JP5629463B2 - Internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine, and more particularly to an internal combustion engine in which a heat insulating film is formed on a wall surface facing at least a part of a base material forming a combustion chamber of the internal combustion engine.

  In order to improve the thermal efficiency of an internal combustion engine, a technique for forming a heat insulating film on a wall surface facing at least a part of a base material forming a combustion chamber of the internal combustion engine has been proposed (for example, the following non-patent document) 1, 2). In Non-Patent Documents 1 and 2, heat transfer from the combustion gas in the combustion chamber to the piston is achieved by forming a single-material heat insulating film made of ceramic (zirconia) with low thermal conductivity on the top surface of the piston. The thermal efficiency is improved by lowering.

Regarding the heat loss Q [W] in the cylinder of the internal combustion engine, the heat transfer coefficient h [W / (m ² · K)] due to the pressure and gas flow in the cylinder, the surface area A [m ² ] in the cylinder, Using the gas temperature Tg [K] in the cylinder and the temperature Twall [K] of the wall surface facing the cylinder (in contact with the combustion gas in the cylinder), it can be expressed by the following equation (1).

  Q = A × h × (Tg−Twall) (1)

  In the cycle of the internal combustion engine, the in-cylinder gas temperature Tg changes from moment to moment, but by changing the wall surface temperature Twall from moment to moment so as to follow the in-cylinder gas temperature Tg, (Tg−Twall) in the equation (1) The value can be reduced, and the heat loss Q can be reduced.

  In order to change the wall surface temperature Twall to follow the in-cylinder gas temperature Tg, it is desirable that the heat insulating film formed on the wall surface facing the combustion chamber has a low thermal conductivity and a heat capacity per unit volume. However, even if a single material heat insulating film made of ceramic (for example, zirconia) is formed on the wall surface facing the combustion chamber, the low thermal conductivity and heat capacity per unit volume are insufficient. As a result, the followability of the wall surface temperature Twall to the in-cylinder gas temperature Tg is lowered, and the effect of reducing the heat loss Q is insufficient.

  There are single materials that have lower thermal conductivity and heat capacity per unit volume than ceramics (for example, zirconia), but there are many materials with low heat resistance and strength, such as resin and foam, for example, in cylinders of internal combustion engines. It does not have heat resistance and strength that can withstand high temperature and high speed gas flow and high pressure.

International Publication No. 89/03930 Pamphlet US Pat. No. 4,495,907 US Pat. No. 5,820,976 Gerhard Woschni et al., "Heat Insulation of Combustion Chamber Walls-A Measure to Decrease the Fuel Combustion of I.C.Engines?", SAE Paper 870339, Society of Automotive Engineers, 1987 Victor W. Wong et al., “Assessment of Thin Thermal Barrier Coatings for I.C. Engines”, SAE Paper 950980, Society of Automotive Engineers, 1995

  The internal combustion engine which concerns on this invention aims at improving thermal efficiency by improving the followable | trackability to the gas temperature in a cylinder of combustion chamber wall surface temperature.

In an internal combustion engine according to the present invention, at least a portion of the base material forming the combustion chamber, the wall surface facing the combustion chamber, the heat insulating film is formed. The heat insulating film includes a first heat insulating material and a second heat insulating material, and the second heat insulating material is zirconia, silicon, titanium, zirconium, ceramic, ceramic fiber, or a combination thereof. The first heat insulating material has a thermal conductivity lower than that of the base material and a heat capacity per unit volume lower than that of the base material, the second heat insulating material has a heat conductivity equal to or lower than the base material, and The first heat insulating material is lower in thermal conductivity than the second heat insulating material and lower in unit volume than the second heat insulating material. It is preferable to have a heat capacity. The first heat insulating material is preferably a hollow ceramic bead, a hollow glass bead, a fine porous heat insulating material, a silica airgel, or a combination of these. The heat insulating film can vary the temperature of the combustion chamber wall in a cycle of 550 ° C. or more in the cycle of the internal combustion engine. Further, the heat insulating film can change the combustion chamber wall surface temperature within a range of 200 ° C. or more in the cycle of the internal combustion engine. Further, the heat insulating film can change the temperature of the combustion chamber wall with a width of 650 ° C. or less in the cycle of the internal combustion engine .

  According to the present invention, the first heat insulating material is protected from the combustion gas in the combustion chamber by the second heat insulating material, so that the heat resistance and pressure resistance of the first heat insulating material against the combustion gas in the combustion chamber are limited. Therefore, a heat insulating material having a sufficiently low thermal conductivity and a heat capacity per unit volume can be selected, and a heat conductivity and a heat capacity per unit volume in the entire heat insulating film can be sufficiently reduced. As a result, the followability of the combustion chamber wall temperature to the cylinder gas temperature can be improved, and the thermal efficiency of the internal combustion engine can be improved. In addition, about a 1st heat insulating material, it can also be comprised by 1 type of heat insulating material, and can also be comprised by multiple types of heat insulating material. And also about a 2nd heat insulating material, it can also be comprised by one type of heat insulating material, and can also be comprised by multiple types of heat insulating material.

  In one embodiment of the present invention, it is preferable that the first heat insulating material is mixed in the second heat insulating material. In this aspect, the second heat insulating material in which the first heat insulating material is mixed is formed in a fiber shape, and a large number of second heat insulating materials formed in the fiber shape are spread on the wall surface. It is preferred that Moreover, in this aspect, it is preferable that the mixing ratio of the first heat insulating material varies depending on the position inside the second heat insulating material. In this embodiment, it is preferable that the first heat insulating material is regularly arranged inside the second heat insulating material. In this embodiment, the first heat insulating material is preferably a heat insulating material having a hollow structure, and further, the first heat insulating material preferably has a multi-layer structure.

  In one aspect of the present invention, the first heat insulating material is formed on the wall surface, and the second heat insulating material is formed on the first heat insulating material so as to cover the first heat insulating material. Is preferred. Here, the first heat insulating material can be directly bonded or coated on the wall surface, and the first heat insulating material can be bonded or coated on the wall surface via an intermediate layer such as an adhesive layer. In addition, the second heat insulating material can be directly bonded or coated to the first heat insulating material, or the second heat insulating material can be bonded or coated to the first heat insulating material via an intermediate layer such as an adhesive layer. You can also. In this aspect, it is preferable that the second heat insulating material is provided with a protruding portion that protrudes toward the first heat insulating material.

  In one embodiment of the present invention, the second heat insulating material is preferably a shell-shaped heat insulating material containing the first heat insulating material therein.

  In one embodiment of the present invention, it is preferable that the first heat insulating material and the second heat insulating material are alternately arranged in the thickness direction of the heat insulating film.

  In one embodiment of the present invention, it is preferable that the heat resistance temperature of the second heat insulating material is higher than the heat resistance temperature of the first heat insulating material. In one embodiment of the present invention, it is preferable that the strength of the second heat insulating material is higher than the strength of the first heat insulating material.

  In one embodiment of the present invention, it is preferable that the second heat insulating material has a thermal conductivity lower than that of the base material and a heat capacity per unit volume lower than or substantially equal to that of the base material. .

An internal combustion engine according to a reference example of the present invention is an internal combustion engine in which a heat insulating film is formed on a wall surface facing the combustion chamber of at least a part of a base material forming the combustion chamber of the internal combustion engine. The film includes a heat insulating material in which a large number of bubbles are formed inside a material having a thermal conductivity lower than that of the base material and a heat capacity per unit volume lower than that of the base material or substantially equivalent to that of the base material. It is a summary.

  According to the present invention, the thermal conductivity of the entire heat insulating film and the heat capacity per unit volume can be sufficiently lowered, so that the followability of the combustion chamber wall surface temperature to the gas temperature in the cylinder can be improved, The thermal efficiency of the internal combustion engine can be improved.

1 is a diagram showing a schematic configuration of an internal combustion engine according to an embodiment of the present invention. It is a figure which shows the structural example of the thin film 20 for heat insulation. It is a figure which shows the other structural example of the thin film 20 for heat insulation. It is a figure which shows the structural example of the heat insulating material. It is a figure which shows the other structural example of the heat insulating material. It is a figure which shows the example of a waveform at the time of changing the combustion chamber wall surface temperature Twall with respect to a crank angle. It is a figure which shows the calculation result which investigated the fuel consumption improvement effect at the time of changing the swing width | variety (DELTA) T of the combustion chamber wall surface temperature Twall. It is a figure which shows the other structural example of the thin film 20 for heat insulation. It is a figure which shows the other structural example of the thin film 20 for heat insulation. It is a figure which shows the other structural example of the thin film 20 for heat insulation. It is a figure which shows the calculation result which investigated the change of the combustion chamber wall surface temperature Twall in 1 cycle, changing the thickness t1 of the thin film 20 for heat insulation. It is a figure which shows the characteristic of the swing width | variety (DELTA) T of the combustion chamber wall surface temperature Twall with respect to thickness t1 of the thin film 20 for heat insulation. It is a figure which shows the calculation result which investigated the change of the combustion chamber wall surface temperature Twall in 1 cycle, changing thickness t0 of the thin film for heat insulation (single material). It is a figure which shows the characteristic of the swing width | variety (DELTA) T of the combustion chamber wall surface temperature Twall with respect to thickness t0 of the thin film for heat insulation (single material). It is a figure which shows the other structural example of the thin film 20 for heat insulation. It is a figure which shows the other structural example of the thin film 20 for heat insulation. It is a figure which shows the other structural example of the thin film 20 for heat insulation. It is a figure which shows the calculation result which investigated the change of the combustion chamber wall surface temperature in one cycle, changing the thickness t2 of the heat insulating material. It is a figure which shows the characteristic of the swing width | variety (DELTA) T of the combustion chamber wall surface temperature Twall with respect to thickness t2 of the heat insulating material. It is a figure which shows the other structural example of the thin film 20 for heat insulation. It is a figure which shows the other structural example of the thin film 20 for heat insulation. It is a figure which shows the other structural example of the thin film 20 for heat insulation. It is a figure which shows the other structural example of the thin film 20 for heat insulation. It is a figure which shows the other structural example of the thin film 20 for heat insulation.

  Preferred embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine 1 according to an embodiment of the present invention, and shows an outline of an internal configuration viewed from a direction orthogonal to the axial direction of a cylinder 11. The internal combustion engine (engine) 1 includes a cylinder block 9 and a cylinder head 10, and a cylinder 11 is formed by the cylinder block 9 and the cylinder head 10. A piston 12 that reciprocates in the axial direction is accommodated in the cylinder 11. A space surrounded by the top surface 12 a of the piston 12, the inner wall surface 9 a of the cylinder block 9, and the lower surface 10 a of the cylinder head 10 forms a combustion chamber 13. An intake port 14 that communicates with the combustion chamber 13 and an exhaust port 15 that communicates with the combustion chamber 13 are formed in the cylinder head 10. Further, an intake valve 16 that opens and closes the boundary between the intake port 14 and the combustion chamber 13 and an exhaust valve 17 that opens and closes the boundary between the exhaust port 15 and the combustion chamber 13 are provided. A cooling water jacket 18 is formed in the cylinder block 9, and cooling of the internal combustion engine 1 is performed by supplying cooling water to the cooling water jacket 18.

  In FIG. 1, for convenience of explanation, illustration of configurations of a fuel injection valve, a spark plug, and the like is omitted, but the internal combustion engine 1 according to the present embodiment is a compression self-ignition internal combustion engine such as a diesel engine. It may be a spark ignition type internal combustion engine such as a gasoline engine. In the case of a compression self-ignition internal combustion engine, for example, when the piston 12 is located near the compression top dead center, the fuel in the combustion chamber 13 is self-ignited by injecting fuel into the combustion chamber 13 from the fuel injection valve. And burn. In the case of a spark ignition type internal combustion engine, the air-fuel mixture in the combustion chamber 13 is ignited by flame propagation by igniting the air-fuel mixture in the combustion chamber 13 by spark discharge of the spark plug at the ignition timing. The combustion gas in the combustion chamber 13 is discharged to the exhaust port 15 in the exhaust stroke.

  In the present embodiment, heat transfer from the combustion gas in the combustion chamber 13 to the base material is suppressed on the wall surface facing (facing) the combustion chamber 13 of at least a part of the base material forming the combustion chamber 13. A heat insulating thin film 20 is formed. Here, examples of the base material forming the combustion chamber 13 include a cylinder block (cylinder liner) 9, a cylinder head 10, a piston 12, an intake valve 16, and an exhaust valve 17. And, as wall surfaces facing the combustion chamber 13, a cylinder block inner wall surface (cylinder liner inner wall surface) 9a, a cylinder head lower surface 10a, a piston top surface 12a, an intake valve top surface (umbrella bottom surface) 16a, and an exhaust valve top surface ( Any one or more of the umbrella bottom surface 17a can be mentioned. FIG. 1 shows an example in which a heat insulating thin film 20 is formed on each of the cylinder block inner wall surface 9a, the cylinder head lower surface 10a, the piston top surface 12a, the intake valve top surface 16a, and the exhaust valve top surface 17a. However, it is not always necessary to form the heat insulating thin film 20 on the cylinder block inner wall surface 9a, the cylinder head lower surface 10a, the piston top surface 12a, the intake valve top surface 16a, and the exhaust valve top surface 17a. That is, the heat insulating thin film 20 can be formed on any one or more of the cylinder block inner wall surface 9a, the cylinder head lower surface 10a, the piston top surface 12a, the intake valve top surface 16a, and the exhaust valve top surface 17a.

  Furthermore, in the present embodiment, the heat insulating thin film 20 is configured to include a plurality of types of heat insulating materials that are different in both thermal conductivity and heat capacity per unit volume. Each of the plurality of types of heat insulating materials has a thermal conductivity equal to or lower than that of the base material, and has a heat capacity per unit volume lower than or substantially equal to that of the base material. Hereinafter, a configuration example of the heat insulating thin film 20 will be described.

"Example 1"
FIG. 2 is a cross-sectional view illustrating a configuration example of the heat insulating thin film 20. In the configuration example (Example 1) shown in FIG. 2, the heat insulating thin film 20 formed on the wall surface 30 a facing the combustion chamber 13 of the base material 30 forming the combustion chamber 13 is formed in a number of granular shapes. A heat insulating material (first heat insulating material) 21 and a heat insulating material (second heat insulating material) 22 formed in a film shape are included. The base material 30 here may be a cylinder block (cylinder liner) 9, a cylinder head 10, a piston 12, or an intake valve 16. The exhaust valve 17 may be used. That is, the wall surface 30a of the base material 30 may be a cylinder block inner wall surface (cylinder liner inner wall surface) 9a, a cylinder head lower surface 10a, or a piston top surface 12a. It may be the intake valve top surface 16a or the exhaust valve top surface 17a.

  The heat insulating material 22 has a thermal conductivity equal to or lower than that of the base material 30 (or lower than that of the base material 30), and has a heat capacity per unit volume lower than that of the base material 30 or substantially equivalent to that of the base material 30. On the other hand, the heat insulating material 21 has a thermal conductivity lower than that of the base material 30 and a heat capacity per unit volume lower than that of the base material 30, and is lower than that of the heat insulating material 22 and lower than that of the heat insulating material 22. It has a heat capacity per unit volume. The heat insulating material 22 is coated or joined on the wall surface 30 a of the base material 30 and comes into contact with the combustion gas in the combustion chamber 13. The heat insulating material 22 has heat resistance and pressure resistance against high temperature and high pressure combustion gas in the combustion chamber 13, has a heat resistant temperature higher than that of the heat insulating material 21, and has higher strength than the heat insulating material 21. . On the other hand, the large number of heat insulating materials 21 are mixed in the heat insulating material 22 so that they do not come into contact with the combustion gas in the combustion chamber 13. The heat insulating material 22 here protects the heat insulating material 21 from the high temperature and high pressure combustion gas in the combustion chamber 13 in addition to the function of suppressing the heat transfer from the combustion gas in the combustion chamber 13 to the base material 30. It also has a function as a material. Furthermore, the heat insulating material 22 also has a function as an adhesive material that connects many heat insulating materials 21. On the other hand, the heat insulating material 21 has a function of lowering the thermal conductivity and the heat capacity per unit volume in the entire heat insulating thin film 20. In addition, although illustration is abbreviate | omitted in FIG. 2, between thin film 20 for heat insulation (heat insulation material 22) and the base material 30, joining and coating of the thin film 20 for heat insulation (heat insulation material 22) and the base material 30 are carried out. A thin intermediate material for strengthening may be formed. As a technique for strengthening the bonding and coating between the heat insulating thin film 20 and the base material 30, it is possible to reinforce the bonding between substances, or to make the thermal expansion coefficient of the heat insulating thin film 20 and the base material 30 equal to each other. It is conceivable to prevent peeling due to impact. Therefore, as the intermediate material, an intermediate material for strengthening the bond between the heat insulating thin film 20 and the base material 30 or an intermediate material that reduces the difference in linear expansion coefficient between the heat insulating thin film 20 and the base material 30 is used. It is preferable. Moreover, it is preferable that an intermediate material has a thermal conductivity comparable as the heat insulating material 21 or the heat insulating material 22, and the heat capacity per unit volume. 2 shows an example in which a large number of heat insulating materials 21 are mixed inside the heat insulating material 22 in a state where the surface of the heat insulating thin film 20 (heat insulating material 22) is smoothed, for example, as shown in FIG. 3A. As described above, the heat insulating material 21 may be mixed in the heat insulating material 22 in a state where some unevenness is generated on the surface of the heat insulating thin film 20 (heat insulating material 22).

Specific examples of the heat insulating material 22 include, for example, a solid ceramic such as zirconia (ZrO ₂ ), silicon, titanium, or zirconium, an organic silicon compound containing carbon, oxygen, silicon, or the like, or high strength and high heat resistance. And ceramic fibers. Further, a plurality of these materials can be used in combination for the heat insulating material 22. In ceramic (zirconia), the thermal conductivity λ is about 2.5 [W / (m · K)], and the heat capacity ρC per unit volume is about 2500 × 10 ³ [J / (m ³ · K)]. The heat resistance temperature Tm is about 2700 [° C.], and the strength (bending strength) σ is about 1470 [MPa]. Regarding ceramics here, in addition to zirconia, cordierite (thermal conductivity λ is about 4 [W / (m · K)], and heat capacity ρC per unit volume is 1900 × 10 ³ [J / (m ³ · K)] grade) can also be used, and alumina-based or silicon nitride-based ceramics can also be partially mixed and used. In addition, the ceramic fiber here may be configured to include, for example, silicon, titanium, or zirconium, and the thermal conductivity λ is about 2.5 [W / (m · K)], and is per unit volume. The heat capacity ρC is about 1600 × 10 ³ [J / (m ³ · K)], the heat resistance temperature Tm is about 1300 [° C.], and the strength (tensile strength) σ is about 3300 [MPa].

On the other hand, specific examples of the heat insulating material 21 include, for example, hollow ceramic beads, hollow glass beads, a heat insulating material having a fine porous structure mainly composed of silica (silicon dioxide, SiO ₂ ), silica airgel, and the like. it can. Further, a combination of a plurality of these materials can be used for the heat insulating material 21. In hollow ceramic beads, the thermal conductivity λ is about 0.1 [W / (m · K)], and the heat capacity ρC per unit volume is about 300 × 10 ³ [J / (m ³ · K)]. The heat resistant temperature Tm is about 1600 [° C.], and the strength (tensile strength) σ is about 70 [MPa]. As for the heat insulating material having a microporous structure, titanium dioxide (TiO ₂ ) can be mixed and used in addition to the main component silica, and the thermal conductivity λ is 0.04 [W / ( m · K)], the heat capacity ρC per unit volume is about 400 × 10 ³ [J / (m ³ · K)], the heat resistant temperature Tm is about 1025 [° C.], and the strength is extremely weak. . In silica airgel, the thermal conductivity λ is about 0.02 [W / (m · K)], and the heat capacity ρC per unit volume is about 190 × 10 ³ [J / (m ³ · K)]. The heat-resistant temperature Tm is about 1200 [° C.], and the strength is extremely weak.

The structural example of the heat insulating material 21 is shown to FIG. 3B and 3C. In the example shown in FIG. 3B, the heat insulating material 21 is a heat insulating material having a hollow structure in which a hollow portion 21a made of decompressed air or inert gas is formed inside a shell portion 21b made of zirconia, glass, or the like. And in the example shown to FIG. 3C, the heat insulating material 21 has the multilayer structure by the shell part 21b and the coat layer 21c because the coat layer 21c is formed in the outer side of the shell part 21b by glass. For the coating layer 21c here, it is preferable to use a material having a thermal conductivity as small as that of the shell (glass) 21b, such as zirconia, and the thickness is preferably as thin as several μm. By covering the shell (glass) 21b with the coat layer (zirconia) 21c, the heat-resistant temperature of the heat insulating material 21 can be increased. In the example of the heat insulating material 21 shown in FIG. 3B, when borosilicate glass is used for the shell portion 21b, the thermal conductivity λ is about 0.07 [W / (m · K)], and the heat capacity per unit volume. ρC is about 220 × 10 ³ [J / (m ³ · K)]. In the example of the heat insulating material 21 shown in FIG. 3C, when borosilicate glass is used for the shell portion 21b and zirconia is used for the coat layer 21c, the thermal conductivity λ is about 0.35 [W / (m · K)]. The heat capacity ρC per unit volume is about 512 × 10 ³ [J / (m ³ · K)].

Specific examples of the base material 30 include iron (steel), aluminum or an aluminum alloy, or ceramic. In iron, the thermal conductivity λ is about 80.3 [W / (m · K)], and the heat capacity ρC per unit volume is about 3500 × 10 ³ [J / (m ³ · K)]. In aluminum, the thermal conductivity λ is about 193 [W / (m · K)], and the heat capacity ρC per unit volume is about 2400 × 10 ³ [J / (m ³ · K)] (almost equivalent to zirconia). ). For example, when iron (steel) is used for the base material 30, ceramic (zirconia) is used for the heat insulating material 22, and hollow ceramic beads are used for the heat insulating material 21, the heat conductivity and the heat capacity per unit volume of the heat insulating material 22 are the base material 30. The heat conductivity of the heat insulating material 21 and the heat capacity per unit volume are lower than those of the heat insulating material 22. And the heat-resistant temperature and intensity | strength of the heat insulating material 22 become higher than the heat insulating material 21. FIG.

  As described above, in the cycle of the internal combustion engine, the in-cylinder gas temperature Tg changes every moment, but by changing the combustion chamber wall surface temperature Twall to follow the in-cylinder gas temperature Tg, The value of (Tg−Twall) can be reduced, and the heat loss Q in the cylinder can be reduced. As a result, the thermal efficiency of the internal combustion engine can be improved and the fuel consumption can be improved. Here, FIGS. 4 and 5 show the calculation results obtained by examining the influence of the fuel consumption on the fluctuation range (swing width) ΔT of the combustion chamber wall surface temperature Twall. FIG. 4 shows an example of a waveform when the combustion chamber wall surface temperature Twall is changed with respect to the crank angle (compression top dead center is 0 °). The swing width ΔT of the combustion chamber wall surface temperature Twall in one cycle is 500 ° C. The waveforms at 1000 ° C. and 1500 ° C. are respectively shown in comparison with the case where the combustion chamber wall surface temperature Twall hardly changes (base condition). In FIG. 4, the waveform of ΔT = 1500 ° C. corresponds to the waveform when the combustion chamber wall surface temperature Twall changes substantially following the cylinder gas temperature Tg. FIG. 5 shows the calculation results of examining the fuel efficiency improvement effect when the swing width ΔT of the combustion chamber wall surface temperature Twall in one cycle is changed to 500 ° C., 1000 ° C., and 1500 ° C. as shown in FIG. In the calculation, the operating conditions of the internal combustion engine (diesel engine) are set to an engine speed of 2100 rpm and an indicated mean effective pressure Pi = 1.6 MPa. In FIG. 5, circles (◯) indicate the results when the combustion chamber wall temperature (base wall temperature) in the intake stroke hardly increases relative to the wall temperature in the base condition, and triangles (Δ) These show the results when the combustion chamber wall surface temperature (base wall temperature) during the intake stroke rises by 100 ° C. relative to the wall surface temperature under the base conditions. As shown in FIG. 5, it can be seen that the fuel efficiency improvement effect can be improved by increasing the swing width ΔT of the combustion chamber wall surface temperature Twall. However, even if the swing width ΔT of the combustion chamber wall surface temperature Twall increases, the fuel efficiency improvement effect decreases as the base wall temperature increases. Therefore, in order to further improve the fuel efficiency improvement effect, it is preferable to increase the swing width ΔT of the combustion chamber wall surface temperature Twall without substantially increasing the base wall temperature. In addition, the heat shielding rate [%] on the horizontal axis in FIG. 5 is expressed by the following equation (2) using the heat loss amount Qb under the base condition and the heat loss amount Qs when the wall surface temperature Twall is changed. expressed.

  Heat shielding rate = (Qb−Qs) / Qb × 100 [%] (2)

In order to increase the swing width ΔT of the combustion chamber wall surface temperature Twall almost without increasing the base wall temperature, the heat insulating film formed on the wall surface facing the combustion chamber has low thermal conductivity and heat capacity per unit volume. It is desirable. However, as described above, a single material with low thermal conductivity and low heat capacity per unit volume has many materials with low heat resistance and strength, such as high temperature and high speed gas flow and high pressure as in the cylinder of an internal combustion engine. Does not have heat resistance and strength to withstand On the other hand, a single material with high heat resistance and strength that can withstand high-temperature, high-speed gas flow and high pressure has insufficient thermal conductivity and low heat capacity per unit volume. The swing width ΔT of Twall decreases. Furthermore, heat is transmitted to the heat insulating film and is easily accumulated, and the base wall temperature rises. When the base wall temperature rises, the following adverse effects (1) to (5) occur.
(1) The intake gas receives heat and expands during the intake stroke, so that the charging efficiency is reduced and the output is reduced.
(2) When the working gas receives heat during the compression stroke and the pressure in the cylinder rises, negative work in the compression stroke increases and fuel consumption decreases.
(3) When the average gas temperature rises due to heat reception during the intake / compression stroke, the specific heat ratio of the in-cylinder gas is lowered and the cycle efficiency is lowered.
(4) Since the gas flow in the cylinder becomes laminar due to the rise in the compression end gas temperature, the degree of mixing of fuel and air in the air-fuel mixture formation process decreases, and the amount of soot generated increases.
(5) The amount of nitrogen oxide (NOx) produced increases as the combustion temperature rises as the compression end gas temperature rises.

  On the other hand, in the configuration example shown in FIG. 2, the heat insulating material 21 having a low thermal conductivity and a low heat capacity per unit volume is mixed in the heat insulating material 22 having a high heat resistance and high strength, thereby burning the heat insulating material 21. It is possible to protect against high temperature and high pressure combustion gas in the chamber 13. Therefore, the heat insulating material 21 has a low thermal conductivity and a low heat capacity per unit volume without being restricted to sufficiently ensure heat resistance and pressure resistance against high temperature and high pressure combustion gas in the combustion chamber 13. The degree of freedom of the selectivity of the heat insulating material that places importance on this is increased, and a heat insulating material having a sufficiently low thermal conductivity and heat capacity per unit volume can be used. Therefore, the heat conductivity and the heat capacity per unit volume in the entire heat insulating thin film 20 can be sufficiently reduced. Accordingly, the swing width ΔT of the combustion chamber wall surface temperature Twall can be increased while suppressing an increase in the base wall temperature, and the followability of the combustion chamber wall surface temperature Twall to the in-cylinder gas temperature Tg can be improved. As a result, the heat loss Q of the internal combustion engine 1 can be reduced to improve the thermal efficiency, and the fuel consumption can be improved. Furthermore, the swing width ΔT of the combustion chamber wall surface temperature Twall can be adjusted by adjusting the thermal conductivity of the heat insulating materials 21 and 22 and the heat capacity per unit volume by selecting the material of the heat insulating materials 21 and 22. In addition, since the exhaust temperature can be raised, the exhaust emission can be reduced by increasing the activity of the catalyst installed downstream of the engine, and more effective use of exhaust energy in a turbocharged supercharged engine. Can do. In particular, in a supercharged engine for the purpose of reducing exhaust emission and increasing thermal efficiency, the exhaust temperature decrease due to the decrease in the combustion temperature becomes significant, so the effect of increasing the exhaust temperature according to the present embodiment is further enhanced.

  In the configuration example shown in FIG. 2, the volume ratio occupied by the heat insulating material 21 in the heat insulating thin film 20, that is, the mixing ratio of the heat insulating material 21 may be changed according to the position inside the heat insulating material 22. it can. For example, the mixing ratio of the heat insulating material 21 can be changed according to the position inside the heat insulating material 22 by making the particle sizes of the heat insulating material 21 uneven and changing the heat insulating material 21 according to the position inside the heat insulating material 22. Further, the mixing ratio of the heat insulating material 21 can be made different depending on the position inside the heat insulating material 22 by changing the number of heat insulating materials 21 mixed per unit volume depending on the position inside the heat insulating material 22. it can. According to this configuration, the thermal conductivity of the entire heat insulating thin film 20 and the heat capacity per unit volume can be distributed, and the swing width ΔT of the combustion chamber wall surface temperature Twall varies depending on the position of the combustion chamber wall surface. (With a distribution).

  Alternatively, for example, as shown in FIG. 6A, a large number of heat insulating materials 21 can be regularly arranged inside the heat insulating materials 22. In the example shown in FIG. 6A, the heat insulating materials 21 having a single particle diameter are arranged at equal intervals in the thickness direction and the in-plane direction (the direction perpendicular to the thickness direction) of the heat insulating thin film 20. By arranging the heat insulating material 21 regularly inside the heat insulating material 22, the heat insulating material 21 and the heat insulating material 22 are uniformly distributed, and the heat insulating material 21 is locally biased with respect to the thickness direction and the in-plane direction of the heat insulating thin film 20. It can be prevented from existing. As a result, the heat insulating thin film 20 having uniform thermophysical properties (low thermal conductivity and low heat capacity) can be realized. Furthermore, since the portion where the heat insulating material 22 is locally thin (thinned) can be avoided, the probability that there is a structural defect that affects the strength of the heat insulating thin film 20 can be suppressed, and the strength of the heat insulating thin film 20 is increased. be able to. It should be noted that the regular arrangement of the heat insulating material 21 inside the heat insulating material 22 can be performed using a known technique such as Brian T. Holland et al., Science, 281, 538-540 (1998). . By slowly filtering the monodispersed spherical particles dispersed in a solution such as water, a deposit of regularly arranged spherical particles can be obtained. Therefore, the structure shown in FIG. 6A is obtained by depositing the heat insulating material 21 having a single particle diameter by using this technique and then pouring the heat insulating material 22 (binder layer) in a liquid state between the deposited bodies and firing. Is feasible.

In the configuration example shown in FIG. 2, the heat insulating material 21 is mixed into the heat insulating material 22 to form the heat insulating thin film 20. However, as shown in FIG. Many can be formed inside the material 22. In the configuration example shown in FIG. 6B, the heat insulating thin film 20 is made of a material having a thermal conductivity lower than that of the base material 30 and a heat capacity per unit volume lower than that of the base material 30 or substantially equivalent to that of the base material 30. A heat insulating material (foam heat insulating material) 22 having a large number of bubbles 31 formed therein is included. In the bubble 31 (air), the thermal conductivity λ is about 0.02 [W / (m · K)], and the heat capacity ρC per unit volume is 2.3 × 10 ³ [J / (m ³ · K). )] Degree. The material forming the heat insulating material 22 has heat resistance and pressure resistance against high-temperature and high-pressure combustion gas in the combustion chamber 13. A specific example of the material forming the heat insulating material 22 (with the bubbles 31 formed therein) is the same as the specific example of the heat insulating material 22 in the configuration example shown in FIG. For example, when iron (steel) is used for the base material 30 and ceramic (zirconia) is used for the material forming the heat insulating material 22, the heat conductivity and the heat capacity per unit volume of the material forming the heat insulating material 22 are the base material 30. And higher than the bubble 31.

  In the configuration example shown in FIG. 6B as well, the thermal conductivity and the heat capacity per unit volume in the entire heat insulating thin film 20 can be sufficiently lowered, so that the combustion chamber wall temperature Twalll swing while suppressing the rise in the base wall temperature. The width ΔT can be increased, and the followability of the combustion chamber wall surface temperature Twall to the in-cylinder gas temperature Tg can be improved. As a result, the thermal efficiency of the internal combustion engine 1 can be improved. In the configuration example shown in FIG. 6B as well, for example, the diameters of the bubbles 31 are uneven, and the volume ratio of the bubbles 31 in the heat insulating thin film 20 (the formation ratio of the bubbles 31) depends on the position inside the heat insulating material 22. By changing it, the swing width ΔT of the combustion chamber wall surface temperature Twall can be varied according to the position of the combustion chamber wall surface. Alternatively, for example, as shown in FIG. 6C, a large number of bubbles 31 can be regularly arranged inside the heat insulating thin film 20 (heat insulating material 22). In the example shown in FIG. 6C, the bubbles 31 having a single particle diameter are arranged at equal intervals in the thickness direction and the in-plane direction (the direction perpendicular to the thickness direction) of the heat insulating thin film 20. By arranging the bubbles 31 regularly inside the heat insulating material 22, it is possible to realize the heat insulating thin film 20 with uniform thermal properties (low thermal conductivity and low heat capacity) and to increase the strength of the heat insulating thin film 20. For the regular arrangement of the bubbles 31 in the heat insulating material 22, for example, Brian T. Holland et al., Science, 281, 538-540 (1998), etc., that is, monodisperse spherical particles are made of water or the like. It is possible to use a method of obtaining a deposit of regularly arranged spherical particles by slowly filtering a solution dispersed in a solution. At that time, a material (for example, resin beads) that is gasified by firing is used as the spherical particles, and after depositing resin beads having a single particle diameter, a heat insulating material 22 (binder layer) in a liquid state between the deposited bodies. ) And fired. If the resin beads are gasified and burned off by heating to several hundred degrees or more at the time of firing, the place where the resin beads are located becomes the bubbles 31. Therefore, the structure shown in FIG. 6C can be realized.

  Next, the result of the analysis (numerical calculation) performed by the present inventor will be described. When the internal combustion engine 1 is a supercharged direct injection diesel engine, the combustion chamber wall surface temperature Twall in one cycle is changed while changing the thickness t1 of the heat insulating thin film 20 (heat insulating material 22) for the configuration example shown in FIG. 6B. Changes were calculated and examined. The calculation results are shown in FIGS. FIG. 7 shows the waveform of the combustion chamber wall surface temperature Twall with respect to the crank angle (compression top dead center is 0 °), and the waveform when the thickness t1 of the heat insulating thin film 20 is 10 μm, 50 μm, 100 μm, 200 μm, and 500 μm. Each is shown. FIG. 8 shows the characteristic of the swing width ΔT of the combustion chamber wall surface temperature Twall with respect to the thickness t1 of the heat insulating thin film 20.

  Further, as a comparative example in which the heat insulating thin film is made of a single material, the change in the combustion chamber wall temperature Twall in one cycle was calculated and examined while changing the thickness t0 of the heat insulating thin film (single material). . The calculation results are shown in FIGS. FIG. 9 shows a waveform of the combustion chamber wall surface temperature Twall with respect to the crank angle (compression top dead center is 0 °), and shows waveforms when the thickness t0 of the heat insulating thin film is 10 μm, 50 μm, 100 μm, and 500 μm, respectively. FIG. 10 shows characteristics of the swing width ΔT of the combustion chamber wall surface temperature Twall with respect to the thickness t0 of the heat insulating thin film.

In calculating the combustion chamber wall surface temperature Twall, the displacement of one cylinder is 550 cc, the compression ratio is 16, the engine speed is 2000 rpm, the fuel injection amount is 50 mm ³ / st, and the indicated mean effective pressure is 1.6 MPa. Appropriate. In the configuration example shown in FIG. 6B, the thermal conductivity λ and the heat capacity ρC per unit volume of the material forming the heat insulating material 22 are λ = 2.5 [W / (m · K)], ρC = 2520. × 10 ³ [J / (m ³ · K)] (equivalent to zirconia), the volume ratio occupied by the bubbles 31 (air) in the heat insulating thin film 20 (heat insulating material 22) was 80%. Further, in the comparative example, the thermal conductivity λ and the heat capacity ρC per unit volume of a single material (the entire heat insulating thin film) constituting the heat insulating thin film are λ = 2.5 [W / (m · K)]. ΡC = 2520 × 10 ³ [J / (m ³ · K)] (equivalent to zirconia).

  In the comparative example, as shown in FIGS. 9 and 10, the swing width ΔT of the combustion chamber wall surface temperature Twall is only about 125 ° C. (when t0 = 100 μm), and the fuel efficiency improvement effect is about 2% at the maximum (t0). = 100 μm). When the thickness t0 of the heat insulating thin film is smaller than 100 μm, the swing width ΔT of the combustion chamber wall surface temperature Twall is decreased, so that the fuel efficiency improvement effect is reduced and hardly obtained. On the other hand, if the thickness t0 of the heat insulating thin film is thicker than 100 μm, the base wall temperature rises, so that the fuel efficiency improvement effect is reduced and hardly obtained.

  On the other hand, in Example 1 (configuration example shown in FIG. 6B), as shown in FIGS. 9 and 10, the swing width ΔT of the combustion chamber wall surface temperature Twall can be significantly increased to about 550 ° C. to 650 ° C. The fuel efficiency improvement effect can be greatly increased to about 7 to 8%. 9 and 10, in the range of t1 = 50 μm to 200 μm, a swing width ΔT of about 550 ° C. to 650 ° C. is obtained with almost no increase in the base wall temperature, and a fuel consumption of about 7 to 8%. Improvement effect is obtained. When t1 = 100 μm, the swing width ΔT is maximized. As described above, it was confirmed that the swing width ΔT of the combustion chamber wall surface temperature Twall can be significantly increased by the configuration of the first embodiment, and a fuel efficiency improvement effect of about 7 to 8% can be obtained.

"Example 2"
11 and 12 are diagrams showing another configuration example of the heat insulating thin film 20, and FIG. 11 is a diagram viewed from a direction (normal direction) that matches the normal line of the wall surface 30a of the base material 30. 12 shows a cross-sectional view. In the following description of the second embodiment, the same or corresponding components as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  In the configuration example shown in FIGS. 11 and 12 (Example 2), the heat insulating material 22 in which a large number of granular heat insulating materials 21 are mixed is formed in a fiber shape. A large number of heat insulating materials 22 formed in a fiber shape are spread on the wall surface 30 a of the base material 30. FIG. 12 shows an example in which a large number of heat insulating materials 22 formed in a fiber shape are stacked in layers. And FIG. 11 has shown the example which formed the thin film 20 for heat insulation by weaving (knitting) many heat insulating materials 22 formed in the fiber form. Specific examples of the heat insulating materials 21 and 22 and the base material 30 are the same as those in the first embodiment. Although not shown in FIGS. 11 and 12, a thin intermediate material for strengthening the bonding between the heat insulating material 22 and the base material 30 is formed between the heat insulating material 22 and the base material 30. Alternatively, a thin intermediate material for strengthening the bonding between the fibrous heat insulating materials 22 may be formed between the heat insulating materials 22. The intermediate material here preferably has a thermal conductivity comparable to that of the heat insulating material 21 or the heat insulating material 22 and a heat capacity per unit volume.

  Also in the second embodiment, the swing width ΔT of the combustion chamber wall surface temperature Twall can be increased while suppressing an increase in the base wall temperature, and the followability of the combustion chamber wall surface temperature Twall to the in-cylinder gas temperature Tg can be improved. it can. As a result, the thermal efficiency of the internal combustion engine 1 can be improved. In the second embodiment, as in the first embodiment, a large number of bubbles 31 can be formed inside the fibrous heat insulating material 22 instead of the heat insulating material 21. Further, in the second embodiment, similarly to the first embodiment, for example, the diameters of the heat insulating materials 21 (or the bubbles 31) are uneven, and the volume ratio of the heat insulating materials 21 (or the bubbles 31) in the heat insulating thin film 20 is set to the heat insulating materials 22. The swing width ΔT of the combustion chamber wall surface temperature Twall can be varied according to the position of the combustion chamber wall surface.

"Example 3"
FIG. 13 is a cross-sectional view showing another configuration example of the heat insulating thin film 20. In the following description of the third embodiment, the same reference numerals are given to the same or corresponding configurations as those of the first and second embodiments, and duplicate descriptions are omitted.

  In the configuration example (Example 3) shown in FIG. 13, the film-like heat insulating material 21 is formed on the wall surface 30 a of the base material 30 by coating or bonding. A film-like heat insulating material 22 is formed on the heat insulating material 21 so as to cover the surface of the heat insulating material 21 and is in contact with the combustion gas in the combustion chamber 13. As described above, the heat insulating thin film 20 has a layer structure including the film-like heat insulating materials 21 and 22, and the heat insulating material 22 is an upper layer than the heat insulating material 21. Specific examples of the heat insulating materials 21 and 22 and the base material 30 are the same as those in the first embodiment. Although not shown in FIG. 13, a thin intermediate material for strengthening the bonding and coating between the heat insulating material 21 and the base material 30 is formed between the heat insulating material 21 and the base material 30. Alternatively, a thin intermediate material for strengthening the bonding and coating between the heat insulating material 21 and the heat insulating material 22 may be formed between the heat insulating material 21 and the heat insulating material 22. The intermediate material here preferably has the same thermal conductivity as the heat insulating material 21 or the heat insulating material 22 and a heat capacity per unit volume.

  In Example 3, the heat insulating material 21 having a low thermal conductivity and a low heat capacity per unit volume is covered with a heat insulating material 22 having a high heat resistance and a high strength, whereby the heat insulating material 21 is heated at a high temperature and a high pressure in the combustion chamber 13. Can be protected from. Therefore, the heat insulating material 21 has a sufficient thermal conductivity and heat capacity per unit volume without being restricted by ensuring sufficient heat resistance and pressure resistance against the high-temperature and high-pressure combustion gas in the combustion chamber 13. A low heat insulating material can be selected, and the heat conductivity and heat capacity per unit volume of the entire heat insulating thin film 20 can be sufficiently reduced. Therefore, it is possible to increase the swing width ΔT of the combustion chamber wall surface temperature Twall while suppressing an increase in the base wall temperature, and to improve the followability of the combustion chamber wall surface temperature Twall to the in-cylinder gas temperature Tg. As a result, the thermal efficiency of the internal combustion engine 1 can be improved.

  Here, the result of the analysis (numerical calculation) performed by the present inventor will be described. When the internal combustion engine 1 is a supercharged direct injection diesel engine, the change in the combustion chamber wall surface temperature Twall in one cycle is calculated and examined while changing the thickness t2 of the heat insulating material 21 for the configuration example shown in FIG. It was. The calculation results are shown in FIGS. FIG. 14 shows the waveform of the combustion chamber wall surface temperature Twall with respect to the crank angle (compression top dead center is 0 °), and shows the waveforms when the thickness t2 of the heat insulating material 21 is 10 μm, 50 μm, 100 μm, and 190 μm, respectively. Note that the thickness of the heat insulating material 22 is constant (10 μm). FIG. 15 shows characteristics of the swing width ΔT of the combustion chamber wall surface temperature Twall with respect to the thickness t2 of the heat insulating material 21.

In calculating the combustion chamber wall surface temperature Twall, the displacement of one cylinder is 550 cc, the compression ratio is 16, the engine speed is 2000 rpm, the fuel injection amount is 50 mm ³ / st, and the indicated mean effective pressure is 1.6 MPa. Appropriate. The thickness of the heat insulating material 22 is set to a constant value of 10 μm, and the heat conductivity λ and the heat capacity ρC per unit volume of the heat insulating material 22 are λ = 2.5 [W / (m · K)], ρC = 2520. × 10 ³ [J / (m ³ · K)] (equivalent to zirconia), and the thermal conductivity λ and heat capacity ρC per unit volume of the heat insulating material 21 are λ = 0.04 [W / (m · K)] , ΡC = 400 × 10 ³ [J / (m ³ · K)] (equivalent to a heat insulating material having a microporous structure).

  In the configuration example shown in FIG. 13, as shown in FIGS. 14 and 15, the swing width ΔT of the combustion chamber wall surface temperature Twall can be greatly increased to about 420 ° C., and the fuel efficiency improvement effect is greatly increased to about 5%. Can be made. In the calculation results shown in FIGS. 14 and 15, a swing width ΔT of about 420 ° C. is obtained in the range of t2 = 10 μm to 50 μm. Furthermore, when t1 = 10 μm, the base wall temperature is hardly increased at 420 ° C. A swing width ΔT of about 5% is obtained, and a fuel efficiency improvement effect of about 5% is obtained. In addition, when the thickness t2 of the heat insulating material 21 is 50 μm or more, the fuel efficiency improvement effect is reduced from 5% due to the increase in the base wall temperature.

Example 4
16 and 17 are cross-sectional views showing other configuration examples of the heat insulating thin film 20. In the following description of the fourth embodiment, configurations similar to or corresponding to those of the first to third embodiments are denoted by the same reference numerals, and redundant description is omitted.

  In the configuration example (Example 4) shown in FIGS. 16 and 17, the heat insulating material 22 protrudes to the heat insulating material 21 side (base material 30 side) compared to the configuration example (Example 3) shown in FIG. 13. By providing the protrusion 22 a, the heat insulating thin film 20 has a structure in which the protrusion 22 a of the heat insulating material 22 enters the heat insulating material 21. Although FIG. 17 shows an example in which the protruding portions 22a are formed in a lattice shape, the protruding portions 22a are not necessarily formed in a lattice shape.

  Also in the fourth embodiment, the swing width ΔT of the combustion chamber wall surface temperature Twall can be increased while suppressing an increase in the base wall temperature, and the followability of the combustion chamber wall surface temperature Twall to the in-cylinder gas temperature Tg can be improved. it can. As a result, the thermal efficiency of the internal combustion engine 1 can be improved. Furthermore, in Example 4, since the joining area of the heat insulating material 21 and the heat insulating material 22 can be increased by the protrusion 22 a provided on the heat insulating material 22, the bonding strength between the heat insulating material 21 and the heat insulating material 22 is increased. be able to.

"Example 5"
18 and 19 are diagrams showing another configuration example of the heat insulating thin film 20, and FIG. 18 is a diagram viewed from a direction (normal direction) that matches the normal line of the wall surface 30a of the base material 30. 19 shows a cross-sectional view. In the following description of the fifth embodiment, the same or corresponding components as those of the first to fourth embodiments are denoted by the same reference numerals, and redundant description is omitted.

  In the configuration example (Example 5) shown in FIGS. 18 and 19, the shell-like heat insulating material 22 includes the heat insulating material 21 inside. A large number of heat insulating materials 22 including the heat insulating material 21 are spread on the wall surface 30 a of the base material 30. Specific examples of the heat insulating materials 21 and 22 and the base material 30 are the same as those in the first embodiment. Although not shown in FIGS. 18 and 19, a thin intermediate material is formed between the heat insulating material 22 and the base material 30 to strengthen the bonding and coating between the heat insulating material 22 and the base material 30. It may be. The intermediate material here preferably has a thermal conductivity comparable to that of the heat insulating material 21 or the heat insulating material 22 and a heat capacity per unit volume. FIG. 18 illustrates an example in which the outer shape of the heat insulating material 22 viewed from the normal direction is a substantially square shape, but the outer shape of the heat insulating material 22 may be other than a rectangular shape.

  In Example 5, the heat insulating material 22 having high heat resistance and high strength encloses the heat insulating material 21 having low thermal conductivity and heat capacity per unit volume, so that the heat insulating material 21 is burned at high temperature and high pressure in the combustion chamber 13. Can be protected from gas. Therefore, the heat insulating material 21 has a sufficient thermal conductivity and heat capacity per unit volume without being restricted by ensuring sufficient heat resistance and pressure resistance against the high-temperature and high-pressure combustion gas in the combustion chamber 13. A low heat insulating material can be selected, and the heat conductivity and heat capacity per unit volume of the entire heat insulating thin film 20 can be sufficiently reduced. Therefore, it is possible to increase the swing width ΔT of the combustion chamber wall surface temperature Twall while suppressing an increase in the base wall temperature, and to improve the followability of the combustion chamber wall surface temperature Twall to the in-cylinder gas temperature Tg. As a result, the thermal efficiency of the internal combustion engine 1 can be improved.

"Example 6"
FIG. 20 is a cross-sectional view illustrating another configuration example of the heat insulating thin film 20. In the following description of the sixth embodiment, the same or corresponding components as those in the first to fifth embodiments are denoted by the same reference numerals, and redundant description is omitted.

  In the configuration example (Example 6) shown in FIG. 20, the layers made of the heat insulating material 21 and the layers made of the heat insulating material 22 are alternately laminated a plurality of times, so that the heat insulating material 21 in the thickness direction of the heat insulating thin film 20 The heat insulating materials 22 are alternately arranged. The thickness of the heat insulating thin film 20 is, for example, about 100 μm, and the thickness of the heat insulating material 22 is preferably as thin as 10 μm or less (for example, about several μm). Specific examples of the heat insulating materials 21 and 22 and the base material 30 are the same as those of the first embodiment. As a structural example of the heat insulating material 21, for example, the structure shown in FIG. 3B or the structure shown in FIG. 3C can be used.

  In Example 6, the heat insulating material 21 is uniformly distributed with respect to the in-plane direction (the direction perpendicular to the thickness direction) of the heat insulating thin film 20, and the heat insulating material 21 is locally biased with respect to the in-plane direction of the heat insulating thin film 20. Can be prevented. As a result, it is possible to realize the heat insulating thin film 20 having a substantially uniform thermal conductivity in the thickness direction, and it is possible to suppress the presence of a location where heat easily escapes or a location where heat is difficult to escape. Therefore, the heat insulating thin film 20 having uniform thermophysical properties can be realized.

  In addition, about the heat insulation thin film 20 formed in the wall surface which faces in the combustion chamber 13, it can also be set as the structure which combined two or more of the structural examples by Examples 1-6, and heat insulation is carried out according to the formation location of the heat insulation thin film 20. The structure of the thin film 20 can be changed. And about the film thickness of the thin film 20 for heat insulation, it is not necessary to make it constant thickness, and can also be changed according to the formation location of the thin film 20 for heat insulation. Furthermore, the heat insulating thin film 20 of this embodiment can be used in combination with other heat insulating structures.

  As mentioned above, although the form for implementing this invention was demonstrated, this invention is not limited to such embodiment at all, and it can implement with a various form in the range which does not deviate from the summary of this invention. Of course.

Claims (15)

An internal combustion engine in which a heat insulating film is formed on a wall surface facing the combustion chamber of at least a part of the base material forming the combustion chamber,
The heat insulating film includes a first heat insulating material and a second heat insulating material,
The first heat insulating material has a lower thermal conductivity than the base material and a heat capacity per unit volume lower than the base material,
The second heat insulating material has a thermal conductivity equal to or lower than the base material,
The first heat insulating material has a lower thermal conductivity than the second heat insulating material and a heat capacity per unit volume lower than that of the second heat insulating material,
The first heat insulating material is a hollow ceramic bead, a hollow glass bead, a heat insulating material having a microporous structure, a silica airgel, or a combination thereof.
The second insulation is zirconia, silicon, titanium, zirconium, ceramic, Ri ceramic fiber or the plurality of Kumiawasedea,
In the cycle of the internal combustion engine, the heat insulating film can change the combustion chamber wall surface temperature within a range of 550 ° C. or more and 650 ° C. or less.
Internal combustion engine. The internal combustion engine according to claim 1, wherein the first heat insulating material is regularly arranged inside the second heat insulating material . The internal combustion engine according to claim 1 or 2,
An internal combustion engine in which the first heat insulating material is mixed in the second heat insulating material. An internal combustion engine according to claim 3,
The second heat insulating material in which the first heat insulating material is mixed is formed in a fiber shape,
An internal combustion engine in which a large number of second heat insulating materials formed in a fibrous shape are spread on the wall surface . The internal combustion engine according to claim 1,
The first heat insulating material is mixed inside the second heat insulating material,
An internal combustion engine in which a mixing ratio of the first heat insulating material varies depending on a position inside the second heat insulating material . The internal combustion engine according to claim 1 ,
The first heat insulating material is mixed inside the second heat insulating material,
An internal combustion engine in which the first heat insulating material is regularly arranged inside the second heat insulating material . An internal combustion engine according to claim 3 ,
The first heat insulating material is an internal combustion engine that is a heat insulating material having a hollow structure . The internal combustion engine according to claim 7 ,
An internal combustion engine in which the first heat insulating material has a multi-layer structure . The internal combustion engine according to claim 1 or 2 ,
A first heat insulating material is formed on the wall surface;
An internal combustion engine, wherein the second heat insulating material is formed on the first heat insulating material so as to cover the first heat insulating material . An internal combustion engine according to claim 9,
An internal combustion engine, wherein the second heat insulating material is provided with a protruding portion that protrudes toward the first heat insulating material . The internal combustion engine according to claim 1 or 2 ,
The second heat insulating material is an internal combustion engine that is a shell-shaped heat insulating material containing the first heat insulating material therein . The internal combustion engine according to claim 1 or 2 ,
The internal combustion engine in which the first heat insulating material and the second heat insulating material are alternately arranged in the thickness direction of the heat insulating film . The internal combustion engine according to claim 1 or 2 ,
An internal combustion engine in which a heat resistant temperature of the second heat insulating material is higher than a heat resistant temperature of the first heat insulating material . The internal combustion engine according to claim 1 or 2 ,
An internal combustion engine in which the strength of the second heat insulating material is higher than the strength of the first heat insulating material . The internal combustion engine according to claim 1 or 2 ,
The internal combustion engine , wherein the second heat insulating material has a thermal conductivity lower than that of the base material and a heat capacity per unit volume lower than or substantially equal to the base material .

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