JPH09236041A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent blow-by of combustion gas caused by elastic deformation and plastic deformation without deteriorating merits that an internal combustion engine is formed of an aluminum alloy. SOLUTION: On the lower surface of a cylinder head 2, a seal ring 30 having rectangular cross section is arranged in a part that it is brought in contact with a seal 27 on a grommet 23 side. The seal ring 30 is formed by dying a thick steel plate, has wide size in comparison with the bead 26 of a gasket main body 21, and is inserted in the lower part of the cylinder head 2 when casted. When the cylinder head 2 is clamped to a cylinder block 3, surface pressure is dispersed by the seal ring 30 so as to be applied on the cylinder head 2, and blow-by of combustion gas caused by elastic deformation and plastic deformation is completely prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine having a cylinder head made of aluminum alloy, and more particularly to a technique for preventing blow-through when a metal gasket is used.

[0002]

2. Description of the Related Art In recent years, in a diesel engine for an automobile, the maximum pressure (maximum in-cylinder pressure) in the combustion chamber tends to rise due to the improvement of intake efficiency by adopting four valves and adopting a supercharger. Therefore, as a head gasket interposed between the cylinder head and the cylinder block, a high-strength metal gasket is used in place of the conventional asbestos base gasket in order to prevent leakage of combustion gas (so-called blow-through). More often than not. The metal gasket is made of a metal plate such as a stainless steel plate, and has a bore hole formed in a portion corresponding to the cylinder bore. There are two types of metal gaskets, a single type and a laminated type.When forming the seal part, the former forms a ring-shaped bead by press molding around the bore hole, and the latter forms a separate body around the bore hole. Many are covered with a gasket.

[0003]

In many diesel engines for passenger cars having a relatively small load, the cylinder head is made of an aluminum alloy casting in order to reduce the engine weight and improve the heat dissipation. However, when the above-described metal gasket is used in this type of engine, there is a possibility that combustion gas may blow through due to elasticity or plastic deformation of the cylinder head.

As is well known, in diesel engines,
Since the cylinder pressure is higher than that of a gasoline engine, the cylinder head is firmly fastened to the cylinder block. At this time, since the Young's modulus and the strength (elasticity limit) of the aluminum alloy are relatively low, the portion of the lower surface of the cylinder head that comes into contact with the seal portion of the metal gasket may undergo elastic deformation or plastic deformation. Since these deformations often occur unevenly, a gap is partially formed on the outer periphery of the cylinder bore, and the combustion gas blows through this gap. Since many cylinder blocks are made of cast iron, and cast iron sleeves are used even for those made of aluminum alloy, the above-mentioned deformation is unlikely to occur on the cylinder block side.

In order to solve such a problem, as described in JP-A-6-346786, Japanese Utility Model Laid-Open No. 1-141348, Japanese Utility Model Laid-Open No. 1-141353, etc., the ignition surface of the cylinder head It is also conceivable to cast a cast iron plate on the inside. However, in this method, the weight of the cylinder head increases and the heat dissipation deteriorates, and it is necessary to cast cast iron plates for the number of cylinders before casting the cylinder head itself, which increases the number of manufacturing steps. There was also a problem that the cost increased.

[0006] The present invention has been made in view of the above situation,
An object of the present invention is to provide an internal combustion engine capable of preventing blow-by of combustion gas due to elastic deformation or plastic deformation without impairing the advantage of being made of aluminum alloy.

[0007]

According to claim 1 of the present invention,
In order to achieve this object, a cylinder head made of an aluminum alloy that is attached to a cylinder block via a metal gasket, and a portion of the cylinder head that abuts a seal portion around the combustion chamber of the metal gasket, An internal combustion engine provided with a seal ring made of a material having a higher Young's modulus and strength than an alloy is proposed. As a result, elastic deformation and plastic deformation are less likely to occur at the portion of the cylinder head that abuts the seal portion of the metal gasket.

A second aspect of the present invention proposes the internal combustion engine of the first aspect, in which the seal ring is cast in when the cylinder head is cast. A third aspect of the present invention proposes the internal combustion engine according to the first or second aspect, wherein the cylinder head corresponds to a plurality of cylinders and adjacent ones of the seal rings are connected to each other.

A fourth aspect of the present invention proposes, in the internal combustion engine of the first to third aspects, that the seal ring is a steel plate press-formed product. Further, in claim 5, claims 1 to
In the internal combustion engine of No. 4, it is proposed that the seal ring is made of a material having a linear expansion coefficient substantially equal to that of the aluminum alloy.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment in which the present invention is applied to an in-line 4-cylinder diesel engine for passenger cars will be described in detail below with reference to the drawings. FIG. 1 is a vertical cross-sectional view showing an upper half of a diesel engine (hereinafter abbreviated as an engine) 1 according to an embodiment. Reference numeral 2 in the drawing is an aluminum alloy mounted on a cylinder block 3 made of cast iron. Shows a cylinder head of. The cylinder head 2 of this embodiment is
The intake camshaft 4 and the exhaust camshaft 5 are of the DOHC4 valve type in which the pair of intake valves 6 and exhaust valves 7 are respectively driven, and the subchamber 9 and the subchamber 9 are located directly above the combustion chamber 8. A fuel injection nozzle 10 for injecting fuel is provided. In the figure, 11 is a glow plug having its tip protruding in the sub chamber 9, and 12 is a piston held by a cylinder bore 13 so as to be vertically movable.

As shown in FIG. 2, a metal gasket 20 is interposed between the cylinder head 2 and the cylinder block 3. Note that FIG. 2 shows a state before the cylinder head 2 is fastened to the cylinder block 3, and after fastening, the metal gasket 20 is deformed into a flat plate shape. The metal gasket 20 of this embodiment is a laminated type made of thin stainless steel plates, and has a relatively thick gasket body 21.
And a relatively thin grommet 2 that covers the periphery of the bore hole 22.
3 and sheets 24, 2 which are relatively thin plates adhered to the upper and lower surfaces of the gasket body 21 so as to avoid the grommet 23.
It consists of five. The gasket body 21 has an annular bead 26 (in the present embodiment, surrounding the bore hole 22).
The width of 1 mm) is formed, and the surface of the grommet 23 corresponding to this bead 26 serves as the seal portion 27.

On the lower surface of the cylinder head 2 of the present embodiment, a seal ring 30 having a rectangular cross section is arranged at a portion contacting the seal portion 27 on the grommet 23 side. The seal ring 30 is a thick (5 mm in this embodiment) austenitic stainless steel plate is press-molded (punched), and is formed wider (5 mm in this embodiment) than the bead 26 of the gasket body 21. As shown in the perspective view of FIG. 3, the adjacent ring portions 31 are connected to each other in the cylinder column direction via the connecting portions 32 to form a siamese shape. The linear expansion coefficient of austenitic stainless steel is almost the same as that of aluminum alloy.

In this embodiment, the cylinder head 2 is manufactured by a low-pressure casting machine (not shown). In this case, after the seal ring 30 is positioned and fixed on the lower die, the sprue formed on the lower die is made of aluminum alloy. The procedure of pouring the molten metal is taken. As a result, the seal ring 30 is attached to the cylinder head 2
The aluminum alloy is cast in the lower part of the mold, and the fine irregularities on the surface of the seal ring 30 generated during the press molding are infiltrated with the aluminum alloy, and both are firmly integrated. Although the lower surface of the cylinder head 2 is ground after casting, the lower surface of the seal ring 30 is also ground at the same time in this process.
The seal ring 30 does not protrude from the lower surface of the.

The operation of this embodiment will be described below. When the cylinder head 2 is fastened to the cylinder block 3, the metal gasket 20 is pinched by the cylinder head 2 and the cylinder block 3 according to the tightening force of a head bolt (not shown). At this time, as described above, in the diesel engine, since the cylinder head 2 is firmly fastened to the cylinder block 3, the seal portion 27 of the metal gasket 20 is strongly pressed against the lower surface of the cylinder head 2 and the gasket main body. A large surface pressure is locally generated at a portion of the 21 corresponding to the bead 26. However, in the cylinder head 2 of the present embodiment, since the wide seal ring 30 is disposed in this portion, the surface pressure is dispersed by the seal ring 30 and acts on the cylinder head 2 as shown in FIG. . Therefore, the cylinder head 2
Elastic deformation and plastic deformation did not occur, and the blow-through of combustion gas due to this was completely prevented. Since the seal ring 30 is made of a steel plate having high rigidity and strength, elastic deformation and plastic deformation do not occur even when a large surface pressure is applied. Further, since the material of the seal ring 30 has an elastic coefficient substantially equal to that of the material of the cylinder head 2, there is no risk that the seal ring 30 will come off due to the difference in thermal expansion with the cylinder head 2.

Although the specific embodiment has been described above, the aspect of the present invention is not limited to this embodiment.
For example, although the above-described embodiment is applied to the in-line four-cylinder four-valve diesel engine, the present invention may be applied to a single-cylinder engine, a V-type six-cylinder engine, or the like having a different number of cylinders or an arrangement thereof. It may be applied to a gasoline engine or the like. In addition, although the seal rings are of the Siamese type in the above-described embodiment, they may be independent for each cylinder, or in the case of a narrow-angle V-type engine in which the cylinder heads of the left and right banks are integrated, the seal rings of all cylinders may be used. You may make it connect. Further, in the above embodiment, the seal ring is cast into the cylinder head, but an annular groove may be formed in the cylinder head to press fit the seal ring. Further, cast iron, ceramics, or the like may be used as the material of the seal ring, and centrifugal molding or cutting may be used for the molding.
Furthermore, the specific configuration and specific shape of the device can be changed without departing from the spirit of the present invention.

[0016]

According to the internal combustion engine of the first aspect of the present invention, an aluminum alloy cylinder head mounted on a cylinder block via a metal gasket, and a seal around the combustion chamber of the metal gasket in the cylinder head. Since a seal ring made of a material having a higher Young's modulus and a higher strength than that of the aluminum alloy is provided at a portion that comes into contact with the portion, blow-by of combustion gas due to elastic deformation or plastic deformation can be prevented.

According to a second aspect of the present invention, in the internal combustion engine of the first aspect, since the seal ring is cast-in at the time of casting the cylinder head, it is possible to reduce the number of steps in manufacturing the cylinder head. You can Further, according to claim 3, in the internal combustion engine according to claim 1 or 2, the cylinder head corresponds to a plurality of cylinders, and adjacent ones of the seal rings are connected to each other. The number of points can be reduced and the setting on the mold becomes easy.

According to the fourth aspect, in the internal combustion engine according to the first to third aspects, since the seal ring is a steel plate press-molded product, the manufacturing cost can be reduced. According to claim 5, in the internal combustion engine of claims 1 to 4, the seal ring is made of a material having a linear expansion coefficient substantially equal to that of the aluminum alloy. The ring will not fall off.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an upper half of a diesel engine according to the present invention.

FIG. 2 is a vertical cross-sectional view showing an interposed state of a metal gasket.

FIG. 3 is a perspective view of a seal ring.

[Explanation of symbols]

 1 Engine 2 Cylinder Head 3 Cylinder Block 20 Metal Gasket 21 Gasket Main Body 23 Grommet 24, 25 Sheet 26 Bead 27 Seal Part 30 Seal Ring 31 Ring Part 32 Connection Part

Claims (5)

[Claims] 1. A cylinder head made of an aluminum alloy, which is attached to a cylinder block via a metal gasket, and a portion of the cylinder head that abuts on a seal portion around the combustion chamber of the metal gasket. An internal combustion engine, comprising: a seal ring made of a high-strength and high-strength material. 2. The internal combustion engine according to claim 1, wherein the seal ring is cast in when the cylinder head is cast. 3. The internal combustion engine according to claim 1, wherein the cylinder head corresponds to a plurality of cylinders, and adjacent ones of the seal rings are connected to each other. 4. The internal combustion engine according to claim 1, wherein the seal ring is a steel plate press-molded product. 5. The internal combustion engine according to claim 1, wherein the seal ring is made of a material having a linear expansion coefficient substantially equal to that of the aluminum alloy.