Cylinder head structure

Abstract

To efficiently cool an EGR gas which passes an EGR passage in a cylinder head when forming the EGR passage at the cylinder head.SOLUTION: A cylinder head structure comprises an in-head EGR passage 70 which is formed in a cylinder head main body 13, a water jacket 20 in which a cooling water derivation part 21 is arranged at an end part in a cylinder row direction, and a water outlet 30 connected to an outlet-side wall part being a wall part at which the cooling water derivation part 21 of the cylinder head main body 13 is arranged. A recess which is formed so as to adjoin the cooling water derivation part 21 via a bulkhead part is formed at the outlet-side wall part, the water outlet 30 has a guide part for introducing a part of cooling water from the water jacket 20 to the recess, and the in-head EGR passage 70 is formed so as to be located at the lower part of the cooling water derivation part 21 and the recess.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The technology disclosed herein belongs to the technical field relating to cylinder head structures. [Background technology]

[0002] 2. Description of the Related Art In an engine having an EGR passage for recirculating a portion of the exhaust gas to an intake passage, a structure in which a portion of the EGR passage is formed within a cylinder head has been known.

[0003] For example, Patent Document 1 discloses a cylinder head structure in which an in-head EGR passage formed in a cylinder head has an exhaust-side portion extending in a straight line from the exhaust-side sidewall, and an intake-side portion bending from the inner end of the exhaust-side portion and extending in a straight line to the intake-side sidewall, and in which a cooling water passage is arranged below the intake-side portion and along the intake-side portion so as to overlap with the intake-side portion when viewed from the axial direction of the cylinder. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-174171 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, since gas with a relatively low temperature basically tends to move downward, if the cooling water passage is disposed below the in-head EGR passage, the upper portion of the in-head EGR passage is difficult to cool. In other words, the structure described in Patent Document 1 can only exchange heat with a portion of the EGR gas passing through the in-head EGR passage. Therefore, there is room for improvement in terms of improving the cooling efficiency of the in-head EGR passage.

[0006] The technology disclosed herein has been made in consideration of these points, and its purpose is to efficiently cool the EGR gas passing through the EGR passage in the cylinder head when an EGR passage is formed in the cylinder head. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the technology disclosed herein is directed to a cylinder head structure in which an in-head EGR passage, which is a part of an EGR passage, is formed in a cylinder head main body of a multi-cylinder engine having an EGR passage for recirculating a part of the exhaust gas to an intake passage, and the cylinder head main body has a water jacket formed in the cylinder head main body, through which cooling water flows from one end side to the other end side of the cylinder head main body in the cylinder row direction, and which has a cooling water outlet part at the other end in the cylinder row direction, and a cooling water introduction part communicating with the cooling water outlet part of the water jacket, and a water outlet connected to an outlet side wall portion which is a wall portion in which the cooling water discharge portion is provided, wherein the outlet side wall portion has a recess formed therein which is adjacent to the cooling water discharge portion in the width direction of the cylinder head body via a partition portion and is recessed toward the one end side in the cylinder row direction, the water outlet having a guide portion which guides a portion of the cooling water from the water jacket to the recess, and the in-head EGR passage is formed so as to extend in the width direction of the cylinder head body and be located below the cooling water discharge portion and the recess.

[0008] With this configuration, the cooling water passes above the in-head EGR passage, so the EGR gas can be efficiently cooled by utilizing heat flow. Also, because a portion of the cooling water is guided to the recess by the guide portion, the cooling water that flows into the recess can also cool the in-head EGR passage. This allows the in-head EGR passage to be cooled over a wide area, and the EGR gas passing through the EGR passage in the cylinder head can be efficiently cooled.

[0009] In the cylinder head structure, the recesses may be provided on both sides in the width direction with the cooling water outlet portion between them, and the guide portions may be formed corresponding to the recesses, respectively.

[0010] With this configuration, the in-head EGR passage can be cooled over a wider area, thereby more efficiently cooling the EGR gas passing through the EGR passage in the cylinder head.

[0011] In one embodiment of the cylinder head structure, the guide portion has a barrier portion that collides with a portion of the cooling water that has passed through the water jacket and changes the flow direction of the portion of the cooling water in the width direction, and a rib portion that is spaced apart from the partition portion in the width direction and extends from the barrier portion toward the recess.

[0012] According to this configuration, a part of the cooling water collides with the barrier portion and flows in the width direction, and then collides with the rib portion and flows toward the recess. This allows the cooling water to be efficiently introduced into the recess. As a result, the EGR gas passing through the EGR passage in the cylinder head can be more efficiently cooled.

[0013] In the above embodiment, the other end of the partition in the cylinder row direction and the one end of the rib in the cylinder row direction may be positioned at the same position in the cylinder row direction.

[0014] According to this configuration, the cooling water can be introduced into the recess as efficiently as possible, thereby more efficiently cooling the EGR gas passing through the EGR passage in the cylinder head.

[0015] In the cylinder head structure, one end of the in-head EGR passage in the width direction may be a curved portion that curves and extends toward the other end in the cylinder row direction, and a recess formed on the one end side in the width direction may be formed with a hole that extends in the cylinder row direction along the curved portion and through which cooling water is introduced.

[0016] This configuration makes it possible to efficiently cool the curved portion where the flow of EGR gas is likely to stagnate, thereby more efficiently cooling the EGR gas passing through the EGR passage in the cylinder head.

[0017] In the cylinder head structure, the in-head EGR passage may be configured such that a cross section at a portion overlapping with the cooling water outlet portion has a flattened circular shape with a major axis extending in a cylinder row direction.

[0018] With this configuration, the contact area between the cooling water and the portion forming the in-head EGR passage can be made as large as possible, thereby more efficiently cooling the EGR gas passing through the in-cylinder head EGR passage. Effect of the Invention

[0019] As described above, according to the technique disclosed herein, when an EGR passage is formed in a cylinder head, the EGR gas passing through the EGR passage in the cylinder head can be efficiently cooled. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a schematic diagram of an engine system having an engine equipped with a cylinder head according to this embodiment. [Diagram 2] FIG. 2 is a cross-sectional view showing a water jacket portion of the cylinder head body. [Diagram 3] FIG. 3 is a cross-sectional perspective view of the cylinder head, in which the cylinder head body is cut along a plane extending in the front-rear and up-down directions. [Figure 4] FIG. 4 is a front view of the cylinder head body. [Diagram 5] FIG. 5 is a perspective view of the cylinder head. [Figure 6] FIG. 6 is a front view of the cylinder head. [Figure 7] FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. [Figure 8] FIG. 8 is a cross-sectional view taken along a line VIII-VIII in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, exemplary embodiments will be described in detail with reference to the drawings. In the following description, the front, rear, left, right, top, and bottom of a vehicle will be simply referred to as the front, rear, left, right, top, and bottom, respectively. With respect to the left-right direction, the left side when looking from the rear to the front side is referred to as the left, and the right side is referred to as the right.

[0022] 1 is a schematic diagram of an engine system having an engine with a cylinder head structure according to this embodiment. The engine 1 is a multi-cylinder engine in which a plurality of cylinders (not shown) are arranged in a cylinder row direction (perpendicular to the plane of the drawing). The engine 1 is placed vertically in an engine room of a vehicle so that the cylinder row direction is the front-rear direction.

[0023] The engine 1 has a cylinder block 11 in which each cylinder is formed, and a cylinder head 12 arranged on the upper side of the cylinder block 11. The cylinder head 12 has a cylinder head body 13 connected to the cylinder block 11, and a water outlet 30 connected to a rear wall portion 13a (see Figs. 2 and 3) of the cylinder head body 13. An intake passage 3 for supplying intake air to each cylinder is connected to one side of the cylinder head body 13 in a width direction perpendicular to the cylinder row direction and the up-down direction, specifically, to the left side of the cylinder head body 13. In addition, an exhaust passage 5 for discharging exhaust gas from each cylinder is connected to the right side (the other side in the width direction) of the cylinder head body 13.

[0024] Between the intake passage 3 and the exhaust passage 5, an EGR passage 7 is formed for recirculating a portion of the exhaust gas from the exhaust passage 5 to the intake passage 3. A portion of the EGR passage 7 is formed in the cylinder head 12. Of the EGR passage 7, an in-head EGR passage 70 formed in the cylinder head 12 is formed integrally with other portions of the cylinder head 12 by casting. The configuration of the in-head EGR passage 70 will be described in detail later. Incidentally, most of the in-head EGR passage 70 is formed in the cylinder head body 13, and an outlet portion is formed in the water outlet 30. In this specification, the in-head EGR passage 70 also includes the portion formed in the water outlet 30.

[0025] 2, a water jacket 20 is formed inside the cylinder head body 13, through which cooling water flows from the front side to the rear side of the cylinder head body 13 (from one end side to the other end side in the cylinder row direction). Although detailed illustration is omitted, the water jacket 20 is formed so as to pass around the intake ports 14 and exhaust ports 15 connected to each cylinder, respectively, and exit to the rear side. The cooling water passing through the water jacket 20 cools the intake ports 14 and exhaust ports 15, and also cools the EGR gas passing through the in-head EGR passage 70.

[0026] As shown in Figs. 3 and 4, a cooling water outlet 21 serving as an outlet of the water jacket 20 is provided at the rear end of the cylinder head body 13. The cooling water outlet 21 is a portion that discharges the cooling water that has passed through the water jacket 20 from the cylinder head body 13. The cooling water outlet 21 is provided at the center in the left-right direction. The cooling water outlet 21 is substantially rectangular when viewed from the front side, and has a relatively wide flow passage cross-sectional area. The cooling water outlet 21 has an opening in the rear wall 13a of the cylinder head body 13, and communicates with a cooling water introduction part 31 of the water outlet 30 (described later) through this opening. For this reason, the rear wall 13a of the cylinder head body 13 corresponds to an outlet side wall part, which is a wall part in the cylinder head body 13 where the cooling water outlet 21 is provided.

[0027] A part of an in-head EGR passage 70 is formed at the rear end of the cylinder head body 13. The in-head EGR passage 70 is located below the cooling water outlet portion 21. In other words, a part of the in-head EGR passage 70 (a lateral extension portion 73 described later) overlaps with the cooling water outlet portion 21 when viewed from the rear side.

[0028] As shown in FIG. 2, an inlet portion 71 of the in-head EGR passage 70 opens into a right side wall portion of the cylinder head body 13. The in-head EGR passage 70 extends from the inlet portion 71 in the width direction (left-right direction) of the cylinder head body 13. Specifically, the in-head EGR passage 70 has an inclined portion 72 inclined rearward toward the left side from the inlet portion 71, a horizontally extending portion 73 extending straight toward the left side from the left front end of the inclined portion, and a curved portion 74 extending in a curved manner toward the rear side from the left end of the horizontally extending portion 73. The rear end of the curved portion 74 is a rear opening portion 75 that opens toward the rear side. The rear opening portion 75 communicates with a vertically extending portion 76 (see FIG. 8) formed in the water outlet 30.

[0029] As shown in Fig. 3, the cross section of the laterally extending portion 73 of the in-head EGR passage 70 has a flattened circular shape with its major axis extending in the front-rear direction. On the other hand, as shown in Fig. 4, the curved portion 74 and the rear opening 75 of the in-head EGR passage 70 have a perfect circular shape.

[0030] As shown in FIG. 4, in the rear wall 13a, two recesses 23, 24 are formed on both sides in the left-right direction of the cooling water outlet portion 21, adjacent to each other via the partitions 17, 18, and recessed forward. The two recesses 23, 24 are provided on both sides in the left-right direction, sandwiching the cooling water outlet portion 21 therebetween. In the following description, the recess on the right side is referred to as the first recess 23, and the recess on the left side is referred to as the second recess 24. The partition between the cooling water outlet portion 21 and the first recess 23 is referred to as the first partition 17, and the partition between the cooling water outlet portion 21 and the second recess 24 is referred to as the second partition 18.

[0031] The first recess 23 has a substantially trapezoidal shape. The lower side of the first recess 23 extends along the upper end of the inclined portion 72 of the in-head EGR passage 70. A part of the laterally extending portion 73 of the in-head EGR passage 70 overlaps with the lower portion of the first recess 23 when viewed from the rear side. In other words, the in-head EGR passage 70 is formed so as to be located below the first recess 23. The right and front portion of the first recess 23 forms a recess 23a (see FIG. 7 ) that is recessed further forward than the other portions of the first recess 23. The recess 23a extends along the inclined portion 72.

[0032] The second recess 24 has an elongated arc shape. The second recess 24 extends along the upper and left side of the rear opening 75 of the head EGR passage 70. That is, the head EGR passage 70 is formed to be located at the lower part of the second recess 24. A through hole 24a communicating with the cooling water outlet 21 is formed at the right end of the second recess 24. The through hole 24a is a hole through which the cooling water that has passed through the water jacket 20 flows. At the left and lower end of the second recess 24, two bottomed holes 24b extending toward the front side are formed in a vertical line along the curved portion 74 of the head EGR passage 70. The holes 24b are holes into which the cooling water discharged from the cooling water outlet 21 is introduced, as will be described in detail later.

[0033] 5, the water outlet 30 is connected to a portion of the rear wall portion 13a of the cylinder head body 13 at the same height as the cooling water outlet portion 21. The water outlet 30 is block-shaped and has a plurality of water channels formed therein.

[0034] The water outlet 30 has a cooling water inlet 31 (see FIG. 7) into which the cooling water discharged from the cooling water outlet 21 is introduced, and a plurality of (four in this example) distribution paths 32 for distributing the cooling water from the cooling water inlet 31 to each water path. The plurality of distribution paths 32 distribute the cooling water to the water paths leading to the transmission, heater, radiator, etc. The distribution paths 32 have two openings in the rear wall of the water outlet 30, one in the left side wall, and one in the right side wall.

[0035] The water outlet 30 has a part of the in-head EGR passage 70. Specifically, the water outlet 30 has a vertically extending portion 76 (see FIG. 8) that communicates with the curved portion 74 via a rear opening 75 of the in-head EGR passage 70 and extends in the front-rear direction, and an upwardly extending portion 77 (see FIG. 6) that extends obliquely from the rear end of the vertically extending portion 76 toward the left and upward. As shown in FIG. 6, the upper end of the upwardly extending portion 77 is expanded in a flange shape. A pipe for introducing the EGR gas that has passed through the in-head EGR passage 70 into the intake passage 3 is connected to the upwardly extending portion 77.

[0036] 7 and 8, the water outlet 30 has first and second guide portions 33, 34 that guide a portion of the cooling water from the water jacket 20 to the first and second recesses 23, 24. That is, the guide portions 33, 34 are formed corresponding to the recesses 23, 24, respectively.

[0037] The first guide portion 33 guides the cooling water discharged from the cooling water outlet portion 21 to the first recess 23. The first guide portion 33 has a first barrier portion 33a that collides with a portion of the cooling water discharged from the cooling water outlet portion 21 and changes the flow direction of the portion of the cooling water to the right, and a first rib portion 33b that is provided separated from the first partition portion 17 in the left-right direction and extends from the first barrier portion 33a toward the first recess 23.

[0038] The first barrier portion 33a overlaps in the front-rear direction with the right portion of the cooling water outlet portion 21. The first barrier portion 33a changes the flow of the cooling water that has passed through the right portion of the cooling water outlet portion 21 to the right, as shown by the arrows in Figs. 7 and 8.

[0039] As shown in Figs. 7 and 8, the first rib portion 33b is located on the right side of the first partition wall portion 17. The first rib portion 33b extends straight from the first barrier portion 33a toward the first recessed portion 23 in the front-rear direction. The front end of the first rib portion 33b and the rear end of the first partition wall portion 17 are located at the same position in the front-rear direction. In other words, when the water outlet 30 is attached to the cylinder head body 13, the front end of the first rib portion 33b and the rear end of the first partition wall portion 17 are located on the same plane in the front-rear direction. As shown by the arrows in Figs. 7 and 8, the first rib portion 33b changes the flow of the cooling water, which has been turned to the right by the first barrier portion 33a, to the forward direction. This allows the cooling water to be actively introduced into the first recessed portion 23. The cooling water introduced into the first recess 23 passes through the inside of the first recess 23 so as to pass above the laterally extending portion 73 and the inclined portion 72 of the in-head EGR passage 70, and then is introduced into the distribution passage 32.

[0040] The second guide portion 34 guides the cooling water discharged from the through hole 24a of the second recess 24 through the water jacket 20, so that the cooling water passes through the second recess 24. As shown in Fig. 7 and Fig. 8, the second guide portion 34 has a second barrier portion 34a that collides with the cooling water discharged from the through hole 24a of the second recess 24 and changes the flow direction of the cooling water to the left, and a second rib portion 34b that is provided separated from the second partition wall portion 18 in the left-right direction and extends from the second barrier portion 34a toward the second recess 24.

[0041] The second barrier portion 34a overlaps in the front-rear direction with the through hole 24a of the second recess 24. The second barrier portion 34a redirects the flow of the cooling water that has passed through the through hole 24a of the second recess 24 to the left, as shown by the arrow in FIG.

[0042] As shown in Figs. 7 and 8, the second rib portion 34b is located on the left side of the second partition wall portion 18. The second rib portion 34b extends straight from the second barrier portion 34a toward the second recess 24 in the front-rear direction. The front end of the second rib portion 34b and the rear end of the second partition wall portion 18 are located at the same position in the front-rear direction. In other words, when the water outlet 30 is attached to the cylinder head body 13, the front end of the second rib portion 34b and the rear end of the second partition wall portion 18 are located on the same plane in the front-rear direction. As shown by the arrow in Fig. 7, the second rib portion 34b changes the flow of the cooling water, which has been turned to the right by the second barrier portion 34a, to the forward direction. This allows the cooling water to be actively introduced into the second recess 24. The cooling water introduced into the second recess 24 is introduced into the distribution passage 32 after passing through the second recess 24 so as to pass above the curved portion 74 of the in-head EGR passage 70.

[0043] Moreover, the cooling water introduced into the second recess 24 reaches the left and lower end of the second recess 24, and then is introduced into each of the holes 24b, filling each of the holes 24b.

[0044] 8, at a position facing the hole 24b in the water outlet 30 (strictly speaking, the upper hole 24b), a part of the distribution passage 32 extends along the vertically extending portion 76 of the in-head EGR passage 70. Also, on the right side of the vertically extending portion 76, a part of the distribution passage 32 extends along the vertically extending portion 76. In other words, the vertically extending portion 76 is sandwiched in the left-right direction by the two distribution passages 32. This allows the EGR gas in the vertically extending portion 76 to be efficiently cooled.

[0045] Here, when a part of the EGR passage 7 is provided in the cylinder head 12 as in this embodiment, it is necessary to appropriately cool the EGR gas passing through the in-head EGR passage 70 by the cooling water passing through the cylinder head 12. In contrast, in this embodiment, the rear wall portion 13a of the cylinder head body 13 is formed with a first recess 23 and a second recess 24 that are provided adjacent to each other in the left-right direction with respect to the cooling water outlet portion 21 via a first partition portion 17 and a second partition portion 18 and are recessed forward, the water outlet 30 has a first guide portion 33 and a second guide portion 34 that guide a part of the cooling water from the water jacket 20 to the first recess 23 and the second recess 24, and the in-head EGR passage 70 is formed to extend in the left-right direction and to be located below the cooling water outlet portion 21, the first recess 23, and the second recess 24. As a result, the cooling water passes above the in-head EGR passage 70, so that the EGR gas can be efficiently cooled by utilizing heat flow. Furthermore, because a portion of the cooling water is guided to the first recess 23 and the second recess 24 by the first guiding portion 33 and the second guiding portion 34, the in-head EGR passage 70 can also be cooled by the cooling water that flows into the first recess 23 and the second recess 24. This makes it possible to cool the in-head EGR passage 70 over a wide area, and therefore makes it possible to efficiently cool the EGR gas passing through the in-head EGR passage 70.

[0046] In the present embodiment, the first and second guide portions 33, 34 include a first barrier portion 33a and a second barrier portion 34a that collide with a portion of the cooling water that has passed through the water jacket 20 and change the flow direction of the portion of the cooling water to the left-right direction, and a first rib portion 33b and a second rib portion 34b that are provided separately from the first partition portion 17 and the second partition portion 18 in the left-right direction and extend from the first barrier portion 33a and the second barrier portion 34a toward the first recess 23 and the second recess 24. As a result, a portion of the cooling water collides with the first barrier portion 33a and the second barrier portion 34a and flows in the left-right direction, respectively, and then collides with the first rib portion 33b and the second rib portion 34b and flows toward the first recess 23 and the second recess 24, respectively, so that the cooling water can be efficiently introduced into the first recess 23 and the second recess 24. As a result, the EGR gas passing through the in-head EGR passage 70 can be more efficiently cooled.

[0047] In this embodiment, the rear ends of the first partition wall 17 and the second partition wall 18 and the front ends of the first rib portion 33b and the second rib portion 34b are located at the same position in the front-rear direction. This allows the cooling water to be introduced into the first recess 23 and the second recess 24 as efficiently as possible. As a result, the EGR gas passing through the in-head EGR passage 70 can be cooled more efficiently.

[0048] In this embodiment, the left end (the end on the intake side) of the in-head EGR passage 70 is a curved portion 74 that curves and extends toward the rear, and the second recess 24 is formed with a hole 24b that extends in the front-rear direction along the curved portion 74 and through which cooling water is introduced. This makes it possible to efficiently cool the curved portion 74, where the flow of EGR gas is likely to be stagnant. As a result, the EGR gas passing through the in-head EGR passage 70 can be cooled more efficiently.

[0049] In the present embodiment, the water outlet 30 is provided with a vertical extension portion 76 that communicates with the curved portion 74 of the in-head EGR passage 70 and extends in the front-rear direction, and an upward extension portion 77 that extends obliquely from the rear end of the vertical extension portion 76 toward the left and upper side, and the vertical extension portion 76 is sandwiched in the left-right direction by two distribution passages 32 of the water outlet 30. That is, in the flow direction of the EGR gas, the EGR gas tends to stagnate in the vertical extension portion 76 located immediately upstream of the upward extension portion 77. As in the present embodiment, the distribution passages 32 are provided on the left and right sides of the vertical extension portion 76, respectively, so that the EGR gas in the vertical extension portion 76 can be efficiently cooled. As a result, the EGR gas passing through the in-head EGR passage 70 can be more efficiently cooled.

[0050] In this embodiment, the cross section of the in-head EGR passage 70 at the portion overlapping with the cooling water outlet portion 21 has a flattened circular shape with a major axis extending in the cylinder row direction. This makes it possible to maximize the contact area between the portion forming the in-head EGR passage 70 and the cooling water. As a result, the EGR gas passing through the in-head EGR passage 70 can be cooled more efficiently.

[0051] (Other embodiments) The technology disclosed herein is not limited to the above-described embodiment, and may be substituted without departing from the spirit and scope of the claims.

[0052] For example, in the above-described embodiment, the first recess 23 is provided on the right side of the cooling water outlet portion 21, and the second recess 24 is provided on the left side of the cooling water outlet portion 21. However, this is not limited to the above, and only one of the first recess 23 or the second recess 24 may be provided.

[0053] In the above embodiment, the engine 1 is vertically mounted so that the cylinders are aligned in the front-rear direction. However, the engine 1 may be horizontally mounted so that the cylinders are aligned in the left-right direction. In this case, the width direction of the cylinder head 12 is the front-rear direction.

[0054] The above-described embodiments are merely illustrative and should not be construed as limiting the scope of the present disclosure. The scope of the present disclosure is defined by the claims, and all modifications and variations within the scope of the claims are within the scope of the present disclosure. [Industrial Applicability]

[0055] The technology disclosed herein is useful when forming a part of an EGR passage in a cylinder head body of a multi-cylinder engine having an EGR passage for recirculating a part of the exhaust gas to the intake passage. [Explanation of symbols]

[0056] 1 Engine 12. Cylinder head 13 Cylinder head body 13a Rear wall (exit side wall) 17 First bulkhead part 18 Second bulkhead section 20 Water Jacket 21 Cooling water outlet 23 First recess 24 Second recess 24b Hole 31 Cooling water inlet 33 1st Information Department 33a First barrier section 33b First rib 34 2nd Information Department 34a Second barrier section 34b Second rib section

Claims

1. A cylinder head structure for a multi-cylinder engine having an EGR passage for recirculating a portion of exhaust gas to an intake passage, the cylinder head structure including an in-head EGR passage that is a part of the EGR passage, a water jacket formed within the cylinder head body, through which cooling water flows from one end side to the other end side of the cylinder head body in a cylinder row direction, and which has a cooling water outlet portion provided at the other end side in the cylinder row direction; a water outlet having a cooling water inlet portion communicating with the cooling water outlet portion of the water jacket and connected to an outlet side wall portion, which is a wall portion of the cylinder head body on which the cooling water outlet portion is provided, a recess formed in the outlet side wall portion, the recess being recessed toward the one end portion in the cylinder row direction and adjacent to the cooling water outlet portion in the width direction of the cylinder head body with a partition wall therebetween; the water outlet has a guide portion that guides a portion of the cooling water from the water jacket to the recess, a cylinder head body that is provided with a cooling water outlet portion and an EGR passage that is disposed below the cooling water outlet portion and the recessed portion;

2. 2. The cylinder head structure according to claim 1, The recesses are provided on both sides of the cooling water outlet portion in the width direction, A cylinder head structure, wherein the guide portions are formed corresponding to the respective recesses.

3. 3. The cylinder head structure according to claim 1, a partition wall portion provided in the partition and spaced apart from the barrier portion in the width direction, the partition wall portion being spaced apart from the barrier portion in the width direction and extending from the barrier portion toward the recessed portion.

4. The cylinder head structure according to claim 3, a first end of the partition portion in the cylinder row direction and a first end of the rib portion in the cylinder row direction, the first end being located at the same position in the cylinder row direction.

5. The cylinder head structure according to any one of claims 1 to 4, one end of the in-head EGR passage in the width direction is a curved portion that curves and extends toward the other end in the cylinder row direction, a recess formed on the one end side in the width direction, the recess having a hole extending along the curved portion in the cylinder row direction and through which cooling water is introduced.

6. The cylinder head structure according to any one of claims 1 to 5, a cylinder head structure, wherein a cross section of the in-head EGR passage at a portion overlapping with the cooling water outlet portion has a flattened circular shape with a major axis extending in a cylinder row direction;

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