JPS6350420Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a sub-combustion chamber for a diesel engine, which is made up of a plurality of ceramic pieces that are abutted against each other in a metal insert ring.

(Prior Art) In the sub-combustion chamber of a diesel engine, which is formed by abutting and uniting a plurality of ceramic pieces within an insert ring, it goes without saying that each ceramic piece must be accurately positioned relative to the other. In addition, if the insert ring and ceramic piece are not positioned accurately, for example, the fuel injection valve installed on the cylinder head side facing the auxiliary combustion chamber and the nozzle formed on the ceramic piece side may The relative position may shift and the combustion characteristics may deteriorate,
Similarly, the heat generating part of the glow plug installed on the cylinder head side facing the auxiliary combustion chamber and the glow plug insertion hole on the ceramic piece side interfered with each other, and the area around the glow plug insertion hole of the ceramic piece was extremely heated. Since there is a risk of problems such as breakage, when manufacturing the auxiliary combustion chamber, it is necessary to accurately position the ceramics not only between each ceramic but also between each ceramic and the insert ring.

However, this type of conventional sub-combustion chamber made of ceramic (for example, Japanese Patent Application Laid-open No. 10723/1983 = F02B19/08)
In the auxiliary combustion chamber, each ceramic piece was simply shrink-fitted into the insert ring during manufacturing, and no other fixing means were applied.
When the ceramic pieces and the insert ring thermally expand due to combustion heat during engine operation, and the tightening force acting between them decreases, the ceramic pieces and the insert ring should be tightened between each ceramic piece or between each ceramic piece and the insert ring. There has been a problem in that subsequent positional deviations tend to occur between them, and as a result, the combustion characteristics or durability of the engine deteriorate.

(Purpose of the invention) The present invention is designed to prevent misalignment between each ceramic piece and an insert ring in the sub-combustion chamber of a diesel engine, which is formed by combining a plurality of ceramic pieces. It was done for the purpose of

(Structure of the invention) In the present invention, a metal coating layer is formed in advance on the fitting surface of the insert ring on a plurality of ceramic pieces that are brought into contact with each other in the insert ring, and the ceramic pieces are fitted into the insert ring. The inserted ceramic piece is positioned relative to the insert ring by metallurgical joining means such as brazing or welding applied between the insert ring and the metal coating layer. It is.

(Embodiment) FIG. 1 shows a main part of a cylinder head 1 of a swirl chamber type diesel engine Z equipped with an auxiliary combustion chamber according to an embodiment of the present invention. In the figure, numeral 2 is a cylinder block, and 3 is a piston. This cylinder head 1 accommodates an insert block 21 (described later) having a sub-combustion chamber block made of ceramic on the abutting surface 1a against the cylinder block 2 and facing upward from the main combustion chamber 14. The receiving hole 17 is formed in a circular concave shape.

The insert block 21 has a sub-combustion chamber 6 therein.
The ceramic sub-combustion chamber block 9 having the cavity formed therein is fitted into a metallic insert ring 11.

The auxiliary combustion chamber block 9 has a vertically divided structure consisting of a first ceramic piece (hereinafter referred to as the first piece) 7 and a second ceramic piece (hereinafter referred to as the second piece) 8, and a substantially spherical piece is formed between the two. A secondary combustion chamber 6 is formed. The first piece 7, which has a substantially hemispherical concave portion 25 corresponding to the upper part of the sub-combustion chamber 6, is installed near the water jacket 22 in the cylinder head 1, and is particularly required to have heat insulation properties. In this embodiment, the first piece 7 is made of zirconia (ZrO ₂ ), which has excellent heat insulation properties among various ceramic materials. Furthermore, this first piece 7
includes a fuel spray hole 20 and a glow plug insertion hole 19.
is formed.

On the other hand, it has an inclined bottom-shaped concave portion 26 corresponding to the lower part of the sub-combustion chamber 6, and its inclined bottom surface 26a.
The second piece 8 has a nozzle 13 formed on the bottom surface 6a of the auxiliary combustion chamber to allow the auxiliary combustion chamber 6 and the main combustion chamber 14 to communicate with each other. Therefore, in this embodiment, silicon nitride (Si ₃ N 4 ), which has particularly high heat resistance and corrosion resistance among various ceramic materials, is used as the material for the second piece ₈ . are doing.

The first piece 7 and the second piece 8 are integrally connected with each other in the proper position as described later, and are further fitted with a metal insert ring 1 (stainless steel is used in this embodiment).
1 and integrally coupled with the insert ring 11 to form an insert block 21. The manufacturing procedure of this insert block 21 will be explained with reference to FIGS. 2 to 5. In forming the insert block 21 in this embodiment, first, as shown in FIG. Accurately position the two pieces 8 at their regular meeting positions and stack them one above the other,
The outer circumferential surface 7a of the first piece 7 and the second piece 8 form the auxiliary combustion chamber block 9 and serve as the fitting surface for the insert ring 11 as shown in FIG.
A metal coating layer 31 of an appropriate thickness is formed on the outer circumferential surface 8b of the metal coating layer 31 by metallization treatment so as to integrally cover the first piece outer circumferential surface 7a and the second piece outer circumferential surface 8b. First piece 7
and the second piece 8 are integrally joined and fixed while being positioned at the normal position. Furthermore, metallization treatment involves coating the surface of a ceramic material with, for example, molybdenum powder in the form of a paste to form a molybdenum layer, which is then baked at a predetermined temperature (1400°C) to make the surface of the ceramic material heat resistant. It forms a rich metal coating layer (for example, a molybdenum layer) with extremely high bonding strength.

Next, as shown in FIG. 5, the auxiliary combustion chamber block 9, which is integrated with a metal coating layer, is formed of stainless steel into a ring shape of an appropriate diameter, and is placed on its peripheral wall and on the same circumferential surface. The insert ring 11 is shrink-fitted into the insert ring 11 in which an appropriate number of through holes 32, 32, . The inner surfaces of the through holes 32, 32, . 21 (see Figure 2).

At this time, the relative fitting position of the insert ring 11 and the sub-combustion chamber block 9 in the vertical direction is as follows.
The abutting portion between the first piece 7 and the second piece 8 of the auxiliary combustion chamber block 9 is the through hole 3 of the insert ring 11.
2, 32... are appropriately set to polymerize.
In this way, when the abutment part of the auxiliary combustion chamber block 9 and the through holes 32, 32, . Since it spans between the metal coating layer 31 on the piece 8 side, the metal coating layer 31 may be damaged at the abutment part between the first piece 7 and the second piece 8 due to excessive stress or impact, for example, and the metal coating layer 31 may be damaged on the first piece 7 side. Even when the insert ring 11 is separated from the second piece 8, the relative positions between the first piece 7, the second piece 8, and the insert ring 11 can be maintained at their normal positions. In another embodiment of the present invention, as shown in FIG. 6, through holes 32, 32, . . . formed on the insert ring 11 side are provided.
are provided at both the position facing the first piece 7 side and the position facing the second piece 8 side, respectively, so that the insert ring 11 and the auxiliary combustion chamber block 9 are separated on the first piece 7 side and the second piece 8 side. It may also be joined to. In this case as well, the same effects as in the embodiment shown in FIG. 5 can be obtained.

Incidentally, as in each of the above embodiments, the auxiliary combustion chamber block 9
When a metal coating layer 31 of an appropriate thickness is formed between the sub-combustion chamber block 9 and the insert ring 11, the metal coating layer 31 is more elastic than the ceramic piece. It acts as a kind of buffer between
Secondary combustion chamber block 9 made of ceramic with low brittle resistance
This can prevent the auxiliary combustion chamber block 9 from being damaged due to excessive shrink-fitting stress acting on it. Furthermore, in these embodiments, the auxiliary combustion chamber block 9 and the insert ring 11 are integrated with a high melting point brazing material (for example, copper solder = melting point 1083° C.); (or welding material), the auxiliary combustion chamber block 9 and insert ring 1 will be removed during engine operation.
Since there is no fear that the parts 1 and 1 will separate, it is also possible to omit the shrink fitting and make the two loosely fitted.

In addition, the insert ring 11 has the first
In addition to acting as a coupling and fixing member between the piece 7 and the second piece 8, the insert block 2
It also acts as a protective member to prevent the ceramic first piece 7 or the second ceramic piece 8 from accidentally hitting directly against the cylinder head 1 side and being damaged when the cylinder head 1 is fitted into the receiving hole 17. , its shape is not limited to a simple ring shape as in this embodiment; for example, the first piece 7 and the second piece
It is formed into a substantially bowl-shaped body having a cylindrical wall portion that covers the outer peripheral surface of the piece 8 and a ceiling portion that covers the upper outer end surface of the first piece 7 facing the ceiling surface of the receiving hole 17;
As shown in FIG. 8, a cylindrical wall portion 11a that covers the outer peripheral surfaces of the first piece 7 and the second piece 8, and a bottom plate that covers the lower outer end surface 8a of the second piece 8 and has a nozzle 13 formed in its center. It can also be formed into a bottomed cylindrical body having a portion 11b.

The shape and dimensions of the receiving hole 17 formed in the cylinder head 1 are such that when the insert block 21 is fitted into the receiving hole 17, the space between the outer peripheral surface of the insert block 21 and the inner surface of the receiving hole 17 is appropriately large. The gap 23 of It is set appropriately so that a gap of a size that can be maintained can be formed. Further, the upper surface 1 of the cylinder head 1 is located on the ceiling surface side of this receiving hole 17.
One end of the fuel injection valve mounting hole 15 and the glow plug mounting hole 16, which are formed from the b side toward the receiving hole 17 side, are each opened. The fuel injection valve 4 is installed in the fuel injection valve installation hole 15, and the glow plug 5 is installed in the glow plug installation hole 16 from the cylinder head upper surface 1b side.

Note that if the insert block 21 is not accurately fitted into the receiving hole 17 at a predetermined position, for example, when the glow plug 5 is installed, the heat generating part 18 of the glow plug 5 will not fit into the glow plug of the first piece 7. There is a risk of interference with the insertion hole 19 and the vicinity of the glow plug insertion hole 19 of the first piece 7 being locally heated and damaged. Therefore, in this example,
By driving the set pin 12 into the pin hole 24 formed across the mouth edge of the receiving hole 17 and the outer peripheral edge of the insert ring 11, the positioning of the receiving hole 17 and the insert block 21 in the circumferential direction can be accurately and easily performed. I am trying to do this so that I can do it. Further, the positioning of the receiving hole 17 and the insert block 21 in the vertical direction is achieved by the contact between the flange 11c formed at the lower end of the insert ring 11 and the shoulder 17a formed at the mouth edge of the receiving hole 17. It is done.

Further, in the above embodiment, the bottom surface 6a of the sub-combustion chamber 6 has an inclined bottom that is inclined at an appropriate angle with respect to the abutment surface 1a of the cylinder head 1, but in other embodiments of the present invention, As shown in FIG. 7, this bottom surface 6a can also be formed into a flat bottom parallel to the abutting surface 1a of the cylinder head 1. Incidentally, when the auxiliary combustion chamber 6 has a sloped bottom as in the embodiment shown in FIG. 1, it has the advantage that half misfires are less likely to occur, and on the other hand, as in the embodiment shown in FIG. The advantage of having a flat bottom is that it does not generate much HC or smoke in the exhaust gas, resulting in good exhaust characteristics.

Furthermore, in each of the above embodiments, the auxiliary combustion chamber 6
is formed by surrounding it with a first piece 7 and a second piece 8 made of ceramic material (that is, the chamber wall of the auxiliary combustion chamber 6 is entirely made of ceramic material), but in other embodiments of the present invention, For example, as shown in FIG. 8, a part of the chamber wall of the sub-combustion chamber 6 may be constructed of a metal member such as an insert ring 11.

(Effect of the invention) In the sub-combustion chamber of the diesel engine of the invention, when a plurality of ceramic pieces are brought together and fitted into an insert ring, a metal coating is applied to the outer peripheral surface of each ceramic piece in advance. Furthermore, since the metal coating layer of each ceramic piece and the insert ring are integrally connected by metallurgical joining means such as brazing or welding, it is resistant to combustion heat during engine operation. Therefore, even if the ceramic piece and the insert ring thermally expand and the joint tightening force acting between them decreases, it is possible to maintain a good bond between each ceramic piece and the insert ring. This has the effect of improving product reliability.

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional view of the essential parts of a swirl chamber type diesel engine equipped with a sub-combustion chamber according to an embodiment of the present invention, Fig. 2 is an enlarged view of a portion of Fig. 1, and Figs. 3 to 5 are sub-combustion The chamber manufacturing process diagrams, FIGS. 6 to 8 are longitudinal sectional views of a sub-combustion chamber according to another embodiment of the present invention. 1... Cylinder head, 2... Cylinder block, 3... Piston, 6... Sub-combustion chamber, 7, 8...
...ceramic piece, 9...auxiliary combustion chamber block,
11...insert ring, 13...spout, 14
... Main combustion chamber, 17 ... Receiving hole, 21 ... Insert block, 31 ... Metal coating layer, 32 ... Through hole, 33 ... Joint part.

Claims (1)

[Scope of utility model registration request] A diesel engine sub-combustion chamber comprising a plurality of ceramic pieces joined together in a metal insert ring, each ceramic piece having a metal coating layer on a surface that fits into the insert ring. and further characterized in that each ceramic piece and the insert ring are positioned relative to each other by metallurgical means such as brazing or welding applied between the insert ring and the metal coating layer. secondary combustion chamber.