JPH09209825A - Cylinder head of diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the thin part of a cylinder head main body from being formed between a valve seat ring and a glow plug hole, by forming a part of the glow plug hole by a part of two valve seat rings composing two adjacent valve seats. SOLUTION: The cylinder head 40 of a diesel engine is equipped with valve seat rings 44 (44-1 to 44-4 ) per air cylinder, and fitting parts 48 (48-1 to 48-4 ) to which these valve seat rings 44 are fitted are formed to the cylinder head 40. The valve seat rings 44 are equipped with valve seats 44-1a to 44-4a in boundaries between inner circumferential surfaces and side surfaces exposed to a combustion chamber. Fuel injection nozzle holes 52 are formed to a cylinder head main body 42, and also a glow plug hole 54 is arranged between the valve seats 44-1a and 44-2a . At this time, an interval between the valve seats 44-1a and 44-2a is formed smaller than the diameter of the glow plug hole 54, and the glow plug hole 54 are formed by means of mechanical work after the valve seat rings 44 are pressed into.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder head of a diesel engine, and more particularly to a cylinder head used for a direct injection type diesel engine equipped with a glow plug.

[0002]

2. Description of the Related Art Conventionally, for example, actual Kaihei 2-74526.
As disclosed in Japanese Patent Publication No. 2003-242242, a direct injection type diesel engine equipped with a glow plug is known. FIG. 5 is a sectional view showing the structure of the main part of such a diesel engine. In a direct injection type diesel engine, a fuel injection nozzle 12 is arranged on a cylinder head 10. Further, a glow plug 14 is arranged at a position of the cylinder head 10 adjacent to the fuel injection nozzle 12.

The cylinder block 16 includes a cylinder 18
Are formed. A piston 20 is slidably inserted in the cylinder 18. In the piston 22,
A combustion chamber 22 is formed. The fuel injection nozzle 12 disposed in the cylinder head 10 has a tip end portion in the combustion chamber 2
It is arranged so as to be exposed at the central portion of 2. Further, the glow plug 14 is arranged so that its tip is exposed inside the combustion chamber 22.

In the field of diesel engines, a multi-valve diesel engine is known in which a plurality of intake valves and exhaust valves are provided for each cylinder. FIG. 6 shows a bottom view of a cylinder head 24 used in a multi-valve direct injection diesel engine equipped with a glow plug.

The cylinder head 24 comprises a cylinder head body 26 made of aluminum alloy or cast iron, and four valve seat rings 28 _{-1 to} 28 _-4 made of heat-resistant alloy steel or sintered alloy. ing. The valve seat rings 28 _{-1 to} 28 _-4 are annular members that form valve seats of two intake valves and two exhaust valves. The cylinder head body 26, the fitting portion 30 _-1 to 30 _-4 to outline the fitting of the valve seat ring 28 _-1 to 28 _-4
Is provided. Valve seat ring 28 _-1 ~ 28 _-4
Are press-fitted into the fitting portions 30 _-1 to 30 _-4 .

The cylinder head body 26 has a port 32 communicating with the openings of the valve seat rings 28 _{-1 to} 28 _{-4.
-1 to} 32 _-4 are provided. Port 32 _{-1 to} 32
_-4 is in a conductive state when the intake valve or the exhaust valve incorporated in the cylinder head 24 is separated from the valve seat constituted by the valve seat rings 28 _{-1 to} 28 _-4 , while the intake valve or the exhaust valve When the valve is seated on the valve seat constituted by the valve seat rings 28 _{-1 to} 28 _-4, it is in the shut-off state.

As shown in FIG. 5, the fuel injection nozzle 12 of the direct injection diesel engine is arranged so that its tip is exposed at the center of the combustion chamber 22. Further, the glow plug 14 is arranged near the fuel injection nozzle 12 so that its tip is exposed to the combustion chamber 14. In order to realize such an arrangement, the cylinder head body 26 shown in FIG. 6, the fuel injection nozzle holes 34 near the center of the four valve seat ring 28 _-1 to 28 _-4 Also, the valve seat ring 28 _- There is a glow plug hole 36 between ₁ and 28 _-2 ,
Each is provided.

According to the cylinder head 24 shown in FIG.
A multi-valve direct injection diesel engine with a glow plug is realized in which fuel is injected near the center of the combustion chamber. According to the heatel engine of this type, good startability can be obtained by causing the glow plug to generate heat during cold starting,
Fuel can be injected from the fuel injection nozzle into the combustion chamber in good balance, and high intake efficiency and exhaust efficiency can be obtained by using a plurality of intake valves and exhaust valves.

[0009]

FIG. 7 is a sectional view obtained when the cylinder head 24 is cut along the line VII-VII shown in FIG. As described above, the glow plug hole 36 of the cylinder head 24 is formed between the two adjacent valve seat rings 28 _-1 and 28 _-2 . Therefore, the cylinder head body 26 is provided between the valve seat ring 28 _-1 and the glow plug hole 36 and between the valve seat ring 28 _-2 and the glow plug hole 36.
Thin portions 26a and 26b are formed as a part of the.

On the bottom surface (the surface exposed to the combustion chamber) of the cylinder head 24, the stress caused by the fluctuation of the explosion pressure and the heat load due to the operation of the diesel engine, and the cold heat load due to the repeated operation / stop of the diesel engine The stress caused by is applied. Therefore, the thin-walled portions 26a and 26b of the cylinder head body 26, the valve seat ring 28 _-1 ,
A large stress acts on 28 _-2 .

The valve seat rings 28 _-1 , 28 _-2 made of heat-resistant alloy steel, sintered alloy or the like show high durability against such stress. However, the durability of the cylinder head body made of aluminum alloy or cast iron is not as high as that of the valve seat rings 28 _-1 , 28 _-2 . Therefore, in the cylinder head 24 shown in FIGS. 6 and 7, fatigue of the thin portions 26a and 26b is more likely to progress than fatigue of other portions.

Also in the cylinder head 24, if the distance between the valve seat rings 28 _-1 and 28 _-2 is sufficiently secured, the wall pressure of the thin portions 26a and 26b is sufficiently secured, and the thin portions 28 _-1 and 28-2 are secured. High durability can be _added to _-2 . However, valve seat rings 28 _-1 and 2
In order to secure a sufficient interval of 8 _-2 , ports 32 _-1 ,
It is necessary to reduce the diameter of 32 _-2 . For this reason,
The above measures have the disadvantage of reducing the intake or exhaust efficiency of the diesel engine. In this respect, the structure of the cylinder head 24 described above is a structure in which it is difficult to impart high durability to the entire cylinder head 24 while maintaining the intake efficiency and the exhaust efficiency of the diesel engine at a high level.

The present invention has been made in view of the above points, and provides a cylinder head capable of ensuring high durability in the entire cylinder head without reducing the intake efficiency and the exhaust efficiency of the diesel engine. The purpose is to

[0014]

The above object is achieved by the present invention.
As described in (1), a fuel injection nozzle hole formed in a portion corresponding to the vicinity of the center of the cylinder, and a plurality of fuel injection nozzle holes arranged around the fuel injection nozzle hole to form a valve seat of an intake valve and an exhaust valve. Valve seat ring,
In a cylinder head of a diesel engine having a glow plug hole formed between two adjacent valve seats, at least a part of each of the two valve seat rings forming the two adjacent valve seats is at least the glow valve. This is achieved by the cylinder head of a diesel engine forming part of the plug hole.

In the present invention, the fuel injection nozzle hole is formed at a portion corresponding to the center of the cylinder. Also, a plurality of valve seat rings are arranged around the combustion injection nozzle hole. Therefore, the glow plug hole to be formed near the fuel injection nozzle is formed between two adjacent valve seat rings. These valve seat rings are arranged such that their spacing is small relative to the diameter of the glow plug hole. The glow plug hole is formed so that the two valve seat rings themselves form at least a part of the glow plug hole.
According to this structure, the thin portion of the cylinder head body is not formed between the valve seat ring and the glow plug hole.

[0016] The above object is as described in claim 2.
A fuel injection nozzle hole formed in a portion corresponding to the vicinity of the center of the cylinder, and a plurality of valve seat rings arranged around the fuel injection nozzle hole to form a valve seat of an intake valve and an exhaust valve, In a cylinder head of a diesel engine having a glow plug hole formed between two adjacent valve seat rings, a cylinder head formed between each of the two adjacent valve seat rings and the glow plug hole. It is also achieved by a cylinder head of a diesel engine having a hollow portion near the boundary between the thin portion of the main body and the other portion of the cylinder head main body.

In the present invention, the glow plug hole is formed between the two valve seat rings. At this time, both of the two valve seat rings are surrounded by the cylinder head main body around their entire circumferences. As a result, these valve seat rings exhibit good thermal conductivity over their entire circumference. A thin portion of the cylinder head body is formed between each of the two valve seat rings and the glow plug. The thin wall portion of the cylinder head body is subjected to stress due to the explosion pressure of the diesel engine and the cold heat load. In the present invention, the hollow portion is formed between the thin portion of the cylinder head body and the other portion. The stress acting on the thin portion of the cylinder head body is absorbed by the cavity. Therefore, large stress is not transmitted to other parts of the cylinder head body.

Further, as described in claim 3, the above object is to form a fuel injection nozzle hole formed in a portion corresponding to the vicinity of the central portion of the cylinder and a valve seat of an intake valve and an exhaust valve. A plurality of valve seat rings arranged around the fuel injection nozzle hole and adjacent to each other.
In a cylinder head of a diesel engine, comprising a glow plug hole formed between two valve seat rings, a thin wall of a cylinder head body formed between each of the two adjacent valve seat rings and the glow plug hole. The parts are also achieved by a cylinder head of a diesel engine, the parts of which have a higher strength than the other parts of the cylinder head body.

In the present invention, the glow plug hole is formed between the two valve seat rings. The two valve seat rings exhibit good heat conductivity over the entire circumference because they are surrounded by the cylinder head body.
In the present invention, the thin portion of the cylinder head body formed between the two valve seat rings is provided with higher strength than other portions. Therefore, the thin part is
Despite its thin wall, it shows excellent durability.

[0020]

FIG. 1 is a bottom view of a cylinder head 40 of a diesel engine which is an embodiment of the present invention.
The cylinder head 40 is arranged such that the surface shown in FIG. 1 is the inside of the diesel engine, that is, the surface shown in FIG. 1 is exposed to the combustion chamber formed inside the diesel engine. It is fixed to the top of a cylinder block (not shown).

The cylinder head 40 has a cylinder head body 42 made of aluminum alloy, cast iron or the like. Further, the cylinder head 40 has four valve seat rings 44 _{-1 to} 44 _{-4 for} each cylinder of the diesel engine.
It has. A head bolt hole 46 for inserting a head bolt (not shown) for fastening the cylinder head 40 and the cylinder block into the cylinder head body 42.
Are formed.

A plurality of head bolt holes 46 are formed through the cylinder head main body 42 so that all the cylinders of the diesel engine are surrounded by six head bolt holes arranged at substantially equal intervals. . The head bolt hole 46 is formed by being cast when the cylinder head body 42 is molded, or by machining the cylinder head body 42 after the cylinder head body 42 is molded.

The cylinder head body 42 also has a fitting portion 48 into which the valve seat rings 44 _{-1 to} 44 _-4 are fitted.
_{-1 to} 48 _-4 are formed. The diameters of the fitting portions 48 _{-1 to} 48 _-4 are set to be substantially equal to the outer diameters of the valve seat rings 44 _{-1 to} 44 _-4 . In addition, the fitting portions 48 _{-1 to} 48 _-4
The depth of the is substantially equal to the ring width of the valve seat ring 44 _-1 to 44 _-4. Valve seat ring 4
4 _{-1 to} 44 _-4 are press-fitted inside the fitting portions 48 _{-1 to} 48 _-4 so as to be embedded in the cylinder head main body 42.

The valve seat ring 44 _-1 to 44 _-4, is an annular member composed of a heat-resistant alloy steel or sintered alloy or the like. The valve seat rings 44 _{-1 to} 44 _-4 are provided with tapered valve seats 44 _-1 a to 44 _-4 a at the boundary between their inner peripheral surfaces and the side surfaces exposed to the combustion chamber. ing. The valve seats 44 _-1 a and 44 _-2 a function as valve seats of intake valves (not shown) incorporated in the cylinder head 40. Also, the valve seat 44
_-3 a and 44 _-4 a function as a valve seat of an exhaust valve (not shown) incorporated in the cylinder head 40.

[0025] the cylinder head body 42, the port 50 _-1 to 50 _-4 having a diameter almost equal to the opening of the valve seat ring 44 _-1 to 44 _-4 are formed. Port 50
_-1 Oobi 50 _-2, a intake port of the diesel engine, in communication with the intake pipe (not shown). Also, port 50
_-3 and _50-4 are exhaust ports of the diesel engine, and are connected to an exhaust pipe (not shown).

The cylinder head body 42 is provided at a position corresponding to the center of the cylinder of the diesel engine, that is,
Substantially central portion of the region surrounded by the valve seat ring 44 _-1 to 44 _-4, a fuel injection nozzle hole 52 is formed.
The fuel injection nozzle hole 52 is a through hole that penetrates the cylinder head 40, and a fuel injection nozzle (not shown) is assembled therein. The tip portion of the fuel injection nozzle assembled in the fuel injection nozzle hole 52 has the cylinder head 4
When 0 is fixed on the cylinder block, it is exposed in almost the center of the combustion chamber of the diesel engine. The fuel injection nozzle hole 52 is formed by machining the cylinder head body 42.

The cylinder head 40 includes a valve seat 44.
_A glow plug hole 54 is provided between _-1 a and _44-2 a. The global hole 54 is a through hole that penetrates the cylinder head 40, and a glow plug (not shown) is assembled therein. The tip portion of the glow plug assembled in the glow plug hole 54 is attached to the cylinder head 40.
When is fixed on the cylinder block, it is exposed inside the combustion chamber of the diesel engine.

In the cylinder head 40 of this embodiment,
Valve seat ring 44 _-1 and valve seat ring 44 _-2
The interval between and is smaller than the diameter of the glow plug hole 54. That is, global blanking hole 54, after press-fitting the valve seat ring 44 _-1 and 44 _-2 cylinder head body 42, a cylinder head body 54,
The valve seat rings _44-1 and _44-2 are formed by performing a machining process for cutting a part thereof.

FIG. 2 is a sectional view obtained when the cylinder head 40 is cut along the line II-II shown in FIG. In FIG. 2, the shape indicated by the chain double-dashed line shows the outer shape of the valve seat rings 44 _-1 and _44-2 before the cutting of the glow plug hole 54 is executed.

As shown in FIG. 2, in the cylinder head 40 of this embodiment, the valve seat rings _44-1 and 4-4 are provided.
_4-2 itself forms a part of the side wall of the glow plug hole 54. According to this configuration, the valve seat ring 44
_-1 and _44-2 and the glow plug hole 54 do not form a thin portion of the cylinder head body 42.
Further, the valve seat rings _44-1 and _44-2 are high durability members made of a sintered alloy, a heat resistant alloy, or the like.
Therefore, even if the wall pressure is reduced due to the formation of the glow plug hole 54, the valve seat rings 44 _-1 , 4
_4-2 can maintain a sufficiently high durability. Therefore, according to the cylinder head 40 of the present embodiment, excellent durability can be ensured for the entire cylinder head 40.

Further, in the cylinder head 40 of this embodiment, since the distance between the valve seat rings 44 _-1 and _44-2 is small, it is necessary to secure a large opening area for the ports 50 _-1 and 50 _-2. You can Therefore, according to the cylinder head 40 of the present embodiment, it is possible to obtain an effect that a high intake efficiency can be secured in the diesel engine.

By the way, in the above embodiment, the glow plug hole 54 is formed between the valve seat rings _44-1 and _44-2 , but the present invention is not limited to this, and the glow plug hole is not limited to this. The plug hole 54 may be provided between the other two adjacent valve seat rings. In the above embodiment, the valve seat rings 44 _-1 and _44-2 correspond to "two valve seat rings forming two adjacent valve seats".

FIG. 3 shows a bottom view of a cylinder head 60 which is a second embodiment of the present invention. The cylinder head 60 is
A cylinder block (not shown) so that the surface shown in FIG. 3 is the inside of the diesel engine, that is, the surface shown in FIG. 3 is exposed to the combustion chamber formed inside the diesel engine. It is fixed on the upper part. In FIG. 3, the same parts as those shown in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

The cylinder head 60 has a cylinder head body 62 made of aluminum alloy, cast iron or the like. Further, the cylinder head 60 includes four valve seat rings 64 _-1 to 64 _{-4 for} each cylinder of the diesel engine.
It has. The cylinder head body 62, fitting portions 68 _-1 to the valve seat ring 64 _-1 to 64 _-4 fitted
68 _-4 are formed. Valve seat ring 64 _-1 ~
64 _-4 is press-fitted inside the fitting portions 68 _{-1 to} 68 _-4 so as to be embedded in the cylinder head body 62.

The valve seat rings 64 _-1 to 64 _-4 are annular members made of heat-resistant alloy steel, sintered alloy or the like, like the above-mentioned valve seat rings 44 _{-1 to} 44 _-4. The valve seat 64 _-1 a formed in a tapered shape at the boundary between the inner peripheral surface of the and the side surface exposed to the combustion chamber
.About.64 _-4 a. Valve seat 64 _-1 a, 64
_-2a functions as a valve seat of an intake valve (not shown) incorporated in the cylinder head 60. The valve seats 64 _-3 a and 64 _-4 a are _attached to the cylinder head 60.
It functions as a valve seat of an exhaust valve (not shown) incorporated in the.

The cylinder head 60 has a glow plug hole 70 between the valve seat rings 64 _-1 and _64-2 . The global hole 70 is a through hole that penetrates the cylinder head 60. Cylinder head 60 of this embodiment
In the above, the distance between the valve seat ring _64-1 and the valve seat ring _64-2 is set to be larger than the diameter of the glow plug hole 70. Therefore, between the valve seat ring 64 _-1 and glow plug hole 70, and between the valve seat ring 64 _-2 and a glow plug hole 70,
Thin portions 62a and 62b of the cylinder head body 62 are formed respectively.

FIG. 4 is a sectional view obtained when the cylinder head 60 is cut along the line IV-IV shown in FIG. As shown in FIG. 4, the cylinder head 60 includes a fitting portion 68 near the boundary between the thin portions 62 a and 62 b of the cylinder head body 62 and other parts of the cylinder head body 62.
_-1 and the glow plug hole 70 are provided with a communication hole 72, and a fitting portion 68 _-2 and the glow plug hole 70 are provided with a communication hole 74. Communication holes 72 and 74, the valve seat ring 64 _-1, 62 prior to the press-fitting _-2, is formed by machining the cylinder head body 62.

The thin portion 62a of the cylinder head body 62,
The stress due to the explosion pressure and heat load fluctuation associated with the operation of the diesel engine and the cold heat stress associated with the repeated operation / stop of the diesel engine act on 62b. Therefore, the fatigue of the thin portions 62a and 62b is more likely to progress than the fatigue of other portions of the cylinder head body 62.

However, since the stress acting on the thin portions 62a and 62b is absorbed by the communication holes 72 and 74, it is difficult to transmit the stress to other parts of the cylinder head body 62. In other words, according to the cylinder head 60 of the present embodiment, the thin-walled portions 62 and 62b of the cylinder head body 62 absorb the stress, so that the stress acting on other portions of the cylinder head body 62 can be relaxed. it can. Therefore, according to the cylinder head 60 of this embodiment, the durability of the entire cylinder head 60 can be substantially improved.

Further, in the cylinder head 60 of the present embodiment, the valve seat rings 64 _-1 , 64 _-2 are surrounded by the cylinder head main body 62 over their entire circumference. Valve seat ring 64 _-1, in order to impart excellent heat radiation against 64 _-2, the valve seat ring 64 _-1, advantageously greater the contact area between 64 _-2 and the cylinder head body 62. In this respect, the cylinder head 60 of this embodiment is superior to the cylinder head 40 of the first embodiment. Therefore, according to the cylinder head 60 of the present embodiment, it is possible to secure durability of the entire cylinder head 60 that is equal to or higher than that of the cylinder head 40 of the first embodiment.

By the way, in the above embodiment, the glow plug hole 70 is formed between the valve seat rings 64 _-1 and _64-2 , but the present invention is not limited to this and the glow plug hole 70 is not limited to this. The plug hole 70 may be provided between two other adjacent valve seat rings. In the above embodiment, the valve seat rings 64 _-1 and _64-2 are connected to the "adjacent two valve seat rings" according to claim 2 by the communicating holes 72 and 7.
4 corresponds to the cavity of the second aspect.

As described above, the cylinder head 60 shown in FIGS. 3 and 4 has the communication hole 7 in the cylinder head body 62.
By forming 2,74, the durability of the cylinder head 60 is substantially increased. On the other hand, the durability of the cylinder head 60 is also enhanced by forming the thin portions 62a and 62b of the cylinder head main body 62 with a material having higher strength than other parts of the cylinder head main body 62. You can

That is, in the cylinder head 60 shown in FIGS. 3 and 4, the thin-walled portions 62a and 62b are laser-plated or the thin-walled portion 6 is formed.
When high strength is imparted to the thin-walled portions 62a and 62b by fitting a high-strength block material to the portions where the 2a and 62b are formed, the second embodiment is performed without providing the communication holes 72 and 74. The durability equivalent to that of the cylinder head 60 of the example can be obtained.

[0044]

As described above, according to the first aspect of the present invention, it is possible to prevent the thin portion of the cylinder head body from being formed between the valve seat ring and the glow plug hole. Therefore, according to the cylinder head of the present invention, excellent durability can be ensured for the entire cylinder head.

According to the second aspect of the present invention, the stress acting on the thin portion of the cylinder head body is absorbed by the hollow portion, so that a large stress is prevented from being transmitted to other parts of the cylinder head body. be able to. Further, according to the present invention, the two valve seat rings arranged on both sides of the glow plug can be provided with good thermal conductivity over their entire circumferences. Therefore, according to the cylinder head of the present invention, excellent durability can be ensured for the entire cylinder head.

According to the third aspect of the invention, high durability can be imparted to the thin portion of the cylinder head body. Further, according to the present invention, the two valve seat rings arranged on both sides of the glow plug can be provided with good thermal conductivity over their entire circumferences. Therefore,
According to the cylinder head of the present invention, excellent durability can be ensured for the entire cylinder head.

[Brief description of drawings]

FIG. 1 is a bottom view of a cylinder head according to a first embodiment of the present invention.

FIG. 2 is a II-I of the cylinder head of the first embodiment shown in FIG.
FIG. 3 is a cross-sectional view obtained when cut along a straight line I.

FIG. 3 is a bottom view of a cylinder head according to a second embodiment of the present invention.

4 is a IV-I showing the cylinder head of the second embodiment in FIG.
FIG. 7 is a cross-sectional view obtained when cut along a V straight line.

FIG. 5 is a cross-sectional view showing a main structure of a direct injection diesel engine including a glow plug.

FIG. 6 is a bottom view of a cylinder head of a multi-valve type direct injection diesel engine including a glow plug.

FIG. 7 shows the cylinder head shown in FIG. 5 in FIG.
FIG. 7 is a cross-sectional view obtained when cut along the line VII.

[Explanation of symbols]

40; 60 cylinder head 42; 62 cylinder head body 44 _-1 to 44 _-4; 64 _-1 to 64 _-2 valve seat ring _{44 -1 a~44 -1 b; 64 -1} a~64 -2 b valve seat 50 _-1 to 50 _-4 port 52 Fuel injection nozzle hole 54; 70 Glow plug hole 70, 72 Communication hole

Claims (3)

[Claims] 1. A fuel injection nozzle hole formed in a portion corresponding to the vicinity of a central portion of a cylinder, and a plurality of fuel injection nozzle holes arranged around the fuel injection nozzle hole to form a valve seat of an intake valve and an exhaust valve. In a cylinder head of a diesel engine, comprising a valve seat ring and a glow plug hole formed between two adjacent valve seats, a part of each of the two valve seat rings forming the two adjacent valve seats. Form at least a part of the glow plug hole, the cylinder head of a diesel engine. 2. A fuel injection nozzle hole formed in a portion corresponding to the vicinity of a central portion of a cylinder, and a plurality of fuel injection nozzle holes arranged around the fuel injection nozzle hole to form a valve seat of an intake valve and an exhaust valve. A cylinder head of a diesel engine, comprising a valve seat ring and a glow plug hole formed between two adjacent valve seat rings, wherein a glow plug hole is provided between each of the two adjacent valve seat rings and the glow plug hole. A cylinder head for a diesel engine, comprising a cavity near a boundary between a thin portion of the cylinder head body to be formed and another portion of the cylinder head body. 3. A fuel injection nozzle hole formed in a portion corresponding to the vicinity of the center of a cylinder, and a plurality of fuel injection nozzle holes arranged around the fuel injection nozzle hole to form a valve seat of an intake valve and an exhaust valve. A cylinder head of a diesel engine, comprising a valve seat ring and a glow plug hole formed between two adjacent valve seat rings, wherein a glow plug hole is provided between each of the two adjacent valve seat rings and the glow plug hole. A cylinder head for a diesel engine, wherein a thin portion of the formed cylinder head body has higher strength than other portions of the cylinder head body.