Seal for a joint or juncture – Seal between fixed parts or static contact against... – Contact seal between parts of internal combustion engine
Reexamination Certificate
2001-11-28
2004-03-09
Knight, Anthony (Department: 3676)
Seal for a joint or juncture
Seal between fixed parts or static contact against...
Contact seal between parts of internal combustion engine
C277S591000, C277S597000
Reexamination Certificate
active
06702297
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a metal gasket for use in an engine with a chain case and more particularly, relates to a metal gasket for sealing a three-surface joining portion defined by a cylinder head extended along the chain case, a cylinder block and the chain case in the engine with the chain case.
BACKGROUND OF THE INVENTION
It is common for an engine with a chain case to have by nature a stepped part on an upper end face of a cylinder block and the chain case in a three-surface joining portion defined by a cylinder head, the cylinder block and the chain case, and in most cases, this stepped part expands due to a difference in thermal expansion associated with the operation of the engine. To seal this three-surface joining portion, foamed cellular elastic material such as foam rubber in particular finds increased use as a sealing component. The reason is as follows. Compared to ordinary rubber, this foam rubber has self-compressibility and flexible compressibility and also has great flexibility with respect to external force. With the use of this flexibility, the foam rubber can find application to a gasket having a reduced tightening thickness.
Known prior techniques for such a metal gasket sealing the three-surface joining portion are as follows.
(1) As disclosed in Japanese Unexamined Patent Publication No. 7-133870 (1995), a seal member having foamed cellular and elastic materials and a metal core interposed between these materials is provided to an area corresponding to the three-surface joining portion.
(2) As disclosed in Japanese Utility Model Registration No. 2,597,677 (see FIG.
11
), auxiliary plate (adjusting plate)
51
serving as one constitutive metal plate is extended along the chain case to be formed with chain case hole
52
, and both sides of plate
51
are covered with respective closed-cell expanded sealing members
53
,
53
covering their respective entire regions surrounding this hole
52
. It is to be noted that an element denoted by reference number
54
in the drawing is a main plate (bead plate).
(3) As disclosed in Japanese Unexamined Utility Model Publication No. 63-48059 (1988) or Japanese Unexamined Patent Publication No. 7-119836 (1995), one constitutive metal plate is extended along the chain case to be formed with a chain case hole and is provided with a soft sheet covering the entire region of its either side or each side that surrounds this hole.
(4) As disclosed in Japanese Unexamined Patent Publication No. 10-292865 (1998), constitutive plates are all extended along the chain case, the surface of the constitutive metal plate that faces the three-surface joining portion is formed with a full bead, and a recessed part of this full bead is filled with elastic material.
One problem associated with the sealing of the three-surface joining portion is that oil is likely to leak when turned into mist at high temperatures. Such leakage is most likely to occur at a point where a leakage passage becomes widest as a result of the expansion of the stepped part of the three-surface joining portion at the start from low temperatures. The expansion of the stepped part is caused by a difference in thermal expansion between an aluminum chain case and a cast-iron cylinder block that is associated with cooling and heating.
With the above-described conventional examples, the seal members of which are made of foam rubber or the like and are each provided to only the area corresponding to the three-surface joining portion, a clearance is likely to appear between the seal member and the constitutive plate of the gasket in the vicinity of a mounting part for the seal member, and if the above-described expansion of the stepped part takes place, complete sealing with a high degree of reliability cannot be accomplished.
The foam rubber itself has the advantageous properties mentioned earlier. However, in cases where foam rubber having a high expansion ratio in particular is used as an elemental sheet, shape stability and durability of this foam rubber become poor, so that the above-mentioned advantages and these disadvantages are two sides of the coin. In other words, the foam rubber is susceptible to fracture resulting from strain, deformation or flow caused by external force and hence cannot secure stable surface pressure over a long period. For this reason, the elemental sheet of foam rubber is unfit for use as a relatively large seal member, and the above-described conventional techniques each using this elemental sheet, under 100-150° C. atmosphere, as a seal member, which requires long-lasting reliability and durability, for the chain case are mostly impracticable.
The present invention addresses the problems discussed above and aims to provide a metal gasket for use in an engine with a chain case, the metal gasket having excellent long-lasting reliability and excellent durability and using a foam-rubber seal member shaped to withstand in practical use.
SUMMARY OF THE INVENTION
To accomplish the above-described object, a metal gasket for use in an engine with a chain case in accordance with a first aspect of the invention comprises:
at least two constitutive plates forming a total constitutive plate comprising:
an extended part for each of the plates extended along the chain case; and
a chain case hole for each of the plates formed in the extended part; and
a foam-rubber seal member, mounted to a surface of the extended part for one of constitutive plates that faces the chain case, for sealing a chain case opening and a three-surface joining portion defined by the chain case, a cylinder block and a cylinder head,
wherein the foam-rubber seal member is a separate and distinct member and is a sheet-like and loop-like combination of layers of foam rubber and a metal core plate interposed between the layers of foam rubber, and the metal core plate is distinct from the constitutive plates.
According to the present invention, sealability at an edge of the chain case opening can be secured because the foam-rubber seal member having self-compressibility, flexible compressibility and great flexibility forms a seal loop along the edge of the chain case opening with covering all over the sealing surface of the chain case opening and the three-surface joining portion defined by the chain case, the cylinder block and the cylinder head. In addition, the foam-rubber seal member is reinforced by having the metal core plate between the layers of foam rubber, thereby obtaining stabilized shape, excellent long-lasting reliability and excellent durability compared to the elemental sheet used as the foam-rubber seal member.
In the present invention, one of the constitutive plates is preferably a bead plate disposed next to the cylinder head, and the foam-rubber seal member is preferably mounted to the extended part of this bead plate. Here, this bead plate may be made of any material selected appropriately, provided that it is an elastic metal plate, and the thickness of this bead plate may also be selected appropriately.
A metal gasket for use in an engine with a chain case in accordance with a second aspect of the present invention comprises:
a first bead plate disposed next to a cylinder head;
a second bead plate disposed next to a cylinder block;
at least one intermediate constitutive plate interposed between the first and second bead plates, the first and second bead plates and the intermediate plate forming a total constitutive plate comprising:
an extended part for each of the plates extended along the chain case; and
a chain case hole for each of the plates formed in the extended part; and
a foam-rubber seal member, mounted to a surface of the extended part of the first bead plate that faces the chain case, for sealing a chain case opening and a three-surface joining portion defined by the chain case, the cylinder block and the cylinder head,
wherein the first bead plate comprises, in the extended part, a small chain-case hole partially defined by a retainer which overhangs the chain case and is opposed to the chain case opening, and a hal
Furuta Yutaka
Ogaeri Tomoyoshi
Uemura Hiroshi
Armstrong Teasdale LLP
Boswell Christopher J.
Knight Anthony
Nippon Gasket Company Ltd.
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