JPH064026Y2 - Ceramic sub-chamber in internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to an improvement of a ceramic auxiliary chamber in a diesel internal combustion engine.

(Prior Art) It is already widely known that a sub chamber of a diesel internal combustion engine is formed of a ceramic body to improve heat resistance and thermal efficiency. Such a ceramic body is shrink-fitted inside a metal ring provided in the cylinder head, and a key is inserted into the cutout portion between the outer peripheral surface of the ceramic body and the inner peripheral surface of the metal ring. It has a detent. However, conventionally, the ceramic body (21) and the metal ring (22) are in contact with each other, and the shrink fitting pressure acts, and the portion (A) shown by hatching in FIG.
In some cases, the tensile stress was concentrated in the edge portion (C) of the boundary with the portion (B) which was notched due to the insertion of the key (23) and the shrink fitting pressure did not act, and cracks were sometimes generated in the ceramic body. .

(Problems to be Solved by the Invention) The present invention solves the above-mentioned conventional problems, and an internal combustion engine that does not cause cracks due to stress concentration in a ceramic body shrink-fitted inside a metal ring. Has been completed to provide a ceramic subchamber.

(Means for Solving the Problems) The present inventors have studied the mechanism of crack generation in the conventional ceramic sub-chamber, and as a result, in the conventional structure as shown in FIG. 6 and FIG. (twenty three)
For inserting the metal ring (22) on the inner peripheral surface of the notch (24) and the ceramic body (21) also on the outer peripheral surface of the notch contour (25) Since and intersect with each other, an edge is formed at the intersecting portion, and a portion which is pressed by the metal ring (22) and a portion which is not pressed are generated on the surface of the ceramic body (21). It was discovered that a strong tensile stress concentration occurs near the boundary.

The present invention has been completed on the basis of such knowledge, and in a ceramic subchamber in an internal combustion engine in which a ceramic body having a circular cross section is shrink-fitted inside a metal ring and a key for preventing rotation is inserted between them. Characterized in that the contour line of the key insertion notch formed on the inner peripheral surface of the metal ring is located inside the contour line of the key insertion notch formed on the outer peripheral surface of the ceramic body. Is.

(Embodiment) Next, the present invention will be described in more detail with reference to an embodiment.
In FIGS. 2 and 2, (1) is a cylinder head of an internal combustion engine, (2) is a metal ring provided inside the cylinder head (1), and (3) and (4) are the metal rings (2 ) Is a ceramic body that is shrink-fitted inside. The ceramic bodies (3) and (4) are hollow bodies having a circular cross section that form a sub chamber, and the upper ceramic body (3) is a glow plug accommodating portion of the cylinder head (1).
A through hole (6) communicating with (5) and a fuel injection hole (8) communicating with the fuel injection nozzle accommodating portion (7) of the cylinder head (1) are provided. The lower ceramic body (4) has an injection hole (10) for injecting fuel gas toward the cylinder chamber (9). Keys (11) and (12) for preventing rotation are inserted between the ceramic bodies (3) and (4) and the metal ring (2). As shown in the cross section of FIG. 1, a metal ring is used in the present invention.
A key insertion notch (1) formed in an arc on the inner peripheral surface of (2).
The contour line (14) of (3) is the contour line (1) of the key insertion notch (15) formed by cutting the outer peripheral surface of the ceramic body (3) into a flat shape.
It is located inside 6).
It becomes like the figure. Although FIG. 1 shows an engaging portion between the upper ceramic body (3) and the key (11), the engaging portion between the lower ceramic body (4) and the key (12) has the same structure. Is adopted. The embodiment shown in FIG. 1 is an example in which a key having a flat surface on one side and a cylindrical surface on the other side is used. However, even if a cylindrical pin (11) is used as shown in FIG. As shown in Fig. 5, even when the prismatic pin (11) is used, the contour line (14) on the metal ring (2) side is replaced with the contour line on the ceramic body (3), (4) side.
If it is located inside of (16), the following operational effects will be obtained.

(Operation) In this structure, the ceramic body (3), (4) with a circular cross section, which is shrink-fitted inside the metal ring (2), is keyed.
The fact that the ceramic bodies (3) and (4) are prevented from sagging even when subjected to heat and vibration during use by the rotation prevention by (11) and (12) is no different from the conventional one. However, in the present invention, the contour line (14) of the key insertion notch (13) formed on the inner peripheral surface of the metal ring (2) is attached to the ceramic body.
Since it is located inside the contour line (16) of the key insertion notch (15) formed on the outer peripheral surface of (3) and (4), both contour lines do not intersect and the edge on the pressure distribution Does not occur, and
Since the metal ring (2) is overhanging rather than the end surface of the contact part between the ceramic body (3), (4) and the metal ring (2), the stress concentration in this part can be kept low. .

Here, the overhang means that when the ceramic body (3) is shrink-fitted to the metal ring (2) as shown in FIG. 9, the end portion of the metal ring (2) is contacted with each other (that is, shrink fit pressure). This means that the tensile stress value generated in the ceramic body (3) is significantly reduced as compared with the structure shown in FIG. 8 with such a structure. Of. On the contrary, if the contour line (14) on the metal ring (2) side is larger than the contour line (16) on the ceramic body (3) side,
The ceramic body (3) is in an overhang state rather than the end of the contact surface between the ceramic body (3) and the metal ring (2). At this time, as in FIG. Since a large tensile stress is generated on the outside of the portion in contact with the metal ring (2), the result is the same as the conventional product.

(Effects of the Invention) As is apparent from the above description, the present invention allows the contour line of the key insertion notch formed on the metal ring side to be the contour line of the key insertion notch formed on the ceramic body side. By arranging it inside, the concentration of tensile stress generated in this part of the ceramic body is relieved, and it is possible to reliably prevent loosening of the ceramic body due to heat and vibration during use and to prevent damage to the ceramic body due to cracks. This has contributed to the improvement of the reliability of the internal combustion engine by preventing it. Therefore, the present invention is of great practical value as it eliminates the problems of the conventional ceramic sub-chamber in the internal combustion engine.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view of an essential part showing a first embodiment of the present invention, FIG. 2 is a sectional view showing the whole of the embodiment, and FIG. 3 is a ceramic body side and metal in the first embodiment. FIG. 4 is a front view showing the relationship of the contour lines on the ring side, FIG. 4 is a partially cutaway perspective view showing the second embodiment of the present invention, and FIG. 5 is the third embodiment. FIG. 6 is a partially cutaway perspective view, FIG. 6 is a front view showing the relationship of contour lines in the conventional example, FIG. 7 is a plan view of a main part in the conventional example, and FIGS. 8 and 9 show a ceramic body and a metal ring. It is a figure which shows the stress generation condition by the relative relationship of. (2): Metal ring, (3), (4): Ceramic body, (11), (1
2): Key, (13): Notch for key insertion, (14): Contour line, (1
5): Notch for key insertion, (16): Contour line.

Claims (1)

[Scope of utility model registration request] 1. An internal combustion engine in which ceramic bodies (3) and (4) having a circular cross section are shrink-fitted inside a metal ring (2), and keys (11) and (12) for preventing rotation are inserted between the two. In the ceramic subchamber in the engine, the contour line (14) of the key insertion notch (13) formed on the inner peripheral surface of the metal ring (2) is attached to the outer peripheral surface of the ceramic body (3), (4). Notch for key insertion (1
A ceramic sub-chamber in an internal combustion engine, characterized in that it is located inside the contour line (16) of (5).