Cylinder block for internal combustion engine

Abstract

The present invention is a cylinder block for an internal combustion engine. The cylinder block keeps heat from a combustion chamber from increasing the temperature of the oil in an oil supply passage of the cylinder block and thereby contributes to energy efficiency.　Disclosed is a cylinder block 42 for an internal combustion engine 4 that comprises: a crankcase 40 that rotatably supports a crankshaft 41; the cylinder block, which is connected to the crankcase and forms a cylinder 42a; and a cylinder head 43 that is connected to the cylinder block, has an intake port 45 and an exhaust port 46 formed therein, and comprises a valvetrain 60. The cylinder block is provided with an oil supply passage 91 that runs from the crankcase side to the cylinder head side. Oil that circulates through the internal combustion engine is supplied into the oil supply passage. A gap 95 is provided between the oil supply passage and the cylinder formed by the cylinder block.

Description

Cylinder block of an internal combustion engine

[0001] The present invention relates to a cylinder block for an internal combustion engine that can suppress a rise in temperature of an oil supply passage.

[0002] In recent years, research has been conducted into improving the energy efficiency of internal combustion engines, which contribute to energy efficiency, in order to ensure that more people have access to affordable, reliable, sustainable, and advanced energy. To improve the thermal efficiency of internal combustion engines, structures in which surface treatment is performed to provide a heat insulating effect around the combustion chamber of an internal combustion engine are disclosed, for example, in Patent Documents 1 to 3 listed below. However, when a heat insulating effect is required for the oil supply passage in the cylinder block, applying a surface treatment that provides a heat insulating effect increases the cost and process burden.

[0003] Japanese Patent Publication No. 2009-243355 (FIGS. 1 and 2), Japanese Patent Publication No. 2015-031226 (FIGS. 1 to 3), and WO2014 / 024494 (FIGS. 1 to 5)

[0004] In the technology for improving the energy efficiency of an internal combustion engine, a problem to be solved is how to prevent the temperature of oil in the oil supply passage of the cylinder block from rising due to heat from the combustion chamber. In order to solve the problem, the present invention aims to provide a cylinder block for an internal combustion engine that can prevent the temperature of oil in the oil supply passage of the cylinder block from rising due to heat from the combustion chamber without performing a surface treatment to provide a heat insulating effect around the combustion chamber of the internal combustion engine, thereby contributing to energy efficiency.

[0005] In order to solve the above problems, the cylinder block of an internal combustion engine of the present invention comprises: a crankcase in which a crankshaft is rotatably supported; a cylinder block connected to the crankcase and forming a cylinder portion; and a cylinder head connected to the cylinder block, having an intake port and an exhaust port formed therein and equipped with a valve mechanism, wherein the cylinder block is provided with a supply oil passage communicating from the crankcase side to the cylinder head side, oil circulating through the internal combustion engine is supplied into the supply oil passage, and a gap is provided between the cylinder portion formed in the cylinder block and the supply oil passage.

[0006] According to the above configuration, a gap that serves as an insulating space is provided between the cylinder portion that constitutes the combustion chamber and the supply oil passage, which makes it possible to prevent the oil in the supply oil passage from rising in temperature due to the heat of the combustion chamber, thereby contributing to energy efficiency.

[0007] According to a preferred embodiment of the present invention, the gap is provided between the oil supply passage and a stud bolt that is inserted through the cylinder block and fastens the cylinder head and cylinder block to the crankcase, allowing heat generated in the combustion chamber to be released to the crankcase by the stud bolt, thereby making it possible to achieve a structure in which the temperature of the oil in the oil supply passage does not easily rise.

[0008] According to a preferred embodiment of the present invention, the cross-sectional area of ​​the gap perpendicular to the cylinder axis increases from the crankcase side toward the cylinder head side in the cylinder block. In this way, the gap increases as it approaches the combustion chamber formed on the cylinder head side of the cylinder portion, which generates a large amount of heat, so that the oil in the oil supply passage is less likely to become hot.

[0009] According to a preferred embodiment of the present invention, the cylinder block is provided with a hydraulic tensioner for maintaining tension on a transmission member that couples the crankshaft and the valve mechanism, and the oil supply passage is connected to a branch at the mating surface between the cylinder block and the cylinder head, which branch into a first oil passage formed in the cylinder head and supplying oil to the valve mechanism, and a second oil passage formed in the mating surface and supplying oil to the hydraulic tensioner, and the second oil passage is disposed near the branch in a direction away from the cylinder axis in the crankshaft direction or further. This allows the second oil passage from the branch to the hydraulic tensioner to be formed farther away from the cylinder portion and stud bolts near the branch, thereby increasing the cross-sectional area of ​​the gap at the mating surface between the cylinder block and the cylinder head, and increasing the volume of the gap, thereby improving the thermal insulation effect. This configuration makes it difficult for the oil in the oil supply passage to rise in temperature.

[0010] According to the cylinder block of the internal combustion engine of the present invention, a gap that serves as an insulating space is provided between the cylinder portion that constitutes the combustion chamber and the oil supply passage, which makes it possible to prevent the oil in the oil supply passage from rising in temperature due to heat from the combustion chamber, thereby contributing to energy efficiency.

[0011] FIG. 4 shows an outline of the right side of a motorcycle equipped with a power unit having a cylinder block of an internal combustion engine according to this embodiment. FIG. 5 is a right side view from the crankcase to the head cover of the internal combustion engine of the power unit of FIG. 1. FIG. 6 is a top cross-sectional view of the internal combustion engine taken along arrows III-III in FIG. 2. FIG. 7 is a front view of the cylinder block taken along arrows IV-IV in FIG. 3. FIG. 8 is a rear view of the cylinder block taken along arrows V-V in FIG. 3. FIG. 9 is a right side cross-sectional view taken along arrows VI-VI in FIG. 3 and FIG. 4, passing through an oil supply passage in the cylinder block of the internal combustion engine.

[0012] A cylinder block of an internal combustion engine according to one embodiment of the present invention will be described with reference to Figures 1 to 6. Note that directions such as front, rear, left, right, up, down, etc. in the description and claims of this specification refer to directions of a vehicle equipped with a power unit including an internal combustion engine according to this embodiment. Specifically, the vehicle in this embodiment is a scooter-type motorcycle (hereinafter simply referred to as a "motorcycle"). In the drawings, arrows FR, LH, RH, and UP indicate the front, left, right, and top directions, respectively.

[0013] 1 shows an outline of the right side of a motorcycle 1 equipped with a power unit 3 having a cylinder block of an internal combustion engine according to this embodiment. Motorcycle 1 has a front body 1F and a rear body 1R connected via a low floor section 1C, and a body frame 2 forming the skeleton of the vehicle body is generally composed of a down tube 21 and a main pipe 22. That is, the down tube 21 extends downward from a head pipe 20 in the front body 1F, bends horizontally at its lower end, extends rearward below the floor section 1C, and is connected at its rear end to a pair of left and right main pipes 22. The main pipes 22 have rising sections 22a that rise diagonally rearward from the connecting section, then bend approximately horizontally at a predetermined height before extending rearward.

[0014] A fuel tank and storage box (not shown) are supported by the main pipe 22, and above that, a bracket 23 protrudes from the rising portion 22a of the riding-in pipe 22. A power unit side bracket 33 is attached to the bracket 23 via a link member 24, and a swing-type power unit (hereinafter simply referred to as "power unit") 3 is connected and supported so that it can swing up and down together with the rear wheel 15. In other words, the motorcycle 1 of this embodiment employs an upper link support structure for the power unit 3.

[0015] The power unit 3 is provided with a forced-air-cooled, single-cylinder, four-stroke internal combustion engine 4 in the front part of its unit case 30, which forms a crankcase 40 for the internal combustion engine 4. The internal combustion engine 4 rotatably supports a crankshaft 41, the axis of which is arranged in the vehicle width direction, in the crankcase 40. The internal combustion engine 4 also includes a cylinder block 42 connected to the crankcase 40 and forming a cylinder section 42a, a cylinder head 43 connected to the cylinder block 42 and forming an intake port 45 and an exhaust port 46, and a head cover 44 that covers the cylinder head 43, and is provided in the power unit 3 with the cylinder block 42, cylinder head 43, and head cover 44 tilted forward to a nearly horizontal position.

[0016] The unit case 30 of the power unit 3 extends from the internal combustion engine 4 to the left rear and constitutes a transmission case 31 that houses a belt-type continuously variable transmission, and the rear wheel 15 is journaled on a reduction gear mechanism 32 provided at the rear of the transmission case 31. As shown in FIG. 1, a rear cushion 16 is interposed between the rear end of the unit case 30 and the rear of the main pipe 22.

[0017] A throttle body 52 connected to an intake pipe 51 extending from the inlet of the intake port 45 at the top of the cylinder head 42 of the internal combustion engine 4, and an air cleaner 53 connected to the throttle body 52 are disposed on top of the power unit 3. An exhaust pipe 55 connected to the outlet of the exhaust port 46 at the bottom of the cylinder head 42 bends rearward, extends rearward along the right side of the vehicle, and connects to a muffler 56 on the right side of the rear wheel 15. The muffler 56 is attached to the unit case 30 via a muffler stay 56a.

[0018] The front portion 1F of the vehicle body is covered at the front and rear by a front cover 17a and a rear cover 17b, and a handle cover 17c covers the center portion of the handle 12. A step plate 17d is attached to the floor portion 1C, and lower side covers 17e are extended downward along the left and right edges of this step plate 17d.

[0019] A body cover 17f is connected to the rear of the step plate 17d above the rear of the vehicle body 1R, and covers the main pipe 22 from the front to the left and right sides, with the seat 11 being able to open and close and cover the upper end opening of the body cover 17f. A rear fender 18 extends diagonally downward from the rear portion of the body cover 17f, tapering diagonally upward and rearward in a side view, and covers the rear wheel 15 from above.

[0020] 2 is a right side view of the internal combustion engine 4 of the power unit 3, from the crankcase 40 to the head cover 44. The internal combustion engine 4 of this embodiment is of a forced-air-cooled type, with the right side of the crankcase 40 covered by a fan cover 70, which has a cooling air intake window 71 opening around the axis of the crankshaft 41. A rotary fan (not shown) is provided inside the cooling air intake window 71, concentric with the crankshaft 41. The cylinder block 42 and cylinder head 43 are covered by a shroud 72, indicated by a two-dot chain line, which communicates with the fan cover 70. Outside cooling air is taken in through the cooling air intake window 71 by the rotary fan, which rotates together with the crankshaft 41, and is forcibly sent into the shroud 72 via the fan cover 70, where it cools the cylinder block 42 and cylinder head 43 before being discharged.

[0021] The internal combustion engine 4 of this embodiment employs an SOHC type valve system, and a cam chain (referred to as a "transmission member" in this invention) 62 that rotates the camshaft 61 in response to rotation of the crankshaft 41 is installed between a driven sprocket 61 a of a camshaft 61 of a valve train 60 provided in the cylinder head 43 and a drive sprocket 41 a of the crankshaft 41. A cam chain chamber 63 for this purpose is provided in a side portion of the crankcase 40, cylinder block 42, and cylinder head 43, and in this embodiment, is provided in communication with the left portion (see FIGS. 3 and 4).

[0022] The crankshaft 41 is rotated clockwise in Figure 2 by the back and forth movement of a piston (not shown) that slides within a cylinder portion 42a (see Figure 4) oriented approximately in the front-rear direction and provided in the cylinder block 42. A camshaft 61 is supported between the front end of the cylinder head 43 and the head cover 44 so as to be rotatable parallel to the crankshaft 41.

[0023] A combustion chamber 65 is formed between the cylinder head 43 and the front of the piston (not shown) of the cylinder section 42a that moves back and forth, and the portion of the cylinder head 43 facing the cylinder section 42a forms a combustion chamber ceiling surface 65a (see Figure 4). The cylinder head 43 is provided with intake and exhaust valves (not shown) for controlling the intake and exhaust of the combustion chamber 65, and the lift amount and opening and closing timing of the intake and exhaust valves are controlled by cam surfaces provided on a camshaft 61 of the valve train 60 in accordance with the rotation of the camshaft 61.

[0024] That is, the valve train 60 is linked to the crankshaft 41 by the transmission member 62, and the rotational torque of the crankshaft 41, which is rotated clockwise in FIG. 2 by the up and down movement of the piston, is transmitted to the camshaft 61 via the wound cam chain 62, and the intake valve and exhaust valve open and close at predetermined timings with respect to the combustion stroke of the internal combustion engine 4, an intake valve opening 66 of the intake port 45 which opens to the combustion chamber ceiling surface 65a, and an exhaust valve opening 67 of the exhaust port 46 (see FIG. 4).

[0025] In order for the intake and exhaust valves to open and close properly at the specified timing, it is necessary to always maintain an appropriate tension in the cam chain 62. However, vibrations can occur in the cam chain 62 due to sudden changes in the rotational speed of the crankshaft 41 caused by sudden acceleration or deceleration by the driver, or changes in running resistance from the road surface.

[0026] In this embodiment, as viewed from the right side in Figure 2, clockwise rotation of the drive sprocket 41a causes the cam chain 62 to run while meshing with the drive sprocket 41a and the driven sprocket 61a, with the upper cam chain 62a, which is sent out from the drive sprocket 41a to the driven sprocket 61a, being slack, and the lower cam chain 62b, which is pulled by the drive sprocket 41a, being tight.

[0027] In order to prevent the above-mentioned vibration of the cam chain 62 and to apply a constant tension to it, the internal combustion engine 4 is provided with a cam chain tensioner mechanism 80 that presses the slack side of the cam chain 62, i.e., the upper cam chain 62a, with a predetermined pressure to maintain the tension of the cam chain 62, and the cylinder block 42 is provided with a tensioner slipper 81 that presses and guides the cam chain 62 for sliding, and a hydraulic tensioner 82 that presses the tensioner slipper 81 with a predetermined pressure.

[0028] Meanwhile, an oil pan 47 (see FIG. 5) is provided below the crankcase 40. An oil pump (not shown) driven by the power of the crankshaft 41 is also provided inside the crankcase 40. When the oil pump is driven by the crankshaft 41, engine oil (hereinafter also referred to simply as "oil" in the claims) stored in the oil pan 47 is drawn through a strainer (not shown) and sent from the oil pump to various parts of the internal combustion engine 1 through multiple oil passages. Reference numeral 57 in FIG. 2 denotes an O2 sensor for exhaust gas. Reference numeral 33 denotes a power unit-side bracket for the upper link support structure of the power unit 3 described above.

[0029] Figure 3 is a top cross-sectional view of the internal combustion engine 4 taken along the line III-III in Figure 2. The small black arrows in Figure 3 schematically show the flow of oil. The valve train 60 described above requires a supply of oil to the camshaft 61 to lubricate the bearings, cams, and other components around the camshaft 61, and the cam chain tensioner mechanism 80 requires a supply of oil to operate the hydraulic tensioner 82.

[0030] 3, the cylinder block 41 is provided with an internal oil supply passage 91 (the "oil supply passage" in the present invention) that communicates from the crankcase 40 side to the cylinder head 43 side, and a first oil passage 91A in the cylinder head 43 that is connected to the internal oil supply passage 91 and leads to the periphery of the camshaft 61 of the valve train 60. Oil circulating in the internal combustion engine 4 is supplied to the internal oil supply passage 91 in the cylinder block from an oil pump (not shown) provided in the crankcase 40, and the oil flows inside the cylinder block 42 forward in the direction of the cylinder axis X toward the cylinder head 43.

[0031] The supply oil passage 91 in the cylinder block and the first oil passage 91A in the cylinder head 43 are connected at mating surfaces 42b, 43b of the cylinder block 42 and the cylinder head 43, on a side closer to the intake valve port 66 of the intake port 45 than the exhaust valve port 67 of the exhaust port 46 (see FIG. 4). A second oil passage 91B formed along the mating surface 42b (the mating surface of the cylinder block 42 that meets the cylinder head 43) and the mating surface 43b (the mating surface of the cylinder head 43 that meets the cylinder block 42) branches off from this connection, and this connection constitutes a branch portion 92 of the first oil passage 91A and the second oil passage 91B.

[0032] In this embodiment, the second oil passage 91B is formed so that its position is aligned with both the mating surface 42b of the cylinder block 42 and the mating surface 43b of the cylinder head 43, and each has a groove-shaped oil passage cross section, which together form a hole-shaped oil passage. However, a groove-shaped oil passage may be formed in either the mating surface 42b of the cylinder block 42 or the mating surface 43b of the cylinder head 43, and the other mating surface may be brought together to form a hole-shaped oil passage.

[0033] Furthermore, a gap 95 is provided in the cylinder block 42 between the cylinder portion 42a and the cylinder block internal oil supply passage 91 (see Figures 4 and 5), penetrating the cylinder block 42 substantially in the direction of the cylinder axis X, as shown in Figure 3. A rear opening 96 of the gap 95 in the mating surface 42c of the cylinder block 42 that faces the crankcase 40 and a front opening 97 in the mating surface 42b that faces the cylinder head 43 are closed by gaskets (not shown) on the mating surfaces 42c and 42b, respectively.

[0034] Figure 4 is a front view of the cylinder block 42, taken along the line IV-IV in Figure 3. The small black arrows in Figure 4 schematically indicate the oil flow. A cylinder section 42a opens approximately in the center of the mating surface 42b of the cylinder block 42, which meets the cylinder head 43. Four through-holes 48 parallel to the cylinder axis X are formed around the cylinder section 42a on a concentric circle Y around the cylinder axis X. The cylinder head 43, which connects to the mating surface 42b, also has four through-holes 48 parallel to the cylinder axis X at the same positions. The tips of stud bolts 49 inserted from the front of the cylinder head 43 pass through the through-holes 48 in the cylinder head 43 and cylinder block 42 and screw into the crankcase 40, fastening the cylinder head 43 and cylinder block 42 to the crankcase 40.

[0035] The cam chain chamber 63 opens to the left of the cylinder section 42a, and a hydraulic tensioner 82 of a cam chain tensioner mechanism 80 is attached to the top of the cylinder block 42, facing the top edge of the cam chain chamber 63. In Figure 4, the positions of the intake valve orifices 66 of the intake ports 45 and the exhaust valve orifices 67 of the exhaust ports 46, which open to the combustion chamber ceiling portion 65a of the cylinder head 43 attached to the cylinder block 42, are indicated by imaginary lines (two-dot chain lines) within the cylinder section 42a.

[0036] 4, the cylinder block oil supply passage 91, which opens into the mating surface 42b of the cylinder block 42, is located outside the concentric circle Y that connects the through holes 48, and in this embodiment, outside the through holes 48 and the stud bolts 49 inserted therein, and is connected to a branch portion 92. Therefore, oil is supplied to the branch portion 92 at a position away from the cylinder portion 42a and outside the through holes 48 and stud bolts 49 of the cylinder block 42, so that relatively low-temperature oil can be sent to the first oil passage 91A and the second oil passage 91B and supplied to the vicinity of the intake valve port 66 and the camshaft 61. This reduces the intake air temperature and suppresses knocking.

[0037] The second oil passage 91B branching off at the branch point 92 is formed along the concentric circle Y on the mating surfaces 42b, 43b on a side closer to the intake valve orifice 66 of the intake port 45 than the exhaust valve orifice 67 of the exhaust port 46 (see FIG. 4 ), and extends leftward. The oil flows toward the rear of the cylinder block 42 near the hydraulic tensioner 82 of the cam chain tensioner mechanism 80 and reaches the hydraulic tensioner 82. Therefore, oil passing through the second oil passage 91B cools the intake valve orifice 66 side, suppressing the intake air temperature and preventing knocking. As shown in FIG. 4 , in this embodiment, a portion of the second oil passage 91B passes through the concentric circle Y and is located inside the concentric circle Y, passing through a position close to the intake valve orifice 66. By positioning the second oil passage 91B as close as possible to the intake valve orifice 66, the increase in intake air temperature can be further suppressed, thereby suppressing knocking.

[0038] 3, a front opening 97 is provided in the mating surface 42b of the cylinder block 42, positioned between the cylinder portion 42a and the cylinder block internal oil supply passage 91, as shown in FIG. 4. In this embodiment, the front opening 97 is further positioned between the stud bolt 49 and the cylinder block internal oil supply passage 91.

[0039] FIG. 5 is a rear view of the cylinder block 42, taken along the line V-V in FIG. 3 . The small black arrows in FIG. 5 schematically indicate the oil flow. The cylinder section 42a opens approximately in the center of the mating surface 42c of the cylinder block 42 that interfaces with the crankcase 40. Four through-holes 48 are formed around the cylinder section 42a in concentric circles around the cylinder axis X, parallel to the cylinder axis X. As shown in FIG. 5 , the gap 95 described in FIG. 3 has a rear opening 96 on the mating surface 42c that interfaces with the crankcase 40, positioned between the cylinder section 42a and the cylinder block oil supply passage 91. Furthermore, in this embodiment, the rear opening 96 is positioned between the stud bolt 49 and the cylinder block oil supply passage 91.

[0040] Therefore, the front opening 97 and rear opening 96 of the gap 95 are located between the cylinder portion 42a and the cylinder block internal supply oil passage 91, and the gap 95 is provided between the cylinder portion 42a and the cylinder block internal supply oil passage 91 as described above. This means that the gap 95, which serves as a heat-insulating space, is provided between the cylinder portion 42a that constitutes the combustion chamber 65 and the cylinder block internal supply oil passage 91, thereby preventing the oil in the cylinder block internal supply oil passage 91 from rising in temperature. Furthermore, in this embodiment, the front opening 97 and rear opening 96 of the gap 95 are located between the stud bolt 49 and the cylinder block internal supply oil passage 91, and the gap 95 is provided between the stud bolt 49 and the cylinder block internal supply oil passage 91 as described above. This allows heat generated in the combustion chamber 65 to be released to the crankcase 40 by the stud bolt 49. This results in a structure in which the oil in the cylinder block internal supply oil passage 91 is less likely to rise in temperature.

[0041] 4 is larger than the rear opening 96 shown in FIG. 5. That is, the cross-sectional area of ​​the gap 95 perpendicular to the cylinder axis X increases from the crankcase 40 side toward the cylinder head 43 side in the cylinder block 42. As shown in FIGS. 3 and 6, the gap 95 has a tapered through-hole shape that widens from the crankcase 40 side toward the cylinder head 43 side in the cylinder block 42. Therefore, the thermal insulation provided by the gap 95 increases as the gap approaches the combustion chamber 65, which is formed on the cylinder head 43 side of the cylinder portion 42a and has a large amount of heat, so the oil in the cylinder block oil supply passage 91 is less likely to rise in temperature.

[0042] 4, at the mating surface 42b of the cylinder block 42 against the cylinder head 43, the front opening 97 of the gap 95 opens larger in the limited area of ​​the mating surface 42b, and therefore has a substantially triangular cross-section with three sides that follow the outer edge 42ba of the mating surface, the through hole 48 of the stud bolt 49, and the second oil passage 91B that branches off from the cylinder block internal oil supply passage 91 at a branch portion 92. Therefore, the second oil passage 90B is disposed near the branch portion 92 and extends in an extending direction W that moves away from the branch portion 92 in the crankshaft direction Z or further away from the cylinder axis X so that one side 97a of the front opening 97 that follows the second oil passage 91B protrudes outward to increase the cross-sectional area of ​​the front opening 97.

[0043] Therefore, the second oil passage 91B from the branching portion 92 to the hydraulic tensioner 82 can be formed so as to be farther away from the cylinder portion 42a and the stud bolt 49 near the branching portion 92, and one side 97a of the front opening 97 along the second oil passage 91B can be formed so as to protrude further outward, which increases the cross-sectional area of ​​the gap 95 at the mating surfaces 42b, 43b of the cylinder block 42 and the cylinder head 43 and increases the volume of the gap 95, improving the heat insulation effect and resulting in a structure in which the oil in the cylinder block supply passage 91 is less likely to rise in temperature. In addition, because the branching portion 92 is located above the second oil passage 91B, it is possible to prevent air bubbles in the engine oil generated in the cylinder block supply passage 91 from flowing into the second oil passage 91B.

[0044] As shown in Figure 5, at the mating surface 42c of the cylinder block 42 where it meets the crankcase 40, the upstream end 91a of an internal cylinder block oil supply passage 91 that passes through the cylinder block 42 is connected to a mating surface oil supply passage 91C that faces downward along the side of the cylinder portion 42a opposite the cam chain chamber 63. The mating surface oil supply passage 91C is connected at its lower end to an oil passage 90 from an oil pump (not shown) provided in the crankcase 40 (see Figure 6), and receives a supply of oil from the oil pump. Note that while the mating surface oil supply passage 91C is shown as a groove provided on the cylinder block 42 side, it may also be a groove provided on the crankcase 40 side, or both may be formed together.

[0045] As with the above-described front opening 97, the cross-sectional area of ​​the rear opening 96 of the gap 95 can be enlarged, so that the mating surface oil supply passage 91C is arranged to extend from the upstream end 91a of the cylinder block oil supply passage 91 in the vicinity of the upstream end 91a in an extension direction V that is perpendicular to the crankshaft direction Z or further away from the cylinder axis X.

[0046] 5, the cylinder block oil supply passage 91 is located above the cylinder section 42a, and the mating surface oil supply passage 91C connected to it faces downward, with the oil feed portion 93 located below. That is, the oil supply destination through the first oil passage 91A connected to the cylinder block oil supply passage 91 at a branch portion 92 is located above because oil drips, and the intake valve orifice 66 to be cooled through the second oil passage 91B connected to the branch portion 92 is located above, so the cylinder block oil supply passage 91 and the branch portion 92 are located above. On the other hand, the oil passage 90 that supplies oil from the oil pan 47 at the bottom of the crankcase 40 by the oil pump is located below, so the oil feed portion 93 is located below, and the mating surface oil supply passage 91C extends upward from the oil feed portion 93 and connects to the upstream end 91a of the cylinder block oil supply passage 91.

[0047] Figure 6 is a right side cross-sectional view taken along the line VI-VI in Figures 3 and 4, passing through an oil supply passage 91 in the cylinder block of the internal combustion engine 4. Small black arrows in Figure 6 schematically indicate the flow of oil. Oil from the oil pan 47 is supplied to the oil supply passage 91 in the cylinder block from an oil passage 90 extending from an oil pump (not shown) in the crankcase 40 via a mating surface supply oil passage 91C, from which a second oil passage 91B branches at a branch point 92, and a first oil passage 91A is disposed forward of the cylinder head 43 toward the camshaft 61 of the valve train 60.

[0048] The cylinder block of the internal combustion engine of this embodiment is configured as described above and therefore has the following features: In the internal combustion engine 4, the crankshaft 41 is rotatably supported in the crankcase 40, the cylinder block 42 forming the cylinder portion 42a is connected to the crankcase 40, the cylinder head 43 connected to the cylinder block 42 has an intake port 45 and an exhaust port 46 formed therein and is equipped with a valve train 60, and the transmission member 62 interlocks the crankshaft 41 and the valve train 60. The cylinder block 42 is provided with an internal cylinder block supply oil passage 91 that communicates from the crankcase 40 side to the cylinder head 43 side, and a gap 95 is provided between the cylinder portion 42a formed in the cylinder block 42 and the internal cylinder block supply oil passage 91. Because the gap 95 serving as an insulating space is provided between the cylinder portion 42a forming the combustion chamber 65 and the internal cylinder block supply oil passage 91, it is possible to prevent the temperature of the oil in the internal cylinder block supply oil passage 91 from increasing due to the heat of the combustion chamber 65, which ultimately contributes to energy efficiency.

[0049] The gap 95 is provided between the stud bolts 49, which are inserted through the cylinder block 42 and fasten the cylinder head 43 and cylinder block 42 to the crankcase 40, and the cylinder block oil supply passage 91. Therefore, the heat generated in the combustion chamber 65 can be released to the crankcase 40 by the stud bolts 49, and the oil in the cylinder block oil supply passage 91 is unlikely to rise in temperature.

[0050] The cross-sectional area of ​​the gap 95, perpendicular to the cylinder axis X, increases from the crankcase 40 side toward the cylinder head 43 side in the cylinder block 42. In this way, the gap 95 is made larger as it approaches the combustion chamber 65, which is formed on the cylinder head 43 side of the cylinder portion 42a and has a large amount of heat, so the oil in the cylinder block oil supply passage 91 is less likely to rise in temperature.

[0051] The cylinder block 42 is provided with a hydraulic tensioner 82 for maintaining the tension of the transmission member 62, and an internal supply oil passage 91 of the cylinder block is connected to a branch portion 92 at the mating surfaces 42b, 43b of the cylinder block 42 and cylinder head 43. The branch portion 92 branches into a first oil passage 91A formed in the cylinder head 43 for supplying oil to the valve train 60, and a second oil passage 91B formed in the mating surfaces 42b, 43b for supplying oil to the hydraulic tensioner 82. The second oil passage 91B is disposed to extend from the branch portion 92 near the branch portion in an extension direction W that extends away from the cylinder axis X in the crankshaft direction Z or further away. As a result, the second oil passage 91B from the branching portion 92 to the hydraulic tensioner 82 can be formed farther away from the cylinder portion 42a and the stud bolt 49 near the branching portion 92, which increases the cross-sectional area of ​​the gap 95 at the mating surfaces 42b, 43b of the cylinder block 42 and the cylinder head 43, and increases the volume of the gap 95, improving the heat insulation effect. This results in a structure in which the oil in the cylinder block oil supply passage 91 does not easily rise in temperature.

[0052] Although one embodiment of the present invention has been described above, the present invention is not limited thereto and may take various forms within the scope of the claims. For example, the vehicle on which the engine is mounted is not limited to a scooter-type motorcycle as shown in the embodiment, the internal combustion engine is not limited to one provided in a swing-type power unit as shown in the embodiment, but may be an internal combustion engine fixed to a body frame, and while the left and right, front and rear have been described according to the illustrations for convenience of explanation, they may be arranged in a reversed left-right configuration, for example.

[0053] 1...Motorcycle, 2...Vehicle frame, 3...Power unit (swing type power unit), 4...Internal combustion engine, 40...Crankcase, 41...Crankshaft, 41a...Drive sprocket, 42...Cylinder block, 42a...Cylinder portion, 42b...Mating surface (mating surface of cylinder block 42 with cylinder head 43), 42c...Mating surface (mating surface of cylinder block 42 with crankcase 40), 43...Cylinder head, 43b...Mating surface (mating surface of cylinder head 43 with cylinder block 42), 45...Intake port, 46...Exhaust port, 47...Oil pan, 48...Through hole, 49...Stud bolt, 6 0...valve train, 61...camshaft, 61a...driven sprocket, 62...cam chain ("transmission member" in the present invention), 63...cam chain chamber, 65...combustion chamber, 65a...combustion chamber ceiling surface, 66...intake valve port, 67...exhaust valve port, 80...cam chain tensioner mechanism, 81...tensioner slipper, 82...hydraulic tensioner, 90...oil passage, 91...cylinder block internal oil supply passage ("oil supply passage" in the present invention), 91A...first oil passage, 91B...second oil passage, 91C...mating surface oil supply passage, 92...branch portion, 93...oil supply portion, 95...gap, 96...rear opening, 97...front opening, X...cylinder axis, Y...concentric circle, Z...crankshaft direction, W...extension direction

Claims

1. A crankcase (40) in which a crankshaft (41) is rotatably supported; a cylinder block (42) connected to the crankcase (40) and forming a cylinder portion (42a); an internal combustion engine (4) including a cylinder head (43) connected to the cylinder block (42), in which an intake port (45) and an exhaust port (46) are formed, and which is equipped with a valve mechanism (60), The cylinder block (43) is provided with an oil supply passage (91) communicating from the crankcase (40) side to the cylinder head (43) side, Oil circulating through the internal combustion engine (4) is supplied to the oil supply passage (91), a gap (95) is provided between a cylinder portion (42a) formed in the cylinder block (42) and the oil supply passage (91), and the gap (95) is provided between a stud bolt (49) that is inserted through the cylinder block (42) and fastens the cylinder head (43) and the cylinder block (42) to the crankcase (40), and the oil supply passage (91) that is located farther outward from the cylinder portion (42a) than the stud bolt (49).

2. (delete)

3. 2. The cylinder block of an internal combustion engine according to claim 1, wherein the gap (95) has a cross-sectional area perpendicular to the cylinder axis (X) that increases from a crankcase (40) side to a cylinder head (43) side in the cylinder block (42).

4. The cylinder block (42) is provided with a hydraulic tensioner (82) for maintaining tension of a transmission member (62) that links the crankshaft (41) and the valve mechanism (60), the supply oil passage (91) is connected to a branch portion (92) that branches into a first oil passage (91A) formed in the cylinder head (43) and that supplies oil to the valve mechanism (60) at a mating surface (42b, 43b) between the cylinder block (42) and the cylinder head (43) and into a second oil passage (91B) formed in the mating surface (42b, 43b) and that supplies oil to the hydraulic tensioner (82); 2. The cylinder block of an internal combustion engine according to claim 1, wherein the second oil passage (91B) is disposed in a vicinity of the branching portion (92) so as to extend in an extension direction (W) away from the cylinder axis (X) in the crankshaft direction (Z) or further away from the branching portion (92).