JPH0610414B2 - Sub chamber structure of engine - Google Patents

Description

The present invention relates to an auxiliary chamber structure of an engine, and more particularly to a structure in which the auxiliary chamber is made of a ceramic material.

[Prior art]

It is conventionally known that the engine auxiliary combustion chamber is made of ceramic. Since a ceramic material is excellent in heat resistance, it is suitable as a constituent material of the sub chamber in this respect. On the other hand, a metal material that has a low thermal conductivity and a low thermal expansion coefficient and is brittle, in particular, extremely weak against tensile stress It has different properties. Therefore, various proposals have been made to solve the problems caused by the peculiar properties of these ceramic materials. For example, Japanese Utility Model Application Laid-Open No. 58-175118 discloses a sub-chamber structure in which a ceramic material forming a sub-chamber is housed in a metal sleeve and covered from the outside so that the ceramic material is supported by the metal sleeve. It is disclosed. The metal sleeve is adapted to be housed in a recess formed in the cylinder head, and is fixed to the cylinder head by being pressed against the inner wall of the recess at the upper and lower portions. Further, a groove for forming a heat insulating space is formed in the middle of the outer periphery of the metal sleeve with the inner wall of the recess. The disclosed structure protects the ceramic material by disposing the metal sleeve on the outer circumference of the ceramic material forming the sub-chamber and forms a heat insulating space on the outer circumference of the sleeve, and the metal material is a good conductor of heat. By utilizing this property, there is no sharp temperature gradient between the inner and outer surfaces of the ceramic sub-chamber structure due to the low thermal conductivity of the ceramic material, the thermal stress is relieved, and the cracking of the ceramic occurs. It is intended to prevent

However, the above eliminates the steep temperature gradient,
Although the thermal stress can be relieved, due to the shape of the sub-chamber, a portion with a different thickness is inevitably formed in the ceramic member. There is a problem that cracks occur in the ceramic member, and this problem cannot be solved by the above-mentioned ones and is still a problem.

[Object of the Invention]

The present invention has been made to solve the above problems, and an object of the present invention is to improve the heat insulating effect and to make the thickness of the ceramic member uniform so as to obtain a uniform thermal expansion amount.

[Structure of Invention]

The structure of the present invention for achieving the above object is a sub-chamber formed of a ceramic member that communicates with a main firing chamber through an injection port, wherein a space portion is formed inside the ceramic member, and the space portion is formed. By forming the inner wall portion and the outer wall portion of the ceramic member to have uniform wall thicknesses, respectively, while improving the heat insulating effect, there is no sharp temperature gradient between the inner and outer surfaces of the sub chamber, and The feature is that the amount of thermal expansion is made uniform.

〔The invention's effect〕

Therefore, according to the present invention, since the space portion functions as a heat insulating space by forming the space portion in the ceramic member forming the sub chamber as described above, the heat insulating effect is improved, and the space portion is separated from the sub chamber and the cylinder. Since an intermediate space is formed between the head and the head, a sharp temperature gradient between the inner and outer surfaces of the sub chamber can be reduced. That is, since the sub chamber, the inner wall portion, the space portion, the outer wall portion, and the cylinder head are sequentially positioned, the inner wall portion has a relatively small temperature gradient between the sub chamber and the space portion, and the outer wall portion has the space portion and the cylinder portion. Since a relatively small temperature gradient between the head and each head is shared, it is possible to prevent the ceramic member from cracking due to a sudden temperature gradient.

Further, when the space is formed, the inner wall portion and the outer wall portion of the ceramic member are formed to have a uniform wall thickness, so that a uniform thermal expansion amount can be obtained, and the ceramic member having a different wall thickness can be obtained. Can be prevented from cracking.

〔Example〕

Hereinafter, the present invention will be described based on embodiments. In the figure,
The sub chamber 2 provided in the cylinder head 1 of the diesel engine is formed in the ceramic member 3, and the injection port 6 extends from the center of the bottom of the sub chamber 2 toward the main combustion chamber 5 in the cylinder 4.
Is slanted through.

A sleeve 7 made of a heat-resistant alloy is externally fitted to the bottom side of the ceramic member 3, and the sleeve 7 and the ceramic member 3
The ceramic member 3 is fixed to the cylinder head 1 by press-fitting the upper end portion 3 a of the above into the upper and lower fitting portions of the concave portion 8. Further, a cylindrical heat insulating space 9 is formed on the outer peripheral side of the ceramic member 3, and is sealed by a seal member 10 which also serves to position the sleeve 7 on the cylinder head 1.

In the cylinder head 1 above the sub chamber 2, an injection nozzle 11 for injecting fuel into the sub chamber 2 and a glow plug 1 are provided.
2 is installed.

A space portion 13 is formed inside the ceramic member 3 so as to surround the entire circumference of the sub chamber 2.

Further, the inner wall portion 14 and the outer wall portion 15 of the ceramic member 3 forming the space portion 13 are formed so that the wall thicknesses thereof are substantially uniform over the entire circumference surrounding the sub chamber 2.

The space portion 13 is formed by blow molding which is generally used as a molding method for a reserve tank of a radiator, and the wall thicknesses of the inner wall portion 14 and the outer wall portion 15 control the air pressure and the like in the blow molding. By doing so, it can be formed appropriately.

Reference numeral 16 is a gasket which also serves as a cushioning member for preventing the ceramic member 3 from hitting the cylinder head 1 strongly, and 17 is a positioning member for positioning the ceramic member 3 and the sleeve 7.

Explaining the operation of the present invention based on the above configuration, first,
While the inside of the sub chamber 2 is heated to a high temperature by combustion, the cylinder head 1 is cooled to some extent by cooling water or the like and has a relatively low temperature. The temperature gradient between the chamber 2 side and the cylinder head 1 side becomes large, and the ceramic member 3 is cracked due to the resulting thermal stress and the difference in the thermal stress due to the difference in the thermal expansion amount at the location where the thickness of the ceramic member 3 is different. However, between the sub chamber 2 and the cylinder head 1, the inner wall 1
4 and the outer wall portion 15 form the space portion 13, the inner wall portion 14 as the ceramic member 3 has a relatively small temperature gradient between the sub chamber 2 and the space portion 13, and the outer wall portion 15 is the space portion. Since a relatively small temperature gradient between the heat insulating space 13 and the heat insulating space 9 is shared by each, it is possible to prevent cracking due to a sudden temperature gradient.

Further, cracking due to the difference in wall thickness can be prevented by forming the space portion 13 by making the inner wall portion 14 and the outer wall portion 15 uniform in thickness.

Further, the heat insulating effect can be improved by the space portion 13 and the heat insulating space 9.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a sub chamber structure showing an embodiment of the present invention. 2 ... Sub chamber, 3 ... Ceramic member, 5 ... Main combustion chamber,
6 ... nozzle, 13 ... space part, 14 ... inner wall part, 15 ...
… Outer wall.

Claims (1)

[Claims] 1. A sub chamber structure of an engine, wherein a sub chamber communicating with a main combustion chamber via an injection port is formed of a ceramic member,
While forming a space inside the ceramic member,
A sub-chamber structure for an engine, wherein an inner wall portion and an outer wall portion of a ceramic member forming the space are made uniform in thickness.