DE112015003558T5 - Cylinder head of an internal combustion engine - Google Patents

Abstract

A straight exhaust duct (13) having a shorter pipe length than a curved exhaust duct and an inner diameter gradually increasing from a combustion chamber (7B) to an exhaust gas collecting portion (14) is characterized in that, when a bottom surface of the exhaust gas collecting portion (14) is defined as a reference surface (18) and a virtual extension surface (19) is arranged such that the reference surface (18) extends toward an upstream end of the straight outlet channel (13), a protruding portion (20) extending from the virtual extension surface (19) projects upwards, is formed on a bottom surface of the straight outlet channel (13).

Description

TECHNICAL AREA

The present invention relates to cylinder heads of internal combustion engines, and more particularly to a cylinder head of an internal combustion engine in which a plurality of combustion chamber communicating exhaust passages are integrally formed with an exhaust gas collecting portion in which the plurality of exhaust passages are merged.

GENERAL PRIOR ART

Internal combustion engines used in vehicles, e.g. Motor vehicles, mounted, include cylinder heads. There are known types of cylinder heads in which a plurality of combustor-related exhaust passages are integrally connected to an exhaust gas collecting section in which the plurality of exhaust passages are merged (see, for example, Patent Literature 1).

Such a conventional cylinder head has a configuration in which the exhaust ports are juxtaposed in a cylinder-row direction, and each of the exhaust ports is formed such that its inner diameter gradually increases from each combustion chamber toward the exhaust gas collecting section.

An exhaust passage formed in the middle in the cylinder-row direction faces the exhaust collecting portion in the direction perpendicular to the cylinder-row direction, and a pipe length of the exhaust passage formed in the middle in the cylinder-row direction is shorter than the pipe lengths of exhaust ports formed on both sides in the cylinder-row direction.

Each exhaust passage has a curved bottom surface curved upward from each combustion chamber and an inclined bottom surface inclined upward from the curved bottom surface. The exhaust gas discharged from the combustion chamber flows upward and is collected in the exhaust gas collecting section.

READINGS

Patent Literature

• Patent Literature 1: JP 2000-161132 A

BRIEF SUMMARY OF THE INVENTION

TECHNICAL PROBLEM

Characterized in that in the conventional cylinder head of the internal combustion engine, located in the cylinder row direction on both sides exhaust ducts longer line lengths than the located in the middle in the cylinder row direction exhaust passage, a large increase of passage areas of the exhaust ports is prevented on both sides. Thus, a flow of the exhaust gas discharged from the combustion chambers can be easily calmed by these exhaust ports on the way to the exhaust collecting portion.

By contrast, because the outlet channel formed in the middle in the cylinder row direction has a shorter line length than the outlet channels formed on both sides in the cylinder row direction, the passage area of this outlet channel immediately increases.

This makes it difficult to calm the exhaust gas discharged and passing through this exhaust passage on the way to the exhaust collecting portion, which may cause turbulent flow or congestion of the exhaust gas at the bottom surface of the exhaust passage. This may reduce the exhaust emission power due to an increase in the back pressure of the exhaust gas discharged from the combustion chamber into this exhaust passage.

The present invention has been made in view of the above-described problem, and it is an object of the present invention to provide a cylinder head of an internal combustion engine capable of increasing the back pressure of exhaust gas discharged from combustion chambers into linear exhaust passages and reducing the power of the cylinder Prevent exhaust emissions.

TECHNICAL SOLUTION

One aspect of the present invention is a cylinder head provided on an upper surface of a cylinder block in an internal combustion engine having cylinders, the cylinder head having a plurality of combustion chambers sequenced in a cylinder-row direction, and a plurality of exhaust ports in a view from above communicating with the combustion chambers, the exhaust ports comprising: a curved exhaust passage integrally formed with the cylinder head and extending in the direction perpendicular to the cylinder-row direction and then curved in the cylinder-row direction; a straight exhaust passage integrally formed with the cylinder head, having a shorter pipe length than the curved exhaust passage and extending in a direction perpendicular to the cylinder row direction; and an exhaust collecting portion, in which downstream portions of the curved exhaust passage and the straight exhaust passage are integrated, the exhaust collecting portion being integrally formed with the cylinder head, the straight exhaust passage including a curved bottom surface extending from one of the combustion chambers and from the one combustion chamber is curved upward, and an inclined bottom surface which is inclined upward from the curved bottom surface, and wherein the straight outlet channel has an inner diameter which gradually increases from the one combustion chamber to the exhaust gas collecting section, wherein, when a bottom surface of the exhaust gas collecting section Reference surface is defined and a virtual extension surface is provided such that the reference surface extends toward an upstream end of the straight outlet channel, the straight outlet channel is provided at its bottom surface with a protruding portion that protrudes upwards from the virtual extent.

BENEFICIAL EFFECTS

According to the aspect of the invention, when the bottom surface of the exhaust collection portion is defined as a reference surface and the virtual extent surface is provided so that the reference surface extends toward an upstream end of the straight exhaust port, the straight exhaust port is a shorter pipe length than the curved exhaust port and an inner diameter gradually increasing from the one combustion chamber to the exhaust gas collecting portion, provided with the protruding portion protruding upward from the virtual extension surface at the bottom of the straight exhaust passage.

This configuration can prevent a large increase in the passage area of the straight exhaust passage from its upstream end to the exhaust collecting portion. Even if the exhaust gas flowing out of the one combustion chamber comes into contact with the curved bottom surface of the straight exhaust passage and causes flow separation, the protruding portion may prevent turbulent flow or congestion of the exhaust gas immediately after the flow separation.

Since generation of turbulent flow or congestion of the exhaust gas at the inclined bottom surface of the linear exhaust passage can be prevented, the flow of the exhaust gas can be calmed and introduced into the exhaust gas collecting section. Accordingly, an increase of a back pressure of the exhaust gas in the linear exhaust passage can be prevented, so that a reduction in the performance of the exhaust emission can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

1 FIG. 10 is a front view of an internal combustion engine including a cylinder head according to an embodiment of the present invention. FIG.

2 FIG. 12 is a plan view of the internal combustion engine including the cylinder head according to the embodiment of the present invention. FIG.

3 is a cross-sectional view taken along the line III-III of 2 seen in a direction indicated by arrows.

4 is a cross-sectional view taken along the line IV-IV of 1 seen in a direction indicated by arrows.

5 FIG. 16 is a front view of the cylinder head according to the embodiment of the present invention. FIG.

6 is a cross-sectional view taken along the line VI-VI of 4 seen in a direction indicated by arrows.

7 FIG. 11 is a view illustrating an exhaust gas flow in exhaust passages without protruding portions. FIG.

8th FIG. 13 is a view illustrating an exhaust flow in exhaust passages provided with protruding portions in the cylinder head according to the embodiment of the present invention. FIG.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of a cylinder head of an internal combustion engine according to the invention will be described with reference to the drawings.

As in 1 includes an engine mounted on a vehicle, such as a motor vehicle, as an internal combustion engine 1 a cylinder block 2 , one at the top of the cylinder block 2 provided cylinder head 3 , one at the top of the cylinder head 3 provided cylinder head cover 4 and one under the cylinder block 2 attached sump 5 to absorb oil.

As indicated by the dashed lines in 2 illustrated, includes the cylinder block 2 a plurality of cylinders 6A to 6C in the vehicle width direction (right-left direction). In the cylinders 6A to 6C are vertically movable piston (not shown in the drawing) housed.

As in 4 shown are on the bottom of the cylinder head 3 in a row direction of the cylinders 6A to 6C by the dashed circles illustrated combustion chambers 7A to 7C formed, each with the cylinders 6A to 6C keep in touch. In 3 is the combustion chamber 7B in a lower section of the cylinder head 3 formed and the combustion chambers 7A and 7C which are the same shape as the combustion chamber 7B are also in the lower part of the cylinder head 3 educated.

As in 2 shown is an intake manifold 8th with the back of the cylinder head 3 connected so that intake air into the intake manifold 8th is introduced via an intake pipe, not shown in the drawing. As in 4 shown is the cylinder head 3 with a plurality of intake ports 9 Mistake. The through the intake manifold 8th flowing intake air is in the intake ducts 9 introduced.

The respective intake ducts 9 stand above the combustion chambers 7A to 7C with the cylinders 6A to 6C in connection and in the intake ducts 9 introduced intake air is in the cylinder 6A to 6C through the combustion chambers 7A to 7C further introduced.

As in 4 shown is the cylinder head 3 with a plurality of outlet channels 10 Mistake. The respective outlet channels 10 stand above the combustion chambers 7A to 7C with the cylinders 6A to 6C in connection.

As in 4 shown include the outlet channels 10 , seen from the top of the outlet channels 10 , curved outlet channels 11 . 12 extending in the vertical direction (forward) to the row direction of the cylinder 6A to 6C extend and then in the row direction of the cylinder 6A to 6C are curved, straight outlet channels 13 that have a shorter line length than the respective curved outlet channels 11 . 12 have and in the direction perpendicular to the row direction of the cylinder 6A to 6C extend (in right-left direction), and an exhaust gas collecting section 14 in which the downstream portions of the curved outlet channels 11 . 12 and the straight exhaust ducts 13 are integrated. In the present case, the row direction corresponds to the cylinder 6A to 6C a cylinder row direction according to the present invention.

The curved outlet channels 11 . 12 , the straight exhaust ducts 13 and the exhaust collecting section 14 are in the cylinder head 3 educated. As in 5 shown is the cylinder head 3 at its front with an opening 14a Mistake. The opening 14a is located at downstream ends of the curved outlet channels 11 ,

As in 5 shown, the straight exhaust ducts extend 13 , seen in the direction perpendicular to the right-left direction (from the front) of the cylinder head 3 , from the combustion chamber 7B to the exhaust collection section 14 taking the opening 14a overlap. Consequently, the respective straight exhaust ducts 13 a shorter overall length than the respective curved outlet channels 11 . 12 on.

As in 1 and 2 shown is a turbocharger 15 on the front surface of the cylinder head 3 attached. The turbocharger 15 is with the in 4 shown opening 14a connected. As in 1 and 2 shown is a catalyst 17 over an exhaust pipe 16 with the turbocharger 15 connected.

As in 4 shown in the engine 1 according to the present embodiment of the combustion chambers 7A to 7C discharged exhaust gas through the curved outlet channels 11 . 12 and the straight outlet channels 13 into the exhaust collection section 14 delivered and collected there.

Part of the exhaust collection section 14 collected exhaust gas is in a turbine (not shown in the drawing) in the turbocharger 15 introduced to turn the turbine. The rest of the exhaust gas is through the exhaust pipe 16 in the catalyst 17 introduced by the catalyst 17 cleaned and then via a with the downstream end of the catalyst 17 Released exhaust pipe (not shown in the drawing) into the atmosphere.

As in the 4 and 6 shown include the straight outlet channels 13 each a curved bottom surface 13a extending from the combustion chamber 7B extends from and from the combustion chamber 7B is curved upwards, and a sloping bottom surface 13b coming from the curved bottom surface 13a is tilted upwards. The straight outlet channels 13 have an inner diameter that of the combustion chamber 7B to the exhaust collection section 14 gradually increases.

As in 4 shown include the curved outlet channels 11 . 12 curved floor surfaces 11a . 12a extending from the combustion chambers 7A . 7C extend out and from the combustion chambers 7A . 7C are curved upwards, and inclined floor surfaces 11b . 12b coming from the curved bottom surfaces 11a . 12a are tilted upwards. The curved outlet channels 11 . 12 have inner diameter, that of the combustion chambers 7A . 7C to the exhaust collection section 14 gradually increase.

As in 6 is shown, the bottom surface of the exhaust gas collecting section 14 to the straight outlet channels 13 towards as a reference surface 18 designated. An area along which the reference surface 18 to the upstream end of the respective straight exhaust ducts 13 extends as a virtual extent surface 19 designated. In the present embodiment, protruding portions are 20 by the virtual extent 19 project upwards, at the bottom surfaces of the straight outlet channels 13 educated.

The protruding sections 20 are each in a range between an upper section 20a that is in the curved floor area 13a and above the virtual extent surface 19 located, and a bottom surface of the exhaust gas collecting section 14 educated. That is, the curved bottom surface 13a According to the present embodiment, the projecting portion includes 20 , In 6 is the area in which the protruding section 20 is formed by the reference numeral 20A designated. In addition, the upstream-downstream direction is a direction in which the exhaust gas flows.

As in 4 is shown, which serves at one end (at the right end) in the row direction of the cylinder 6A to 6C in the cylinder head 3 provided combustion chamber 7A as an end-side combustion chamber according to the present invention and that at the other end (left-hand end) in the row direction of the cylinders 6A to 6C provided combustion chamber 7C as another end-side combustion chamber according to the present invention. The between the combustion chamber 7A and the combustion chamber 7C provided combustion chamber 7B serves as the central combustion chamber according to the present invention.

As described above, the cylinder head comprises 3 According to the present embodiment, the protruding portions 20 in the from the combustion chamber 7B as middle combustion chamber ersteckenden straight exhaust ducts 13 ,

As in 3 and in 6 Shown are the curved outlet channels 11 . 12 and the straight outlet channels 13 at their respective lower and upper sides with Wassermänteln 21A to 21C and 22A to 22C Mistake. That through the curved outlet channels 11 . 12 and the straight outlet channels 13 flowing exhaust gas G is through that in the water jackets 21A to 21C and 22A to 22C flowing coolant W cooled.

As in 3 shown is the cylinder head 3 with coolant inlets 24 on a connection surface 23 between the cylinder head 3 and the cylinder block 2 Mistake.

The water coats 21A to 21C of the cylinder head 3 stand above the coolant inlets 24 with water-jackets 25A to 25C of the cylinder block 2 in connection. That from the water-coats 25A to 25C discharged coolant flows over the coolant inlets 24 in the water-coats 21A to 21C ,

As in 3 shown in the water coats 21A to 21C flowing coolant from there into the water jackets 22A to 22C introduced.

As in 6 shown overlap the coolant inlets 24 with the protruding sections 20 in the height direction of the vehicle 1 , The coolant inlets 24 are among the protruding sections 20 open. That through the coolant inlets 24 in the water jacket 21B flowing coolant hits directly on the lower side of the protruding portions 20 ,

As in 3 is shown, the position T1 of the bottom surface of the straight outlet channels 13 in the height direction of the engine 1 higher than the position T2 of the bottom surfaces of the curved outlet channels 11 . 12 in the height direction of the engine 1 ,

Next, the operation will be described.

In the cylinder head 3 According to the present embodiment, the outlet channels 10 , seen from the top of the outlet channels 10 , the curved outlet channels 11 . 12 extending in the direction perpendicular to the row direction of the cylinder 6A to 6C extend and then in the row direction of the cylinder 6A to 6C are curved, the straight outlet channels 13 that have a shorter line length than the respective curved outlet channels 11 . 12 have and in the direction perpendicular to the row direction of the cylinder 6A to 6C extend, and the exhaust gas collection section 14 in which the downstream portions of the curved outlet channels 11 . 12 and the straight exhaust ducts 13 are integrated.

In the present case take the passage areas of the curved outlet channels 11 . 12 with the longer line lengths not immediately too. This facilitates a calming of the flow from the combustion chambers 7A . 7C through the curved outlet channels 11 . 12 spent exhaust gas on the way to the exhaust gas collection channel 14 ,

On the other hand, the passage surfaces of the straight outlet channels 13 With the shorter line lengths increase immediately, this is a reassurance of the out of the combustion chamber 7B in the straight outlet channels 13 discharged exhaust gas on the way to the exhaust gas collecting section 14 difficult.

In 7 are straight outlet channels 31 that does not match the protruding sections 20 are provided, exemplified. The straight outlet channels 31 can generate a turbulent flow or congestion of exhaust gases G1 flowing therein at bottom surfaces of the straight exhaust passages 31 cause, as indicated by the arrows A. The turbulent flow or congestion can reduce the exhaust emission power because of the back pressure of the combustion chamber into the exhaust ducts 31 discharged exhaust gas increases.

According to the present embodiment, the straight outlet channels 31 a shorter line length than the curved outlet channels 11 . 12 on. The inner diameter of the respective straight outlet channels 13 takes from the combustion chamber 7B to the exhaust collection section 14 gradually closed. In the present embodiment, when the bottom surface of the exhaust collecting portion 14 as a reference surface 18 is defined and the virtual extent surface 19 is provided so that the reference surface 18 toward the upstream ends of the respective straight exhaust passages 13 extends are those of the virtual extent surface 19 protruding sections 20 at the bottom surfaces of the straight outlet channels 13 educated.

This configuration according to the present embodiment can greatly increase the passage areas of the straight exhaust passages 13 from their upstream ends to the exhaust collecting section 14 prevent it. Even if that's from one combustion chamber 7B outflowing exhaust gas in contact with the curved bottom surfaces 13a comes and causes a flow separation, the protruding sections can 20 prevent turbulent flow or congestion of the exhaust gas immediately after flow separation.

Since generation of turbulent flow or congestion of the exhaust gas at the inclined bottom surfaces 13b namely at the protruding sections 20 the linear outlet channels 13 , can be prevented, the flow of the exhaust gas can be calmed and in the exhaust gas collecting section 14 be introduced. Accordingly, an increase in back pressure of the exhaust gas in the linear exhaust passages 13 be prevented, so that a reduction in the performance of the exhaust emission can be prevented.

8th shows a state in which a turbulent flow or a congestion of the exhaust gas G2 at the projecting portions 20 the straight outlet channels 13 is prevented, so that the exhaust gas G2 flows evenly.

In the cylinder head 3 The present invention is the water jackets 21A to 21C into which the coolant from the cylinder block 2 flows in, at the bottom of the curved outlet channels 11 . 12 and the straight exhaust ducts 13 intended.

Because a capacity of the entire water jackets 21A to 21C by the thickness of the projection of the respective projecting portions 20 can be increased, a larger amount of coolant in the water jackets 21A to 21C flow into it. This improves a cooling effect on the straight outlet channels 13 ,

As a result, excessive increase in the temperature of the exhaust gas in the exhaust gas collecting section 14 be prevented. Because the cylinder head 3 can be sufficiently cooled, also a wear of the cylinder head 3 restricted, so that the life of the cylinder head 3 can be extended.

Further, the coolant inlets 24 through which the coolant from the cylinder block 2 flows, at the connection surface 23 between the cylinder head 3 and the cylinder block 2 formed and under the protruding sections 20 open to with them in the height direction of the engine 1 to overlap.

That with a low temperature from the cylinder block 2 through the coolant inlets 24 in the cylinder head 3 Incoming coolant thus hits directly on the lower side of the protruding portions 20 , Accordingly, the cooling effect on the straight outlet channels 13 be improved more efficiently.

Furthermore, the cylinder head 3 according to the present embodiment with the projecting portions 20 each provided in the area between an upper section 20a that is in the curved floor area 13a and above the virtual extent surface 19 located, and the bottom surface of the exhaust gas collecting section 14 are formed. This can cause a large increase in the passage areas of the straight exhaust ducts 13 from the curved floor surfaces 13a to the exhaust collection section 14 be prevented.

Accordingly, the projecting portions 20 in the linear outlet channels 13 prevent the generation of turbulent flow or congestion of the exhaust gas to calm the flow of the exhaust gas and the exhaust gas into the exhaust gas collecting section 14 introduce. Because the capacity of the water jacket 21B can also be effectively increased, can also a large amount of coolant through the water jacket 21B stream. As a result, the cooling effect on the straight outlet channels 13 be improved more effectively.

Furthermore, in the cylinder head 3 In the present embodiment, the projecting portions 20 in the straight outlet channels 13 formed, extending from the combustion chamber 7B extend between the one end (the right end) in the row direction of the cylinder 6A to 6C formed combustion chamber 7A and at the other end (the left end) in the row direction of the cylinders 6A to 6C formed combustion chamber 7C is arranged.

The position T1 of the bottom surface of the straight exhaust ducts 13 in the height direction of the engine 1 is thus the thickness of the projection of the protruding portions 20 higher than the position T2 of the curved outlet channels 11 . 12 in the height direction of the engine 1 ,

Thus, the passage areas of the straight outlet channels 13 smaller than the passage areas of the curved outlet channels 11 . 12 be. Accordingly, turbulent flow or congestion of the exhaust gas may be caused by the protruding portion 20 be prevented, so that the flow of the exhaust gas can be calmed and in the exhaust gas collecting section 14 can be introduced.

Furthermore, the curved outlet channels 11 . 12 whose passage areas do not increase immediately, calm the flow of exhaust gas without reducing their passage areas. Accordingly, an increase in the back pressure in the curved outlet channels 11 . 12 reliably prevented.

Furthermore, in the cylinder head 3 According to the present embodiment, the coolant, the straight outlet channels 13 Cool down in which the temperature is higher than in the curved outlet channels 11 . 12 increases, since the straight exhaust ducts 13 between the curved outlet channels 11 . 12 are arranged. Because the capacity of the water jacket 21B by the thickness of the projection of the respective in the straight outlet channels 13 formed projecting sections 20 can also be increased, a larger amount of coolant in the water jacket 21B flow in, so that the cooling effect on the straight outlet channels 13 can be improved.

Seen in the cross section of the cylinder head 3 along a plane vertical to the row direction of the cylinders 6A to 6C and parallel to the row direction of the cylinders 6A to 6C , position T1 is the bottom surface of the straight exhaust ducts 13 in the height direction of the engine 1 higher than the position T2 of the bottom surface of the respective curved outlet channels 11 . 12 in the height direction of the engine 1 ,

Thus, as in 3 shown a distance t1 of the water jacket 21B in the height direction greater than a distance t2 of the respective water jackets 21A . 21C be in the height direction. Accordingly, the capacity of the water jacket 21B be increased more than the capacity of the respective water jackets 21A . 21C , It should be noted that, although the protruding sections 20 in the cylinder head 2 according to the present embodiment, respectively along the inclined bottom surface 13b are formed in the longitudinal direction, the protruding portions 20 each in a predetermined range in the longitudinal direction of the curved bottom surface 13a to the inclined floor surface 13b can be trained.

Although an embodiment of the present invention has been described, it will be understood by those skilled in the art that various modifications can be made without departing from the scope of the invention. It is intended that all such modifications and equivalents fall within the scope of the following claims.

LIST OF REFERENCE NUMBERS

1

 ENGINE (INTERNAL COMBUSTION ENGINE)

2

 CYLINDER BLOCK

3

 CYLINDER HEAD

6A to 6C

 CYLINDER

7A

 COMBUSTION CHAMBER (A FINAL COMBUSTION CHAMBER)

7B

 COMBUSTION CHAMBER (MEDIUM COMBUSTION CHAMBER)

7C

 COMBUSTION CHAMBER (OTHER FINAL FIRE CHAMBER)

10

 exhaust port

11, 12

 CURVED EXHAUST CHANNEL

13

 STRAIGHT EXHAUST DUCT

13a

 CURVED FLOOR AREA

13b

 SLICED FLOOR AREA

14

 EXHAUST COLLECTOR SECTION

18

 REFERENCE AREA

19

 VIRTUAL REMOVAL SURFACE

20

 SUPREME SECTION

23

 PORT AREA

21B

 WATER COAT

24

 COOLANT INLET

Claims (5)

A cylinder head provided on an upper surface of a cylinder block in an internal combustion engine having cylinders, wherein the cylinder head communicates a plurality of combustion chambers juxtaposed in a cylinder-row direction and a plurality of exhaust passages communicating with the combustion chambers in a top view stand, wherein the outlet channels comprise: a curved outlet channel, which is formed integrally with the cylinder head and extending in the direction perpendicular to the cylinder row direction and then curved in the cylinder row direction; a straight exhaust passage integrally formed with the cylinder head, having a shorter pipe length than the curved exhaust passage and extending in a direction perpendicular to the cylinder row direction; and an exhaust collecting portion in which downstream portions of the curved exhaust passage and the straight exhaust passage are integrated, the exhaust collecting portion being integrally formed with the cylinder head, the straight exhaust passage including a curved bottom surface extending from one of the combustion chambers and from the one combustion chamber is curved upward, and an inclined bottom surface which is inclined upward from the curved bottom surface, and wherein the straight outlet channel has an inner diameter which gradually increases from the one combustion chamber to the exhaust gas collecting section, wherein, when a bottom surface of the exhaust gas collecting section Reference surface is defined and a virtual extension surface is provided such that the reference surface extends toward an upstream end of the straight outlet channel, the straight outlet channel is provided at its bottom surface with a protruding portion that protrudes upwards from the virtual extent. A cylinder head of the internal combustion engine according to claim 1, wherein: a water jacket into which coolant flows out of the cylinder block is formed on a lower side of each of the curved exhaust passage and the straight exhaust passage; a coolant inlet through which the coolant flows out of the cylinder block is formed on a land between the cylinder head and the cylinder block; and the coolant inlet is open under the protruding portion so as to overlap with each other in a height direction of the internal combustion engine. The cylinder head of the internal combustion engine according to claim 1 or 2, wherein the protruding portion is formed in a region between a portion located in the curved bottom surface and above the virtual extension portion and the bottom surface of the exhaust gas collecting portion. A cylinder head of the internal combustion engine according to any one of claims 1 to 3, wherein: the combustion chambers have an end combustion chamber formed at one end in the cylinder-row direction, another end-side combustion chamber formed at the other end in the cylinder-row direction, and a middle combustion chamber disposed between the one end-side combustion chamber and the other end-side combustion chamber; include; the curved exhaust passage includes an exhaust passage extending from the one end combustion chamber and an exhaust passage extending from the other end combustion chamber; the straight exhaust passage is an exhaust passage extending from the middle combustion chamber; and the protruding portion is formed in the straight exhaust passage extending from the central combustion chamber. A cylinder head of the internal combustion engine according to claim 4, wherein, seen in the cross section of the cylinder head along a plane vertical to the row direction of the cylinder and parallel to the row direction of the cylinder, a position of the bottom surface of the straight exhaust duct in the height direction of the internal combustion engine higher than a position of the bottom surface of the curved exhaust duct in the height direction of the internal combustion engine.

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