JPH032678Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an auxiliary combustion chamber of an internal combustion engine.

(Prior Art) In an internal combustion engine having a sub-combustion chamber of a diesel engine, in order to improve the heat insulation and heat retention of the sub-combustion chamber to improve low-temperature startability or reduce exhaust emissions, the sub-combustion chamber is Ceramics have been researched and various ideas and trials have been carried out. For example, a structure is known in which the auxiliary combustion chamber is formed of ceramics separately from the metal cylinder head, and is fitted into a recessed receiving hole formed on the cylinder head side. However, ceramics are prone to breakage due to thermal shock during heating or cooling, rapid pressure changes due to combustion, etc., so to prevent this, ceramic sintered bodies are cast with a casting alloy, etc., and are initially compressed. A stress-applied structure has been proposed by the present applicant (Utility Model Publication No. 14890/1989).
(Japanese Patent Publication No. 60-212614).

Fig. 5 shows an example of the auxiliary combustion chamber according to Utility Model Publication No. 60-14890. In the figure, the chamber part 51 is a bell-shaped ceramic hollow body made of mica ceramics whose main component is mica with low thermal conductivity. Nozzle insertion hole 52 and glow plug insertion hole 53
are provided, and the multiple cylinders are cast at once with the casting alloy constituting the cylinder head 54 by a known method, and after casting, the inner surface of the ceramic hollow body 51 is cut with a milling machine or the like to make the pitch between the cylinders a predetermined size. A mouthpiece 56 having a nozzle hole 55 that communicates the chamber part and the main combustion chamber with each other is fitted onto the open end side of the chamber part 51.

Fig. 6 is an example of a sub-combustion chamber according to Japanese Patent Application Laid-Open No. 60-212614. At the same time, a cylindrical protrusion 67-1 is formed in the cast metal, and a cap 66 made of a silicon nitride sintered body having a nozzle 65 is inserted into the cylindrical protrusion 67-1 of the cast metal. A structure formed by shrink-fitting and joining the inner cavity is fitted into the recessed portion of the cylinder head 64.

Note that 62 is a glow plug insertion hole, and 63 is a fuel injection nozzle insertion hole.

(Problem to be solved by the invention) When the sub-combustion chamber of an internal combustion engine is constructed of ceramics, the chamber part is constructed of ceramics with particularly low thermal conductivity, that is, excellent heat insulation, in order to improve thermal efficiency. Among these, it is desirable that the cap part, which is exposed to high temperatures, be made of ceramics that have particularly high heat and corrosion resistance, and therefore silicon nitride, which has particularly excellent heat and corrosion resistance among ceramics, is often used for the cap.

However, silicon nitride has a high thermal conductivity comparable to that of metals, so there is a problem that heat from the mouthpiece is absorbed by the metal cylinder head in contact with the mouthpiece, which slows down the rate of temperature rise in the sub-combustion chamber and adversely affects startability. be.

(Means for Solving the Problems) The present invention was made to solve the problems mentioned above, and it uses heat insulating ceramics between the base made of ceramics with high thermal conductivity and the metal cylinder head. Therefore, it is intended to provide heat shielding, and specifically, when forming the chamber part made of low thermal conductivity ceramics, a cylindrical protrusion is provided on the open end side of the chamber part, and it is cast and machined at the same time as the chamber part. Thereafter, a mouthpiece is fitted into the inner cavity of the cylindrical protrusion, thereby forming an auxiliary combustion chamber having a structure that provides heat shielding between the mouthpiece and the cylinder head. The chamber part and the cylindrical protrusion made of ceramics may be directly cast into the cylinder head, or they may be cast in advance with metal and the structure made of the composite of ceramics and metal is placed in the cylinder head. The structure may be such that it fits into the recess of the head.

(Function) In the sub-combustion chamber of the present invention, only the chamber part and the cylindrical protrusion made of low thermal conductivity ceramics are cast, so the compressive stress during casting is ideal, and the mouth part which is the highest temperature is It is made of ceramic with excellent heat resistance, and a cylindrical ceramic with low thermal conductivity is interposed between the mouthpiece and the cylinder head, so the heat from the mouthpiece is not transferred to the cylinder head, and the temperature rise rate of the sub-combustion chamber is high. becomes. In addition, since the chamber part is finished in post-processing, there is no need to worry about inner diameter tolerances or deformation during casting, and the cap is manufactured separately, so the shape can be freely selected.

(Example) Example Figure 1 shows an example of the auxiliary combustion chamber according to the present invention.
In the figure, reference numeral 11 denotes a substantially hemispherical hollow part 11-1 with a thickness of about 4 mm made of aluminum titanate by slip casting.
A fired body having the same cylindrical protruding part 11-2 and a stepped part 11-3 is cast into a cylinder head 14 made of aluminum, that is, it is a hollow body directly cast by the cylinder head 14. c. In the case of a four-cylinder diesel engine, four cylinders are cast at the same time, so the above-mentioned fired body is positioned before being cast, and after being cast, the inner wall surface of the hollow body 11 is cut with a milling machine, etc., and at the same time, the glow plug is The insertion hole 12 and the fuel injection nozzle insertion hole 13 have been formed.

Reference numeral 16 designates a cap made of silicon nitride and provided with a nozzle port 15 that communicates with the main combustion chamber.
1-3 and the inner cavity of the cylindrical protrusion 11-2 via annular gaskets 17 and 18, respectively, between the tip of the cylindrical protrusion 11-2 and the stepped portion 16-1 of the cap. It is press-fitted.

Embodiment Figure 2 shows an embodiment of the auxiliary combustion chamber according to the present invention.
In the figure, reference numeral 21 is made of cordierite instead of aluminum titanate in the above embodiment, and includes a substantially hemispherical hollow portion 21-1 and a cylindrical protrusion whose tip abuts against the cylinder head end surface 24-1. It is a ceramic sintered body having step portions 21-3 and 21-4, and is a hollow body that is cast and machined in the same manner as in the above embodiment with a cylinder head 24 made of aluminum. It is.
Numeral 26 is a base made of silicon nitride as in the embodiment, and a nozzle 25 is formed therein, and the stepped portions 21-3 and 21
-4 are press-fitted into the inner cavity of the cylindrical projection 21-2 via annular gaskets 27 and 28, respectively. Note that 22 is a glow plug insertion hole, and 23 is a fuel injection nozzle insertion hole.

Embodiment FIG. 3 shows an embodiment of the auxiliary combustion chamber according to the present invention, in which numeral 31 is made of cordierite as in the above embodiment, and is approximately hemispherical with a glow plug insertion hole 32 and a fuel injection nozzle insertion hole 33. The ceramic sintered body is formed by providing a stepped portion 31-3, and a cylindrical protruding portion 31-2 protruding such that its tip abuts against the cylinder head end face 34-1. It is a hollow body that is directly cast and machined by the cylinder head 34, which is also made of aluminum. Reference numeral 36 denotes a cap made of silicon nitride and having a nozzle 35, which is cold-fitted into the stepped portion 31-3 and the cylindrical protrusion 31-2.

Embodiment FIG. 4 shows an embodiment of the auxiliary combustion chamber according to the present invention, where 41 is a substantially hemispherical hollow body 4 made of a PSZ sintered body.
1-1 and the cylindrical protrusion 41-2 form a step 41-3.
A nozzle 46 is a hollow body formed by providing a casting alloy or the like 47, and has a nozzle 45 made of silicon nitride in the inner cavity of the cylindrical protrusion 41-2.
are fitted by press fit or cold fit. The thus formed assembly consisting of a composite of metal and ceramics was fitted into the recessed part of the cylinder head 44 to form a sub-combustion chamber. Since PSZ sintered bodies have such high strength that machining is difficult, the structure described above is suitable when using such ceramics.

Note that 42 is a glow plug insertion hole, and 43 is a fuel injection nozzle insertion hole.

For the samples from Examples ~ above, 4500 rpm×
After 300 hours of operation on April 4th, it was disassembled and examined, and no abnormalities were found in the cap or chamber. In addition, starting at a low temperature of -25°C takes about half the time of the base engine, and the time it takes for the white smoke to disappear has been significantly reduced. Incidentally, if the accuracy of the inner diameter of the cylindrical protrusion is increased during machining of the ceramic inner wall, press-fitting or cold-fitting will be easier when installing the cap, and most of the current mass production lines for cylinder heads will not need to be changed. You can do everything from casting to finishing without any hassle.

(Effects of the invention) The auxiliary combustion chamber according to the invention uses ceramics that are easy to cast and have low thermal conductivity for the chamber part, and ceramics that are particularly heat resistant for the cap, which is the highest temperature. Ceramic, which has the same low thermal conductivity as the chamber part, is interposed between the mouthpiece and the metallic cylinder head, so the transfer of heat from the high-temperature mouthpiece to the cylinder head is blocked, and the rise of the entire sub-combustion chamber is prevented. The engine heats up faster, improving the engine's ability to start at low temperatures, reducing half-misfires and white smoke, reducing noise by shortening ignition delay time, and reducing fuel consumption by improving thermal efficiency. In addition, since the only ceramics to be cast are the chamber part and the cylindrical protrusion, the compressive stress during casting is applied uniformly to the ceramics, improving durability. It is advantageous for mass production since there is no need to worry about tolerances or deformation, and since the cap is manufactured separately, the shape can be freely selected, which has the effect of increasing the degree of freedom without being subject to restrictions on mounting design.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view of an embodiment of the auxiliary combustion chamber according to the present invention, Fig. 2 is a similar embodiment, Fig. 3 is a longitudinal sectional view of an embodiment, Fig. 4 is a longitudinal sectional view of an embodiment. Conventional Example, FIG. 6 is a longitudinal sectional view of the conventional example. 11, 21, 31, 41, 51, 61: Hollow body made of low thermal conductivity ceramics, 11-1, 2
1-1, 31-1, 41-1, 51-1, 61-
1: Chamber part, 11-2, 21-2, 31-
2, 41-2, 51-2, 61-2: Cylindrical protrusion, 14, 24, 34, 44, 54, 64: Cylinder head, 15, 25, 35, 45, 55, 6
5: Nozzle, 16, 26, 36, 46, 56, 6
6: Base.

Claims (1)

[Claims for Utility Model Registration] (1) A chamber portion consisting of a substantially hemispherical hollow body made of ceramics with low thermal conductivity, and a cylindrical protruding portion below the chamber portion are cast with metal, and the inside of the cylindrical protruding portion is A ceramic auxiliary combustion chamber for an internal combustion engine, characterized in that a mouthpiece made of heat-resistant ceramics and having a nozzle that communicates a chamber part and a main combustion chamber with each other is fitted in a cavity. (2) The ceramic sub-combustion chamber for an internal combustion engine according to claim 1, wherein the edge of the cylindrical protrusion and the end face of the cylinder head are on the same plane.