Metal gasket assembly

A metal gasket assembly for a cylinder head includes a pair of elastic metal substrates each having an outer shape which conforms with the outer shape of the gasket assembly, cylinder openings corresponding to cylinders in the cylinder head, a peripheral region surrounding the cylinder opening, which may be greater in thickness than remaining region of the relevant substrate, and a bead in the peripheral region. The substrates are superimposed with each other with top portions of the beads of the substrates in abutment with each other. A by-plate may be arranged between the substrates and has an increased thickness in its peripheral region which surrounds the cylinder opening and which is in direct abutment with the top portions of the beads in the substrates.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a metal gasket assembly for a cylinder 
head of an internal combustion engine. 
2. Description of the Related Art 
Metal gasket assembly comprising primarily of metal material is known and 
disclosed, e.g., in Japanese Patent Application Laid-open Publication No. 
4-165,167. Typically, a metal gasket assembly comprises a pair of 
substrates and a by-plate, each of which is formed of an elastic metal 
sheet, e.g., a stainless steel sheet. The gasket assembly is formed with 
various openings, such as openings for engine cylinders, cooling water 
jackets, lubricating oil passages in the cylinder head, and bolt holes. 
The substrates are provided with beads in the peripheral regions 
surrounding the cylinder openings. The substrates are superimposed with 
the by-plate on its both sides, such that the top portions of the beads on 
the substrates are oriented in opposite directions to protrude outwards. 
The by-plate is comprised of a relatively thick first metal sheet which 
surrounds the cylinder openings with a predetermined width, and a 
relatively thin second metal sheet which forms the remaining region of the 
by-plate and which is simply fitted into the first metal sheet, without 
being welded to each other. 
With a recent trend towards internal combustion engines with higher output, 
there arose a demand for a higher sealing performance of the gasket 
assembly. Therefore, it has been proposed to increase the thickness of the 
metal sheet of the by-plate in the peripheral regions which surround the 
cylinder openings, thereby to realize a higher fastening pressure in the 
regions adjacent to the engine cylinders. 
However, since the top portions of the beads on the substrates protrude 
outwards in mutually opposite directions, the skirts of the beads may 
undergo expansion during fastening of the gasket assembly to disperse the 
fastening pressure and cause dislocation of the skirt of the bead out of 
the peripheral region of the by-plate which surrounds the cylinder 
opening. Moreover, since the two metal sheets forming the by-plate are 
simply fitted to each other, they may undergo a relative displacement upon 
thermal expansion, so as to form a gap and thereby deteriorate the sealing 
performance of the gasket assembly. 
SUMMARY OF THE INVENTION 
It is therefore a primary object of the present invention to provide an 
improved metal gasket assembly which eliminates to at least mitigates the 
abovementioned problems. 
Briefly stated, the present invention provides a metal gasket assembly for 
a cylinder head, which includes a pair of elastic metal substrates each 
having an outer shape which conforms with the outer shape of the gasket 
assembly. Each substrate has at least one cylinder opening corresponding 
to at least one cylinder in the cylinder head, a peripheral region 
surrounding the cylinder opening, and a bead in the peripheral region 
surrounding the cylinder opening. The substrates are superimposed with 
each other with top portions of the beads of the substrates directed 
toward, and in abutment with each other. 
In this instance, the peripheral region of the substrate surrounding the 
cylinder opening may have a thickness which is greater than that of 
remaining region of the relevant substrate. Alternatively, a by-plate may 
be arranged between the substrates and designed to have an increased 
thickness in its peripheral region which surrounds the cylinder opening 
and which is in direct abutment with the top portions of the beads in the 
substrates. 
With the above-mentioned arrangement of the metal gasket assembly according 
to the present invention, the substrates are superimposed with each other 
such that the top portions of the beads in the peripheral region 
surrounding the cylinder opening are directed toward, and brought into 
abutment with each other either directly or with the by-plate 
therebetween. It is thus possible to concentrate the fastening pressure 
and avoid undesirable dislocation of the skirts of the beads out of 
predetermined position. Moreover, when the by-plate is held between the 
substrates, the top portions of the beads are in direct abutment with the 
by-plate at its peripheral region having an increased thickness. It is 
thus possible to realize a further increased fastening pressure in such 
peripheral region. 
According to a preferred embodiment of the present invention wherein the 
metal gasket assembly further comprises a by-plate held between the two 
substrates, the by-plate comprises a relatively thick first metal sheet 
having at least one cylinder opening and surrounding the cylinder opening 
with a predetermined width, and a relatively thin second metal sheet 
having an outer shape which conforms with the outer shape of the gasket 
assembly and forming remaining region of the by-plate, in which the first 
and second metal sheets are fitted and laser-welded to each other. Thus, 
the two metal sheets of the by-plate can be prevented from dislocation 
upon thermal expansion, making it readily possible to realize a further 
improved sealing performance of the gasket assembly. 
According to an alternative embodiment of the present invention wherein 
metal gasket assembly further comprises a by-plate held between the two 
substrates, the by-plate comprises a first metal sheet having at least one 
cylinder opening corresponding to said cylinder in the cylinder head and 
surrounding the cylinder opening with a predetermined width, and a second 
metal sheet having at least one cylinder opening corresponding to the 
cylinder in the cylinder head and an outer shape which conforms with the 
outer shape of the gasket assembly, in which the first and second metal 
sheets are fitted and laser-welded to each other. In this instance also, 
the two metal sheets of the by-plate can be prevented from dislocation 
upon thermal expansion, making it readily possible to realize a further 
improved sealing performance of the gasket assembly. 
According to another preferred embodiment of the present invention, at 
least one of the substrates comprises a relatively thick first metal sheet 
having at least one cylinder opening and surrounding the cylinder opening 
with a predetermined width, and a relatively thin second metal sheet 
having an outer shape which conforms with the outer shape of the gasket 
assembly and forming remaining region of the substrate, in which the first 
and second metal sheets are fitted and laser-welded to each other. 
When the metal gasket assembly according to the present invention is for a 
cylinder block having at least one cooling water jacket, the first and 
second metal sheets of at least one of the substrates or those of the 
by-plate are laser-welded to each other at a location which is close to 
the cooling water jacket in use. This makes it possible to mitigate 
thermal stress or thermal expansion to which the welded portions are 
subjected, by the cooling function of the cooling water jacket in the 
cylinder block. 
According to still another embodiment of the present invention, besides 
first and second substrates, the metal gasket assembly further comprises a 
third substrate formed of an elastic metal and having an outer shape which 
conforms with the outer shape of the gasket assembly, at least one 
cylinder opening corresponding to the cylinder in the cylinder head, a 
peripheral region surrounding the cylinder opening, and a bead in the 
peripheral region, wherein the first and third substrates are superimposed 
with each other with top portions of the beads of the first and third 
substrates oriented in opposite directions. This makes it possible to 
realize a further increased elasticity of the beads.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention will be explained in further detail hereinafter, with 
reference to the accompanying drawings wherein like reference numerals are 
used to denote the same or corresponding elements for the sake of 
simplicity. 
Referring now to FIGS. 1, 2 and 3, there is shown a first embodiment of the 
metal gasket assembly 10 according to the present invention, which 
comprises a pair of substrates 1 and a by-plate 2 held between the 
substrates 1. The substrates 1 and the by-plate 2 may be each made of 
elastic metal sheet, such as stainless steel sheet (SUS 301) or the like. 
The gasket assembly 10 is formed with various openings therein, e.g., 
cylinder openings 4 for engine cylinders, openings 5 for cooling water 
jackets, openings 6 for lubricating oil passages, bolt holes 7, etc. Each 
substrate 1 has full beads 8 of substantially semi-circular cross-section 
(FIG. 3), which are formed in the peripheral regions surrounding the 
cylinder openings 4 in the substrate 1. In FIG. 1, the single-dotted chain 
line 8a represents full bead lines corresponding to the top of the 
semi-circular shape of the full beads 8, and the double-dotted chain line 
11a represents a stepwise half bead line. Reference numeral 12 denotes 
caulking portions where the metal plates superimposed one above the other 
are connected with each other. 
FIG. 3 is a fragmentary sectional view of the gasket metal assembly 10 in 
enlarged scale, taken along the line 3--3 of FIG. 1. In this embodiment, 
the by-plate 2 without the beads is shown as being held between a pair of 
substrates 1 which are formed with the beads 8 in the peripheral regions 
of the cylinder openings 4. The by-plate 2 is comprised of a relatively 
thick metal sheet 2a of a desired outer shape, which circumscribes the 
peripheral regions of the cylinder openings 4 with a predetermined width, 
and a relatively thin metal sheet 2b having an outer shape conforming with 
that of the assembly 10 and forming the remainder of the by-plate 2. The 
metal sheets 2a, 2b are fitted with and integrally connected to each other 
by a laser-welding, as shown at 13, and arranged relative to the 
substrates 1 such that the opposite top portions of the beads 8 in the 
substrates 1 are brought into abutment with the relatively thick metal 
plate 2a. 
In a practically preferred example of the gasket assembly shown in FIGS. 1 
to 3, the substrate 1 has a thickness of 0.25 mm, the metal sheet 2a 
circumscribing the peripheral regions of the cylinder openings 4 has a 
thickness of 0.3 mm, and the metal sheet 2b forming the remainder of the 
by-plate 2 has a thickness of 0.2 mm. 
In the first embodiment explained above, the thickness of the metal sheet 
2a of the by-plate 2 circumscribing the peripheral regions of the cylinder 
openings 4 is larger than that of the metal sheet 2b forming the remainder 
of the by-plate 2, so that the fastening pressure at the relatively thick 
metal sheet 2a becomes the highest. Moreover, the beads 8 of the 
substrates 1 are arranged so that the top portions of the beads 8 contact 
with the metal sheet 2a of the by-plate 2 and the metal sheet 2a is held 
between the beads 8 of the substrates 1. Therefore, the fastening pressure 
is concentrated on the top portions of the beads 8 during the fastening, 
thereby to prevent escapement or dislocation of the skirt of each bead 8. 
Furthermore, the relatively thick metal sheet 2a and the relatively thin 
metal sheet 2b are integrally and tightly connected to each other by the 
laser-welding 13, so that the metal sheets when subjected to a thermal 
expansion do not undergo a relative dislocation and thus provide an 
improved sealing performance due the absence of a gap between the metal 
sheets 2a, 2b. 
FIG. 4 shows the second embodiment of the metal gasket assembly according 
to the present invention. In this case, the gasket assembly includes a 
pair of substrates 1 which are essentially same as those of the previous 
embodiment, and a by-plate 2 which is held between the substrates 1. The 
by-plate 2 is comprised of a first metal sheet 2c of a desired outer 
shape, which circumscribes the peripheral regions of the cylinder openings 
4 with a predetermined width, and a second metal sheet 2d having an outer 
shape conforming with that of the assembly, which also circumscribes the 
peripheral regions of the cylinder openings 4. The first and second metal 
sheets 2c, 2d are superimposed with, and integrally connected to each 
other by a laser-welding, as shown at 13, and arranged relative to the 
substrates 1 such that the opposite top portions of the beads 8 in the 
substrates 1 are brought into abutment with the by-plate 2. 
In a practically preferred example of the gasket assembly shown in FIG. 4, 
the substrate 1 has a thickness of 0.25 mm, the first metal sheet 2c has a 
thickness of 0.2 mm, and the second metal sheet 2b has a thickness of 
0.1-0.15 mm. 
In the second embodiment explained above, by superimposing the first and 
second metal sheets 2a, 2b, the by-plate 2 in the peripheral region of the 
cylinder openings 4 has a thickness which is larger than that of the 
remaining region thereof, so that the fastening pressure at the peripheral 
region becomes the highest. Moreover, the beads 8 of the substrates 1 are 
arranged so that the top portions of the beads 8 contact with the metal 
sheet 2a of the by-plate 2 and the metal sheet 2a is held between the 
beads 8 of the substrates 1. Therefore, the fastening pressure is 
concentrated on the top portions of the beads 8 during the fastening, 
thereby to prevent escapement of the skirt of each bead 8. Furthermore, 
the by-plate 2 is comprised of the first and second metal sheets 2c, 2d 
which are laser-welded to each other, and thus provides an improved 
sealing performance due the absence of a gap at the stepped shoulder where 
the metal sheets 2c, 2d are superimposed with each other. 
FIG. 5 shows the third embodiment of the metal gasket assembly according to 
the present invention. In this case, the gasket assembly includes a pair 
of substrates 1A, 1B provided with opposite beads 8 and having an outer 
shape which conforms with that of the gasket assembly. One of the 
substrates, e.g., the substrate 1A on the lower side, is comprised of a 
relatively thick metal sheet la provided with the bead 8, which forms the 
peripheral region of the substrate 1A and circumscribes the cylinder 
openings 4 with a predetermined width, and a relatively thin metal sheet 
1b which forms the remaining region of the substrate 1A. The metal sheets 
1a, 1b are fitted with and integrally connected to each other by a 
laser-welding, as shown at 13. The other substrate 1B may be essentially 
same as the substrate 1 shown in FIG. 3 or 4. The two substrates 1A, 1B 
are arranged relative to each other such that the opposite top portions of 
the beads 8 of the substrates 1A, 1B are in direct abutment with each 
other. 
In a practically preferred example of the gasket assembly shown in FIG. 5, 
the relatively thick metal sheet 1a of the substrate 1A and the substrate 
1B have a thickness of 0.25-0.30 mm, and the relatively thin metal sheet 
1b of the substrate 1A has a thickness of 0.15-0.2 mm. 
In the third embodiment explained above, the thickness of the elastic metal 
sheet 1a for the peripheral region of the substrate 1A is larger than that 
of the metal sheet 1b for the remaining region of the substrate 1A, so 
that the fastening pressure at the peripheral region becomes the highest. 
Moreover, the beads 8 of the substrates 1A, 1B are arranged so that the 
top portions of the beads 8 with each other. Therefore, the fastening 
pressure is concentrated on the top portions of the beads 8 during the 
fastening, thereby to prevent escapement of the skirt of each bead 8. 
Furthermore, the substrate 1A is comprised of the two metal sheets 1a, 1b 
which are laser-welded to each other, so that the metal sheets when 
subjected to a thermal expansion do not undergo a relative dislocation and 
thus provide an improved sealing performance due the absence of a gap 
between the metal sheets 1a, 1b. 
FIG. 6 shows the fourth embodiment of the metal gasket assembly according 
to the present invention. In this case, the gasket assembly includes a 
pair of substrates 1A, 1C which are essentially same as the substrate 1A 
of the third embodiment. Thus, each substrate 1A, 1C is provided with the 
bead 8 and has an outer shape which conforms with that of the gasket 
assembly. Further, each substrate 1A, 1C is comprised of a relatively 
thick metal sheet 1a provided with the bead 8, which forms the peripheral 
region of the substrate and circumscribes the cylinder openings 4 with a 
predetermined width, and a relatively thin metal sheet 1b which forms the 
remaining region of the substrate 1A. The metal sheets 1a, 1b are fitted 
with and integrally connected to each other by a laser-welding, as shown 
at 13. The two substrates 1A, 1C are arranged relative to each other such 
that the top portions of the beads 8 of the substrates 1A, 1B are opposite 
to, and in direct abutment with each other. 
In a practically preferred example of the gasket assembly shown in FIG. 6, 
the relatively thick metal sheets 1a of the substrates 1A, 1C have a 
thickness of 0.25-0.30 mm, and the relatively thin metal sheets 1b of the 
substrates 1A, 1C have a thickness of 0.15-0.2 mm. 
In the fourth embodiment explained above, the substrate 1B of a constant 
thickness in the third embodiment is substituted by the substrate 1C which 
includes a relatively thick metal sheet 1a in the peripheral region which 
circumscribes the cylinder openings 4. Since the metal sheet 1a in the 
peripheral region has a thickness which is larger than that of the metal 
sheet 1b for the remaining regions of the substrates 1A, 1C, the fastening 
pressure at the peripheral regions becomes the highest. Moreover, the 
beads 8 of the substrates 1A, 1C are arranged so that the top portions of 
the beads 8 with each other. Therefore, the fastening pressure is 
concentrated on the top portions of the beads 8 during the fastening, 
thereby to prevent escapement of the skirt of each bead 8. Furthermore, 
each substrate 1A, 1C is comprised of the two metal sheets 1a, 1b which 
are laser-welded to each other, so that the metal sheets when subjected to 
a thermal expansion do not undergo a relative dislocation and thus provide 
an improved sealing performance due the absence of a gap between the metal 
sheets 1a, 1b. 
FIG. 7 shows the fifth embodiment of the metal gasket assembly according to 
the present invention. In this case, the gasket assembly includes three 
substrates 1A, 1B and 1D each having an outer shape which conforms with 
that of the gasket assembly and provided with a bead 8 in the peripheral 
region which circumscribes the cylinder opening 4. The arrangement of the 
first and second substrates 1A, 1B is essentially same as that of the 
third embodiment shown in FIG. 5. Thus, the first substrate 1A is 
comprised of a relatively thick metal sheet 1a provided with the bead 8, 
which forms the peripheral region of the substrate 1A and circumscribes 
the cylinder openings 4 with a predetermined width, and a relatively thin 
metal sheet 1b which forms the remaining region of the substrate 1A. The 
metal sheets 1a, 1b are fitted with and integrally connected to each other 
by a laser welding, as shown at 13. The second substrate 1B may be 
essentially same as the substrate 1 shown in FIG. 3 or 4. The first and 
second substrates 1A, 1B are arranged relative to each other such that the 
opposite top portions of the beads 8 of the substrates 1A, 1B are in 
direct abutment with each other. Furthermore, the third substrate 1D is 
arranged on the outer side of the first substrate 1A, and may also be 
essentially same as the substrate 1 shown in FIG. 3 or 4. However, the 
first and third substrates 1A, 1D are arranged relative to each other such 
that the opposite top portions of the beads 8 of the substrates 1A, 1D are 
oriented in opposite directions, leaving a space therebetween. 
In a practically preferred example of the gasket assembly shown in FIG. 7, 
the relatively thick metal sheet 1a of the substrate 1A and the substrates 
1B, 1D have a thickness of 0.25 mm, and the relatively thin metal sheet 1b 
of the substrate 1A has a thickness of 0.15 mm. 
The fifth embodiment explained above achieves all of the advantageous 
functions of the the gasket assembly according of the third embodiment. 
Moreover, since the gasket assembly of the third embodiment comprising the 
first and second substrates 1A, 1B is further combined with the third 
substrate 1D, it is possible to provide further improved elasticity in the 
peripheral region of the assembly circumscribing the cylinder openings 4 
and hence further improved sealing performance. 
In the first to fifth embodiments explained above, the laser-welded 
portions 13 are preferably arranged at locations close to the 
cooling-water openings 5 shown in FIGS. 1 and 2, which correspond the 
water-jackets in the cylinder block. In this instance, it is possible to 
mitigate the thermal stress imposed on the welded portions 13 and the 
thermal expansion of the welded portions 13, by the cooling function of 
the water jackets in the cylinder block. 
While the present invention has been described with reference to a specific 
embodiment, it is of course that various modifications and/or alterations 
are possible without departing from the scope of the invention as defined 
by the appended claims.