Internal combustion engine

Abstract

To facilitate the manufacture of a cylinder head by using a configuration in which a rocker arm holder is supported between cylinders of the cylinder head.SOLUTION: An internal combustion engine has a plurality of cylinders, a rocker arm shaft 53 parallel to a camshaft 52 between a cylinder head 32 and a head cover 33, a plurality of rocker arms 54 rockably on the rocker arm shaft 53, in which each rocker arm 54 drives a plurality of valves of each cylinder by a cam provided on the camshaft 52. The internal combustion engine has, between the cylinders, a rocker arm holder 71 that holds the rocker arm shaft 53, in which the rocker arm holder 71 is fastened to the cylinder head 32 via a base portion 72 that is separate from the cylinder head 32.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] The Unicam system is known as one type of valve operating system that has a single camshaft 52 in the cylinder head. The Unicam system has a rocker arm shaft that is parallel to the camshaft between the cylinder head and the head cover, and a rocker arm that is swingable on the rocker arm shaft, and the rocker arm drives multiple valves provided in the cylinder by a cam provided on the camshaft (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-035689 Summary of the Invention [Problem to be solved by the invention]

[0004] In the case of an internal combustion engine having multiple cylinders, a structure for supporting rocker arm holders that hold rocker arm shafts is required between the cylinders in the cylinder head. When fixing the rocker arm holder directly to the cylinder head, it is necessary to form a tall, columnar holder support part integrally with the cylinder head, extending from the cam chamber of the cylinder head toward the split surface (the surface where the cylinder head and head cover are separated), which makes it difficult to manufacture (by casting, for example) a cylinder head that maintains sufficient rigidity. Furthermore, if the cylinder head is made of an aluminum alloy, it may be necessary to enlarge the holder support portion to ensure rigidity, which may result in an increase in weight. The present invention has been made in consideration of the above-mentioned circumstances, and aims to make it easier to manufacture a cylinder head with appropriate rigidity using a configuration in which a rocker arm holder is supported between cylinders in the cylinder head. [Means for solving the problem]

[0005] The present invention provides an internal combustion engine having a plurality of cylinders, a rocker arm shaft parallel to a camshaft between a cylinder head and a head cover, a plurality of rocker arms swingably mounted on the rocker arm shaft, and each rocker arm driving a plurality of valves for each cylinder by a cam provided on the camshaft, the engine having a rocker arm holder for holding the rocker arm shaft between the cylinders, the rocker arm holder fastened to the cylinder head via a base portion separate from the cylinder head. [Effects of the Invention]

[0006] According to the present invention, a configuration in which a rocker arm holder is supported between cylinders of a cylinder head makes it easier to manufacture a cylinder head with appropriate rigidity. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a side view of a saddle-ride type vehicle according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing the cylinder head together with its internal structure. [Figure 3] FIG. 2 is a plan view of the rocker arm holder. [Figure 4] FIG. 2 is a front view of the rocker arm holder. [Figure 5] 4 is a cross-sectional view of FIG. 3 taken along line aa. [Figure 6] FIG. [Figure 7] 6B is a cross-sectional view of FIG. [Figure 8] 4 is a cross-sectional view showing the area of ​​a first holder hole and a first base fastening hole in a cylinder head together with the surrounding configuration. FIG. [Figure 9] 4 is a cross-sectional view showing the area of ​​the second base through-hole in the cylinder head together with the surrounding configuration. FIG. [Figure 10] 1 is a diagram illustrating an engine according to a reference example and an embodiment of the present invention; [Figure 11] FIG. 2 is a cross-sectional view showing a cross section of a rocker arm shaft together with the surrounding configuration. [Figure 12] FIG. 2 is a side cross-sectional view of the cylinder head. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the description, directions such as front, rear, left, right, up and down are the same as directions relative to the vehicle body unless otherwise specified. In addition, in each drawing, the symbol FR indicates the front of the vehicle body, the symbol UP indicates the upper side of the vehicle body, and the symbol LH indicates the left side of the vehicle body.

[0009] [Embodiment Mode] FIG. 1 is a side view of a saddle-ride type vehicle 10 according to an embodiment of the present invention. The saddle-ride type vehicle 10 is a vehicle that includes a body frame 11, a power unit 12 supported by the body frame 11, a front fork 14 that supports a front wheel 13 so as to be steerable, a swing arm 16 that supports a rear wheel 15, and a seat 17 for a passenger. The saddle-ride type vehicle 10 is a vehicle in which a passenger sits astride a seat 17. The seat 17 is provided above the rear part of the body frame 11.

[0010] The body frame 11 includes a head pipe 18 provided at the front end of the body frame 11, a front frame 19 located rearward of the head pipe 18, and a rear frame 20 located rearward of the front frame 19. The front end of the front frame 19 is connected to the head pipe 18. The seat 17 is supported by a rear frame 20 .

[0011] The front forks 14 are supported by a head pipe 18 so as to be steerable to the left and right. The front wheel 13 is supported by an axle 13a provided at the lower end of the front forks 14. A steering handle 21 that is held by the rider is attached to the upper end of the front forks 14.

[0012] The swing arm 16 is supported by a pivot shaft 22 that is supported by the body frame 11. The pivot shaft 22 is a shaft that extends horizontally in the vehicle width direction. The pivot shaft 22 is inserted into the front end of the swing arm 16. The swing arm 16 swings up and down around the pivot shaft 22. The rear wheel 15 is supported by an axle 15 a provided at the rear end of the swing arm 16 .

[0013] The power unit 12 is disposed between the front wheels 13 and the rear wheels 15 and is supported by the body frame 11. The power unit 12 is an internal combustion engine. The power unit 12 includes a crankcase 23 and a cylinder section 24 that houses a reciprocating piston. An exhaust device 25 is connected to an exhaust port of the cylinder section 24. The output of the power unit 12 is transmitted to the rear wheels 15 by a driving force transmission member that connects the power unit 12 and the rear wheels 15 .

[0014] The saddle-ride type vehicle 10 also includes a front fender 26 that covers the front wheel 13 from above, a rear fender 27 that covers the rear wheel 15 from above, a step 28 on which a rider places their feet, and a fuel tank 29 that stores fuel used by the power unit 12. The front fender 26 is attached to the front fork 14. The rear fender 27 and the step 28 are provided below the seat 17. The fuel tank 29 is supported by the body frame 11.

[0015] The crankcase 23 supports a crankshaft 30 that extends horizontally in the vehicle width direction (left-right direction). The cylinder section 24 extends upward from the front of the crankcase 23. The cylinder section 24 includes a cylinder block 31, a cylinder head 32 connected to the cylinder block 31, and a head cover 33 connected to the cylinder head 32. A cylinder axis 24a of the cylinder section 24 is inclined forward with respect to the vertical.

[0016] The power unit 12 is an in-line four-cylinder four-stroke engine having four cylinders aligned in the axial direction (vehicle width direction) of the crankshaft 30, and can also be referred to as an in-line four-cylinder internal combustion engine. Hereinafter, the power unit 12 will be referred to as the "engine 12."

[0017] FIG. 2 is a diagram showing the cylinder head 32 together with its internal structure. The cylinder head 32 has a hollow case shape that is open at the top and is produced by casting an aluminum alloy. Engine components other than the cylinder head 32, such as the crankcase 23, cylinder block 31, and head cover 33, are also produced by casting an aluminum alloy. The aluminum alloy that constitutes these components may contain other materials such as magnesium or silicon. These components may also be produced from materials other than aluminum alloys (for example, cast iron).

[0018] 2, a valve train 51 that drives the intake and exhaust valves (intake valves, exhaust valves) of each cylinder is disposed in the cylinder head 32. The valve train 51 is housed between the cylinder head 32 and the head cover 33. The valve train 51 includes a camshaft 52 arranged above the intake valve, a rocker arm shaft 53 arranged parallel to the camshaft 52, and a plurality of rocker arms 54 supported by the rocker arm shaft 53 so as to be swingable, and can also be called a unicam type valve train mechanism.

[0019] Camshaft 52 has a plurality of intake cams 61 that respectively drive the intake valves of the cylinders, and a plurality of exhaust cams 62 that respectively swing rocker arms 54. A cam sprocket 63 is connected to one end of camshaft 52, and cam sprocket 63 is synchronized with the rotation of crankshaft 30 via a cam chain so that cam sprocket 63 rotates once for every two rotations of crankshaft 30. The engine 12 is configured as a four-valve engine with two intake valves and two exhaust valves per cylinder. Therefore, the camshaft 52 is provided with eight intake cams 61 that drive the eight intake valves for the four cylinders, respectively, and eight exhaust cams 62 that swing the eight rocker arms 54 that drive the eight exhaust valves, respectively.

[0020] 2 shows the lateral center CT of each cylinder, as well as multiple plug ports 65 that communicate with the combustion chamber of each cylinder. The lateral center CT of each cylinder coincides with the lateral center of each plug port 65. The two rocker arms 54 provided for each cylinder are positioned on either side of the lateral center CT of the cylinder, thereby avoiding the plug ports 65. Reference numeral 66 in FIG. 2 denotes an intake port connected to the combustion chamber of each cylinder. The plug is a center plug. The rocker arm 54 is disposed so as to straddle the rocker arm shaft 53. However, the shape and layout of each part of the engine 12 may be changed as appropriate. For example, the engine 12 does not have to be limited to a four-cylinder engine, and may be an engine with two or more cylinders (a multi-cylinder engine).

[0021] Furthermore, in this embodiment, a configuration is shown in which camshaft 52 is provided above the intake valves, and the intake valves are directly driven by camshaft 52, and the exhaust valves are driven by camshaft 52 via rocker arms 54, but the configuration is not limited to this. For example, a configuration may be used in which camshaft 52 is provided above the exhaust valves, and the exhaust valves are directly driven by camshaft 52, and the intake valves are driven by camshaft 52 via rocker arms 54, or a configuration may be used in which both the intake and exhaust valves are driven via rocker arms.

[0022] 2, a rocker arm holder 71 that holds the rocker arm shaft 53 is provided between the cylinders of the cylinder head 32. The rocker arm holder 71 is also sometimes called a rocker arm shaft holder. The rocker arm holders 71 between the cylinders are fastened to the cylinder head 32 via base portions 72 that are separate from the cylinder head 32. Rocker arm holders 71 that hold rocker arm shafts 53 are also provided on the left and right outer sides of the cylinders at both ends. The rocker arm holders 71 on the outer sides of the cylinders are also fastened to the cylinder head 32 via base portions 72 that are separate from the cylinder head 32.

[0023] Next, a detailed description will be given of the rocker arm holder 71 and base portion 72 between the cylinders. Note that for the rocker arm holder 71 and base portion 72 on the outer side of the cylinder, the same parts as those of the rocker arm holder 71 and base portion 72 between the cylinders are designated by the same reference numerals, and redundant explanations will be omitted.

[0024] 3 is a plan view of the rocker arm holder 71, FIG. 4 is a front view, and FIG. 5 is a cross-sectional view taken along line aa in FIG. 3 to 5, rocker arm holder 71 is integrally provided with a pair of shaft support portions 71b each having a shaft hole 71a through which rocker arm shaft 53 is inserted, and a connecting portion 71c that connects the pair of shaft support portions 71b. Rocker arm shaft 53 is rotatably supported by the pair of shaft support portions 71b.

[0025] Furthermore, the rocker arm holder 71 has a pair of through holes 71d (hereinafter referred to as first holder holes 71d) into which fastening bolts 81 (hereinafter referred to as first fastening bolts 81) shown in Figure 5 etc. are inserted, a through hole 71e (hereinafter referred to as holder common hole 71e) into which fastening bolt 82 (hereinafter referred to as common fastening bolt 82) is inserted, and a positioning hole 71f (hereinafter referred to as holder positioning hole 71f) into which a positioning member 83 (e.g., a knock pin) is inserted.

[0026] The rocker arm holder 71 is made of a part manufactured by heating a sintered material made from an appropriate metal powder at high temperatures, i.e., it is made of a sintered body. A sintered body can increase the density of the metal, thereby increasing its strength (which can also be described as rigidity or durability). In addition, since a sintered body can be manufactured into complex shapes, it is possible to manufacture a rocker arm holder 71 with high precision. This makes it possible to minimize draft angles and unnecessary shapes, which is advantageous for weight reduction.

[0027] FIG. 6 is a plan view of the base portion 72, and FIG. 7 is a cross-sectional view taken along line bb in FIG. 6 and 7, the base portion 72 is formed in the shape of a generally triangular flat plate when viewed from above. The base portion 72 has a pair of fastening holes 72d (hereinafter referred to as first base fastening holes 72d) that communicate with the first holder holes 71d of the rocker arm holder 71, a through-hole 72e (hereinafter referred to as base common hole 72e) that communicates with the holder common hole 71e, and a positioning hole 72f (hereinafter referred to as base positioning hole 72f) that communicates with the holder positioning hole 71f.

[0028] 7, the first base fastening hole 72d is a threaded hole (internal thread) into which the first fastening bolt 81 can be fastened, and the base common hole 72e is a hole through which the common fastening bolt 82 can pass. A common positioning member 83 is inserted into both positioning holes 71f, 72f of the rocker arm holder 71 and the base portion 72, thereby positioning the rocker arm holder 71 and the base portion 72.

[0029] Furthermore, the base portion 72 has a pair of through holes 72g (hereinafter referred to as second base through holes 72g) into which fastening bolts 84 (hereinafter referred to as second fastening bolts 84) shown in FIG. 7 and the like are inserted, respectively. The base portion 72 is made of a cast part formed by pouring molten cast iron into a mold. This results in a base portion 72 that is highly rigid and can be expected to absorb vibrations. Any suitable type and composition of cast iron can be used. Furthermore, the vibration absorption properties can be adjusted appropriately by adjusting the thickness of the base portion 72, etc.

[0030] FIG. 8 is a cross-sectional view showing the area of ​​the first holder hole 71d and the first base fastening hole 72d in the cylinder head 32 together with the surrounding configuration. As shown in Fig. 8, the first fastening bolts 81 are inserted into the first holder holes 71d of each rocker arm holder 71 and fastened to the first base fastening holes 72d of each base portion 72. As a result, each rocker arm holder 71 is fastened to each base portion 72 by the two first fastening bolts 81. As shown in Fig. 8, each first fastening bolt 81 is formed to a length that does not pass through the base portion 72.

[0031] FIG. 9 is a cross-sectional view showing the area of ​​each second base through-hole 72g of the base portion 72 in the cylinder head 32 together with the surrounding configuration. 9, the second fastening bolts 84 are inserted into the second base through-holes 72g of each base portion 72 and fastened to the fastening holes 32g provided in advance in the cylinder head 32. As a result, each rocker arm holder 71 is fastened to the cylinder head 32 by the two second fastening bolts 84.

[0032] 5 and 7, the common fastening bolts 82 are inserted into the holder common holes 71e of each rocker arm holder 71 and the base common holes 72e of each base portion 72, and then fastened to fastening holes (not shown) that are provided in advance in the cylinder head 32. The common fastening bolts 82 pass through the base portions 72 to directly fasten the rocker arm holders 71 and the cylinder head 32, improving the accuracy and ease of assembly when assembling the rocker arm holders 71 and the cylinder head 32.

[0033] Next, the engine 12 of the reference example and the present embodiment will be described with reference to FIG. The engine 12A of the reference example has a configuration in which rocker arm holders 71 between the cylinders are fixed directly to the cylinder head 32. In this engine 12A, a tall columnar portion 32x (hereinafter referred to as the holder support portion 32x) that supports the rocker arm holder 71 is integrally formed between the cylinders of the cylinder head 32, and the rocker arm holder 71 is fastened to the holder support portion 32x with a fastening bolt 81x.

[0034] As described above, between the cylinders there are two rocker arms 54 that operate the valves of adjacent cylinders, so at least a reaction force f1 from the two rocker arms 54 and exhaust valves that swing at different times acts on the rocker arm holder 71 between the cylinders. The reaction force f1 from the left and right generates a high-frequency vibration force f2 that vibrates the rocker arm holder 71 in small increments. When the columnar holder support portion 32x vibrates due to this vibration force f2, stress may be concentrated at the base of the holder support portion 32x, and a high stress σ may act on the base. Therefore, it is necessary to manufacture a cylinder head 32 that has a high rigidity base portion while providing a tall columnar holder support portion 32x, which makes manufacturing the cylinder head 32 difficult.

[0035] In particular, in the case of a cylinder head 32 made of an aluminum alloy, increasing the rigidity of the cylinder head 32 may result in an increase in size and weight.

[0036] 10, in the engine 12 of this embodiment, the rocker arm holder 71 between the cylinders is fastened to the cylinder head 32 via a base portion 72 that is separate from the cylinder head 32. Therefore, the height H of the holder support portion 32x that supports the rocker arm holder 71 in the cylinder head 32 is lower than the height Ha of the holder support portion 32x in the reference example. Because the height H of the holder support portion 32x is low, the rigidity of the holder support portion 32x is increased, making it easier to suppress the amount of vibration of the holder support portion 32x and to suppress the vibration of the holder support portion 32x itself.

[0037] In this embodiment, a first fastening bolt 81 that fastens the rocker arm holder 71 to the base portion 72, and a second fastening bolt 84 that fastens the base portion 72 to the cylinder head 32 are located between the rocker arm holder 71 and the cylinder head 32. A tensile axial force is generated by fastening these bolts 81, 84, and this tensile axial force causes the bolts 81, 84 to elastically deform in the expansion / contraction direction, which is expected to have the effect of mitigating and absorbing the vibration force f2 transmitted to the cylinder head 32. Therefore, compared to the engine 12A that has only one stage of fastening bolts, the presence of two stages of fastening bolts 81, 84 can further alleviate and absorb stress generated around the rocker arm holder 71. This also makes it easier to suppress the amount of vibration of the holder support portion 32x, and to suppress the vibration of the holder support portion 32x itself.

[0038] Furthermore, since the fastening position of the cylinder head 32 (the position of the second fastening bolt 84) is close to the base portion of the holder support portion 32x and is relatively far from the surface of the base portion, the rigidity of the base portion and its surrounding area is increased, and the transmission of vibration force f2 to the surface of the cylinder head 32 can be suppressed. In this way, the rigidity of the holder support portion 32x can be increased and the transmission of vibrations to the base portion of the holder support portion 32x, etc. can be suppressed, thereby improving the rigidity of the cylinder head 32 and alleviating and absorbing stress generated around the rocker arm holder 71.

[0039] Furthermore, because the base portion 72 of the engine 12 is made of cast iron, it is possible to obtain a base portion 72 that is highly rigid and has vibration absorption properties. This also helps to reduce the vibration force f2 transmitted to the cylinder head 32, which is advantageous for improving the rigidity of the cylinder head 32.

[0040] 7, in the region of the base portion 72 facing the cylinder head 32 (the lower surface region of the base portion 72), foot portions 72t are formed in locations corresponding to the base common hole 72e and the second base through-hole 72g, protruding toward the cylinder head 32. The spaces between the foot portions 72t are formed into recessed portions 72v that are recessed upward. 9, when the base portion 72 and the cylinder head 32 are fastened together, each foot portion 72t of the base portion 72 abuts against the cylinder head 32, and the recessed portions 72v form a space between the base portion 72 and the cylinder head 32. By providing this space, heat transfer from the cylinder head 32 to the base portion 72 and the rocker arm holder 71 can be more easily suppressed.

[0041] Figure 11 is a cross-sectional view showing the rocker arm shaft 53 together with the surrounding structure, with arrows indicating the flow of oil from the oil pump. In Figure 11, reference numeral 67 denotes an exhaust port connected to the combustion chamber of each cylinder. As shown in Figure 11, the rocker arm shaft 53 is divided into left and right halves. A first oil passage 91 is provided in the cylinder head 32 to supply oil from the cylinder block 31 to the area between the left and right rocker arm shafts 53a, 53b. The first oil passage 91 supplies oil from the cylinder block 31 to the left and right rocker arm shafts 53a, 53b, respectively. Second oil passages 92 are provided in the left and right rocker arm shafts 53a, 53b at intervals in the axial direction, and supply oil from each shaft 53a, 53b to the bearings of the camshaft 52.

[0042] This allows rocker arm shaft 53 to double as part of the oil passage. Moreover, oil is distributed from the center of rocker arm shaft 53 in the longitudinal direction to both sides of rocker arm shaft 53 and supplied to the oil supply points of camshaft 52 from second oil passage 92 provided in rocker arm shaft 53, so the oil passages from cylinder block 31 to each oil supply point of camshaft 52 can be shortened and the lengths of the oil passages to each oil supply point can be made uniform. This makes it easier to shorten and uniform the oil arrival time. If the rocker arm shaft 53 were not divided and oil were supplied from one end of the rocker arm shaft 53 and from each second oil passage 92 of the rocker arm shaft 53, the time it takes for oil to reach the farthest second oil passage 92 would be longer and the variation in the oil arrival time would also be greater.

[0043] FIG. 12 is a side cross-sectional view of the cylinder head 32, with arrows indicating the flow of oil from the oil pump. 12, the cylinder head 32 is provided with an oil passage 91 extending upward from the lower surface of the cylinder head 32 and an oil passage 96 extending downward from the upper surface of the cylinder head 32, spaced apart in the front-to-rear direction. A cross oil passage 97 extending in the front-to-rear direction is provided to connect these oil passages 91, 92. These oil passages 91 to 93 form an oil passage that flows oil from the cylinder block 31 through the cylinder head 32 to the head cover 33.

[0044] The cross oil passage 97 is formed by extending a pilot hole of a female screw provided for fastening a predetermined part to the cylinder head 32. This makes it possible to reduce the space and machining required for the oil passage.

[0045] The oil passage 95, into which oil flows from the cylinder block 31, extends above the intersecting oil passage 97. An oil passage 98 is further formed that extends in the front-to-rear direction of the head cover 33 above the intersecting oil passage 97 and parallel to the intersecting oil passage 97 so as to intersect with the oil passage 95. The oil passage 98 supplies some of the oil from the cylinder block 31 to a tensioner lifter of the cam chain.

[0046] As described above, the engine 12 of this embodiment has the rocker arm holder 71 that holds the rocker arm shaft 53 between the cylinders, and the rocker arm holder 71 is fastened to the cylinder head 32 via the base portion 72 that is separate from the cylinder head 32, so the height H of the holder support portion 32x of the cylinder head 32 can be reduced. This makes it easier to ensure the rigidity of the holder support portion 32x and to manufacture the cylinder head 32. Therefore, with a configuration in which the rocker arm holder 71 is supported between the cylinders of the cylinder head 32, it becomes easier to manufacture a cylinder head 32 with appropriate rigidity, and it is possible to prevent the cylinder head 32 from becoming larger in size in order to ensure rigidity. Furthermore, since it is easy to ensure the rigidity of the cylinder head 32, even if the cylinder head 32 is made of an aluminum alloy, it is possible to prevent the cylinder head 32 from becoming larger and its weight from increasing.

[0047] Additionally, the rocker arm holder 71, base portion 72, and cylinder head 32 are fastened together with bolts consisting of a first fastening bolt 81, a second fastening bolt 84, and a common fastening bolt 82. A tensile axial force is generated in the bolts when fastened together, and this tensile axial force causes the bolts to elastically deform in the expansion and contraction direction, thereby alleviating and absorbing stress generated around the rocker arm holder 71.

[0048] Furthermore, since the rocker arm holder 71 is made of a sintered body, it is possible to obtain a rocker arm holder 71 that is high in strength and precision, and it is possible to minimize draft angles and unnecessary shapes. Furthermore, since the base portion 72 is made of cast iron, it is possible to obtain a base portion 72 that is strong and can be expected to absorb vibrations.

[0049] In addition, there are multiple bolts, and at least one of the bolts is a common fastening bolt 82 that penetrates the base portion 72 and directly fastens the rocker arm holder 71 and the cylinder head 32, thereby improving the accuracy and ease of assembly when assembling the rocker arm holder 71 and the cylinder head 32.

[0050] In addition, the bolts include a first fastening bolt 81 that fastens the rocker arm holder 71 and the base portion 72 together, and a second fastening bolt 84 that fastens the base portion 72 and the cylinder head 32 together, so it is expected that the bolts 81, 84 will have the effect of mitigating and absorbing vibrations between the rocker arm holder 71 and the base portion 72, and between the base portion 72 and the cylinder head 32, respectively.

[0051] Furthermore, a portion of the base portion 72 is shaped to form a space between it and the cylinder head 32, which makes it easier to achieve the effects of reducing weight, ensuring space for oil flow, and suppressing heat transfer from the cylinder head 32.

[0052] [Other embodiments] The above-described embodiment merely shows one aspect of the present invention, and any modifications and applications are possible without departing from the spirit of the present invention.

[0053] In the above embodiment, the present invention has been described as being applied to the engine (internal combustion engine) 12 of the saddle-ride type vehicle 10 shown in FIG. 1, but the present invention may also be applied to the engine of any saddle-ride type vehicle, the engine of a vehicle other than a saddle-ride type vehicle, or an engine used in something other than a vehicle.

[0054] [Configuration supported by the above embodiment] The above embodiment supports the following configurations.

[0055] (Configuration 1) An internal combustion engine having a plurality of cylinders, a rocker arm shaft parallel to a camshaft between a cylinder head and a head cover, a plurality of rocker arms swingably attached to the rocker arm shaft, and each rocker arm driving a plurality of valves for each cylinder by a cam provided on the camshaft, and a rocker arm holder for holding the rocker arm shaft between the cylinders, the rocker arm holder being fastened to the cylinder head via a base portion separate from the cylinder head. With this configuration, the holder support portion that supports the rocker arm holder in the cylinder head can be lowered, and a configuration that supports the rocker arm holder between the cylinders of the cylinder head makes it easier to manufacture a cylinder head with appropriate rigidity.

[0056] (Configuration 2) The internal combustion engine according to configuration 1, wherein the rocker arm holder, the base portion, and the cylinder head are fastened together with bolts. With this configuration, a tensile axial force is generated in the bolt when it is fastened, and this tensile axial force causes the bolt to elastically deform in the expansion and contraction direction, thereby alleviating and absorbing the stress generated around the rocker arm holder.

[0057] (Configuration 3) The internal combustion engine according to configuration 1 or 2, wherein the rocker arm holder is made of a sintered body. This configuration makes it possible to obtain a rocker arm holder that is strong and has high precision, and minimizes draft angles and unnecessary shapes.

[0058] (Configuration 4) The internal combustion engine according to any one of configurations 1 to 3, wherein the base portion is made of cast iron. This configuration makes it possible to obtain a base portion that is strong and can be expected to absorb vibrations.

[0059] (Configuration 5) The internal combustion engine according to configuration 2, wherein the bolts are plural, and at least one of the bolts penetrates the base portion to directly fasten the rocker arm holder and the cylinder head. This configuration improves the accuracy and ease of assembly when assembling the rocker arm holder and the cylinder head.

[0060] (Configuration 6) The internal combustion engine according to configuration 2 or 5, wherein the bolts include a first fastening bolt that fastens the rocker arm holder and the base portion together, and a second fastening bolt that fastens the base portion and the cylinder head together. With this configuration, it is expected that the vibrations between the rocker arm holder and the base portion, and the vibrations between the base portion and the cylinder head will be reduced and absorbed by the bolts.

[0061] (Configuration 7) The internal combustion engine according to any one of configurations 1 to 6, wherein a portion of the base portion has a shape that forms a space between the base portion and the cylinder head. This configuration makes it easier to obtain the effects of weight reduction, ensuring space for oil flow, and suppressing heat transfer from the cylinder head by using the space. [Explanation of symbols]

[0062] 10 Saddle-type vehicle 11 Body frame 12 Power unit (engine, internal combustion engine) 30 crankshaft 31 Cylinder block 32 cylinder head 32g fastening hole 32x holder support 33 Headcover 53, 53a, 53b Rocker arm shaft 54 Rocker arm 61 Intake cam 62 exhaust cam 71 Rocker arm holder 72 Base 81 First fastening bolt 82 Common fastening bolt 83 Positioning member 84 Second fastening bolt CT cylinder center

Claims

1. An internal combustion engine having a plurality of cylinders, a rocker arm shaft (53) parallel to a camshaft (52) between a cylinder head (32) and a head cover (33), a plurality of rocker arms (54) swingably mounted on the rocker arm shaft (53), and each rocker arm (54) drives a plurality of valves of each cylinder by a cam provided on the camshaft (52), A rocker arm holder (71) is provided between the cylinders to hold the rocker arm shaft (53), The rocker arm holder (71) is fastened to the cylinder head (32) via a base portion (72) separate from the cylinder head (32). Internal combustion engine.

2. The rocker arm holder (71), the base portion (72), and the cylinder head (32) are fastened together with bolts (81, 82, 84).

2. The internal combustion engine according to claim 1.

3. The rocker arm holder (71) is made of a sintered body.

2. The internal combustion engine according to claim 1.

4. The base portion (72) is made of cast iron. An internal combustion engine according to any one of claims 1 to 3.

5. There are a plurality of bolts, and at least one of the bolts penetrates the base portion (72) to directly fasten the rocker arm holder (71) and the cylinder head (32).

3. The internal combustion engine according to claim 2.

6. Proposed additional claims The bolts (81, 82, 84) include a first fastening bolt (81) that fastens the rocker arm holder (71) to the base portion (72) and a second fastening bolt (84) that fastens the base portion (72) to the cylinder head (32).

6. An internal combustion engine according to claim 2 or 5. Action and effect)

7. A part of the base portion (72) is shaped to form a space between it and the cylinder head (32). An internal combustion engine according to any one of claims 1 to 3.

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