JPH07260001A - Metallic gasket - Google Patents

Abstract

PURPOSE:To decrease the number of metallic plates while having sufficient blocking performance by interposing a metallic gasket between a cylinder block and a head. CONSTITUTION:A metallic gasket 2 is formed by overlapping two base plates 5, 6 wherein beads 5a, 6a are formed along the edge of an opened hole 8 for a combustion chamber onto a sub plate 7 on which the hole 8 for the combustion chamber is formed. A soft steel ring 9 formed by turning up the edges of the hole 8 for the combustion chamber of the sub plate 7, and forming a rod-like soft steel having the thickness larger than the thickness dimensions of two base plates 5, 6, so as to surround the combustion chamber is turned up in the position to the combustion chamber 4 from the edges to the combustion chamber of the base plates 5, 6 and held to the inside, and a hold-in part 7b of the sub plate 7 is exposed to the combustion chamber 4 from the edges to the combustion chamber 4 of the base plates 5, 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal gasket interposed between a cylinder block and a cylinder head of an engine so as to close the deck surfaces of the cylinder block and the cylinder head.

[0002]

2. Description of the Related Art A metal gasket is used in an engine to seal between a cylinder block and a cylinder head. The metal gasket is basically a substrate made of an elastic metal plate, and a combustion engine. A combustion chamber hole that is concentric with the chamber is opened, and a bead is formed concentrically with the combustion chamber along the edge of the combustion chamber hole on the side far from the combustion chamber. By elastically deforming the bead, the elastic restoring force is utilized to close the space between the combustion chamber and the deck surface of the cylinder block and the cylinder head.

By the way, between the opposing deck surfaces of the cylinder block and the cylinder head, the tightening force is large at the position close to the bolt for tightening the cylinder head with respect to the cylinder block, and conversely at the position away from the bolt. The tightening force is unavoidable. This is because the cylinder head is made of a low-rigidity aluminum alloy to reduce the weight of the engine, and the distance between the combustion chambers is reduced to reduce the size and weight of the engine. This is because the rigidity of the portion between the combustion chambers of the cylinder head decreases as a result of factors such as narrowing the width of the head.

For this reason, between the deck surfaces of the cylinder block and the cylinder head, the surface pressure is different between a position near the tightening bolt and a position far from the bolt around the combustion chamber, and the surface pressure differs from the bolt. Even at a distant position, due to the difference in the surface pressure between the narrow portion and the non-width portion between the two combustion chambers,
The metal gasket for blocking the deck surfaces is
It is necessary to sufficiently follow the difference in the surface pressure to change the thickness in order to improve the closing function.

On the other hand, since it is necessary to reduce the weight of the metal gasket in accordance with the reduction in weight of the engine, the number of metal plates to be stacked to form the metal gasket is reduced as much as possible, and the thickness of the metal plate is large. It is also necessary to be thin. Therefore, conventionally, for example, Japanese Patent Laid-Open No. 1-67194
A metal gasket disclosed in Japanese Patent Publication has been proposed.
In this metal gasket, a ring with a wire diameter larger than the thickness of the middle plate is placed on the end face on the combustion chamber side of the middle plate with a relatively large thickness dimension, and this ring is folded back to a sub plate that covers the upper surface of the middle plate. Hold the center plate together with the middle plate, extend the folded end of the sub plate to the bottom surface of the middle plate, and sandwich the set of the middle plate and ring and the sub plate embracing them with elastic metal plates from both upper and lower sides. Both elastic metal plates are formed with beads that project toward the middle plate. Thus, according to this metal gasket, due to the difference in tightening force between the cylinder block and the cylinder head around the combustion chamber,
The deformation amount of the bead and the crush amount of the ring are made different from each other, and the crush amount of the ring is regulated by the thickness dimension of the intermediate plate to obtain an effective closing property at any position.

[0006]

However, according to the above-mentioned conventional technique, the intermediate plate is required to have a function of restricting the amount of crushing of the ring, and the elastic restoring function of the bead is required to the elasticity of the substrate. In addition to the substrate that is basically required as a metal gasket, there is a problem in that a middle plate with a large thickness dimension that regulates the collapse amount of the ring is required separately. Therefore, the thickness dimension of the metal gasket and the required number of metal plates are required. There is a problem that is increased. Further, since the substrates are arranged on the upper and lower surfaces of the sub plate enclosing the ring inside, the tightening force between the cylinder block and the cylinder head is 2
Since the ring acts on the ring through the one substrate and the two sub plates, the ring is unlikely to be crushed, and as a result, there is a problem that the crushing of the ring does not sufficiently follow the change in the tightening force.

[0007] Therefore, an object of the present invention is to reduce the number of metal plates required for a metal gasket by removing an extra metal plate while having a sufficient closing property. The object of the present invention is to reduce the thickness of the metal gasket as much as possible while maintaining a sufficient blocking property. Further, the object of the present invention is to prevent the ring from collapsing due to the difference in tightening force depending on the position between the cylinder block and the cylinder head. The object of the present invention is to add a function of restricting the collapse of the ring to the substrate, and the object of the present invention is to provide both the cylinder block and the cylinder head. The purpose is to prevent deformation of the metal gasket against relative movement of the deck surface in the surface direction.

[0008]

SUMMARY OF THE INVENTION The present invention is similar to two substrates in which a bead is formed along an edge of the combustion chamber hole on an elastic metal plate having a combustion chamber hole. A metal gasket, which is formed by stacking a sub-plate made of another metal plate in which a combustion chamber hole is opened, and is interposed between a cylinder block and a cylinder head of the engine, the metal gasket of the combustion chamber hole of the sub-plate. The mild steel ring formed by folding back the edges and surrounding the combustion chamber with rod-shaped mild steel having a thickness larger than the thickness dimension of the two substrates is further provided in the combustion chamber than the edge of the at least one substrate near the combustion chamber. The holding portion of the sub-plate is hugged inside the folded-back portion at a position nearer to expose the hugging portion of the sub-plate further toward the combustion chamber from the edge of the one substrate near the combustion chamber.

The folded-back end portion of the sub-plate enclosing the mild steel ring is located farther from the combustion chamber than the edges of both substrates near the combustion chamber, and two pieces are provided between the mild steel ring and the bead. It is preferable to stack the substrate and the two sub plates. If the rod-shaped mild steel forming the mild steel ring has a circular cross-section, the followability against crushing is high.

Further, it is preferable that the holding portion of the sub-plate is exposed closer to the combustion chamber than the edges of both substrates closer to the combustion chamber, and the edge of the one substrate closer to the combustion chamber is not exposed. , Located on the side farther from the combustion chamber than the mild steel ring, exposing the enclosing portion from this substrate toward the combustion chamber, and the edge of the other substrate closer to the combustion chamber toward the combustion chamber of the enclosing portion. May extend to the end of.

Further, if the folded-back end of the sub-plate is arranged on the surface of one of the substrates on which the bead protrudes, it is possible to prevent the bead from bending completely. In this case,
You may weld the said folding | returning edge part and one board | substrate. For this welding, any welding means such as spot welding or continuous laser welding along the continuous direction of the beads can be adopted.

In any of the above cases, the beads are
A so-called full bead in which a part of the substrate is curved in an arc shape in cross section can be used, and a so-called step bead in which a part of the substrate is bent at a predetermined inclination angle can be used. The respective beads of the two substrates can be full beads or step beads, or one of them can be a full bead and the other can be a step bead.

[0013]

According to the metal gasket of the present invention, when the metal gasket is deformed in a direction in which the cylinder head is crushed by tightening the cylinder head against the cylinder block, at least one of the ends of the substrate near the combustion chamber has an outer peripheral side of the mild steel ring,
That is, even if it is located on the side farther from the combustion chamber and the edge of the other substrate closer to the combustion chamber extends to the holding portion of the sub-plate,
Due to the deformation of this substrate, a part of this substrate that is slightly away from the edge close to the combustion chamber also enters the outer peripheral side of the mild steel ring, and on the outer peripheral side of the mild steel ring, both substrates and the sub-plate regulate the collapse of the mild steel ring. Will be done.

At this time, the mild steel ring is crushed by the cylinder block and the cylinder head to close the space between them (primary seal), and the two substrates and the sub-plates are formed on both deck surfaces of the cylinder block and the cylinder head. The gap between these decks is closed (secondary seal) while the gap is regulated as a stopper so as not to make it smaller than a predetermined value (secondary seal), and the elastic restoration force of the beads of both boards also similarly closes the deck surfaces. Yes (3rd seal). Thus, the first to third seals sequentially block the deck surfaces in three steps from the combustion chamber side.

On the other hand, the mild steel ring encased in the auxiliary plate is
At least one of the upper and lower surfaces is crushed by the deck surface not through the substrate but only by the sub-plate, so the crushing of the mild steel ring due to the tightening force of the cylinder head against the cylinder block is good, and therefore the primary seal is blocked. It is highly likely. To further explain the closing property of each seal, the metal gasket crushed by the tightening of the cylinder head against the cylinder block has a flat portion outside the bead (the side far from the combustion chamber) of both substrates and one sub-plate. There are a total of three components, and between the bead and the embracing part of the mild steel ring, there are four components including both substrates, the sub-plate, and the folded end of the sub-plate. The thickness of one plate serves as a stopper for preventing the total bending of the beads formed on both substrates and for preventing the mild steel ring from being crushed more than a predetermined amount.

Further, in the combustion chamber hole and in the direction away from the hole, the plate is formed between the stopper portion and the vicinity of the bolt hole in the flat portion outside the bead as described above.
Since there is a difference between the number of sheets and the number of sheets, when the surface pressure acts on the gasket, a thickness gradient occurs between the two, while the deck surface of the cylinder head bolted to the cylinder block has this gradient. Based on this, deformation occurs.
On the other hand, in the direction along the holes for the combustion chambers, the effect of the tightening force of the bolts is small between the plurality of bolts that tighten the cylinder head to the cylinder block, and the width between the combustion chambers of a multi-cylinder engine may be narrow. Join us,
Since the surface pressure of the cylinder head against the gasket on the cylinder block is also low, in some cases, such as when knocking occurs, the explosive pressure in the combustion chamber of the engine tends to cause a gap between the gasket and the cylinder head. The hugging portion of the ring has a large tightening force on the cylinder head near the tightening bolt and is largely crushed and deformed to the stopper height.On the other hand, the tightening force becomes small between the bolts, especially between the combustion chambers of a multi-cylinder engine. Therefore, the deformation amount of the embracing part of the mild steel ring becomes small. Thus, in this hug,
Since the portion having a low surface pressure is crushed in a narrow area and the portion having a strong surface pressure is crushed in a wide area, the surface pressure per unit area of the hugging portion is averaged over the entire circumference of the combustion chamber. Occlusion can be obtained.

Further, the folded end portion of the sub-plate enclosing the mild steel ring is positioned farther from the combustion chamber than the edges of both substrates close to the combustion chamber, and between the mild steel ring and the bead. By constructing a structure in which two substrates and two sub-plates are stacked, a total of four plates do not make the gap between both deck surfaces smaller than a predetermined amount, that is, the mild steel ring and the bead are crushed more than necessary. It functions as a stopper to prevent this.

When the rod-shaped mild steel forming the mild steel ring has a circular cross section, the followability against crushing is high at first and gradually lowers so that it is less likely to be crushed more than necessary. Further, when the hugging portion of the sub-plate is exposed closer to the combustion chamber than the edges of the two substrates that are close to the combustion chamber, the mild steel ring hugged by the sub-plate has the substrate from both the upper and lower surfaces. Since it is directly crushed by the deck surface through only the sub-plate, the followability of the crushing of the mild steel ring due to the tightening force of the cylinder head against the cylinder block is better, and from this point as well, the closure of the primary seal is high. Become.

On the contrary, the edge of one of the substrates, not the two substrates, closer to the combustion chamber is positioned on the side farther from the combustion chamber than the mild steel ring, and the hugging portion is exposed from the substrates toward the combustion chamber. , And the edge of the other substrate closer to the combustion chamber is extended to the end of the embracing portion closer to the combustion chamber, the deck surfaces of both decks face in the surface direction due to the relative deformation of the cylinder block and the cylinder head. When relatively moved, on the deck surface having the other substrate, it is possible to prevent the hugging portion from being deformed due to the movement of the deck surface.
Therefore, even when the deck surface or the surface of the other substrate in contact with the deck surface is a rough surface and the substrate is deformed as the deck surface moves, the hugging portion is prevented from moving integrally.

Furthermore, the folded back end of the sub-plate is
If you place it on the surface where the bead of one of the boards is projected,
Since the thickness of the sub plate serves as a stopper, it is possible to prevent the bead from fully bending and yielding. In this case, if the folded end of the sub-plate and one of the substrates are welded, the folded end of the sub-plate may be displaced with respect to the one of the substrates even if there is a gap between the deck surfaces due to the difference in thermal expansion between the cylinder head and the cylinder block. The part does not shift, and therefore the folded end does not drop off from the substrate.

[0021]

1 and 2 show a first embodiment of the present invention, and FIG. 2 is a plan view showing a part of a metal gasket.
It is FIG. 1A that the cylinder block and the cylinder head are arranged in the enlarged cross-sectional view taken along line XX of FIG. 2, and FIG. 1B is a part of FIG. 1A extracted. It is a figure.

In FIG. 1A, a cylinder head 3 is placed on a deck surface 1a on the upper surface of a cylinder block 1 of an engine via a metal gasket 2, and a deck surface 3a on the lower surface of the cylinder head 3 is in contact with the metal gasket 2. However, this figure shows the relationship between these positions, and since the cylinder head 3 is not tightened with the bolts to the cylinder block 1, the metal gasket 2 is not in a deformed state. Further, in the same figure, the middle of the combustion chamber 4 of the engine in the left-right direction is omitted, so that the diameter of the combustion chamber 4 is shown small.

The metal gasket 2 has two substrates 5 and 6 made of elastic metal plates and a sub-plate 7 made of a metal plate thinner than these between the substrates 5 and 6, and these are, for example, a deck. The surfaces 1a and 3a are not in contact with each other, that is, the portions protruding to the outside of the cylinder block 1 and the cylinder head 3 are connected at several points by means such as spot welding or eyelets. A combustion chamber hole 8 for forming the combustion chamber is formed concentrically with the combustion chamber 4, and the combustion chamber hole 8 is a combustion chamber hole of each of the plates 5, 6 and 7 and at the same time as the combustion chamber as the metal gasket 2. Has a hole.

In the upper substrate 5, the combustion chamber hole 8 is formed.
Bead 5a is formed along the edge of the bead 5a.
Form a so-called full bead in which a part of the substrate 5 is raised and curved in an arc shape in cross section. Similarly, a bead 6a is formed on the lower substrate 6 as well, in this case, a part of the substrate 6 is raised downward. Both beads 5a and 6a have the same diameter and are formed concentrically with the combustion chamber 4.
The diameters of a and 6a may be different, and the widths of the beads may be different from each other.

The edges of the two substrates 5 and 6 near the combustion chamber hole 8 are at the same position, and the edge of the auxiliary plate 7 between them is closer to the combustion chamber hole 8 than the two substrates 5 and 6. Also protrudes toward the combustion chamber hole 8 and the edge of the sub-plate 7 is folded back, and the folded end portion 7a is overlapped between the edge of the upper substrate 5 near the combustion chamber 4 and the bead 5a. There is. At this overlapped position, the stopper 11 is set as a state in which four metal plates are stacked in this order from the folded end 7a of the sub-plate 7, the end of the substrate 5, the middle part of the sub-plate 7, and the end of the substrate 6 from the top. With this structure, even when the space between the deck surfaces 1a and 3a is narrowed by tightening, the metal gasket 2 keeps the stopper 11 closed.
It is prevented from collapsing below the thickness of. More specifically, since the stopper 11 has a thickness greater than that of the portion farther from the combustion chamber 4 by the folded-back end portion 7a, this thickness portion functions as a stopper.

Further, since the folded-back end portion 7a of the sub-plate 7 is superposed on the upper surface of the upper substrate 5, this is also the bead 5a.
A stopper is provided to prevent the bead 5a from being crushed to the extent of buckling. A soft steel ring 9 is wrapped around the folded portion of the sub plate 7.
Is made of round bar-shaped mild steel having a thickness (diameter) larger than the total thickness of the two substrates 5 and 6, and is formed so as to surround the combustion chamber. Thus, the hugging portion 7b that holds the mild steel ring 9 in the sub-plate 7 is exposed further toward the combustion chamber 4 from the edges of both the substrates 5 and 6 that are closer to the combustion chamber 4, and the combustion chamber of the hugging portion 7b is also exposed. The end portion near 4 is flush with the wall surface of the combustion chamber 4, and the thickness of each portion of the metal gasket 2 of this embodiment is such that the beads 5a and 6a are the thickest when the surface pressure is not applied. The bead 5 becomes smaller in the order of the recess 7b and the stopper 11.
The outermost portions of a and 6a (that is, the portion far from the combustion chamber hole 8 and the flat portion) are the thinnest.

A small hole indicated by reference numeral 12 in FIG.
It is a hole through which a bolt for tightening and fixing the.
In FIG. 2, the oil hole and the water hole are not shown. Further, it goes without saying that the metal gasket 2 may be coated on its inner and outer surfaces with a sealant.

Next, the operation of this embodiment will be described. First, when the cylinder head 3 is fastened to the cylinder block 1, the metal gasket 2 is deformed in the crushing direction.
More specifically, the bed surfaces 1a and 3a start elastic deformation in the direction in which the thickest beads 5a and 6a are first crushed, and then the mild steel ring 9 is crushed.
The deck surfaces 1a and 3a are in contact with 1 from above and below. At this time,
The beads 5a and 6a are pressed against the deck surfaces 1a and 3a by the elastic restoring force of the beads 5a and 6a by the deformation in the crushing direction to close the deck surfaces 1a and 3a.

Further, in the embracing part 7b, the mild steel ring 9 is crushed by the deck surfaces 1a and 3a via the sub-plate 7. However, since the mild steel ring 9 has a circular cross section, the surface pressure from the top and bottom is initially increased. Since it is received in a small area and the surface pressure increases as the mild steel ring 9 is crushed, the mild steel ring 9 is initially mounted on the deck surfaces 1a, 3a.
It easily collapses following the change in the gap between them, and its followability gradually decreases, and it becomes difficult to collapse.

The deck surfaces 1a and 3a are stoppers 1
At this point, the space between the deck surfaces 1a and 3a is prevented from becoming narrower than that, and thus the beads 5a and 6a are prevented from fully bending and yielding, and thus the elasticity of the beads 5a and 6a is reduced. It is possible to secure resilience. Thus, the gap between the deck surfaces 1a and 3a is primary sealed from the combustion chamber 4 side in the embracing portion 7b, secondary sealed in the stopper 11, and further the beads 5a and 6a.
Therefore, in this embodiment, the tertiary sealing is performed, and therefore, in this embodiment, a position where the surface pressure from the deck surfaces 1a and 3a is high (a position where the clearance is small, for example, a position near the hole 12 for bolt penetration). ), The combustion chamber 4 is closed three times, and a position where the surface pressure from the deck surfaces 1a and 3a is low, such as a position far from the hole 12, especially between the combustion chamber holes 8 (a large gap is present). Position), deck surface 1
Even if a and 3a are not crushed until they hit the stopper 11,
A double blockage is made between the hugging portion 7b and the beads 5a, 6a.

As described above, in this embodiment, the bead 5a, 6a formed on the substrates 5, 6 is formed by the folded end portion 7a of the sub-plate 7 folded over the substrate 5 to prevent the metal gasket 2 from being crushed. Of the bending radius of the bead is prevented, and the energy stored in the bead portions 5a and 6a is used to further prevent the vibration of the bead 5a and 6a. Since the deformation follows the deformation, the metal gasket 2 can be thin and the metal gasket 2 can be made thin with a sufficient number of metal plates to be used while having a sufficient closing property. In particular, since the gap between the deck surfaces 1a and 3a differs depending on the position around the combustion chamber 4, even if the surface pressure on the metal gasket 2 varies depending on the location, sufficient blocking can be achieved.

The folded-back end portion 7a of the sub plate 7 is the substrate 5
When it is folded back to the outside of the
It is preferable to weld a and the substrate 5. In FIGS. 1 and 2, reference numeral 13 indicates a welded portion, which may be spot welding or welding by a laser or the like which is continuous along the continuous direction of the beads 5a. As a result of the large number of cylinders in the engine due to such welding, even when the deck surfaces 1a, 3a are greatly displaced in the plane direction due to thermal expansion, the folded-back end portion 7a is accompanied by the displacement of the deck surfaces 1a, 3a. It can be prevented from moving.

FIG. 3 shows a second embodiment of the present invention and is a view corresponding to FIG. 1B of the first embodiment. That is, in this embodiment, the beads 5a of the substrate 5 are
While raising a part of the substrate 5 downward and curving in an arc shape in cross section, the bead 6a of the substrate 6 is raised in a part of the substrate 6 and curved in an arc shape in cross section. The sub plate 7 is opposed to the sub plate 7 from above and below. As a result, gaps 5b and 6b are formed between the sub plate 7 and the beads 5a and 6a. The folded end 7a of the sub-plate 7 is located on the lower surface of the edge of the upper substrate 5 and is arranged on the surface of the substrate 5 on which the bead 5a is raised to form a stopper for the beads 5a and 6a. .

According to the metal gasket 2 of this embodiment,
When the surface pressure is applied, the substrates 5 and 6 relatively approach each other while crushing the beads 5a and 6a, and the distance between the outer surfaces of the substrates 5 and 6 becomes smaller than the thickness of the embracing portion 7b, that is, the substrate 5 When the end portions of the fuel cells 6 and 6 near the combustion chamber have entered the outer peripheral side of the mild steel ring 9 (the side farther from the combustion chamber), the mild steel ring 9 begins to collapse. In addition, 2 which constitutes the stopper 11
The stopper 11 functions when the four substrates 5, 6 and the two sub-plates 7 in this case, that is, the total of four metal plates are polymerized without any gap, and the mild steel ring 9 and the beads 5a, 6a are further crushed. Prevent. Due to the deformation of each part, the primary seal, the secondary seal, and the tertiary seal function in the same manner as in the first embodiment, and other configurations and operational effects are also the same as in the first embodiment. Therefore, redundant description will be omitted.

FIG. 4 shows a third embodiment of the present invention, which also corresponds to FIG. 1B of the first embodiment. In this embodiment, the edge of the lower substrate 6 near the combustion chamber is extended to the lower side of the mild steel ring 9, and the extension 6
This is an example in which c is extended to the end of the hugging portion 7b near the combustion chamber. Further, in this embodiment, the folded-back end 7a of the sub-plate 7 is located below the mild steel ring 9 and is brought into contact with the upper surface of the extension 6c of the substrate 6.

According to this, when both the deck surfaces are moved in the plane direction due to the relative deformation of the cylinder block and the cylinder head, the extension surface 6c is moved by the movement of the deck surface on the deck surface of the cylinder block. Even if is moved, since the extension portion 6c covers the folding end portion 7a, the folding end portion 7a is not affected by the movement of the extension portion 6C, so that the folding end portion 7a is prevented from moving. . Except for the exposed portion of the hugging portion 7b of the sub-plate 7, the hugging portion 7b is sandwiched between the substrates 5 and 6 and pressed against each other with a strong surface pressure, so that the hugging portion 7b can be prevented from shifting toward the combustion chamber. Therefore, even when the deck surface of the cylinder block or the surface of the lower surface of the substrate 6 that is in contact with the cylinder block is a rough surface and the substrate 6 is deformed as the deck surface moves, the hugging portion 7b moves integrally. As a result, even the hugging portion 7b is prevented from being deformed.

Although the extension 6c is formed on the lower substrate 6 in this embodiment, it may be formed on the upper substrate 5 conversely. In this case, the folded-back end portion 7a of the sub plate 7 is also located above the mild steel ring 9. That is, the structure is vertically symmetrical with respect to the state shown in FIG. The points in which the primary seal, the secondary seal, and the tertiary seal function by the deformation of the respective parts configured in this manner are the same as in the first embodiment, and other configurations and operational effects are Since it is the same as the second embodiment, duplicated description will be omitted.

FIG. 5 shows a fourth embodiment of the present invention, which also corresponds to FIG. 1B of the first embodiment. In this embodiment, the beads 5a and 6a on the substrates 5 and 6 are used.
Is a so-called step bead in which a part of the substrates 5 and 6 is refracted at a predetermined inclination angle. Thus, the beads 5a, 6
Gaps 5b and 6b are formed between the upper and lower surfaces of the sub plate 7 and the substrates 5 and 6 in a portion farther from the combustion chamber than a. Further, the folded-back end portion 7a of the sub-plate 7 wraps around the lower side of the edge of the substrate 6 on the combustion chamber side to prevent the bead 6a from fully bending.
Also in this embodiment, the point that the substrate 6 and the folded-back end portion 7a of the sub plate 7 are welded at the welded portion 13 is the same as in the first embodiment.

The metal gasket 2 having such a structure is also the same as the first embodiment in that the primary seal, the secondary seal, and the tertiary seal function due to the deformation of the respective parts, and other structures and functions. The effect is the same as that of each of the above embodiments.

[0040]

As described above, according to the metal gasket of the first aspect, the metal gasket crushed by tightening the cylinder head against the cylinder block is located outside the bead (the side far from the combustion chamber). In the flat part, there are a total of three structures of both substrates and one sub plate, and between the bead and the embracing part of the mild steel ring, there are four structures of both substrates, the sub plate and the folded end of the sub plate. Therefore, the thickness of one sub-plate, which is larger than the other portions, serves as a stopper that prevents total bending of the beads formed on both substrates and prevents the mild steel ring from being crushed more than a predetermined amount.

Further, in the direction along the combustion chamber hole,
The effect of the tightening force of the bolts is smaller between the bolts that tighten the cylinder head to the cylinder block than in the vicinity of the bolts, and in particular, the width between the combustion chambers of a multi-cylinder engine is narrow. Since the surface pressure of the cylinder head against the gasket is also low, in some cases, such as when knocking occurs, the explosion pressure in the combustion chamber of the engine can easily create a gap between the gasket and the cylinder head. Since the portion near the tightening bolt has a large tightening force of the cylinder head, it is crushed and deformed to the stopper height, while the tightening force is small between the bolts, especially between the combustion chambers of a multi-cylinder engine. The deformation amount of the hugging portion of the mild steel ring becomes small. Thus, in this hugging portion, the portion having a low surface pressure is crushed in a narrow area and the portion having a high surface pressure is crushed in a wide area, so that the surface pressure per unit area of the hugging portion is averaged over the entire combustion chamber. Therefore, it is possible to obtain sufficient occlusivity.

Thus, in addition to reducing the number of required metal plates, the primary seal by the hugging portion of the sub-plate and the mild steel ring, the secondary seal by the portion for controlling the crushing, and the first seal by the bead. A sufficient sealability can be secured by the tertiary seal. On the other hand, since the mild steel ring wrapped in the sub plate is crushed by the deck surface through only the sub plate without interposing the substrate from at least one of the upper and lower surfaces,
The crushing of the mild steel ring due to the tightening force of the cylinder head with respect to the cylinder block has good followability, and therefore the obstruction of the primary seal can be enhanced.

Further, according to the metal gasket of the second aspect, in addition to the above-mentioned effect, it is possible to prevent the occurrence of a gap between the mild steel ring and the bead.
Since a structure in which one substrate and two sub plates are superposed on each other, it is possible to prevent a total of four plates from having a gap between both deck surfaces smaller than a predetermined size and crushing the mild steel ring and the bead more than necessary. Further, according to the metal gasket of claim 3, in addition to the above respective effects, since the rod-shaped mild steel forming the mild steel ring has a circular cross section, the followability against crushing is initially high, and gradually lowers more than necessary. It becomes difficult to be crushed, and it becomes easy to secure the blocking property.

Further, according to the metal gasket of the fourth aspect, in addition to the above respective effects, when the holding portion of the sub-plate is exposed further toward the combustion chamber than the edges of both substrates near the combustion chamber, the sub-plate Since the mild steel ring held in the upper part is crushed by the deck surface directly from both the upper and lower surfaces, not via the substrate and only the sub-plate, the crushing property of the mild steel ring due to the tightening force of the cylinder head against the cylinder block is less likely to follow. Even better, and from this point as well, the closing property of the primary seal is enhanced, and it is possible to improve the followability of the collapse of the ring with respect to the difference in tightening force depending on the position between the cylinder block and the cylinder head. Become.

Further, according to the metal gasket of the fifth aspect, in addition to the above respective effects, the edge of one of the substrates near the combustion chamber is extended to the end of the holding portion near the combustion chamber. When the surface relatively moves in the surface direction, it is possible to prevent the hugging portion from being deformed due to the movement of the deck surface on the deck surface having the substrate. Therefore, even when the deck surface or the substrate surface in contact with the deck surface is a rough surface and the substrate is deformed along with the movement of the deck surface, the hugging portion is prevented from being integrally moved and deformed. .

Further, according to the metal gasket of the sixth aspect, in addition to the above respective effects, since the folded-back end portion of the sub-plate is arranged on the surface of one of the substrates on which the bead is projected, the sub-plate of the sub-plate is formed. The thickness serves as a stopper to prevent the bead from buckling. Furthermore, according to the metal gasket of claim 7, in addition to the effect of claim 6, since the folded end of the sub-plate and one of the substrates are welded, the difference in thermal expansion between the cylinder head and the cylinder block causes Even if the deck surfaces are misaligned, the folded-back end portion of the sub-plate does not shift with respect to the one substrate, and thus the folded-back end portion can be prevented from falling off from the substrate.

[Brief description of drawings]

FIG. 1 is a sectional view of a first embodiment.

FIG. 2 is a plan view of the first embodiment.

FIG. 3 is a sectional view of a second embodiment.

FIG. 4 is a sectional view of a third embodiment.

FIG. 5 is a sectional view of a fourth embodiment.

[Explanation of symbols]

 1 ... Cylinder block 1a ... Deck surface 2 ... Metal gasket 3 ... Cylinder head 3a ... Deck surface 4 ... Combustion chamber 5 ... Substrate 5a ... Bead 6 ... Substrate 6a.・ Bead 6c ・ Extended part 7 ・ ・ ・ Sub plate 7a ・ ・ Folded end 7b ・ ・ Holding part 8 ・ ・ ・ Combustion chamber hole 9 ・ ・ ・ Mild steel ring 11 ・ ・ ・ Stopper

Claims (7)

[Claims] 1. An elastic metal plate having a combustion chamber hole,
A cylinder block of an engine, which is formed by stacking two substrates, each of which has a bead formed along the edge of the combustion chamber hole, and a sub plate made of another metal plate in which the combustion chamber hole is similarly formed. In the metal gasket interposed between the cylinder head and the cylinder head, the edge of the combustion chamber hole of the sub-plate is folded back, and rod-shaped mild steel having a thickness larger than the thickness dimensions of the two substrates is formed so as to surround the combustion chamber. The soft steel ring formed by hugging the inside of the folded-back portion at a position closer to the combustion chamber than the edge of the at least one substrate closer to the combustion chamber, and hugging the sub-plate on at least one of the substrates. A metal gasket characterized by being exposed further from the edge near the combustion chamber toward the combustion chamber. 2. The folded end portion of the sub-plate enclosing the mild steel ring is located farther from the combustion chamber than the edges of both substrates near the combustion chamber, and between the mild steel ring and the bead. The metal gasket according to claim 1, wherein two substrates and two sub plates are stacked. 3. The rod-shaped mild steel forming the mild steel ring has a circular cross-section.
The described metal gasket. 4. The hugging portion of the sub-plate is exposed to a position closer to the combustion chamber than edges of the both substrates closer to the combustion chamber. Metal gasket. 5. An edge of one of the substrates closer to the combustion chamber is positioned on a side farther from the combustion chamber than the mild steel ring to expose the entangled portion from the substrate toward the combustion chamber, and the other substrate The metal gasket according to any one of claims 1 to 3, wherein an edge near the combustion chamber is extended to an end of the holding portion near the combustion chamber. 6. The metal gasket according to claim 1, wherein the folded-back end portion of the sub-plate is arranged on a surface of one of the substrates on which a bead is projectingly provided. . 7. The metal gasket according to claim 6, wherein the folded-back end portion of the sub-plate and one of the substrates are welded to each other.