Internal combustion engine

Abstract

To suppress increase in a size while improving sealing performance by inhibiting oil from coming into contact with a three-face mating part.SOLUTION: In an internal combustion engine 1, a head cover 70 is connected to both of a cylinder body part 10 and a chain cover 60, and accommodates a part of a cam sprocket 22 and the other part of a chain 30. The head cover 70 includes a flange face 71 and a projecting part 72. The flange face 71 comes into contact with both of the cylinder body part 10 and the chain cover 60 to form a three-face mating part T. The projecting part 72 projects in the circumferential direction of the cam sprocket 22 on an inner face on an accommodation space side accommodating the cam sprocket 22 and the chain 30. The projecting part 72 is located on the accommodation space side relative to the flange face 71.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an internal combustion engine. [Background technology]

[0002] Documents disclosing the structure of an internal combustion engine include JP 2016-108992 A (Patent Document 1) and JP 2008-231957 A (Patent Document 2). Patent Documents 1 and 2 describe a structure for improving oil leakage from a three-surface mating portion formed on a cover that houses a chain in an internal combustion engine. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-108992 A [Patent Document 2] JP 2008-231957 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the past, in order to prevent oil from flowing down the inner surface of the head cover and coming into contact with the three-surface joint, it has been considered to add or mold a shield to the inner surface to guide the oil flow. However, if the separation distance between the head cover and the chain (sprocket) is increased to add such a shield, the internal combustion engine will become larger.

[0005] The present invention has been made in consideration of the above problems, and aims to provide an internal combustion engine that can improve sealing performance by suppressing contact of oil with the three-surface mating portion while suppressing an increase in size. [Means for solving the problem]

[0006] The internal combustion engine according to the present invention includes a cylinder body, a camshaft, a cam sprocket, a chain, a chain cover, and a head cover. The camshaft is provided in the cylinder body, and an axial end of the camshaft protrudes from a side surface of the cylinder body. The cam sprocket is provided at an axial end of the camshaft to rotate the camshaft. The chain is wound around the cam sprocket to rotate the cam sprocket. The chain cover is positioned to face the cylinder body in the axial direction of the camshaft, and accommodates a part of the cam sprocket and a part of the chain together with the cylinder body. The head cover is connected to both the cylinder body and the chain cover to accommodate another part of the cam sprocket and another part of the chain. The head cover has a flange surface and a protruding portion. The flange surface forms a three-surface mating portion by contacting both the cylinder body and the chain cover. The protruding portion protrudes along the circumferential direction of the cam sprocket on an inner surface on the side of the accommodation space that accommodates the cam sprocket and the chain. The protruding portion is positioned on the accommodation space side with respect to the flange surface. Effect of the Invention

[0007] According to the present invention, the oil that flows down the inner surface of the head cover under its own weight is guided by the protruding portion so that it climbs over the flange surface and falls onto the inner surface of the cylinder body or the chain cover. This reduces the oil from coming into contact with the three-surface mating portion. Furthermore, because the protruding portion protrudes along the circumferential direction of the cam sprocket, it is possible to prevent the separation distance between the head cover and the sprocket from becoming too long, and therefore the internal combustion engine can be prevented from becoming too large. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic diagram showing a configuration of an internal combustion engine according to a first embodiment. [Diagram 2] 2 is a schematic cross-sectional view of the internal combustion engine of FIG. 1, as viewed in the direction of the arrows along line II-II. [Diagram 3]3 is a perspective cross-sectional view of the internal combustion engine of FIG. 2, as viewed in the direction of the arrows along line III-III. [Figure 4] 3 is an enlarged partial cross-sectional view of region IV in FIG. 2. [Diagram 5] FIG. 6 is a partial cross-sectional view showing an internal combustion engine according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an internal combustion engine according to each embodiment of the present invention will be described with reference to the drawings. In the following description of the embodiments, the same or corresponding parts in the drawings are given the same reference characters, and the description thereof will not be repeated.

[0010] (Embodiment 1) FIG. 1 is a schematic diagram showing a configuration of an internal combustion engine according to a first embodiment. FIG. 2 is a schematic cross-sectional view of the internal combustion engine of FIG. 1 as viewed from the direction of the arrows II-II. As shown in FIGS. 1 and 2, an internal combustion engine 1 according to this embodiment is specifically a V-type engine. The internal combustion engine 1 includes an engine body 2 that is substantially V-shaped when viewed from one direction. The engine body 2 includes a first bank 3 that protrudes obliquely toward the upper U on the left side as viewed from one direction, and a second bank 4 that protrudes obliquely toward the upper U on the right side as viewed from one direction.

[0011] Fig. 3 is a perspective cross-sectional view of the internal combustion engine of Fig. 2, seen from the direction of the arrows III-III. As shown in Figs. 1 to 3, the internal combustion engine 1 according to the first embodiment of the present invention includes a cylinder body 10, a camshaft 20, a cam sprocket 22, a chain 30, a chain cover 60, a head cover 70, and a rib 80.

[0012] 2, the cylinder body 10 constitutes a part of the first bank 3 of the engine body 2 in the internal combustion engine 1. The cylinder body 10 also has a first body flange surface 11 facing sideways (axial direction A described below) and a second body flange surface 12 facing obliquely upwards (towards the head cover 70).

[0013] As shown in Figures 1 and 2, the cylinder body 10 includes a cylinder block 15, a cylinder head 16, and a chain case 17. The cylinder head 16 is located on the head cover 70 side as viewed from the cylinder block 15, and journals the camshaft 20. The cylinder head 16 is connected to an upper U of the cylinder block 15. The chain case 17 is located on the chain cover 60 side as viewed from the cylinder block 15 and the cylinder head 16. That is, in this embodiment, in the cylinder body 10, the chain case 17 has a first body flange surface 11 and a second body flange surface 12.

[0014] The cylinder body 10 does not necessarily have to have the chain case 17. When the cylinder body 10 does not have the chain case 17, the cylinder head is configured to have the first body flange surface 11 and the second body flange surface 12.

[0015] 1 and 2, the camshaft 20 is provided in the cylinder body 10, and an axial end 21 protrudes from a side surface of the cylinder body 10. When viewed from the axial direction A, the camshaft 20 is located on one side in the horizontal direction with the horizontal center C of the internal combustion engine 1 as a boundary. The cam sprocket 22 is provided at the axial end 21 of the camshaft 20, and rotates the camshaft 20.

[0016] The internal combustion engine 1 further includes a second camshaft 23 and a second cam sprocket 24. The second camshaft 23 is provided in the cylinder body 10, and its axial end 21 protrudes from the side surface of the cylinder body 10. When viewed from the axial direction A, the second camshaft 23 is located on the same side as the (first) camshaft 20 in the horizontal direction, with the center C as the boundary. The second camshaft 23 is located on the center C side as viewed from the (first) camshaft 20, and is located above the (first) camshaft 20 at a position U. In addition, the (first) camshaft 20 is an intake camshaft and the second camshaft 23 is an exhaust camshaft, but these may be reversed.

[0017] The second cam sprocket 24 is provided at an axial end of the second camshaft 23 to rotate the second camshaft 23.

[0018] The chain 30 is wound around the (first) cam sprocket 22 to rotate the cam sprocket 22. The chain 30 is further wound around the second cam sprocket 24 to rotate the second cam sprocket 24.

[0019] The internal combustion engine 1 further includes an operating shaft 40, a first operating sprocket 41, a second operating sprocket 42, a second chain 43, a crank sprocket 44, and a crankshaft 45. The operating shaft 40 is journalled by the engine body 2, and is located on the center C side as viewed from the camshaft 20.

[0020] The first operating sprocket 41 is provided at an axial end of the operating shaft 40, and is rotated by the operating shaft 40 in a clockwise direction as viewed from the chain cover 60 side. The chain 30 is wound around the first operating sprocket 41. The first operating sprocket 41 drives the chain 30 by rotating clockwise as viewed from the chain cover 60 side. As a result, the portion of the chain 30 opposite the center C as viewed from the camshaft 20 is driven from the downward direction D toward the upward direction U. The second operating sprocket 42 is provided at an axial end of the operating shaft 40, and rotates clockwise as viewed from the chain cover 60 side to rotate the operating shaft 40.

[0021] The second chain 43 is a separate chain that is not connected to the (first) chain 30. The second chain 43 is wound around the second actuating sprocket 42. When the second chain 43 is driven, the second chain 43 rotates the second actuating sprocket 42.

[0022] The second chain 43 is wound around the crank sprocket 44. The crank sprocket 44 drives the second chain 43 by rotating clockwise when viewed from the chain cover 60 side. The crankshaft 45 is journaled on the engine body 2. The crankshaft 45 is located on the center C side when viewed from the camshaft 20, and is located D below the camshaft 20. The crank sprocket 44 is provided on the axial end of the crankshaft 45. The crank sprocket 44 rotates as the crankshaft 45 rotates. In this way, the chain 30 is indirectly driven by the rotational force of the crankshaft 45. The chain 30 may be directly wound around the crank sprocket 44.

[0023] The internal combustion engine 1 further includes a tensioner 50. When viewed from the axial direction A, the tensioner 50 is located closer to the center C than the camshaft 20, and more specifically, is located between the camshaft 20 and the operating shaft 40 in the horizontal direction. The tensioner 50 is located below D of the chain 30, and applies a predetermined tension from the below D toward the above U. As a result, the chain 30 has a portion that extends obliquely upward from the lower end of the cam sprocket 22 toward the center C.

[0024] The internal combustion engine 1 further includes an oil supply unit 55. The oil supply unit 55 is provided on the side of the cylinder main body 10, and supplies oil so that the oil falls onto the chain 30. The position of the oil supply unit 55 is not particularly limited, and may be any position that allows the oil to fall onto any of the chains included in the internal combustion engine 1.

[0025] As shown in FIG. 3, the chain cover 60 is positioned so as to face the cylinder body 10 in the axial direction A of the camshaft 20, and accommodates a part of the cam sprocket 22 and a part of the chain 30 together with the cylinder body 10. In the cylinder body 10 according to this embodiment, the chain case 17 constitutes the inner surface on the accommodation space side, but if the cylinder body 10 does not have the chain case 17, the cylinder head and the cylinder block constitute the inner surface on the accommodation space side. The chain cover 60 has a first cover flange surface 61 facing in the axial direction A (toward the cylinder body 10) and a second cover flange surface 62 facing obliquely upward (toward the head cover 70). The first cover flange surface 61 abuts against the first body flange surface 11, so that the chain cover 60 is connected to the cylinder body 10.

[0026] The head cover 70 is connected to both the cylinder body 10 and the chain cover 60, and houses another part of the cam sprocket 22 and another part of the chain 30. The head cover 70 has a flange surface 71.

[0027] FIG. 4 is a partial cross-sectional view showing an enlarged region IV in FIG. 2. As shown in FIG. 3 and FIG. 4, the flange surface 71 is inclined obliquely with respect to the horizontal direction when viewed from the axial direction A. The flange surface 71 contacts both the cylinder body 10 and the chain cover 60 to form a three-surface mating portion T. Specifically, the first body flange surface 11 of the cylinder body 10 and the first cover flange surface 61 of the chain cover 60 contact each other, the second body flange surface 12 of the cylinder body 10 and the flange surface 71 of the head cover 70 contact each other, and the second cover flange surface 62 of the chain cover 60 and the flange surface of the head cover 70 contact each other, thereby forming the three-surface mating portion T. When viewed from the three-surface mating portion T, the chain 30 is driven from the lower side D toward the upper side U.

[0028] The head cover 70 further has a gasket 71A (not shown in FIG. 3). The gasket 71A is arranged so as to contact a flange surface 71 of the head cover 70. The gasket 71A is arranged so that at least a part of the flange surface 71 is located on the side opposite to the housing space that houses the cam sprocket 22 and the chain 30 as viewed from the gasket 71A. A sealing material such as a formed in place gasket (FIPG) may be further provided on the housing space side that houses the cam sprocket 22 and the chain 30 as viewed from the gasket 71A.

[0029] The head cover 70 further has a protruding portion 72. The protruding portion 72 protrudes along the circumferential direction of the cam sprocket 22 on the inner surface of the head cover 70 on the housing space side. Specifically, the protruding portion 72 protrudes diagonally downward when viewed from the axial direction A, and more specifically, protrudes toward the center C in the horizontal direction and protrudes downward D in the up-down direction. The protruding portion 72 is located on the housing space side with respect to the flange surface 71. When viewed from the axial direction A, the protruding portion 72 is located below the chain 30. Moreover, when viewed from the cam sprocket 22, the protruding portion 72 extends along the flange surface 71.

[0030] The head cover 70 further has a protruding portion 75 that is located above the protruding portion 72 in a direction U and protrudes toward the housing space in order to protrude the protruding portion 72. When viewed from the axial direction A of the camshaft 20, the protruding portion 75 has a third surface portion 76 that extends along the circumferential direction of the cam sprocket 22, and a fourth surface portion 77 that is connected to the third surface portion 76 and is inclined upward in the direction U as it moves away from the cam sprocket 22.

[0031] Although the protrusion 72 and the overhanging portion 75 are molded integrally with the head cover 70, they may be provided by attaching a bracket or the like separate from the head cover 70 to the head cover 70.

[0032] The rib 80 protrudes from at least one of the cylinder body 10 and the chain cover 60 toward the cam sprocket 22 when viewed from the axial direction A of the camshaft 20 on the housing space side. Specifically, the rib 80 is provided on both the cylinder body 10 (chain case 17) and the chain cover 60. The rib 80 has a first rib 80A and a second rib 80B. The first rib 80A protrudes from the cylinder body 10, and the second rib 80B protrudes from the chain cover 60. The first rib 80A and the second rib 80B are positioned adjacent to each other in a direction along the flange surface 71. That is, the rib 80 extends along the flange surface 71.

[0033] The rib 80 has a first surface 81 located on the front side in the drive direction of the chain 30 as viewed from the camshaft 20, and a second surface 82 connected to the first surface 81 and located on the rear side in the drive direction of the chain 30. The first surface 81 is located below the protruding portion 72 and is inclined downward D toward a connecting portion 83 with the second surface 82 as viewed from the axial direction A of the camshaft 20. The second surface 82 faces toward a portion 31 of the chain 30 located at the lower end of the cam sprocket 22. The protruding portion 72 protrudes toward the connecting portion 83 between the first surface 81 and the second surface 82.

[0034] Although the ribs 80 are molded integrally with the cylinder body 10 and the chain cover 60, the ribs 80 may also be provided by attaching a bracket or the like separate from the cylinder body 10 and the chain cover 60 to the cylinder body 10 and the chain cover 60.

[0035] As described above, in the internal combustion engine 1 according to this embodiment, the head cover 70 has a flange surface 71 and a protruding portion 72. The flange surface 71 contacts both the cylinder body 10 and the chain cover 60 to form a three-surface mating portion T. The protruding portion 72 protrudes in the circumferential direction of the cam sprocket 22 from the inner surface on the side of the storage space that houses the cam sprocket 22 and the chain 30. The protruding portion 72 is located on the storage space side with respect to the flange surface 71.

[0036] As a result, when the chain 30 wound around the cam sprocket 22 drives upward, oil splashes from the chain 30 to the head cover 70 and flows down the inner surface of the head cover 70 under its own weight, and reaches the protruding portion 72. Then, as shown by path R1 in FIG. 4, the oil is guided by the protruding portion 72 to climb over the flange surface 71 and fall onto the inner surface of the cylinder main body 10 or the chain cover 60. This reduces the oil from coming into contact with the three-surface mating portion T. Furthermore, because the protruding portion 72 protrudes along the circumferential direction of the cam sprocket 22, the separation distance between the head cover 70 and the cam sprocket 22 can be prevented from becoming long, and the internal combustion engine 1 can be prevented from becoming large.

[0037] The cylinder body 10 also includes a cylinder block 15, a cylinder head 16, and a chain case 17. The cylinder head 16 is located on the head cover 70 side as viewed from the cylinder block 15, and supports the camshaft 20. The chain case 17 is located on the chain cover side as viewed from the cylinder block 15 and the cylinder head 16, and forms the inner surface of the cylinder body 10 on the housing space side.

[0038] By configuring the cylinder body 10 to include the chain case 17 in this manner, the position of the three-surface mating portion can be adjusted, and the three-surface mating portion can be formed in a position that is advantageous for preventing oil leakage.

[0039] In addition, the internal combustion engine 1 further includes a rib 80 that protrudes from at least one of the cylinder body 10 and the chain cover 60 toward the cam sprocket 22 when viewed from the axial direction A of the camshaft 20 on the storage space side and extends along the flange surface 71.

[0040] As a result, oil that has splashed onto the cylinder body 10 or the chain cover 60 from the portion of the chain 30 that is driven toward the cam sprocket 22 flows along the inner surface of the cylinder body 10 or the chain cover 60 due to the force of the splash, and reaches the rib 80. Then, as shown by path R2 in Figure 4, the oil is blocked by the rib 80 and bounced away from the flange surface 71. This makes it possible to reduce the oil coming into contact with the three-surface mating portion T.

[0041] Moreover, the chain 30 drives from below to above when viewed from the three-surface mating portion T. When viewed from the camshaft 20, the rib 80 has a first surface portion 81 located on the front side in the driving direction of the chain 30, and a second surface portion 82 connected to the first surface portion 81 and located on the rear side in the driving direction of the chain 30. The first surface portion 81 is located below the protruding portion 72, and is inclined downward toward the connection portion with the second surface portion 82 when viewed from the axial direction A of the camshaft 20.

[0042] As a result, even when the rib 80 is provided, the oil that has dropped from the protrusion 72 onto the first surface 81 is guided further downward, as shown by the path R3 in Fig. 4. This prevents the oil on the first surface 81 from coming into contact with the flange surface 71 and the three-surface mating portion T.

[0043] In addition, the second surface portion 82 faces toward a portion 31 of the chain 30 that is located at the lower end of the cam sprocket 22 .

[0044] This allows the oil that splashes directly from the portion 31 of the chain 30 toward the flange surface 71 to be effectively blocked by the second surface portion 82 and guided downward. As a result, the oil can be prevented from coming into contact with the three-surface mating portion T.

[0045] Moreover, the protruding portion 72 protrudes toward a connection portion 83 between the first surface portion 81 and the second surface portion 82.

[0046] This makes it easier for the oil flowing on the cam sprocket 22 side of the protrusion 72 to climb over the rib 80 when it spurts out of the protrusion 72 in the direction of its flow, as shown by route R4 in Fig. 4. This makes it possible to prevent the oil from accumulating on the first surface 81. This in turn makes it possible to prevent the oil from coming into contact with the three-surface mating portion T.

[0047] Further, head cover 70 has a protruding portion 75 that is located above protruding portion 72 and protrudes toward the housing space in order to protrude protruding portion 72. Protruding portion 75 has a third surface portion 76 that extends along the circumferential direction of cam sprocket 22 when viewed from axial direction A of camshaft 20, and a fourth surface portion 77 that is connected to third surface portion 76 and inclines upward in the direction away from cam sprocket 22.

[0048] This allows the oil adhering to the fourth surface portion 77 to be guided to the third surface portion 76, and the oil on the third surface portion 76 to be guided further downward. As a result, oil can be prevented from accumulating on the inner surface of the head cover 70 above the protruding portion 72.

[0049] Moreover, when viewed from the axial direction A of the camshaft 20 , the protrusion 72 is located below the chain 30 .

[0050] As a result, oil that directly drops from the chain 30 can be received and guided downward by the protrusion 72. As a result, the oil can be prevented from contacting the flange surface 71 and the three-surface mating portion T.

[0051] (Embodiment 2) Hereinafter, an internal combustion engine according to embodiment 2 of the present invention will be described. The internal combustion engine according to embodiment 2 of the present invention differs from embodiment 1 mainly in the shape of the protruding portion. Therefore, the description of the configuration that is similar to that of internal combustion engine 1 according to embodiment 1 of the present invention will not be repeated.

[0052] Fig. 5 is a partial cross-sectional view showing an internal combustion engine according to embodiment 2. As shown in Fig. 5, in an internal combustion engine 1a according to embodiment 2 of the present invention, a protruding portion 72a protrudes so as to cover a three-surface mating portion T when viewed from a portion 31 of the chain 30 located at the lower end of the cam sprocket 22.

[0053] This not only prevents oil that runs down the inner surface of the head cover 70 from coming into contact with the three-surface mating portion T, but also allows the protruding portion 72a to receive oil that splashes when the driving direction of the chain 30 faces upward U from the portion 31 and guide it downward D. As a result, oil can be prevented from reaching the flange surface 71 that forms the three-surface mating portion T.

[0054] Furthermore, the protrusion 72a extends along the inner surface of at least one of the cylinder body 10 and the chain cover 60 on the housing space side.

[0055] This makes it easier to guide the oil running down the inner surface of the head cover 70 to the inner surfaces of at least one of the cylinder main body 10 and the chain cover 60, thereby further preventing oil from coming into contact with the three-surface joint portion T.

[0056] In addition, the internal combustion engine 1a of embodiment 2 does not have a rib because the protrusion 72a can sufficiently suppress contact of oil with the three-surface mating portion T, but the internal combustion engine 1a may be provided with a rib 80 similar to that of embodiment 1.

[0057] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0058] 1,1a internal combustion engine, 2 engine body, 3 first bank, 4 second bank, 10 cylinder body portion, 11 first body flange surface, 12 second body flange surface, 15 cylinder block, 16 cylinder head, 17 chain case, 20 camshaft, 21 axial end, 22 cam sprocket, 23 second camshaft, 24 second cam sprocket, 30 chain, 31 portion, 40 operating shaft, 41 first operating sprocket, 42 second operating sprocket, 43 second chain, 44 crank sprocket, 45 crankshaft, 50 tensioner, 55 oil supply portion, 60 chain cover, 61 first cover flange surface, 62 second cover flange surface, 70 head cover, 71 flange surface, 71A gasket, 72,72a protrusion, 75 overhang, 76 third surface portion, 77 fourth surface portion, 80 Rib, 80A first rib, 80B second rib, 81 first surface portion, 82 second surface portion, 83 connecting portion.

Claims

1. A cylinder main body, a camshaft provided in the cylinder body, the axial end of the camshaft protruding from a side surface of the cylinder body; a cam sprocket provided at an axial end of the camshaft to rotate the camshaft; a chain that is wound around the cam sprocket and rotates the cam sprocket; a chain cover that is positioned to face the cylinder body in the axial direction of the camshaft and that accommodates the cylinder body, a part of the cam sprocket, and a part of the chain; a head cover connected to both the cylinder body and the chain cover to accommodate another part of the cam sprocket and another part of the chain, The head cover is a flange surface that forms a three-surface mating portion by contacting both the cylinder body portion and the chain cover; a protrusion protruding in a circumferential direction of the cam sprocket on an inner surface on the side of an accommodation space that accommodates the cam sprocket and the chain, The protruding portion is located on the housing space side with respect to the flange surface, The protruding portion protrudes so as to cover the three-surface mating portion, the internal combustion engine further comprising a rib that protrudes from at least one of the cylinder body and the chain cover toward the cam sprocket when viewed in the axial direction of the camshaft on the accommodation space side and extends along the flange surface.

2. A cylinder body, a camshaft provided in the cylinder body, the axial end of the camshaft protruding from a side surface of the cylinder body; a cam sprocket provided at an axial end of the camshaft to rotate the camshaft; a chain that is wound around the cam sprocket and rotates the cam sprocket; a chain cover that is positioned to face the cylinder body in the axial direction of the camshaft and that accommodates the cylinder body, a part of the cam sprocket, and a part of the chain; a head cover connected to both the cylinder body and the chain cover to accommodate another part of the cam sprocket and another part of the chain, The head cover is a flange surface that forms a three-surface mating portion by contacting both the cylinder body portion and the chain cover; a protrusion protruding in a circumferential direction of the cam sprocket on an inner surface on the side of an accommodation space that accommodates the cam sprocket and the chain, The protruding portion is located on the housing space side with respect to the flange surface, The protruding portion protrudes so as to cover the three-surface mating portion, the head cover has a protruding portion located above the protruding portion and protruding toward the accommodation space to allow the protruding portion to protrude, an internal combustion engine, wherein the protrusion portion has a third surface portion extending circumferentially around the cam sprocket when viewed in the axial direction of the camshaft, and a fourth surface portion connected to the third surface portion and inclined upward in a direction away from the cam sprocket.

3. 3. The internal combustion engine according to claim 2, further comprising a rib that protrudes from at least one of the cylinder body and the chain cover toward the cam sprocket when viewed in the axial direction of the camshaft on the accommodation space side and extends along the flange surface.

4. The chain is driven from below to above when viewed from the three-surface mating portion, the rib has a first surface portion located on a front side in a drive direction of the chain when viewed from the camshaft, and a second surface portion connected to the first surface portion and located on a rear side in the drive direction of the chain, 4. The internal combustion engine according to claim 1, wherein the first surface portion is located below the protrusion and is inclined downwardly toward a connection portion with the second surface portion when viewed in the axial direction of the camshaft.

5. 5. The internal combustion engine according to claim 4, wherein the second surface portion faces toward a portion of the chain that is located at a lower end of the cam sprocket.

6. 6. The internal combustion engine according to claim 4, wherein the protruding portion protrudes toward the connection portion between the first surface portion and the second surface portion.

7. The cylinder body portion is A cylinder block; a cylinder head located on the head cover side as viewed from the cylinder block and supporting the camshaft; 7. The internal combustion engine according to claim 1, further comprising: a chain case that is located on the chain cover side as viewed from the cylinder block and the cylinder head and that forms an inner surface of the cylinder body on the side of the accommodation space.

8. 8. The internal combustion engine according to claim 1, wherein the protrusion is located below the chain when viewed in the axial direction of the camshaft.

9. 9. The internal combustion engine according to claim 1, wherein the protruding portion protrudes so as to cover the three-surface mating portion when viewed from a portion of the chain that is located at a lower end of the cam sprocket.

10. The internal combustion engine according to claim 9 , wherein the protrusion extends along an inner surface of at least one of the cylinder body and the chain cover that faces the accommodation space.

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