BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] 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
[0002] 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.
[0003] 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.
[0004] 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.
[0005] 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.
[0006] 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
[0007] 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.
[0008] 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.
[0009] 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.
[0010] Here, the communication means may be one having only one communication path or one
having a plurality of communication paths.
[0011] 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.
[0012] 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.
[0013] 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.
[0014] The term "central portion" used in Claim 1 will be defined as follows:
[0015] 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.
[0016] 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.
[0017] 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.
[0018] 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.
[0019] 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.
[0020] 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.
[0021] 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.
[0022] 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.
[0023] 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.
[0024] 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.
[0025] 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.
[0026] 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.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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.
[0031] 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.
[0032] 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
[0033] 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
[0034] Embodiments of the present invention will now be described with reference to the
drawings. First, Embodiment 1 will be described.
(Embodiment 1)
[0035] 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.
[0036] 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.
[0037] 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.
[0038] 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).
[0039] 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.
[0040] 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.
[0041] 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.
[0042] 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.
[0043] 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.
[0044] 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.
[0045] 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.
[0046] 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.
[0047] 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.
[0048] 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.
[0049] 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.
[0050] 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.
[0051] 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.
[0052] 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.
[0053] 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.
[0054] 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.
[0055] 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.
[0056] 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.
[0057] 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.
[0058] 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)
[0059] 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.
[0060] 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.
[0061] 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.
[0062] 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.
[0063] 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.
[0064] 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)
[0065] 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.
[0066] 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.
[0067] 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.
[0068] 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.
[0069] 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.
[0070] 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.
[0071] 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.
[0072] 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.
[0073] 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.
[0074] 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.
[0075] 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.
[0076] 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.
[0077] 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.
[0078] 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.
[0079] 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.
[0080] 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.
1. A cylinder head cooling structure for an internal combustion engine in which a cooling
liquid is caused to flow from an inflow portion (30a, 30b, 31, 32a to 32d) to an outflow
portion (33) through a cooling liquid path (5) formed in the cylinder head of the
internal combustion engine equipped with a port row (10, 20) in which at least one
intake valve and at least one exhaust valve are arranged, so that the cylinder head
(1) heated by a combustion chamber is cooled,
characterized in that:
the cooling liquid path comprises an intake side cooling path (6) formed between an
intake port wall portion (11c to 14c) forming an intake port row and a cylinder head
peripheral wall portion (4), an exhaust side cooling path (8) formed between an exhaust
port wall portion (20c) forming an exhaust port row and a cylinder head peripheral
wall portion, and a central cooling path (7) formed between the intake port wall portion
and the exhaust port wall portion; and
a communication means (34a to 34c) 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 a low flow rate portion are formed in the central cooling
path through the intermediation of the communication means, and 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.
2. A cylinder head cooling structure for an internal combustion engine according to Claim
1, characterized in that the communication means have at least one of communication path communicating the
central cooling path with at least one of the intake side cooling path and the exhaust
side cooling path, a flow rate control portion (35a, 35b, 35) is provided 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.
3. A cylinder head cooling structure for an internal combustion engine according to Claim
2, characterized in that the inflow portion has a plurality of holes, at least one of which is provided in
a path which has the flow rate control portion and on the upstream side of the flow
rate control portion, and is an intermediate inflow portion allowing cooling liquid
to flow to the central cooling path through the communication path.
4. A cylinder head cooling structure for an internal combustion engine according to Claim
1, characterized in that the communication means have at least one of communication path communicating the
central cooling path with at least one of the intake side cooling path and the exhaust
side cooling path, a flow rate control portion (35a, 35b, 35) is provided at a position
on the upstream side of the communication path, 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.
5. A cylinder head cooling structure for an internal combustion engine according to any
one of Claims 2 through 4, characterized in that the flow rate control portion (35a, 35b, 35) consists of a protrusion extending from
one to the other of the intake port wall portion or the exhaust port wall portion
and the cylinder head peripheral wall portion so as to narrow the flow path.
6. A cylinder head cooling structure for an internal combustion engine in which a cooling
liquid is caused to flow from an inflow portion (30a, 30b, 31, 32a to 32d) to an outflow
portion (33) through a cooling liquid path (5) formed in the cylinder head of the
internal combustion engine equipped with a port row (10, 20) in which at least one
intake valve and at least one exhaust valve are arranged, so that the cylinder head
(1) heated by a combustion chamber is cooled,
characterized in that:
the cooling liquid path comprises an intake side cooling path (6) formed between an
intake port wall portion (11c to 14c) forming an intake port row and a cylinder head
peripheral wall portion (4), an exhaust side cooling path (8) formed between an exhaust
port wall portion (20c) forming an exhaust port row and a cylinder head peripheral
wall portion, and a central cooling path (7) formed between the intake port wall portion
and the exhaust port wall portion; and
a communication means (34a to 34c) 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.
7. A cylinder head cooling structure for an internal combustion engine according to Claim
6, characterized in that the communication means consists of a plurality of communication paths and with regard
to at least one of the plurality of communication paths, a flow rate control portion
(35a, 35b, 35) 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.
8. A cylinder head cooling structure for an internal combustion engine according to Claim
7, characterized in that the inflow portion has a plurality of holes, at least one of which is provided in
a path which has the flow rate control portion and on the upstream side of the flow
rate control portion, and is an intermediate inflow portion allowing cooling liquid
to flow to the central cooling path through the communication path.
9. A cylinder head cooling structure for an internal combustion engine according to Claim
6, characterized in that the communication means have at least one of communication path communicating the
central cooling path with at least one of the intake side cooling path and the exhaust
side cooling path, a flow rate control portion (35a, 35b, 35) is provided at a position
on the upstream side of the communication path, 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.
10. A cylinder head cooling structure for an internal combustion engine according to any
one of Claims 2 through 4, characterized in that the flow rate control portion (35a, 35b, 35) consists of a protrusion extending from
one to the other of the intake port wall portion or the exhaust port wall portion
and the cylinder head peripheral wall portion so as to narrow the flow path.
11. A cylinder head cooling structure for an internal combustion engine according to any
one of Claims 1 through 10, characterized in that the communication means consists of a plurality of communication paths, and that
the high flow rate portion starts from the downstream side of one of the communication
paths by the one communication path and a first flow rate control portion (35a, 35)
arranged on the downstream of the one communication path in the intake side cooling
path or the exhaust side cooling path, and ends on the upstream of another communication
path by the another communication path and a second flow rate control portion (35b,
35) arranged on the upstream side of the another communication path in the intake
side cooling path or the exhaust side cooling path.
12. A cylinder head cooling structure for an internal combustion engine according to Claim
11, characterized in that the first flow rate control portion (35) and the second flow rate control portion
(35) are identical.
13. A cylinder head cooling structure for an internal combustion engine according to Claim
11, characterized in that the inflow portion has a plurality of holes, and that some of these holes are arranged
between the first flow rate control portion (35a) and the second flow rate control
portion (35b).
14. A cylinder head cooling structure for an internal combustion engine according to any
one of Claims 11 to 13, characterized in that the inflow portion has a plurality of holes, and that a plurality of holes of these
holes provided in the intake side cooling path or the exhaust side cooling path are
all arranged on the upstream side of the second flow rate control portion (35b).
15. A cylinder head cooling structure for an internal combustion engine according to any
one of Claims 1 to 14, 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.
16. A cylinder head cooling structure for an internal combustion engine according to any
one of Claims 1 to 15, characterized in that the high flow rate portion accounts for the central portion, and the low flow rate
portion accounts for the end portions.