U.S. patent application number 11/828160 was filed with the patent office on 2008-01-31 for sealing structure using metal gasket.
This patent application is currently assigned to YAMAHA MARINE KABUSHIKI KAISHA. Invention is credited to Takuma Kameyama, Hiroyuki Matsumoto, Takanobu Suzuki.
Application Number | 20080023923 11/828160 |
Document ID | / |
Family ID | 38985399 |
Filed Date | 2008-01-31 |
United States Patent
Application |
20080023923 |
Kind Code |
A1 |
Kameyama; Takuma ; et
al. |
January 31, 2008 |
SEALING STRUCTURE USING METAL GASKET
Abstract
A metal gasket has a primary bead formed on an area positioned
between a cylinder bore and a cooling water passage. A second bead
is formed on an area corresponding to an opening of one or more
cooling passages. A base member of the metal gasket comprises bead
plates that have a rubber coating layer. The base member also
comprises a shim member disposed between the bead plates. The
primary bead is formed by defining a space respectively between the
bead plates and the shim member. The secondary bead is formed by
defining a space on a given area between the bead plates.
Inventors: |
Kameyama; Takuma;
(Shizuoka-ken, JP) ; Suzuki; Takanobu;
(Shizuoka-ken, JP) ; Matsumoto; Hiroyuki;
(Saitama-ken, JP) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET, FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Assignee: |
YAMAHA MARINE KABUSHIKI
KAISHA
Shizuoka-ken
JP
JAPAN METAL GASKET CO., LTD
Saitama-ken
JP
|
Family ID: |
38985399 |
Appl. No.: |
11/828160 |
Filed: |
July 25, 2007 |
Current U.S.
Class: |
277/595 ;
277/654 |
Current CPC
Class: |
F16J 15/0825 20130101;
F16J 2015/085 20130101 |
Class at
Publication: |
277/595 ;
277/654 |
International
Class: |
F16J 15/00 20060101
F16J015/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 26, 2006 |
JP |
2006-203824 |
Claims
1. A metal gasket adapted for sealing an interface between a
cylinder head and a cylinder body of an engine body, the metal
gasket comprising cylinder openings and at least one cooling water
passage positioned in the vicinity of at least one of the cylinder
openings, the metal gasket further comprising a primary bead that
protrudes toward at least one of the cylinder head and the cylinder
body, the primary bead being positioned between at least one of the
cylinder openings and the at least one cooling water passage, the
metal gasket also comprising a secondary bead that protrudes toward
at least one of the cylinder head and the cylinder body, the
secondary bead being positioned between the primary bead and the at
least one cooling water passage such that cooling water is less
likely to enter a region defined between the cylinder head and the
cylinder body.
2. The metal gasket of claim 1, wherein the secondary bead extends
along at least a portion of an edge that defines an opening of the
water passage.
3. The metal gasket of claim 1, wherein the engine body is mounted
in an outboard motor.
4. The metal gasket of claim 1, wherein a gap filler is applied on
at least a part of the secondary bead is formed.
5. The metal gasket of claim 4, wherein the engine body is mounted
in an outboard motor.
6. The metal gasket of claim 1, wherein the metal gasket comprises
a stainless steel thin-plate base member with a rubber coating
layer formed on at least one of its surfaces.
7. The metal gasket of claim 6, wherein the engine body is mounted
in an outboard motor.
8. The metal gasket of claim 6, wherein a gap filler is applied on
at least a part of the secondary bead is formed.
9. The metal gasket of claim 8, wherein the engine body is mounted
in an outboard motor.
10. The metal gasket of claim 6, wherein the base member comprises
two bead plates arranged in layers and an inner member disposed
between at least a portion of the two bead plates that defines the
primary bead, the primary bead being formed by a spaced defined
respectively between the two bead plates and the inner member, and
the secondary bead being formed by defining a space respectively
between the two bead plates and the inner member or between the two
bead plates.
11. The metal gasket of claim 10, wherein the engine body is
mounted in an outboard motor.
12. The metal gasket of claim 10, wherein a gap filler is applied
on at least a part of the secondary bead is formed.
13. The metal gasket of claim 12, wherein the engine body is
mounted in an outboard motor.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the priority benefit of Japanese
Patent Application No. 2006-203824, filed Jul. 26, 2006, which is
hereby incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention generally relates to a sealing
structure using a metal gasket designed to seal a mating face of an
engine body. More particularly, the present invention relates to
such a seal that can be positioned between an assembled cylinder
and cylinder body combination.
[0004] 2. Description of the Related Art
[0005] An engine body of an engine used in small watercraft
typically comprises multiple case members or components that are
secured together to define at least a portion of the engine. Two of
those components are the cylinder head and the cylinder body. The
cylinder head and the cylinder body are joined together at a mating
face. A sealing structure can be provided at the mating face to
reduce the likelihood that coolant or cooling water will enter into
the combustion system (See JP-A-2005-325885, for example).
[0006] The sealing structure can comprise a metal gasket that is
positioned along the mating surfaces of the cylinder head and the
cylinder body. The metal gasket can be made from a stainless
thin-plate base member with a rubber layer formed on its surface.
The metal gasket also can have a protruding bead that is formed on
an area along a periphery of a cooling water passage. The
protruding bead is pressed between the cylinder head and the
cylinder body such that a tight seal around the cooling water
passage can be formed by the protruding bead. Thus, cooling water
is less likely to seep from the cooling water passage into the
combustion system or the like.
SUMMARY OF THE INVENTION
[0007] However, in the aforementioned sealing structure, the bead
is not positioned very close to the cooling water passage. In
addition, the beam may actually cause the cylinder head and the
cylinder body to be spaced apart ever so slightly in the region of
the cooling water passage. Thus, in some situations, coolant or
cooling water can seep into the space between defined among the
cylinder head, the cylinder body, the cooling water passage and the
bead. In such situations, particularly when seawater is used as the
coolant, corrosion may occur on the mating face between the
cylinder head and the cylinder body.
[0008] Thus, in accordance with one aspect of the present
invention, a sealing structure is formed that uses a metal gasket
to inhibit corrosion of mating surfaces of the cylinder head and
the cylinder body, for instance, by reducing the likelihood of
cooling water entering the region defined between the mating
surfaces.
[0009] Thus, in accordance with one aspect of an embodiment of the
present invention, a metal gasket is provided that is adapted to
seal an interface between a cylinder head and a cylinder body of an
engine body. The metal gasket comprises cylinder openings and at
least one cooling water passage that is positioned in the vicinity
of at least one of the cylinder openings. The metal gasket further
comprises a primary bead that protrudes toward at least one of the
cylinder head and the cylinder body. The primary bead is positioned
between at least one of the cylinder openings and one of the at
least one cooling water passages. The metal gasket also comprises a
secondary bead that protrudes toward at least one of the cylinder
head and the cylinder body. The secondary bead is positioned
between the primary bead and the at least one cooling water passage
such that cooling water is less likely to enter a region defined
between the cylinder head and the cylinder body.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] These and other features, aspects and advantages of
embodiments of the present invention will be described below with
reference to the attached drawings. The drawings comprise the
following figures.
[0011] FIG. 1 is a side view of an outboard motor having a sealing
structure using a metal gasket that is arranged and configured in
accordance with certain features, aspects and advantages of an
embodiment of the present invention.
[0012] FIG. 2 is a sectional view of an engine used in the outboard
motor of FIG. 1.
[0013] FIG. 3 is a plan view of the metal gasket used in the engine
of FIG. 2.
[0014] FIG. 4 is a sectional view of the metal gasket used in the
engine of FIG. 2.
[0015] FIG. 5 is a sectional view taken along the line 5-5 of FIG.
3.
[0016] FIG. 6 is a sectional view taken along the line 6-6 of FIG.
3.
[0017] FIG. 7 is a sectional view taken along the line 7-7 of FIG.
3.
[0018] FIG. 8 is a sectional view taken along the line 8-8 of FIG.
3.
[0019] FIG. 9 is a sectional view of the metal gasket installed
between the cylinder body and the cylinder head.
[0020] FIG. 10 is a graphical depiction that represents a surface
pressure of the respective components shown in FIG. 9.
[0021] FIG. 11 is a graphical depiction that represents a surface
pressure of the respective components in the conventional art.
[0022] FIG. 12 is a plan view of a metal gasket that is arranged
and configured in accordance with certain features, aspects and
advantages of another embodiment of the present invention.
[0023] FIG. 13 is a sectional view taken along the line 13-13 of
FIG. 12.
[0024] FIG. 14 is a sectional view taken along the line 14-14 of
FIG. 12.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0025] With reference to FIG. 1, an outboard motor 10 that has a
sealing structure arranged and configured in accordance with
certain features, aspects and advantages of an embodiment of the
present invention is described below. The sealing structure,
however, may also be used for other vehicles, and particularly,
other watercraft, including but not limited to, small planing boats
having inboard engines.
[0026] The outboard motor 10 comprises a swivel bracket 11 and a
clamp bracket 12 that is connected to the swivel bracket 11 to
support the outboard motor 10. The swivel bracket 11 is connected
to a steering shaft (not shown) that is rotatable about an
approximately vertical axis when the outboard motor is in an
operational position. The swivel bracket 1 is connected
approximately to the center of the front (i.e., the front side in
the forward drive direction of the boat) of the outboard motor 10
through the steering shaft.
[0027] Thus, the outboard motor 10 can rotate relative to the
swivel bracket 11 on the horizontal plane. The clamp bracket 12 can
be removably mounted on a stem (not shown) of the hull. The upper
end of the swivel bracket 11 can be connected to the upper end of
the clamp bracket 12 via a tilt shaft 12a. More specifically, the
clamp bracket 12 comprises a pair of members that are spaced apart
by a given distance in a lateral direction of the hull. The tilt
shaft 12a extends horizontally across the pair of the members of
the clamp bracket 12 on the upper end thereof. The upper end of the
swivel bracket 11 is mounted on the tilt shaft 12a between the
paired members of the clamp bracket 12 such that the upper end of
the swivel bracket rotates in the axial direction of the tilt shaft
12a.
[0028] A housing that forms an external surface of the outboard
motor 10 comprises a cowling 13 having a top and a bottom cowl 13a
and 13b with the cowling forming an upper part of the housing, an
upper case 14 forming a middle part of the housing, and a lower
case 15 forming a lower part of the housing. An engine 16 is housed
within the cowling 13 while a propeller 17 is provided adjacent to
the lower case 15. A power transmission mechanism, including a
drive shaft 18 that transmits a driving force from the engine 16 to
the propeller 17, is housed within the upper case 14.
[0029] The engine 16 is a water-cooled three-cylinder engine in
which a crankshaft 16a extends generally in the vertical direction.
The drive shaft 18 is connected at the bottom end of the crankshaft
16a. Thus, when the engine 16 operates, the crankshaft 16a rotates
and the rotation of the crankshaft is transmitted to the propeller
17 through the drive shaft 18. The rotation of the propeller 17
produces a propulsion force. In one configuration, the cooling
water pump 19 is installed at the bottom end of the upper case 14.
A water intake 19a can be provided in the lower case 15 for
introducing cooling water (seawater). The cooling water pump 19 is
designed to introduce cooling water from the water intake 19a
during its operation and to feed the cooling water to the engine 16
for cooling.
[0030] With reference now to FIG. 2, the outer shell, which defines
the main body of the engine 16, comprises a crankcase 21 that
houses the crankshaft 16a. The main body of the engine 16 also
comprises the cylinder body 22 and the cylinder head 23 with the
cylinder body 22 positioned generally between the cylinder head 23
and the crankcase 21. The main body of the engine 16 preferably is
made of aluminum. In approximately a middle of the interior of the
cylinder body 22, three cylinders 24 (only one cylinder is shown)
are aligned and each cylinder 24 preferably comprises a bore that
defines a recess. A connecting rod 25a connects a piston 25 to the
crankshaft 16a. Each piston 25 can be housed inside a respective
cylinder 24 with the piston 25 being capable of translating
movement inside the bore. The translating movement of the piston 25
is transmitted to the crankshaft 16a through the connecting rods
25a such that the crankshaft 16a rotates due to the translation of
the piston 25.
[0031] A cooling water passage 26 is formed around the cylinders 24
on the upper side of the cylinder body 22. In the cylinder body 22,
an exhaust passage 27 is formed outside of one side (left side in
FIG. 2) of the cooling water passage 26. In turn, a cooling water
passage 28 is formed around the exhaust passage 27. Three
combustion chambers 31 (only one chamber is shown), each
communicating with the respective cylinders 24, are formed on the
bottom center (in the orientation shown in FIG. 2) of the cylinder
head 23. An intake valve 32 and an exhaust valve 33 are provided on
the top of each combustion chamber 31. An intake port 32a
communicating with the intake valve 32 of each cylinder 24 is
connected to an intake system including a carburetor 34, an intake
pipe 35 and other components. An exhaust port 33a communicating
with the exhaust valve 33 is connected to an exhaust system
including an exhaust passage 27 and other components.
[0032] The intake valve 32 is open during the intake stroke to feed
an air-fuel mixture formed of air supplied through the intake
system and fuel supplied from a fuel tank (not shown) to the
interior of the cylinder 24. The exhaust valve 33 is open during
the exhaust stroke such that the exhaust gas can be evacuated from
the cylinder 24 to the exhaust system. The engine 16 is provided
with an ignition device (not shown), and a spark generated by the
ignition device ignites the mixture for an explosion. The explosion
causes the piston 25 to move up and down, thereby rotating the
crankshaft 16a.
[0033] In a bottom area of the cylinder head 23 opposing the
cooling water passage 26, a cooling water passage 36 is formed that
communicates with the cooling water passage 26. In another bottom
area of the cylinder head 23 opposing the cooling water passage 28,
a cooling water passage 37 is formed that communicates with the
coolant water passage 28. Further, a cooling water passage 38 is
formed on one of the outer sides of the exhaust valve 33 in the
cylinder head 23. In one configuration, these cooling water
passages 26, 28, 36, 37, and 38 all communicate with each other,
defining a single flow channel. Operation of the cooling water pump
19 causes the cooling water to be introduced from the water intake
19a and causes the cooling water to flow through the interior of
the flow channel, thereby cooling the engine 16. An oil flow
channel (not shown) for supplying lubricant to the engine 16 also
can be formed in the main body of the engine 16.
[0034] With reference still to FIG. 2, a metal gasket 40 preferably
is installed on the mating face between the cylinder body 22 and
the cylinder head 23. In one configuration, the metal gasket 40 is
constructed as shown in the plan view of FIG. 3. Bores 41a, 41b,
and 41c are formed corresponding to the three cylinders 24. The
size of each bore preferably is generally equal to the size of the
bore of each cylinder 24 and the axial location of each bore 41a,
41b, 41c preferably aligns with the axis of each of the
corresponding cylinders 24. The illustrated metal gasket 40
preferably also has an exhaust gas hole 42 that is formed on an
area corresponding to the exhaust passage 27 with the size, shape
and position of the exhaust gas hole 42 being generally the same as
the size, shape and position of the exhaust passage 27.
[0035] The metal gasket 40 also preferably has small oval-shaped
cooling water holes 43a, 43b, 43c, 43d, 43e, and 43f that are
formed in sizes, shapes and locations that generally correspond to
the cooling water passages 26, 36 that are formed around the
periphery of the bores defining the cylinders 24. In other words,
the cooling water holes 43a, 43b, 43c, 43d, 43e, and 43f are
positioned around the periphery of the bores 41a, 41b and 41c. The
metal gasket 40 preferably comprises approximately arc-shaped
elongated cooling water holes 44a, 44b, and 44c that are spaced
apart from each other around a periphery of the exhaust gas hole 42
and that correspond to the cooling water passages 28 and 37.
Further, cooling water holes 45a, 45b, and 45c having different
shapes can be formed at the respective comers of the metal gasket
40, with the exclusion in the illustrated configuration of the
corner where the exhaust gas hole 42 exists.
[0036] In addition, the illustrated metal gasket 40 has three oil
holes 46a, 46b, and 46c which are approximately triangular in shape
and which generally correspond to the oil flow channel. Further,
the illustrated metal gasket 40 also has six bolt holes 47a, 47b,
47c, 47d, 47e, 47f, and 47g that generally correspond to the
location of respective bolts used to secure the cylinder head to
the cylinder body and that are positioned so as to not intersect
with the cooling water passages 26 and 36.
[0037] Two through holes 48a and 48b can be formed at the interval
approximately equal to the interval between the bolt holes 47e and
47f on the outsides of the bolt holes 47e and 47f such that the
bolt holes 47e and 47f are interposed between the through holes 48a
and 48b. The bolt holes 47a, 47b, 47c, 47d, 47e, 47f, and 47g are
designed to allow a bolt (not shown) used to connect the cylinder
body 22 and the cylinder head 23 to be inserted therethrough. The
through holes 48a and 48b are designed to allow a positioning pin
(not shown) for generally aligning the cylinder body 22 and the
cylinder head 23 to be inserted therethrough.
[0038] As shown in FIG. 4, the metal gasket 40 preferably is formed
by interposing a thin-plate shim member 53, which defines an inner
member, at a desired location between thin bead plates 51, 52 that
are arranged in layers. The bead plates 51, 52 and the shim member
53 can be made of stainless steel with each having a rubber coating
layer (not shown) or the like formed on the surface. In one
configuration, the bead plates 51, 52 have a predetermined
thickness of approximately 0.2 mm while the shim member 53 has a
predetermined thickness of approximately 0.1 mm.
[0039] The bead plates 51, 52 preferably are vertical symmetrical
(i.e., the top and bottom in FIG. 4). In one configuration, the
bead plate 51 has protrusions 51a, 51b, 51c that extend upward at
desired locations. The bead plate 52 has protrusions 52a, 52b, 52c
that extend downward at desired locations. Preferably, each of the
protrusions 51a, 52a is shaped into a curved surface while each of
protrusions 51b, 51c, 52b, 52c is each shaped into a table or
plateau shape having a bent portion. The protrusions 51a, 52a and
the shim member 53 located within the protrusions 51a, 52a
preferably define a primary bead 54. The protrusions 51b, 52b and a
part of the shim member 53 located within the protrusions 51b, 52b
preferably define a secondary bead 55. Also, the protrusions 51c,
52c preferably define a half bead 56 having an open end.
[0040] As shown in FIG. 3, the primary bead 54, the secondary bead
55 and the half bead 56 preferably are formed in multiple areas of
the metal gasket 40. More specifically, FIG. 5 is a sectional view
taken along the line 5-5 of FIG. 3 (primary bead 54); FIG. 6 is a
sectional view taken along the line 6-6 of FIG. 3 (primary bead 54,
secondary bead 55 and half bead 56); FIG. 7 is a sectional view
taken along the line 7-7 of FIG. 3 (half bead 56); and FIG. 8 is a
sectional view taken along the line 8-8 of FIG. 3 (half bead
56).
[0041] As shown in FIG. 5, the primary bead 54, in which the shim
member 53 is interposed between the protrusions 51a, 52a, is formed
on an area around the peripheries of the bores 41a, 41b, and 41c.
Thus, the primary bead 54 can circumscribe the openings for the
cylinder bores.
[0042] As shown in FIG. 6, the metal gasket 40, on an area defined
between each of the bores 41a, 41b, 41c and the periphery of the
metal gasket 40, comprises the primary bead 54, the secondary bead
55 and the half bead 56 formed in order from the bores 41a, 41b,
41c to the periphery of the metal gasket 40. In the illustrated
configuration, as shown in FIG. 9, the secondary bead 55 preferably
extends from an area of the metal gasket 40 corresponding to the
cooling water passages 26, 36 to areas on the opposite sides of the
cooling water passages 26, 36 (i.e., the edge of the openings 26,
36 where they extend through the mating faces of the cylinder head
and the cylinder body). Preferably, the half bead 56 is disposed
with its open end aligned with the outer edge of the mating face
between the cylinder body 22 and the cylinder head 23.
[0043] FIG. 10 represents a surface pressure exerted on the mating
face between the cylinder body 22 and the cylinder head 23 when the
primary bead 54, the secondary bead 55 and the half bead 56 are
used. In FIG. 10, the lateral direction along a straight line (a)
represents the respective areas of the metal gasket 40, while the
vertical direction perpendicular to the straight line (a)
represents surface pressures of the respective areas. On the
straight line (a), the surface pressure is "0." The surface
pressure is larger in an area protruding more downward from the
straight line (a). The larger surface pressure area has better
sealability. In accordance with FIG. 10, a larger peak (b) of the
surface pressure appears on the area of the primary bead 54, and a
peak (c) smaller than the peak (b) appears on the area of the half
bead 56. Further, small peaks (d) and (e) appear on the respective
areas corresponding to the periphery of the cooling water passages
26 and 36 on the opposite sides.
[0044] FIG. 11 is provided for reference purpose, showing the
surface pressure exerted on the mating face between the cylinder
body 22 and the cylinder head 23 when the conventional metal gasket
is used that is generally the same as the metal gasket 40 without a
secondary bead 55. In this case, similar to FIG. 10, a larger peak
(b) of the surface pressure appears on the area of the main bead
54, while a peak (c) smaller than the peak (b) appears on the area
of the half bead 56. However, no peak of the surface pressure
appears on the areas corresponding to the periphery of the cooling
water passages 26 and 36 on the opposite sides, except a contact
pressure with the edge. It can be seen from the measurement results
that providing the secondary bead 55 on the metal gasket 40 helps
to exert a greater surface pressure on areas adjacent to the
periphery of the cooling water passages 26, 36 on the opposite
sides on the mating face between the cylinder body 22 and the
cylinder head 23; cooling water thus is less likely to enter into
the mating face between the cylinder body 22 and the cylinder head
23.
[0045] With reference to FIG. 7, four half beads 56 can alternate
between the periphery of the metal gasket 40 through the oil hole
46b to the inner periphery of the bolt hole 47f. More specifically,
in the illustrated configuration, each half bead 56 can be disposed
such that its open end is positioned respectively at the periphery
of the metal gasket 40, the oil hole 46b and the inner periphery of
the bolt hole 47f.
[0046] As shown in FIG. 8, three half beads 56 can alternate in
opposite directions where the gasket 40 extends from the inner
periphery of the exhaust gas hole 42, through the cooling water
hole 44b and to the outer periphery of the metal gasket 40. In this
case, each half bead 56 can be disposed such that its open end is
positioned respectively at the periphery of the metal gasket 40 and
the inner periphery of the cooling water hole 44b. The joined
portion of the bead plates 51, 52 can be positioned in an area of
the metal gasket 40 that corresponds to the inner periphery of the
gas hole 42.
[0047] As described above, the metal gasket 40 preferably has the
primary bead 54 formed on an area corresponding to the middle
between the bores 41a, 41b, 41c where the highest sealability is
desired and at the cooling water passages 26, 36. This
configuration reduces the likelihood of cooling water in the
cooling water passages 26, 36 entering through the mating face
between the cylinder body 22 and the cylinder head 23 toward the
bores 41a, 41b, 41c.
[0048] Further, the metal gasket 40 has the secondary bead 55
extending from an area corresponding to the cooling water passages
26, 36 to areas on the opposite sides of the cooling water passages
26, 36 (i.e., the inner edge sides of the mating face between the
cylinder body 22 and the cylinder head 23). This reduces the
likelihood of the cooling water entering into the mating face
between the cylinder body 22 and the cylinder head 23. Further, the
metal gasket 40 has the half bead 56 formed on another area where
sealability is desired. Thus, sealability appropriate to the
respective areas can be achieved.
[0049] As described above, the metal gasket 40 not only has the
primary bead 54 that is formed on an area corresponding to the
middle portion disposed between the bores 41a, 41b, 41c and the
cooling water passages 26, 36, but also the secondary bead 55 that
is formed on an area corresponding to an edge defining the opening
of the cooling water passages 26, 36. Thus, the surface pressure
increases on the edge that defines the opening of the cooling water
passages 26, 36, which reduces the likelihood that cooling water
will enter into the mating face between the cylinder body 22 and
the cylinder head 23.
[0050] The metal gasket 40 can be made from a stainless steel
thin-plate base member with a rubber coating layer formed on its
surface. Thus, the metal gasket 40 can reduce the likelihood of
entry of seawater or other coolant into the mating face between the
cylinder body 22 and the cylinder head 23 as a result of scratches
found on the mating face. Further, the primary bead 54 is formed by
the two bead plates 51, 52 as well as the shim member 53 disposed
between the bead plates 51, 52. Also, the primary bead 54 is formed
by defining a space respectively between the bead plates 51 and 52
and the shim member 53. Therefore, the surface pressure increases
on the area corresponding to the primary bead 54 on the mating face
between the cylinder body 22 and the cylinder head 23, which
improves the sealing ability in the regions of the bores 41a, 41b,
41c and the cooling water passages 26, 36.
[0051] Further, the secondary bead 55 can be formed by defining a
space on a given area between the two bead plates 51, 52. Thus, the
surface pressure increases on an area corresponding to the border
of the mating face between the cylinder body 22 and the cylinder
head 23 in the region of the cooling water passages 26 and 36. This
can reduce the likelihood of cooling water flowing through the
cooling water passages 26 and 36 entering into the mating face
between the cylinder body 22 and the cylinder head 23.
[0052] The primary and secondary beads of the metal gasket, within
which the respective spaces are formed, preferably function as a
spring or a cushion. Thus, the surface pressure that is exerted by
the metal gasket increases, which results in better sealing of the
mating faces between the cylinder head and the cylinder body. In
addition, the primary bead includes two bead plates and the inner
member, which ensures better sealing between the cylinder forming
recesses and the cooling water passage. In an area of the metal
gasket where the secondary bead exists, the inner member may be
provided in order to reinforce the secondary bead, although the
inner member is not always needed.
[0053] FIG. 12 illustrates another metal gasket 60 that is arranged
and configured in accordance with certain features, aspects and
advantages of an embodiment of the present invention. The metal
gasket 60, which is generally the same as the metal gasket 40, has
certain areas on the front and back surfaces to which a gap filler
is applied. Thus, components common to the metal gasket 40 are
denoted by the same reference numeral and the description thereof
is not repeated. In the illustrated configuration, the metal gasket
60 has a gap filling layer 61 disposed respectively on the front
and back surfaces at the border of the mating face between the
cylinder body 22 and the cylinder head 23 and the cooling water
passages 26, 36 and at areas adjacent to the border (the gap
filling layer on the back surface is not shown) such that the gap
filling layer 61 surrounds the cooling water passages 26 and
36.
[0054] The illustrated metal gasket 60 also has gap filling layers
62, 63, 64 formed respectively on the front and back surfaces at
borders of the mating face between the cylinder body 22 and the
cylinder head 23 and the cooling water holes 44a, 44b, 44c and at
areas adjacent to the borders (the gap filling layers on the back
surface are not shown) such that the gap filling layers 62, 63, 64
surround the cooling water holes 44a, 44b, 44c.
[0055] FIG. 13 illustrates a sectional view taken along the line
13-13 of FIG. 12. FIG. 14 illustrates a sectional view taken along
the line 14-14 of FIG. 12. To be more specific, the gap filling
layers 61, 62, 63, 64 are formed on the respective surfaces of the
secondary bead 55 or the half bead 56. Thus, the mating face
between the cylinder body 22 and the cylinder head 23, and the
secondary bead 55 or the half bead 56, which contacts the mating
face through the gap filing layers 61, 62, 63, 64, are brought into
tighter contact with each other, resulting in higher sealability by
the metal gasket 60. Moreover, in the event that the rigidity of
the engine can cause a gap on the mating face between the cylinder
head and the cylinder body, the beads provided to the metal gasket
may not be sufficient enough in all situations to prevent entry of
the cooling water into the mating face. Thus, the gap filler can
further reduce the likelihood of cooling water entering. The
functions and effects of the metal gasket 60, other than those
described above, are generally the same as in the case with the
metal gasket 40 according to the aforementioned embodiment.
[0056] Although the present invention has been described in terms
of certain embodiments, other embodiments apparent to those of
ordinary skill in the art also are within the scope of this
invention. For example, in the aforementioned embodiments, the
secondary beads 55, 75 comprise left and right long protrusions
51b, 51b, or protrusions 71b, 71b, and an inner plate 73. However,
the secondary bead 55 may be short and can be formed on one of the
sides of the cooling water passages 26 and 36. In short, the
secondary bead 55 may be formed on any area corresponding to the
border of the mating face between the cylinder body 22 and the
cylinder head 23 and the cooling water passages 26, 36. Further,
the layout, structure and materials of the components in the
sealing structure using the metal gasket may be modified as
appropriate within the technical scope of the invention. Thus,
various changes and modifications may be made without departing
from the spirit and scope of the invention. For instance, various
components may be repositioned as desired. Moreover, not all of the
features, aspects and advantages are necessarily required to
practice the present invention. Accordingly, the scope of the
present invention is intended to be defined only by the claims that
follow.
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