JP6777028B2 - Internal combustion engine cylinder head - Google Patents

Description

The present invention relates to a cylinder head of an internal combustion engine.

The cylinder head of an internal combustion engine is provided with a combustion chamber, a water jacket through which cooling water flows, a plug attachment portion having a plug hole for attaching a spark plug, an exhaust port, and the like. In order to cool such a combustion chamber and an exhaust port, for example, the cylinder head described in Patent Document 1 is provided independently of the first water jacket for cooling the combustion chamber and the first water jacket for exhaust. It has a second water jacket that cools the port.

Japanese Unexamined Patent Publication No. 2010-209479

By the way, in the cylinder head, the part existing in each combustion chamber where the amount of heat transferred from the spark plug to the cylinder head and the amount of heat transferred from the exhaust port to the cylinder head are added is more heat than other parts. By concentrating, the temperature tends to rise, making it a priority cooling site with high cooling requirements. Therefore, it is desired to improve the cooling performance of such a priority cooling portion.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a cylinder head of an internal combustion engine capable of enhancing cooling performance with respect to a priority cooling portion of the cylinder head.

Cylinder heads of an internal combustion engine that solves the above problems are provided in a direction intersecting with a plurality of linearly arranged combustion chambers and the arrangement direction of the combustion chambers, and an intake port and an exhaust connected to the combustion chambers. A water jacket formed between the port, the intake port and the exhaust port, straddling the plurality of combustion chambers and extending in the arrangement direction of the combustion chambers to cool the combustion chambers, and the intake port. It has a plug hole formed between the exhaust port and the ignition plug, and a plug attachment portion provided independently for each combustion chamber. The water jacket is located on the intake port side of the plug mounting portion and is located on the intake port side flow path provided for each combustion chamber and on the exhaust port side of the plug mounting portion. It has an exhaust port side flow path provided for each combustion chamber. Then, a portion where the temperature of the cylinder head rises due to the addition of the amount of heat transmitted from the spark plug attached to the plug hole and the amount of heat transmitted from the exhaust port, and the portion existing in each combustion chamber is designated as the priority cooling portion. Occasionally, the exhaust port side flow path is formed so as to pass through the priority cooling portion and the flow path cross-sectional area gradually decreases from the upstream of the exhaust port side flow path toward the priority cooling portion. .. The plug mounting portion has an upstream projection that projects so as to narrow toward the upstream side of the water jacket.

In the same configuration, the exhaust port side flow path passes through the priority cooling portion, and the cross-sectional area of the flow path gradually decreases from the upstream of the exhaust port side flow path toward the priority cooling portion. .. Therefore, the flow velocity of the cooling water flowing through the exhaust port side flow path increases from the upstream side of the exhaust port side flow path toward the priority cooling portion. As the flow velocity of the cooling water increases, the amount of heat carried away by the cooling water per unit time increases, so that the cooling performance for the priority cooling portion can be improved.

Further, when the cooling water flows into the water jacket, the flowing cooling water is divided into the cooling water flowing through the intake port side flow path and the cooling water flowing through the exhaust port side flow path by the upstream projection of the plug mounting portion. Here, the upstream protrusion protrudes so as to narrow toward the upstream side of the water jacket, and has a substantially triangular shape. The tip of the upstream protrusion, which has a substantially triangular shape, faces the upstream side of the water jacket. Therefore, when the cooling water flowing from the upstream of the plug mounting portion is diverted by the upstream protrusion, it is diverted from the relatively sharp tip portion as the base point, so that the change in the flow direction of the cooling water is small. Also, stagnation is unlikely to occur. Therefore, the decrease in the flow velocity of the cooling water at the time of diversion can be suppressed, and the decrease in the flow velocity of the cooling water flowing into the flow path on the exhaust port side can be suppressed, so that the cooling performance for the priority cooling portion can be improved.

Further, in the cylinder head, when it is the minimum value of the flow path cross-sectional area of the portion of the exhaust port side flow path that passes through the priority cooling portion and the value for each combustion chamber is set as the minimum cross-sectional area for each cylinder. The exhaust port side flow path may be formed so that the minimum cross-sectional area for each cylinder becomes larger toward the priority cooling portion located downstream of the water jacket.

As described above, the exhaust port side flow path is formed so that the cross-sectional area of the flow path gradually decreases from the upstream side of the exhaust port side flow path toward the priority cooling portion, so that the portion passes through the priority cooling portion. The pressure loss is relatively large in. Therefore, when the cooling water that has passed through one exhaust port side flow path flows into the next exhaust port side flow path located downstream, some of the cooling water is not on the exhaust port side flow path but on the intake port side. It is easy to flow into the flow path, and the flow rate of cooling water may decrease toward the exhaust port side flow path located downstream. In this respect, in the same configuration, each exhaust port side flow path is formed so that the minimum cross-sectional area for each cylinder becomes larger toward the priority cooling portion located downstream of the water jacket. Therefore, since the pressure loss becomes smaller in the exhaust port side flow path located downstream of the water jacket, the cooling water that has passed through one exhaust port side flow path flows into the next exhaust port side flow path located downstream. In this case, it becomes easier to flow into the exhaust port side flow path instead of the intake port side flow path. Therefore, it is possible to suppress a decrease in the flow rate of the cooling water in each exhaust port side flow path.

Further, in the cylinder head, the plug mounting portion may have a downstream projection protruding so as to narrow toward the downstream side of the water jacket.
According to the same configuration, the downstream protrusion of the plug mounting portion protrudes so as to narrow toward the downstream side of the water jacket, and has a substantially triangular shape. The tip of the downstream protrusion, which has a substantially triangular shape, faces the downstream side of the water jacket. Therefore, when the cooling water that has passed through the exhaust port side flow path and the cooling water that has passed through the intake port side flow path merge downstream of the downstream protrusion, the cooling water is less likely to stagnate. Therefore, for example, it is possible to suppress a decrease in the flow velocity of the cooling water that has merged at a position downstream of the downstream protrusion.

Further, in the cylinder head, the tip of the upstream protrusion is located closer to the wall surface of the water jacket on the intake port side than the wall surface of the water jacket on the exhaust port side in a cross section orthogonal to the central axis of the plug hole. It may be provided.

According to the same configuration, the tip of the upstream protrusion in the above cross section is provided at a position closer to the wall surface of the water jacket on the intake port side than the wall surface of the water jacket on the exhaust port side, and the tip of the upstream protrusion is provided. It is offset to the intake port side. Therefore, when the cooling water flowing from the upstream of the plug mounting portion is divided by the upstream projection, more cooling water flows into the exhaust port side flow path than the cooling water flowing into the intake port side flow path. Become. Therefore, as compared with the case where the tip of the upstream protrusion is not offset to the intake port side, the amount of cooling water passing through the priority cooling portion is increased, which also improves the cooling performance for the priority cooling portion.

Further, when the cylinder head is provided with a plurality of exhaust ports for each combustion chamber, it is desirable to set a portion in the region surrounded by the plug hole and the plurality of exhaust ports as the priority cooling portion. ..

Further, when the cylinder head is provided with one exhaust port for each combustion chamber, it is desirable to set a portion located between the plug hole and the exhaust port as the priority cooling portion.

The cross-sectional view which shows the structure about one Embodiment of a cylinder head. FIG. 2 is a cross-sectional view taken along the line 2-2 of FIG. An enlarged view of part A in FIG. FIG. 5 is a cross-sectional view taken along the line 4-4 of FIG. FIG. 3 is a cross-sectional view of a cylinder head in a modified example of the same embodiment. FIG. 3 is a cross-sectional view of a cylinder head in a modified example of the same embodiment.

Hereinafter, an embodiment in which the cylinder head of the internal combustion engine is embodied will be described with reference to FIGS. 1 to 4.
In the following, the direction in which the head cover is assembled in the cylinder head is referred to as "upward", the direction in which the cylinder block is assembled in the cylinder head is referred to as "downward", and these "vertical directions" are referred to as "height direction" of the cylinder head. Is indicated by an arrow H in each figure. Further, the direction orthogonal to the longitudinal direction and the vertical direction of the cylinder head is defined as the "width direction" of the cylinder head, and is indicated by an arrow W in each drawing.

FIG. 1 shows a cross-sectional view of the cylinder head 100 in the longitudinal direction. As shown in FIG. 1, a plurality of combustion chambers arranged linearly in the longitudinal direction of the cylinder head 100 (arrow L direction shown in FIG. 1) on the lower surface of the cylinder head 100 (the surface on which the cylinder block is assembled). 10 is formed. Further, the cylinder head 100 is provided in a direction intersecting the arrangement direction of the combustion chambers 10, and an intake port 20 and an exhaust port 30 connected to the combustion chamber 10 are formed. Two intake ports 20 and two exhaust ports 30 are formed in each combustion chamber 10. A bolt hole 150 into which a bolt for fixing the cylinder head 100 to the cylinder block is inserted is formed around the combustion chamber 10. Further, between the intake port 20 and the exhaust port 30, a plug mounting portion 40 having a plug hole 41 for mounting a spark plug is provided for each combustion chamber 10.

Between the intake port 20 and the exhaust port 30 of the cylinder head 100, a combustion chamber water jacket 110 that cools each combustion chamber 10 with cooling water of an internal combustion engine straddles the plurality of combustion chambers 10 described above. It is formed so as to extend in the arrangement direction of the combustion chambers 10 (longitudinal direction of the cylinder head 100).

As shown in FIG. 2 and FIG. 1 above, a first exhaust water jacket 120 for cooling each exhaust port 30 with cooling water of an internal combustion engine extends in the longitudinal direction of the cylinder head 100 below the exhaust port 30. Is formed in. Further, above the exhaust port 30, a second exhaust water jacket 125 for cooling each exhaust port 30 with the cooling water of the internal combustion engine is formed so as to extend in the longitudinal direction of the cylinder head 100.

As shown in FIG. 1, in the vicinity of one side surface of both side surfaces orthogonal to the arrangement direction of the combustion chamber 10 in the cylinder head 100, cooling water for introducing cooling water into the water jacket of the cylinder head 100 is introduced. An introduction hole 111 is formed. Further, a cooling water discharge hole 112 for discharging cooling water from the water jacket of the cylinder head 100 is formed on the other side surface of the side surfaces of the cylinder head 100 which are orthogonal to the arrangement direction of the combustion chamber 10. ..

The most upstream portion of the combustion chamber water jacket 110, the most upstream portion of the first exhaust water jacket 120, and the most upstream portion of the second exhaust water jacket 125 are connected to the cooling water introduction hole 111. Further, the most downstream part of the combustion chamber water jacket 110, the most downstream part of the first exhaust water jacket 120, and the most downstream part of the second exhaust water jacket 125 are connected to the cooling water discharge hole 112.

FIG. 3 shows a cross section orthogonal to the central axis PL (shown in FIG. 3 and FIG. 2 above) of the plug hole 41 in the plug mounting portion 40.
As shown in FIG. 3, the plug mounting portion 40 has an upstream projection 42 that protrudes so as to narrow toward the upstream side of the combustion chamber water jacket 110. More specifically, the plug mounting portion 40 is connected at a position on the upstream side of the combustion chamber water jacket 110, and is upstream including a pair of side surfaces in which the distance between the plug mounting portions 40 becomes narrower toward the upstream side of the combustion chamber water jacket 110. It has a side protrusion 42. The pair of side surfaces of the upstream side projection 42 is composed of a first side surface 42B which is a side surface on the intake port 20 side and a second side surface 42C which is a side surface of the exhaust port 30. Further, the portion where the first side surface 42B and the second side surface 42C are connected at a position on the upstream side of the water jacket 110 for the combustion chamber is the apex of the upstream side protrusion 42.

Further, as shown in FIG. 3, the plug mounting portion 40 has a downstream projection 43 that protrudes so as to narrow toward the downstream side of the combustion chamber water jacket 110. More specifically, the plug mounting portion 40 is connected at a position on the downstream side of the combustion chamber water jacket 110, and is downstream including a pair of side surfaces in which the distance between the plug mounting portions 40 becomes narrower toward the downstream side of the combustion chamber water jacket 110. It has a side protrusion 43. The pair of side surfaces of the downstream side projection 43 is composed of a third side surface 43B which is a side surface on the intake port 20 side and a fourth side surface 43C which is a side surface of the exhaust port 30. Further, the portion where the third side surface 43B and the fourth side surface 43C are connected at a position on the downstream side of the combustion chamber water jacket 110 is the apex of the downstream side protrusion 43.

The internal angle θ1 of the tip portion 42A located on the upstream side of the combustion chamber water jacket 110 in the upstream projection 42 is an acute angle. Further, the internal angle θ2 of the tip 43A located on the downstream side of the combustion chamber water jacket 110 in the downstream projection 43 is also an acute angle, and the internal angle θ1 of the tip 42A is smaller than the internal angle θ2 of the tip 43A. ..

Further, the tip portion 42A of the upstream side protrusion 42 and the tip portion 43A of the downstream side protrusion 43 are the same as the wall surface 110B on the exhaust port 30 side of the combustion chamber water jacket 110 in a cross section orthogonal to the central axis PL of the plug hole 41. It is provided at a position close to the wall surface 110A on the intake port 20 side of the water jacket 110 for the combustion chamber.

As shown in FIG. 3, an intake port side flow path 117 through which cooling water flows is formed for each combustion chamber 10 at a position on the intake port 20 side of the plug mounting portion 40 having the upstream side protrusion 42 and the downstream side protrusion 43. An exhaust port side flow path 115 through which cooling water flows is formed for each combustion chamber 10 at a position on the exhaust port 30 side of the plug mounting portion 40. The intake port side flow path 117 and the exhaust port side flow path 115 form a part of the water jacket 110 for the combustion chamber.

The first side surface 42B of the upstream projection 42 is substantially parallel to the wall surface 110A on the intake port 20 side of the combustion chamber water jacket 110. Further, the second side surface 42C of the upstream projection 42 is inclined with respect to the wall surface 110B on the exhaust port 30 side of the combustion chamber water jacket 110. More specifically, the second side surface 42C is inclined so as to approach the wall surface 110B toward the downstream side of the exhaust port side flow path 115, whereby the exhaust port side flow path 115 becomes the second side surface of the upstream side projection 42. The distance between the 42C and the wall surface 110B of the water jacket 110 for the combustion chamber is shorter toward the downstream side.

A portion where the temperature of the cylinder head 100 rises due to the addition of the amount of heat transferred from the spark plug attached to the plug hole 41 to the cylinder head 100 and the amount of heat transferred from the exhaust port 30 to the cylinder head 100, which exists in each combustion chamber 10. Is the priority cooling portion CZ, and the following portions are the priority cooling portions CZ in the cylinder head 100. That is, the cylinder head 100 is provided with a plurality of exhaust ports 30 for each combustion chamber 10, and the portion in the region surrounded by the plug hole 41 to which the spark plug is attached and each exhaust port 30 becomes the priority cooling portion CZ. There is.

The exhaust port side flow path 115 is formed so as to pass through the above-mentioned priority cooling portion CZ and the flow path cross-sectional area gradually decreases from the upstream side of the exhaust port side flow path 115 toward the priority cooling portion CZ. .. The exhaust port side flow path 115 is formed so that the cross-sectional area of the flow path gradually increases from the priority cooling portion CZ toward the downstream side of the exhaust port side flow path 115.

As shown in FIG. 4 and FIG. 3 above, it is the minimum value of the flow path cross-sectional area of the portion of the exhaust port side flow path 115 that passes through the priority cooling portion CZ, and the value for each combustion chamber 10 is the minimum cross-sectional area for each cylinder. When SE is used, each exhaust port side flow path 115 is formed so that the minimum cross-sectional area SE for each cylinder becomes larger as the priority cooling portion CZ located downstream of the water jacket 110 for the combustion chamber becomes larger. For example, in the present embodiment, four combustion chambers 10 are formed in the cylinder head 100, and the plurality of combustion chambers 10 are sequentially formed in the first combustion chamber 10A and the second combustion chamber from the upstream side of the combustion chamber water jacket 110. The chamber 10B, the third combustion chamber 10C, and the fourth combustion chamber 10D. Then, the minimum cross-sectional area SE for each cylinder in the priority cooling portion CZ of the first combustion chamber 10A is set to the minimum cross-sectional area SE1 for each cylinder, and the minimum cross-sectional area SE for each cylinder in the priority cooling portion CZ of the second combustion chamber 10B is set to the second. The minimum cross-sectional area for each cylinder is SE2. Further, the minimum cross-sectional area SE for each cylinder in the priority cooling portion CZ of the third combustion chamber 10C is set to the minimum cross-sectional area SE3 for each third cylinder, and the minimum cross-sectional area SE for each cylinder in the priority cooling portion CZ of the fourth combustion chamber 10D is the fourth. The minimum cross-sectional area for each cylinder is SE4. In this case, the size of the minimum cross-sectional area SE1 for each first cylinder SE1 to the minimum cross-sectional area SE4 for each fourth cylinder satisfies the relationship of "SE1 <SE2 <SE3 <SE4".

According to the present embodiment described above, the following effects can be obtained.
(1) As described above, in the cylinder head 100 provided with a plurality of exhaust ports 30 for each combustion chamber, the region surrounded by the plug mounting portion 40 and the plurality of exhaust ports 30 exists for each combustion chamber 10. It is a priority cooling part CZ.

Therefore, the exhaust port side flow path 115 is formed so as to pass through the priority cooling portion CZ and the flow path cross-sectional area gradually decreases from the upstream side of the exhaust port side flow path 115 toward the priority cooling portion CZ. .. Therefore, the flow velocity of the cooling water flowing through the exhaust port side flow path 115 increases from the upstream side of the exhaust port side flow path 115 toward the priority cooling portion CZ. As the flow velocity of the cooling water increases, the amount of heat taken away by the cooling water per unit time increases, so that the cooling performance for the priority cooling portion CZ can be improved.

(2) Further, as shown in FIG. 3, when the cooling water CW flows into the combustion chamber water jacket 110 from the cooling water introduction hole 111, the flowing cooling water CW is the upstream protrusion of the plug mounting portion 40. The cooling water CW flowing through the intake port side flow path 117 and the cooling water CW flowing through the exhaust port side flow path 115 are separated by 42. Here, the upstream projection 42 projects so as to narrow toward the upstream side of the combustion chamber water jacket 110, and the cross section orthogonal to the central axis PL of the plug hole 41 has a substantially triangular shape. The tip 42A of the upstream projection 42 having a substantially triangular shape faces the upstream side of the water jacket 110 for the combustion chamber. Therefore, when the cooling water flowing from the upstream of the plug mounting portion 40 is diverted by the upstream projection 42, the cooling water is diverted from the relatively sharp tip portion 42A as a base point, so that the cooling water CW There is little change in the flow direction, and stagnation is unlikely to occur. Therefore, the decrease in the flow velocity of the cooling water CW at the time of diversion can be suppressed, and the decrease in the flow velocity of the cooling water CW flowing into the exhaust port side flow path 115 can be suppressed, which also enhances the cooling performance for the priority cooling portion CZ. be able to.

(3) As shown in FIG. 3 and the like above, the tip portion 42A of the upstream side projection 42 has a cross section orthogonal to the central axis PL of the plug hole 41 and a wall surface 110B on the exhaust port 30 side of the combustion chamber water jacket 110. It is provided at a position closer to the wall surface 110A on the intake port 20 side of the water jacket 110 for the combustion chamber. That is, the tip portion 42A of the upstream side protrusion 42 is offset to the intake port 20 side. Therefore, when the cooling water flowing from the upstream of the plug mounting portion 40 is divided by the upstream projection 42, the cooling water flows into the exhaust port side flow path 115 rather than the cooling water CW flowing into the intake port side flow path 117. Water CW is more. Therefore, the amount of cooling water CW passing through the priority cooling portion CZ is larger than that in the case where the tip portion 42A of the upstream side protrusion 42 is not offset to the intake port 20 side, and this also causes the cooling performance for the priority cooling portion CZ. Will increase.

(4) As shown in FIG. 3 above, the plug mounting portion 40 has a downstream protrusion 43. The downstream projection 43 projects so as to narrow toward the downstream side of the combustion chamber water jacket 110, and the cross section orthogonal to the central axis PL of the plug hole 41 is substantially triangular. The tip 43A of the downstream projection 43 faces the downstream side of the combustion chamber water jacket 110. Therefore, when the cooling water CW that has passed through the exhaust port side flow path 115 and the cooling water CW that has passed through the intake port side flow path 117 merge downstream of the downstream projection 43, the cooling water is less likely to stagnate. .. Therefore, for example, it is possible to suppress a decrease in the flow velocity of the cooling water that has merged at a position downstream of the downstream protrusion 43.

(5) Since the exhaust port side flow path 115 is formed so that the cross-sectional area of the flow path gradually decreases from the upstream side of the exhaust port side flow path 115 toward the priority cooling portion CZ, the priority cooling portion CZ is formed. The pressure loss is relatively large in the passing part. Therefore, when the cooling water that has passed through one exhaust port side flow path 115 flows into the next exhaust port side flow path 115 located downstream, some of the cooling water is not the exhaust port side flow path 115. It easily flows into the intake port side flow path 117, and the flow rate of the cooling water may decrease as the exhaust port side flow path 115 located downstream.

In this respect, in the present embodiment, each exhaust port side flow path 115 is formed so that the minimum cross-sectional area SE for each cylinder becomes larger as the priority cooling portion CZ located downstream of the water jacket 110 for the combustion chamber becomes larger. Therefore, the pressure loss becomes smaller as the exhaust port side flow path 115 located downstream of the combustion chamber water jacket 110, so that the cooling water that has passed through one exhaust port side flow path 115 flows to the next exhaust port located downstream. When flowing into the side flow path 115, it tends to flow into the exhaust port side flow path 115 instead of the intake port side flow path 117. Therefore, it is possible to suppress a decrease in the flow rate of the cooling water in each exhaust port side flow path 115.

In addition, the said embodiment can also be carried out in the following embodiment which modified this as appropriate.
As shown in FIG. 5, the intake water jacket 130 for cooling each intake port 20 with the cooling water of the internal combustion engine may be formed so as to extend in the longitudinal direction of the cylinder head 100. The most upstream portion of the intake water jacket 130 is preferably connected to the cooling water introduction hole 111. Further, it is preferable that the most downstream portion of the intake water jacket 130 is connected to the cooling water discharge hole 112.

Further, as shown by the alternate long and short dash line in FIG. 5, when the in-cylinder injection valve 200 for directly injecting fuel into the combustion chamber 10 is provided on the intake port 20 side, the tip of the in-cylinder injection valve 200 is provided. By narrowing the flow path of the intake water jacket 130 in the vicinity of the portion, the flow path cross-sectional area SN of the intake water jacket 130 in the throttle portion may be narrowed. In this case, by providing such a throttle portion, the flow velocity of the cooling water increases in the vicinity of the tip portion of the in-cylinder injection valve 200 in the intake water jacket 130, so that the flow velocity of the cooling water increases in the vicinity of the tip portion of the in-cylinder injection valve 200. Cooling effect can be enhanced.

-The first exhaust water jacket 120 may be omitted, or the second exhaust water jacket 125 may be omitted.
-The number of intake ports 20 and the number of exhaust ports 30 formed in one combustion chamber 10 can be appropriately changed.

As shown in FIG. 6, in the case of the cylinder head 100 provided with one exhaust port 30 for each combustion chamber 10, the portion located between the plug hole 41 and the exhaust port 30 is the priority cooling portion CZ. It has become. Therefore, by forming the exhaust port side flow path 115 so that the exhaust port side flow path 115 passes between the plug hole 41 and the exhaust port 30, it is possible to obtain the same effect as that of the above embodiment. it can.

The internal angle θ1 of the tip portion 42A may be larger than the internal angle θ2 of the tip portion 43A. Further, the internal angle θ1 of the tip portion 42A and the internal angle θ2 of the tip portion 43A may be the same.
-As shown in FIGS. 1 and 3, the tip portion 42A of the upstream side protrusion 42 and the tip portion 43A of the downstream side protrusion 43 are both provided at positions offset to the intake port 20 side. In addition, only the tip 42A of the upstream protrusion 42 may be offset to the intake port 20 side, or only the tip 43A of the downstream protrusion 43 may be offset to the intake port 20 side.

-For example, the downstream projection 43 may be omitted by forming the downstream portion of the combustion chamber water jacket 110 in an arc shape in the plug mounting portion 40.
The upstream projection 42 has a shape including a pair of the first side surface 42B and the second side surface 42C, but has a shape that protrudes toward the upstream side of the combustion chamber water jacket 110 in another shape. It may be. Similarly, the downstream projection 43 has a shape including a pair of the third side surface 43B and the fourth side surface 43C, but in another shape, the downstream projection 43 projects so as to narrow toward the upstream side of the combustion chamber water jacket 110. The shape may be changed.

Each exhaust port side flow path 115 is formed so that the minimum cross-sectional area SE for each cylinder becomes larger toward the priority cooling portion CZ located downstream of the water jacket 110 for the combustion chamber. In addition, each exhaust port side flow path 115 may be formed so that the minimum cross-sectional area SE for each cylinder is the same.

10 ... Combustion chamber, 10A ... 1st combustion chamber, 10B ... 2nd combustion chamber, 10C ... 3rd combustion chamber, 10D ... 4th combustion chamber, 20 ... Intake port, 30 ... Exhaust port, 40 ... Plug mounting part, 41 ... plug hole, 42 ... upstream protrusion, 42A ... tip, 42B ... first side surface, 42C ... second side, 43 ... downstream protrusion, 43A ... tip, 43B ... third side, 43C ... fourth side, 100 ... Cylinder head, 110 ... Water jacket for combustion chamber, 110A ... Wall surface on the intake port side of the water jacket for the combustion chamber, 110B ... Wall surface on the exhaust port side of the water jacket for the combustion chamber, 111 ... Cooling water introduction hole, 112 ... Cooling water discharge hole, 115 ... Exhaust port side flow path, 117 ... Intake port side flow path, 120 ... First exhaust water jacket, 125 ... Second exhaust water jacket, 130 ... Intake water jacket, 150 ... Bolt hole , 200 ... In-cylinder injection valve, CZ ... Priority cooling part, PL ... Central axis of plug hole, SE ... Minimum cross-sectional area for each cylinder.

Claims (4)

Between a plurality of combustion chambers arranged in a straight line, an intake port and an exhaust port provided in directions intersecting the arrangement direction of the combustion chambers and connected to the combustion chamber, and the intake port and the exhaust port. A water jacket that is formed in the above and extends in the arrangement direction of the combustion chambers across the plurality of combustion chambers to cool the combustion chambers, and is formed between the intake port and the exhaust port and ignites. A cylinder head of an internal combustion engine having a plug hole for attaching a plug and a plug attachment portion independently provided for each combustion chamber.
The water jacket
An intake port side flow path located on the intake port side of the plug mounting portion and provided for each combustion chamber, and an exhaust port side flow path located on the exhaust port side of the plug mounting portion and provided for each combustion chamber. It has an exhaust port side flow path and
When the portion where the temperature of the cylinder head rises due to the addition of the amount of heat transferred from the spark plug attached to the plug hole and the amount of heat transferred from the exhaust port and the portion existing in each combustion chamber is designated as the priority cooling portion. The exhaust port side flow path is formed so as to pass through the priority cooling portion and the flow path cross-sectional area gradually decreases from the upstream of the exhaust port side flow path toward the priority cooling portion.
The plug mounting portion has an upstream projection protruding toward the upstream side of the water jacket and a downstream projection protruding toward the downstream side of the water jacket.
The tip of the upstream protrusion and the tip of the downstream protrusion are closer to the wall surface of the water jacket on the intake port side than the wall surface of the water jacket on the exhaust port side in a cross section orthogonal to the central axis of the plug hole, respectively. The cylinder head of the internal combustion engine provided at the position . It is located downstream of the water jacket when it is the minimum value of the flow path cross-sectional area of the portion of the exhaust port side flow path that passes through the priority cooling portion and the value for each combustion chamber is the minimum cross-sectional area for each cylinder. The cylinder head of an internal combustion engine according to claim 1, wherein the exhaust port side flow path is formed so that the minimum cross-sectional area for each cylinder becomes larger as the priority cooling portion is formed. Each combustion chamber is equipped with a plurality of exhaust ports.
The cylinder head of an internal combustion engine according to claim 1 or 2 , wherein the priority cooling portion is a portion in a region surrounded by the plug hole and the plurality of exhaust ports. Each combustion chamber is equipped with one exhaust port.
The cylinder head of an internal combustion engine according to claim 1 or 2 , wherein the priority cooling portion is a portion located between the plug hole and the exhaust port.