JPH0861505A - Metal gasket - Google Patents

Abstract

PURPOSE: To secure sufficient sealing performance by suppressing subsidence of an iron sleeve to form the combustion chamber of an aluminum engine. CONSTITUTION: A metal gasket 1 is formed from two aux. plates 11, 12 which are laid one over the other on a base board 10, wherein the base board is made flat in the position 4a supporting an iron sleeve of a cylinder block 4, and beads 10b are formed on the farther side than a hole 2 for combustion chamber provided in the flat part 10a, and the first aux. plate 11 is made thinner than the base board, and the edge of the hole for combustion chamber is folded back. The tip 11a of the fold-back is positioned nearer the combustion chamber than the board end on the combustion chamber 6 side. The edge of hole for combustion chamber provided in the second aux. plate 12 is folded back, and the end 12a of the fold-back is laid on the flat part of the board. The plate thicknesses should meet the condition B>A>D>=C, where B is total plate thickness in the supporting position, A is the total plate thickness on the side nearer the combustion chamber than the supporting position, C is the total plate thicknesses in the position of beads, and D is a position of beads farther than the combustion chamber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention particularly relates to a metal gasket used in an aluminum engine in which the inner surface of a combustion chamber of the engine is composed of a cast iron sleeve.

[0002]

2. Description of the Related Art Aluminum cylinder blocks are often used in internal combustion engines. In this cylinder block, the inner peripheral surface of the combustion chamber is made of cast iron, and therefore a cast iron sleeve is fitted in the cylinder block. It has become. As means for attaching the cast iron sleeve to the cylinder block, there are means for forming a flange on the outside of the upper end of the sleeve to support this flange on the cylinder block, and for making the outer peripheral surface of the cast iron sleeve uneven and using this as a support portion for the cylinder. There is a means for integrally casting when the block is cast, and the seal between the cylinder block and the cylinder head is laminated as described in, for example, Japanese Utility Model Publication No. 6-6829 and Japanese Patent Laid-Open Publication No. 6-26575. Shaped metal gasket is used.

These conventional metal gaskets have a structure in which the total plate thickness of the laminated metal plates is maximized in the portion closest to the combustion chamber. Therefore, this has a sealing function due to the maximum surface pressure and a plate thickness equal to or less than the plate thickness. Has a stopper function that does not compress the gap between the cylinder block and the cylinder head.

[0004]

However, in the metal gasket of the prior art described above, the maximum load is input to the position closest to the combustion chamber between the opposed overlapping surfaces of the cylinder block and the cylinder head. That is, since the maximum surface pressure is designed to be applied to the position closest to the combustion chamber hole of the metal gasket, when the cylinder head is superposed on the cylinder block with the metal gasket interposed and the bolt is tightened, the aluminum gasket In the cylinder block, the maximum load is input to the end surface of the cast iron sleeve in the axial direction of the sleeve, so in the cast iron sleeve having the flange-shaped protrusion, the flange is the aluminum part of the cylinder block. Supported on the combustion chamber side of the cast iron sleeve, not on the flange. Because that is on the endmost, load is applied large aluminum portion for holding the cast iron sleeve. At the sleeve end without the holding part, it becomes a cantilever state, and by operating the engine in this state, the flange of the cast iron sleeve may be deformed, and many of the aluminum parts supporting the flange are close to the combustion chamber. There is a drawback that an uneven load is applied, the supporting aluminum part is deformed, and the high surface pressure applied to the aluminum part leads to sinking of the cast iron sleeve. Further, in the cast iron sleeve made of cast iron, the cast iron sleeve is formed by the input of the load at a place where the cylinder block and the cast iron sleeve are easily separated from each other due to a difference in coefficient of thermal expansion between aluminum and cast iron. May sink as described above and the peeling may be promoted. Due to such a phenomenon, the sealing performance of the metal gasket deteriorates, which causes blow-through of the high-pressure gas generated in the combustion chamber.

Therefore, an object of the metal gasket of the present invention is to prevent the iron sleeve from sinking and to secure a sufficient sealing property even in an engine having an aluminum cylinder block.

[0006]

According to a first aspect of the present invention, there is provided a metal gasket according to claim 1, in which a metal substrate having a combustion chamber hole and a bead surrounding the combustion chamber hole is formed. A cylinder block made of aluminum, in which first and second sub-plates made of different metal plates having holes for combustion chambers are superposed on each other, and an inner surface of the combustion chamber of the engine is formed by a cast iron sleeve, and a cylinder to be superposed on the cylinder block. It is premised on a metal gasket to be interposed between the head and the substrate, and the substrate is made flat at a supporting position for supporting the cast iron sleeve of the cylinder block, and the bead is provided on the side farther than the combustion chamber hole of the flat portion. The first sub-plate is made thinner than the substrate, and the edge of the combustion chamber hole is folded back so that the tip is located closer to the combustion chamber than the end of the substrate on the combustion chamber side. The folded end portion by folding the edge of the combustion chamber hole of the second sub-plate superimposed on the flat portion of the substrate, the total thickness of at the supporting position of the cylinder block B
When the total plate thickness on the combustion chamber side from the supporting position is A, the total plate thickness at the bead position is C, and the position farther from the combustion chamber of the bead is D, each plate thickness is ,
B>A> D = C.

Further, in claim 2, the first and second
When the sub plates are overlapped and the thicknesses thereof are different, the sub plate having the smaller plate thickness is folded back inside. Further, in a third aspect of the present invention, the first and second sub-plates are overlapped with each other, and the sub-plate on the concave side of the bead of the substrate is folded back so that the flat plate is overlapped with the flat part of the substrate. There is.

Further, according to a fourth aspect of the present invention, a surface pressure adjusting plate, which is thinner than the second sub-plate, is stacked on the side farther from the combustion chamber hole than the bead of the substrate, and the plate thicknesses are B> A. ＞ D ＞
It is designated as C.

[0009]

In the metal gasket of claim 1, as described above, B>A> D = C, that is, B (total plate thickness at the supporting position of the cylinder block) is maximized, and A (combustion chamber from the supporting position). The total plate thickness on the side) is the thickness next to B, D (the position farther from the combustion chamber of the bead) is the thickness next to A, and C (the total plate thickness at the bead position) is the same as D. Since it is thick, the surface pressure of the support position that supports the cast iron sleeve in the cylinder block is the highest between the opposing flat overlapping surfaces of the cylinder block and cylinder head, and the width of this high surface pressure portion is also secured sufficiently. Therefore, the sealing performance in this supporting position is maximized. Moreover, since it is the support position in the cylinder block that supports the surface pressure, the force for sinking the cast iron sleeve does not act.

Next, the surface pressure is higher on the combustion chamber side than the support position, and corresponds to the end surface position of the cast iron sleeve.
Here, the first and second sub-plates are folded back, the cross-sections of both sub-plates are U-shaped, and an arc of a small radius is formed. The thickness is twice the thickness due to the arc, and the thickness is close to the thickness B at the supporting position. However, the large part of this thickness is only the arc part having the small radius in the cross section. In addition, since the circular linear portion along the periphery of the combustion chamber has a small radius of curvature and the point where the two sub plates are stacked, elasticity is generated in the bent portion. In addition, between the overlapping surface of the cylinder head and the overlapping surface of the cylinder block, a gap is slightly different between the tightening bolts and between the tightening bolts due to the effect of the tightening force of the bolts, and this difference is far from the bolts. Although it appears slightly on the combustion chamber side from the support position, the gasket of the present invention absorbs the difference in the gap on the combustion chamber side by the elasticity, and thus the primary seal of the high pressure gas in the combustion chamber is obtained. I am doing it. On the other hand, since the seal is formed by the circular linear portion, the seal width is small, and therefore the surface pressure of this seal portion is high but the total load is low, and therefore the sinking of the cast iron sleeve does not occur.

The next highest surface pressure is at the bead position. The position of the bead and the position farther than the combustion chamber of the bead mean that the total thickness of the substrate and both sub-plates is the thickness A at the position.
Since it is smaller than B, the surface pressure is lower than these, but since the bead deforms the substrate in the thickness direction and the sealing performance is improved by the elasticity of the deformed portion, the surface pressure is higher than the position far from the combustion chamber, Therefore, the third seal is formed here.

Therefore, according to the metal gasket of the first aspect, since the total plate thickness of the supporting positions for supporting the cast iron sleeve on the cylinder block is maximized, the surface pressure is also maximized and the input to the cylinder block is also maximized. While the sufficient sealing performance is obtained here, the surface pressure of the cast iron sleeve on the end surface is high, but the area where the surface pressure is applied is small, and therefore the sinking of the cast iron sleeve is unlikely to occur. In addition to the seal at the two positions, since the bead also seals due to its elasticity, a tertiary seal is possible and the sealing performance is improved.

The bead may be a so-called full bead in which a part of the substrate is curved in an arc shape in section.
It is also possible to use a so-called step bead in which a part of the substrate is refracted at a predetermined inclination angle. According to the metal gasket of claim 2, since the sub-plate having the smaller plate thickness is folded back inside, the sub-plate can be naturally folded back, and the U-shaped cross section of the folded back sub-plate is possible. It is possible to reduce the radius of the circular arc and reduce the load on the cast iron sleeve.

According to the metal gasket of the third aspect, since the auxiliary plate on the concave side of the bead of the substrate is folded back and is overlapped with the flat portion of the substrate, the metal gasket is closer to the combustion chamber than the bead. Since the other sub-plate and the substrate are included in this sub-plate, it is possible to avoid the corner of the end of the sub-plate being located on the flat portion of the surface of the metal gasket.

According to the metal gasket of claim 4, since the surface pressure adjusting plate, which is thinner than the second sub-plate, is placed on the side farther from the combustion chamber hole than the bead of the substrate, the surface pressure adjusting plate is placed more than the bead position. The total plate thickness becomes larger at a position farther from the combustion chamber, so that the bead is less likely to be crushed and its durability is increased.

[0016]

1 to 3 show a first embodiment, and FIG. 1 is a plan view of a part of a metal gasket 1. In FIG. 1, reference numeral 2 is a combustion chamber hole, which is opened at a position corresponding to the combustion chamber of the engine, and reference numeral 3 is a bolt hole, which will be described later. Is a hole through which a bolt for tightening the cylinder head 5 is inserted. Further, the metal gasket has a hole communicating with the water jacket of the engine, etc., but is not shown.

FIG. 2 shows an engine composed of a cylinder block 4 and a cylinder head 5. The cylinder block 4 and the cylinder head 5 are made of an aluminum alloy, thus forming a so-called aluminum engine. The inner surface of the combustion chamber 6 formed in the cylinder block 4 is formed by a sleeve 7 made of cast iron, and the sleeve 7 is supported by the cylinder block 4 as follows.

That is, the sleeve 7 is formed with a flange 7a on the outer periphery of the upper end, and the cylinder block 4 is formed with a step portion 4a for supporting the flange 7a from below, and the step portion 4a is provided with the flange 7a. In the engaged state, the upper surface of the sleeve 7 is flush with the upper surface of the cylinder block 4, thereby forming a flat overlapping surface (deck surface) with the cylinder head 5 in the cylinder block 4. Thus, the step portion 4a of the cylinder block 4 is in the supporting position for supporting the sleeve 7. Further, the lower surface of the cylinder head 5 is also flat with a superposed surface (deck surface) with the cylinder block 4, and a metal gasket 1 is interposed between these superposed surfaces to seal between the superposed surfaces. There is.

This metal gasket 1 is composed of a single substrate 10 made of an elastic metal plate, a first sub plate 11 and a second sub plate 12 made of metal plates sandwiching the base plate 10 from above and below, and also made of a metal plate. And a plate 13 for adjusting the surface pressure, which is provided by several means such as spot welding and eyelets at a portion where the overlapping surfaces do not contact, that is, a portion protruding to the outside of the cylinder block 4 and the cylinder head 5. In each case, a combustion chamber hole 2 for a combustion chamber 6 of the engine is provided concentrically with the combustion chamber 6, and the combustion chamber hole 2 is formed in each plate 10, 11, 12 At the same time, it is a hole for the combustion chamber as the metal gasket 1.

A flat portion 10a is formed on the substrate 10 at a position above the supporting position 4a of the cylinder block 4, and a bead 10b is formed on the flat portion 10a on the side farther from the combustion chamber hole 2. Combustion chamber hole 2 of bead 10b
An inner flat portion 10c is formed on the farther side. In this embodiment, the bead 10b is a so-called full bead in which a part of the substrate 10 is curved in an arc shape in cross section.

A combustion chamber hole 2 is formed on the upper surface of the substrate 10 and a first sub-plate 11 thinner than the substrate 10 is superposed, and the edge of the combustion chamber hole 2 is folded back and folded back. The front end 11a of the substrate 10 is located closer to the combustion chamber 6 than the end of the substrate 10 on the combustion chamber 6 side is.
And the end surface of the tip 11a of the sub-plate 11 are opposed to each other. Reference numeral 11b is a folded portion of the sub plate 11.

On the lower surface of the substrate 10, the combustion chamber hole 2 is formed.
And a second sub-plate 12 having the same thickness as the first sub-plate 11 is overlaid. The second sub-plate 12 is folded back at the edge of the combustion chamber hole 2 while including the folded-back portion 11b of the second sub-plate 12, and the folded-back end 12a is brought into contact with the flat portion 10a of the substrate 10. Piled up. 12b is the secondary plate 1
It is a folded part of 2.

Thus, this metal gasket 1 is shown in FIG.
As shown in FIG. 5, from a position close to the combustion chamber hole 2, a position PA is formed by folding back two sub-plates 11 and 12, one substrate 10 and one sub-plate 11 and two folding back plates. Position PB consisting of sub-board 12 and each one sub-board 11, 12
Position PC consisting of and the bead 10b of one substrate 10
And a position PD including one substrate 10, each of the sub plates 11 and 12, and the surface pressure adjusting plate 13, respectively.
A is located on the upper surface of the sleeve 7 of the cylinder block 4, position PB is located on the support position 4a of the cylinder block 4 and flange 7a of the sleeve 7, and position PC is located on the upper surface of the aluminum alloy portion of the cylinder block 4. Then
The position PD is farther from the combustion chamber 6.

Here, the total plate thickness at the position PA is A,
When the total plate thickness at the position PB is B, the total plate thickness at the position PC is C, and the total plate thickness at the position PD is D, the respective plate thicknesses have a relationship of B>A>D> C. . The surface pressure adjusting plate 13 may be omitted as will be described later, but when omitted in this way, it goes without saying that the plate thicknesses have a relationship of B>A> D = C.

The state in which the metal gasket 1 is arranged between the cylinder block 4 and the cylinder head 5 is shown in FIG.
2, the state before the cylinder head 5 is fastened to the cylinder block 4 is shown in FIG. 2, and the metal gasket 1 is not yet crushed. Here, when the cylinder head 5 is pressure-bonded to the cylinder block 4 by tightening a bolt (not shown), the total plate thickness B is maximum at the position PB of the metal gasket 1. Therefore, between the cylinder block 4 and the cylinder head 5. Has the highest surface pressure, and the width of the portion having the highest surface pressure is sufficiently secured, so that the load applied to the metal gasket 1, the cylinder block 4, and the cylinder head 5 is maximum at this position PB. Therefore, the sealing performance is maximized at the position PB corresponding to the supporting position which is the step portion 4a of the cylinder block 4. This forms a second seal when viewed from the combustion chamber 6. Further, since the total plate thickness is maximum and the width is sufficiently secured, the position P is prevented in the sense that the cylinder block 4 and the cylinder head 5 are prevented from coming closer to each other.
B also serves as a stopper for the metal gasket 1. Moreover, since it is the supporting position (step portion 4a) in the cylinder block 4 that supports the surface pressure, the force for sinking the sleeve 7 does not act.

The next highest surface pressure is at the position PA where the total plate thickness A of the metal gasket 1 is present. This position PA corresponds to the end face position of the sleeve 7, which is the primary position when viewed from the combustion chamber 6. Forming a seal. Here, the sub plate 11 and the sub plate 1
2 is folded back, and the cross sections of both sub plates 11 and 12 are U.
Since the arc 11c having a small radius is formed inside the folded portion 11b of the inner sub-plate 11, the thickness of the metal gasket 1 is more than twice the thickness of the two sub-plates 11 and 12.
The bulge due to the arc 11c increases and becomes a thickness close to the thickness B at the position PB. The large part of this thickness is only the part of the arc 11c having the small radius in the cross section, and the combustion chamber 6 Since it is a circular linear portion along the peripheral edge of, while the surface pressure is high and the sealing performance is high, that portion is distributed in the circular linear shape and the width is narrow,
Therefore, the load input to the sleeve 7 is the position PB.
Since it is smaller than the above, the depression of the sleeve 7 does not occur. Therefore, the sleeve 7 is prevented from being deformed, and the roundness of the combustion chamber 6 is secured.

Further, since the surface pressure at the position PB is high, the flange 7a of the sleeve 7 is strongly pressed to the support position 4a. From this point as well, the sinking of the sleeve 7 is suppressed at the position PA. Further, when the cylinder head 5 is tightened to the cylinder block 4 by a tightening bolt (not shown), a strong tightening force is exerted around the combustion chamber 6 near the bolt hole 3 and the arc 1
1c is sufficiently crushed, and the warping of the cylinder head 5 does not sufficiently transmit the tightening force of the bolt in a place far from the bolt hole 3, so that the crushing is halfway, and thus the tightening condition around the combustion chamber 6 is The difference in the clearance between the cylinder block 4 and the cylinder head 5 due to the difference is absorbed by the difference in the collapse of the arc 11c.

The next highest surface pressure is at the position PC where the bead 10b is located. The bead 10b has a higher surface pressure than the position PD because the bead 10b bends and deforms the substrate 10 in the thickness direction and improves the sealing performance by the elasticity of the deformed portion. Therefore, the third seal is formed here. There is. According to the first embodiment, both sub plates 11,
Although 12 has the same thickness, by making the thickness of the first sub-plate 11 smaller than that of the second sub-plate 12, it is possible to fold the first sub-plate 11 that is folded back inside without any difficulty, There is also an advantage that the radius of the arc 11c can be reduced and the load on the sleeve 7 can be reduced.

The second sub-plate 12 that covers the recessed side of the bead 10b of the substrate 10 is folded back outside the first sub-plate 11, and the sub-plate 1 is attached to the flat portion 10A of the substrate 10.
Since the first sub-plate 11 and the substrate 10 are included in the second sub-plate 12 on the combustion chamber 6 side of the bead 11b, the metal gasket 1 of the metal gasket 1 It is possible to avoid that the corners of the end portions of the sub plates 11 and 12 are located on the flat portion of the surface.

Further, since the surface pressure adjusting plate 13 which is thinner than the second sub plate 12 is provided on the surface of the substrate 10 on the convex side of the bead 10b on the side farther from the combustion chamber 6 of the bead 10b, it is more than the position PC. In the position PD, the total plate thickness is larger and the bead 10b is less likely to be crushed, so that its durability is increased. The height of the bead 10b and the substrate 10
The surface pressure adjusting plate 13 may be unnecessary depending on the conditions such as the material.

The magnitude of the surface pressure at each position of the metal gasket 1 is represented by a vertical line showing the pressure distribution in FIG. This pressure distribution shows a distribution at an average position around the combustion chamber 6, but it appears to be slightly different between the position near the bolt hole 3 and the position far from it. The difference occurs at the time of initial tightening of the bolt in the bolt hole 3, but the stopper function at the position PB of the metal gasket 1 prevents the subsequent change of the surface pressure due to aging. At the position PC where the bead 10b is located, two small peaks are formed on the cylinder head 5 side as the pressure distribution. This is because the center of the bead 10b is located at the center of the bead 10b when the cylinder head 5 is tightened to the cylinder block 4. This is because the cylinder head 5 is bent downward and is deformed as shown by the broken line, and the surface pressure is applied to the cylinder head 5 by the elasticity of the left and right portions.

FIG. 4 shows a second embodiment, in which the sub plate 1
This is an example in which 1 and 12 are folded back inside out from the first embodiment. Here, the folding arc 1 of the sub plate 12 that is on the inside
2c is larger than the folding arc 11c of the sub plate 11 of the first embodiment, but is the same as the first embodiment in that it is crushed by tightening between the cylinder block 4 and the cylinder head 5. Further, the surface pressure adjusting plate 13 may be interposed between the substrate 10 and the sub plate 11 as in the first embodiment, and the folded tip of the sub plate 11 is exposed on the lower surface of the sub plate 12. Other than that, the configuration and operation are the same as those of the first embodiment.

FIG. 5 shows a third embodiment, which is an example in which a sealing material 15 is interposed between the plates of the first embodiment and on the surface of the metal gasket 1. Although the surface pressure adjusting plate 13 is omitted in this figure, it goes without saying that this may be used. Other configurations and operations are the same as those in the first embodiment. FIG. 6 shows a fourth embodiment, which is an example in which a step bead 10d is formed on the substrate 10. The step bead 10d is composed of an inclined portion formed by refracting the substrate 10, and obtains a sealing action by the elastic restoring force of this refraction angle. Other configurations and operations are first
Same as the embodiment.

FIG. 7 shows a fifth embodiment, in which the support means for the sleeve 7 forming a part of the cylinder block 4 is the first.
This is different from the embodiment. In FIG. 7, the outer circumference of the sleeve 7 is provided with an unevenness, which is integrated when the cylinder block 4 is cast, and the sleeve 7 is attached by what is called a cast gurney. Therefore, the support position of the sleeve 7 in the cylinder block 4 is constituted by the portion 4b of the cylinder block 4 close to the sleeve 7. Thus, at the position of this portion 4b, the position PB of the metal gasket 1
Is positioned, and the same position PA is positioned at the end face position of the sleeve 7. The metal gasket 1 used here is the first except that the sub-plate 11 is thinner than the sub-plate 12.
Although it is the same as the embodiment, it goes without saying that the above-mentioned second to fourth metal gaskets 1 can be used.

[0035]

As described above, in the metal gasket of claim 1, the total plate thickness at the supporting position of the cylinder block is maximized, and the total plate thickness on the combustion chamber side from the supporting position is the second thickness. Since the position of the bead farther from the combustion chamber and the position of the bead and the total plate thickness of the third are the same as each other, the cylinder block and the cylinder head have a flat overlapping surface that faces each other. The surface pressure of the supporting position for supporting the cast iron sleeve in the block is the highest, and the width of the portion with high surface pressure is sufficiently secured, so that the sealing performance at this supporting position is maximized and the surface pressure is supported. Since it is the supporting position in the cylinder block, it does not have a bad influence such as sinking on the cast iron sleeve of the aluminum engine block. Further, at the end surface position of the cast iron sleeve, which is on the combustion chamber side from the supporting position, the sub-plate is folded back to form an arc of a small radius, so that elasticity is generated and it is generated around the combustion chamber far from the tightening bolt. In addition to absorbing subtle gap changes, the thickness of the metal gasket becomes larger than the total thickness of each plate by the amount of bulging due to the arc, and the surface pressure is high in a circular linear shape along the peripheral edge of the combustion chamber, resulting in high sealing performance. Is high. But,
Since the portion where the surface pressure is high is only distributed in the circular linear shape, and therefore the load input to the cast iron sleeve is smaller than the supporting position, the sinking of the cast iron sleeve can be prevented also in this point. Furthermore, since the bead deforms the substrate in the thickness direction and improves the sealing performance by the elasticity of the deformed portion, the surface pressure becomes higher than at the position far from the combustion chamber, and the bead also has the sealing function.

Therefore, according to the metal gasket of the first aspect, since the total plate thickness of the supporting positions for supporting the cast iron sleeve on the cylinder block is maximized, the surface pressure is also maximized and the input to the cylinder block is also maximized. While sufficient sealing performance and stopper performance have been obtained here, sinking of the cast iron sleeve is unlikely to occur because the surface pressure applied to the end surface of the cast iron sleeve is high, but the surface pressure loading area is small. In addition to the seal at the two positions, since the bead also seals due to its elasticity, a tertiary seal is possible and the sealing performance is improved.

According to the metal gasket of the second aspect, since the sub-plate having the smaller plate thickness is folded back inside, the sub-plate can be folded back comfortably, and the U of the folded back sub-plate is U. The radius of the circular arc in the V-shaped cross section can be reduced, and the load on the cast iron sleeve can be reduced. According to the metal gasket of claim 3, since the sub-plate on the side of the concave portion of the bead of the substrate is folded back and is superposed on the flat portion of the substrate, the sub-plate on the combustion chamber side of the bead is subfolded. Since the other sub-plate and the substrate are included in the plate, and the folded tip of the sub-plate can be made to face the vicinity of the bead, the corner of the end of the sub-plate is flattened on the surface of the metal gasket. Has the effect of avoiding being located.

According to the metal gasket of claim 4, since the surface pressure adjusting plate, which is thinner than the second sub-plate, is placed on the side farther from the combustion chamber hole than the bead of the substrate, The total plate thickness becomes larger at a position farther from the combustion chamber, so that the bead is less likely to be crushed and its durability is increased.

[Brief description of drawings]

FIG. 1 is a partially cutaway plan view showing a first embodiment.

FIG. 2 is a sectional view showing a positional relationship between a metal gasket, a cylinder block and a cylinder head of the first embodiment.

3 is an enlarged cross-sectional view taken along line XX of FIG.

FIG. 4 is a sectional view similar to FIG. 3 in the second embodiment.

FIG. 5 is a sectional view similar to FIG. 3 in the third embodiment.

FIG. 6 is a sectional view similar to FIG. 3 in a fourth embodiment.

FIG. 7 is a sectional view similar to FIG. 2 in a fifth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal gasket 2 Combustion chamber hole 4 Cylinder block 4a Step part (supporting position) 4b A part close to a sleeve (supporting position) 5 Cylinder head 6 Combustion chamber 7 Sleeve (cast iron sleeve) 7a Flange 10 Substrate 11 First sub-plate 12 Second auxiliary plate 13 Surface pressure adjusting plate

Claims (4)

[Claims] 1. A metal substrate having a combustion chamber hole formed therein and forming a bead surrounding the combustion chamber hole, and a metal plate having another combustion chamber hole similarly formed on the metal substrate. And a second sub-plate, the metal gasket to be interposed between the superposed surfaces of the aluminum cylinder block formed by the cast iron sleeve on the inner surface of the combustion chamber of the engine and the cylinder head superposed on the aluminum cylinder block. The block is made flat at a supporting position for supporting the cast iron sleeve, and the bead is formed on the side of the flat portion farther than the combustion chamber hole, and the first sub-plate is made thinner than the substrate and the combustion chamber is formed. The edge of the working hole is folded back, and the folded tip is positioned closer to the combustion chamber than the end of the substrate on the combustion chamber side is, and the edge of the combustion chamber hole of the second sub-plate is folded back and the folded end is moved forward. Overlapped on the flat part of the substrate, the total plate thickness at the supporting position of the cylinder block is B, the total plate thickness on the combustion chamber side from the supporting position is A, and the total plate thickness at the bead position is A metal gasket, wherein each plate thickness is set to B>A> D = C, where C is C and D is a position farther from the combustion chamber of the bead. 2. The metal gasket according to claim 1, wherein the first and second sub-plates are overlapped with each other and the sub-plate having the smaller plate thickness is folded back inside. 3. The first and second sub-plates are overlapped with each other and folded back with the sub-plate on the concave side of the bead of the substrate facing outward, and this is laid on the flat part of the substrate. The metal gasket according to claim 1 or 2. 4. A surface pressure adjusting plate, which is thinner than the second sub-plate, is placed on the side of the substrate farther from the combustion chamber hole than the bead, and the plate thicknesses are set to B>A>D> C. The metal gasket according to claim 1, wherein the metal gasket is a metal gasket.