JP2565322Y2 - Cylinder head structure of direct injection diesel engine - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder head structure of a direct injection diesel engine, and more particularly to a technique for preventing a cylinder head from cracking.

[0002]

2. Description of the Related Art Conventionally, an engine in which a fuel injection nozzle is made to face a combustion chamber formed of a cavity formed at the top of a piston and a cylinder head and directly injects fuel toward the inner peripheral surface of the cavity. A so-called direct injection type diesel engine is known. In such a direct-injection diesel engine, the fuel injection nozzle is inserted and mounted in a mounting hole formed in a cylinder head, and a front injection hole faces the inside of the cylinder.

[0003]

In such a direct-injection diesel engine, however, a heat load (thermal stress) is generated because the vicinity of the fuel injection nozzle mounting hole on the lower surface of the cylinder head is exposed to high-temperature gas during combustion. Therefore, there is a problem that a crack is generated around the opening of the mounting hole.

For this reason, in the prior art, Japanese Utility Model Laid-Open Publication No. 1-1495
As shown in Japanese Patent Publication No. 47, a concave portion is formed between the intake valve and the exhaust valve on the lower surface of the cylinder head so as to reduce the wall thickness of the water jacket, and the cooling effect of the cooling water in the water jacket is increased. The heat load has been suppressed. However, the above configuration cannot sufficiently cope with the recent increase in the combustion temperature of the engine, and cannot be sufficiently satisfied to reliably prevent the occurrence of the crack.

In view of the above-mentioned conventional problems, the present invention is exposed to high-temperature gas around the fuel injection nozzle mounting hole by a unique improvement in the shape of the lower surface of the cylinder head, and cracks occur due to thermal stress. It is intended to prevent the situation.

[0006]

Therefore, the cylinder head structure of the direct-injection diesel engine of the present invention is provided with a fuel injection device which is inserted and mounted in a mounting hole formed in the cylinder head so that a front injection hole faces the inside of the cylinder. In a direct injection diesel engine provided with a nozzle , a tip injection hole of the fuel injection nozzle mounting hole is provided on a surface including the mounting hole opening surface around the fuel injection nozzle mounting hole opening on the lower surface of the cylinder head.
A circular recess having a diameter two to three times the diameter of the hole into which the hole is inserted was formed, and the inner peripheral surface and the inner end surface of the recess were connected by a curved surface.

[0007]

In this configuration, by forming a predetermined recess around the fuel injection nozzle mounting hole on the lower surface of the cylinder head, the cooling effect of the cooling water in the cooling water passage of the cylinder head can be easily obtained and the combustion gas heat Concentration can be prevented, and the heat is evenly radiated, so that the surface temperature around the fuel injection nozzle mounting hole on the lower surface of the cylinder head can be reduced, and cracks can be effectively prevented by reducing the heat load.

Further, since the inner peripheral surface and the inner end surface of the recess are connected by a curved surface, the edge portion is eliminated, and the occurrence of cracks can be suppressed.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. 1 to 4, an intake port 2 and an exhaust port 3 are formed in a cylinder head 1. The intake port 2 and the exhaust port 3 are opened on the lower surface of the cylinder head 1, and valve seats 4 for intake valves and exhaust valves (not shown) are provided around the openings of the ports 2 and 3. In addition, a water jacket 5 that forms a cooling water passage is formed in the cylinder head 1 so as to surround the intake port 2 and the exhaust port 3.

A mounting hole 6 for the fuel injection nozzle is formed at a position shifted laterally from a position between the intake port 2 and the exhaust port 3 of the cylinder head 1. A fuel injection nozzle (not shown) is inserted and mounted in the mounting hole 6, and the front end injection hole portion is
It is inserted into the hole portion 6A of the mounting hole 6 and faces the inside of the cylinder. Here, the circular recess 7 is formed on a surface around the opening of the fuel injection nozzle mounting hole 6 on the lower surface of the cylinder head 1 and including the opening surface of the mounting hole 6. The inner peripheral surface and the inner end surface of the recess 7 are connected by a curved surface. That is,
An R portion 8 is formed at a corner which is a boundary between the inner peripheral surface and the inner end surface of the recess 7.

The shape and dimensions of each recess 7 are set as follows. Recess 7 diameter = fuel injection out of mounting hole 6
2 of the diameter of the hole 6A into which the tip injection hole of the injection nozzle is inserted
３3 times the depth of the recess 7 = the seat position of the valve seat 4 of the exhaust valve Corner R = 5 to 10 times the depth of the recess 7 For example, the diameter of the recess 7 is 20 mm, and the depth of the recess 7 is 1.6.
mm and the corner R are formed to 15 mm.

A concave portion 9 is formed on the lower surface of the cylinder head 1 between the intake valve and the exhaust valve so as to reduce the wall thickness of the water jacket 5. According to this configuration, the predetermined recess 7 is formed around the fuel injection nozzle mounting hole 6 on the lower surface of the cylinder head 1, so that the water jacket 5 of the cylinder head 1 is formed around the fuel injection nozzle mounting hole 6 on the lower surface of the cylinder head 1. The thickness of the corresponding portion can be reduced, and the cooling effect of the cooling water in the water jacket 5 can be easily obtained by the reduced thickness.

Also, since the area of the lower surface of the cylinder head 1 around the fuel injection nozzle mounting hole 6 can be increased, the concentration of heat of the combustion gas can be prevented, the heat is evenly radiated, and the contact of the combustion gas is reduced. The surface temperature around the fuel injection nozzle mounting hole 6 on the lower surface 1 can be reduced. As described above, the heat load can be reduced, and the occurrence of cracks can be effectively prevented.

In particular, as a result of forming the R portion 8 at the corner which is the boundary between the inner peripheral surface and the inner end surface of the concave portion 7, there is no edge portion, and the occurrence of cracks can be suppressed. It should be noted that the present invention is not limited to the configuration of the embodiment, and various changes can be made based on the claims of the utility model registration.

[0015]

As described above, according to the cylinder head structure of the direct injection diesel engine of the present invention, the surface including the mounting hole opening surface around the fuel injection nozzle mounting hole opening on the lower surface of the cylinder head is specified. Since a circular concave portion having a diameter is formed and the inner peripheral surface and the inner end surface of the concave portion are connected by a curved surface, heat load can be reduced, and crack generation can be suppressed. It can be prevented.

[Brief description of the drawings]

FIG. 1 is a top view of a cylinder head showing one embodiment of the present invention.

FIG. 2 is a bottom view of the cylinder head.

FIG. 3 is a sectional view of a fuel injection nozzle mounting hole.

FIG. 4 is an enlarged sectional view of a portion A in FIG. 3;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Cylinder head 6 Fuel injection nozzle mounting hole 6A Hole part into which tip injection hole is inserted 7 Depression 8 R

Claims (1)

(57) [Scope of request for utility model registration] 1. A direct-injection diesel engine having a fuel injection nozzle inserted and mounted in a mounting hole formed in a cylinder head and having a front-end injection hole facing the inside of the cylinder.
A plane including the attaching hole opening surface in the fuel injection nozzle mounting hole openings around the lower surface of the cylinder head, intake the fuel injection nozzle
Of the attached holes , the diameter of the hole part where the tip injection hole is inserted is 2 to 2
A cylinder head structure for a direct-injection diesel engine, wherein a circular recess having a diameter three times as large is formed, and an inner peripheral surface and an inner end surface of the recess are connected by a curved surface.