Internal combustion engine

Abstract

To provide an internal combustion engine which can sufficiently secure the stiffness of a structure for holding a camshaft to a cylinder head.SOLUTION: An internal combustion engine 10 comprises a lower cam cap 14, an upper cam cap 16, a fastening member and a reinforcing part 32. The lower cam cap 14 has lower half-holes 14a, 14b. The upper cam cap 16 has upper half-holes 16a, 16b. The fastening member penetrates the upper cam cap 16 and the lower cam cap 14 in a position avoiding cam holes in a state that the cam holes (bearing parts C1, C2) are formed by a combination of the upper half holes 16a, 16b and the lower half holes 14a, 14b, and fastens the upper cam cap 16 and the lower cam cap 14 to a cylinder head 12. The reinforcing part 32 connects at least one outer wall 30 of the cylinder head 12 in a short direction from a substantially-central region of the cylinder head 12 in the short direction (X-direction) in a position corresponding to an attachment position of the lower cam cap 14.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Conventionally, a cylinder head mounted on a cylinder block of an internal combustion engine is provided with a camshaft equipped with a cam that drives the intake valve and exhaust valve to open and close at a predetermined timing. The camshaft is disposed in a bearing portion formed by, for example, a camshaft housing attached to the upper side of the cylinder head and a cam cap attached to the upper side of the camshaft housing (Patent Document 1). Also proposed is an internal combustion engine that includes a lower cam holder formed for each cylinder, and an intake upper cam holder and an exhaust upper cam holder fixed to the upper side of the lower cam holder (Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-57427 A [Patent Document 2] JP 2000-170506 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the case of the internal combustion engine of Patent Document 1, the camshaft housing and the cam cap are fastened together with a fastening member, and then fixed to the cylinder head with another fastening member. Similarly, in the case of the internal combustion engine of Patent Document 2, the intake upper cam holder and the exhaust upper cam holder are fixed to the lower cam holder with a fastening member, and then fixed to the cylinder head with another fastening member. In other words, each part is fastened with its own fastening member. Therefore, even though each part is fastened with multiple fastening members, there is a problem that the structural rigidity is not sufficient to hold the camshaft to the cylinder head.

[0005] SUMMARY OF THE PRESENT INVETION In view of the above, an object of the present invention is to provide an internal combustion engine that can obtain sufficient rigidity of a structure for holding a camshaft to a cylinder head. [Means for solving the problem]

[0006] In order to achieve the above object, an internal combustion engine according to an embodiment of the present invention comprises: a lower cam cap that can be attached to an upper surface of a cylinder head and has two lower half holes that can support a camshaft from below; an upper cam cap that faces the lower half holes and has two upper half holes that can support the camshaft from above; a plurality of fastening portions that penetrate the lower cam cap and the upper cam cap and fasten the upper cam cap to the lower cam cap; a plurality of fastening members that penetrate the upper cam cap and the lower cam cap and fasten the upper cam cap to the cylinder head at positions that avoid two cam holes formed by the combinations of the upper half holes and the lower half holes; a reinforcing portion that is provided on the upper surface of the cylinder head at a position corresponding to the attachment position of the lower cam cap and is formed integrally with one of the outer walls of the cylinder head in the short side direction of the cylinder head; and a non-formed portion where the reinforcing portion is not formed, that is formed between the other outer wall of the cylinder head and the reinforcing portion in the short side direction of the cylinder head,The non-forming portion is provided with an oil flow path, At least one of the plurality of fastening portions is provided at a position corresponding to the non-formed portion, and at least one of the plurality of fastening members does not reach the non-formed portion.

[0007] According to this configuration, for example, a reinforcing portion is formed integrally with one of the outer walls of the cylinder head in the short side direction of the cylinder head. Therefore, the upper cam cap and the lower cam cap can be integrally fastened to the cylinder head with fastening members. As a result, the rigidity of the structure for holding the camshaft against the cylinder head can be easily improved. Also, since the rigidity can be improved by efficiently using fastening members for the reinforcing portion, the rigidity of the structure for holding the camshaft against the cylinder head can be easily improved without increasing the number of fastening members. Furthermore, a non-formed portion where no reinforcing portion is formed is formed between the other outer wall of the cylinder head and the reinforcing portion. Then, an oil flow path is provided there. This makes it possible to effectively utilize the internal space of the cylinder head, thereby achieving both improved rigidity of the structure for holding the camshaft to the cylinder head and effective utilization of the internal space of the cylinder head.

[0009] In addition, the internal combustion engine according to the embodiment of the present invention may further include, for example, a straight pin that aligns the lower cam cap and the reinforcing portion of the cylinder head when they are combined, and the straight pin may be positioned below the lower half hole. According to this configuration, for example, the positioning of the lower cam cap and the reinforcing portion of the cylinder head can be easily and accurately performed. Effect of the Invention

[0012] According to the present invention, an internal combustion engine is provided that is capable of obtaining sufficient rigidity of a structure for holding a camshaft relative to a cylinder head. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is an exemplary schematic perspective view showing a fastening structure for an internal combustion engine according to an embodiment. [Diagram 2] FIG. 2 is an exemplary schematic cross-sectional view showing a fastening structure for an internal combustion engine according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, exemplary embodiments of the present invention will be disclosed. The configurations of the embodiments shown below, as well as the actions, results, and effects brought about by the configurations, are merely examples. The present invention can be realized by configurations other than those disclosed in the following embodiments, and it is possible to obtain at least one of various effects based on the basic configurations and derivative effects.

[0015] Fig. 1 is an exemplary schematic perspective view showing a fastening structure of an internal combustion engine 10 according to an embodiment of the present invention, and Fig. 2 is an exemplary schematic cross-sectional view showing the fastening structure of the internal combustion engine 10.

[0016] For convenience, an X-axis, a Y-axis, and a Z-axis are defined in this specification. The X-axis, the Y-axis, and the Z-axis are perpendicular to each other. The X-axis is provided along the short side direction of the internal combustion engine 10. The Y-axis is provided along the long side direction of the internal combustion engine 10. The Z-axis is provided along the height of the internal combustion engine 10. Furthermore, an X-direction, a Y-direction, and a Z-direction are defined in this specification. The X-direction is the direction along the X-axis, the Y-direction is the direction along the Y-axis, and the Z-direction is the direction along the Z-axis.

[0017] The internal combustion engine 10 of this embodiment includes a cylinder head 12, a lower cam cap 14, an upper cam cap 16, and fastening members (bolts 36, 38, 40, 42, described below) that fasten these components together.

[0018] The cylinder head 12 is attached to the upper side of a cylinder block (not shown) in the internal combustion engine 10. For convenience of illustration, in Fig. 1, the cylinder head 12 is formed by the lower cam cap 14 and the upper cam cap 16, and only the portion present below the cam holes that rotatably support the camshaft 18 and the camshaft 20 (i.e., below the lower cam cap 14) of the bearings C1 and C2 (see Fig. 2) of the cylinder head 12 is shown, and other portions are omitted from the illustration. The cylinder head 12 corresponds to the shape of the upper surface of the cylinder block, which is, for example, substantially rectangular, extends in the directions of the arrows X and Y, and is formed to a size capable of accommodating a plurality of cylinders therein.

[0019] The cylinder head 12 is fastened to the cylinder block by a plurality of fastening members (e.g., bolts) not shown. The cylinder head 12 can be formed, for example, by low pressure casting using an aluminum alloy or the like. Engine valves such as intake valves and exhaust valves, and various parts of a valve train (not shown) are attached to the cylinder head 12.

[0020] A lower cam cap 14 having lower half holes 14a, 14b capable of supporting a rod-shaped camshaft 18 and a camshaft 20 extending in the Y direction and rotatable about a rotation axis parallel to the Y axis from the lower surface thereof can be attached in a state of intimate contact with the upper surface 12M of the cylinder head 12. The lower cam cap 14 can be formed, for example, by casting an aluminum alloy or the like.

[0021] The lower cam cap 16 has upper half holes 16a, 16b that face the lower half holes 14a, 14b of the lower cam cap 14 and can support the camshaft 18 and the camshaft 20 from above. The upper cam cap 16 can also be formed by casting an aluminum alloy, for example.

[0022] 1 and 2, intake valves and exhaust valves are formed at positions corresponding to each cylinder, and camshaft 18 opens and closes, for example, the intake valves by means of cam portion 18a formed on its axis. Similarly, camshaft 20 opens and closes, for example, the exhaust valves by means of cam portion 20a formed on its axis.

[0023] 2, it is desirable that the bearing portions C1, C2 formed by the lower half holes 14a, 14b of the lower cam cap 14 and the upper half holes 16a, 16b of the upper cam cap 16 have a predetermined level of roundness or higher in order to smoothly rotate the camshafts 18, 20. Although the roundness of the arc portions of the lower half holes 14a, 14b of the lower cam cap 14 and the upper half holes 16a, 16b of the upper cam cap 16 can satisfy a predetermined value during machining, it becomes necessary to assemble the lower cam cap 14 and the upper cam cap 16 again to satisfy the roundness when combining them.

[0024] Therefore, the internal combustion engine 10 of this embodiment is provided with a pin ring 22 for ensuring positioning accuracy when the lower cam cap 14 and the upper cam cap 16 are assembled together. The pin ring 22 is, for example, a hollow ring made of metal, and the accuracy of the outer circumferential surface in particular is precisely machined so that a predetermined accuracy can be achieved when the lower cam cap 14 and the upper cam cap 16 are assembled together. A bolt 36 (bolt 42) serving as a fastening member for fastening the lower cam cap 14 and the upper cam cap 16 to the cylinder head 12 is inserted into the inner diameter side of the pin ring 22. The lower cam cap 14 is formed with a stepped portion having a diameter enlarged by the outer diameter of the pin ring 22 from the insertion hole for the bolt 36 (bolt 42) as an attachment portion 22a into which the pin ring 22 can be inserted at the insertion position of the bolt 36 (bolt 42). Similarly, the upper cam cap 16 is formed with a stepped portion, which is larger in diameter than the insertion hole for the bolt 36 (bolt 42) by the outer diameter of the pin ring 22, as the mounting portion 22b into which the pin ring 22 can be inserted at the insertion position of the bolt 36 (bolt 42). The inner diameter of the pin ring 22 is formed to be equal to the diameter of the insertion hole for the bolt 36 (bolt 42). The forming position and inner diameter surface accuracy of the mounting portion 22a in the lower cam cap 14 and the mounting portion 22b in the upper cam cap 16 are ensured at a predetermined level when the lower cam cap 14 and the upper cam cap 16 are machined, and the machining accuracy of the outer diameter surface of the pin ring 22 is ensured at a predetermined level. As a result, by combining the lower cam cap 14 and the upper cam cap 16 via the pin ring 22, the predetermined roundness of the bearing portion C1 and the bearing portion C2 can be easily ensured.

[0025] In addition, if there is sufficient space on the top surface 14M of the lower cam cap 14 and the bottom surface 16N of the upper cam cap 16, the mounting portion 22a and the mounting portion 22b may be formed at a position different from the insertion position of the bolt 36 (bolt 42), and the lower cam cap 14 and the upper cam cap 16 may be assembled by mounting the pin ring 22, and the assembly accuracy can be similarly ensured. In this case, the pin ring 22 may be a solid cylindrical pin, which may contribute to reducing manufacturing costs. Also, although an example in which the pin ring 22 is provided at two locations is shown in Figures 1 and 2, the number and locations of the pin rings 22 may be changed as appropriate.

[0026] 2, there are cases where the accuracy of the assembled position of the cylinder head 12 cannot be maintained at a predetermined value with respect to the bearing parts C1, C2 formed by combining the lower cam cap 14 and the upper cam cap 16. In such cases, the intake valve operated by the cam part 18a of the camshaft 18 and the exhaust valve operated by the cam part 20a of the camshaft 20 may not be able to operate accurately.

[0027] Therefore, in the case of the internal combustion engine 10 of this embodiment, a straight pin 24 is provided to ensure positioning accuracy when the lower cam cap 14, which is combined with the upper cam cap 16 via the pin ring 22, is combined with the cylinder head 12. The straight pin 24 is, for example, a metal cylindrical shape, and the accuracy of the outer circumferential surface in particular is precisely machined so that the accuracy when the lower cam cap 14 and the cylinder head 12 are combined can be realized with a predetermined accuracy. The cylinder head 12 is formed with a hole portion having an inner diameter corresponding to the outer diameter of the straight pin 24 as a mounting portion 24a into which the straight pin 24 can be inserted. Similarly, the lower cam cap 14 is formed with a hole portion having an inner diameter corresponding to the outer diameter of the straight pin 24 as a mounting portion 24b into which the straight pin 24 can be inserted. The accuracy of the inner diameter surfaces of the mounting portion 24a in the cylinder head 12 and the mounting portion 24b in the lower cam cap 14 is ensured to a predetermined level when machining the cylinder head 12 and the lower cam cap 14, and the machining accuracy of the outer diameter surface of the straight pin 24 is ensured to a predetermined level. As a result, by combining the cylinder head 12 and the lower cam cap 14 via the straight pin 24, the positioning accuracy of the intake valves and exhaust valves of the camshafts 18 and 20 journalled on the bearings C1 and C2 can be easily improved.

[0028] The straight pin 24 may be configured similarly to the pin ring 22, and the insertion position of the bolt 36 (bolt 42) may be used to determine the positioning of the cylinder head 12 and the lower cam cap 14 when they are assembled together.

[0029] As described above, the lower cam cap 14 and the upper cam cap 16 can be fastened to the cylinder head 12 by the bolts 36, 38, 40, and 42. In the example shown in Figures 1 and 2, the bolt 38 is used only to fasten the lower cam cap 14 and the upper cam cap 16, and the bolts 36, 40, and 42 are used to fasten the lower cam cap 14, the upper cam cap 16, and the cylinder head 12.

[0030] As shown in Figures 1 and 2, the bolts 36 and 42 are fastened using a fastening portion 36c (on the outer wall 30B side) having an internal thread formed in a position near the outer wall 30 in the short side direction (X direction) of the cylinder head 12, and a fastening portion 42c (on the outer wall 30A side) having an internal thread formed therein.

[0031] On the other hand, since the bolt 40 is fastened at a position away from the outer wall 30 of the cylinder head 12, the internal combustion engine 10 of this embodiment is provided with a reinforcing portion 32 that connects the outer peripheral portion 28 of the spark plug storage portion 26 to the outer wall 30A, which is at least one of the outer walls in the short direction of the cylinder head 12, at a position corresponding to the mounting position of the lower cam cap 14 on the upper surface 12M of the cylinder head 12 in order to fasten the bolt 40. The reinforcing portion 32 is formed integrally with the outer wall 30 of the cylinder head 12 when the cylinder head 12 is molded. By connecting the spark plug storage portion 26 (outer peripheral portion 28) and the outer wall 30A with the reinforcing portion 32, the rigidity of the cylinder head 12 itself can be improved. The reinforcing portion 32 is formed with a fastening portion 40c in which a female thread portion that screws with the male thread portion of the bolt 40 is formed.

[0032] The lower cam cap 14 is formed with through-holes 36b, 40b, 42b through which the bolts 36, 40, 42 are inserted corresponding to the positions of the fastening parts 36c, 40c, 42c and screwed into the female threads of the fastening parts 36c, 40c, 42c. As described above, the bolt 38 is used only for fastening the lower cam cap 14 and the upper cam cap 16. Therefore, the lower cam cap 14 is formed with a fastening part 38b having a female thread into which the male thread of the bolt 38 can be screwed. The fastening part 38b may penetrate the lower cam cap 14, but is preferably formed in a stopper hole shape to prevent dust, chips, etc. attached to the bolt 38 from falling to the cylinder head 12 side. It is also preferable that the fastening parts 36c, 40c, 42c formed on the cylinder head 12 are similarly formed in a stopper hole shape.

[0033] The upper cam cap 16 is formed with through-holes 36a, 38a, 40a, 42a through which the bolts 36, 38, 40, 42 are inserted, corresponding to the positions of the fastening portions 36c, 40c, 42c of the cylinder head 12 and the through-hole 40b of the lower cam cap 14. The lower cam cap 14 is formed with a through-hole 26a for accelerating the spark plug at a position corresponding to the spark plug storage portion 26. Similarly, the upper cam cap 16 is formed with a through-hole 26b at a position corresponding to the spark plug storage portion 26 and the through-hole 26a.

[0034] In this manner, at least one fastening member (e.g., bolt 40) that fastens the upper cam cap 16 and the lower cam cap 14 together to the cylinder head 12 is fastened to the reinforcing portion 32. That is, in the case of Figs. 1 and 2, for example, by forming the reinforcing portion 32 that connects the outer peripheral portion 28 of the spark plug housing portion 26 formed in the approximate central region in the short side direction of the cylinder head 12 to the outer wall 30A in the short side direction of the cylinder head 12, the upper cam cap 16 and the lower cam cap 14 can be integrally fastened to the cylinder head 12 by the fastening member. As a result, the rigidity of the structure for holding the camshafts 18, 20 to the cylinder head 12 can be easily improved. In addition, since the rigidity can be improved by efficiently using the fastening member for the reinforcing portion 32, the rigidity of the structure for holding the camshafts 18, 20 to the cylinder head 12 can be easily improved without increasing the number of fastening members.

[0035] 1 and 2, the bolt 38 only fastens the lower cam cap 14 and the upper cam cap 16 together, and does not reach the cylinder head 12. In other words, no reinforcing portion is formed on the outer wall 30B side of the spark plug housing 26, and a space (non-formed portion) is secured as a lightening portion. Therefore, in the non-formed portion where the reinforcing portion 32 of the cylinder head 12 is not formed, an oil flow path 34 or the like can be formed as a part that is not involved in fastening parts. The oil flow path 34 is, for example, a flow path branched from a main flow path (main gallery) for supplying lubricating liquid (e.g., oil) that lubricates the driving parts of the internal combustion engine 10 to each position of the internal combustion engine 10, and supplies oil to a lash adjuster, for example.

[0036] In this manner, in the case of the present embodiment 10, by adjusting the position of the reinforcing portion 32, it is possible to selectively arrange fastening members that reach the cylinder head 12 and fastening members that do not reach the cylinder head 12. As a result, it is possible to easily achieve both improved rigidity of the structure for holding the camshafts 18, 20 to the cylinder head 12 and effective utilization of the internal space of the cylinder head 12.

[0037] In the case of the internal combustion engine 10 shown in Figs. 1 and 2, an example is shown in which the reinforcing portion 32 is formed to connect the outer peripheral portion 28 of the spark plug housing portion 26 formed in the approximate central region in the short-side direction of the cylinder head 12 to the short-side outer wall 30A of the cylinder head 12. In another embodiment, the reinforcing portion 32 may be formed on the upper surface 12M of the cylinder head 12 at a position corresponding to the mounting position of the lower cam cap 14 so as to connect both the short-side outer walls 30A, 30B of the cylinder head 12. In this case, the bolt 38 in Fig. 1 is used as a fastening member for fastening the upper cam cap 16 and the lower cam cap 14 together to the cylinder head 12, similar to the bolt 40. In this case, although it becomes necessary to change the position of the oil flow passage 34, it becomes possible to further improve the rigidity of the structure for holding the camshafts 18, 20 relative to the cylinder head 12, which can contribute to improving the performance of the internal combustion engine 10.

[0038] In the internal combustion engine 10 of the present embodiment, the lower cam cap 14 for holding the camshafts 18, 20 is separated from the cylinder head 12. As a result, when the cylinder head 12 is subjected to low pressure casting, it is possible to reduce the height (size) of the cylinder head 12 in the Z direction. In addition, it is possible to contribute to simplifying the shape of the cylinder head 12, and it is possible to reduce the size of the core used when casting the cylinder head 12. As a result, it is possible to contribute to reducing the manufacturing cost of the cylinder head 12. In addition, as the height direction of the cylinder head 12 is reduced, it is possible to improve the molten metal circulation during casting, which can contribute to improving the casting quality. In this way, by adopting a fastening structure using the reinforcing portion 32, it is possible to simultaneously realize an improvement in the rigidity of the internal combustion engine 10, a reduction in the manufacturing cost of the internal combustion engine 10, and an improvement in quality.

[0039] (Effects of this embodiment) As described above, the internal combustion engine 10 according to this embodiment includes the lower cam cap 14, the upper cam cap 16, the fastening members (bolts 36, etc.), and the reinforcing portion 32. The lower cam cap 14 can be attached to the upper surface 12M of the cylinder head 12, and has lower half holes 14a, 14b capable of supporting the camshafts 18, 20 from the lower surface. The upper cam cap 16 has upper half holes 16a, 16b facing the lower half holes 14a, 14b and capable of supporting the camshafts 18, 20 from the upper surface. The fastening members penetrate the upper cam cap 16 and the lower cam cap 14 at positions avoiding the cam holes (bearings C1, C2) in a state in which the cam holes (bearings C1, C2) are formed by combining the upper half holes 16a, 16b and the lower half holes 14a, 14b, and fasten the upper cam cap 16 and the lower cam cap 14 to the cylinder head 12. The reinforcing portion 32 connects at least one of the outer walls 30 in the short side direction (X direction) of the cylinder head 12 from a substantially central region in the short side direction (X direction) of the cylinder head 12 at a position on the upper surface 12M of the cylinder head 12 corresponding to the mounting position of the lower cam cap 14. At least one of the fastening members is fastened to the reinforcing portion 32. This makes it possible to easily improve the rigidity of the structure for holding the camshafts 18, 20 to the cylinder head 12. In addition, since the rigidity can be improved by efficiently using the fastening members for the reinforcing portion 32, it is possible to easily improve the rigidity of the structure for holding the camshafts 18, 20 to the cylinder head 12 without increasing the number of fastening members.

[0040] Furthermore, in the internal combustion engine 10 according to the embodiment of the present invention, for example, the oil flow passage 34 may be formed in a non-formed portion of the reinforcing portion 32 of the cylinder head 12. This makes it possible to achieve both improved rigidity of the structure for holding the camshafts 18, 20 to the cylinder head 12 and effective use of the internal space of the cylinder head 12.

[0041] Moreover, the internal combustion engine 10 according to the embodiment of the present invention includes the lower cam cap 14, the upper cam cap 16, fastening members (bolts 36, etc.), and the reinforcing portion 32. The lower cam cap 14 can be attached to the upper surface 12M of the cylinder head 12, and has lower half holes 14a, 14b capable of supporting the camshafts 18, 20 from the lower surface. The upper cam cap 16 has upper half holes 16a, 16b facing the lower half holes 14a, 14b and capable of supporting the camshafts 18, 20 from the upper surface. The fastening members penetrate the upper cam cap 16 and the lower cam cap 14 at positions avoiding the cam holes (bearings C1, C2) in a state in which the cam holes (bearings C1, C2) are formed by a combination of the upper half holes 16a, 16b and the lower half holes 14a, 14b, and fasten the upper cam cap 16 and the lower cam cap 14 to the cylinder head 12. The reinforcing portion 32 connects both outer walls 30A, 30B in the short direction (X direction) of the cylinder head 12 at a position on the upper surface 12M of the cylinder head 12 corresponding to the mounting position of the lower cam cap 14. Then, all of the fastening members are fastened to the reinforcing portion 32. This makes it possible to easily and reliably improve the rigidity of the structure for holding the camshafts 18, 20 to the cylinder head 12. Also, since the rigidity can be improved by efficiently using the fastening members for the reinforcing portion 32, it is possible to easily and reliably improve the rigidity for holding the camshafts 18, 20 to the cylinder head 12 without increasing the number of fastening members.

[0042] Although the embodiment of the present invention has been described above, the above-mentioned embodiment is presented as an example and is not intended to limit the scope of the present invention. This new embodiment can be embodied in various other forms. In addition, various omissions, substitutions, and modifications can be made without departing from the gist of the invention. In addition, this embodiment is included in the scope and gist of the invention, and is included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0043] 10 Internal combustion engine 12. Cylinder head 12M,14M top surface 14 Lower cam cap 14a, 14b Lower half hole 16 Upper Cam Cap 14N,16N bottom surface 16a, 16b Upper half hole 18,20 Camshaft 22 Pin Ring 22a, 22b, 24a, 24b Mounting parts 24 Straight pin 26 Spark plug storage compartment 26a,26b through hole 28 Outer periphery 30, 30A, 30B Outer wall 32 Reinforcement 34 Oil flow path 36, 38, 40, 42 Bolts (fastening members) 36a,36b,38a,40a,40b,42a,42b Penetration part 38b,36c,40c,42c Fastening section

Claims

1. a lower cam cap that can be attached to an upper surface of the cylinder head and has two lower half holes that can support a camshaft from a lower surface; an upper cam cap having two upper half holes facing the lower half holes and capable of supporting the camshaft from an upper surface thereof; a plurality of fastening portions that penetrate the lower cam cap and the upper cam cap and fasten the upper cam cap and the lower cam cap together; a plurality of fastening members capable of fastening the upper cam cap and the lower cam cap to the cylinder head by penetrating the upper cam cap and the lower cam cap at positions avoiding two cam holes formed by the combination of the upper half hole and the lower half hole; a reinforcing portion provided on the upper surface of the cylinder head at a position corresponding to a mounting position of the lower cam cap and integrally formed with one of the outer walls of the cylinder head in a short side direction of the cylinder head; a non-formed portion where the reinforcing portion is not formed, the non-formed portion being formed between the other of the outer walls of the cylinder head and the reinforcing portion in the short side direction of the cylinder head; Equipped with The non-forming portion is provided with an oil flow path, At least one of the plurality of fastening portions is provided at a position corresponding to the non-formed portion, and at least one of the plurality of fastening members does not reach the non-formed portion.

2. A straight pin is further provided for aligning the lower cam cap and the reinforcing portion of the cylinder head when they are assembled together.

2. The internal combustion engine of claim 1, wherein said straight pin is located below said lower half bore.

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