JPH0524400B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a heat insulating structure for an internal combustion engine that provides heat shielding between a ceramic heat insulating wall and a metal structure in the engine.

[Prior art] Adiabatic internal combustion engines using ceramics that have been proposed in the past have a monolith type ceramic insulating wall mainly made of silicon nitride, silicon carbide, etc., which is used for combustion in the piston body, cylinder body, cylinder head, etc. Bonded to the inner wall of a metal structure exposed to gas. In order to suppress heat dissipation from the ceramic insulation wall, a heat insulation cavity is provided between the ceramic insulation wall and the metal structure (Japanese Patent Application No. 1983).
-151885), a gasket made of a metal plate is interposed between the ceramic insulation wall and the metal structure to withstand the explosion pressure (Japanese Patent Laid-Open No. 58-25552).
However, with the above-mentioned means, there is a limit to suppressing the amount of heat dissipated from the ceramic insulation wall to the metal structure. Even though the thermal conductivity of the walls of the combustion chamber is reduced to about 1/25th due to the use of ceramic insulation walls, the heat drop between the combustion chamber and the metal structure is three times as large, so the amount of heat transfer is still 7 times as large. It will only decrease by about 1/2.

[Problems to be Solved by the Invention] In view of the above-mentioned problems, an object of the present invention is to suppress heat radiation in an insulated cavity between a ceramic insulating wall and a metal structure in order to insulate a combustion chamber. An object of the present invention is to provide a heat insulating structure for an internal combustion engine that increases thermal efficiency.

[Means for Solving the Problems] In order to achieve the above object, the present invention has a configuration in which a hollow ring made of a heat-resistant metal is filled with a powder having low thermal conductivity to form an insulating gasket, and a metal structure is The insulating gasket is interposed between the body and the ceramic insulating wall, the insulating gasket is connected by a bolt passing through the insulating gasket, and at least the inner wall of the metal structure is provided with a heat reflector made of a stainless steel plate in the cavity surrounded by the insulating gasket. It is made of overlapping boards.

[Function] A heat reflecting plate made of a heat-resistant stainless steel plate provided on the inner wall of the heat-insulating cavity between the ceramic heat-insulating wall and the metal structure is designed to protect the heat-insulating cavity from the ceramic heat-insulating wall exposed to combustion gas. suppresses heat radiation directed toward the metal structure.

[Embodiments of the Invention] FIG. 1 shows a basic thermal insulation structure of an internal combustion engine according to the present invention. A ceramic heat insulating wall 51 exposed to combustion gas is connected to a metal structure 52 by tightening a nut 54 to a bolt 53 passing through the heat insulating gasket 55. The heat insulating gasket 55 connects the ceramic heat insulating wall 51 and the metal structure 52.
A heat insulating space A is defined between the two.

According to the present invention, in order to prevent heat radiation from the ceramic insulation wall 51 toward the metal structure 52 via the insulation cavity A, the insulation cavity A is defined between the ceramic insulation wall 51 and the metal structure 52. It is equipped with a heat reflecting plate on the inner wall. Specifically, a heat-reflecting plate 59a having heat resistance such as stainless steel is superimposed on the inner wall of the metal structure 52. Preferably, a heat reflecting plate 5 is also provided on the inner wall of the ceramic heat insulating wall 51.
Overlap 9.

As shown in FIG. 2, the insulating gasket 55 is made by filling a hollow ring 56 made of a heat-resistant metal plate such as stainless steel with powder 57 of potassium titanate, cordierite, or the like having low thermal conductivity. The bolt insertion hole is a cylindrical body 56a.
are fitted, and both ends of the cylindrical body 56a are bent and connected to both upper and lower surfaces of the hollow ring 56. In particular, it is preferable to densely fill the powder of potassium titanate, so that even when the bolts 53 are tightened, the compressive load can be withstood and the distance between the metal structure 52 and the ceramic heat insulating wall 51 can be maintained.

In the present invention, as described above, the heat reflecting plates 59 and 59a are superimposed on the inner walls of the ceramic heat insulating wall 51 and the metal structure 52 that partition the heat insulating cavity A.
Ceramic insulation wall 5 exposed to high temperature combustion gas
Thermal radiation from 1 is reflected by the heat reflecting plate 59, and the amount of thermal radiation reaching the heat insulating cavity A is reduced. Since the heat reflecting plate 59a is also superimposed on the inner wall of the metal structure 52, the amount of heat radiation reaching the metal structure 52 is further reduced. As a result, the amount of heat transferred from the ceramic heat insulating wall 51 to the metal structure 52 is significantly reduced compared to the case where the heat insulating cavity A is simply provided between the metal structure 52 and the ceramic heat insulating wall 51.

Hollow ring 56 as insulating gasket 55
The hollow ring 56 is in contact with the heat reflecting plates 59, 59a superimposed on the ceramic heat insulating wall 51 and the metal structure 52, and the inside of the hollow ring 56 is filled with potassium titanate powder 57 having extremely low thermal conductivity. The amount of heat transferred from the heat insulating wall 51 to the metal structure 52 via the hollow ring 56 and the potassium titanate powder 57 is significantly reduced.

FIG. 3 is a front sectional view of a specific adiabatic internal combustion engine using ceramics. A cylindrical portion 1a is formed at the lower part of a cylinder head 1 made of ordinary metal, and an inverted cup-shaped head liner 3 made of ceramic is fitted inside the cylindrical portion 1a via a pair of upper and lower positioning rings 9. Cylinder head 1
between the ceiling wall surface 1b and the top surface of the head liner 3,
Rings 10 and 16 are interposed to surround the ring 26, the fuel injection nozzle 5, and the intake/exhaust ports 11, respectively. The intake/exhaust ports 11 are opened and closed by intake/exhaust valves 7 coated with ceramics. The combustion chamber is defined by an inverted cup-shaped head liner 3 made of ceramics and a piston crown 8 made of ceramics. The head liner 3 butts against a cylinder liner 4 made of ceramics at a portion away from the main part of the combustion chamber.

Actually, head liner 3 and cylinder liner 4
In order to avoid stress due to the difference in thermal expansion between the head liner 3 and the cylinder body 2, an extremely small gap is provided between the two, and a gasket 22 similar to the heat insulating gasket 55 connects the lower end surface of the head liner 3 and the upper end surface of the cylinder body 2. A bolt (not shown) is inserted from the cylinder head 1 into the cylinder body 2 and fastened. The cylinder liner 4 is fitted into the cylindrical portion 20 of the cylinder body 2.

The piston 19 has a piston crown part 8 made of ceramics superimposed on a skirt part 6 made of ordinary metal, and a nut 3 attached to a bolt 31 inserted from above.
3 are screwed together. The piston crown portion 8 is provided with a recess 39 on the upper surface to promote mixing of fuel and air, a cylindrical portion 34 at the center of the lower surface, and a stepped portion on the peripheral edge of the lower surface. The skirt portion 6 has a piston ring 41 mounted on its outer circumferential surface, and a protrusion 24 provided on its upper circumferential edge.
The above-mentioned stepped portion of the piston crown portion 8 is fitted into the piston crown portion 8. The piston crown 8 is superimposed on a pillar 35 formed at the center of the upper surface of the skirt part 6 via a gasket 27, and a heat insulating cavity D is formed between the pillar 35 and the cylindrical part 34. A seal ring 28 is interposed between the overlapping surfaces of the piston crown portion 8 and the skirt portion 6 on the outer peripheral side.

As mentioned above, the cylindrical portion 1 of the cylinder head 11
A heat insulating cavity C closed by a pair of upper and lower rings 9 is formed between the inner peripheral surface of the cylinder head 1 and the head liner 3, and a ring 10 is formed between the top wall surface 1b of the cylinder head 1 and the upper surface of the head liner 3. , 16, 26 form a closed adiabatic cavity B. A heat insulating cavity D closed by a ring 28 is formed between the piston crown part 8 and the skirt part 6.

The heat-insulating cavities B and C of the cylinder head 1 and the heat-insulating cavity D of the piston 19 described above are equipped with a heat reflecting plate on the inner wall of the heat-insulating cavity, similar to the heat-insulating cavity A shown in FIG. Heat radiation from the chamber to the cylinder head 1 via the head liner 3 is suppressed, and heat radiation from the piston crown part 8 to the skirt part 6 is suppressed.

In the case of the heat insulating space B, two stainless steel plates (upper and lower) with mounting holes for the combustion injection nozzle 5 and holes for the intake/exhaust ports 11 are attached to the top wall surface 1 of the cylinder head 1.
b and the upper surface of the head liner 3, respectively, and gaskets 10, 16, and 26 are sandwiched between them to form a heat reflecting plate. Around each of the mounting holes of the combustion injection nozzle 5 and the holes of the intake/exhaust port 11, an insulating gasket 55 as shown in FIG. 2 or a hollow ring with a circular cross section made of a heat-resistant metal such as Inconel is installed and the head bolts Supports the tightening load of

In the case of the heat insulating space C, a positioning ring 9 is installed as a heat reflecting plate between the upper and lower ends of two inner and outer cylindrical bodies made of stainless steel plates.

In the case of the heat insulating cavity D of the piston 19, a heat reflecting plate made of a stainless steel plate is attached to the inner wall of the heat insulating cavity D, or chrome plating is applied.

[Effects of the Invention] As described above, the present invention includes filling a hollow ring made of a heat-resistant metal with a powder having low thermal conductivity to form a heat insulating gasket, and forming the heat insulating gasket between the metal structure and the ceramic heat insulating wall. Interpose an insulating gasket and connect with bolts that pass through the insulating gasket,
Since a heat reflecting plate made of a stainless steel plate is superimposed on at least the inner wall of a metal structure in a cavity surrounded by a heat insulating gasket, the following effects can be obtained.

By inserting a ceramic head liner with excellent heat resistance inside the metal cylinder head with an insulating cavity, the temperature of the combustion gas in the combustion chamber can be maintained at a high temperature.

By providing a heat insulating cavity outside the head liner, the amount of heat transferred from the head liner to the cylinder head can be suppressed and the cylinder head can be protected from high temperatures.

By superimposing a heat reflecting plate on the outside of the heat-insulating cavity, that is, on the inner surface of the cylindrical part of the cylinder head,
It is possible to suppress the amount of heat transfer due to radiation from the heat liner to the outside through the heat insulating cavity.

The insulating gasket for forming an insulating cavity between the head liner and the cylinder head is a hollow ring made of heat-resistant metal such as stainless steel, filled with powder with low thermal conductivity, which connects the cylinder head and the head liner. It has sufficient strength to withstand the tightening load of the tightening bolt, and can suppress the amount of heat transferred from the head liner to the cylinder head via the insulating gasket.

Placing a heat reflector in the space between the metal structure and the ceramic insulation wall can be easily implemented without any design changes to conventional insulated internal combustion engines, and can reduce heat dissipation from the combustion chamber. This can improve the thermal efficiency of internal combustion engines.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing the basic structure of a heat insulation structure for an internal combustion engine, and Figure 2 is an example of a heat insulation gasket for forming a heat insulation cavity between a metal structure and a ceramic heat insulation wall in the heat insulation structure. FIG. 3 is a front sectional view of an adiabatic internal combustion engine to which the heat insulating structure according to the present invention is applied. 51: Ceramic heat insulating wall, 52: Metal structure, 5: Heat insulating gasket, 59, 59a: Heat reflecting plate.

Claims (1)

[Claims] 1 Filling the inside of a hollow ring made of heat-resistant metal with powder of low thermal conductivity to form an insulating gasket, interposing the insulating gasket between the metal structure and the ceramic insulating wall, and penetrating the insulating gasket. A heat insulating structure for an internal combustion engine, characterized in that a heat reflecting plate made of a stainless steel plate is superimposed on at least the inner wall of a metal structure in a space connected by bolts and surrounded by a heat insulating gasket.