JPH0218299Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an internal combustion engine with heat insulation properties.

In recent years, it has been proposed, for example, in Japanese Utility Model Application Laid-Open No. 54-85206, to improve thermal efficiency by using ceramics with excellent heat insulation properties in cylinders. However, in order to further improve thermal efficiency, if almost the entire combustion chamber is made of ceramic material, the difference in thermal expansion coefficient between the exhaust valve and the valve seat, which are made of ordinary materials, will cause the exhaust port to Not only does the airtightness and the opening/closing timing of the exhaust port change,
There is also a risk of damage.

An object of the present invention is to provide an adiabatic engine that can solve the above-mentioned problems by using a valve seat made of ceramics, which has approximately the same coefficient of thermal expansion as the material of ordinary exhaust valves.

Therefore, the structure of the present invention is to form a cylindrical part in the lower half of the cylinder head, fit and support a cup-shaped head liner made of ceramic material in the cylindrical part, and provide a hole in the upper end wall of the head liner to exhaust air. A valve seat made of a ceramic material having approximately the same coefficient of thermal expansion as the valve is inserted into the hole, and an end flange of the valve seat is inserted between the inner end wall of the cylindrical portion of the cylinder head and the upper end wall of the head liner. It is sandwiched between.

To explain the present invention based on an embodiment, as shown in FIG. A head liner 1 consisting of;
A piston 4 fitted into the cylindrical portion of the head liner 1 and having an upper end portion 12 made of ceramics.
It consists of

A cylinder liner 8 is fitted into the cylindrical portion 15 of the cylinder block 7, and the end flange 8a of the cylinder liner 8 is superimposed on the upper end surface of the cylinder block 7. A gasket 9 is disposed around the flange 8a, and the cylinder head 5 and head liner 1 are superimposed on the upper side of the gasket 9, and are connected to the cylinder block 7 by bolts (not shown).

A cylindrical portion 22 is formed in the lower half of the cylinder head 5, and a cup-shaped head liner 1 is supported in the cylindrical portion 22 with a gap formed by a heat insulating material 8. A hole 25 is provided in the upper end wall of the head liner 1, into which a valve seat 16 formed of a ceramic different from that of the head liner 1 is inserted and supported.

The piston 4 consists of a lower half or body 11 preferably made of aluminum and an upper end 12 made of ceramics, which are connected to each other via a damping bond 10. That is, a small diameter portion 4a is formed at the upper end of the piston body 11, and a recess 19 is formed approximately at the center. On the other hand, the upper end portion 12 is provided with a combustion chamber or recess 13 in the center of the upper surface where fuel is concentrated and injected, and a cylindrical portion 12a that fits with the small diameter portion 4a of the piston body 11 with a sufficient clearance on the lower surface. A protrusion 20 is provided at the center of the inner end wall of the cylindrical portion 12a, the protrusion 20 having a thicker tip end.

The buffer binding material 10 is composed of a mesh material such as stainless steel filled with carbon powder, etc., and has a cylindrical portion 12.
The upper end portion 12 and the main body 11 are sandwiched between the upper end portion 12 and the small diameter portion 4a, and are integrally fired and bonded to the upper end portion 12 and the main body 11, which are preformed with ceramics. At the same time, the protrusion 2 of the upper end 12 is inserted into the recess 19 of the piston body 11.
0 is padded.

The dimensions (thickness) of the upper end 12 are as follows:
is always in sliding contact with the head liner 1 and the upper surface of the upper end portion 12 is dimensioned so that it does not descend from the head liner 1 to the cylinder liner 8. Specifically, the length of the cylinder portion of the head liner 1 is preferably such that the upper surface of the piston 4 moves up to about 120 degrees from the top dead center. Normally, when the temperature exceeds 120°, the exhaust port opens and the temperature in the combustion chamber 2 suddenly drops.
There is little point in making the head liner 1 longer than that.

According to the present invention, in order to securely support the valve seat 16 on the head liner 1, a cylindrical recess 21 is formed in the inner end wall of the cylindrical portion 22 of the cylinder head 5 so as to surround the exhaust passage 17. The end flange 16a of the valve seat 16 fits into the recess 21 and overlaps the upper end wall of the head liner 1. A conical surface is formed on the lower end surface of the valve seat 16, and an exhaust valve 6 having a stem 6a supported by the cylinder head 5 is formed on the conical surface.
move toward and away from each other to open and close the exhaust passage 17. Although not shown, the intake valve is also configured in substantially the same manner.

The valve seat 16 is made of ceramic, such as partially stabilized zirconia, which has approximately the same coefficient of thermal expansion as the normally used exhaust valve 6. Therefore, since the coefficient of thermal expansion is different from that of the head liner 1, the valve seat 16 is inserted into the hole 25 of the head liner 1 with a gap 14, and the flange 16a is fitted and fixed in the recess 21 of the cylinder head 5. , and is held between the cylinder head 5 and the upper end wall of the head liner 1.

By configuring the present invention as described above,
Since the combustion chamber 2 including the recess 13 made of ceramic is formed between the cup-shaped head liner 1 and the upper end 12 of the piston 4, the heat insulation of the combustion chamber 2 is improved and heat loss released to the outside is reduced. The combustion heat is effectively converted into kinetic energy of the piston 4.

According to the present invention, the valve seat 16 is made of ceramic having a coefficient of thermal expansion approximately equal to that of the exhaust valve in relation to the material of the exhaust valve 6, and the flange 16a is sandwiched between the cylinder head 5 and the head liner 1. Since the tip part is configured to face the combustion chamber 2 through the hole 25 provided in the head liner 1, the same wear resistance and heat resistance as the head liner 1 can be obtained, and the heat insulation of the combustion chamber is not impaired. In other words, since the valve seat 16 is made of ceramics, the valve seat 16 has wear resistance, and since the gap 16 is provided between the valve seat 16 and the head liner 1, damage caused by thermal expansion can be prevented. .

[Brief explanation of the drawing]

FIG. 1 is a front sectional view of an adiabatic engine according to the present invention. 2: Combustion chamber, 4: Piston, 5: Cylinder head, 6: Exhaust valve, 7: Cylinder block, 8: Gasket, 10: Upper end of piston, 13: Recess, 16: Valve seat, 17: Exhaust passage, 18 : Heat insulating material, 22: Cylindrical part.

Claims (1)

[Scope of utility model registration request] A cylindrical part is formed in the lower half of the cylinder head, a cup-shaped head liner made of ceramic material is fitted and supported in the cylindrical part, and a hole is provided in the upper end wall of the head liner so that the cylinder head has approximately the same coefficient of thermal expansion as the exhaust valve. A valve seat made of a ceramic material having the following properties is inserted into the hole, and an end flange of the valve seat is sandwiched between an inner end wall of the cylindrical portion of the cylinder head and an upper end wall of the head liner. Adiabatic engine.