JPH0483975A - Metallic gasket - Google Patents

Abstract

PURPOSE:To prevent the damage of a joint face due to a bead and to ensure stable sealing ability on the whole of a metallic gasket by increasing the thickness of a seal film on the surface on the protrusion part side of a bead to a value higher than that of a seal film on the surface on the recessed part side of the bead. CONSTITUTION:First seal films 16a and 16b of a vulcanized rubber layer formed of vulcanized fluorine rubber are formed on both surfaces of a base plate 10. The first seal films 16a and 16b are a seal film adhered on the surface on the protrusion part 15a side of a bead 15 and the surface on the recessed part 15b side thereof, and a thickness t1a of the surface on the protrusion part 15a side of the bead 15 is increased to a value higher than a thickness t1a of the back thereof. Second seal films 17a and 17b of a non-vulcanized or unvulcanized rubber layer formed on both surfaces of the base plate 10 are adhered to the first seal films 16a and 16b, respectively. A thickness t2a of the surface on the protrusion part 15a side of the bead 15 of the second seal films 17a and 17b is increased to a value higher than a thickness t2b of the back thereof. This constitution prevents the top surface of the protrusion part of the bead from being exposed to damage a joint face and ensures stable sealing ability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a metal gasket, and particularly to a metal gasket suitable as a cylinder head gasket, an exhaust manifold gasket, etc. of an internal combustion engine.

[Prior Art] It is well known that gaskets are interposed between joint members to prevent pressure fluid from leaking from joint surfaces. For example, a cylinder head gasket interposed between a cylinder head and a cylinder block of an internal combustion engine is required to simultaneously seal combustion gas, cooling water, and lubricating oil. Especially for combustion gas, high temperature,
Sealing is difficult not only because of the high pressure but also because of the large temperature and pressure changes. For this reason, various gaskets have been proposed, and recently, metal gaskets made of metal plates, ie, metal gaskets, have been attracting attention. Specifically, multiple holes are drilled in a metal substrate through which pressurized fluid such as combustion gas passes, and a bead is formed in the substrate around each hole to ensure high surface pressure against the bonding members. This is what I did to get it.

When the above-mentioned metal gasket is interposed between joining members such as a cylinder head or a cylinder block, and the two are fastened together with a predetermined tightening force, the bead is compressively deformed and its elastic restoring force forces it into a predetermined surface against the joining member. pressure is obtained. At this time, in order to prevent the joint surfaces of the joint members from being damaged by beads, for example, in the metal gasket described in Japanese Utility Model Application Publication No. 61-41960, a vulcanized first coating layer is applied to the substrate surface, and A soft, non-vulcanized second coating layer is applied to compensate for the irregularities of the joint surfaces.

Similarly, Japanese Utility Model Application Laid-Open No. 64-8556 also discloses a cylinder rad gasket in which a micro sealing material is applied to the entire surface of a substrate to cover beads and the like.

[Problems to be Solved by the Invention] In the gaskets described in the above-mentioned publications, a predetermined surface pressure against the joint surface is ensured by the elastic restoring force of the bead, and stress is not applied to the top surface of the convex portion of the bead. You will have to concentrate. Therefore, if a sealing film such as a paint layer or a micro sealing material attached to the top surface of the convex portion of the bead flows and the substrate is exposed, the sealing function of this portion will be degraded. This becomes noticeable in a metal gasket interposed between joining members having different coefficients of thermal expansion, such as between a cylinder head made of an aluminum alloy and a cylinder block made of cast iron. In order to prevent such a situation, it is possible to increase the thickness of the sealing film, but if the thickness of the sealing film on both sides of the board becomes large, the tightening force when connecting the joining members or the combustion gas, etc. The sealing film in the above portion flows due to a temperature change in the fluid to be sealed, causing a decrease in the fastening force between the joining members. Jitsukai 61-41
960 describes that it is possible to provide a sealing film on one side of the substrate, for example, only on the upper surface of the cylinder head, but this imposes limitations on the fluid to be sealed, the material of the joining member, etc.

Therefore, in order to ensure the desired sealing function in a gasket interposed between joining members having different coefficients of thermal expansion as mentioned above, it is desirable to provide a sealing film on both sides of the substrate. If the thickness is increased, new problems will arise as described above.

Therefore, an object of the present invention is to prevent damage to the bonding surface due to beads and to ensure stable sealing performance of the metal gasket as a whole, without causing a decrease in fastening force due to an increase in the thickness of the sealing film. .

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a metal gasket in which beads are formed on a metal substrate and sealing films are attached to both surfaces of the substrate including the beads. The thickness of the sealing film on the surface of the bead on the convex side is made larger than the thickness of the sealing film on the surface of the bead on the concave side.

Therefore, the present invention provides a metal substrate with a hole through which a pressurized fluid passes, a bead around the hole, and a thickness that has a sealing property over the entire circumference of the hole on the inner peripheral side of the bead. In a metal gasket in which a thick part is provided and a sealing film is attached to both sides of the substrate including the thick part and the bead, the thickness of the sealing film on the surface on the convex part side of the bead is equal to the thickness of the sealing film on the surface on the concave part side of the bead. Including those that are larger than the thickness of the seal membrane on the surface.

The seal film has two layers: a first seal film, which is a vulcanized rubber layer that adheres to the substrate, and a second seal film, which is an unvulcanized or unvulcanized rubber layer that adheres to the first seal film. It is better to use a structure.

[Operation] When the metal gasket having the above structure is interposed between opposing joining members, for example between a cylinder head and a cylinder block, and the two are fastened with a predetermined tightening force, the bead is compressed. and transform.

The elastic restoring force of this compressively deformed bead provides a predetermined surface pressure against the joining member. In this case, sealing films are attached to both sides of the substrate, and the thickness of the sealing film on the surface on the convex side of the bead is larger than the thickness of the sealing film on the surface on the concave side. Even if a difference in thermal expansion occurs between the two, the substrate on the top surface of the convex portion of the bead that is pressed against the bonding surface will not be exposed. Therefore, a predetermined sealing function is ensured without damaging the joint surfaces.

[Example] Hereinafter, an example of the metal gasket of the present invention will be described with reference to FIGS. 1 and 2. This embodiment relates to a metal gasket applied to a cylinder rad gasket interposed between a cylinder head and a cylinder block of a multi-cylinder internal combustion engine (not shown).

In FIG. 2, the metal gasket 1 has a base plate 10 made of an elastic metal plate, for example, a stainless steel plate, in which a combustion chamber hole 11 and the like are bored and a bead 15 is formed. A plurality of cooling water holes 12 and a lubricating oil hole 13 are formed in the substrate 10, and a plurality of bolt holes 14 are formed around the combustion chamber hole 11 at substantially equal intervals. In this embodiment, the bead 15 is arranged such that the convex portion 15a is on the cylinder block side and the concave portion 15b is on the cylinder head side. Although not shown, it is possible to form an inclined portion so as to surround the bolt hole 14 and the lubricating oil hole 13 of the substrate 10, and also to form an inclined portion on the outer edge of the substrate 10 so as to surround all the holes. Preferably, these sloped portions correspond to the sloped portions on one side of the bead 15 and are therefore referred to as half beads. Further, the substrate 10 from the bead 15 to the combustion chamber hole 11 has a flat open end 10a.
A thick portion may be formed on the surface of the opening end 10a on the side of the convex portion 15a of the bead 15. For example, an annular stainless steel plate spacer (not shown),
It is also possible to fix a so-called shim ring.

As shown in the cross-sectional view of FIG. 1, first seal films 16a and 16b of vulcanized rubber layers made of vulcanized fluorocarbon rubber are formed on both surfaces of the substrate 10. This first seal [16a, 16b is a sealing film attached to the surface of the bead 15 on the convex portion 15a side and the surface on the concave portion 15b side, respectively, and the thickness tla of the surface of the bead 15 on the convex portion 15a side is the same. It is larger than the thickness tlb of the back surface. For example, the thickness tla is set to 10 μm and the thickness tlb is set to 7 μm. Furthermore, in order to ensure the sealing performance of the misaligned joint surfaces during contact with the cylinder block and cylinder head, second sealing films 17a, 17 of unvulcanized or unvulcanized rubber layers are provided on both surfaces of the substrate 10.
b are attached to the first seals 1ij16a, 16b, respectively. Here, unvulcanized rubber refers to rubber that does not contain a vulcanizing agent, and unvulcanized rubber refers to rubber that contains a vulcanizing agent but has not been subjected to vulcanization treatment. Although unvulcanized rubber initially has the same initial sealing properties as unvulcanized rubber, it is preferable to use unvulcanized rubber because vulcanization progresses during use and a strong rubber layer is formed. The thickness t2a of the surface of the second seal 1i17a, 17b on the convex portion 15a side of the bead 15 is also smaller than the thickness t2b of the back surface thereof. For example, the thickness t2a is 10 μm and the thickness t2b is 8 μm.
is set to .

Note that the first seal films 16a and 16b are formed by continuously flowing liquid, unvulcanized fluorocarbon rubber to form a film-like flowing lower surface, and one side of the substrate 10 is placed on this film-like flowing lower surface. It can be deposited on both sides of the substrate 10 by passing it upward, passing it again with the other side facing upward, and then heating and vulcanizing it at a predetermined temperature. Furthermore, unvulcanized or unvulcanized fluororubber is first treated in the same manner as above.
The second seals [17a, 17b] can be formed by depositing the second seals [17a, 17b] on the seal films 16a, 16b.

The metal gasket 1 having the above structure is interposed between a cylinder head and a cylinder block (not shown), and when a fastening force is applied between them, the convex portion 15a of the beat 15 first comes into contact with the joint surface of the cylinder block and deforms. However, due to its elastic restoring force, it comes into close contact with both. At this time,
First sealing film 16a on the surface of the bead 15 on the convex portion 15a side
and the thickness of the second seal film 17a are the same as those of the recess 15.
First seal [16b and second seal film 1 on side b side]
7b, the substrate 10 is prevented from being exposed even if stress is concentrated on the convex portion 15a and the first and second seal films 16a, 17a slightly flow.
It will not damage the joint surfaces. Thus, stable sealing performance is ensured. In addition, when applying unvulcanized rubber to the second seal film, in order to ensure initial sealing performance against the roughness of the other material, the second seal @ 17 is lower than the first seal film 16b.
It is desirable to make b thick.

In the above-described embodiment, the metal gasket 1 is arranged so that the convex part 15a of the bead 15 is on the cylinder block side, but it can be turned upside down and arranged so that the convex part 15a is on the cylinder head side. You can also use it as Also,
It is also possible to apply a metal gasket having the same configuration as above to the exhaust manifold gasket.

[Effects of the Invention] Since the present invention is configured as described above, it produces the effects described below.

That is, in the metal gasket of the present invention, the thickness of the seal film attached to the surface of the convex portion of the bead formed on the substrate is greater than the thickness of the seal film adhered to the surface of the bead on the concave portion side. Therefore, the substrate on the top surface of the convex portion of the bead is not exposed and the bonding surface is not damaged, and stable sealing performance can be ensured.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a part of a metal gasket according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along line II in FIG. 2, and FIG. 2 is a bottom view of a part of the metal gasket. . 16a, 16b...first seal membrane. 17a, 17b --- Second seal film

Claims (1)

[Claims] (1) In a metal gasket in which a bead is formed on a metal substrate and a sealing film is attached to both sides of the substrate including the bead, the thickness of the sealing film on the surface of the bead on the convex side is A metal gasket characterized in that the thickness of the sealing film on the concave side surface is larger than that of the sealing film.