JPH068273Y2 - Secondary combustion chamber of internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial field of application" The present invention is preferably used for a secondary combustion chamber made of ceramics.

“Prior Art” In recent years, it has been put into practical use to form a secondary combustion chamber of a diesel engine with ceramics for the purpose of improving thermal efficiency, heat resistance, and measures against particulates. In this case, the second
As shown in the figure, the lower part of the sub-combustion chamber (base part) 22 is a nozzle 23
Since it has a large heat load, a heat-resistant ceramic such as Si ₃ N ₄ is used, and the upper part (chamber part) 24 is ZrO ₂ , Al ₂ TiO ₅
It is desirable to use a heat insulating ceramic such as.

[Problems to be Solved by the Invention] However, a flow hole 25 and a fuel injection nozzle hole (hereinafter referred to as “nozzle hole”) 26 are provided in the chamber portion 24 in the vicinity thereof, and the glow hole 25 is different from the glow hole 25. Nozzle hole 2
Since the inner wall surface between 6 and 6 is steep at an acute angle α, ZrO ₂ and Al ₂ TiO ₅ may cause chipping during processing, heat load, and melting loss due to hot spots. Also,
In general, adiabatic ceramics have low thermal conductivity, so they are often used in compression fields such as castings to suppress the generation of thermal stress, but chipping also occurs when the compressive stress concentrates on the sharp corners. It can happen.

The present invention aims to solve such problems.

"Means for Solving Problems" The means is, as shown in FIGS. 1 (A) and 1 (B), the opening end edge 15a of the glow hole 15 and the opening of the nozzle hole 16 in the inner wall of the chamber portion. The plane sandwiched by the edge 16a is a plane 17 perpendicular to the central axis of the auxiliary combustion chamber. As for the shape of the parallel surface 17, the shortest distance between the central axis and the opening edge 15a is p, and the longest distance between the central axis and the opening edge 16a is q.
Where r is concentric with the central axis and the radius r is p ≦ r ≦ q
17a, opening edge 15a and opening edge 1 in the range of
It is desirable to have a crescent shape surrounded by 6a.

"Action" Since the angle β formed by the flat surface 17 and the glow hole 15 is wider than the conventional angle α, stress concentration and melting loss can be avoided, and the wall thickness becomes thicker, which is advantageous in strength.

Although the volume of the combustion chamber is reduced by the above means, since the nozzle hole occupies a large area in practice, the plane 17 is only a small area and the volume change is negligible.

Further, since the plane 17 is perpendicular to the central axis, the inner wall can be easily processed by using a ball end mill with a flat blade edge.

[Example] A dome made of an aluminum titanate sintered body and having an outer diameter of 30 mm and a wall thickness of 5 mm was cast with AC-4B, and T-6 was used.
After the treatment, a flat surface 17 is formed on the dome bottom by machining,
The wall thickness other than the flat surface 17 was set to 3 mm, and the glow hole 15 and the nozzle hole 16 were formed. At this time, the flat surface 17 has a circular shape if the glow hole 15 and the nozzle hole 16 are not formed, and is formed so as to cover the opening edge 15a of the glow hole 15 by 1 mm. Then, a SUH-3 base 12 was press-fitted to manufacture the auxiliary combustion chamber 11 of the 4-cylinder 2000cc diesel engine shown in FIG. The number of manufactured cylinders was 10 for each cylinder.

Using the above engine, a durability test was carried out at a full load of 4500 rpm for 500 hours (n = 10), but no abnormality was found.

For the purpose of comparison, except that the entire inner wall of the dome is spherical, the auxiliary combustion chamber 21 of FIG. 2 was manufactured under the same conditions as the auxiliary combustion chamber 11. There was chipping in the individual. In addition, when the above durability test was conducted on the ones without chipping, 4
Two of the cylinders suffered chipping at point e, and the other two cylinders had melting damage at point e.

"Effect of the idea" It becomes a ceramic auxiliary combustion chamber with excellent reliability and productivity.

[Brief description of drawings]

FIG. 1 (A) is an axial sectional view of a sub-combustion chamber according to an embodiment of the present invention, and FIG. 1 (B) is a sectional view taken along the line AA 'of FIG. 1 (A) as seen from below. FIG. 2 (A) is an axial sectional view of a conventional auxiliary combustion chamber, and FIG. 2 (B) is a view of a section taken along the line AA ′ of FIG. 14, 24 ... Chamber part, 15, 25 ... Glow hole,
16, 26 ... Fuel injection nozzle hole, 17 ... Plane

Claims (1)

[Scope of utility model registration request] 1. In a sub-combustion chamber in which a chamber portion having a glow hole and a fuel injection nozzle hole is formed of ceramic, and the glow hole is inclined toward the central axis side, an inner edge of the chamber portion and an opening edge of the glow hole are formed. An auxiliary combustion chamber for an internal combustion engine, wherein a surface sandwiched by the opening edge of the fuel injection nozzle hole is a plane perpendicular to the central axis of the auxiliary combustion chamber.