阅读说明：本技术 水套 (Water jacket ) 是由 伊藤裕亮 山崎信 竹形徳之 大田笃志 小出景二郎 于 2021-03-16 设计创作，主要内容包括：本发明提供一种水套,能够通过进行高效的冷却来抑制爆震,并且防止水泵的损失恶化。作为本发明的水套的气缸盖内冷却液通路(30)具有：燃烧室壁,其形成气缸盖(3)的燃烧室(6)；进气口壁,其形成与燃烧室(6)相连的进气口(7)；排气口壁,其形成与燃烧室(6)相连的排气口(8a)；作为冷却液流路的主冷却液通路(31),其面向燃烧室壁、进气口壁和排气口壁,供冷却液流动；和多个第一突条部(101)和第二突条部(103),它们在主冷却液通路(31)内沿与在进气口壁和排气口壁之间流动的冷却液的流动方向垂直的方向延伸,第一突条部(101)和第二突条部(103)形成在比进气口壁及排气口壁中的至少一方与燃烧室壁的边界部靠燃烧室壁侧的位置。(The invention provides a water jacket which can restrain knocking through efficient cooling and prevent the loss deterioration of a water pump. An in-cylinder-head cooling liquid passage (30) as a water jacket of the present invention comprises: a combustion chamber wall forming a combustion chamber (6) of the cylinder head (3); an intake port wall forming an intake port (7) connected to the combustion chamber (6); an exhaust port wall forming an exhaust port (8a) connected to the combustion chamber (6); a main coolant passage (31) as a coolant flow path for flowing a coolant, facing the combustion chamber wall, the intake port wall and the exhaust port wall; and a plurality of first protruding strip portions (101) and second protruding strip portions (103) extending in the main coolant passage (31) in a direction perpendicular to the flow direction of the coolant flowing between the inlet wall and the outlet wall, the first protruding strip portions (101) and the second protruding strip portions (103) being formed at positions closer to the combustion chamber wall than a boundary portion between at least one of the inlet wall and the outlet wall and the combustion chamber wall.)

1. A water jacket, comprising:

a combustion chamber wall forming a combustion chamber of the cylinder head;

an intake port wall forming an intake port connected to the combustion chamber;

an exhaust port wall forming an exhaust port connected to the combustion chamber;

a coolant flow path for flowing coolant, facing the combustion chamber wall, the air inlet wall and the air outlet wall; and

a plurality of ridges extending in the coolant flow path in a direction perpendicular to a flow direction of the coolant flowing between the air inlet wall and the air outlet wall,

the protruding strip is formed at a position closer to the combustion chamber wall than a boundary portion between at least one of the intake port wall and the exhaust port wall and the combustion chamber wall.

2. The water jacket according to claim 1,

the protruding strip has a horizontal portion at a distal end in the protruding direction, and a retention portion that is recessed toward a base end side in the protruding direction is provided between the plurality of protruding strips.

3. The water jacket according to claim 2,

the projection is formed on the combustion chamber wall between the intake port wall and the exhaust port wall.

4. The water jacket according to claim 2 or 3,

the cylinder head is assembled on the cylinder block, and has a boundary part between a joint surface of the cylinder head and the cylinder block and a bottom surface of the air inlet wall, and a boundary part between the joint surface and a bottom surface of the exhaust port wall,

the protruding strip is formed at least at a boundary between the joint surface and the bottom surface of the exhaust port wall.

5. The water jacket according to claim 3,

the water jacket is used for a multi-cylinder internal combustion engine provided with a cylinder head having a plurality of exhaust ports and an exhaust gas collecting portion merging the exhaust ports,

the water jacket has a collecting portion coolant flow path that covers the exhaust collecting portion,

the cross-sectional area of the collecting section cooling liquid flow path is formed small, and the surface area of the collecting section cooling liquid flow path is formed large so that the flow speed of the cooling liquid flowing through the collecting section cooling liquid flow path is higher than the flow speed of the cooling liquid flowing through the cooling liquid flow path.

Technical Field

The present invention relates to a water jacket for cooling a cylinder head of an internal combustion engine.

Background

Conventionally, as a water jacket having a fin extending toward the center on a bottom wall of a water jacket of a cylinder head, there is known a water jacket including: a wall portion on the lower surface side of the cylinder head defining the water jacket portion is formed with a fin bulging and bent toward the cylinder center side and extending from one side to the other side of the cylinder head (see, for example, patent document 1). According to the water jacket of patent document 1, the heat radiation effect can be improved by the fins, and the coolant can be brought close to the center by the fins, so that the coolant can be prevented from stagnating at the end portions.

Documents of the prior art

Patent document

Patent document 1: japanese examined patent publication (Kokoku) No. 7-103828

Disclosure of Invention

Problems to be solved by the invention

A water jacket of a conventional cylinder head is set to form a uniform flow without stagnation in order to cool the cylinder head, and has an effect of improving combustion efficiency by suppressing knocking as one of its effects.

On the other hand, in recent years, the shape of the water jacket is complicated, and the coolant may be partially retained to inhibit cooling.

As a countermeasure against this, a fin-like projection shape is provided on the wall surface in the flow path to control the flow of the coolant and prevent stagnation, thereby improving the cooling performance by increasing the contact area. Further, the protrusion height exceeding the necessary height causes deterioration in formability of the water jacket core and castability of the cylinder head, and lowers productivity.

In view of the above problems, an object of the present invention is to provide a water jacket that can suppress knocking by performing efficient cooling and can prevent deterioration of the loss of a water pump.

Means for solving the problems

[1] In order to achieve the above object, a water jacket according to the present invention includes:

a combustion chamber wall forming a combustion chamber of the cylinder head;

an intake port wall forming an intake port connected to the combustion chamber;

an exhaust port wall forming an exhaust port connected to the combustion chamber;

a coolant flow path for flowing coolant, facing the combustion chamber wall, the air inlet wall and the air outlet wall; and

a plurality of ridges extending in the coolant flow path in a direction perpendicular to a flow direction of the coolant flowing between the air inlet wall and the air outlet wall,

the protruding strip is formed at a position closer to the combustion chamber wall than a boundary portion between at least one of the intake port wall and the exhaust port wall and the combustion chamber wall.

According to the present invention, the heat transfer efficiency can be improved by the ridge portions, and the cooling performance can be improved. Further, the wall surface rigidity is increased by the projected portions formed on the wall surface, and the heat transfer efficiency can be further improved by thinning the wall surface.

[2] In the present invention, it is preferable that the protruding strip has a horizontal portion at a distal end in the protruding direction, and a retention portion recessed toward a proximal end side in the protruding direction is provided between the plurality of protruding strips.

According to the present invention, it is possible to suppress an increase in pressure loss due to the formation of the protruding portions by the horizontal portion, and to improve heat transfer efficiency due to collision of the coolant with the protruding portions.

[3] In the present invention, it is preferable that the projection is formed on a wall of the combustion chamber between the intake port wall and the exhaust port wall.

According to the present invention, the rigidity around the combustion chamber can be improved by the protruding portions, and the combustion chamber wall can be made thin to improve the heat transfer efficiency.

[4] Further, in the present invention, it is preferable that the cylinder head is assembled to the cylinder block, and has a boundary portion between a joint surface of the cylinder head to the cylinder block and a bottom surface of the intake port wall and a boundary portion between the joint surface and a bottom surface of the exhaust port wall,

the protruding strip is formed at least at a boundary between the joint surface and the bottom surface of the exhaust port wall.

According to the present invention, the exhaust gas immediately downstream of the combustion chamber can be cooled, and the exhaust gas can be efficiently cooled. In addition, the cooling of the periphery of the valve seat of the cylinder head can be performed efficiently.

[5] In the present invention, it is preferable that the water jacket is used for a multi-cylinder internal combustion engine including a cylinder head having a plurality of exhaust ports and an exhaust gas collecting portion merging the exhaust ports,

the water jacket has a collecting portion coolant flow path that covers the exhaust collecting portion,

the cross-sectional area of the collecting section cooling liquid flow path is formed small, and the surface area of the collecting section cooling liquid flow path is formed large so that the flow speed of the cooling liquid flowing through the collecting section cooling liquid flow path is higher than the flow speed of the cooling liquid flowing through the cooling liquid flow path.

According to the present invention, the main flow of the coolant can be made to flow to the exhaust collecting portion having a high temperature, and the exhaust heat can be reliably cooled. Further, the heat transfer efficiency is improved by the ridge portions, and the combustion chamber can be reliably cooled. That is, the combustion chamber and the exhaust gas collecting portion can be appropriately cooled at a predetermined flow rate of the coolant.

Drawings

Fig. 1 is a sectional view of a main portion of an internal combustion engine according to an embodiment of the present invention, taken in a direction perpendicular to a cylinder row direction.

Fig. 2 is a perspective view of the cylinder head as viewed from below.

Fig. 3 is a sectional view of the cylinder head taken along line III-III in fig. 1.

Fig. 4 is a perspective view of the cylinder head with the coolant passage drawn out and viewed obliquely from above.

Fig. 5 is a perspective view of the cylinder head with the coolant passage drawn out and viewed obliquely from below.

Fig. 6 is an explanatory diagram showing a first projection of the main coolant passage.

Fig. 7 is an explanatory view showing the second protrusions of the exhaust-side coolant flow field.

Description of the reference symbols

1: a cylinder;

2: a cylinder block;

3: a cylinder head;

3S: a side wall;

6: a combustion chamber;

7: an air inlet;

8: an exhaust gas collection port;

8 a: an exhaust port;

8 b: an exhaust gas collection unit;

8 c: an exhaust outlet;

11: a valve drive chamber;

18: an exhaust outlet tubular portion (a portion defining an exhaust outlet);

19: a bulging portion;

30: a cooling fluid passage in the cylinder head;

32: an upper exhaust side coolant passage;

33: a lower discharge side coolant passage;

101: a first protrusion portion;

101 a: a horizontal portion;

101 b: a retention section;

103: a second projection strip portion;

103 a: a horizontal portion;

103 b: a retention section;

e: an engine.

Detailed Description

Hereinafter, an embodiment in which the present invention is applied to an internal combustion engine for an automobile (hereinafter, simply referred to as an engine E) will be described in detail with reference to the drawings. Hereinafter, the description will be made in the vertical direction shown in fig. 1 with reference to a state where the engine E is mounted on the automobile.

As shown in fig. 1 and 2, the engine E is an in-line four-cylinder gasoline engine of the SOHC4 valve type. As shown in fig. 1, the engine E includes: a cylinder block 2 in which 4 cylinders 1 for housing pistons are formed in a row; a box-shaped cylinder head 3 fastened to an upper portion of the cylinder block 2; and a cylinder head cover 4 fastened to an upper portion of the cylinder head 3, and the engine E is mounted on the vehicle in a posture in which the cylinder head 3 is disposed on an upper side in the vertical direction. The cylinder block 2 and the cylinder head 3 are cast from an aluminum alloy.

The cylinders 1 extend in substantially the vertical direction, and are formed in parallel with each other on the cylinder block 2. Hereinafter, the arrangement direction of the plurality of cylinders 1 arranged in an array is referred to as a cylinder row direction. The upper end of each cylinder 1 opens to an upper end surface 2a of the cylinder block 2, and the lower end opens to a crank chamber (not shown) formed in a lower portion of the cylinder block 2. A block internal cooling liquid passage 5 (a block internal water jacket) is formed in a side portion of the cylinder 1 of the cylinder block 2 so as to integrally surround a side peripheral portion of each cylinder 1. The block internal cooling liquid passage 5 is curved so as to follow the side peripheral portion of each cylinder 1, and the upper end of the block internal cooling liquid passage 5 opens at the upper end surface 2a of the cylinder block 2. The block internal cooling liquid passage 5 is formed as a cavity by sand molding or the like at the time of molding the cylinder block 2 in order to circulate a cooling liquid such as cooling water, oil, or a refrigerant.

A combustion chamber recess 3b, which is a curved recess, is formed in a portion of a joint surface of the cylinder head 3 to the cylinder block 2 (hereinafter, referred to as a cylinder block joint surface 3a) that faces each cylinder 1. Each combustion chamber recess 3b defines a combustion chamber 6 together with a portion of each cylinder 1 above the piston. That is, the cylinder head 3 defines the upper edge of the combustion chamber 6.

Inside the cylinder head 3 are formed: 4 intake ports 7 whose upstream ends open to one side surface (left side surface in fig. 1) of the cylinder head 3 in the bank direction and whose downstream ends branch into two branches open to the wall surface of each combustion chamber recess 3 b; one exhaust collecting port 8 has two upstream ends that open to the wall surface of each combustion chamber recess 3b, and has a downstream end that opens to the other side surface (the right side surface in fig. 1) of the cylinder head 3 in the cylinder row direction.

That is, the exhaust collection port 8 includes a plurality of (8) exhaust ports 8a opening to the combustion chamber recesses 3b in the cylinder head 3 and an exhaust collection portion 8b collecting all the exhaust ports 8a, and the exhaust collection portion 8b has a single exhaust outlet 8c formed in the other side surface of the cylinder head 3. With reference to the combustion chamber recess 3b, the side provided with the intake port 7 is the intake side, and the side provided with the exhaust collection port 8 is the exhaust side.

An intake valve 9 for opening and closing each connection portion of the intake port 7 to the combustion chamber 6 and an exhaust valve 10 for opening and closing each connection portion of the exhaust collection port 8 to the combustion chamber 6 are slidably provided in the cylinder head 3. A valve operating chamber 11 is defined between the cylinder head 3 and the cylinder head cover 4, and a valve operating mechanism 12 for opening the intake valve 9 and the exhaust valve 10 is housed in the valve operating chamber 11. The valve gear 12 includes a camshaft 13 rotatably mounted on the cylinder head 3, a rocker shaft 14 disposed above the camshaft 13, and intake rocker arms 15 and exhaust rocker arms 16 swingably supported by the rocker shaft 14, and the like. On the camshaft 13, 4 valve operating cams 13a are formed, and the 4 valve operating cams 13a drive a pair of the intake valve 9 and the exhaust valve 10 for each cylinder 1.

As shown in fig. 2, the exhaust outlet 8c is formed at a longitudinally intermediate position of the exhaust-side surface 3c of the cylinder head 3. Further, a spark plug insertion hole 17 for inserting a spark plug (not shown) is formed in the center of the four intake ports 7 and the exhaust collecting port 8 in the wall surface of the combustion chamber recess 3b so as to penetrate the upper surface of the cylinder head 3.

As shown in fig. 1 and 2, the exhaust collecting portion 8b is formed on the exhaust side of the cylinder head 3 with respect to the cylinder block joint surface 3 a. More specifically, the exhaust outlet 8c is defined by a tubular exhaust outlet tubular portion 18 protruding from the exhaust-side surface 3c of the cylinder head 3, and the exhaust outlet tubular portion 18 of the cylinder head 3 and its vicinity bulge laterally with respect to the cylinder block 2 to form a bulge portion 19 forming the exhaust collecting portion 8 b.

The end surface of the exhaust outlet tubular portion 18 is a joint surface 18a of a downstream exhaust passage member 20 such as a turbine of a supercharger (turbocharger), an exhaust gas purification device, or the like, not shown. Further, at the tip end of the exhaust outlet tubular portion 18, a plurality of (4 in the example of the drawing) fastening bosses 21 for fastening the downstream exhaust passage member 20 by bolts are formed so as to surround the exhaust outlet 8 c. On the other hand, two ribs 22 are formed on the lower surface of the bulging portion 19 so as to reach the fastening bosses 21 from the peripheral edge of the cylinder block joint surface 3 a. These ribs 22 extend in the front-rear direction, which is a direction toward and away from the banks, and are in a splayed shape that opens from the fastening boss 21 toward the cylinder block joint surface 3 a.

As described above, the downstream-side exhaust passage member 20 such as a supercharger or an exhaust gas purification device is disposed in front of the cylinder block 2 and the cylinder head 3, and after the engine E is started, these members are heated to a high temperature. Therefore, the bulging portion 19 of the cylinder head 3 bulging laterally with respect to the cylinder block 2 is likely to transmit heat from the supercharger or the exhaust gas purification apparatus by heat transfer, radiation, and convection, and particularly the lower surface is likely to have a high temperature. Further, if the lower surface of the bulging portion 19 is at a high temperature, the sealing performance between the cylinder head 3 and the downstream exhaust passage member 20 is likely to be lowered due to deformation caused by thermal expansion, but in the present embodiment, the deformation of the bulging portion 19 can be suppressed by forming the rib 22 extending in the direction approaching and separating from the cylinder row on the lower surface of the bulging portion 19.

As shown in fig. 1 and 3 to 5, in the cylinder head 3, cylinder head internal cooling liquid passages 30(31 to 39, cylinder head internal water jacket) are formed around the combustion chamber recess 3b, the intake port 7, and the exhaust collection port 8 in order to suppress a temperature rise caused by heat transfer from the combustion gas in the combustion chamber 6 or the exhaust collection port 8. The cylinder head internal cooling liquid passage 30 is also formed as a cavity by sand molds or the like at the time of molding the cylinder head 3 in order to allow a cooling liquid such as cooling water, oil, or a refrigerant to flow therethrough, but the cylinder head internal cooling liquid passage 30 is shown as a solid space portion in fig. 4 and 5 by looking through the cylinder head 3.

The head-internal cooling liquid passage 30 includes, as main elements, a main cooling liquid passage 31, an upper exhaust-side cooling liquid passage 32, a lower exhaust-side cooling liquid passage 33, an exhaust-side connecting passage 34, an intake-side cooling liquid passage 35, an intake-side connecting passage 36, and the like. The main coolant passage 31 extends in the cylinder row direction (longitudinal direction) of the cylinder head 3 so as to pass through the vicinity of the upper side of the plurality of combustion chamber recesses 3 b. The upper exhaust-side coolant passage 32 and the lower exhaust-side coolant passage 33 are disposed so as to sandwich the exhaust collecting portion 8b from above and below, and each extend in the longitudinal direction of the cylinder head 3. The exhaust-side connecting passage 34 connects the main coolant passage 31 to the upper exhaust-side coolant passage 32 and the lower exhaust-side coolant passage 33. The intake-side coolant passage 35 is disposed below the intake port 7 and extends in the longitudinal direction of the cylinder head 3. The intake side connecting passage 36 connects the main coolant passage 31 and the intake side coolant passage 35.

The broken line in fig. 2 indicates a portion that comes into contact with the upper end of the block internal cooling liquid passage 5 when the cylinder block 2 and the cylinder head 3 are fastened. In the block internal cooling liquid passage 5, the cooling liquid flows as indicated by the hollow arrow. Two coolant inflow passages 37 are formed at one end in the cylinder row direction at a portion where the upper end of the block internal cooling liquid passage 5 contacts the cylinder block mating surface 3a, and the coolant inflow passages 37 extend upward from the block mating surface 3a in the cylinder head 3 and communicate with the cylinder head internal cooling liquid passage 30. The two coolant inflow passages 37 communicate with the exhaust-side connecting passage 34 and the intake-side connecting passage 36 disposed on one end side of the head-interior cooling liquid passage 30 in the bank direction, respectively, and allow the coolant to flow in from the block-interior cooling liquid passage 5.

Further, a bypass passage 38 extending upward from the cylinder block joining surface 3a in the cylinder head 3 and communicating with the cylinder head internal cooling liquid passage 30 is formed at an appropriate position in a portion on the other end side in the cylinder row direction than the coolant inflow passage 37 in the broken line portion where the upper end of the cylinder block internal cooling liquid passage 5 and the cylinder block joining surface 3a meet. The bypass passage 38 communicates with the exhaust side connecting passage 34, the lower exhaust side coolant passage 33, the intake side connecting passage 36, or the intake side coolant passage 35 of the cylinder head internal cooling passage 30. Each bypass passage 38 is formed to have a smaller flow path cross-sectional area than the coolant inflow passage 37.

As shown in fig. 4 and 5, a coolant outflow passage 39 for discharging the coolant from the head internal coolant passage 30 is formed at the other end (end different from the end where the coolant inflow passage 37 is provided) of the upper exhaust side coolant passage 32 in the cylinder row direction. The outer end of the coolant outflow passage 39 communicates with a radiator (not shown) via a pipe, a hose, or the like. In the main coolant passage 31, the upper exhaust side coolant passage 32, the lower exhaust side coolant passage 33, and the intake side coolant passage 35, the coolant flows in the cylinder row direction as indicated by black arrows in fig. 3.

As shown in fig. 6, a plurality of first ridges 101 are provided in the main coolant passage 31, the main coolant passage 31 facing the combustion chamber wall defining the combustion chamber 6, the intake port wall defining the intake port 7, and the exhaust port wall defining the exhaust port 8a, and through which the coolant flows, the plurality of first ridges 101 being located on the combustion chamber wall between the intake port wall and the exhaust port wall, and extending in the main coolant passage 31 in a direction perpendicular to the flow direction of the coolant flowing between the intake port wall and the exhaust port wall.

As shown in fig. 7, a plurality of second protrusions 103 are provided between the adjacent exhaust-side connecting passages 34 and/or between the adjacent intake-side connecting passages 36.

Horizontal portions 101a and 103a are provided at the distal ends of the first protruding portion 101 and the second protruding portion 103 in the protruding direction. Furthermore, retention portions 101b, 103b recessed toward the base end side in the protruding direction are provided between the adjacent first protrusions 101 and between the adjacent second protrusions 103.

In the present embodiment, the first protrusions 101 and the second protrusions 103 are set to have a projection height of 0.25mm, a width of 0.5mm to 2.0mm, and a distance of 2.5mm to 7.5 mm. The number of the protrusions of the present invention is not limited to this, and is preferably set as appropriate according to the type and specification of the engine E, the shape of the water jacket, and the like.

The cylinder head internal cooling liquid passage 30, which is the water jacket of the present embodiment, includes an upper exhaust side cooling liquid passage 32 and a lower exhaust side cooling liquid passage 33, which are collection portion cooling liquid passages covering the exhaust collection portion.

The upper and lower discharge-side coolant passages 32, 33 are formed to have a small cross-sectional area and a large surface area so that the coolant flowing through the upper and lower discharge-side coolant passages 32, 33 as the collective coolant passages has a higher (faster) flow rate than the coolant flowing through the main coolant passage 31 as the coolant passage.

According to the in-cylinder head cooling liquid passage 30 as the water jacket of the present embodiment, the first protrusions 101 and the second protrusions 103 can improve the heat transfer efficiency and the cooling performance. Further, the first protrusions 101 and the second protrusions 103 formed on the wall surface of the in-cylinder-head cooling liquid passage 30 improve the rigidity of the wall surface, and the wall defining the in-cylinder-head cooling liquid passage 30 is thinned, thereby improving the heat transfer efficiency.

Further, according to the present embodiment, the horizontal portions 101a and 103a at the distal ends in the protruding direction suppress an increase in pressure loss due to the formation of the first protrusions 101 and the second protrusions 103, and the coolant flowing through the cylinder head internal cooling liquid passage 30, which is a water jacket, can collide with the side surfaces of the first protrusions 101 and the second protrusions 103, thereby improving the heat transfer efficiency.

The coolant flowing through the cylinder head internal cooling liquid passage 30 flows into the retention portions 101b and 103b after passing over the first protrusions 101 and the second protrusions 103.

In the present embodiment, the first protrusions 101 are formed on a combustion chamber wall that defines the combustion chamber 6, and the combustion chamber wall is located between an intake port wall that defines the intake port 7 and an exhaust port wall that defines the exhaust port 8 a. The first protrusions 101 can increase the rigidity of the combustion chamber wall around the combustion chamber 6, and can reduce the thickness of the combustion chamber wall to improve the heat transfer efficiency.

In the present embodiment, the cylinder head 3 is assembled to the cylinder block 2, and the cylinder head 3 has a boundary portion between the joint surface with the cylinder block 2 and the bottom surface of the intake port wall, and a boundary portion between the joint surface with the cylinder block 2 and the bottom surface of the exhaust port wall.

As shown in fig. 7, the second protrusions 103 are formed at the boundary between the joint surface with the cylinder block 2 and the bottom surface of the intake port wall and at the boundary between the joint surface with the cylinder block 2 and the bottom surface of the exhaust port wall. Thus, according to the present embodiment, the exhaust gas immediately below the exhaust port 8 facing the combustion chamber 6 can be cooled, and the exhaust gas can be efficiently cooled. In addition, the cooling of the valve seat periphery facing the combustion chamber 8 can be performed efficiently. In the present invention, the second ridge may be formed at least at the boundary between the joint surface with the cylinder block 2 and the bottom surface of the exhaust port wall, and it is not necessary to provide the second ridge at the boundary between the joint surface with the cylinder block 2 and the bottom surface of the intake port wall.

The cylinder-head internal cooling liquid passage 30, which is the water jacket of the present embodiment, is used in an engine E, which is a multi-cylinder internal combustion engine, and includes a cylinder head 3, and the cylinder head 3 includes a plurality of exhaust ports 8a and an exhaust gas merging portion 8b that merges the exhaust ports 8 a.

The cylinder head internal cooling liquid passage 30 has an upper exhaust side cooling liquid passage 32 and a lower exhaust side cooling liquid passage 33 as collective portion cooling liquid passages covering the exhaust gas collective portion 8 b.

The upper and lower discharge-side coolant passages 32, 33 are formed to have a small cross-sectional area and a large surface area so that the coolant flowing through the upper and lower discharge-side coolant passages 32, 33 as the collective coolant passages has a higher (faster) flow rate than the coolant flowing through the main coolant passage 31 as the coolant passage.

According to the present embodiment, the main flow of the coolant can be made to flow to the exhaust collecting portion 8b having a high temperature, and the exhaust heat can be reliably cooled. Further, the first protrusions 101 and the second protrusions 103 improve the heat transfer efficiency, and thereby the combustion chamber 6 can be reliably cooled even at a small flow rate. That is, the combustion chamber 6 and the exhaust gas collection portion 8b can be appropriately cooled at a predetermined flow rate of the coolant.

The above description has been made of the specific embodiments, but the present invention is not limited to the above embodiments and can be widely modified. For example, in the above-described embodiment, the present invention is applied to a four-valve in-line four-cylinder gasoline engine for an automobile, but may be applied to a different type of internal combustion engine for other uses. In the above embodiment, only one exhaust outlet 8c is formed, but two exhaust outlets 8c may be formed for every two cylinders adjacent to each other, and a plurality of exhaust collecting portions 8b may be formed in the cylinder head 3. The specific configuration, arrangement, number, angle, and the like of each member or portion can be appropriately changed without departing from the scope of the present invention. On the other hand, all the components of the cylinder head 3 of the present invention shown in the above embodiments are not necessarily essential, and may be appropriately selected.