Internal-combustion engines – Cooling – With jacketed head and/or cylinder
Reexamination Certificate
2001-03-05
2003-06-10
Kamen, Noah P. (Department: 3747)
Internal-combustion engines
Cooling
With jacketed head and/or cylinder
C123S193200
Reexamination Certificate
active
06575124
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cylinder block of a multi-cylinder engine, and in particular a cooling water passage arrangement for such engine.
2. Explanation of Related Art
According to a technique proposed up to now, a spacing between adjacent cylinder bores is narrowed in order to make the multi-cylinder engine compact and light. Or a cylinder bore is formed larger than the conventional one to reduce the thickness of a wall between adjacent bores as much as possible so as to increase the exhaust amount in an attempt to enhance the output of the engine. Further, the proposed technique forms a cooling water passage within the wall between adjacent bores. For example,
FIGS. 7
to
9
show a conventional technique proposed by an Assignee of the invention of the present application. Here,
FIG. 7
is a vertical sectional view of a cooling water passage formed within a wall between adjacent bores, which is an essential part of a multi-cylinder block.
FIG. 8
is a perspective view of a cylinder jacket core. FIG.
9
(A) is a perspective view of a water passage forming member made of metal sheets. FIG.
9
(B) is a plan view showing the water passage forming member filled with molding sand. FIG.
9
(C) is a front view showing the water passage forming member filled with molding sand.
The conventional technique was disclosed, for example, in Japanese Patent Public Disclosure No. 8-319881. As shown in
FIG. 7
, a water passage forming member
110
made of metal sheets is embedded at a head side portion of an inter-bore wall
4
of a multi-cylinder block
1
by a molding process to form a cooling water passage
10
. The metal sheet water passage forming member
110
comprises two molded metal sheet members joined to each other by welding or caulking as shown in FIG.
9
(A).
The cooling water passage
10
comprises a pair of left and right rising water passages
12
,
12
having lower portions provided with cooling water induction portions
13
,
13
, respectively, and a plurality of transverse water passages
15
,
15
provided in vertical and multiple stages for mutually communicating these rising water passages
12
,
12
as shown in FIG.
7
. Cooling water within left and right cylinder jackets
8
,
8
is introduced from the cooling water induction portions
13
,
13
to a head jacket
22
through the transverse water passages
15
,
15
and the rising water passages
12
,
12
to thereby cool the head side portion of the inter-bore wall
4
. A portion
11
of the water passage forming member
110
which does not form the cooling water passage
10
is welded to form a non-hollow portion. The metal sheet water passage forming member
110
is embedded into the inter-bore wall
4
by a molding process in the following manner.
As shown in FIGS.
9
(B) and
9
(C), there is preliminarily prepared a water passage forming member
110
filled with molding sand, which is attached to a position corresponding to an inter-bore wall of a jacket forming mold (not shown). The jacket forming mold is filled with molding sand under pressure by a core making machine to make a jacket core
30
as shown in FIG.
8
. As such, the metal sheet water passage forming member
110
is integrated into the core
30
. The metal sheet water passage forming member is employed because the conventional molding sand has insufficient flowability, filling ability and transverse rupture strength, and therefore is not suitable for forming the cooling water passage
10
.
Next, the jacket core
30
, a crank bore core (not shown), a cam balancer core (not shown) and the like are attached to a cylinder block forming metal mold (not shown), into which molten metal is poured. Then after the molten metal has been cooled, the sand is removed to finish the molding of the multi-cylinder block. As such, the metal sheet water passage forming member
110
is embedded into the inter-bore wall
4
by the molding process to form within the inter-bore wall
4
the cooling water passage
10
which communicates the cylinder jackets
8
with the head jacket
22
.
SUMMARY OF THE INVENTION
According to the conventional technique, the metal sheet water passage forming member
110
is embedded into the inter-bore wall
4
by a molding process. This entails the following problems.
The jacket core
30
is different from the metal sheet water passage forming member
110
in expansion coefficient, which sometimes results in causing the jacket core
30
to crack and deform after molten metal has been poured.
Further, the metal sheet water passage forming member
110
is apt to insufficiently join with the poured molten metal. This causes the inter-bore wall
4
to distort when working the cylinder bore to result in separating the water passage forming member and ultimately decreasing the cooling effect due to reduction of thermal conduction between the water passage forming member and the inter-bore wall.
An attempt to sufficiently secure the working strength of the inter-bore wall
4
so as to be able to resist the distortion of the cylinder bore caused when working it invites a necessity of increasing the minimum thickness of the inter-bore wall
4
. The sectional area of the cooling water passage
10
has to be decreased by an amount corresponding to the increase.
Then prior to the present invention, a trial was conducted to make the water passage forming member core of the molding sand which has been used up to now. But this molding sand is non-spherical and has a large spacing between sand particles to provide a bad filling ability and a weak mutual shape-retaining force. In consequence, in order to secure a strong mutual shape-retaining force and a desired transverse rupture strength, there is a need of enlarging the percentage content of a binder in the molding sand.
However, when the molding sand to make the water passage forming core has the percentage content of the binder enlarged, during the step of pouring the molten metal, if the binder vaporizes and splashes, it increases the generation of gas with the result of being apt to produce mold cavities. In addition, the water passage forming core has a smaller mass and calorific capacity than the other parts. Therefore, when the binder has vaporized and splashed, it extremely loses its shape-retaining force to collapse or the like due to pouring pressure and overheat, which eventually results in forming no water passage and causing, so-called, sand residue. In consequence, the molding sand is involved by the molding material and is seized onto the molded surface and the like to produce unuseful concave and convex portions which narrow the water passage. Additionally, water scale deposits on the concave and convex portions of an inner surface of the water passage to reduce the cooling efficiency.
The present invention provides a technique to form a cooling water passage by using a water passage forming core which is made of core sand to be mentioned later, instead of the conventional metal sheet water passage forming member, and has the following objects:
1. To solve the cracking or the like of a jacket forming core, attributable to the difference of expansion coefficient;
2. To solve a disadvantage of distorting the inter-bore wall when working the cylinder bore or the like;
3. To solve the problem of separation caused by the conventional technique and to enhance the cooling effect of the inter-bore wall;
4. To sufficiently secure the working strength of the cylinder bore and the sectional area of the cooling water passage; and
5. To solve the above-mentioned disadvantage which occurs when the water passage forming core is made of the conventionally used molding sand and to make a water passage forming core large in transverse rupture strength with a binder added in a small amount, thereby forming a highly accurate cooling water passage.
A cylinder block of a multi-cylinder engine as set forth in claim 1 has the following basic construction.
The multi-cylinder engine (E) has an inter-bore wall
4
whose head side portion is provided with a
Aketa Masahiro
Shimizu Yutaka
Uehara Takefumi
Yamada Shuichi
Bacon & Thomas PLLC
Kamen Noah P.
Kubota Corporation
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