JPH0442526B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a ceramic pre-chamber for an internal combustion engine, and in particular to an improvement of a ceramic pre-chamber in which a plurality of ceramic bodies are assembled in an internal combustion engine such as an automobile. It is.

(Prior Art) Many attempts have been made to use ceramics in the pre-chambers of internal combustion engines, such as the swirl chambers of diesel engines. For example, in a swirl chamber type diesel engine, the swirl chamber mouth body that forms the nozzle part is made of various ceramics such as silicon carbide and silicon nitride. Attempts have been made to improve the durability of the chamber mouth body. In addition, in recent years, with the aim of improving fuel efficiency, thermal efficiency, etc., attempts have been made to construct the entire swirl chamber with ceramics, and to utilize the heat resistance and insulation properties of ceramics to increase the temperature of the combustion gas inside the swirl chamber. has been done.

By the way, in a case where the sub-chamber is entirely made of ceramics, such as the above-mentioned vortex chamber, for manufacturing reasons, the sub-chamber is generally constructed as an assembly of a plurality of ceramic bodies. Usually, a structure is adopted in which a plurality of horizontally split ceramic bodies are stacked to form a hook assembly.

In addition, in the case of subchambers made of such horizontally split ceramic bodies, a metal ring is usually fitted onto the outer peripheral surface of the assembly formed by assembling the ceramic bodies by shrink fitting, press fitting, etc. The assembled state of the assembly is maintained based on the tightening force of the metal ring by shrink fitting or press fitting, and the assembly is inserted into the receiving hole formed in the cylinder head of the internal combustion engine through the metal ring. It is now being installed. Note that it is also possible to mount the assembly of multiple ceramic bodies as is into the accommodation hole of the cylinder head and have the assembled state directly maintained based on the tightening force of the cylinder head, but such In this case, when the assembly is installed in the receiving hole of the cylinder head, there is a possibility that defects such as chips may occur in the ceramic body constituting the assembly.

Furthermore, in such an auxiliary chamber, in order to improve the heat insulation effect of the auxiliary chamber, it is desirable to form a void as an air existing space around the auxiliary chamber. It has been proposed to form a cavity with a predetermined gap between the receiving hole of the cylinder head and the metal ring. In this way, the heat insulating effect of the pre-chamber can be further enhanced, so the combustion temperature of the combustion gas can be further increased, and fuel efficiency, thermal efficiency, etc. can be further improved.

(Problem) However, such an assembly consisting of a plurality of horizontally split ceramic bodies is held in its assembled state by a metal ring, and furthermore, when it is attached to a cylinder head, there is a void on the outer peripheral surface of the metal ring. In the subchamber where the metal ring is formed, the thermal expansion coefficient of the metal ring is usually larger than that of the ceramic body. It is inevitable that the three-dimensional holding force will decrease, and for this reason, when the holding force decreases, it is inevitable that high temperature and high pressure combustion gas will be ejected from the abutting portions of adjacent ceramic bodies. When combustion gas spewed out in this way, the metal ring swelled and deformed toward the cavity, causing the problem that it was eventually destroyed.

On the other hand, in order to improve the heat insulation effect, a space is formed between the ceramic body and the metal ring, and the sub-chamber is installed with the outer peripheral surface of the metal ring in close contact with the receiving hole of the cylinder head. It is possible that In this way, even if combustion gas blows out from the butt part of the ceramic body,
This prevents the metal ring from bulging outward, thereby avoiding damage to the metal ring due to the outward bulge. However, if a void is simply formed between the ceramic body and the metal ring, combustion gas will eject into the void, and soot from combustion will accumulate within the void, resulting in the formation of a void. There is a problem that the insulation effect is lost.

(Solution Means) Here, the present invention has been made to solve the above-mentioned problems, and its feature is that a plurality of horizontally split ceramic bodies are stacked and a main body is formed inside. A ceramic internal combustion engine in which a cylindrical metal ring is fitted onto the outer peripheral surface of a hollow assembly forming a space communicating with a combustion chamber, and the metal ring maintains the assembled state of the assembly. In the auxiliary chamber, circumferential circumferential portions are located at both ends of the fitting portion of each ceramic body to the metal ring in the assembly stacking direction, and protrude from either one of the ceramic body and the metal ring toward the other. By providing flange portions and fitting the ceramic body and the metal ring through the flange portions, both ends are closed by the flange portions between the ceramic body and the metal ring. This is because a cavity having a predetermined gap is formed.

(Functions and Effects) In such a ceramic sub-chamber, a cavity is formed between the ceramic body and the metal ring to improve the heat insulation effect, so the metal ring is tightly fitted into the receiving hole of the cylinder head. It becomes possible to install it. Therefore, even if the temperature of the pre-chamber increases when the internal combustion engine is operating, the holding force of the assembly by the metal ring decreases, and high-temperature, high-pressure combustion gas is ejected from the butt part of the ceramic body, the combustion will be prevented. It is possible to prevent the metal ring from expanding outward due to the ejection of gas, and it is possible to prevent the metal ring from being damaged by the outward expansion. Furthermore, since it is possible to improve the heat dissipation of the metal ring and to suppress its temperature rise, it is also possible to prevent the metal ring from being damaged.

Moreover, in the present invention, circumferential flanges are located at both ends in the assembly stacking direction of the fitting portion of each ceramic body to the metal ring, and protrude from either one of the ceramic body and the metal ring toward the other. The ceramic body and the metal ring are fitted through the flanges, and the space for obtaining a heat insulating effect is closed at both ends by the flanges. Because of this, combustion gas ejected from the abutting parts of the ceramic bodies does not enter into these spaces, and therefore, the soot generated during combustion accumulates in these spaces, resulting in a heat insulating effect. It is well avoided to reduce the

In other words, according to the present invention, it is possible to obtain a highly reliable pre-chamber for an internal combustion engine that maintains a good heat insulation effect and has significantly improved durability of the metal ring.

(Example) Hereinafter, in order to clarify the present invention more specifically, one example thereof will be described in detail based on the drawings.

FIG. 1 shows an example of a swirl chamber of a diesel engine according to the present invention. There,
2 is a cylinder body of a diesel engine, and a piston 6 is fitted into a cylinder bore 4 formed in the cylinder body 2 so as to be slidable in the vertical direction. A cylinder head 10 is attached above the cylinder body 2 via a gasket 8, and closes the opening of the cylinder bore 4 to form a main combustion chamber 12. A housing hole 14 is formed in the cylinder head 10 with a portion thereof opening into the main combustion chamber 12, and a space 16 forming a swirl-type combustion chamber inside the housing hole 14 is provided. A swirl chamber 18 made of ceramics such as silicon nitride, silicon carbide, zirconia, alumina, glass ceramics, mullite, etc. is accommodated therein.

As is clear from FIG. 1, the vortex chamber 18 has a structure in which the ceramic portion is horizontally divided into two upper and lower ceramic bodies, an upper ceramic body 20 and a lower ceramic body 22. The ceramic bodies 20 and 22 are held together by a cylindrical metal ring 24 fitted to the outer periphery by shrink fitting or the like. The cylinder head 10 is fitted into the housing hole 14 of the cylinder head 10 via the cylindrical metal ring 24 and is mounted thereon.

That is, the upper ceramic body 20 and the lower ceramic body 22 are shown in FIGS. 2 to 5, respectively.
As shown in the figure, the assembly has a cup shape with a cylindrical outer peripheral surface and has a space 16 inside by being stacked one above the other with the openings facing each other. It constitutes 26. A metal ring 24 having a larger coefficient of thermal expansion than the ceramic bodies 20 and 22 is fitted onto the outer peripheral surface of the assembly 26 by shrink fitting or the like, thereby forming the swirl chamber 18.
Such a swirl chamber 18 is formed on the outer peripheral surface of the metal ring 24 in the receiving hole 1 of the cylinder head 10.
This is because it is inserted and attached in close contact with the inner circumferential surface of 4.

The upper ceramic body 20 constituting the swirl chamber 18 has a substantially spherical portion that bulges outward and forms the top of the swirl chamber 18.
As shown in the figure and FIG. 3, two through holes 28 and 30 are formed in the top of the head. When the swirl chamber 18 is installed in the housing hole 14 of the cylinder head 10, the glow plug 32 and injection nozzle 34 are inserted into the through holes 28 and 30, respectively.

Further, as shown in FIGS. 1 and 5, the lower ceramic body 22 has, at its bottom,
A through hole 36 is formed, and when the swirl chamber 18 is installed in the accommodation hole 14 of the cylinder head 10, the space 16 inside the swirl chamber 18 is connected to the main combustion chamber 12.
It is designed to communicate with The combustion gas of the fuel injected from the injection nozzle 34 into the space 16 and combusted within the space 16 is guided into the main combustion chamber 12 through the through hole 36.

In this embodiment, the swirl chamber 1 as described above is used.
8, wide grooves 38 and 40 are formed on the outer peripheral surfaces of the ceramic bodies 20 and 22 constituting the assembly 26, respectively, over the entire circumference, as shown in FIGS. 2 to 5. Between the ceramic bodies 20, 22 and the metal ring 24,
As shown in FIG.
Vacancies (air storage gaps) 42, 44 corresponding to 40
is formed. In other words, the circumferential flange portions 46, 46 are located on the outer periphery of the ceramic bodies 20, 22 at both ends of the assembly 26 in the stacking direction.
48, 50, and 52 are formed, respectively, and the metal ring 24 is shrink-fitted to the outer peripheral surfaces of these flange portions 46 to 48, thereby making the ceramics 20, 22 and the metal ring 24 In between, there is a cylindrical cavity 42 whose both ends are closed by the flanges 46 to 52,
44 is formed.

In such a swirl chamber 18, when the temperature of the swirl chamber 18 rises due to the operation of the diesel engine, both ceramic bodies 2
0, 22 and the metal ring 24 are each expanded according to their respective thermal expansion coefficients, the holding force of the assembly 26 based on the tightening force of the metal ring 24 is reduced. Therefore, the ceramic bodies 20, 22
High-temperature, high-pressure combustion gas leaks from the abutting portion of the cylinder head and is blown against the metal ring 24, but the outer peripheral surface of the metal ring 24 is in close contact with the inner peripheral surface of the receiving hole 14 of the cylinder head 10. Since the metal ring 24 is mounted in this state, even if it is directly exposed to combustion gas, it will not swell outward, and the metal ring 24 itself will maintain its heat dissipation properties in a good condition to prevent a rise in temperature. Since the metal ring 24 is suppressed, it is not easily damaged unlike the conventional ring 24 in which a void is formed on the outer periphery of the metal ring 24.

Also, void spaces 42 and 44 for obtaining a heat insulation effect.
Since both ends are closed with flange parts 46, 48 and 50, 52, respectively, combustion gas leaking from the abutting parts of ceramic bodies 20, 22 will not enter into these spaces 42, 44. Therefore, soot generated due to combustion does not accumulate in the spaces 42, 44 and reduce the heat insulation effect.

Although one embodiment of the present invention has been described above, this is a literal illustration, and the present invention should not be interpreted as being limited to this specific example.

For example, in the embodiment described above, the flange portions 46 to 52 that close both ends of the cavities 42 and 44 were formed on the ceramics 20 and 22 side.
It is also possible to form part or all of these flange parts 46 to 52 on the metal ring 24 side.

Furthermore, in the embodiment described above, the present invention is applied to the vortex chamber 18 in which the assembly 26 is formed by stacking two ceramic bodies, the upper ceramic body 20 and the lower ceramic body 22. The present invention can also be applied to a swirl chamber having a structure in which an assembly is formed by stacking three or more ceramic bodies.

In addition, in the above explanation, an example was described in which the swirl chamber, which is one of the sub-combustion chambers in a diesel engine, was composed of a plurality of ceramic bodies, but other types of sub-combustion chambers, such as pre-combustion chambers, were described. The same situation applies to combustion chamber type combustion chambers, air chamber type combustion chambers, etc., and it goes without saying that the present invention can also be applied to such types of auxiliary combustion chambers.

Further, although the present invention is suitably applied to a sub-combustion chamber structure of a diesel engine, it is not limited thereto; It is also possible to suitably apply the present invention to a case where the sub-chamber is constituted by a plurality of ceramic bodies having a horizontally divided shape.

Although not listed in detail, it goes without saying that the present invention can be implemented with various modifications and improvements within the scope of the spirit thereof.

[Brief explanation of drawings]

FIG. 1 is an explanatory cross-sectional view showing a state in which a swirl chamber of a diesel engine according to an embodiment of the present invention is attached to a cylinder head of the engine. Second
3 are a front view and a bottom view, respectively, of the upper ceramic body of the swirl chamber shown in FIG. 1, and FIGS. 4 and 5 are a front view and a plan view of the lower ceramic body, respectively. . 2: Cylinder body, 6: Piston, 10: Cylinder head, 12: Main combustion chamber, 14: Accommodation hole,
16: space, 18: swirl chamber, 20: upper ceramic body, 22: lower ceramic body, 24: metal ring, 26: assembly, 28, 30, 36: through hole, 42, 44: void (air storage gap ), 46,
48, 50, 52: Flange portion.

Claims (1)

[Scope of Claims] 1. A cylindrical metal ring is fitted onto the outer peripheral surface of a hollow assembly in which a plurality of horizontally split ceramic bodies are stacked to form a space communicating with a main combustion chamber, In a ceramic pre-chamber of an internal combustion engine in which the assembled state of the assembly is maintained by the metal ring, a fitting portion of each of the ceramic bodies to the metal ring is located at both ends in the stacking direction of the assembly. By providing a circumferential flange portion projecting from one of the ceramic body and the metal ring toward the other, and fitting the ceramic body and the metal ring through the flange portions, A pre-chamber made of ceramics for an internal combustion engine, characterized in that a cavity having a predetermined gap is formed between each ceramic body and a metal ring, both ends of which are closed by the flanges thereof.