっている空孔であっても、表面から気体が入り込むことを防止でき、断熱膜の断熱性を維持することができる。   With the above configuration, the internal combustion engine has a thermal conductivity lower than the thermal conductivity of the combustion chamber base material and a heat capacity per unit volume lower than the thermal capacity per unit volume of the combustion chamber base material, and has a large number of holes. A heat insulating film composed of an anodized film having a porous structure is provided. A plurality of encapsulated particles are encapsulated inside the pores of the heat insulating film so that the gap between adjacent particles becomes a gap having a preset size. Thereby, even if it is a void | hole connected toward the surface as a porous structure, gas can be prevented from entering from the surface, and the heat insulation of a heat insulation film | membrane can be maintained.

また、内燃機関において、断熱膜に封入される粒子は、中空構造を有する中空粒子であるので、断熱性を十分に維持することができる。   Further, in the internal combustion engine, since the particles enclosed in the heat insulating film are hollow particles having a hollow structure, the heat insulating property can be sufficiently maintained.

また、内燃機関において、封入粒子は、陽極酸化膜の空孔の大きさよりも小さい外形で、１０ｎｍ以上１５０ｎｍ以下の粒子径を有する。陽極酸化膜の空孔の径は、およそ１０ｎｍから１５０ｎｍであるので、この程度の粒子径が好ましい。   Further, in the internal combustion engine, the encapsulated particles have a particle size of 10 nm or more and 150 nm or less with an outer shape smaller than the pore size of the anodized film. Since the pore diameter of the anodized film is about 10 nm to 150 nm, a particle diameter of this level is preferable.

また、内燃機関において、封入粒子は、ナノ中空体ビーズまたはナノ多孔体またはナノチューブで構成されるので、陽極酸化膜の空孔内に十分に配置することができる。   In the internal combustion engine, the encapsulated particles are composed of nano hollow body beads, nano porous bodies, or nanotubes, so that they can be sufficiently disposed in the pores of the anodized film.

また、内燃機関において、粒子を空孔内に封入することで形成される空隙は、内燃機関の燃焼室における気体分子の平均自由行程よりも小さい。これによって、空孔の表面から内部に向かって気体が入り込むことを十分に抑制でき、さらに、空隙に存在する気体の熱伝導率は、同じ圧力で平均自由行程以上の領域に存在する気体よりも低下するので、断熱膜の断熱性をさらに向上させることができる。また、封入粒子により空隙が小さくなることで、空孔内に存在する気体の対流も抑制することができ、断熱膜の断熱性をさらに向上できる。   Further, in the internal combustion engine, the void formed by enclosing the particles in the pores is smaller than the mean free path of gas molecules in the combustion chamber of the internal combustion engine. Thereby, it is possible to sufficiently suppress the gas from entering from the surface of the hole toward the inside, and the thermal conductivity of the gas present in the void is higher than that of the gas present in the region above the mean free path at the same pressure. Since it falls, the heat insulation of a heat insulation film | membrane can further be improved. Moreover, since the voids are reduced by the encapsulated particles, the convection of the gas existing in the pores can be suppressed, and the heat insulating property of the heat insulating film can be further improved.

本発明に係る実施の形態の内燃機関について、燃焼室周辺の構成を説明する図である。It is a figure explaining the structure of a combustion chamber periphery about the internal combustion engine of embodiment which concerns on this invention. 本発明に係る実施の形態において、断熱膜である陽極酸化膜の構成を説明する図である。In embodiment which concerns on this invention, it is a figure explaining the structure of the anodic oxide film which is a heat insulation film | membrane. 本発明に係る実施の形態において、断熱膜の空孔に封入される粒子の様子を説明する図である。In embodiment which concerns on this invention, it is a figure explaining the mode of the particle | grains enclosed with the hole of a heat insulation film | membrane. 気体分子の平均自由行程を説明する図である。It is a figure explaining the mean free path of gas molecules.

以下に図面を用いて本発明に係る実施の形態につき、詳細に説明する。以下では、内燃機関として火花点火式ガソリンエンジンを説明するが、様々な仕様の火花点火式機関、圧縮着火式機関等に適用可能である。   Embodiments according to the present invention will be described below in detail with reference to the drawings. Hereinafter, a spark ignition gasoline engine will be described as an internal combustion engine, but the present invention can be applied to various types of spark ignition engines, compression ignition engines, and the like.

また、以下では、燃焼室の構成として、シリンダ、ピストン、吸気弁、排気弁、点火プラグを説明するが、これは燃焼室壁面に関連する主要な要素であって、内燃機関としては、勿論これ以外の要素を含む。例えば、燃料噴射弁、スロットルバルブ、フローメータ、ＥＧＲ等を含むが、これらの説明は単に省略しただけである。   In the following, a cylinder, a piston, an intake valve, an exhaust valve, and a spark plug will be described as the configuration of the combustion chamber. However, this is a major element related to the wall surface of the combustion chamber. Contains elements other than. For example, a fuel injection valve, a throttle valve, a flow meter, EGR, etc. are included, but these descriptions are merely omitted.

また、以下の燃焼室の形状、燃焼室の構成要素の配置等は、説明のための例示であり、内燃機関の仕様に応じ、適宜変更が可能である。   Further, the following shape of the combustion chamber, arrangement of the components of the combustion chamber, and the like are examples for explanation, and can be appropriately changed according to the specifications of the internal combustion engine.

以下では、全ての図面において同様の要素には同一の符号を付し、重複する説明を省略する。また、本文中の説明においては、必要に応じそれ以前に述べた符号を用いるものとする。   Below, the same code | symbol is attached | subjected to the same element in all the drawings, and the overlapping description is abbreviate | omitted. In the description in the text, the symbols described before are used as necessary.

図１は、内燃機関１０における燃焼室２６の周辺を説明するための図である。この内燃機関１０は、火花点火式のガソリンエンジンであり、図１では、その１つの気筒の断面図が示されている。   FIG. 1 is a view for explaining the periphery of the combustion chamber 26 in the internal combustion engine 10. The internal combustion engine 10 is a spark ignition type gasoline engine, and FIG. 1 shows a cross-sectional view of one cylinder thereof.

ここでは、ピストン１２と、ピストン１２が摺動するシリンダ１４とが示されている。ピストン１２は、円柱状の外形形状を有し、その上面３０は、中央部にキャビティとも呼ばれるくぼみを有する。シリンダ１４は、ピストン１２の摺動を案内する円筒状の内壁と、円筒状の天井部を構成する上部部材とを含む。円筒状の部分はライナ部と呼ばれ、天井部を構成する上部部材はヘッド部と呼ばれる。ピストン１２の上面３０とシリンダ１４のヘッド部の下面３２とで囲まれる空間が燃焼室２６である。   Here, a piston 12 and a cylinder 14 on which the piston 12 slides are shown. The piston 12 has a cylindrical outer shape, and the upper surface 30 has a recess called a cavity at the center. The cylinder 14 includes a cylindrical inner wall that guides the sliding of the piston 12 and an upper member that forms a cylindrical ceiling portion. The cylindrical portion is called a liner portion, and the upper member constituting the ceiling portion is called a head portion. A space surrounded by the upper surface 30 of the piston 12 and the lower surface 32 of the head portion of the cylinder 14 is a combustion chamber 26.

シリンダ１４のヘッド部には、吸気弁１６、吸気路１８、排気弁２０、排気路２２、点火プラグ２４等が設けられる。したがって、燃焼室２６の内壁を構成する要素としては、ピストン１２の上面３０、シリンダ１４のヘッド部の下面３２、この下面に配置される吸気弁１６の先端部、排気弁２０の先端部、点火プラグ２４の先端部等が含まれる。これらの要素を、燃焼室を構成する要素としてまとめて、燃焼室母材と呼ぶことにする。ピストン１２、シリンダ１４は、その材質としてアルミニウム合金が用いられるので、燃焼室母材の材質としては一部を除いてアルミニウム合金であると考えてよい。   An intake valve 16, an intake passage 18, an exhaust valve 20, an exhaust passage 22, a spark plug 24, and the like are provided in the head portion of the cylinder 14. Therefore, the elements constituting the inner wall of the combustion chamber 26 include the upper surface 30 of the piston 12, the lower surface 32 of the head portion of the cylinder 14, the tip portion of the intake valve 16 disposed on this lower surface, the tip portion of the exhaust valve 20, and ignition. The tip of the plug 24 and the like are included. These elements are collectively referred to as elements constituting the combustion chamber, and are referred to as a combustion chamber base material. Since the piston 12 and the cylinder 14 are made of an aluminum alloy, the material of the combustion chamber base material may be considered to be an aluminum alloy except for a part thereof.

断熱膜４０，４２は、燃焼室母材が燃焼室２６に面する壁面に形成され、燃焼室２６の燃焼ガスの温度が燃焼室母材に逃げないように断熱して高温を維持するための断熱膜である。断熱膜４０，４２は、燃焼室母材の熱伝導率よりも低い熱伝導率と、燃焼室母材の単位体積当り熱容量よりも低い単位体積当り熱容量とを有する。なお、断熱膜４０は、シリンダ１４のヘッド部の下面３２とともに、そこに配置される吸気弁１６、排気弁２０の下面にも設けられる。また、シリンダ１４の円筒状の部分であるライナ部にも断熱膜を設けるものとしてもよい。   The heat insulating films 40 and 42 are formed on the wall surface where the combustion chamber base material faces the combustion chamber 26, and insulate the temperature of the combustion gas in the combustion chamber 26 so as not to escape to the combustion chamber base material to maintain a high temperature. It is a heat insulating film. The heat insulating films 40 and 42 have a thermal conductivity lower than the thermal conductivity of the combustion chamber base material and a heat capacity per unit volume lower than the heat capacity per unit volume of the combustion chamber base material. The heat insulating film 40 is provided on the lower surface 32 of the head portion of the cylinder 14 as well as the lower surfaces of the intake valve 16 and the exhaust valve 20 disposed there. Moreover, it is good also as what provides a heat insulating film also in the liner part which is a cylindrical part of the cylinder 14. FIG.

このような断熱膜４０，４２としては、陽極酸化皮膜を用いることができる。図２は、陽極酸化断熱膜としての断熱膜４２の構成を説明する断面図である。断熱膜４２は、燃焼室母材であるピストン１２の材質であるアルミニウムを公知の陽極酸化法によって、陽極酸化処理し、多数の空孔４６を有するアルミナ膜４４としたものである。断熱膜４０，４２の厚さは、陽極酸化処理の条件で調整できる。断熱効果を考えると、断熱膜４０，４２の厚さを、例えば、５０μｍから１５０μｍ程度とすることができる。   As such heat insulation films 40 and 42, an anodized film can be used. FIG. 2 is a cross-sectional view illustrating the configuration of the heat insulating film 42 as an anodized heat insulating film. The heat insulating film 42 is an alumina film 44 having a large number of holes 46 by anodizing aluminum which is a material of the piston 12 which is a combustion chamber base material by a known anodizing method. The thickness of the heat insulating films 40 and 42 can be adjusted by the conditions of the anodizing treatment. Considering the heat insulating effect, the thickness of the heat insulating films 40 and 42 can be set to, for example, about 50 μm to 150 μm.

図２に示すように、多数の空孔４６は、燃焼室２６の側に向かって繋がった細長い孔としてアルミナ膜４４の中に形成される。空孔４６の径の大きさはおよそ１０ｎｍから１５０ｎｍである。この空孔４６の中は空気であるので、アルミニウムであるピストン１２に比べ、熱伝導率が低く、また単位体積当り熱容量が小さい。   As shown in FIG. 2, the numerous holes 46 are formed in the alumina film 44 as elongated holes connected toward the combustion chamber 26 side. The diameter of the hole 46 is about 10 nm to 150 nm. Since the air holes 46 are air, the heat conductivity is lower and the heat capacity per unit volume is smaller than that of the piston 12 made of aluminum.

断熱膜４２の空孔４６の中に配置される中空粒子４８は、中空構造を有し、その外径が空孔４６の大きさよりも小さい１０ｎｍ以上１５０ｎｍ以下の径を有し、隣接する粒子の間の隙間が予め設定される大きさの空隙となるように封入される複数の封入粒子である。このような封入粒子としては、ナノ中空体ビーズまたはナノ多孔体またはナノチューブを用いることができる。   The hollow particles 48 disposed in the pores 46 of the heat insulating film 42 have a hollow structure, the outer diameter of which is smaller than the size of the pores 46 and is 10 nm or more and 150 nm or less. It is a plurality of encapsulated particles that are encapsulated so that the gap between them becomes a gap of a preset size. As such encapsulated particles, nano hollow body beads, nano porous bodies or nanotubes can be used.

図３は、断熱膜４２の空孔４６に封入される中空粒子４８の様子を説明する図である。中空粒子４８の大きさは、それぞれが揃っていてもよいが、実際には図３に示されるように異なることが多い。また、図３では、球形の粒子として示されているが、外形は必ずしも対称形でなくてもよい。また、中空粒子４８に代えて、熱伝導率の小さく、単位体積当り熱容量の小さい材質の中実粒子を用いてもよい。   FIG. 3 is a diagram for explaining the state of the hollow particles 48 enclosed in the holes 46 of the heat insulating film 42. The sizes of the hollow particles 48 may be equal to each other, but in reality, they are often different as shown in FIG. In FIG. 3, although shown as spherical particles, the outer shape is not necessarily symmetrical. Instead of the hollow particles 48, solid particles having a small thermal conductivity and a small heat capacity per unit volume may be used.

図３では、隣接する粒子の間の隙間として予め設定される大きさの空隙Ｓが示されている。この空隙Ｓは、空孔４６に燃焼室２６側から高温高圧の気体が入り込まない程度の狭い隙間であることが好ましい。例えば、空隙Ｓを数ｎｍとすることができる。この空隙Ｓは、好ましくは、燃焼室２６の高温高圧の気体について、その気体分子の平均自由行程よりも小さい隙間とすることがよい。   In FIG. 3, a gap S having a size set in advance as a gap between adjacent particles is shown. The gap S is preferably a narrow gap that does not allow high temperature and high pressure gas to enter the holes 46 from the combustion chamber 26 side. For example, the gap S can be several nm. The gap S is preferably a gap smaller than the mean free path of the gas molecules of the high-temperature and high-pressure gas in the combustion chamber 26.

図４は、気体分子５０の平均自由行程Ｓ0の様子を説明する図である。気体分子の平均自由行程Ｓ0とは、いまの場合、空孔４６の中にある空気分子に衝突しながら高温高圧の気体分子が進んでゆくときの直線移動の距離の平均値である。例えば、エンジンの燃焼室２６の状態を１５ＭＰａ、２０００°Ｋとして、その場合の気体分子の平均自由行程は、３．２ｎｍと計算される。したがって、空隙Ｓは、これより小さい値に設定することが好ましい。 FIG. 4 is a diagram for explaining the state of the mean free path S 0 of the gas molecules 50. In this case, the mean free path S 0 of gas molecules is the average value of the distance of linear movement when high-temperature and high-pressure gas molecules travel while colliding with air molecules in the holes 46. For example, assuming that the state of the combustion chamber 26 of the engine is 15 MPa and 2000 ° K, the mean free path of gas molecules in that case is calculated as 3.2 nm. Therefore, the gap S is preferably set to a smaller value.

このように、空孔内の空隙を気体分子の平均自由行程よりも小さくなるように複数の粒子を封入することで、空孔の表面から内部に向かって気体が入り込むことを十分に抑制できる。また、空隙に存在する気体の熱伝導率は、同じ圧力で平均自由行程以上の領域に存在する気体よりも低下するので、断熱膜の断熱性をさらに向上させることができる。また、封入粒子により空隙が小さくなることで、空孔内に存在する気体の対流も抑制することができ、断熱膜の断熱性をさらに向上できる。   Thus, by enclosing a plurality of particles so that the voids in the pores are smaller than the mean free path of the gas molecules, it is possible to sufficiently suppress the gas from entering from the surface of the pores to the inside. Moreover, since the thermal conductivity of the gas existing in the voids is lower than that of the gas existing in the region above the mean free path at the same pressure, the heat insulating property of the heat insulating film can be further improved. Moreover, since the voids are reduced by the encapsulated particles, the convection of the gas existing in the pores can be suppressed, and the heat insulating property of the heat insulating film can be further improved.

本発明に係る内燃機関は、火花点火式機関、圧縮着火式機関に利用できる。   The internal combustion engine according to the present invention can be used for a spark ignition engine and a compression ignition engine.

１０ 内燃機関、１２ ピストン、１４ シリンダ、１６ 吸気弁、１８ 吸気路、２０ 排気弁、２２ 排気路、２４ 点火プラグ、２６ 燃焼室、３０ 上面、３２ 下面、４０，４２ 断熱膜、４４ アルミナ膜、４６ 空孔、４８ 中空粒子、５０ 気体分子。   DESCRIPTION OF SYMBOLS 10 Internal combustion engine, 12 Piston, 14 Cylinder, 16 Intake valve, 18 Intake path, 20 Exhaust valve, 22 Exhaust path, 24 Spark plug, 26 Combustion chamber, 30 Upper surface, 32 Lower surface, 40,42 Thermal insulation film, 44 Alumina film, 46 pores, 48 hollow particles, 50 gas molecules.

Claims (5)

内燃機関の燃焼室を構成する各要素を燃焼室母材として、燃焼室母材の燃焼室に面する壁面に形成され、燃焼室母材の熱伝導率よりも低い熱伝導率と、燃焼室母材の単位体積当り熱容量よりも低い単位体積当り熱容量とを有し、多数の空孔を含むポーラス構造を有する陽極酸化膜から構成される断熱膜と、
断熱膜の空孔の内部に封入される複数の粒子であって、隣接する粒子の間の隙間が予め設定される大きさの空隙となるように封入される複数の封入粒子と、
を備えることを特徴とする内燃機関。 Each element constituting the combustion chamber of the internal combustion engine is formed on the wall surface of the combustion chamber base material facing the combustion chamber, and has a thermal conductivity lower than that of the combustion chamber base material, and the combustion chamber A heat insulating film having a heat capacity per unit volume lower than the heat capacity per unit volume of the base material and composed of an anodized film having a porous structure including a large number of pores;
A plurality of encapsulated particles that are encapsulated in the pores of the heat insulating film, the encapsulated particles being encapsulated so that the gap between adjacent particles becomes a gap of a preset size;
An internal combustion engine comprising: 請求項１に記載の内燃機関において、
封入粒子は、中空構造を有する中空粒子であることを特徴とする内燃機関。 The internal combustion engine according to claim 1,
The internal combustion engine, wherein the encapsulated particles are hollow particles having a hollow structure. 請求項２に記載の内燃機関において、
封入粒子は、陽極酸化膜の空孔の大きさよりも小さい外形で、１０ｎｍ以上１５０ｎｍ以下の粒子径を有することを特徴とする内燃機関。 The internal combustion engine according to claim 2,
The internal combustion engine, wherein the encapsulated particles have a particle size of 10 nm or more and 150 nm or less with an outer shape smaller than the pore size of the anodized film. 請求項４に記載の内燃機関において、
封入粒子は、ナノ中空体ビーズまたはナノ多孔体またはナノチューブで構成されることを特徴とする内燃機関。 The internal combustion engine according to claim 4,
An internal combustion engine in which encapsulated particles are composed of nano hollow body beads, nano porous bodies, or nanotubes. 請求項１に記載の内燃機関において、
粒子を空孔内に封入することで形成される空隙は、内燃機関の燃焼室における気体分子の平均自由行程よりも小さいことを特徴とする内燃機関。 The internal combustion engine according to claim 1,
An internal combustion engine characterized in that a void formed by enclosing particles in a hole is smaller than the mean free path of gas molecules in a combustion chamber of the internal combustion engine.
JP2010190408A 2010-08-27 2010-08-27 Internal combustion engine Pending JP2012047110A (en)

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