BACKGROUND OF THE INVENTION
1. Field of the Invention
-
The present invention relates to a cylinder head cooling
structure which causes cooling water to flow through a cooling water
path formed in the cylinder head of an internal combustion engine,
from an inflow portion to an outflow portion, thereby cooling the
cylinder head heated by a combustion chamber.
2. Description of the Related Art
-
The cylinder head of an internal combustion engine is provided
with a cooling water path for cooling against heating by the combustion
chamber. Usually, this cooling water path is formed such that cooling
water can flow around wall portions forming an intake port and an
exhaust port.
-
However, due to the restriction regarding the arrangement of
the intake port, the exhaust port, the fuel injection valve insertion
opening, etc., it is difficult to form a cooling water path having
a sufficient space between the intake port and the exhaust port.
Further, the inter-port portion between the intake port and the
exhaust port is particularly likely to attain high temperature.
Thus, when cooling water is caused to flow from the inflow portion
provided at one end of the cylinder head to the outflow portion
provided at the other end side thereof, a sufficient amount of cooling
water does not flow through the portion between the intake port
and the exhaust port, where the flow resistance is high, and it
is difficult to efficiently cool the inter-port portion, which is
subject to high temperature as stated above.
-
JP 5-86969 A, for example, discloses a structure in which,
in order to pass as much cooling water as possible through the portion
between the intake port and the exhaust port and to cool the inter-port
portion subject to high temperature, the cooling water path is divided
by a partition wall for each combustion chamber, and a protruding
wall for guiding the flowing direction of cooling water toward the
inter-port portion is formed at some midpoint of the partition wall.
-
However, in the above-mentioned structure, in which the cooling
water path is subdivided for each combustion chamber and in which
cooling water is guided to the inter-port portion subject to high
temperature, an excessive pressure loss is generally likely to occur,
and the structure becomes rather complicated. As a result, it is
highly possible that the supply of a sufficient amount of cooling
water to the inter-port portion will be impaired.
-
Further, as has been found out before the completion of the
present invention, in an internal combustion engine in which a
plurality of cylinders are arranged, there is relatively little
constraint in the portions near the ends of the cylinder row, so
that, as compared with the inter-port portions of the cylinders
situated at the positions other than the ends, the inter-port portions
at the ends are less subject to generation of thermal stress, and
it is not always necessary to pass a large amount of cooling water
therethrough. From this point of view also, it has been suggested
in completing the present invention that it is possible to distribute
a cooling water flow rate appropriately throughout the cylinder
head and to cool more efficiently the cylinder head central portion
which is subject to generation of large thermal stress.
SUMMARY OF THE INVENTION
-
In view of the above situation, it is an object of the present
invention to provide a cylinder head cooling structure for an internal
combustion engine which is capable of efficiently cooling the central
portion of the cylinder head and which appropriately distributes
the cooling water flow rate throughout the cylinder head, whereby
it is possible to achieve an improvement in cooling efficiency.
-
To achieve the above object, there is provided, in accordance
with the present invention, a cylinder head cooling structure for
an internal combustion engine in which a cooling liquid is caused
to flow from an inflow portion to an outflow portion through a cooling
liquid path formed in the cylinder head of the internal combustion
engine equipped with a port row in which at least one intake valve
and at least one exhaust valve are arranged, so that the cylinder
head heated by a combustion chamber is cooled, characterized in
that: the cooling liquid path comprising an intake side cooling
path formed between an intake port wall portion forming an intake
port row and a cylinder head peripheral wall portion, an exhaust
side cooling path formed between an exhaust port wall portion forming
an exhaust port row and a cylinder head peripheral wall portion,
and a central cooling path formed between the intake port wall portion
and the exhaust port wall portion; and a communication means
communicating the central cooling path with at least one of the
intake side cooling path and the exhaust side cooling path is formed,
that a high flow rate portion and a low flow rate portion are formed
in the central cooling path through the intermediation of the
communication means, and that the proportion of the longitudinal
length of the cylinder head of the high flow rate portion formed
in a central portion of the central cooling path with respect to
the longitudinal length of the cylinder head of the central portion
of the central cooling path is larger than the proportion of the
longitudinal length of the cylinder head of the high flow rate portion
formed in the end portions other than the central portion of the
central cooling path with respect to the length of the end portions
other than the central portion of the central cooling path.
-
The internal combustion engine equipped with a port row in
which at least one intake valve and at least one exhaust valve are
arranged includes a single-cylinder engine and a multi-cylinder
internal combustion engine, and also includes a two-valve system
in which each cylinder has one intake valve and one exhaust valve
and a four-valve system in which each cylinder has two intake valves
and two exhaust valves, etc.
-
Here, the communication means may be one having only one
communication path or one having a plurality of communication paths.
-
Then, in the central cooling path, the high flow rate portion
and the low flow rate portion are determined in correspondence with
upstream side and downstream side portions of the communication
path when there is only one communication path, and determined in
correspondence with each of the portion between adjacent
communication paths, the portion between the uppermost-stream side
communication path and the upstream end, and the portion between
the downmost-stream side communication path and the downstream end
when there are a plurality of communication paths.
-
In the case in which there are a plurality of communication
paths, when cooling liquid flows into the central cooling path from
the communication path on the upstream side of the portion between
adjacent communication paths, the portion between the communication
path into which cooling liquid flows and the adjacent communication
path is the high flow rate portion; when cooling liquid flows into
the central cooling path from the downmost-stream side communication
path, the portion between the downmost-stream side communication
path and the downstream end is the high flow rate portion; when
no cooling liquid flows into the central cooling path from the
communication path on the upstream side of the portion between
adjacent communication paths, the portion between the communication
path into which no cooling liquid flows and the adjacent communication
path is the low flow rate portion; and when no cooling liquid flows
into the central cooling path from the downmost-stream side
communication path, the portion between the downmost-stream side
communication path and the downstream end is the low flow rate portion.
-
Regarding the portion between the upstream end of the central
cooling path and the adjacent communication path, when cooling liquid
flows into the central cooling path from the communication path
adjacent to the upstream end, the portion between the upstream end
and the communication path is the low flow rate portion, and when
no cooling liquid flows into the central cooling path from the
communication path, the portion between the upstream end and the
communication path is the high flow rate portion.
-
The term "central portion" used in Claim 1 will be defined
as follows:
-
First, in the case of an engine with three or more cylinders
arranged in series, the central cooling path of the portion adjacent
to the cylinders other than those at the ends will be referred to
as the central portion.
-
For example, as described in relation to Embodiment 1, in the
case of an engine with four cylinders, the central cooling path
of the portion adjacent to the central two cylinders other than
those at the ends is the central portion.
-
In the case of Embodiment 2 shown in Fig. 3, which consists
of a four-valve type engine with two in-line cylinders in which
a communication path is formed between the two intake port wall
portions formed on the respective cylinders, the two end intake
ports of the four intake ports are excluded, and the central cooling
path of the portion adjacent to the remaining two central intake
ports is the central portion.
-
It is stated in Claim 1 that "the proportion of the longitudinal
length of the cylinder head of the high flow rate portion formed
in a central portion of the central cooling path with respect to
the longitudinal length of the cylinder head of the central portion
(37) of the central cooling path is larger than the proportion of
the longitudinal length of the cylinder head of the high flow rate
portion formed in the end portions other than the central portion
of the central cooling path with respect to the length of the end
portions other than the central portion of the central cooling path. "
This means that as in, for example, Embodiment 1, when all the central
portion of the central cooling path is a high flow rate portion,
and all the end portions other than the central portion of the central
cooling path are a low flow rate portion, "the proportion of the
longitudinal length of the cylinder head of the high flow rate portion
formed in the central portion of the central cooling path with respect
to the longitudinal length of the cylinder head of the central portion
(37) of the central cooling path" is "100%", and "the proportion
of the longitudinal length of the cylinder head of the high flow
rate portion formed in the end portions other than the central portion
of the central cooling path with respect to the length of the end
portions other than the central portion of the central cooling path"
is "0%"; the proportion of the longitudinal length of the cylinder
head of the high flow rate portion formed in the central portion
of the central cooling path with respect to the longitudinal length
of the cylinder head of the central portion of the central cooling
path is larger than the proportion of the longitudinal length of
the cylinder head of the high flow rate portion formed in the end
portions other than the central portion of the central cooling path
with respect to the length of the end portions other than the central
portion of the central cooling path.
-
Further, when the proportion of the longitudinal length of
the cylinder head of the high flow rate portion formed in the central
portion of the central cooling path with respect to the longitudinal
length of the cylinder head of the central portion of the central
cooling path is larger than the proportion of the longitudinal length
of the cylinder head of the high flow rate portion formed in the
end portions other than the central portion of the central cooling
path with respect to the length of the end portions other than the
central portion of the central cooling path, only a portion of the
central portion of the central cooling path may be the high flow
rate portion, or a portion of the end portions other than the central
portion of the central cooling path may be the high flow rate portion.
-
In this construction, there is formed a communication means
by means of which cooling liquid is guided to the central portion,
and, through this communication means, the cooling liquid flow rate
in the central portion is increased with respect to the end portions,
so that the flow resistance is high between the intake port and
the exhaust port and, further, it is possible to efficiently cool
the cylinder head central portion, which is subject to generation
of thermal stress.
-
Further, in this construction, for the end portions to which
it is not always necessary to supply a large amount of cooling liquid,
detouring to the intake side cooling path or the exhaust side cooling
path is possible through the communication means, whereby, regarding
the central cooling path with high flow resistance, it is possible
to chiefly cool the central portion, which is subject to generation
of thermal stress. That is, the central portion is efficiently cooled,
and the end portions which offer high flow resistance but do not
always require a large amount of cooling liquid are bypassed, whereby
in the cooling liquid path as a whole, it is possible to decrease
the pressure loss and increase the flow rate. Thus, the cooling
water flow rate is appropriately distributed throughout the cylinder
head, thereby making it possible to provide a cylinder head cooling
structure for an internal combustion engine capable of enhancing
cooling efficiency.
-
Preferably, the present invention may provide the cylinder
head cooling structure for an internal combustion engine is
characterized in that the high flow rate portion accounts for the
central portion, and the low flow rate portion accounts for the
end portions.
-
In this construction, the central portion, which is subject
to generation of thermal stress, can be efficiently cooled and,
further, the cooling liquid flow rate is appropriately distributed
throughout the cylinder head, whereby it is possible to provide
a cylinder head cooling structure for an internal combustion engine
with enhanced cooling efficiency.
-
Preferably, the present invention may provide a cylinder head
cooling structure for an internal combustion engine in which a cooling
liquid is caused to flow from an inflow portion to an outflow portion
through a cooling liquid path formed in the cylinder head of the
internal combustion engine equipped with a port row in which at
least one intake valve and at least one exhaust valve are arranged,
so that the cylinder head heated by a combustion chamber is cooled,
characterized in that: the cooling liquid path comprising an intake
side cooling path formed between an intake port wall portion forming
an intake port row and a cylinder head peripheral wall portion,
an exhaust side cooling path formed between an exhaust port wall
portion forming an exhaust port row and a cylinder head peripheral
wall portion, and a central cooling path formed between the intake
port wall portion and the exhaust port wall portion; and a
communication means communicating the central cooling path with
at least one of the intake side cooling path and the exhaust side
cooling path is formed, a high flow rate portion and two low flow
rate portions are formed in the central cooling path through the
intermediation of the communication means, and the high flow rate
portion and two low flow rate portions arranged in order of the
low flow rate portion, the high flow rate portion, the low flow
rate portion from upstream toward downstream of the central cooling
path.
-
Preferably, the present invention may provide the cylinder
head cooling structure for an internal combustion engine is
characterized in that regarding at least one of the plurality of
communication paths constituting the communication means, a flow
rate control portion is provided in the intake side cooling path
or the exhaust side cooling path communicating with the central
cooling path through the communication path at a position on the
downstream side of the communication path, so that cooling liquid
is caused to flow into the central cooling path through the
communication path, forming the high flow rate portion on the
downstream side of the communication path of the central cooling
path.
-
In this construction, it is possible to achieve the same effect
as that of the other aspects of the invention with a simple
construction in which a flow rate control portion is provided at
some midpoint of the intake side cooling path or the exhaust side
cooling path communicating with the central cooling path. Regarding
the flow rate control portion, there is no particular restriction
in configuration and it may be formed, for example, by causing a
part of the port wall portion or the cylinder head peripheral wall
portion to protrude, or providing at some midpoint of the cooling
path a portion separate from the wall portion which narrows the
flow path; various designs are possible which narrow or cut off
the cooling path.
-
Preferably, the present invention may provide the cylinder
head cooling structure for an internal combustion engine is
characterized in that a flow rate control portion is provided in
at least one of the intake side cooling path and the exhaust side
cooling path, so that a high flow rate portion is formed in the
central cooling path, and one of the plurality of communication
paths constituting the communication means is provided on the
downstream side of the flow rate control portion, so that cooling
liquid in the central portion is caused to flow into the communication
path, forming a low flow rate portion on the downstream side of
the communication path of the central cooling path.
-
In this construction, cooling liquid is reliably caused to
flow through the central portion, which is subject to generation
of thermal stress, and it is possible to easily realize the bypassing
of the end portions, which offer high flow resistance but do not
always require a large amount of cooling liquid. Thus, the central
portion of the cylinder head can be efficiently cooled, and further,
the cooling liquid flow rate is appropriately distributed throughout
the cylinder head, whereby it is possible to provide a cylinder
head cooling structure for an internal combustion engine which can
attain an enhancement in cooling efficiency.
-
Preferably, the present invention may provide the cylinder
head cooling structure for an internal combustion engine is
characterized in that the inflow portion has a plurality of holes,
at least one of which is provided on the upstream side of the flow
rate control portion, and is an intermediate inflow portion forming
a flow path allowing cooling liquid to flow to the central cooling
path through the communication path.
-
In this construction, by providing an intermediate inflow
portion on the upstream side of the flow rate control portion, it
is possible to more effectively urge cooling liquid to flow toward
the central portion through the communication path. Thus, as
compared with the other construction, it is possible to cool the
central portion of the cylinder head more efficiently.
-
Preferably, the present invention may provide the cylinder
head cooling structure for an internal combustion engine is
characterized in that the cylinder head is applied to an internal
combustion engine in which each combustion chamber has two intake
ports and two exhaust ports and in which not less than three cylinders
are arranged.
-
In this construction, even in the case of a cylinder head for
an internal combustion engine with a large number of intake ports
and exhaust ports, such as a four-valve type one with not less than
three cylinders, it is possible to efficiently cool the central
portion of the cylinder head; further, the cooling liquid flow rate
is appropriately distributed throughout the cylinder head, whereby
it is possible to provide a cylinder head cooling structure for
an internal combustion engine with enhanced cooling efficiency.
BRIEF DESCRIPTION OF THE DRAWINGS
-
In the accompanying drawings:
- Fig. 1 is a horizontal sectional view of a cylinder head of
an internal combustion engine according to Embodiment 1 of the present
invention;
- Fig. 2 is a horizontal sectional view of a cylinder head of
an internal combustion engine according to Embodiment 2 of the present
invention; and
- Fig. 3 is a horizontal sectional view of a cylinder head of
an internal combustion engine according to Embodiment 3 of the present
invention.
-
DESCRIPTION OF THE PREFERRED EMBODIMENTS
-
Embodiments of the present invention will now be described
with reference to the drawings. First, Embodiment 1 will be
described.
(Embodiment 1)
-
Fig. 1 is a horizontal sectional view of the cylinder head
1 of an internal combustion engine according to Embodiment 1 as
seen from the opposite side to the cylinder block (not shown), that
is, as seen from above. The cylinder head 1 is applied to a four-valve
type internal combustion engine with four in-line cylinders. The
cylinder head 1 is formed as an integral unit in the form of a casting
of aluminum alloy.
-
The cylinder head 1 has two intake ports for each cylinder:
intake ports 11a and 11b, 12a and 12b, 13a and 13b, and 14a and
14b, and has two exhaust ports for each cylinder: exhaust ports
21a and 21b, 22a and 22b, 23a and 23b, and 24a and 24b. In the intake
ports and exhaust ports, there are respectively arranged intake
valves and exhaust valves (not shown). All the intake ports and
exhaust ports are respectively arranged in a row, forming an intake
port row 10 and an exhaust port row 20. The intake port row 10 and
the exhaust port row 20 are adjacent to each other. In the following
description, all the intake ports of the intake port row 10 will
also be collectively referred to as the intake ports 10, and all
the exhaust ports of the exhaust port row 20 will also be collectively
referred to as the exhaust ports 20.
-
Regarding the intake ports 10, they are formed by intake port
wall portions 11c, 12c, 13c, and 14c, each of which integrally forms
two ports for each cylinder, and regarding the exhaust ports 20,
they are formed by an exhaust port wall portion 20c which integrally
forms all the exhaust ports 21a through 24b. The intake ports 10
and exhaust ports 20 thus formed are open on the lower side in direction
of combustion chambers (not shown). These ports are formed through
punching by means of cores when forming the cylinder head 1 by casting
or the like.
-
Between the paired intake ports and on the side facing the
exhaust port row 20, the intake port wall portions 11c, 12c, 13c,
and 14c respectively have fuel injection valve insertion holes 11d,
12d, 13d, and 14d. These fuel injection valve insertion holes 11d
through 14d are formed by machining so as to open at the centers
of the cylinders (not shown).
-
Then, between a cylinder head peripheral wall portion 4,
surrounding the intake ports 10 and the exhaust ports 20 and
constituting the contour of the cylinder head 1, and the periphery
of the intake port wall portions 11c through 14c and of the exhaust
port wall portion 20c, there is formed a cooling water path 5 serving
as a cooling liquid path for cooling the cylinder head 1 heated
by the combustion chambers (not shown). The cooling water path 5
is formed through punching by means of a core when forming the cylinder
head 1 by casting or the like; the formation process is effected
such that a part of the intake port wall portions or of the exhaust
port wall portion is connected with the cylinder head peripheral
wall portion 4. In the cylinder head 1 shown in Fig. 1, an example
is shown in which the exhaust port wall portion 20c is connected
to the peripheral wall portion 4.
-
The cooling water path 5 is equipped with an intake side cooling
path 6 formed between the intake port wall portions 11c through
14c and the cylinder head peripheral wall portion 4, an exhaust
side cooling path 8 formed between the exhaust port wall portion
20c and the cylinder head peripheral wall portion 4, and a central
cooling path 7 formed between the intake port wall portions 11c
through 14c and the exhaust port wall portion 20c.
-
As for the cooling liquid, cooling water is caused to flow
through the cooling water path 5 formed as described above, from
inflow portions to outflow portions, whereby the cylinder head 1
is cooled. There are provided a plurality of inflow portions: intake
side inflow portions 30a and 30b provided in the vicinity of an
intake port 11a that is on the uppermost stream side of the intake
side cooling path 6 or the central cooling path 7, an exhaust side
inflow portion 31 provided in the vicinity of the exhaust port 21a
on the uppermost stream side of the exhaust side cooling path 8,
and intermediate inflow portions 32a, 32b, 32c, and 32d described
below for causing cooling water to flow in at midpoints in the intake
side cooling path 6. These inflow portions are formed as holes
communicating with cooling passages formed in the cylinder block
(not shown). Regarding an outflow portion 33, it is formed at the
position substantially on the downmost-stream side of the intake
side cooling path 6 so as to form in a part of the cylinder head
peripheral wall portion 4 a hole for communication with the exterior.
Note that, apart from the cooling water, the cooling liquid may
be some other cooling liquid, such as cooling oil.
-
Then, between the central cooling path 7 and the intake side
cooling path 6, there are provided a plurality of communication
passages formed so as to be narrow between the intake port wall
portions and adapted to communicate the central cooling path 7 with
the intake side cooling path 6. That is, a communication path 34a
is formed between the intake port wall portions 11c and 12c, a
communication path 34b is formed between the wall portions 12c and
13c, and a communication path 34c is formed between the wall portions
13c and 14c.
-
Further, at midpoints of the intake side cooling path 6
communicating with the central cooling path 7, there are provided
a plurality of flow rate control portions. The flow rate control
portions restrain inflow of cooling water into the intake side cooling
path 6, and are formed so as to protrude from the cylinder head
peripheral wall portion 4 toward the intake port wall portion. That
is, in the cylinder head 1 shown in Fig. 1, flow rate control portions
35a and 35b are formed so as to partly protrude from the cylinder
head peripheral wall portion 4 respectively toward the portions
between paired intake ports of the intake port wall portions 12c
and 13c.
-
In the vicinity of the flow rate control portions 35a and 35b,
there are provided the intermediate inflow portions 32b through
32d as described above and further, in the vicinity of the intake
port 11b, the intermediate inflow portion 32a is provided. That
is, the intermediate inflow portion 32a is provided at the position
where cooling water comes out from the upstream side of the
communication path 34a; the intermediate inflow portion 32b is
provided somewhat nearer to the upstream side than the flow rate
control portion 35a and in the vicinity of the intake port 12a;
the intermediate inflow portion 32c is provided on the downstream
side of the flow rate control portion 35a and on the upstream side
of the communication path 34b; and the intermediate inflow portion
32d is provided on the upstream side of the flow rate control portion
35b and in the vicinity of the intake port 13a. These inflow portions
cause inflow such that cooling water comes out at midpoints of the
intake side cooling path 6.
-
The cooling structure for the cylinder head 1 is as described
above. Next, the cooling water flowing condition and the cooling
action in this cylinder head 1 will be described.
-
First, cooling water flows into the cylinder head 1 from the
inflow portions. As described above, there are provided a plurality
of inflow portions; of these, cooling water flows in mainly from
the intake side inflow portions 30a and 30b and the exhaust side
inflow portion 31 rather than from the intermediate inflow portions
32a through 32d. Of course, cooling water does flow in from the
intermediate inflow portions 32a through 32d, too.
-
The cooling water flowing in from the intake side inflow portion
30a flows mainly along the intake side cooling path 6. The flowing
direction is indicated by the arrow A2. A part of the cooling water
flowing in from the intake side inflow portion 30b flows toward
the central cooling path 7 as indicated by the arrow A1. However,
in the central flow path 7, the flow passage space is small and
the flow resistance is high, so that, as compared with the intake
side cooling path 6, it does not easily allow cooling water to flow
in. The remain portion of the cooling water flowing in from the
intake side inflow portion 30b joins the cooling water flowing in
from the intake side inflow portion 30a and flows also into the
intake side cooling path 6. It is to be noted that there is provided
not only the intake side inflow portion 30a but also the intake
side inflow portion 30b, whereby the inflow to the central cooling
path 7 is promoted. In order that the structures, etc. of the cooling
paths may be easily understood, the dimensions and configurations
as given in Fig. 1 are somewhat different from the actual ones.
-
The cooling water flowing in from the intake side inflow portion
30a flows in the direction of the arrow A2, and joins at some midpoint
the cooling water flowing in from the intermediate inflow portion
32a and further flows toward the downstream side. On the downstream
side of the intake side cooling path 6, there is provided the flow
rate control portion 35a, and the pressure loss of a flow resistance
portion 6b constituting a flow path formed between the flow rate
control portion 35a and the intake port wall portion 12c is large,
so that the inflow of cooling water from the upstream side into
a flow path 6a constituting the intake side cooling path 6 adjacent
to the intake port 12a is restrained.
-
And, cooling water also flows in from the intermediate inflow
portion 32b situated on the upstream side of the flow rate control
portion 35a, so that the inflow of cooling water from the upstream
side into the flow path 6a is restrained. Most of the cooling water
flowing in from the intermediate inflow portion 32b is caused to
flow in such a direction that the flow resistance on the opposite
side to the flow resistance portion 6b on the downstream side is
low, that is, in the direction of the arrow A6.
-
In this way, the inflow into the flow path 6a is restrained,
and the cooling water flowing from the upstream side and the cooling
water flowing in from the intermediate inflow portion 32a join
together and flow into the communication path 34a. The cooling water
flowing into the communication path 34a flow into the central cooling
path 7 as indicated by the arrow A5 after passing the communication
path 34a. At this time, it joins the cooling water coming from the
upstream side of the central cooling path 7 in the direction of
the arrow A3. Thus, the portions of cooling water flowing in the
directions of the arrows A3 and A5 and joining together flow into
a flow path 7a constituting the central cooling path 7 formed by
the intake port wall portion 12c and the exhaust port wall portion
20c.
-
Together with a flow path 7b described below, this flow path
7a forms the portion situated at the center of the port row
(hereinafter referred to as "central portion 37"), which is a portion
subject to generation of excessive thermal stress. Thus, due to
the fact that it is possible to realize a structure promoting cooling
water flow toward the flow path 7a as described above, a high flow
rate portion where plenty of cooling water flows is formed in the
flow path 7a, that is, in the central portion 37, and it is possible
to efficiently cool the central portion 37, thereby restraining
generation of excessive thermal stress. As will be described below,
this high flow rate portion is formed in the central portion 37
consisting of the flow paths 7a and 7b.
-
The cooling water flowing into the flow path 7a from the
directions of the arrows A3 and A5 passes through the flow path
7a and flows in the direction of the arrow A7, and joins the cooling
water flowing in from the communication path 34b. The cooling water
flowing into the communication path 34b comes flowing from the
intermediate inflow portions 32c and 32d into the intake side cooling
path 6 . That is, due to the provision of the flow rate control portion
35b on the downstream side, most of the cooling water flowing in
from the intermediate inflow portion 32c flows in the direction
of the arrow A8, and, due to the provision of the flow rate control
portion 35b on the downstream side, most of the cooling water flowing
in from the intermediate inflow portion 32d flows in the direction
of the arrow A10 on the upstream side. In this way, the portions
of cooling water from the directions of the arrows A8 and A10 join
together and flow into the communication path 34b, and, after passing
the communication path 34b, flow in the direction of the arrow A9
before joining the cooling water from the direction of the arrow
A7.
-
In this way, the cooling water from the directions of the arrows
A7 and A9 flows into the flow path 7b formed between the intake
port wall portion 13c and the exhaust port wall portion 20c, that
is, into the rear half of the central portion 37, so that a high
flow rate portion where plenty of cooling water flows is also formed
in the rear half of the central portion 37, and, like the flow path
7a, the flow path 7b is also efficiently cooled, thereby preventing
the central portion 37 from attaining an excessively high temperature
and restraining generation of excessive thermal stress.
-
A part of the cooling water passing through the flow path 7b
flows downstream along the narrow central cooling path 7 (in the
direction of the arrow A13), whereas the remain thereof flows into
the communication path 34c (in the direction of the arrow A11) and
passes through the communication path 34c before flowing into the
intake side cooling path 6 (in the direction of the arrow A12),
whereby a low flow rate portion where a small amount of cooling
water flows is formed in a flow path 7c which is on the downstream
side of the communication path 34c and which is formed between the
intake port wall portion 14c and the exhaust port wall portion 20c.
The cooling water having flowed to the downstream side of the central
cooling path 7 by way of the flow path 7c flows out in the direction
of the arrow A14, and the cooling water having flowed downstream
through the intake side cooling path 6 flows out in the direction
of the arrow A15, and joins the cooling water coming from the exhaust
side cooling path 8 as described below before flowing out to the
exterior of the cylinder head 1 from the outflow portion 33.
-
In addition, regarding the cooling water flowing through the
exhaust side cooling path 8, the cooling water flowing in from the
inflow portion 31 situated on the uppermost stream side of the exhaust
side cooling path 8 first flows in the direction of the arrow B1,
and continues to flow downstream through the exhaust side cooling
path 8, that is, through the passage between the exhaust port wall
portion 20c and the cylinder head peripheral wall portion 4. Then,
it flows out in the direction of the arrow B2 from the exhaust side
cooling path 8, and joins the cooling water from the directions
of the arrows A14 and A15 before flowing out to the exterior from
the outflow portion 33. The cooling water having flowed out to the
exterior circulates through a radiator or the like (not shown),
and is used for the cooling of the cylinder head 1 again.
-
As described above, in the internal combustion engine cylinder
head cooling structure of Embodiment 1, the communication path 34a,
etc. through which cooling water is guided to the central portion
37 are formed; further, due to the flow rate control portion 35a,
etc., the inflow of cooling water into the intake side cooling path
6 is restrained, so that the inflow of cooling water into the central
portion 37 through the communication path 34a, etc. is promoted,
whereby a high flow rate portion is formed in the central portion
37 which offers high flow resistance between the intake port 10
and the exhaust port 20 and which is subject to generation of large
thermal stress, thereby making it possible to efficiently cool the
central portion 37.
-
Further, in this cylinder head 1, with respect to the flow
path 7c that is on one downstream side of the end portions other
than the central portion 37 of the central cooling path 7, in which
it is not always necessary to cause plenty of cooling water to flow,
bypassing to the intake side cooling path 6 is possible through
the communication path 34c, whereby, regarding the central cooling
path 7 involving high flow resistance, it is possible to chiefly
cool the central portion 37 that is subject to generation of large
thermal stress. That is, the central portion 37 is efficiently cooled,
and the end portions of the central cooling path 7, which offer
high flow resistance but do not always require plenty of cooling
water, are bypassed, and a low flow rate portion is formed in this
portion, making it possible to decrease the pressure loss of the
cooling water path 5 as a whole and increase the flow rate. Thus,
the cooling water flow rate is appropriately distributed throughout
the cylinder head, whereby it is possible to provide an internal
combustion engine cylinder head cooling structure capable of
enhancing cooling efficiency. Note that, in this cylinder head 1,
a low flow rate portion is formed not only in the flow path 7c on
the downstream side of the central portion 37 of the end portions
but also on the upstream side of the central cooling portion 37
constituting the other end portion, that is, in the flow path 7d
that is the central cooling path 7 formed between the intake port
wall portion 11c and the exhaust port wall portion 20c.
-
While in the structure of the cylinder head 1 the intake side
cooling path 6 communicates with the central cooling path 7 through
the communication path 34a, etc., this should not be construed
restrictively. In the cylinder head 1 of Fig. 1, it is also possible,
for example, to reverse the right and left sides. That is, it is
also possible to adopt a construction in which the intake port wall
portion is formed as an intake port wall portion integrally forming
all the intake ports, one end on the upstream side thereof being
connected to the cylinder head peripheral wall portion and the exhaust
side cooling path 8 communicating with the central cooling path
7. Further, it is also possible to adopt a construction in which
both the intake side cooling path 6 and the exhaust side cooling
path 8 communicate with the central cooling path 7.
(Embodiment 2)
-
Next, an internal combustion engine cylinder head cooling
structure according to Embodiment 2 will be described. Fig. 2 is
a schematic horizontal sectional view of an internal combustion
engine cylinder head 2 according to Embodiment 2 as seen from the
opposite side of the cylinder block (not shown), that is, from above.
In this cylinder head 2, the present invention is applied to a
two-valve type internal combustion engine with three in-line
cylinders. In the description of the embodiment, the components
having the same constructions and functions as those of the cylinder
head 1 are indicated by the same reference numerals, and a detailed
description of such components will be omitted as appropriate.
-
The cylinder head 2 is equipped with a cylinder head peripheral
wall portion 4, an intake port row 10 consisting of intake ports
11, 12, and 13, an exhaust port row 20 consisting of exhaust ports
21, 22, and 23, inflow portions 30a, 30b, and 31 provided on the
upstream side, and an outflow portion 33 provided on the downstream
side. The intake ports 11, 12, and 13 are formed by intake port
wall portions 11c, 12c, and 13c, respectively, and the exhaust ports
21 through 23 are formed integrally by an exhaust port wall portion
20c, one end on the upstream side of the exhaust port wall portion
20c being connected to the cylinder head peripheral wall portion
4. Then, an exhaust side cooling path 8 is formed between the cylinder
head peripheral wall portion 4 and the exhaust port wall portion
20c; an intake side cooling path 6 is formed between the cylinder
head peripheral wall portion 4 and the intake side port wall portions
11c through 13c; and a central cooling path 7 is formed between
the exhaust port wall portion 20c and the intake port wall portions
11c through 13c. Further, between the intake port wall portions,
there are provided communication paths communicating the central
cooling path 7 with the intake side cooling path 6. That is, a
communication path 34a is provided between the intake port wall
portions 11c and 12c, and a communication path 34b is provided between
the intake port wall portions 12c and 13c. Further, at some midpoint
of the intake side cooling path 6 and at a position corresponding
to the intake port wall portion 12c, there is provided a flow rate
control portion 35 which protrudes from the cylinder head peripheral
wall portion 4 so as to narrow the intake side cooling path 6.
-
The main directions in which cooling water flows in this
cylinder head 2 are indicated by arrows A1 through A8, B1 and B2.
Cooling water flowing in from inflow portions 30a and 30b flow in
the directions of the arrows A2 and A1. Note that plenty of cooling
water flows in the direction of the arrow A2, where the flow passage
is wide and there is less flow resistance. Due to the flow rate
control portion 35 situated on the downstream side, the inflow of
the cooling water flowing in the direction of the arrow A2 toward
the downstream side of the intake side cooling path 6 is restrained,
and most of the cooling water flows into the communication path
34a. Then, after flowing through the communication path 34a in the
direction of the arrow A3, it joins the cooling water from the
direction of the arrow A1 to flow in the direction of the arrow
A4. The portion where the flow in the direction of the arrow A4
is formed, that is, the portion of the central cooling path 7 which
is between the intake port wall portion 12c and the exhaust port
wall portion 20c (hereinafter referred to as "central portion 37"),
is the portion of the cylinder head 2 which is subject to generation
of large thermal stress; due to the fact that the flow in the direction
of the arrow A4 is promoted, a high flow rate portion where plenty
of cooling water flows is formed in the central portion 37, and
this central portion 37 is cooled efficiently.
-
A part of the cooling water having passed the central portion
37 flows to the downstream side of the central cooling path 7 (i.e.,
flows in the directions of the arrows A6 and A8), and the remain
thereof flows through the communication path 34b (in the direction
of the arrow A5) before flowing downstream through the intake side
cooling path 6 (in the direction of the arrow A7), whereby a low
flow rate portion is formed in one of the end portions other than
the central portion 37 of the central cooling path 7 situated on
the downstream side. Then, the portions of cooling water from the
directions of the arrows A8 and A7 join together to flow out to
the exterior from the outflow portion 33.
-
The cooling water flowing in from the inflow portion 31 flows
in the direction of the arrow B1 and flows downstream through the
exhaust side cooling path 8 (in the direction of the arrow B2) before
joining the cooling water from the directions of the arrows A6 and
A7 and flowing out to the exterior from the outflow portion 33.
-
As described above, also in the cylinder head 2 for a two-valve
type internal combustion engine with three cylinders, it is possible
to efficiently cool the central portion of the cylinder head; further,
the cooling water flow rate is appropriately distributed throughout
the cylinder head as a whole, whereby it is possible to provide
an internal combustion engine cylinder head cooling structure
capable of enhancing cooling efficiency.
(Embodiment 3)
-
Finally, an internal combustion engine cylinder head cooling
structure according to Embodiment 3 will be described. Fig. 3 is
a schematic horizontal sectional view of an internal combustion
engine cylinder head 3 according to Embodiment 3 as seen from the
opposite side of the cylinder block (not shown), that is, from above.
In this cylinder head 3, the present invention is applied to a
four-valve type internal combustion engine with two cylinders. Note
that, in the description of the embodiment, the components having
the same constructions and functions as those of the cylinder heads
1 and 2 are indicated by the same reference numerals, and a description
of such components will be omitted as appropriate.
-
The cylinder head 3 is equipped with a cylinder head peripheral
wall portion 4, an intake port row 10 consisting of intake ports
11, 12, 13 and 14, an exhaust port row 20 consisting of exhaust
ports 21, 22, 23 and 24, inflow portions 30a, 30b, and 31 provided
on the upstream side of a cooling path 5, and an outflow portion
33 provided on the downstream side of the cooling path 5. The intake
ports 11 through 14 are formed by intake port wall portions 11c,
12c, 13c and 14c, respectively, and the exhaust port wall portions
21 through 24 are formed integrally by an exhaust port wall portion
20c, one end on the upstream side of the exhaust port wall portion
20c being connected to the cylinder head peripheral wall portion
4. Note that, the intake ports 11 and 12 and the exhaust ports 21
and 22, and the intake ports 13 and 14 and the exhaust ports 23
and 24 correspond to one cylinder, respectively.
-
Then, between the cylinder head peripheral wall portion 4 and
the exhaust port wall portion 20c, there is formed an exhaust side
cooling path 8; between the cylinder head peripheral wall portion
4 and the intake side port wall portions 11c through 14c, there
is formed an intake side cooling path 6; and, between the exhaust
port wall portion 20c and the intake port wall portions 11C through
14c, there is formed a central cooling path 7. Further, between
the intake port wall portions, there are provided communication
paths communicating the central cooling path 7 with the intake side
cooling path 6. That is, a communication path 34a is provided between
the intake port wall portions 11c and 12c, a communication path
34b is provided between the intake port wall portions 12c and 13c,
and a communication path 34c is provided between the intake port
wall portions 13c and 14c. Further, at midpoints of the intake side
cooling path 6 and at positions corresponding to the intake port
wall portions 12c and 13c, there are provided flow rate control
portions 35a and 35b which protrude from the cylinder head peripheral
wall portion 4 so as to narrow the intake side cooling path 6.
-
The main directions in which cooling water flows in this
cylinder head 3 are indicated by arrows A1 through A9, B1 and B2.
Cooling water flowing in from inflow portions 30a and 30b flow in
the directions of the arrows A2 and A1. Note that plenty of cooling
water flows in the direction of the arrow A2, where the flow passage
is wide and there is less flow resistance. Due to the flow rate
control portion 35a situated on the downstream side, the inflow
of the cooling water flowing in the direction of the arrow A2 toward
the downstream side of the intake side cooling path 6 is restrained,
and most of the cooling water flows into the communication path
34a. Then, after flowing through the communication path 34a in the
direction of the arrow A3, it joins the cooling water from the
direction of the arrow A1 to flow in the direction of the arrow
A4. Remain of the cooling water flows between the flow rate control
portion 35a and the intake port wall portion 12c, along the intake
side cooling path 6.
-
Further, on the downstream side of the flow rate control portion
35a, there is also provided the flow rate control portion 35b, so
that the inflow of cooling water into the intake side cooling path
6 in between is restrained. Thus most of the cooling water from
the direction of the arrow A4 flows in the direction of the arrow
A5. The portion where the flow in the direction of the arrow A4
is formed and the portion where the flow in the direction of the
arrow A5 is formed, that is, the portion of the central cooling
path 7 surrounded by the intake port wall portions 12c and 13c and
the exhaust port wall portion 20c (hereinafter referred to as the
"central portion 37"), is the portion of the cylinder head 3 which
is subject to generation of large thermal stress; through the
promotion of this cooling water flow, a high flow rate portion where
plenty of cooling water flows is formed in the central portion 37,
and this central portion 37 is cooled efficiently. That is, due
to the flow rate control portion 35a on the upstream side and the
flow rate control portion 35b on the downstream side, it is possible
to guide the cooling water such that sufficient cooling water flows
to the central portion 37.
-
A part of the cooling water having passed the central portion
37 flows to the downstream side of the central cooling path 7 (i.e.,
flows in the directions of the arrows A7 and A8), and the remain
thereof flows through the communication path 34c (in the direction
of the arrow A6) before flowing downstream through the intake side
cooling path 6 (in the direction of the arrow A9), whereby a low
flow rate portion is formed in one of the end portions other than
the central portion 37 of the central cooling path 7 situated on
the downstream side. Then the portions of cooling water from the
directions of the arrows A8 and A9 join together to flow out to
the exterior from the outflow portion 33.
-
The cooling water flowing in from the inflow portion 31 flows
in the direction of the arrow B1 and flows downstream through the
exhaust side cooling path 8 (in the direction of the arrow B2) before
joining the cooling water from the directions of the arrows A7 and
A9 and flows out to the exterior from the outflow portion 33.
-
As described above, also in the cylinder head 3 for a four-valve
type internal combustion engine with two cylinders, it is possible
to efficiently cool the central portion of the cylinder head; further,
the cooling water flow rate is appropriately distributed throughout
the cylinder head as a whole, whereby it is possible to provide
an internal combustion engine cylinder head cooling structure
capable of enhancing cooling efficiency.
-
The embodiments of the present invention are as described above.
The above embodiments, however, should not be construed
restrictively. For example, the following modifications are
possible.
- (1) While in the above embodiments the present invention is
applied to four-valve/four-cylinder, two-valve/three-cylinder,
and four-valve/two-cylinder internal combustion engines, this
should not be construed restrictively. The present invention is
applicable to any type of internal combustion engine as long as
it is equipped with a port row in which a plurality of intake valves
and exhaust valves are arranged.
- (2) While in the above embodiments each flow rate control
portion partly protrudes from the cylinder head peripheral wall
portion, this should not be construed restrictively. For example,
it is also possible to form the flow rate control portion as a
continuous portion extending along the cylinder head peripheral
wall portion or the port wall portion and having a length approximately
corresponding to the central portion of the central cooling path.
- (3) Regarding the communication paths, it is not always
necessary to provide a plurality of them; for example, when the
length of the port row in the valve arrangement direction is small,
it is possible to provide only one communication path guiding inflow
into the central cooling path on the upstream side thereof.
-
-
In the invention according to the present invention, the
communication means is formed, by means of which cooling liquid
is guided to the central portion, and, through this communication
means, the cooling liquid flowrate in the central portion is increased
with respect to the end portions, so that the flow resistance is
high between the intake port and the exhaust port and, further,
it is possible to efficiently cool the cylinder head central portion,
which is subject to generation of thermal stress.
-
Further, in this construction, for the end portions to which
it is not always necessary to supply a large amount of cooling liquid,
detouring to the intake side cooling path or the exhaust side cooling
path is possible through the communication means, whereby, regarding
the central cooling path with high flow resistance, it is possible
to chiefly cool the central portion, which is subject to generation
of thermal stress. That is, the central portion is efficiently cooled,
and the end portions which offer high flow resistance but do not
always require a large amount of cooling liquid are bypassed, whereby
in the cooling liquid path as a whole, it is possible to decrease
the pressure loss and increase the flow rate. Thus, the cooling
water flow rate is appropriately distributed throughout the cylinder
head, thereby making it possible to provide a cylinder head cooling
structure for an internal combustion engine capable of enhancing
cooling efficiency.
-
Since the high flow rate portion accounts for the central
portion, and the low flow rate portion accounts for the end portions,
the central portion, which is subject to generation of thermal stress,
can be efficiently cooled and, further, the cooling liquid flow
rate is appropriately distributed throughout the cylinder head,
whereby it is possible to provide a cylinder head cooling structure
for an internal combustion engine with enhanced cooling efficiency.
-
In the invention in which a flow rate control portion is provided
at some midpoint of the intake side cooling path or the exhaust
side cooling path communicating with the central cooling path, though
a simple construction, it is possible to achieve the same effect
as the invention in claim 1.
-
Since the flow rate control portion is provided in at least
one of the intake side cooling path and the exhaust side cooling
path, so that a high flow rate portion is formed in the central
cooling path, and the communication means consists of a plurality
of communication paths and one of the plurality of communication
paths is provided on the downstream side of the flow rate control
portion, so that cooling liquid in the central portion is caused
to flow into the communication path, forming a low flow rate portion
on the downstream side of the communication path of the central
cooling path, cooling liquid is reliably caused to flow through
the central portion, which is subject to generation of thermal stress,
and it is possible to easily realize the bypassing of the end portions,
which offer high low resistance but do not always require a large
amount of cooling liquid. Thus, the central portion of the cylinder
head can be efficiently cooled, and further, the cooling liquid
flow rate is appropriately distributed throughout the cylinder head,
whereby it is possible to provide a cylinder head cooling structure
for an internal combustion engine which can attain an enhancement
in cooling efficiency.
-
Since the inflow portion has a plurality of holes, at least
one of which is provided on the upstream side of the flow rate control
portion, and is an intermediate inflow portion forming a flow path
allowing cooling liquid to flow to the central cooling path through
the communication path, it is possible to more effectively urge
cooling liquid to flow toward the central portion through the
communication path. Thus, as compared with the other construction,
it is possible to cool the central portion of the cylinder head
more efficiently.
-
Since the cylinder head is applied to an internal combustion
engine in which each combustion chamber has two intake ports and
two exhaust ports and in which not less than three cylinders are
arranged, even in the case of a cylinder head for an internal
combustion engine with a large number of intake ports and exhaust
ports, such as a four-valve type one with not less than three cylinders,
it is possible to efficiently cool the central portion of the cylinder
head; further, the cooling liquid flow rate is appropriately
distributed throughout the cylinder head, whereby it is possible
to provide a cylinder head cooling structure for an internal
combustion engine with enhanced cooling efficiency.