JPH10205620A - Metal gasket for cylinder head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sufficiently increase sealing surface pressure by projecting two layered base material provided with convex beads for enclosing the circumference of holes for a combustion chamber, and a convex bead for a shim plate provided with a convex bead, in the same directions, and forming them in the nearly same shapes, and overlapping them on each circumferential part of the holes. SOLUTION: Elastic metal base plates 1, 2 which are formed comparative thick, are arranged around combustion chamber holes 4 separately from a circumferential rim 41 of the hole with beads 6 of crest cross sections for enclosing hole, a comparative thin metal plate made shim plate 3 is enlarged to only a circumferential part of the holes 4, and a convex bead 6' for enclosing the holes 4 is arranged on the same position as the convex beads 6 of the base materials 1, 2. The beads 6 of the base material 1, 2 and the bead 6' of the shim plate 3 are formed on the same position around the holes 4, are projected in the same direction, are formed in the nearly same shape, and are overlapped with each other. When they are mounted and fastened, its thickness is regulated by the shim plate 3, and the convex beads 6' are overlapped with each other so as to provide a seal line having high surface pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal gasket used as a cylinder head gasket for an engine of an automobile or the like.

[0002]

2. Description of the Related Art As shown in FIG. 6, a metal plate 12 having a folded portion 15 at the periphery of a hole 13 for a combustion chamber, and a chevron bead surrounding the hole 13 for a combustion chamber at a position outside the folded portion 15. Plate 11 provided with convex beads 14 such as
A metal gasket for a cylinder head, which is formed by laminating the above, is already well known. When this gasket is mounted between cylinder head H and cylinder block B and tightened,
As shown in FIG. 6, the highest surface pressure is generated around the hole for the combustion chamber at the position of the folded portion 15, and a seal line having a high surface pressure is also generated at the position of the bead 14. It is double sealed with the convex bead 14. In addition, the folded portion 15 functions as a so-called stopper for the bead 14, prevents the bend from bending, limits the size of the deformation of the bead compression and restoration that is repeatedly repeated based on the gas pressure cycle in the combustion chamber, and Prevents beads from sagging or damage during use.

[0003]

As described above, the gasket having a folded portion on the periphery of the hole for the combustion chamber and having a convex bead on the outside thereof has excellent performance as a metal gasket for a cylinder head as described above. However, the following problems remain. In other words, the metal plate having the folded portion needs to be folded, and it is necessary to use a relatively thin metal plate in view of the balance of the surface pressure between the periphery of the combustion chamber hole and the other portions. In addition, there is a danger that gas may leak or gasket may be damaged due to deformation or misalignment during long-term use due to stress acting on expansion and contraction of the cylinder head or cylinder block due to the stop.

Further, when the gasket is mounted between the cylinder head and the cylinder block and tightened, as described above, the largest surface pressure is generated at the immediate peripheral edge of the combustion chamber, and the peripheral edge of the combustion chamber is pressurized. The chamber may be deformed and its roundness may be impaired. Further, the gasket can generate a high surface pressure at the position of the folded portion and the position of the convex bead, and can double seal the combustion chamber. In other words, the surface pressure is dispersed, and the sealing surface pressure is reduced. Is not high enough. An object of the present invention is to provide a metal gasket for a cylinder head which does not have the above-mentioned disadvantages of a metal gasket having a folded portion.

[0005]

A metal gasket for a cylinder head according to the present invention, which achieves the above object, is made of an elastic metal plate having a large thickness. The metal gasket spreads over almost the entire joint surface between the cylinder head and the cylinder block, and burns. A two-layer substrate provided with a convex bead surrounding the chamber hole and a metal plate having a small thickness, the convex shape extending only around the periphery of the combustion chamber hole and surrounding the combustion chamber hole. A shim plate provided with a bead, wherein the two-layer substrate and the convex bead of the shim plate are formed in substantially the same shape at the same position so as to project in the same direction and overlap with each other; The substrate of the layers is overlapped on the periphery of each combustion chamber hole with a shim plate interposed therebetween.

In the metal gasket for a cylinder head according to the present invention, as described above, only the thick substrate spreads over almost the entire joint surface between the cylinder head and the cylinder block, and the thin shim plate is used for the combustion chamber. The gasket repeatedly receives stress based on the expansion and contraction of the cylinder head and cylinder block due to the operation and stoppage of the engine, because the gasket is sandwiched between two thick layers of the substrate that exist only in the periphery of the hole. However, there is no danger that the thin shim plate will be deformed or displaced.

[0007] In addition, the gasket thickness is adjusted by means of a shim plate at the periphery of the hole for the combustion chamber to increase the surface pressure, but a seal line having a high surface pressure is formed by a two-layer substrate and a convex bead of the shim plate. Since only the overlapping bead portions occur and the surface pressure is concentrated on this sealing line, a very high sealing surface pressure around the combustion chamber is obtained. Since the high sealing surface pressure acts not at the immediate periphery of the combustion chamber hole but at a position spaced from the hole, the deformation of the combustion chamber is reduced.

Further, in the present invention, the thickness of the sealing material layer covering the concave portion of the convex bead surrounding the hole for the combustion chamber of the substrate is made larger than the thickness of the sealing material layer covering other portions. In some cases, the surface pressure of the seal line formed in the bead portion can be further increased. Further, when the coating thickness of a portion of the sealing material layer covered by the concave portion that is separated from the bolt hole is made larger than the coating thickness of the portion close to the bolt hole, the surface pressure of the sealing line at the bead portion is increased. There is an advantage that can be equalized around the combustion chamber.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the drawings of an embodiment. FIGS. 1 and 2 show a metal gasket for a cylinder head according to an embodiment of the present invention.
FIG. 2 is a plan view, and FIG. 2 is an enlarged sectional view taken along line AA of FIG. However, FIG. 1 omits illustration of a cooling water passage hole, an oil passage hole, a bead for sealing these, and the like for simplification of the drawing. FIG. 1 shows a state where the surface is not covered with the sealing material layer.

In FIGS. 1 and 2, an elastic metal plate such as a stainless steel plate has a thickness of, for example, 0.2 to 0.3 mm.
The relatively thick substrates 1 and 2 extend over substantially the entire joint surface of the cylinder head and the cylinder block, and are provided with a plurality of combustion chamber holes 4 and bolt holes 5 arranged substantially evenly around the combustion chamber holes. And a cooling water passage hole, an oil passage hole, etc., not shown. The substrates 1 and 2 are provided with a bead 6 having a chevron-shaped cross section surrounding the hole 4 for the combustion chamber at a distance from the peripheral edge 41 of the hole at a distance from the peripheral edge 41 of the hole. At least 2.0 from 41
mm or more.

A shim plate 3 made of a metal plate such as a stainless steel plate or an iron plate and having a relatively small thickness of, for example, 0.05 to 0.15 mm extends only around the periphery of the combustion chamber hole 4. At the same position as the convex beads 6 of 1 and 2, a convex bead 6 'surrounding the combustion chamber hole 4 is provided. The beads 6, 6 of the substrates 1 and 2 and the bead 6 'of the shim plate 3 are formed at the same position around the combustion chamber hole, protrude in the same direction, have substantially the same shape, and can be overlapped with each other. Is formed. The metal gasket for a cylinder head according to the present invention is formed by laminating the substrates 1 and 2 and the shim plate 3 so as to overlap the beads 6, 6 and 6 '. Is interposed between the substrate 1 and the substrate 2.

The outer and inner surfaces of the substrates 1 and 2 are made of a heat-resistant rubber such as fluoro rubber or silicone resin or synthetic resin, and constitute the surface of the joint surface between the cylinder head and the cylinder block, the substrate and the shim plate. And a sealing material layer 7 functioning as a micro-seal that compensates for irregularities such as scratches, surface roughness, and distortion on the surface of the metal plate. Normally, the thickness of the sealing material layer is 15 to 40 μm on the outer surface in contact with the joining surface of the cylinder head or the cylinder block,
The inner surface in contact with the shim plate 3 is coated to 5 to 25 μm.

When the metal gasket for a cylinder head according to the present invention having the structure described above is mounted between the cylinder head H and the cylinder block B and the gasket is tightened, the thickness of the gasket is adjusted by the shim plate 3. The surface pressure is increased around the thickened combustion chamber hole 4, and the convex beads 6 and 6 of the substrates 1 and 2 and the convex beads 6 'of the shim plate 3 are overlapped as shown in FIG. A seal line having a high surface pressure is obtained at the top E1 and the leg E2 of the bead portion. However, in FIG. 5, in order to clarify the positional relationship, the cross-sectional shape of the gasket is shown in the state of being tightened. Unlike the conventional gasket shown in FIG. 6, a high surface pressure is not distributed between the folded portion 15 and the bead 14, so that a higher sealing surface pressure can be obtained and the sealing ability can be increased. Moreover, in the gasket according to the present invention, since there is no high surface pressure portion immediately around the periphery of the combustion chamber hole, deformation of the combustion chamber is reduced.

FIG. 3 shows another embodiment of the present invention.
It is an expanded sectional view similar to. However, in FIG. 3, the respective plates constituting the gasket are shown in a spaced state in order to make the drawing easy to understand. 1 and 2 denote the same parts. In the embodiment of FIG. 3, the sealing material layers 71 and 71 covering the concave portions 61 and 61 of the convex beads 6 and 6 of the substrates 1 and 2 are thicker than the sealing material layer 7 of the other portions.

The thickness of the sealing material layer 7 covering the inner surface 12 of the substrate 1 is usually 5 to 25 μm as described above.
Is a thick coating having a thickness of, for example, 30 to 50 μm. The thickness of the sealing material layer 7 covering the outer surface 21 of the substrate 2 is usually 15 to 40 μm as described above.
The sealing material layer 71 in the concave portion 61 of the
It is coated with a thick wall of 0 to 50 μm. The gasket of the embodiment shown in FIG. 3 is the same as the embodiment shown in FIGS. 1 and 2 except for the above points.

As described above, in the embodiment shown in FIG. 3, the sealing material layer 7 of the concave portions 61 of the beads of the substrates 1 and 2 is formed.
Since the gaskets 1 and 71 are thickly coated, the thickness of the gasket in the bead portion where the beads 6 and 6 of the substrates 1 and 2 and the bead 6 'of the shim plate are superimposed increases by that much, and the gasket is moved to the cylinder. The surface pressure of the bead portion when mounted and tightened between the head and the cylinder block increases accordingly. Furthermore, the thick sealing material layer 7 of the concave portion 61 of the bead.
By making the thickness of the portion apart from the bolt hole in 1 larger than the thickness of the portion close to the bolt hole, for example, the thickness of the portion close to the bolt hole is 30 to 50 as described above.
μm, and the thickness of the part
By setting the thickness to 70 μm, the sealing surface pressure around the combustion chamber hole can be equalized, and the sealing performance can be improved.

In each of the embodiments shown in FIGS. 1 and 2, and the embodiment shown in FIG.
Use independent annular shim plates.
As shown in the plan view, the use of the connection shim plates 3 'connected in parallel by the connection portions 31 between the combustion chamber holes 4 is advantageous for gasket assembly. In the connection shim plate 3 ′ shown in FIG. 4, each convex bead 6 ′ around each combustion chamber hole 4 is provided independently.
It may be connected between them. In the gasket illustrated and described above, the convex beads 6 and 6 'protrude upward in the drawing (cylinder head side), but may protrude downward in the drawing (cylinder block side). It is.

[0018]

The metal gasket for a cylinder head according to the present invention described above has the following remarkable effects. A shim plate made of a thin metal plate is sandwiched between substrates made of a thick metal plate, and is present only around the combustion chamber hole. There is no danger of deforming or displacing and causing gas leakage or gasket damage. Since the convex bead of the two-layer substrate and the shim plate protrudes and overlaps in the same direction, and the folded portion does not exist, the surface pressure is concentrated only on the convex bead when the gasket is tightened. A very high surface pressure sealing line is obtained around the chamber, and the sealing ability is large. When the gasket is tightened, the deformation of the combustion chamber is reduced because there is no high surface pressure portion immediately around the combustion chamber hole. Since the thickness of the gasket around the hole for the combustion chamber is adjusted by the shim plate, the thickness can be finely adjusted as compared with the conventional gasket having the folded portion.

[Brief description of the drawings]

FIG. 1 is a plan view of a gasket according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view taken along line AA of FIG.

FIG. 3 is a sectional view similar to FIG. 2 of another embodiment of the present invention.

FIG. 4 is a plan view of a connection shim plate used for the gasket of the present invention.

FIG. 5 is an explanatory diagram of a surface pressure distribution when the gasket of the present invention is tightened between a cylinder head and a cylinder block.

FIG. 6 is an explanatory diagram illustrating a cross section and a surface pressure distribution of a conventional gasket.

[Explanation of symbols]

 1, 2 substrate 3 shim plate 4 hole for combustion chamber 6, 6 'convex bead 7 sealing material layer

Claims (4)

[Claims] 1. A two-layer substrate comprising a thick elastic metal plate, extending over substantially the entire joint surface between a cylinder head and a cylinder block, and including a convex bead surrounding a combustion chamber hole; A shim plate comprising a thin metal plate having a convex bead extending only around the periphery of the combustion chamber hole and surrounding the periphery of the combustion chamber hole, wherein the two-layer substrate and the shim plate The convex beads project in the same direction and are formed in substantially the same shape at the same position so that they can be overlapped with each other. The two-layer substrate is provided with a shim plate interposed at the periphery of each combustion chamber hole. A metal gasket for a cylinder head, which is superposed. 2. A metal gasket for a cylinder head according to claim 1, wherein shims extending around adjacent combustion chamber holes are connected to each other. 3. The metal gasket for a cylinder head according to claim 1, wherein the thickness of the sealing material layer covering the concave portion of the bead of the substrate is larger than the thickness of the sealing material layer in other portions. 4. The metal gasket for a cylinder head according to claim 3, wherein a thickness of a portion of the sealing material layer covering the concave portion, which is separated from the bolt hole, is larger than a thickness of a portion close to the bolt hole. .