JPH02112613A - Structure for subcombustion chamber - Google Patents

Abstract

PURPOSE:To more improve combustion efficiency, heat resistance, durability, etc., of a subcombustion chamber by forming a wall member, forming the subcombustion chamber, with a heat insulating material while providing a thin film member, consisting of ceramic material, to be arranged in an internal wall surface of this wall member. CONSTITUTION:A subcombustion chamber 2 is connected communicating with a main combustion chamber 1 through a nozzle 3 while built in a cylinder head 10 provided with a cooling jacket 14. Here the subcombustion chamber 2 is formed by two or more wall members 4, 7 respectively molded by a heat insulating material of aluminum titanate or the like. And each wall member 4, 7 arranges in its internal wall surface two or more thin film members 5, 6 consisting of non-oxide system ceramic material or the like. While in order to reinforce the subcombustion chamber 2, a metal-made protecting cylinder 8 is fitted to the one wall member 4 on its peripheral surface. In this way, the subcombustion chamber 2 is more improved in its combustion efficiency, heat resistance and durability or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to the structure of a sub-combustion chamber in an internal combustion engine.

[Conventional technology]

Conventionally, a pre-chamber structure for an internal combustion engine, particularly a pre-chamber structure defined by a pre-chamber ceramic material to improve engine thermal efficiency, heat resistance and durability of the pre-chamber, has been disclosed in, for example, Japanese Patent Laid-Open No. 123714/1983. has been done. The sub-chamber structure of an internal combustion engine disclosed in this publication consists of an upper ceramic body and a lower ceramic body abutted against the upper ceramic body, and has a nozzle hole communicating with the main combustion chamber. A metal annular ring is fitted around the outer periphery of the ceramic body and the lower ceramic body, and an annular recess is provided on the inner peripheral surface of the annular ring corresponding to the abutting surfaces of the upper ceramic body and the lower ceramic body.

Further, a subchamber of an internal combustion engine whose inner peripheral surface is formed of a ceramic material is disclosed in, for example, Japanese Patent Laid-Open No. 60-212614. The subchamber of the internal combustion engine disclosed in the publication is
The chamber part, which is a substantially hemispherical hollow body, and the mouthpiece part, which has a connecting hole with the main chamber, are each made of different ceramic materials. A cylindrical protrusion is simultaneously formed on the surrounding metal, and the ceramic of the base is fired inside this protrusion. Further, the chamber portion is made of heat-insulating ceramics, and the cap portion is made of heat-resistant ceramics. Further, a heat insulating layer is partially provided between the inside of the cylindrical protrusion and the ceramic of the base.

[Problem to be solved by the invention]

In general, in the combustion chamber of an internal combustion engine, the pre-chamber type has a larger loss of cooling water and lower fuel efficiency than the direct injection type. The mixing condition is better than that of the direct injection method. Furthermore, the pre-chamber type reduces NOx compared to the direct injection type.
Also, the generation of HC is small, and the generation of smoke and particulates is also small. By the way, SQOT
) is more likely to occur when the fuel concentration of the air-fuel mixture is high, and more likely to occur when the temperature is low. Regarding the process of producing NO, it is more likely to occur when the fuel mixture is lean and the temperature is high. Furthermore, the process of generating HC is more likely to occur when the fuel concentration of the air-fuel mixture is low, and more likely to occur when the temperature is low.

From the above, in internal combustion engines, the pre-chamber type is more advantageous than the direct injection type in terms of reducing the generation of soot, NOx, and HC, but the pre-chamber type reduces cooling water loss. (In both cases, the problem is how to improve the cooling water loss to the level or even more than that of the direct injection type.

That is, in order to increase the temperature during one mixture combustion period in the sub-combustion chamber and to suppress the amount of smoke generated and the generation of particulate intermediate products, the pre-combustion chamber/l! 7
In the first-flow combustion chamber, it is preferable to have a structure in which heat does not dissipate from the outer periphery of the combustion chamber.In addition, in order to reduce cooling water loss and improve fuel efficiency, it is important to consider how to configure the pre-chamber with an insulating structure. There is a problem in how to ensure the strength of the auxiliary chamber itself when constructed with a heat insulating structure.

By the way, in the pre-chamber structure of an internal combustion engine disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 61-123714, the wall forming the pre-chamber is made entirely of ceramics, and the pre-chamber itself has a sufficient heat insulation effect. There is a problem with obtaining it. Furthermore, the pre-chamber of the internal combustion engine disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 60-212614 is made by casting metal into the ceramic of the chamber, and similarly to the above, there is a problem with the insulation of the pre-chamber. be.

However, in structures such as those described above in which the subchamber is constructed using ceramics as a heat insulator or heat-resistant material, it is extremely difficult to ensure the strength of the wall surface and obtain sufficient heat insulation properties. In order to obtain strength, the wall thickness of the ceramic must be increased, and even if the wall thickness is increased, there is a problem in that a sufficient heat insulation effect cannot be obtained.

The purpose of this invention is to solve the above problems,
The inner surface of the auxiliary combustion chamber exposed to combustion gas is made of silicon nitride, silicon carbide, or sialon [(
'9 of ceramics such as Si, Al) i (0, N)++1! The main body of the wall forming the auxiliary combustion chamber is made of a heat insulating material made of a material with a low thermal conductivity α such as aluminum titanate (AhTiO%). In addition, the mechanical stress and thermal stress applied to the thin-walled member are absorbed by the heat insulating material located on the outer periphery of the thin-walled member, thereby ensuring the strength of the ceramic thin-walled member and reducing the wall thickness of the ceramic material. It is an object of the present invention to provide a structure of a sub-combustion chamber that can prevent deterioration in strength due to this.

(?!, Means for Solving the Problem) In order to achieve the above object, the present invention is configured as follows. That is, the present invention provides a sub-combustion chamber that communicates with the main combustion chamber through a nozzle hole. The sub-combustion chamber wall forming the combustion chamber is made of a heat insulating material such as aluminum titanate, and a thin film member made of a non-oxide ceramic material is arranged on the inner wall surface of the sub-combustion chamber wall. Regarding the structure of the auxiliary combustion chamber.

Further, a metal protection cylinder is fitted onto the outer peripheral surface of the wall of the sub-combustion chamber.

[Function] The structure of the auxiliary combustion chamber according to the present invention is constructed as described above, and functions as follows. That is, the structure of this sub-combustion chamber is such that the sub-combustion chamber wall forming the sub-combustion chamber is made of a heat insulating material such as aluminum titanate, and the inner wall surface of the sub-combustion chamber wall is covered with a thin film made of non-oxide ceramic. Since the members are arranged, there is no fear of damage due to thermal stress generated during combustion, and the insulation effect of the sub-combustion chamber can be enhanced by the heat insulating material, reducing cooling water loss and improving fuel efficiency.

In addition, the wall surface of the sub-combustion chamber, that is, the thickness of the ceramic body, is made thinner to reduce the heat capacity.Since the heat capacity of the sub-combustion chamber itself is small, the temperature can be raised in a short time and the fuel spray and air can be mixed quickly. The air can be blown out from the auxiliary combustion chamber to the main combustion chamber as a heswart.

Furthermore, although aluminum titanate itself has low strength and Young's modulus, it is difficult to break due to external forces, but since aluminum titanate is a porous material and is susceptible to thermal shock, ceramic! ! The thin-walled member can ensure strength against thermal stress related to combustion, and even if the thin-walled member itself expands thermally, it can be absorbed by the insulating material located on the outer peripheral surface, reducing mechanical stress and thermal stress that the thin-walled member receives. , cracks, destruction, etc. do not occur in the thin film member.

In addition, since a metal protection tube is fitted to the outer peripheral surface of the auxiliary combustion chamber wall, the auxiliary combustion chamber wall can be reinforced to ensure strength, and the auxiliary combustion chamber wall can be damaged by mechanical stress and thermal stress. It's not going to get destroyed.

〔Example〕

Hereinafter, embodiments of the structure of the sub-combustion chamber according to the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a schematic cross-sectional view of the structure of a sub-combustion chamber according to an embodiment of the present invention. The structure of this sub-combustion chamber is such that the sub-combustion chamber 2 is communicated with the main combustion chamber l through the nozzle hole 3, and the sub-combustion chamber wall 4.7 forming the sub-combustion chamber 2 is made of a heat insulating material. Thin film members 5 and 6 made of a ceramic material are arranged on the inner wall surfaces of the chamber walls 4 and 7. In this case, a ceramic material such as silicon nitride (SiJ4) can be deposited onto the aluminum titanate material by chemical vapor deposition (CVD) or plasma spray coating. Further, a metal protection tube 8 is fitted onto the outer circumferential surface of the sub-combustion chamber wall 4. The auxiliary combustion chamber 2 is integrated into a cylinder head 10 equipped with a cooling jacket 14. The cylinder head 10 is fixed to the cylinder body 11 with a head gasket 13 interposed therebetween. A piston ring 16 is attached to the cylinder 15 of the cylinder body 11.
The piston 12 fitted with the piston 12 reciprocates. Further, fuel is injected into the sub-combustion chamber 2 from a fuel injection nozzle, and a mounting hole 9.17 for the fuel injection nozzle is formed in the sub-combustion chamber wall 4 and the thin film member 5 on the inner wall surface. ing.

In the structure of the sub-combustion chamber according to the present invention, the sub-combustion chamber walls 4 and 7 constituting the walls of the sub-combustion chamber 2 are made of a heat insulating material made of a material with a low thermal conductivity α such as aluminum titanate (AIzTiOs). It consists of

For aluminum titanate, thermal conductivity α: 0.0035 cal/sec cm
'c, strength: 51g7m+11', thermal shock 8900°C, Young's modulus: 13 GN/m'', linear expansion coefficient F 1.5/106K.

This aluminum titanate is not very strong, but it has extremely high heat insulation properties, thermal shock resistance, and thermal expansion resistance.

Therefore, in order to heat the sub-combustion chamber 2, it is extremely effective to use it as the sub-combustion chamber walls 4, 7 forming the sub-combustion chamber 2. However, if a heat insulating material such as aluminum titanate is used directly on the inner wall surface of the sub-combustion chamber 2, the sub-combustion chamber 2 will receive a large thermal shock due to the interaction of fuel spray and flame, resulting in damage. . Therefore,
In order to avoid this situation, the structure of the auxiliary combustion chamber according to the present invention is such that a thin film member 5.6 made of strong ceramics is disposed on the inner wall surface of the auxiliary combustion chamber 2.

a thin film member 5 disposed on the inner wall surface of the sub-combustion chamber walls 4, 7;
6 is silicon nitride (SisNa), silicon carbide (SiC)
, Sialon f (Si, AI) b (0, N) sl, etc. Thin film of ceramics, for example, thickness 1 mm ii ~ 1.5!
It is composed of 1111 thin film members. These ceramics are highly heat resistant and impact resistant.

For example, for silicon nitride (Si, N,), thermal conductivity α: 0.03 cal/see ca+ 'c, strength: 80 kg/+m'' thermal shock near 00℃, Young's modulus: 300 GN/m'' wire Expansion coefficient: 3.2/10"K.

By the way, a large thermal shock acts on the inner wall surface of the sub-combustion chamber 2 due to the alternating action of fuel spray and flame, but by arranging the thin film member 56 made of ceramics on the inner wall surface of the sub-combustion chamber 2, the thermal shock can be reduced. It is possible to provide the combustion chamber 2 with an inner wall surface having high thermal shock strength. Therefore, the auxiliary combustion chamber walls 4 and 5 constituting the auxiliary combustion chamber 2 are not very strong, but have high thermal insulation properties. Even when constructed with a heat insulating material such as aluminum titanate, it can withstand sufficient strength.
In addition, it is possible to provide a sub-combustion chamber 2 with excellent heat insulation properties.

Regarding the manufacturing process of the structure of this sub-combustion chamber, for example, it can be assembled as follows.

First, a thin film member 5 made of ceramic such as silicon nitride and having an inverted cup shape and provided with a fuel injection nozzle mounting hole 17, and a thin film member 6 made of ceramic such as silicon nitride and having a flat plate shape and provided with nozzle holes 18, for example. The thin film members 5 and 6 constitute the inner wall of the sub-combustion chamber 2 by joining at a joint 19 by appropriate means such as chemical vapor deposition (CVD), coating, or the like. Further, a sub-combustion chamber wall 4 having an inverted cup shape and provided with a fuel injection nozzle mounting hole 9 is formed from aluminum titanate, and an inner wall made of a thin film member 5.6 is fitted into the sub-combustion chamber wall 4. Next, the sub-combustion chamber wall 7 having a flat plate shape and provided with the nozzle holes 3 is made of aluminum titanate.
Fits in. Through this forming process, the entire outer surface of the thin film members 5 and 6 constituting the inner wall surface of the sub-combustion chamber 2 is coated with the sub-combustion chamber wall 4.
, 7 are arranged. The auxiliary combustion chamber 2 is manufactured by firing this assembly. In order to reinforce the sub-combustion chamber 2, a metal protective cylinder 8 is fitted onto the outer circumferential surface of the sub-combustion chamber wall 4 by press-fitting it by shrink fitting or the like. By attaching this auxiliary combustion chamber 2 with the metal protective tube 8 to the cylinder at the throat 1o, the auxiliary combustion chamber 2 communicating with the main combustion chamber 1 can be completed. Note that the nozzle holes 3 and 18 are set in an inclined state so that swirl is promoted in the sub-combustion chamber 2 or the main combustion chamber 1 by the inflow and outflow of fluid. Further, in order to promote mixing of the fuel spray and air in the sub-combustion chamber 2, nozzle holes 3. 18 and the axes of the fuel injection nozzle mounting holes 9, 17 are offset or offset and are arranged opposite to each other.

〔Effect of the invention〕

Since the structure of the sub-combustion chamber according to the present invention is configured as described below, it has the following effects.

That is, the structure of this sub-combustion chamber is such that the sub-combustion chamber wall, which forms the sub-combustion chamber that communicates with the main combustion chamber through the nozzle holes, is made of a heat insulating material such as aluminum titanate, and the inner part of the sub-combustion chamber wall is Since the thin film member made of ceramic material is placed on the wall surface of the sub-combustion chamber, the heat conduction path through the wall surface of the sub-combustion chamber is blocked by the heat insulating material, and no heat is radiated to the outside. It enhances the heat insulation effect, provides an ideal structure for a sub-combustion chamber, reduces cooling water loss, and improves fuel efficiency. In addition, as mentioned above, the heat insulation effect is excellent, and the wall surface of the sub-combustion chamber, that is, the ceramic body, is thinned to reduce the heat capacity, and the empty capacity of the sub-combustion chamber itself is small, so the temperature can be raised in a short time. At the same time, the fuel spray and air can be quickly mixed, and the fuel can be blown out from the auxiliary combustion chamber as a heswart into the main combustion chamber. That is, since the temperature in the sub-combustion chamber can be raised in a short time and the fuel spray and air can be mixed quickly, the temperature within the auxiliary combustion chamber can be increased within the smoke generation temperature zone determined by the fuel equivalence ratio of fuel and air and the combustion temperature. immediately clears the combustion, and the flame is blown out from the auxiliary combustion chamber to the main combustion chamber as a heswar. Then,
As the flame is blown out from the auxiliary combustion chamber to the main combustion chamber, the fuel equivalence ratio and combustion temperature are lowered, so that the NOx generation temperature zone determined by the fuel equivalence ratio and the combustion temperature is combustion can be avoided.

Therefore, combustion can be performed in the sub-combustion chamber and the main combustion chamber while avoiding the generation of smoke, HC, and NO.

Furthermore, in general, a large thermal shock is applied to the sub-combustion chamber due to the interaction between fuel spray and flame. In the structure of this sub-combustion chamber, when subjected to such a thermal shock, aluminum titanate itself has low strength, but the thin ceramic member on the inner peripheral wall has strong strength against the above-mentioned thermal shock, and the sub-combustion chamber itself Since sufficient strength can be secured for the sub-combustion chamber, cracks, destruction, etc. will not occur in the sub-combustion chamber, and even if the thin-walled member itself expands thermally, the thermal insulation material located on the outer peripheral surface will absorb the thermal expansion. can be absorbed, the mechanical stress and thermal stress that the thin-walled member receives can be reduced, and cracks, destruction, etc. do not occur in the thin-film member.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the structure of a sub-combustion chamber according to the present invention. 1-=-King combustion chamber, 2-1-- Sub-combustion chamber, 3.18 injection hole, 4.7-- Sub-combustion chamber wall, 5, 6-- Thin film member, 8-- -Metal protection tube, 9.17-.-Fuel injection nozzle mounting hole, 10-.-Cylinder head, l-cylinder body, l2--Piston.

Claims (2)

[Claims] (1) A sub-combustion chamber wall forming a sub-combustion chamber communicating with the main combustion chamber through a nozzle hole is made of a heat insulating material, and a thin film member made of a ceramic material is arranged on the inner wall surface of the sub-combustion chamber wall. The structure of the auxiliary combustion chamber is characterized by: (2) The structure of the auxiliary combustion chamber according to claim 1, characterized in that a metal protection tube is fitted onto the outer peripheral surface of the auxiliary combustion chamber wall.