JP2521485B2 - Cylinder head gasket - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention fits a sub combustion chamber member to a cylinder head,
The present invention relates to a cylinder head gasket that is interposed between a cylinder block and a cylinder block in an internal combustion engine that forms a sub combustion chamber between the cylinder head and the sub combustion chamber member.

[Problems to be Solved by Prior Art and Invention]

FIG. 8 shows an example of an internal combustion engine having the auxiliary combustion chamber and a conventional cylinder head gasket.

In this type of internal combustion engine, a sub-combustion chamber member 2 having a circular bottom surface is tightly fitted (press-fitted) into a cylinder head 1, and the sub-combustion chamber member 2 and the cylinder head 1 are provided with a sub-combustion chamber. 3 is formed. The auxiliary combustion chamber member 2 is arranged so as to straddle both an area above the opening of the cylinder 4 and an area outside the opening of the cylinder 4. Reference numeral 5 is a cylinder block, 6 is a cylinder liner, 7 is a combustion injection nozzle, and 8 is a glow plug.
Further, 9 is a communication passage that connects the auxiliary combustion chamber 3 and the inside of the cylinder 4, and penetrates the lower portion of the auxiliary combustion chamber member 2.

In this type of internal combustion engine, gas leakage easily occurs from the gap between the outer wall of the auxiliary combustion chamber member 2 and the cylinder head 1. Further, due to the limits of processing accuracy and assembly accuracy, and the difference in the coefficient of thermal expansion between the material forming the auxiliary combustion chamber member 2 and the material forming the cylinder head 1, the lower surface of the auxiliary combustion chamber member 2 and the lower surface of the cylinder head 1 are There is a tendency for a step to occur between the two, and this step also tends to cause gas leakage.

Therefore, conventionally, in this type of internal combustion engine, for example, a cylinder head gasket 10 as shown in FIGS. 8 and 9 has been used. This conventional cylinder head gasket 10 is obtained by pressing a sheet made of a compound of rubber and asbestos on both sides of a hook steel plate 12 in which a large number of hooks 11 are projected on both sides, thereby forming the compound layer 13 of the steel plate 12 on the steel plate 12. Gasket body 14 formed on both sides
And the cylinder hole 15 provided in the main body 14 and the main body
Of the fourteen, a metal bore grommet 16 mounted around the cylinder hole 15 is provided.

A part of the bore grommet 16 is extended to a slightly outer side of the outer circumference of the lower surface of the auxiliary combustion chamber member 2 (16a indicates this extended portion). Therefore, in this gasket 10, in the peripheral portion of the cylinder hole 15 (hereinafter referred to as the first portion A), the bore grommets 16 are present on both surfaces of the gasket body 14, and the extension portion 16a of the bore grommet 16 is located. In the portion (hereinafter referred to as the second portion B), the bore grommet is provided only on one surface of the gasket body 14.
There are 16 and the rest (hereinafter referred to as the third part C)
Both sides of the gasket body 14 are bore grommets.
16 does not exist.

Here, the bore grommet 16 maintains a surface pressure sufficient to seal the gas in the first portion A, and further, the auxiliary combustion chamber member 2 and the first portion A in the second portion B (extension portion 16a). It is provided for the purpose of ensuring the surface pressure necessary to seal a small amount of gas passing between the and (so-called secondary sealing).

FIG. 7 shows the first portion A of the conventional gasket 10,
The relationship between compressive strain and compressive stress in the second portion B and the third portion C is shown respectively. Then, in a normal use state, the entire gasket 10 is compressed by about 10%, at this time, the compressive stress of the first portion A is 1000 kg / cm ² , the compressive stress of the second portion B is 300 kg / cm ² , The compressive stress in the portion C is about 100 kg / cm ² .

However, in such a conventional cylinder head gasket 10, (a) when a large stress acts on the first portion A that performs the primary gas seal at the peripheral portion of the cylinder hole 15, the rubber / asbestos compound 13 of that portion is applied. Exceeds the compressive elasticity limit, resulting in a decrease in sealing stress, an increase in the sealing gap, a gas leak, and damage to the bore grommet 16.

(B) A large thermal load is applied to the gas seal portion, that is, the first portion A and the second portion B, so that the rubber / asbestos compound 13 is apt to settle (creep) in these portions. Gas leakage is also likely to occur.

(C) Since the water holes and oil holes (not shown) provided in the third portion C are apt to be insufficiently sealed, apply a liquid gasket or attach a rubber ring. However, these operations are troublesome and reduce productivity. Further, when applying a liquid gasket, it is not always possible to obtain a satisfactory sealing effect.

(D) If the tightening force of the bolt is increased in order to sufficiently seal the surroundings of the water hole and oil hole, excessive stress will act on the rubber / asbestos compound 13 around the bolt, exceeding the compression elastic limit. And the gasket body 1 is destroyed.

(E) Since there is a thick layer of non-metallic material (that is, rubber / asbestos compound 13) in the gas seal part, that is, the first part A and the second part B, the heat conductivity of the gas seal part is poor, Since the function of releasing heat from the sub-combustion chamber member 2 to the cylinder block 5 and the like is not sufficient, cooling around the sub-combustion chamber 3 becomes insufficient.

There were drawbacks such as.

[Object of the Invention]

The present invention has been made in view of the above conventional problems, and can increase the effective tightening surface pressure of the gas seal portion even at a relatively low load, and can obtain an ideal surface pressure distribution, Even if a large stress is applied to the gas seal part, the compression elastic limit will not be exceeded, and even if a large heat load is applied, the gas seal part will not sag (creep), which is stable and excellent. Gas seal performance can be maintained,
Moreover, the heat conductivity of the gas seal is very good, the heat dissipation in the vicinity of the auxiliary combustion chamber can be made good, and the extremely excellent sealing performance against water and oil can be stably maintained. An object of the present invention is to provide a cylinder head gasket which does not require a liquid gasket to be applied around a hole and an oil hole or a rubber ring to be attached.

[Means for solving problems]

A cylinder head gasket according to the present invention includes a metal core plate, a cylinder hole provided in the core plate, an annular bead provided around the cylinder hole of the core plate, and a core plate of the core plate. A portion along the outer periphery of the auxiliary combustion chamber member slightly outside, an arc-shaped bead provided so that both ends thereof are continuous with the annular bead, and the annular bead is sandwiched from both sides, and the cylinder is provided in the arc-shaped bead. In a state of contacting only from the head and the side of the auxiliary combustion chamber member, the peripheral portion of the cylinder hole of the surface of the core plate on the side of the cylinder head and the auxiliary combustion chamber and the auxiliary combustion chamber member from the peripheral portion. A metal that is attached to the core plate so as to cover a portion extending slightly outside the outer periphery of the core plate and the peripheral edge of the cylinder hole in the surface of the core plate on the cylinder block side. Bore grommet of, the head side surface plate and the block side surface plate that are overlapped on the portion of the both sides of the core plate where the bore grommet does not exist, and the water hole and the oil penetrated through the core plate and the surface plate A hole, and a water hole bead and an oil hole bead that are respectively provided around the water hole and the oil hole of each of the surface plates and project to the outer surface side of the surface plate, and the head side The block-side surface plate is formed by coating both surfaces of a metal plate with a compressible material layer made of a compound containing a compressible fiber and an elastomer such as rubber. Among the initial thickness of each part of the gasket, initial thickness of t _D of the annular bead installation part, the initial thickness of the t _E of the arcuate bead set portion, the head-side surface plate and the block-side face sheet on both surfaces of the core plate is not superimposed Part (hereinafter,
When both the surface plate existing portions) and the initial thickness of the portion other than the water hole bead and oil hole bead installation portions is t _F , t _D ≧ t _E > t _F.

[Action]

In the present invention, since the annular bead and the arcuate bead are formed on the core plate in the gas seal portion, the effective tightening surface pressure of the gas seal portion can be increased even with a relatively low load.

Further, since t _D ≧ t _E > t _F , when the cylinder head is tightened, the thickness of the annular bead installation portion (initial value t _D ) and the thickness of the arc-shaped bead installation portion (initial value t _E ) will reach the initial thickness t _F other than the bead portion of both surface plate existing parts, (surface pressure of annular bead installation part)> (surface pressure of arcuate bead installation part)> (both tables An ideal surface pressure distribution (surface pressure at the face plate existing part) is obtained.

Further, in this gasket, the annular bead installation portion for performing the primary gas seal at the peripheral edge of the cylinder hole is entirely made of metal, so that even if excessive stress acts on this portion, the compression elastic limit will not be exceeded, so As in the case of the conventional cylinder head gasket, the reduction of the sealing stress, the expansion of the sealing gap, the gas leakage, the breakage of the bore grommet, etc. are not caused. Naturally, the sag property is low and a high torque holding force can be obtained, so that stable and excellent gas sealing performance can be maintained.

Further, as described above, since the annular ring installation portion is made of only metal, the heat dissipation is good, and even if a large heat load is applied, there is no occurrence of gas leakage due to fatigue (creep). . At the same time, the heat is well dissipated from the sub-combustion chamber member to the cylinder block and the like, so that the surroundings of the sub-combustion chamber are sufficiently cooled.

In addition, since water hole beads and oil hole beads are provided in both surface plate existing portions, the contact area with the cylinder head and the cylinder block is limited, so a small bolt tightening force can be used to remove water holes and oil holes. A sufficiently high contact pressure can be obtained around the hole.

Further, since the gasket body is configured by superposing the two surface plates on the core plate, the metal plate used for each surface plate can be made sufficiently thin. Further, since water hole beads and oil hole beads are formed on these thin metal plates, respectively, these bead portions (that is, water and oil seal portions) can have relatively high compressibility,
A stable and uniform surface pressure distribution can be obtained, a stable seal stress can be maintained at the bead portion, and a water / oil seal can be maintained extremely well.

Also, looking at the parts other than the water hole bead and the oil hole bead in both surface plate existing parts, since the compressive material layer is thin as described above, the sag property is extremely small, and a high torque holding force as a whole is obtained. can get.

Furthermore, since the water hole bead and oil hole bead can be formed by pressing, compared to the conventional case where a liquid gasket is applied around the water hole and oil hole or a rubber ring is attached, The productivity of the head gasket can be improved.

〔Example〕

Hereinafter, the present invention will be described based on embodiments shown in the drawings.

1 to 5 show an embodiment of the present invention (note that reference numerals 1 to 5 and 9 in these drawings denote the aforementioned eighth embodiment).
It shows the same internal combustion engine parts as in the figure). The gasket body 21 is formed by superimposing a head-side surface plate 23 and a block-side surface plate 24 on both surfaces of a core plate 22 having a plate thickness t ₂₂ = 0.3 mm.

As the core plate 22, it is preferable to use a hot-rolled steel plate (SPCC steel plate) or a stainless steel plate (SUS steel plate). In particular, in order to prevent the settling of the annular bead 26 and the arc-shaped bead 27 described later, it is relatively difficult. It is preferable to use a material having high hardness.

The head-side surface plate 23 has a plate thickness of 0.3 mm on both sides of the SPCC steel plate 23a, a base fiber made of a compressible inorganic fiber or a compressible organic fiber or both, a rubber material, and a rubber chemical,
Thin compressible material layer composed of compound with inorganic filler
23b is covered (FIG. 2 is an enlarged sectional view of the head-side surface plate 23). Similarly, the surface plate 24 has a plate thickness of 0.
Both sides of a 3 mm SPCC steel plate 24a are coated with a thin compressible material layer 24b made of a compound having the same composition as the compressive material layer 23b. The compressive material layers 23b and 24b are each 0.1 mm.
The following is preferable, and in the present embodiment, these compressible material layers 23b and 24b are each 0.075 mm on one side.
It has been. Therefore, the total plate pressure t ₂₃ , t _{24 of the} surface plates 23,24
Is 0.45mm respectively.

Incidentally, as the inorganic fibers constituting the base fiber of the compound constituting the compressible material layers 23b, 24b, asbestos, glass fibers, ceramic fibers, rock wool, mineral wool, fused silica fibers, chemically treated high silica fibers, Molten silicate alumina fiber, alumina continuous fiber, stabilized zirconia fiber, boron nitride fiber, alkali titanate fiber, whiskers, boron fiber,
Carbon fiber, metal fiber or the like can be used.

Further, as the organic fibers constituting the base fiber of the compound, aromatic polyamide fibers, polyamide fibers, polyolefin fibers, polyester fibers, polyacrylonitrile fibers, polyvinyl alcohol fibers, polyvinyl chloride fibers, poly Urea-based fibers, polyurethane-based fibers, polyfluorocarbon-based fibers, phenol fibers, cellulose-based fibers and the like can be used.

Further, as the rubber material constituting the compound,
Nitrile rubber (NBR), styrene-butadiene rubber (SB
R), isoprene rubber (IR), chloroprene rubber (C
R), butadiene rubber (BR), butyl rubber (IIR), ethylene-propylene rubber (EPM), fluororubber (FPM), silicone rubber (Si), chlorosulfonated polyethylene (CSM), ethylene vinyl acetate rubber (EVA), chloride Polyethylene (CPE), butyl chloride rubber (CIR), shrimp chlorohydrin rubber (ECO), nitrile isoprene rubber (NIR), natural rubber (NR), etc. can be used. Also, other types of elastomers may be used in place of the rubber material.

As the rubber product constituting the compound, sulfur, zinc oxide, magnesium oxide, peroxide, a vulcanizing agent such as dinitrorebenzene, and a thiazole compound, a polyamine compound, a sulfenamide compound,
Vulcanization accelerators such as dithiocarbamate compounds, aldehyde amine compounds, guanidine compounds, thiourea compounds and xanthate compounds can be used.

Further, as the filler, clay, talc, barium sulfate, sodium bicarbonate, graphite, lead sulfate,
Tripoli stone, wollastonite, etc. can be used.

A cylinder hole 25 is provided in the core plate 22. Then, the cylinder head 1 of the core plate 22 and the auxiliary combustion chamber member 2
Of the side surface, an annular portion 22a at the peripheral edge of the cylinder hole 25 and a crescent-shaped portion 22b (which is well shown in FIG. 4) extending from this portion to slightly outside the outer periphery of the lower surface of the auxiliary combustion chamber member 2 The head side surface plate 23 is not overlapped. Of the surface of the core plate 22 on the cylinder block 5 side,
The surface plate 24 is not overlapped with the annular portion 22c at the periphery of the cylinder hole 25.

On the annular portions 22c and 22c on both sides of the core plate 22, annular beads 26 are formed by pressing so as to form a concentric circle with the cylinder hole 25. The cross-sectional shape of the annular bead 26 is the same as the cylinder head 1 and the auxiliary combustion chamber member 2.
It has an arc shape that is convex toward the side. Further, the core plate 22 is formed with an arc-shaped bead 27 extending in an arc shape along the vicinity of the outer peripheral arc part of the crescent-shaped portion 22b by press working, and both ends of the arc-shaped bead 27 are annular beads.
26 consecutive times. The cross-sectional shape of the arcuate bead 27 is also an arcuate shape that is convex toward the cylinder head 1 and the auxiliary combustion chamber member 2. The heights H ₂₆ and H ₂₇ of the annular beads 26 and ₂₇ are both 0.2 mm.

The annular beads 26 are sandwiched from both sides in the portions 22a, 22b, 22c of the core plate 22 where the surface plates 23, 24 are not overlapped, but the cylinder head 1 and the auxiliary combustion chamber member 2 are provided in the arc-shaped beads 27. Plate thickness t ₂₈ = 0.45mm with only contact from side
Bore grommet 28 made of stainless steel is covered and attached (however, a slight gap is provided between the end of bore grommet 28 and the ends of surface plates 23, 24).

The core plate 22 and the surface plates 23, 24 have water holes 31 for passing cooling water and oil holes 32 for passing lubricating oil.
(See FIGS. 3 and 4), and bolt holes 33 (see FIGS. 3 and 4) for inserting the tightening bolts are provided. Water hole 31 and oil hole 3 of the surface plates 23, 24
As shown in FIG. 1, a water hole bead 34 and an oil hole bead 35 having an arcuate cross-section that protrude outwardly are provided in the peripheral portion of 2.
Are formed by pressing and these beads 3
4, 35 respectively surround the water hole 31 and the oil hole 32 in an annular shape (note that only the cross sectional shape of the water hole bead 34 is shown in FIG. 1, but the cross sectional shape of the oil hole bead 35 is also shown. (Beads 34 and 35 are indicated by alternate long and short dash lines in the plan views of FIGS. 3 and 4).

In the cylinder head gasket 1, since the annular bead 26 and the arcuate bead 27 are formed on the core plate 22 in the gas seal portion, the effective tightening surface pressure of the gas seal portion can be increased even with a relatively low load.

In addition, in the annular bead 26 installation section, the annular bead 26
There are boa grommet 28 on the front and back. Therefore, the initial thickness t _D of the gasket at the installation portion of the annular bead 26 is t _D = t ₂₈ × 2 + t ₂₂ + H ₂₆ = 0.45 × 2 + 0.3 + 0.2 = 1.4 mm.

Further, in the arcuate bead 27 installation portion, the bore log mat 28 is present on the surface of the arcuate bead 27 on the cylinder head 1 side and the auxiliary combustion chamber member 2 side, while the cylinder block 5
There is a block side surface plate 24 on the side surface. Therefore,
The initial thickness t _E of this gasket at this arcuate bead 27 installation portion is t _E = t ₂₈ + t ₂₂ + H ₂₇ + t ₂₄ = 0.45 +0.3 +0.2 +0.45 = 1.4 mm.

Further, in the remaining part of this gasket, that is, in the part where both surface plates are present, the surface plates are provided on both surfaces of the core plate 22.
23 and 24 are present, bore grommet 28 is absent.
Therefore, the initial thickness t _F of the gasket in the portion other than the bead 34 in the portion where both surface plates are present is t _F = t ₂₃ + t ₂₂ + t ₂₄ = 0.45 + 0.3 + 0.45 = 1.2 mm.

As described above, in this cylinder head gasket, the mutual relationship among the initial thicknesses of the annular bead 26 installation portion, the arcuate bead 27 installation portion, and both surface plate existing portions is t _D = t _E > t _F , When the cylinder head 1 is tightened as shown in FIG. 5, the thickness of the installation portion of the annular bead 26 (initial value)
t _D ) and the thickness of the installation portion of the arcuate bead 27 (initial value t _E ) reach the initial thickness t _F of both surface plate existing portions, so (surface pressure of installation portion of annular bead 26)> ( An ideal surface pressure distribution of (surface pressure of the arcuate bead 27 installation portion)> (surface pressure of both surface plate existing portions) is obtained (in the present invention, even if t _D > t _E > t _F , The above ideal surface pressure distribution can be obtained).

This will be described more specifically. The relationship between the compressive strain and the compressive stress in the annular bead 26 installation portion, the arcuate bead 27 installation portion, and the bead 34 portion of both surface plate existing portions is as shown in FIG. 6 ( The curve D shows the installation portion of the annular bead 26, the curve E shows the installation portion of the arcuate bead 27, and the curve F shows the bead 34 portion of both surface plate existing portions). In FIG. 6, the compressive stress on the vertical axis represents the compressive force per 1 cm of the length of each bead (unit: kg / cm). If this cylinder head gasket is tightened to a plate thickness of 1.25 mm at a predetermined tightening time, at this time, compression of the bead 34 part of the annular bead 26 installation part, the arcuate bead 27 installation part, and both surface plate existing parts is performed. Each amount is about 11%.

Therefore, from FIG. 6, the compressive stress of the annular bead 26 installation portion is about 200 kg / cm. Where the width of the bead 26
If the width is 1.5 mm, the width of the contact portion of the bead 26 is about 1 mm, and the contact surface pressure is about 2000 kg / cm ² .

Similarly, the compressive stress of the arcuate bead 27 installation part is 150k.
It is about g / cm and the contact surface pressure is about 1500 kg / cm ² . Also, the compressive stress of the bead 34 part where both surface plates exist is 50 kg / c.
The contact surface pressure is about 500 kg / cm ² . As a result, as described above, the ideal surface pressure distribution can be obtained.

Further, in this gasket, the annular bead 26 installation portion for gas sealing at the peripheral edge of the cylinder hole 25 is entirely made of metal, so even if excessive stress is applied to this portion, it is clear from the characteristics of FIG. Therefore, the compression elastic limit is not exceeded, and therefore, unlike the case of the conventional cylinder head gasket, there is no reduction in sealing stress, expansion of the sealing gap, gas leakage, and breakage of the bore grommet 28. Naturally, the sag property is low and a high torque holding force can be obtained, so that stable and excellent gas sealing performance can be maintained.

Furthermore, since the annular bead 26 installation portion is composed only of metal, it has good heat dissipation, and even if a large heat load is applied,
It does not cause a gas leak due to settling (creep). At the same time, the heat is well dissipated from the auxiliary combustion chamber member 2 to the cylinder block 5 and the like, so that the surroundings of the auxiliary combustion chamber 3 are sufficiently cooled.

Further, since the beads 34 are provided on both surface plate existing portions, the cylinder head 1 and the cylinder block 5 are
Since the contact area with respect to is limited, a sufficiently high contact pressure can be obtained around the water hole 31 and the oil hole 32 with a small bolt tightening force.

Further, since the gasket body 21 is constructed by superposing the two surface plates 23, 24 on the core plate 22, the plate thickness of the steel plates 23a, 24a used for the surface plates 23, 24 can be made sufficiently thin. . Since the beads 34 are formed on the thin steel plates 23a, 24a, respectively, the beads 34 (that is, the water and oil seal portions) can have a relatively high compressibility, so that the beads 34 are stable and uniform. Surface pressure distribution can be obtained, stable sealing stress can be maintained in the bead 34 part,
Water and oil seals can be maintained extremely well.

Also, looking at the portion of the gasket main body 21 except for the bead 34 in both surface plate existing portions, since the compressive material layers 23b and 24b are thin as described above, the sag property is extremely small,
As a whole, a high torque holding force can be obtained.

Also, since the beads 34 can be formed by pressing,
The productivity of the cylinder head gasket can be improved as compared with the conventional case where a liquid gasket is applied around the water hole and the oil hole or a rubber ring is attached.

In the present invention, the metal constituting the core plate, the head side plate and the block side surface plate is not limited to the metal used in the above embodiment, and it is possible to use other kinds of metals.

Needless to say, the specific dimensions of each part of the cylinder head gasket of the present invention are not limited to the dimensions shown in the above embodiment.

〔The invention's effect〕

As described above, in the cylinder head gasket according to the present invention, (a) the effective tightening surface pressure of the gas seal portion can be increased even under a relatively low load.

(B) An ideal surface pressure distribution can be obtained.

(C) Even if a large stress is applied to the gas seal portion, the compression elastic limit is not exceeded.

(D) Even if a large heat load is applied, the gas seal portion does not sag.

(E) The heat conductivity of the gas seal portion is very good, and the heat dissipation near the auxiliary combustion chamber can be improved.

(F) From the above, not only can stable and excellent gas sealing performance be maintained, but also extremely excellent sealing performance against water and oil can be stably maintained, and the surroundings of water holes and oil holes can be maintained. There is no need to apply a liquid gasket or to attach a rubber ring to.

It is possible to obtain excellent effects such as.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a cylinder head gasket according to the present invention (the sectional position is the line II in FIG. 3), and FIG. 2 is a partially enlarged sectional view showing a gasket body in the embodiment. FIG. 3 is a plan view showing the example, FIG. 4 is a plan view showing only the gasket main body with the bore grommet removed from the embodiment, and FIG. 5 is attached to the internal combustion engine having the auxiliary combustion chamber. 6 is a sectional view showing the relationship between the compressive strain and the compressive stress in each part of the above embodiment, and FIG. 7 is a compressive strain in each part of an example of a conventional cylinder head gasket. FIG. 8 is a characteristic view showing a relationship with a compressive stress, FIG. 8 is a sectional view showing the conventional cylinder head gasket mounted on an internal combustion engine having an auxiliary combustion chamber, and FIG. 9 is the conventional cylinder head gasket. Cross section It is. 1 ... Cylinder head, 2 ... Sub combustion chamber member, 3 ... Sub combustion chamber, 4 ... Cylinder, 5 ... Cylinder block, 22
…… Core plate, 23 …… Head side surface plate, 23a …… Steel plate, 23b…
… Compressible material layer, 24 …… Block side surface plate, 24a …… Steel plate, 24b …… Compressible material layer, 25 …… Cylinder hole, 26 ……
Ring bead, 27 …… Arc bead, 28 …… Bore grommet, 31 …… Water hole, 32 …… Oil hole, 34 …… Water hole bead, 35…
... oil hole beads.

Claims (1)

(57) [Claims] 1. A sub-combustion chamber member is fitted to a cylinder head so as to extend over both an area on the opening of the cylinder and an area off the opening of the cylinder, and the cylinder head and the sub-combustion chamber member. In an internal combustion engine in which a sub combustion chamber is formed between the cylinder head and the sub combustion chamber member, and a cylinder head gasket interposed between the cylinder block, a metal core plate, and the core plate A cylinder hole provided in the core plate, an annular bead provided around the cylinder hole of the core plate, and a part of the core plate along a side slightly outside the outer periphery of the auxiliary combustion chamber member, both ends are An arc-shaped bead that is provided so as to be continuous with the annular bead, and the annular bead is sandwiched from both sides, but the arc-shaped bead is contacted only from the cylinder head and the auxiliary combustion chamber member side. In the state of, the peripheral portion of the cylinder hole of the surface of the core plate on the side of the cylinder head and the auxiliary combustion chamber member and the portion extending from the peripheral portion to slightly outside the outer periphery of the auxiliary combustion chamber member, and The metal bore grommet mounted on the core plate so as to cover the peripheral edge portion of the cylinder hole of the surface of the core plate on the cylinder block side, and the bore grommet on both surfaces of the core plate. Head-side surface plate and block-side surface plate that are superposed on a nonexistent portion, water holes and oil holes that penetrate the core plate and the surface plate, and the water holes and the oil holes of each of the surface plates Each having a water hole bead and an oil hole bead that project to the outer surface side of the surface plate, wherein the head side and block side surface plates are respectively on both sides of a metal plate, It was coated with a compressible material layer comprising a compound containing a compressible fiber and elastomer, of an initial thickness of each portion of the gasket, the initial thickness of the t _D of the annular bead installation section, the arcuate bead installation The initial thickness of the part is t _E , and the head side surface plate and the block side surface plate are overlapped on both sides of the core plate, and the portion other than the water hole bead and oil hole bead installation part Cylinder head gasket, characterized in that t _D ≧ t _E > t _F , where t _F is the initial thickness.