Internal-combustion engines – Particular piston and enclosing cylinder construction – Cylinder detail
Reexamination Certificate
2000-11-08
2001-10-09
McMahon, Marguerite (Department: 3747)
Internal-combustion engines
Particular piston and enclosing cylinder construction
Cylinder detail
Reexamination Certificate
active
06298818
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a cylinder liner and a cylinder block, which are used in an engine of a vehicle, and a method of manufacturing them.
A conventional cylinder block of an engine is shown in
FIGS. 7 and 8
. The cylinder block
1
includes: cylinder liners
2
made of cast iron; an aluminium block
3
enclosing the cylinder liners
2
; and water paths
4
, through which cooling water is introduced.
Generally, cold shut and scattered structures in aluminium occur defects in aluminium-casted products.
In the case of the cylinder block
1
, rate of contraction of aluminium is very high when aluminium is cooled to solidify. On the other hand, the cylinder liners
2
, which have been casted with cast iron, are not thermally influenced, so that great residual stress left in the aluminium portions.
In a portion “A” (see FIG.
8
), which is between the adjacent cylinder liners
30
, the aluminium contracts in directions of arrows. If there is an inner defect in the portion “A”, the inner defect is apt to make a crack therein. When the aluminium is cooled and contacts, the residual stress, which is caused by the contraction of the aluminium, works to various portions. Especially, the stress works to the portion “A” and portions “B” when the cylinder liners
2
are machined or pistons slide in the cylinder liners, so that the cracks are apt to be formed in the portions “A” and “B”.
To prevent forming the cracks, the portions “A” and “B” are made thicker, but this countermeasure makes the cylinder block
1
bigger and heavier.
No alloy is formed between the cast iron of the cylinder liners
2
and the aluminium of the alminium block
3
, so the cylinder liners
2
and the aluminium block
3
cannot tightly adhered. There are many minute clearances there between. With the minute clearances, cooling efficiency of the cooling water must be lower.
To tightly adhere the cylinder liners
2
and the aluminium block
3
, many ring projections are formed in outer circumferential faces of the cylinder liners
2
.
The cylinder liner
2
having the ring projections is casted in a splittable molding unit, etc.
An example of the splittable molding unit is shown in FIG.
9
.
The splittable molding unit includes a lower mold
10
and an upper mold
12
. A core
14
is sandwitched between the molds
10
and
12
, so that a casting space is formed between an outer circumferential face of the core
14
and inner faces of the molds
10
and
12
. Molten metal is introduced into the casting space. Note that, symbol “P.L” indicates parting faces of the molds
10
and
12
.
Another splittable molding unit is shown in FIG.
10
.
The splittable molding unit includes a lower mold
10
, which has an island section
10
a
, and an upper mold
12
, which has an island section
12
a
. A casting space is formed between outer circumferential faces of the island sections
10
a
and
12
a
and an inner face of the lower mold
10
. Molten metal is introduced into the casting space. Note that, symbol “P.L” indicates parting faces of the molds
10
and
12
.
In the case of the splittable molding unit shown in
FIG. 9
, ring grooves, which correspond to the ring projections, are formed in the inner faces of the molds
10
and
12
. The ring projections can be formed in the cylinder liner by employing the splittable molding unit, and the cylinder liner can be easily taken out from the molds.
However, many flashes are formed in an outer circumferential face of the cylinder liner along the parting faces “P.L”. Namely, the flashes are formed between the ring projections, so it is difficult to perfectly remove the flashes. If the flashes are left, the residual stress works to the aluminium block, which encloses the cylinder liners, and cracks are apt to be formed in the aluminium block.
On the other hand, in the case of the splittable molding unit shown in
FIG. 10
, outer diameter of the cylinder liner is not fixed in the axial direction because angle for drafting the cylinder liner from the molds must be required. Therefore, the casted cylinder liner must be machined so as to have fixed outer diameter and form the ring projections.
By forming the ring projections in the cylinder liner, adhesion between the cylinder liner and the aluminium block is improved. However, the contraction rate of the aluminium in the circumferential direction of the cylinder liner is still great; the contraction rate of the aluminium in the axial direction of the cylinder liner is not so great. So, the residual stress still damages the aluminum block when the aluminium is cooled.
SUMMARY OF THE INVENTION
The present invention is invented to solve the above described disadvantages. An object of the present invention is to provide a cylinder liner, which is capable of being tightly adhered to an aluminium block, and a method of manufacturing the cylinder liner. Another object is to provide a hard compact cylinder block, which is capable of preventing cracks and reducing size and weight, and a method of manufacturing the cylinder block.
To achieve the objects, the present invention has following structures.
The cylinder liner, which is made of cast iron and formed into a cylindrical shape, comprises:
a slender section being provided in a middle portion of the cylinder liner, wherein outer diameter of the cylinder liner is gradually made greater toward both end sections of the cylinder liner from the slender section; and
a plurality of projected lines being formed on an outer circumferential face of the cylinder liner with regular separations and extended in the axial direction thereof.
Since the outer diameter of the middle slender section is shorter than that of other portions, the cylinder liner can securely stay in a cylinder block even if an external force in the axial direction, which is applied by a piston, etc., works to the cylinder liner. Namely, the adhesion between the cylinder liner and the cylinder block can be improved.
The projected lines extended in the axial direction improve strength of the cylinder liner. Therefore, the cylinder liner can be thinner and lighter.
The contraction of the aluminium in the circumferential direction, which occurs when the cylinder block is formed, can be uniformly limited by the projected lines, so that the residual stress in the contracted aluminium can be uniformly reduced. By reducing the residual stress, forming the cracks in the aluminium block can be prevented. Therefore, the aluminium block can be thinner; namely the compact and light cylinder block can be realized. When the aluminium contracts, the projected lines are tightly pinched by the aluminium, so that the adhesion between the cylinder liner and the cylinder block can be improved. Further, contact area between the two can be broader, so that the cooling efficiency of the cooling water can be improved.
In the cylinder liner, a circular groove may be formed in the outer circumferential face of the slender section. With this structure, the aluminium engages with the circular groove, so that the cylinder liner can stand against the external force in the axial direction.
In the cylinder liner, the outer circumferential face of the cylinder liner may be a casting surface. Since the casting face is a rough surface, the adhesion between the cylinder liner and the cylinder block can be improved.
The method of manufacturing a cylinder liner of the present invention comprises the steps of:
providing a core, which is made by solidifying casting sand with binders in one of the molds;
combining the other mold, which has an island section, with the one mold so as to insert the island section into an inner space of the core and form a casting space between an outer circumferential face of the island section and an inner circumferential face of the core; and
filling the casting space with molten metal,
wherein the core comprises:
a slender section being provided in a middle portion of the core, wherein inner diameter of the core is gradually made greater toward both end sections of the core from the slender section; an
Koyama Shigeru
Oda Teruyuki
Jordan and Hamburg LLP
Kabushiki Kaisha Koyama
McMahon Marguerite
LandOfFree
Cylinder liner and cylinder block and method of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Cylinder liner and cylinder block and method of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cylinder liner and cylinder block and method of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2578082