JPH0577565U - Cylinder head structure of direct injection diesel engine - Google Patents

Abstract

(57) [Abstract] [Purpose] The purpose of the present invention is to prevent cracks due to thermal stress from being exposed to high temperature gas around the fuel injection nozzle mounting hole on the lower surface of the cylinder head. A circular recess 7 having a diameter two to three times the diameter of the mounting hole 6 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 a surface including the opening surface of the mounting hole 6. By providing the R portion 8 by connecting the inner peripheral surface and the inner end surface of the recessed portion 7 with a curved surface, the generation of cracks can be effectively prevented by reducing the heat load, and the edge portion on the inner surface of the recessed portion 7 can be eliminated. So that the occurrence of cracks can be suppressed.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a cylinder head structure for a direct injection diesel engine, and more particularly to a technology for preventing cracks in a cylinder head.

[0002]

[Prior Art]

 Conventionally, a fuel injection nozzle faces a combustion chamber composed of a cavity formed at the top of a piston and a cylinder head to directly inject fuel toward the inner peripheral surface of the cavity, a so-called direct injection diesel engine. It has been known. In such a direct-injection diesel engine, the fuel injection nozzle is inserted and mounted in a mounting hole formed in the cylinder head so that the tip injection hole faces the inside of the cylinder.

[0003]

[Problems to be solved by the device]

 By the way, in such a direct injection diesel engine, since the vicinity of the fuel injection nozzle mounting hole opening on the lower surface of the cylinder head is exposed to high temperature gas during combustion, a crack occurs around the mounting hole opening due to heat load (thermal stress). There was a problem that occurred.

Therefore, conventionally, as disclosed in Japanese Utility Model Laid-Open No. 1-149547, a recess is formed between the intake valve and the exhaust valve on the lower surface of the cylinder head to reduce the wall thickness of the water jacket, The above-mentioned heat load is suppressed by increasing the cooling effect of the cooling water in the water jacket. However, with the above-mentioned structure, it is not possible to sufficiently cope with the recent increase in the combustion temperature of the engine, and it is not enough to surely prevent the occurrence of the cracks.

In view of the above-described conventional problems, the present invention has a unique improvement in the shape of the lower surface of the cylinder head, which exposes the vicinity of the fuel injection nozzle mounting hole to high-temperature gas, receives thermal stress, and causes cracks. The purpose is to prevent

[0006]

[Means for Solving the Problems]

 Therefore, the cylinder head structure of the direct injection diesel engine of the present invention is used in a direct injection diesel engine having a fuel injection nozzle that is inserted into a mounting hole formed in a cylinder head and has a tip injection hole facing the inside of the cylinder. A circular recess having a diameter two to three times as large as the diameter of the mounting hole is formed 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 curved surface connects the inner peripheral surface and the inner end surface.

[0007]

[Action]

 In this structure, 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 is concentrated. Since the heat can be prevented and the heat is evenly dissipated, the surface temperature around the fuel injection nozzle mounting hole on the lower surface of the cylinder head can be lowered, and the generation of 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 cracking can be suppressed.

[0009]

【Example】

 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 the cylinder head 1. The intake port 2 and the exhaust port 3 are opened on the lower surface of the cylinder head 1, and an intake valve and an exhaust valve valve seat 4 (not shown) are provided on the peripheral portion of the opening of each port 2, 3. In addition, a water jacket 5 forming 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 laterally displaced 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 so that the tip injection hole faces the inside of the cylinder. Here, the circular recess 7 is formed on the surface of the lower surface of the cylinder head 1 around the opening of the fuel injection nozzle mounting hole 6 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, the R portion 8 is formed at the corner portion which is the boundary between the inner peripheral surface and the inner end surface of the recess 7.

The shape and size of each recess 7 are set as follows. Cavity 7 diameter = 2 to 3 times the diameter of the mounting hole 6 Cavity 7 depth = Valve seat 4 seat surface position of exhaust valve Corner R = Cavity 7 depth 5 to 10 times The depth of the recess 7 is 20 mm, the depth of the recess 7 is 1.6 mm, and the corner R is 15 mm.

A recess 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 structure, since the predetermined recess 7 is formed around the fuel injection nozzle mounting hole 6 on the lower surface of the cylinder head 1, the water jacket 5 of the cylinder head 1 is surrounded by 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 as the thickness is reduced, the cooling effect of the cooling water in the water jacket 5 can be easily obtained.

Further, 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 combustion gas heat can be prevented, the heat is evenly dissipated, 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 lowered. As described above, it is possible to reduce the heat load and effectively prevent the occurrence of cracks.

In particular, as a result of forming the R portion 8 at the corner portion which is the boundary between the inner peripheral surface and the inner end surface of the recessed portion 7, there is no edge portion, and cracking can be suppressed. The present invention is not limited to the configuration of the embodiment, and various modifications can be made based on the scope of the utility model registration request.

[0015]

[Effect of the device]

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

[Brief description of drawings]

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

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

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

FIG. 4 is an enlarged cross-sectional view of part A of FIG.

[Explanation of symbols]

 1 Cylinder head 6 Fuel injection nozzle mounting hole 7 Cavity 8 R part

Claims (1)

[Scope of utility model registration request] 1. A direct-injection diesel engine equipped with a fuel injection nozzle that is inserted into a mounting hole formed in a cylinder head and has a tip injection hole facing the inside of the cylinder.
The surface of the lower surface of the cylinder head around the fuel injection nozzle mounting hole opening including the mounting hole opening surface has a diameter of 2 to
A cylinder head structure for a direct injection diesel engine, characterized in that a circular recess having a diameter three times larger is formed, and an inner peripheral surface and an inner end surface of the recess are connected by a curved surface.