JPH0217150Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Field of Application) This invention relates to the structure of the subchamber of an engine, particularly the subchamber whose periphery is formed of ceramic material.

(Prior art) In engines for automobiles, etc., the combustion chamber is composed of a main combustion chamber and an auxiliary chamber that communicates with the main combustion chamber through an injection hole, and fuel is injected into the auxiliary chamber from a fuel injection nozzle. In some cases, a so-called pre-chamber type combustion method is adopted, in which half-burned gas is ignited in the main combustion chamber and diffused into the main combustion chamber for combustion.

In this combustion method, it is important to maintain the interior of the pre-chamber at a high temperature in order to suppress the emission of unburned gas such as hydrocarbons. As if
Attempts have been made to form a ceramic material with excellent heat insulation around the subchamber. Among ceramic materials, there is a desire to use zirconia, which has particularly excellent heat insulation properties.

However, although ceramic materials have excellent heat insulation properties, they are also extremely resistant to external forces such as impact forces, so when the pre-chamber is made of ceramic material, it is necessary to install it in the cylinder head of the engine body. When it is fitted into a recess, it is likely to be damaged by hitting the peripheral wall of the recess, and during operation, the difference in thermal expansion between the cylinder head and the ceramic material interferes with the ceramic material and presses against the inner wall surface of the recess, causing cracks. There were problems such as: In particular, when zirconia is used as the ceramic material, zirconia has a good heat insulating effect but is a material with a large coefficient of thermal expansion, so there is a problem in that cracks are likely to occur.

(Purpose of the invention) The present invention is intended to deal with the above-mentioned problems when the periphery of the sub-chamber is formed of ceramic material, such as damage when assembling the sub-chamber into the fitting recess of the engine body, or The main purpose is to prevent cracks from occurring during driving.

A second object of the present invention is to use a foamed metal gasket having heat insulating properties as a means for achieving the above object, thereby further improving the heat insulation effect of the subchamber.

(Structure of the invention) That is, the sub-chamber structure of an engine according to the present invention includes a sub-chamber structure of an engine in which the sub-chamber that communicates with the main combustion chamber through the nozzle hole is made of ceramic material. A hollow sub-chamber structure is constructed by fitting the ceramic material forming the sub-chamber inside the sub-chamber so that its upper part protrudes from the support member, and the ceramic material in this sub-chamber structure is made of zirconia. At the same time, a through hole through which a fuel jet injected from a fuel injection nozzle is introduced and a through hole through which a glow plug is inserted are provided in the upper part of the ceramic material protruding from the support member, and a through hole through which a glow plug is inserted is provided. The present invention is characterized in that a foamed metal gasket is interposed between the inner wall surface of the fitting recess into which the subchamber structure is fitted and the upper portion of the ceramic material that protrudes from the support member.

According to the above configuration, the foamed metal gasket is connected to the upper part of the ceramic material protruding from the support member of the structure and the fitting part of the engine body when the pre-chamber structure is assembled and the engine is operated. Since it acts as a buffer member between the ceramic material and the inner wall surface, it not only prevents damage to the ceramic material during assembly, but also prevents damage during operation, even when the ceramic material is made of zirconia with particular consideration to heat insulation. Cracks caused by thermal expansion of zirconia are effectively prevented. In addition, since the metal foam gasket retains air within its structure, an air layer is formed between the ceramic material and the inner wall surface of the fitting recess.
This further improves the heat insulating effect on the subchamber, reduces the temperature difference between the inner and outer surfaces of the ceramic material, and reduces the occurrence of thermal stress in the ceramic material. Moreover, since the shape retention property is good, the durability is improved.

Incidentally, the above-mentioned publication shows a configuration in which a gasket is interposed between the ceramic cap and the stepped part of the hole for the sub-chamber, but this gasket is for gas sealing in the sub-chamber, and is not used in the present invention. The purpose of use is different from that of a foamed metal gasket, and it does not improve the heat insulation effect on the subchamber as in the present invention.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

As shown in FIG. 1, an engine 1 has a main combustion chamber 5 formed by a cylinder lock 2, a cylinder head 3, and a piston 4 as a combustion chamber, and a main combustion chamber 5 formed within the cylinder head 3 with nozzle holes 6. It has an auxiliary chamber 7 that communicates with the main combustion chamber 5 through the combustion chamber 5. The auxiliary chamber 7 is provided by fitting and fixing a hollow auxiliary chamber structure 8, which has been assembled and integrated in advance, into a fitting recess 9 provided in the cylinder head 3, as shown in FIG. The structure 8 is composed of a metal annular support member 10 and a ceramic material 11 shrink-fitted inside the support member.
The interior of the chamber is designated as the subchamber 7. The flange 10a provided at the lower end of the support member 10 is press-fitted into the entrance of the recess 9 in the cylinder head 3, thereby being fixed to the cylinder head 3.

In addition, through holes 12 and 13 are provided in the upper part of the ceramic material 11 that protrudes from the support member 10, and a fuel injection nozzle 14 mounted on the cylinder head 3 is provided with through holes 12 and 13.
A fuel jet injected from the engine is introduced into the auxiliary chamber 7 through one of the through holes 12, and a glow plug 15 that preheats the inside of the auxiliary chamber 7 at the time of startup is inserted into the other through hole 13. .

However, the upper surface 11a of the ceramic material 11 of the subchamber structure 8 exposed from the support member 10,
Ceiling surface 9 of fitting recess 9 in cylinder head 3
A gasket 16 is interposed between it and a.
This gasket 16 is made of, for example, nickel or nickel chrome alloy, and has an areal density of 0.1 to 0.3.
The upper surface ^11a of the ceramic material 11 is made of foamed metal foamed to a density of
Holes 16a and 16b are formed to correspond to the through holes 12 and 13 in the ceramic material 11.

In this embodiment, the ceramic material 11 is divided into a lower part 11' in which the injection hole 6 is provided and an upper part 11'' in which the through holes 12 and 13 are provided.
As for the material of both parts 11' and 11'', silicon nitride, which is resistant to thermal shock, is used for the lower part 11', which is exposed alternately to high-temperature combustion gas and low-temperature fresh air, and also has a heat insulating effect between it and the cylinder head 3. Zirconia (partially stabilized zirconia), which has particularly excellent heat insulation properties, is used for the upper part 11'' which requires the following.

According to the above configuration, when the engine 1 is operating, air is forced into the auxiliary chamber 7 from the main combustion chamber 5 through the nozzle holes 6 during the compression stroke, forming a vortex flow, and from the compression stroke to the expansion stroke. Fuel is injected from the fuel injection nozzle 14 into the auxiliary chamber 7 at a predetermined time during the transition. This fuel is immediately ignited in the auxiliary chamber 7, becomes semi-combusted gas, and is injected from the nozzle hole 6 into the main combustion chamber 5, where it is further combusted and pushes down the piston 4. In this case, since the auxiliary chamber 7 is entirely covered with a ceramic material 11 having excellent heat insulation properties, the inside is maintained at a high temperature, and the fuel can be ignited and burned well.

However, since the ceramic material 11 is weak against impact forces, etc., when the sub-chamber structure 8 is fitted into the fitting recess 9 of the cylinder head 3, the upper part exposed from the support member 10 may directly contact the peripheral wall of the recess 9. It will be easily damaged when touched. However, the upper surface 11a of this ceramic material 11 and the ceiling surface 9 of the recess 9
A foamed metal gasket 16 is interposed between the ceramic material and the ceramic material upper surface 11a.
The upper surface 11a of the ceramic material is protected and prevented from coming into direct contact with the cylinder head 3, and the gasket 16 alleviates the impact caused by the contact. This prevents damage to the ceramic material 11 during assembly.

Furthermore, when the engine 1 is operated after the ceramic material 11 or sub-chamber structure 8 is assembled into the fitting recess 9 of the cylinder head 3, since the coefficient of thermal expansion of the cylinder head 3 is large, the ceiling surface of the recess 9 is 9a thermally deforms downward and tries to press the upper surface 11a of the ceramic material 11 downward. However, since the foamed metal gasket 16 interposed between the upper surface 11a and the recess ceiling surface 9a absorbs the pressing force, a large force is prevented from acting on the ceramic upper surface 11a. The occurrence of cracks on the upper part of the ceramic material is prevented.

Furthermore, since the gasket 16 retains air within its structure, the upper surface 11a of the ceramic material
An air layer is formed between the cylinder head 3 and the recess ceiling surface 9a on the cylinder head 3 side. This air layer acts as a heat insulating layer and further improves the heat insulation effect on the inside of the subchamber 7. Furthermore, by forming a heat insulating layer on the outside of the ceramic material 11, the temperature difference between the inner and outer surfaces of the ceramic material 11 becomes smaller, and as a result, internal stress is generated due to the difference in thermal expansion between the inner and outer surfaces of the ceramic material 11. is reduced. This also prevents cracks from occurring in the ceramic material 11.

(Effects of the invention) As described above, according to the invention, in an engine in which a sub-chamber surrounded by a ceramic material is provided in the cylinder head or the like of the engine body, the upper part of the sub-chamber is placed inside the metal annular support member. A hollow sub-chamber structure is formed by fitting a ceramic material so as to protrude from the support member, and the inner wall surface of a fitting recess in the engine body into which the sub-chamber structure is fitted, and the ceramic material are fitted to protrude from the support member. By interposing the foamed metal gasket between the upper part of the ceramic material that protrudes from the support member, the ceramic material and the inner wall surface of the fitting recess are in direct contact with each other during assembly and operation of the ceramic material. Since there is no contact or interference, damage to the ceramic material and generation of cracks are prevented. In particular, in the present invention, since the ceramic material is made of zirconia, which has a low thermal conductivity, an excellent heat retention effect for the subchamber can be obtained. On the other hand, by using a foam metal gasket as the gasket, the thermal expansion of the zirconia is absorbed.
In particular, it not only effectively prevents the occurrence of cracks in the ceramic material during operation, but also has the advantage of improved durability due to its excellent shape retention. Furthermore, the heat insulating effect of the foamed metal gasket further improves the heat retention effect on the subchamber, and also reduces the occurrence of thermal stress in the ceramic material. Furthermore, since there is no risk of damaging the ceramic material during assembly, the work of assembling the ceramic material is facilitated and the workability of the work is improved.

[Brief explanation of the drawing]

1 and 2 show a first embodiment of the present invention, in which FIG. 1 is a longitudinal sectional view of the vicinity of the subchamber in an engine, and FIG. 2 is a perspective view of the subchamber structure and gasket. 1...Engine, 5...Main combustion chamber, 6...Nozzle hole, 7...
Sub-chamber, 8... Sub-chamber structure, 9... Fitting recess, 10... Annular support member, 11... Ceramic material, 11''... Upper part,
12, 13...Through hole, 14...Fuel injection nozzle, 1
5... Glow plug, 16... Foamed metal gasket.

Claims (1)

[Scope of utility model registration request] An engine sub-chamber structure in which a sub-chamber communicating with a main combustion chamber via a nozzle hole is made of ceramic material,
A hollow sub-chamber structure is constructed by fitting a ceramic material forming the sub-chamber inside a metal annular support member such that its upper part protrudes from the support member; The ceramic material is made of zirconia, and an upper part of the ceramic material protruding from the support member is provided with a through hole through which a fuel jet injected from a fuel injection nozzle is introduced and a through hole through which a glow plug is inserted. , and a foamed metal gasket is interposed between the inner wall surface of the fitting recess in the engine body into which the sub-chamber structure is fitted and the upper part of the ceramic material protruding from the support member. Engine pre-chamber structure.