Internal-combustion engines – Cooling – With jacketed head and/or cylinder
Reexamination Certificate
2000-08-30
2002-01-01
McMahon, Marguerite (Department: 3747)
Internal-combustion engines
Cooling
With jacketed head and/or cylinder
C123S193300
Reexamination Certificate
active
06334412
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a mono-block cylinder head structure of a water cooled engine, and more particularly, to a mono-block cylinder head structure of a water cooled engine wherein a mono-block cylinder head portion which constitutes a water cooled engine is provided with a reinforcing rib.
2. Description of the Related Art
In recent years, there have been adopted many mono-block cylinders for aircraft engines.
In producing the engine body, in general, as shown in
FIG. 6
, an engine body
43
is constituted by joining a cylinder block
40
and a cylinder head
41
with bolts through a cylinder head gasket
42
. In the figure, reference numeral
44
denotes a head cover, and reference numeral
45
denotes an oil pan.
The mono-block cylinder is made by integrally molding a cylinder portion and a cylinder head of a cylinder block, which obviates the need for a plurality of bolt boss portions, corresponding bolts and cylinder gaskets for joining the cylinder block and the cylinder head which are necessary when the cylinder block and the cylinder head are separated from each other. Thus, as it is possible to make the engine body lightweight, which is why such mono-block cylinders are much adopted, especially in aircraft engines.
In the mono-block cylinder head
46
of a water cooled engine, as shown in
FIG. 7
, a water jacket outer wall portion
50
is provided on a cylinder head portion
47
from an upper end of a cylinder wall portion
48
to a cylinder head ceiling portion
49
with a predetermined space between the cylinder wall portion
48
and the cylinder head ceiling portion
49
. A water jacket
51
is then formed with cooling liquid stored between the cylinder wall portion
48
and the cylinder head ceiling portion
49
.
In such a mono-block cylinder
46
, combustion load generated during combustion in a cylinder body
53
acts in concentration on a joint portion
52
between the cylinder head ceiling portion
49
and the cylinder wall portion
48
.
In order to avoid this situation there may be, for example, a method for enlarging a thickness of the above cylinder head ceiling portion
49
or the cylinder wall portion
48
, or for expanding a radius of curvature of the above joint portion
52
.
However, when the wall thickness is set large, the cylinder head portion
47
including the joint portion
52
shows a temperature increase during combustion because the cooling effect by the cooling liquid in the water jacket
51
is decreased. Consequently, such a temperature increase may bring about a loss in material strength of the joint portion
52
and induce non-uniformity of heat distribution in the cylinder head portion
47
, and reduce the strength of the cylinder head portion
47
itself.
Further, when the radius of curvature of the joint portion
52
is made larger, it is necessary to make an escape of the end portion of pistons larger to correspond to the inner shape of the joint portion
52
, thereby there was a possibility to lower a combustion efficiency and lower the engine performance such as fuel consumption, etc.
In particular, when the cylinder block is cast with aluminum alloy, the temperature of the combustion chamber side wall portion in the cylinder head portion
47
becomes 200° C. to 300° C. during combustion. However, since the strength of aluminum rapidly declines from about 150° C., the aforementioned condition becomes noticeable, such that some countermeasure has been desired.
SUMMARY OF THE INVENTION
In view of this, an object of the present invention is to provide a mono-block cylinder head structure of water cooled engine that makes it impossible to effectively prevent a reduction in strength of a joint portion due to a concentration of stress from a combustion load on the joint portion between a cylinder portion and a cylinder head ceiling portion without reducing the cooling efficiency by a water jacket.
Further, another object of the present invention is to provide a mono-block cylinder head structure of a water cooled engine which aims to alleviate uneven thermal stress by improving thermal uniformity in a cylinder body, while also enabling the cooling efficiency to be improved.
In order to solve the foregoing objects, in the invention, there is provided a mono-block cylinder head structure provided with a water jacket having a water jacket outer wall portion
14
covering a cylinder upper end portion
12
and a cylinder head ceiling portion
13
of a cooling-water type engine, comprising a reinforcing rib
19
, which can hold a load generated by combustion in a combustion chamber
18
formed in a cylinder
21
and which can release heat generated by combustion to the water jacket
11
, at a joint portion
16
between the cylinder upper end portion
12
and the cylinder head ceiling portion
13
.
Accordingly, in the invention, even when a combustion load is generated by combustion in the combustion chamber
18
formed in the engine cylinder
21
and acts upon the joint portion
16
between the cylinder upper end portion
12
and the cylinder head ceiling portion
13
, the reinforcing rib
19
which can hold the load generated by combustion enables the joint portion
16
to sufficiently withstand the generated stress, so that a loss in strength in the joint portion
16
can be prevented. Furthermore, as the heat generated in the combustion chamber
18
formed in the cylinder
21
can be radiated to the water jacket
11
, there is no loss in cooling effect by the water jacket
11
.
Consequently, in the invention, a loss in strength in the joint portion
16
between the cylinder upper end portion
12
and the cylinder head ceiling portion
13
can be effectively prevented without lowering the cooling efficiency by the water jacket
11
.
According to one form of the invention, there is provided a mono-block cylinder head structure of a water cooled engine provided with a water jacket
11
having a water jacket outer wall portion
14
covering the cylinder upper end portion
12
and the cylinder head ceiling portion
13
, comprising a reinforcing rib
19
, which is formed so as to be continuously rising from the cylinder upper end portion
12
at the joint portion
16
between the above cylinder upper end portion
12
and the cylinder head ceiling portion
13
in the water jacket
11
, for joining a space between the joint portion
16
and the water jacket outer side wall
14
.
Accordingly, in this form of the invention, when stress by combustion load generated in the combustion chamber
18
of the cylinder
21
has acted on the above joint portion
16
, the stress is retained by the joint portion
16
and the reinforcing rib
19
. Furthermore, the stress is input to the water jacket outer wall portion
14
through the reinforcing rib
19
and is hold also by the water jacket outer wall portion
14
. Accordingly, since it is possible to distribute and hold at the plural portions the stress generated by the combustion load, the stress caused by the combustion load does not concentrate on the joint portion
16
.
As a result, a loss of strength in the joint portion
16
can be effectively prevented.
Also, as the reinforcing rib
19
is joined to the water jacket outer wall portion
14
, it can effectively transfer the heat generated in the combustion chamber
18
to the water jacket
11
side without the heat remaining within the reinforcing rib
19
, and thus can prevent the cooling efficiency of the cylinder head
15
from being reduced.
In a yet another form of the invention, the reinforcing ribs
19
are disposed radially in a plane over the entire area in the peripheral direction of the combustion chamber
18
with predetermined intervals therebetween.
Accordingly, in this form of the invention, since the reinforcing ribs
19
are disposed radially in a plane over the entire area in the peripheral direction of the combustion chamber
18
with predetermined intervals therebetween, a plurality of radially disposed ribs
19
sustain the combustion load generated at the central porti
McMahon Marguerite
Oliff & Berridg,e PLC
Toyota Jidosha & Kabushiki Kaisha
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