JP2540878B2 - Insulation engine structure - Google Patents

Description

TECHNICAL FIELD The present invention relates to the structure of a heat insulating engine in a ceramic engine or the like.

[Conventional technology]

Conventionally, engine members such as adiabatic engines that use ceramic materials as heat insulating materials or heat resistant materials are, for example,
It is disclosed in JP-A-59-192647, JP-A-60-90955 and the like.

First, the cylinder liner of the adiabatic engine disclosed in Japanese Utility Model Laid-Open No. 59-192647 will be outlined with reference to FIG. The cylinder liner 34 of the adiabatic engine is configured such that the inner diameter of the liner upper portion 33 of the liner head 31 in which the cylinder head inner wall portion 32 and the cylinder liner upper portion 33 are integrally formed is larger than the inner diameter of the cylinder liner 34. ,
It is installed on the cylinder head 37 via the heat insulating gasket 35 on the outer surface of the liner upper portion 33.Therefore, contact between the cylinder liner upper portion 33 of the liner head 31 and the piston head 36 does not occur, and smooth and durable. Good operation will be possible.

Next, the structure of the heat insulation engine disclosed in Japanese Patent Laid-Open No. 60-90955 will be outlined with reference to FIG. Fifth
The structure of the adiabatic engine shown in the figure is the cylinder head 41
A heat reflecting surface is formed on an inner end wall 43 of a cylindrical portion 42 provided in the lower half of the cylinder head 41, and a head liner 44 made of ceramics is fitted to the cylindrical portion 42 of the cylinder head 41 with an empty portion 45 provided around the head liner 44. It is a thing. A heat insulating material 46 such as a ceramic fiber or a glass fiber is housed in a space 45 between the cylinder portion of the cylinder head 41 and the head liner 44. Further, the upper end wall 51 of the headliner 44 is connected to the inner end wall 43 of the cylindrical portion 42 of the cylinder head 41 via the gasket 53, and the lower end wall of the headliner 44 is connected to the cylinder block 47 and the cylinder liner 49 via the elastic gasket 54. Are pressed against the upper ends of the headliner 44 to alleviate stress concentration in the headliner 44 due to imbalance of tightening force and thermal deformation, and since the void 45 is formed, the headliner 44 surrounding the combustion chamber 40 Heat conduction to the cylinder head 41 is cut off, and heat dissipation can be suppressed. Further, heat radiation is reflected by the heat reflecting surface of the inner end wall 43, and heat transfer to the cylinder head 41 can be suppressed. Further, by accommodating the heat insulating material 46 such as a ceramic fiber in the empty space 45, it is possible to prevent convection of air in the empty space 45 and suppress heat transfer from the wall portion of the head liner 44 to the cylinder head 41. Reference numeral 48 in the figure
Indicates a piston.

[Problems to be solved by the invention]

However, it is extremely difficult to obtain sufficient heat insulating properties in a heat insulating engine member such as a cylinder head that uses the above ceramics as a heat insulating material and a heat resistant material, and the wall thickness increases in order to obtain sufficient heat insulating characteristics. There is a problem. That is, the portion facing the combustion chamber of the engine is made of ceramics such as silicon nitride having excellent heat resistance, heat insulation, and heat shock resistance, and can withstand high temperature combustion gas, but if the wall thickness is too large, The heat capacity increases,
Therefore, there is a problem that the inhalation efficiency decreases.

By the way, in the cylinder liner of the heat insulation engine disclosed in Japanese Utility Model Publication No. 59-192647, the liner head 31 including the cylinder head inner wall portion 32 and the cylinder liner upper portion 33 is made of a relatively thick ceramic material. Has been done. Further, in the structure of the heat insulating engine disclosed in Japanese Patent Laid-Open No. 60-90955, the headliner 44 including the upper end wall 51 and the lower end wall is made of a relatively thick ceramic material. Therefore, similarly to the above, the heat capacity of the headliner 31 or 44 facing the combustion chamber side becomes large, and it is not sufficient to reduce the heat capacity of the portion exposed to high temperature, and it is possible to prevent a decrease in suction efficiency. The above problem cannot be solved. Further, the upper end wall 51 of the headliner 44 is attached to the inner end wall 43 of the cylindrical portion 42 of the cylinder head 41 via the gasket 53, and the headliner
The lower end wall of 44 is installed by being pressed against the upper ends of the cylinder block 47 and the cylinder liner 49 via an elastic gasket 54, and an empty portion 45 is formed between the head liner 44 and the cylinder head 41. Since it has a structure, it is not always possible to obtain a heat insulating structure having excellent pressure resistance.

An object of the present invention is to solve the above problems, and to minimize the wall thickness of a ceramic member facing the combustion chamber side of a cylinder head liner in which a cylinder head lower surface portion and a cylinder liner upper portion are integrally structured. With a structure that can be made thin, the heat capacity of the cylinder head liner that faces the combustion chamber and becomes high in temperature is made small, thereby improving the intake efficiency of the engine and reducing the strength deterioration due to the decrease in the thickness of the ceramic material. It is an object of the present invention to provide a structure of an adiabatic engine which is improved and has improved sealability so that the adiabatic material does not come into contact with air, and also has an improved adiabatic function.

[Means for solving problems]

The present invention is configured as follows to achieve the above object. That is, the present invention comprises a ceramic headliner body on the side of the combustion chamber with a ceramic thin plate via a heat insulating material, and the headliner body, the heat insulating material and the thin plate are joined by chemical vapor deposition, that is, CV.
The present invention relates to a structure of a heat insulating engine, characterized in that the heat insulating material is coated and sealed with D, and the heat insulating material is enclosed in a space formed by the headliner body and the thin plate.

Further, the structure of this adiabatic engine, the headliner body and the thin plate is made of silicon nitride, the heat insulating material is made of a material obtained by mixing and firing silicon nitride fiber and alumina fiber or potassium titanate whiskers, the CVD
Is made of a silicon nitride material.

Alternatively, the structure of this adiabatic engine is configured such that the headliner body and the thin plate are made of silicon carbide, and the heat insulating material is made of carbon having a large internal porosity and low thermal conductivity,
The CVD is performed using a silicon carbide material.

Further, in the structure of this adiabatic engine, the headliner body is made of a material having high rigidity, high porosity and low thermal conductivity obtained by forming and firing alumina fiber, and the heat insulating material is provided on the combustion chamber surface of the headliner body. It is composed of coated carbon, and the thin plate is composed of a silicon carbide material coated by CVD.

[Action]

The structure of the heat insulation engine according to the present invention is configured as described above, and operates as follows. That is, the structure of this adiabatic engine is such that the combustion chamber side of the ceramic headliner main body is made of a ceramic thin plate via a heat insulating material, and the joint between the headliner main body and the thin plate is fixed to each other by CVD using a ceramic material. Since the heat insulating material is sealed in, the thickness of the ceramic material facing the lower surface of the cylinder head exposed to high temperature combustion gas and the combustion chamber side of the upper portion of the cylinder liner can be made as thin as possible. The heat capacity can be reduced, the heat insulating material is enclosed to improve the sealing property, and the contact with the air is blocked, so that the carbon heat insulating material does not carbonize.
The heat insulating function can be sufficiently fulfilled, and the heat capacity of the ceramic thin plate facing the combustion chamber can be surely reduced.

Specifically, in order to improve the intake efficiency of the engine, it is important to minimize the heat capacity of the ceramic inner wall that becomes hot in order to minimize the heat received from the combustion chamber inner wall of the adiabatic engine. By reducing, the wall surface of the combustion chamber is immediately cooled during the intake stroke of the engine, and the temperature difference between the intake air temperature and the wall surface temperature is reduced,
This facilitates inflow of intake air. Also, at the maximum temperature in the combustion chamber, the amount of heat absorbed by the wall surface is reduced to reduce the temperature difference between the combustion gas temperature and the wall surface temperature, and the thermal energy that escapes to the outside through the cylinder head, cylinder block, etc. is minimized. .

〔Example〕

Hereinafter, embodiments of the structure of the heat insulation engine according to the present invention will be described in detail with reference to the drawings. In the drawings, the structure of an adiabatic engine which is an embodiment of the present invention discloses only the technical concept of the adiabatic structure of the cylinder head and the cylinder liner in the adiabatic engine, and the cylinder, piston and suction part other than the above are disclosed. Although the heat insulating structure for the exhaust valve is not disclosed and is not shown, the heat insulating engine has a heat insulating structure such as a cylinder head, a cylinder liner, a piston, and an intake / exhaust valve made of a ceramic material such as silicon nitride or a heat insulating material. Needless to say, the purpose of heat insulation can be achieved more reliably by the configuration.

First, referring to FIG. 1, a structure 10 of an adiabatic engine according to an embodiment of the present invention will be described. The structure 10 of this heat insulation engine is a headliner main body 1 in which a cylinder head lower surface portion 2 and a cylinder liner upper portion 3 are integrally formed.
The combustion chamber 5 side is formed of a thin plate 4 made of a ceramic material via a heat insulating material 6. That is, in this heat insulating engine structure 10, a ceramic thin plate 4 is provided on the side of the combustion chamber 5 of the ceramic headliner body 1 with a heat insulating material 6 interposed between the headliner main body 1 and the thin plate 4. 7
Are fixed to each other by CVD (Chemical Vapor Deposition) using a ceramic material, and a heat insulating material 6 is enclosed in an internal space surrounded by the headliner body 1 and the thin plate 4. Headliner body 1
Is made of a ceramic material made of silicon nitride (Si ₃ N ₄ ), and has a valve seat portion 9 for an intake / exhaust valve and a bore gas seal portion 19 protruding in the outer peripheral direction. Insulation material 6
Is disposed inside the headliner main body 1 and is, for example, a mixture of alumina fibers (Al ₂ O ₃ ) and silicon nitride fibers and fired, or a mixture of potassium titanate whiskers and silicon nitride fibers. It is a material having a large porosity and a low thermal conductivity, which is composed of materials and the like. The thin plate 4 facing the combustion chamber side is made of a ceramic material made of silicon nitride. The thin plate 4 is
It is manufactured by molding and firing in advance, but in some cases, it may be formed by coating by CVD of silicon nitride. Further, the headliner body 1 located near the valve seat portion 9 of the intake / exhaust valve on the cylinder head lower surface portion 2 of the headliner body 1, the joint portion 8 of the heat insulating material 6 and the thin plate 4, and the cylinder liner of the headliner body 1. The lower end portion of the upper portion 3, the lower end portion of the heat insulating material 6 and the joint portion 7 of the lower end portion of the thin plate 4 are made of silicon nitride.
It is coated with CVD and sealed,
Moreover, the heat insulating material 6 is configured to be enclosed in the space formed by the headliner body 1 and the thin plate 4. In the case of coating silicon nitride by CVD, the silicon nitride fiber is mixed in the heat insulating material 6, so that the silicon nitride fiber becomes a nucleus of crystallization, and the CVD coating of silicon nitride is easily achieved.

Next, referring to FIG. 2, a structure 20 of an adiabatic engine according to another embodiment of the present invention will be described. The structure 20 of this adiabatic engine is the same as the structure 10 of the adiabatic engine, except that the materials for each member, that is, the headliner body, the heat insulating material and the thin plate, and the materials used for the CVD are different. Therefore, the description of the same points will be omitted. The headliner body 11 is made of silicon carbide (SiC).
Ceramic material consisting of (thermal conductivity: 0.16 cal / m ・ hr ・
C.) and has a valve seat portion 9 for intake and exhaust valves and a bore gas seal portion 19 protruding in the outer peripheral direction. The heat insulating material 16 is arranged inside the headliner main body 11, and is, for example, a material composed of carbon having a large internal porosity and low thermal conductivity, which is an independent porous material (heat conductivity: 0.008 cal / m 2.・ Hr ・ ° C). Further, the thin plate 14 facing the combustion chamber side is made of a ceramic material made of silicon carbide. The thin plate 14 is manufactured by preforming and firing, but in some cases, it may be formed by coating by CVD of silicon carbide. Further, the headliner body 11, the heat insulating material 16, and the thin plate located near the valve seat portion 9 of the intake / exhaust valve on the cylinder head lower surface portion 12 of the headliner body 11.
The joint portion 18 of 14, the lower end portion of the cylinder liner upper portion 13 of the headliner main body 11, the lower end portion of the heat insulating material 16 and the joint portion 17 of the lower end portion of the thin plate 14 are coated with silicon carbide by CVD and sealed. In addition, the heat insulating material 16 is configured to be enclosed in the space formed by the headliner main body 11 and the thin plate 14. When coating silicon carbide by CVD, since silicon carbide is mixed in heat insulating material 16, silicon carbide serves as a crystallization nucleus, and CVD coating of silicon carbide is easily achieved.

Further, referring to FIG. 3, a structure 30 of an adiabatic engine which is still another embodiment of the present invention will be described. The structure 30 of this adiabatic engine is the structure of each adiabatic engine 10 and 2 described above.
Similar to 0, the ceramic headliner main body 21 is integrally configured from the cylinder head lower surface portion 22 and the cylinder liner upper portion 23, and the combustion chamber 5 side of the headliner main body 21 is insulated with the heat insulating material 26.
It consists of a ceramic thin plate 24 through
The outer peripheral surface of is coated with CVD of a ceramic material, and the heat insulating material 26 is enclosed inside the ceramic material.
The headliner main body 21 is made of a material having high rigidity, high porosity and low thermal conductivity. For example, a material obtained by molding and firing alumina fiber (thermal conductivity: 0.0004 cal / m
・ Hr ・ ° C). The heat insulating material 26 is made of a carbon material that coats the outer peripheral portion of the headliner body 21. Further, regarding the thin plate 24, silicon carbide is applied to the outer peripheral portion of the heat insulating material 26 made of a carbon material.
It is coated with CVD.

Therefore, the structure of the adiabatic engine 10, 20, 30 according to the present invention
Is, as described above, for the surface of the high heat insulating material 6,16,26,
By forming a thin plate having high heat resistance such as silicon nitride or silicon carbide or a coating layer, that is, a thin film layer (4, 14, 24) by CVD, a headliner having a low heat capacity and a high heat insulation property can be provided. . That is, the headliner body 1, 1
Ceramic thin plates on the inside of 1,21,4,24
Is exposed to the high temperature combustion gas in the combustion chamber 5 of the engine, but in order to minimize the heat received from the inner wall of the combustion chamber 5, the thickness of the thin plates 4, 14, 24 should be as small as possible. It can be made thin and the heat capacity can be reduced. Furthermore, thin sheets 4,1
In order to prevent the strength from deteriorating due to the thin structure of 4,24, the strength is reinforced by the headliner body 1,11,21 via the heat insulating material 6,16,26 on the outer surface of the thin plates 4,14,24. In addition, the heat insulating materials 6, 16 and 26 improve the heat insulating property, and both ends are coated by CVD to improve the positioning and sealing properties.

〔The invention's effect〕

Since the structure of the heat insulation engine according to the present invention is configured as described above, it has the following effects. That is,
The structure of this adiabatic engine is such that the combustion chamber side of the ceramic headliner body is made of a ceramic thin plate via a heat insulating material, and the joint portion between the headliner body and the thin plate is sealed by CVD using a ceramic material and Since the heat insulating material is enclosed, the thickness of the ceramic material facing the lower surface of the cylinder head exposed to high temperature combustion gas and the combustion chamber side of the upper portion of the cylinder liner can be formed as thin as possible, and the heat capacity can be reduced. It can be made smaller and does not reduce the intake efficiency of the engine.

Further, in the structure of this heat insulation engine, since the heat insulation material is enclosed to improve the sealing property and to block the contact with the air, the carbon heat insulation material is not carbonized.
The heat insulating function can be sufficiently fulfilled, and the heat capacity of the ceramic thin plate facing the combustion chamber can be surely reduced.

Specifically, in order to improve the intake efficiency of the engine, by minimizing the heat received from the inner wall of the combustion chamber of the adiabatic engine, during the intake stroke of the engine, the wall surface of the headliner, that is, the thin plate, is immediately cooled by the intake air, The temperature difference between the intake air temperature and the wall surface temperature is reduced, thereby facilitating the inflow of intake air. Further, at the maximum temperature in the combustion chamber, the amount of heat absorbed by the wall surface is reduced to reduce the temperature difference between the combustion gas temperature and the wall surface temperature, and the thermal energy escaping to the outside through the cylinder head and the cylinder block is minimized. In this way, while improving the intake efficiency of the engine, the heat energy in the combustion chamber can be maximally sent to the energy recovery device provided downstream through the exhaust port, and therefore the heat energy can be maximally recovered. it can.

For example, in an adiabatic engine, by configuring the heat capacity of a portion of the cylinder headliner that is in contact with high-temperature gas to be small, thermal energy is not retained in the sheet during the explosion stroke and exhaust stroke of the engine, In other words, most of the thermal energy can be sent to the energy recovery device provided downstream through the exhaust port without the thermal energy remaining in the combustion chamber. Further, in the intake stroke of the engine, since the portion where the high temperature gas comes into contact, that is, the thin plate, has a small heat capacity, it is immediately cooled to an appropriate temperature and the intake air is not blocked from flowing into the combustion chamber. The phenomenon that the inhalation efficiency is lowered does not occur. That is, by reducing the heat capacity, the wall surface is immediately cooled during the intake stroke, and the temperature difference between the intake air temperature and the wall surface temperature is reduced, which facilitates the inflow of intake air.
Also, at the maximum temperature in the combustion chamber, the amount of heat absorbed by the wall surface is reduced to reduce the temperature difference between the combustion gas temperature and the wall surface temperature, and the thermal energy that escapes to the outside through the cylinder head or cylinder block is minimized. You can

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the structure of the heat insulation engine according to the present invention, FIG. 2 is a sectional view showing another embodiment of the structure of the heat insulation engine according to the present invention, and FIG. 3 is a heat insulation engine according to the present invention. Sectional drawing which shows another Example of the structure of
FIG. 4 is a sectional view showing a conventional adiabatic engine, and FIG. 5 is a sectional view showing a structure of another conventional adiabatic engine. 1,11,21 …… Headliner body, 2,12,22 …… Cylinder head bottom surface, 3,13,23 …… Cylinder liner upper part, 4,14,24
...... Thin plate, 5 …… Combustion chamber, 6,16,26 …… Insulation material, 7,8,17,
18 …… Coupling part, 9 …… Valve seat part, 10,20,30 …… Insulation engine structure.

Claims (4)

(57) [Claims] 1. A ceramic headliner body on the combustion chamber side is formed of a ceramic thin plate with a heat insulating material interposed therebetween, and a ceramic material is coated on the joint portion of the headliner body, the heat insulating material and the thin plate by CVD. A structure of an adiabatic engine characterized by sealing and encapsulating the adiabatic material in a space formed by the headliner body and the thin plate. 2. The headliner body and the thin plate are made of silicon nitride, the heat insulating material is made of a material obtained by mixing and firing silicon nitride fiber and alumina fiber or potassium titanate whiskers, and the CVD is made of a silicon nitride material. The structure of the adiabatic engine according to claim 1, characterized in that 3. The headliner body and the thin plate are made of silicon carbide, the heat insulating material is made of low thermal conductive carbon having a large internal porosity, and the CVD is performed using a silicon carbide material. A structure of an adiabatic engine according to claim 1. 4. The headliner body is made of a material of high rigidity, high porosity and low thermal conductivity obtained by molding and firing alumina fiber, and the heat insulating material is carbon coated on the combustion chamber surface of the headliner body. The structure of the adiabatic engine according to claim 1, wherein the thin plate is made of a silicon carbide material coated by CVD.