U.S. patent application number 10/570026 was filed with the patent office on 2008-10-09 for water-cooled engine and cylinder block thereof.
Invention is credited to Yujirou Ishikawa.
Application Number | 20080245320 10/570026 |
Document ID | / |
Family ID | 34554778 |
Filed Date | 2008-10-09 |
United States Patent
Application |
20080245320 |
Kind Code |
A1 |
Ishikawa; Yujirou |
October 9, 2008 |
Water-Cooled Engine and Cylinder Block Thereof
Abstract
A cylinder block has a cylinder bore and a water jacket provided
about the cylinder bore. The cylinder block is divided at the water
jacket into a cylinder liner portion and a cylinder outer wall
portion. The cylinder liner portion has a wall defining the
cylinder bore. The cylinder outer wall portion surrounds the wall
of the cylinder liner portion, thereby defining the water jacket
between the cylinder outer wall portion and the wall of the
cylinder liner portion. The cylinder liner portion includes an
upper deck portion integrally formed with the cylinder liner
portion. The upper deck portion contacts the cylinder head
assembled to the cylinder block. The cylinder outer wall portion
has a top surface that functions as a receiving surface that
contacts and supports the upper deck portion.
Inventors: |
Ishikawa; Yujirou;
(Toyota-shi, JP) |
Correspondence
Address: |
KENYON & KENYON LLP
1500 K STREET N.W., SUITE 700
WASHINGTON
DC
20005
US
|
Family ID: |
34554778 |
Appl. No.: |
10/570026 |
Filed: |
October 28, 2004 |
PCT Filed: |
October 28, 2004 |
PCT NO: |
PCT/JP04/16386 |
371 Date: |
March 1, 2006 |
Current U.S.
Class: |
123/41.74 |
Current CPC
Class: |
F02F 1/108 20130101;
F02F 7/0007 20130101; F02F 1/10 20130101 |
Class at
Publication: |
123/41.74 |
International
Class: |
F01P 3/00 20060101
F01P003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 31, 2003 |
JP |
2003-373196 |
Jun 22, 2004 |
JP |
2004-183991 |
Claims
1. A water-cooled engine, comprising: a cylinder block having a
cylinder bore and a water jacket provided about the cylinder bore;
and a cylinder head assembled to the cylinder block, the
water-cooled engine being characterized in that: the cylinder block
is divided at the water jacket into a cylinder liner portion and a
cylinder outer wall portion, wherein the cylinder liner portion has
a wall defining the cylinder bore, and wherein the cylinder outer
wall portion surrounds the wall of the cylinder liner portion,
thereby defining the water jacket between the cylinder outer wall
portion and the wall of the cylinder liner portion, and wherein the
cylinder liner portion includes an upper deck portion integrally
formed with the cylinder liner portion, the upper deck portion
contacting the cylinder head assembled to the cylinder block, and
wherein the cylinder outer wall portion has a top surface that
functions as a receiving surface, the receiving surface contacting
and supporting the upper deck portion.
2. The water-cooled engine according to claim 1, characterized in
that the cylinder outer wall portion includes a support portion
integrally formed with the cylinder outer wall portion, the support
portion supporting a lower portion of the cylinder liner
portion.
3. The water-cooled engine according to claim 2, characterized in
that the support portion has a support surface that contacts and
supports a lower end of the cylinder liner portion.
4. The water-cooled engine according to claim 2, characterized in
that the support portion has a support surface that contacts and
supports the wall of the cylinder liner portion.
5. The water-cooled engine according to any one of claims 1 to 4,
characterized in that the cylinder block includes a crankcase
portion that is integrally formed with the cylinder outer wall
portion.
6. The water-cooled engine according to any one of claims 1 to 5,
characterized in that the upper deck portion has a through hole
that connects a fluid passage formed in the cylinder head with a
fluid passage formed in the cylinder outer wall portion.
7. The water-cooled engine according to any one of claims 1 to 6,
characterized in that, in a state where the upper deck portion is
held between a bottom surface of the cylinder head and the
receiving surface, the cylinder head and the cylinder outer wall
portion are fastened to each other such that the cylinder block is
assembled to the cylinder head.
8. A cylinder block of a water-cooled engine, wherein the cylinder
block has a cylinder bore and a water jacket provided about the
cylinder bore, and is assembled to a cylinder head, the cylinder
block being characterized in that: the cylinder block is divided at
the water jacket into a cylinder liner portion and a cylinder outer
wall portion, wherein the cylinder liner portion has a wall
defining the cylinder bore, and wherein the cylinder outer wall
portion surrounds the wall of the cylinder liner portion, thereby
defining the water jacket between the cylinder outer wall portion
and the wall of the cylinder liner portion, and wherein the
cylinder liner portion includes a substantially planar upper deck
portion integrally formed with the cylinder liner portion, the
upper deck portion forming a top surface of the cylinder block, and
wherein the cylinder outer wall portion has a top surface that
functions as a receiving surface, the receiving surface contacting
and supporting the upper deck portion.
9. The cylinder block according to claim 8, characterized in that
the cylinder outer wall portion includes a support portion
integrally formed with the cylinder outer wall portion, the support
portion supporting a lower portion of the cylinder liner
portion.
10. The cylinder block according to claim 9, characterized in that
the support portion has a support surface that contacts and
supports a lower end of the cylinder liner portion.
11. The cylinder block according to claim 9, characterized in that
the support portion has a support surface that contacts and
supports the wall of the cylinder liner portion.
12. The cylinder block according to any one of claims 8 to 11,
characterized by a crankcase portion that is integrally formed with
the cylinder outer wall portion.
13. The cylinder block according to any one of claims 8 to 12,
characterized in that the upper deck portion has a through hole
that communicates with a fluid passage formed in the cylinder outer
wall portion.
14. The cylinder block according to any one of claims 8 to 13,
characterized in that the receiving surface of the cylinder outer
wall portion has a bolt receiving hole to which a head bolt is
threaded, and the upper deck portion has a bolt through hole
through which the head bolt is passed.
Description
TECHNICAL FIELD
[0001] The present invention relates to a water-cooled engine that
has a cylinder block assembled with a cylinder head, which cylinder
block has a water jacket defined about cylinder bores. The present
invention also pertains to a cylinder block used in such a
water-cooled engine.
BACKGROUND ART
[0002] In the cylinder block of a water-cooled engine, a water
jacket for circulating coolant is defined about cylinder bores. The
cylinder block generally consists of an upper cylinder liner
portion in which cylinder bores are formed, and a lower crankcase
portion that forms a crankcase.
[0003] The types of the water jacket in the cylinder block of such
a water-cooled engine include an open-deck structure in which the
water jacket is open at the top of the cylinder block and a
closed-deck structure in which the water jacket is not open at the
top of the cylinder block but closed.
[0004] Japanese Laid-Open Utility Model No. 62-119450 discloses a
cylinder block for a water-cooled engine, having upper and lower
parts, or a cylinder liner portion and a crankcase portion. In the
cylinder block of the publication, a water jacket is open to the
lower portion of the cylinder liner portion. Therefore, even if a
water jacket of the closed deck structure is used, the cylinder
block can be molded without using a core. Therefore, a die casting
to which sand core is difficult to apply is used can be adopted to
mold the cylinder block.
[0005] Japanese Laid-Open Patent Publication No. 2002-97997
discloses a cylinder block of a water cooled engine, in which a
lower end of a cylinder liner is press fitted to a cylinder main
body. This cylinder block is known as a wet liner structure in
which the cylinder liner contacts the water jacket.
[0006] This publication also discloses a structure in which a
circumferential projection is formed on an end of the cylinder
liner close to the cylinder head and the projection contacts the
cylinder block main body. This structure supports the cylinder
liner at its upper and lower ends so that the cylinder liner is
firmly secured.
[0007] The cylinder block of the above described water-cooled
engine has an intricate shape because of the water jacket defined
about the cylinder bores. Therefore, casting deficiencies such as
blow holes are likely to be formed. Such casting deficiencies
degrade the quality. In the die for casting such a cylinder block,
a portion for molding the water jacket is extremely thin and
difficult to cool. This results in a shortened life of the die.
Particularly, in recent years, demands for reduced size and weight
of engines and a reduced amount of coolant circulation have
resulted in narrower water jackets. Accordingly, the above
deficiencies have become obvious.
[0008] Although the cylinder block disclosed in Japanese Laid-Open
Utility Model No. 62-119450 has separately formed crankcase portion
and cylinder liner portion, a narrow and deep groove, which
functions as a water jacket, has to be formed in the cylinder liner
portion. Therefore, the above described deficiencies are inevitable
when casting the cylinder block.
[0009] However, these deficiencies can be avoided by adopting a wet
liner structure as described in Japanese Laid-Open Patent
Publication No. 2002-97997. That is, since the cylinder liner forms
a wall surface of the water jacket facing the cylinder, it is
possible to form a water jacket without forming a narrow and deep
groove in the cylinder block main body.
[0010] However, in this type of cylinder block, since the lower end
of the cylinder liner is press fitted in the cylinder block main
body, the cylinder bores can be deformed. It is thus necessary to
finish the cylinder bore wall surfaces after the cylinder liner is
assembled.
[0011] Further, a cylinder block having a wet liner structure has
the following drawbacks. During operation of the engine, the bottom
surface of the cylinder head is deformed as if it is lifted by
combustion pressure. At this time, the top surface of the cylinder
block main body, which is fastened to the cylinder head with bolts,
is deformed integrally with the cylinder head bottom surface.
However, the cylinder liner is not directly fixed to the cylinder
head, and is pressed downward by the head gasket. Therefore, the
top surface of the cylinder liner does not follow the deformation
of the cylinder head bottom surface, which creates a step between
the top surface of the cylinder liner and the top surface of the
cylinder block. This degrades the sealing of coolant and combusted
gas. Forming a projection at the upper portion of the cylinder
liner limits deformation of the cylinder liner in the
circumferential direction relative to the cylinder block main body.
However, the projection is not sufficient to permit the top surface
of the cylinder liner to follow deformation of the cylinder head
bottom surface.
SUMMARY OF THE INVENTION
[0012] Accordingly, it is an objective of the present invention to
provide a water-cooled engine that facilitates formation of a water
jacket about cylinder bores and to provide a cylinder block of the
engine.
[0013] To achieve the foregoing and other objectives and in
accordance with the purpose of the invention, a water cooled engine
having a cylinder block and a cylinder head is provided. The
cylinder block has a cylinder bore and a water jacket provided
about the cylinder bore. The cylinder head is assembled to the
cylinder block. The cylinder block is divided at the water jacket
into a cylinder liner portion and a cylinder outer wall portion.
The cylinder liner portion has a wall defining the cylinder bore.
The cylinder outer wall portion surrounds the wall of the cylinder
liner portion, thereby defining the water jacket between the
cylinder outer wall portion and the wall of the cylinder liner
portion. The cylinder liner portion includes an upper deck portion
integrally formed with the cylinder liner portion. The upper deck
portion contacts the cylinder head assembled to the cylinder block.
The cylinder outer wall portion has a top surface that functions as
a receiving surface. The receiving surface contacts and supports
the upper deck portion.
[0014] The present invention also provides a cylinder block of a
water-cooled engine. The cylinder block has a cylinder bore and a
water jacket provided about the cylinder bore, and is assembled to
a cylinder head. The cylinder block is divided at the water jacket
into a cylinder liner portion and a cylinder outer wall portion.
The cylinder liner portion has a wall defining the cylinder bore.
The cylinder outer wall portion surrounds the wall of the cylinder
liner portion, thereby defining the water jacket between the
cylinder outer wall portion and the wall of the cylinder liner
portion. The cylinder liner portion includes a substantially planar
upper deck portion integrally formed with the cylinder liner
portion. The upper deck portion forms a top surface of the cylinder
block. The cylinder outer wall portion has a top surface that
functions as a receiving surface. The receiving surface contacts
and supports the upper deck portion.
[0015] Other aspects and advantages of the invention will become
apparent from the following description, taken in conjunction with
the accompanying drawings, illustrating by way of example the
principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The invention, together with objects and advantages thereof,
may best be understood by reference to the following description of
the presently preferred embodiments together with the accompanying
drawings in which:
[0017] FIG. 1 is a perspective view illustrating a main body of a
water-cooled engine according to one embodiment of the present
invention;
[0018] FIG. 2(a) is a perspective view illustrating the cylinder
block of the embodiment of FIG. 1;
[0019] FIG. 2(b) is a side view illustrating the cylinder block of
the embodiment of FIG. 1;
[0020] FIG. 3 is an exploded perspective view illustrating the
cylinder block;
[0021] FIG. 4(a) is a perspective view illustrating an inner block
of the cylinder block;
[0022] FIG. 4(b) is a side view illustrating the inner block of the
cylinder block;
[0023] FIG. 5(a) is a perspective view illustrating an outer block
of the cylinder block;
[0024] FIG. 5(b) is a side view illustrating the outer block of the
cylinder block;
[0025] FIG. 6 is a cross-sectional view taken along line 6-6 of
FIG. 2(b); and
[0026] FIG. 7 is a cross-sectional view taken along line 7-7 of
FIG. 1.
BEST MODE FOR CARRYING OUT THE INVENTION
[0027] A water-cooled engine 1 and a cylinder block 3 of the engine
according to one embodiment of the present invention will now be
described with reference to drawings.
[0028] FIG. 1 is a perspective view illustrating a main body of the
water-cooled engine 1 of the present invention. The engine 1 is
in-line four cylinders. Generally, the main body of the
water-cooled engine 1 consists of a cylinder head 2 and the
cylinder block 3. The cylinder head 2 and the cylinder block 3 are
fastened to each other with a gasket 4 in between with bolts.
Although not illustrated, a head cover is attached to the upper
side of the cylinder head 2, and an oil pan is attached to the
lower side of the cylinder block 3.
[0029] FIG. 2(a) is a perspective view of the cylinder block 3, and
FIG. 2(b) is a side view of the cylinder block 3. As shown in these
drawings, the cylinder block 3 has four cylinder bores 5 formed in
an upper portion. A crankcase portion 31, or a skirt portion of the
cylinder block 3, is provided below the cylinder bores 5. The
crankcase portion 31, together with the oil pan attached to the
lower side, forms a crankcase for accommodating a crankshaft. An
upper deck portion 22 is provided at the top portion of the
cylinder block 3. The cylinder head 2 is placed on and contacts the
upper deck portion 22.
[0030] FIG. 3 is an exploded perspective view of the cylinder block
3. As shown in this drawing, the cylinder block 3 has an inner
block 20 and an outer block 30, which are separately formed.
Accordingly, a section between the upper deck portion 22 and the
crankcase portion 31 is divided into a cylinder liner portion 21
and a cylinder outer wall portion 32 at a portion that functions as
a water jacket surrounding the cylinder bores 5. The cylinder liner
portion 21 forms a circumferential wall defining the cylinder bores
5, and the outer wall portion 32 forms an outer wall surrounding
the water jacket. The cylinder liner portion 21 is formed
integrally with the upper deck portion 22, and the cylinder outer
wall portion 32 is formed integrally with the crankcase portion
31.
[0031] The inner block 20 forming the cylinder liner portion 21 and
the upper deck portion 22 is made, for example, of an aluminum
alloy or a magnesium alloy and mold to be an integral member
through die casting. Like the inner block 20, the outer block 30
forming the crankcase portion 31 and the cylinder outer wall
portion 32 is made, for example, of an aluminum alloy or a
magnesium alloy and mold to be an integral member through die
casting. Reinforcing ribs 3a are formed horizontally and vertically
on the outer surface of the crankcase portion 31 and the cylinder
outer wall portion 32 of the outer block 30.
[0032] FIG. 4(a) is a perspective view of the inner block 20, and
FIG. 4(b) is a side view of the inner block 20.
[0033] As shown in these drawings, the cylinder liner portion 21 of
the inner block 20 has a shape formed by connecting four
cylindrical bodies in series. The inner surface 23 of each
cylindrical body form the circumferential wall of one of the
cylinder bores 5. The outer surface 24 of the cylindrical bodies
form a wall of the water jacket formed about the cylinder bores 5.
A projection 25 projecting radially outward from the cylinder bores
5 is formed at the lower end of the cylinder liner portion 21. The
inner surfaces 23 of the cylinder liner portions 21, which define
the cylinder bores 5, are coated with protective films, for
example, of iron through thermal spraying.
[0034] The upper deck portion 22 is formed substantially planar at
a top portion of the cylinder liner portion 21. The upper deck
portion 22 forms a top surface portion of the cylinder block 3. The
upper surface of the upper deck portion 22 functions as a mounting
surface 26, on which the cylinder head 2 is mounted. During
assembly, the bottom of the cylinder head 2 contacts the mounting
surface 26. Bolt through holes 27 are formed in the upper deck
portion 22. The bolt through holes 27 receive head bolts 7 for
fastening the cylinder head 2 and the cylinder block 3 to each
other (see FIG. 7). Each bolt 7 is not threaded or fixed to the
corresponding bolt through hole 27 but is merely passed through the
bolt through hole 27. Further, the upper deck portion 22 has
through holes such as coolant holes 28, oil holes 29a, and blowby
gas holes 29b.
[0035] FIG. 5(a) is a perspective view of the outer block 30, and
FIG. 5(b) is a side view of the outer block 30.
[0036] As shown in these drawings, the crankcase portion 31 has at
its upper portion the cylinder outer wall portion 32, which
protrudes upward. The cylinder outer wall portion 32 is formed
substantially as a loop and has an inner surface 35. The inner
surface 35 faces the outer surface 24 of the cylinder liner portion
21 of the inner block 20. The inner surface 35 of the cylinder
outer wall portion 32 forms an outer wall of the water jacket. A
step 35a is formed substantially in the middle with respect to the
vertical direction (see FIG. 3). A section of the inner surface 35
that is below the step 35a is formed to be closer to the outer
surface 24 of the cylinder liner portion 21 than the section above
the step 35a to the outer surface 24.
[0037] A flange 36 protruding radially outward of the cylinder
bores 5 is formed at the upper portion of the cylinder outer wall
portion 32. The flange 36 is coupled to some of the ribs 3a formed
on the outer surface of the cylinder outer wall portion 32, which
increases the rigidity. The top surface of the cylinder outer wall
portion 32, at which the flange 36 is formed, forms a receiving
surface 32a that contacts and supports the upper deck portion 22 of
the inner block 20. In this embodiment, the flange 36 is formed at
the upper end of the cylinder outer wall portion 32 so that the
area of the receiving surface 32a is increased.
[0038] Bolt receiving holes 37 are formed in the receiving surface
32a of the cylinder outer wall portion 32. The above described head
bolts 7 shown in FIG. 7 are threaded to the bolt receiving holes
37. Further, oil passages 38a, blowby gas passages 38b are formed
in the cylinder outer wall portion 32. The passages 38a, 38b are
open in the receiving surface 32a. The oil passages 38a return
surplus oil from the cylinder head 2 to the oil pan. The blowby gas
passages 38b extend from the crankcase into the cylinder head 2,
and allow blowby gas to pass therethrough. A coolant port 39 is
formed on a side of the cylinder outer wall portion 32. The coolant
port 39 permits coolant to flow into and out of the water
jacket.
[0039] The cylinder liner portion 21 of the inner block 20 is
inserted into the cylinder outer wall portion 32 from above. At
this time, a clearance exists between the outer surface 24 of the
cylinder liner portion 21 and the inner surface 35 of the cylinder
outer wall portion 32. The coolant holes 28 formed in the upper
deck portion 22 open to the clearance at the lower side of the
upper deck portion 22. Also, the openings of the bolt receiving
holes 37, the oil passages 38a, and the blowby gas passages 38b
formed in the cylinder outer wall portion 32 are aligned with the
bolt through holes 27, the oil holes 29a, and the blowby gas holes
29b formed in the upper deck portion 22, respectively.
[0040] FIG. 6 is a cross-sectional view illustrating the cylinder
block 3 taken along line 6-6 of FIG. 2(b), in which the inner block
20 is assembled with the outer block 30.
[0041] As shown in this drawing, the cylinder liner portion 21 of
the inner block 20 is inserted into the cylinder outer wall portion
32 to a point where the receiving surface 32a of the cylinder outer
wall portion 32 contacts the lower surface of the upper deck
portion 22. Accordingly, the outer surface 24 of the cylinder liner
portion 21, the inner surface 35 of the cylinder outer wall portion
32, and the lower surface of the upper deck portion 22 define a
water jacket 6 about the cylinder bores 5.
[0042] On the other hand, the outer surface of the projection 25 at
the lower end of the cylinder liner portion 21 contacts a lower
portion of the inner surface 35 of the cylinder outer wall portion
32. Accordingly, the cylinder liner portion 21 contacts and is
supported by the lower portion of the inner surface 35 of the
cylinder outer wall portion 32 at the outer wall of the lower
portion of the cylinder liner portion 21. That is, in this
embodiment, the lower portion of the inner surface 35 of the
cylinder outer wall portion 32 functions as a support portion and a
support surface.
[0043] FIG. 7 is a cross-sectional view illustrating the main body
portion of the water-cooled engine 1 taken along line 7-7 of FIG.
1, in which the cylinder block 3 is assembled with the cylinder
head 2. As shown in these drawings, the cylinder head 2 is
assembled with the cylinder head 2 by fastening the head bolts
7.
[0044] The head bolts 7 are inserted through the bolt through holes
27 formed in the upper deck portion 22 of the inner block 20, and
threaded to the bolt receiving holes 37 formed in the outer block
30. At this time, the upper deck portion 22 of the inner block 20
is held between the bottom surface 2a of the cylinder head 2 and
the receiving surface 32a of the cylinder outer wall portion 32 of
the outer block 30. That is, fastening the head bolts 7 applies
compression force to the upper deck portion 22 through the bottom
surface 2a and the receiving surface 32a. Accordingly, the upper
deck portion 22 is fixed.
[0045] Although not illustrated, a water jacket, oil passages, and
blowby gas passages are formed in the cylinder head 2 and are open
at the bottom surface 2a of the cylinder head 2. When the assembly
is complete, these openings are aligned with the corresponding
openings in the upper deck portion 22, or the coolant holes 28, the
oil holes 29a, and the blowby gas holes 29b. The through holes in
the upper deck portion 22 connect the passages in the cylinder head
2 with the corresponding passages in the outer block 30.
[0046] In this embodiment thus constructed, the inner wall of the
water jacket 6 surrounding the cylinder bores 5 is formed on the
inner block 20, and the outer wall of the water jacket is formed on
the separate outer block 30. This simplifies the shape of portions
of the die that is related to the formation of the water jacket 6.
Since the shape of the die is simplified, casting deficiencies such
as blow holes are significantly reduced and the life of the die is
extended. Accordingly, the formation of the water jacket about the
cylinders is facilitated.
[0047] In the case where the wall surfaces of the cylinder bores 5
are formed by forming protective films, for example, of iron
through thermal spraying, cavities formed by casting deficiencies
such as blow holes will remain on the surfaces of the cylinder
bores 5. As a result, a clearance exits between the sliding
surfaces of each cylinder bore 5 and the corresponding piston ring.
This creates drawbacks such as increased consumption of lubricant.
Thus, conventionally, prior to forming a protective film through
thermal spraying, cavities caused by casting deficiencies must be
removed through machining, which increases the manufacturing costs.
To the contrary, in this embodiment, since the above described
simplification of the die significantly reduces casting
deficiencies such as blow holes, the manufacturing costs related to
the thermal spraying to the cylinder bore surfaces are reduced.
[0048] This embodiment has the following advantages.
[0049] (1) The cylinder block 3 has the inner block 20 and the
outer block 30, which are separately formed, and the water jacket 6
is defined by the inner wall of the outer block 30 and the outer
wall of the inner block 20. This allows the shape of the die to be
simplified. Accordingly, casting deficiencies such as blow holes
are reduced and the life of the die is extended. Accordingly, the
formation of the water jacket about the cylinders is
facilitated.
[0050] (2) Since the casting deficiencies are reduced, formation of
the protective films, for example, of iron on the surfaces of the
cylinder bores 5 is facilitated.
[0051] (3) Since the outer surface of the projection 25 formed at
the lower end of the cylinder liner portion 21 of the inner block
20 are supported by the lower portion of the inner surface 35 of
the cylinder outer wall portion 32, the cylinder liner portion 21
is stably fixed.
[0052] (4) When assembling the cylinder head 2 with the cylinder
block 3, the upper deck portion 22 of the inner block 20 is held
between the bottom surface 2a of the cylinder head 2 and the
receiving surface 32a of the cylinder outer wall portion 32, and is
fixed by fastening the head bolts 7. Thus, the inner block 20 is
stably fixed. Also, the upper deck portion 22, the cylinder outer
wall portion 32, and the cylinder head 2 are fastened to each other
with the head bolts 7. Therefore, even if the bottom surface of the
cylinder head 2 is deformed upward by combustion pressure, the
contacting surfaces of sealing portions are not separated. The
sealing performance therefore does not deteriorate.
[0053] (5) Due to the advantages (3) and (4), the rigidity of the
cylinder liner portion 21, which is independently formed, is easily
maintained.
[0054] (6) Since the area of the receiving surface 32a is increased
by forming the flange 36 at the top surface portion of the cylinder
outer wall portion 32, the upper deck portion 22 is stably
fixed.
[0055] (7) Since through holes are formed in the upper deck portion
22 to connect fluid passages formed in the cylinder head 2 with
fluid passages formed in the outer block 30, the fluid passages in
the cylinder head 2 and the outer block 30 are connected to each
other with a simple structure. Also, forming such through holes in
the upper deck portion 22 increases the area of the receiving
surface 32a. This, in turn, permits the inner block 20 to be stably
fixed to the outer block 30.
[0056] The above embodiment may be modified as follows.
[0057] In the illustrated embodiment, the inner block 20 and the
outer block 30 are made of an aluminum alloy or a magnesium alloy.
However, the material may be arbitrarily changed. For example, one
or both of the inner block 20 and the outer block 30 may be made of
cast iron. If the overall mechanical strength of the cylinder block
3 is ensured by the outer block 30, the inner block 20 may be made
of a material the strength of which is not easily improved. For
example, ceramics or sintered metal may be used. Also, the outer
block 30, which is not directly exposed to combusted gas in the
cylinders, may be made of material having a relatively low heat
resistance. For example, resin may be used.
[0058] In the illustrated embodiment, the inner block 20 and the
outer block 30 are formed through die casting. However, the blocks
20, 30 may be formed through method other than die casting.
[0059] In the illustrated embodiment, the protective films are
formed on the wall surfaces of the cylinder bores 5. However, such
treatment does not need to be applied. For example, if separately
formed cylinder liners may be attached to the inner surfaces 23 of
the cylinder liner portion 21 or if the inner block 20 is made of a
material having a sufficient wear resistance, the base material may
be used to form the surfaces of the cylinder bores 5.
[0060] If the sealing property in the contacting surfaces of the
upper deck portion 22 and the receiving surface 32a and the sealing
property in the contacting surfaces of the outer circumferential
surface of the projection 25 and the lower portion of the inner
surface 35 are insufficient, a sealing structure such as an
application of a sealing agent or sealing member may be provided at
those contacting surfaces.
[0061] In the illustrated embodiment, the projection 25 is formed
at the lower portion of the cylinder liner portion 21, and the
outer circumference surface of the projection 25 contacts the inner
surface 35 of the cylinder outer wall portion 32 to support the
cylinder liner portion 21 from below. A projection like the
projection 25 may be formed on the inner surface 35 of the cylinder
outer wall portion 32. In this case also, the cylinder liner 21 is
supported from below. This stably fixes the cylinder liner portion
21.
[0062] A supporting surface for supporting the lower end of the
cylinder liner portion 21 may be integrally formed with the
cylinder outer wall portion 32, and the cylinder liner portion 21
may be supported by the supporting surface from below. In this case
also, the cylinder liner portion 21 is stably fixed.
[0063] If the rigidity of the cylinder liner portion 21 is secured
by fixing the upper deck portion 22, a supporting portion for
supporting the lower portion of the cylinder liner 21 does not need
to be formed in the cylinder outer wall portion 32. In this case,
however, a sealing structure needs to be provided to prevent
coolant from leaking from the water jacket 6 at the lower portion
of the cylinder liner portion 21.
[0064] In the illustrated embodiment, the crankcase portion 31 and
the cylinder outer wall portion 32 are integrated to form the outer
block 30. However, the crankcase portion 31 and the cylinder outer
wall portion 32 may be formed separately. In this case, the
cylinder block 3 includes separately formed three pieces, which are
the inner block 20, the cylinder outer wall portion 32, and the
crankcase portion 31. This structure increases the number of the
components and the number of the dies, but is advantageous in a
case where the integrally formed crankcase portion 31 and the
cylinder outer wall portion 32 have complicated shapes and are thus
difficult to mold.
[0065] In the illustrated embodiment, the present invention is
applied to the water-cooled engine having in-line four cylinders.
However, the present invention may be applied to any type of
water-cooled engine as long as a cylinder block in which a water
jacket is defined about cylinder bores is assembled with a cylinder
head.
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