JPH068621B2 - Sealed structure of adiabatic engine - Google Patents

Description

TECHNICAL FIELD The present invention relates to a seal structure of a heat insulating engine using ceramics.

[Prior Art] By using ceramics that withstands high temperatures and has an excellent heat insulation effect on the wall of the combustion chamber of the engine, the thermal cycle efficiency is improved and the high temperature exhaust is sent to an exhaust turbine to save energy. An adiabatic engine that recovers heat and improves the overall thermal efficiency is disclosed in, for example, Japanese Patent Laid-Open No. 58-72652, but it has not reached the stage of practical use due to various problems.

In particular, in a structure in which the ceramic headliner and the ceramic cylinder liner do not come into direct contact with each other, and the metal cylinder head and the metal cylinder body are connected with a gasket in between, the combustion gas in the combustion chamber If it leaks from the upper end of the liner, it may blow through the gap between the cylinder portion of the cylinder body and the cylinder liner into the crank chamber. In other words, if there is a slight gap in the fitting part between the cylinder body and the cylinder liner due to the difference in the coefficient of thermal expansion, the combustion gas will flow from the gap between the lower end of the headliner and the upper end of the cylinder liner into the cylinder of the cylinder body. Blows into the crank chamber through the gap between the fitting part and the cylinder liner.

Therefore, as disclosed in Japanese Patent Laid-Open No. 58-30454, a step is formed by expanding the inner diameter at the upper end of the cylindrical portion of the cylinder body, while a flange is formed at the upper end of the cast iron cylinder liner. If it is formed integrally and a seal ring is applied to the step of the cylinder in advance and the cylinder liner is fitted or screwed into the cylinder of the cylinder body from the upper side, there will be no gap at the upper end of the cylinder liner. The gas does not leak to the fitting portion between the cylinder portion of the cylinder body and the cylinder liner and blows into the crank chamber.

However, the cast iron cylinder liner has no problem in the above-mentioned structure, but in the ceramic cylinder liner, providing the flange integrally with the cylinder liner makes the heat distribution of the cylinder liner complicated, and the flange of the cylinder body If the flange is pressed against the stepped portion of the cylindrical portion, the flange may crack due to the pressing force and thermal deformation.

[Problems to be Solved by the Invention] An object of the present invention is to allow a combustion gas to leak from a combustion chamber to a fitting portion between a cylindrical portion of a cylinder body and a cylinder liner with a simple structure without changing the conventional configuration. Another object of the present invention is to provide a seal structure for an adiabatic engine capable of suppressing blow-through to the crank chamber.

[Means for Solving the Problems] In order to achieve the above object, according to the configuration of the present invention, a cylinder liner made of ceramics is formed by enlarging the inner diameter to form a step at the upper end of the cylindrical portion of the metal cylinder body. Is fitted to the cylindrical portion, a metal ring having a coefficient of thermal expansion equivalent to that of ceramics is externally fitted to the upper end of the cylinder liner, and a soft carbon ring is engaged with the conical portion formed on the inner peripheral wall of the lower half of the metal ring. ,
With the elastic metal ring sandwiched between the lower surface of the cylinder head and the upper end surface of the metal ring, the metal ring is pressed against the step portion, the lower end portion of the soft carbon ring is moved to the step portion, and the inner peripheral wall of the soft carbon ring is attached to the cylinder liner. It is closely attached to the outer peripheral wall of.

[Operation] A metal ring made of a metal having substantially the same coefficient of thermal expansion as that of the cylinder liner is externally fitted to the upper end of the cylinder liner, and the metal ring is fitted and inserted into the stepped part of the upper end of the cylindrical portion of the cylinder body. The end face is pressed against the step of the cylindrical portion. The soft carbon ring is engaged with the conical portion formed on the inner peripheral surface of the metal ring. Since the soft carbon ring is elastically brought into close contact with the outer peripheral wall of the cylinder liner and the stepped portion of the cylinder portion of the cylinder body, even if the combustion gas in the combustion chamber leaks into the gap between the head liner and the cylinder liner, The soft carbon ring that is in close contact with the outer peripheral wall of the liner and the step portion prevents the soft carbon ring from blowing through the gap between the cylinder liner and the cylinder portion of the cylinder body into the crank chamber.

[Embodiment of the Invention] As shown in FIG. 2, an ordinary metal cylinder head 1 is used.
A cylindrical portion 37 is formed on the lower surface of the head, and an inverted cup-shaped ceramic hedliner 15 is formed inside the cylindrical portion 37.
Cylinder head 1 fitted through a pair of rings 6
A ring 23 between the lower surface 1a of the
A fuel injection nozzle 5 and a ring 22 surrounding the intake / exhaust ports (not shown) are interposed. The combustion chamber is partitioned by a ceramics liner 15 and a ceramics piston crown 3, and the headliner 15 is abutted against the ceramics cylinder liner 10 at a portion apart from the main part of the combustion chamber.

In reality, in order to avoid stress due to the difference in thermal expansion between the head liner 15 and the cylinder liner 10, a very small gap is provided between the two, and the metal cylinder head 1
A gasket 8 is interposed between the lower end surface of the cylinder and the upper end surface of the metal cylinder body 9, and a head bolt (not shown) is screwed from the cylinder head 1 to the cylinder body 9 for fastening. The cylinder liner 10 has a cylindrical portion 20 of the cylinder body 9.
Is fitted to.

In the piston 13, the ceramic crown portion 3 made of ceramics is superposed on the ordinary skirt portion 7 made of metal, and the nut 16 is fastened and coupled to the bolt 18 inserted from above through the disc spring 17. The piston crown portion 3 is provided with a recess 2 for promoting mixing of fuel and air on the upper surface, a cylindrical portion 34 at the center of the lower surface, and a step portion at the outer peripheral portion of the lower surface. A piston ring 39 is mounted on the outer peripheral surface of the skirt portion 7, while the protrusion 4 provided on the outer peripheral surface of the upper surface is fitted to the step portion of the piston crown portion 3 described above. Further, the skirt portion 7 has a pillar 35 formed in the center of the upper surface, and the piston crown portion 3 is superposed on the pillar 35 via the gasket 19, so that an empty portion 12 is formed between the pillar 35 and the cylindrical portion 34. A seal ring 31 is provided on the overlapping surface of the piston crown portion 3 and the skirt portion 7 on the outer peripheral side.

Thus, an empty portion 21 is defined between the inner peripheral surface of the cylindrical portion 37 of the cylinder head 1 and the headliner 15 by a pair of upper and lower rings 6, and a ring 23 is formed between the lower surface 1a of the cylinder head 1 and the headliner 15. An empty portion 30 is defined by 22. Further, the space 12 is defined by the seal ring 31 between the piston crown portion 3 and the skirt portion 7. These voids 21, 30, 12 act as a heat insulating layer.

In the adiabatic engine described above, most of the combustion period of fuel is performed in the space surrounded by the headliner 15 and the piston crown portion 3, and the abutting portion between the headliner 15 and the cylinder liner 10 is a portion where the combustion gas is somewhat lowered from the maximum temperature. Are placed in the space to reduce the heat load on the gasket 8.

As shown in FIG. 1, according to the present invention, a metal ring 42, such as an alloy called Kovar, having a thermal conductivity equivalent to that of ceramics is externally fitted to the upper end of a cylinder liner 10 made of ceramics. The soft carbon ring 52 having heat resistance is sandwiched between the conical portion 53 formed on the inner peripheral wall of the lower half portion of the metal ring 42 to form the cylindrical portion 20 of the cylinder body 9.
And the large-diameter cylindrical portion 20a formed at the upper end of the cylindrical portion 20 are pressed against the stepped portion 47. The soft carbon ring 52 is elastically brought into close contact with the step portion 47, and is also brought into close contact with the outer peripheral wall of the cylinder liner 10.

A head bolt for connecting the cylinder head 1 to the cylinder body 9 by elastically sandwiching a hollow elastic metal ring 42 such as Inconel having heat resistance between the upper end surface 42a of the metal ring 42 and the lower end surface 15a of the headliner 15. Tighten with.

As described above, in the present invention, since the metal ring 42 is made of a metal whose thermal conductivity is almost the same as that of the ceramics forming the cylinder liner 10, there is no risk of thermal breakage in the fitting portion of both.

The conical portion 53 of the metal ring 42 has a wedge-shaped cross section, is longer in the axial direction than the conical portion 53, and has an inner diameter of the cylinder liner 1.
Sandwiching a soft carbon ring 52 smaller than the outer diameter of 0,
When the lower end surface 42b of the metal ring 42 is pressed against the step portion 47 by the tightening force of the head bolt, the soft carbon ring 52 is brought into close contact with the outer peripheral wall of the headliner 10 and the step portion 47. Therefore, even if a gap is generated in the fitting portion between the cylindrical portion 20 of the cylinder body 9 and the cylinder liner 10 made of ceramics due to thermal expansion, the combustion gas causes the lower end surface 15a of the headliner 15 and the upper end surface 10a of the cylinder liner 10. It is possible to prevent the flow from the gap 57 between the cylindrical portion 20 and the cylinder liner 10 into the gap between the fitting portions.

Further, due to the partial contact failure of the elastic metal ring 42, the combustion gas is forced from the gap 57 to the large-diameter cylindrical portion 20a and the metal ring 42.
Even if the soft carbon ring 52 goes into the gap with the outer peripheral wall of the above, since the soft carbon ring 52 is in close contact with the step portion 47, the blow-off of the combustion gas from this portion can be prevented. The lower end surface of the cylinder head 1 and the upper end surface of the cylinder body 9 are sealed by a gasket 8 shown in FIG.

FIG. 3 shows a front sectional view of another type of adiabatic engine.
In this embodiment, a lower surface 1a of a cylinder head 1A made of ceramics is superposed on the upper end surface of the cylinder body 9 via a gasket 8 and is joined by a head bolt (not shown). The other structure is the same as that shown in FIG. 2, and the same components are designated by the common reference numerals and the description thereof will be omitted.

Also in this embodiment, the cylinder liner 10 made of ceramics is used.
A seal structure 40 is provided on the outer peripheral wall of the upper end portion of the cylinder, and the seal structure 40 can prevent the combustion gas from passing through the gap between the cylinder portion 20 of the cylinder body 9 and the cylinder liner 10.

EFFECTS OF THE INVENTION As described above, the present invention forms a step by enlarging the inner diameter at the upper end of the cylindrical portion of the metal cylinder body, and fits the ceramic cylinder liner to the cylindrical portion, A metal ring with a coefficient of thermal expansion equal to that of ceramics is fitted on the upper end of the liner, and a soft carbon ring is engaged with the conical part formed on the inner peripheral wall of the lower half of the metal ring. With the elastic metal ring sandwiched between the end faces, the metal ring was pressed against the step, and the lower end of the soft carbon ring was brought into close contact with the step, and the inner peripheral wall of the soft carbon ring was brought into close contact with the outer peripheral wall of the cylinder liner. It produces the effect like.

A metal ring is externally fitted to the upper end of the ceramic cylinder liner, a soft carbon ring is attached to the conical part of the lower half of the inner wall of the metal ring, and the metal ring is pressed against the stepped part of the cylinder body by the tightening force of the head bolt. Therefore, the lower end surface of the soft carbon ring elastically comes into close contact with the step portion, and at the same time, the inner peripheral wall of the soft carbon ring comes into elastic close contact with the outer peripheral wall of the ceramic cylinder liner.

Even if the combustion gas leaks through the gap between the headliner and the cylinder liner, the gap between the cylinder liner and the metal ring is sealed by the inner wall of the soft carbon ring, and the gap between the metal ring and the step is sealed by the lower end wall of the soft carbon ring. Therefore, the combustion gas does not blow into the crank chamber through the gap between the cylinder liner and the cylinder body.

The cylinder liner has no flange and has a simple shape. Since it does not receive the tightening force of the head bolt or the complicated thermal deformation force, it does not suffer damage such as cracking.

The structure of each part is simple, the conventional main parts can be formed without any modification, mass production is easy, and assembly is also easy.

[Brief description of drawings]

FIG. 1 is a front sectional view showing a main part of a sealing structure of a heat insulating engine according to the present invention, FIG. 2 is a front sectional view of a heat insulating engine to which the present invention is applied, and FIG. 3 is another heat insulating engine of the same type. FIG. 1: Cylinder head 9: Cylinder body 10: Cylinder liner 13: Piston 15: Headliner 2
0: Cylindrical part 40: Seal structure 42: Metal ring 4
7: Step portion 52: Soft carbon ring 53: Conical portion

Claims (1)

[Claims] Claim: What is claimed is: 1. A cylinder body made of metal has a stepped portion formed by enlarging an inner diameter at an upper end portion of the cylinder body. A ceramic cylinder liner is fitted to the cylinder portion, and a coefficient of thermal expansion is provided at an upper end portion of the cylinder liner. Is fitted with a metal ring equivalent to the ceramics, the soft carbon ring is engaged with the conical portion formed on the inner peripheral wall of the lower half of the metal ring, and the elastic metal sandwiched between the lower surface of the cylinder head and the upper end surface of the metal ring. By the ring, the metal ring is pressed against the step, the lower end of the soft carbon ring to the step, the inner peripheral wall of the soft carbon ring is in close contact with the outer peripheral wall of the cylinder liner,
Seal structure for adiabatic engine.