Seal for a joint or juncture – Seal between fixed parts or static contact against... – Contact seal between parts of internal combustion engine
Reexamination Certificate
2001-03-07
2003-01-07
Sandy, Robert J. (Department: 3676)
Seal for a joint or juncture
Seal between fixed parts or static contact against...
Contact seal between parts of internal combustion engine
C277S598000
Reexamination Certificate
active
06502829
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a construction for squeezing a gasket disposed between confronting surfaces of engine components, for example cylinder heads, cylinder blocks and others by a clamping force that results from the tightening of fastening bolts.
2. Description of the Prior Art
With metal gaskets, multi-layer gaskets are conventionally known in public, which are used placed between engine parts such as cylinder blocks, cylinder heads, and so on of automotive engines. An exemplification of the metal gaskets is disclosed in, for example, Japanese Patent Laid-Open No. 39868/1993.
A prior metal gasket
20
shown in
FIGS. 4 and 5
is comprised of a pair of bead sheets
21
,
22
of stainless steel overlaid one on the other, each of which is made with beads
23
,
24
extending around holes
25
formed in alignment with cylinder bores. The metal gasket
20
is a head gasket designed for multi-cylinder engine, and thus the bead sheets
21
,
22
are each provided therein with holes
25
arranged juxtaposed in conformation with cylinder bores in the cylinder block of the engine. The bead sheets
21
,
22
are also made with bolt holes
26
through which head bolts extend to clamp together the cylinder head and the cylinder block, and other holes for coolant, oil, and so on.
The bead sheets
21
,
22
of the metal gasket
20
, as shown in
FIG. 5
, are made with the beads
23
,
24
of full bead type, which are raised above any one face thereof towards each other so as to make line abutment against each other at the beads in a cross section taken on the plane joining the centers of any adjacent holes
25
. Moreover, any one dead sheets, or bead sheet
22
has a flange
22
formed by folding back the bead sheet itself at a return defining the associated hole
25
to be overlaid on the major surface of the bead sheet, with extending radially to the extent of not having to interfere with the associated bead
24
. Although but leach bead
23
,
24
is formed independently of one another at an area between any two adjacent holes
25
, it will be appreciated that the adjoining beads
23
,
24
may be made to merge into a single bead. Moreover, it is well-known that the modification in width and/or height of the beads
23
,
24
and in thickness and/or width of the flanges
27
results in the increase of compressive sealing stress when tightened, at the area between the adjacent holes
25
, which extends over an angle a shown in FIG.
4
.
When tightening the head bolts to squeeze the metal gasket
20
placed between the confronting surfaces of the engine components, the beads
23
,
24
generates, in combination with the flange
27
folded back to serve increasing the sheet thickness, a dual annular sealing construction of high compressive sealing stress around the associated hole
25
. The dual annular sealing construction prevents leakage combustion gases through the joint between the mating surfaces of the engine components.
In the meantime the head gasket has areas where the gasket is jointed together with the cylinder head, or bolt holes
26
in which the head bolts are installed to tighten together the cylinder head and the cylinder block. As seen from
FIG. 4
, the bolt holes
26
are arranged in only the perimetral area of the metal gasket
20
due to spatial design restrictions and further, not all the bolt holes
26
are uniformly disposed around the holes at areas where the sealing effects are need locally. Moreover, the compressive sealing stress desired in the head gasket
20
differs in magnitude between a first sealing stress level needed at areas around the holes
25
and a second sealing stress desired neighboring the coolant holes and oil holes. It will be understood that the first sealing stress is set higher than the second sealing stress.
To keep the compressive sealing stress higher around the cylinder holes in the head gaskets such as multi-layer gaskets, composite gaskets, and so on, various measures in the gasket construction have been taken, in which the metallic sheet is increased in thickness only areas surrounding around the cylinder bores or the beads around the cylinder bores are made greater in height than the beads around the coolant holes, oil holes and others. The desired compressive sealing stress around the cylinder holes is established by the tightening of the head bolts, which are mostly remote from the cylinder holes. Thus, the much tightening of the head bolts is needed to ensure the sufficiently high sealing stress at the areas around the cylinder holes. This becomes a major problem in which continued bolt tightening might cause deformation of the cylinder block and the cylinder head at or near the fastening bolts.
As a result, although the sealing stress becomes high at the areas around the cylinder holes nearby the head bolts tightened, other areas far spaced away from the tightened head bolts, as illustrated with somewhat exaggeration in
FIG. 6
, might experience deformation in both the cylinder block and the cylinder head, in which the mating surfaces
4
,
5
are subjected to warp towards opposite directions, whereby the cylinder block
3
and the cylinder head
2
are made spaced apart away from each other at the region between the adjoining head bolts. This results in failure of ensuring the desired sealing stress around the cylinder holes neighboring the region where the mating surfaces are made spaced away from each other. Even if the head bolts more continue tightening to increase the squeeze-torque for ensuring the desired sealing stress, the satisfactory head-to-block sealing is no longer established at, especially, the area between any two adjacent cylinder holes because the warp occurring between the cylinder head
2
and the cylinder block
3
is much more enlarged, so that it becomes very tough to realize well the desired sealing stress at the sealing areas with good balance.
To cope with the event stated earlier, many modifications are required such that the folded flange of the gasket is further made varied in thickness and/or radial width locally around the associated cylinder hole, the beads are changed in height and/or width, and each metallic sheet itself is varied in thickness. These modifications make the construction of the gasket complicated, thus coming to have a strong tendency to repeat a vicious spiral introducing much trouble in effort and cost on every aspect.
The disadvantageous phenomenon of the vicious relation between the gasket construction and the sealing stress on the sealing areas is apt to become much more remarkable in all aluminum-made engine of open deck type.
The metal gaskets for the current engines are involved inherently with the antinomic subject matter: it is needed to render the spring constant of the bead large to reduce the warp at the mating surfaces by either the use of materials higher in elasticity and/or stiffness or the modification embodied in the gasket construction, while the elastic effect should be regulated such that the sealing stress does not converge on only any local area, but diverges uniformly over the gasket. Nevertheless, the above-mentioned vicious relation between the gasket construction and the sealing stress on the sealing areas is considered a major problem left to solve, compared with the antinomic subject matter described just above.
The problem discussed earlier occurs more or less in other gaskets than the head gaskets, which are adapted disposed between the mating surfaces of the cylinder head and any of the intake and exhaust manifolds.
Thus, it will be worthwhile developing a squeezing construction for a gasket disposed between the confronting surfaces of the engine components such as cylinder head, cylinder block, and so on, in which a clamping force resulting from the tightening of fastening bolts to squeeze together the gasket between the confronting surfaces is made uniform throughout the entire of the gasket while a sealing stress created neighboring bolt holes where the fastening bolts are inse
Sugimoto Kiyoshi
Watanabe Takuya
Yoshijima Kazuya
Browdy and Neimark , P.L.L.C.
Nippon Gasket Co. Ltd.
Patel Vishal
Sandy Robert J.
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