Cylinder block of an 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

[Technical Field]

[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. [Background technology]

[0002] In recent years, research has been conducted into improving the energy efficiency of internal combustion engines, which contributes to energy efficiency, in order to ensure that more people have access to affordable, reliable, sustainable and advanced energy. In order to improve the thermal efficiency of an internal combustion engine, structures in which a surface treatment is applied to provide a heat insulating effect around the combustion chamber of the internal combustion engine are disclosed, for example, in Patent Documents 1 to 3. 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 burden in terms of cost and process. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2009-243355 (Figs. 1 and 2) [Patent Document 2] Japanese Patent Publication No. 2015-031226 (Figs. 1 to 3) [Patent Document 3] WO2014 / 024494 (Figs. 1 to 5) Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, in this technology relating to improving the energy efficiency of an internal combustion engine, it is an issue to suppress an increase in the temperature of oil in the oil supply passage of the cylinder block due to heat in the combustion chamber. In order to solve the above problems, the present invention aims to provide a cylinder block for an internal combustion engine that can prevent the oil in the oil supply passage of the cylinder block from rising in temperature due to the heat of the combustion chamber, without the need for surface treatment to provide an insulating effect around the combustion chamber of the internal combustion engine, and ultimately contributes to energy efficiency. [Means for solving the problem]

[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 the crankshaft is rotatably supported; a cylinder block connected to the crankcase and forming a cylinder section; a cylinder head connected to the cylinder block, having an intake port and an exhaust port formed therein, and having a valve mechanism, The cylinder block is provided with an oil supply passage that communicates from the crankcase side to the cylinder head side, The oil supply passage is supplied with oil circulating through the internal combustion engine, The cylinder block for an internal combustion engine is characterized in that a gap is provided between a cylinder portion formed in the cylinder block and the oil supply passage.

[0006] According to the above configuration, Since a gap that acts as an insulating space is provided between the cylinder portion that constitutes the combustion chamber and the supply oil passage, it is possible to prevent the oil in the supply oil passage from rising in temperature due to the heat of the combustion chamber, which ultimately contributes 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. Therefore, the heat generated in the combustion chamber can be dissipated to the crankcase by the stud bolt, making it possible to create 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 is made larger as it approaches the combustion chamber, which is formed on the cylinder head side of the cylinder portion and has a large amount of heat, so it is possible to achieve a structure in which the temperature of the oil in the supply oil passage does not easily rise.

[0009] According to a preferred embodiment of the present invention, a hydraulic tensioner is provided in the cylinder block to maintain tension on a transmission member that links the crankshaft and the valve mechanism; the oil supply passage is connected to a branching portion at a mating surface between the cylinder block and the cylinder head, the branching portion being 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, The second oil passage is disposed in the vicinity of the branching portion and extends from the branching portion in an extending direction away from the cylinder axis in the crankshaft direction or further away. This allows the second oil passage from the branching point to the hydraulic tensioner to be positioned farther away from the cylinder and stud bolts near the branching point, increasing the cross-sectional area of ​​the gap at the mating surface between the cylinder block and cylinder head, and increasing the volume of the gap to improve the heat insulation effect, resulting in a structure in which the oil in the oil supply passage is less likely to heat up. [Effects of the Invention]

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

[0011] [Figure 1] 1 is a schematic right side view of a motorcycle equipped with a power unit including a cylinder block of an internal combustion engine according to an embodiment of the present invention. [Figure 2] 2 is a right side view of the internal combustion engine of the power unit of FIG. 1, from the crankcase to the head cover. [Figure 3] FIG. 3 is a top cross-sectional view of the internal combustion engine taken along the line III-III in FIG. 2. [Figure 4] 4 is a front view of the cylinder block taken along the line IV-IV in FIG. 3. [Figure 5] FIG. 4 is a rear view of the cylinder block as seen from the arrow VV in FIG. 3. [Figure 6] 6 is a right side cross-sectional view taken along the arrows VI-VI in FIG. 3 and FIG. 4 and passing through an oil supply passage in a cylinder block of the internal combustion engine. DETAILED DESCRIPTION OF THE INVENTION

[0012] A cylinder block of an internal combustion engine according to one embodiment of the present invention will be described with reference to FIGS. In the description and claims of this specification, the directions of front, back, left, right, up, down, etc. are based on the directions of a vehicle equipped with a power unit having an internal combustion engine according to this embodiment. Specifically, the vehicle in this embodiment is a scooter-type motorcycle (hereinafter simply referred to as "motorcycle"). In addition, in the figure, the arrow FR indicates the front of the vehicle, LH indicates the left side of the vehicle, RH indicates the right side of the vehicle, and UP indicates the top of the vehicle.

[0013] FIG. 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. The motorcycle 1 has a front body 1F and a rear body 1R connected via a low floor portion 1C, and a body frame 2 forming the skeleton of the body is generally composed of a down tube 21 and a main pipe 22. That is, a down tube 21 extends downward from a head pipe 20 at the front part 1F of the vehicle body, bends horizontally at its lower end and extends rearward below the floor part 1C, and is connected at its rear end to a pair of left and right main pipes 22, which pass through a rising part 22a that rises diagonally rearward from the connecting part, bends approximately horizontally at a predetermined height, and extends rearward.

[0014] The main pipe 22 supports a fuel tank and storage box (not shown), and above that, a bracket 23 protrudes from the rising portion 22a of the passenger-in pipe 22. A power unit side bracket 33 is attached to the bracket 23 via a link member 24, and the swing-type power unit (hereinafter simply referred to as the "power unit") 3 is connected and supported so that it can swing up and down together with the rear wheel 15. That is, 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, and the front part of the unit case 30 forms a crankcase 40 of the internal combustion engine 4. The internal combustion engine 4 rotatably supports a crankshaft 41, whose axis 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 mounted in the power unit 3 in a position where the cylinder block 42, cylinder head 43, and head cover 44 are 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 portion 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 unit 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 arranged on the 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 and extends rearward along the right side of the vehicle, connecting 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 part 1F of the vehicle body is covered at the front and rear by a front cover 17a and a rear cover 17b, and the center part of the handlebar 12 is covered by a handlebar cover 17c. A step plate 17d is stretched on the floor portion 1C, and lower side covers 17e are extended downward along the left and right side edges of the 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] FIG. 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. FIG. The internal combustion engine 4 of this embodiment is a forced air-cooled type, and the right side of the crankcase 40 is covered with a fan cover 70. The fan cover 70 has a cooling air intake window 71 opened around the axis of the crankshaft 41, and a rotating fan (not shown) is provided inside the cooling air intake window 71 concentrically with the crankshaft 41. The cylinder block 42 and the cylinder head 43 are covered by a shroud 72 indicated by a two-dot chain line, and the shroud 72 is in communication with a fan cover 70. Outside cooling air is taken in through a cooling air intake window 71 by a rotary fan that rotates together with the crankshaft 41, and is forced into the shroud 72 via the fan cover 70, where it cools the cylinder block 42 and the cylinder head 43 before being discharged.

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

[0022] The crankshaft 41 is rotated clockwise in FIG. 2 by the back and forth movement of a piston (not shown) that slides within a cylinder portion 42a (see FIG. 4) that is provided in the cylinder block 42 and oriented approximately in the front-to-rear direction. At the front end of the cylinder head 43, a camshaft 61 is supported between 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 part of the cylinder head 43 facing the cylinder section 42a forms the combustion chamber ceiling surface 65a (see Figure 4). The cylinder head 43 is provided with intake valves and exhaust valves (not shown) for controlling the intake and exhaust of air into the combustion chamber 65, and the lift amount and opening / closing timing of the intake valve and exhaust valve are each controlled by a cam surface provided on the camshaft 61 of the valve train 60 in accordance with the rotation of the camshaft 61.

[0024] That is, the valve mechanism 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 the illustration of Figure 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 timing with respect to the combustion stroke of the internal combustion engine 4, an intake valve opening 66 of the intake port 45 that opens to the combustion chamber ceiling surface 65a, and an exhaust valve opening 67 of the exhaust port 46 (see Figure 4).

[0025] In order for the intake valves and exhaust valves to open and close properly at the predetermined timing, the tension of the cam chain 62 must always be maintained at an appropriate level. However, vibrations may 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 due to 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 provide 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] On the other hand, an oil pan 47 (see FIG. 5) is provided below the crankcase 40. In addition, an oil pump (not shown) driven by the power of the crankshaft 41 is provided inside the crankcase 40. When the oil pump is driven by the crankshaft 41, engine oil (hereinafter, also in the claims, simply referred to as "oil") stored in the oil pan 47 is sucked in through a strainer (not shown) and sent from the oil pump to various parts of the internal combustion engine 1 through multiple oil passages. In addition, reference numeral 57 in FIG. 2 denotes an O2 sensor for exhaust gas. Also, reference numeral 33 denotes a power unit side bracket for the upper link support structure of the power unit 3 described above.

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

[0030] Therefore, as shown in Figure 3, the cylinder block 41 is provided with an internal oil supply passage 91 (the "oil supply passage" in this 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 toward the periphery of the camshaft 61 of the valve train 60. Oil circulating through the internal combustion engine 4 is supplied to the cylinder block oil supply passage 91 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 the mating surfaces 42b, 43b of the cylinder block 42 and the cylinder head 43 on the 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 Figure 4). From this connection, a second oil passage 91B formed along mating surface 42b (the mating surface of cylinder block 42 against cylinder head 43) and mating surface 43b (the mating surface of cylinder head 43 against cylinder block 42) branches off, and this connection constitutes a branching 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 it is aligned with both the mating surface 42b of the cylinder block 42 and the mating surface 43b of the cylinder head 43, each having a groove-shaped oil passage cross section, and together they form a hole-shaped oil passage. However, a groove-like oil passage may be formed in one of 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-like oil passage.

[0033] In addition, a gap 95 is provided in the cylinder block 42 between the cylinder portion 42a and the cylinder block internal supply oil passage 91 (see Figures 4 and 5), penetrating the cylinder block 42 in the direction of the cylinder axis X as shown in Figure 3. A rear opening 96 of the gap 95 at the mating surface 42c of the cylinder block 42 that faces the crankcase 40 and a front opening 97 at 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] Fig. 4 is a front view of the cylinder block 42 taken along the line IV-IV in Fig. 3. Small black arrows in Fig. 4 schematically indicate the flow of oil. A cylinder portion 42a opens at approximately the center of a mating surface 42b of the cylinder block 42 that faces the cylinder head 43, and four through holes 48 parallel to the cylinder axis X are formed around the cylinder portion 42a on a concentric circle Y about the cylinder axis X. Four through holes 48 are drilled in the cylinder head 43, which is connected to the mating surface 42b, at the same positions and parallel to the cylinder axis X. The tips of stud bolts 49, which are inserted from the front of the cylinder head 43, pass through the through holes 48 in the cylinder head 43 and the cylinder block 42 and are screwed into the crankcase 40, fastening and fixing the cylinder head 43 and the cylinder block 42 to the crankcase 40.

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

[0036] As shown in FIG. 4, an oil supply passage 91 in the cylinder block that opens into the mating surface 42b of the cylinder block 42 is provided at a position 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 that are inserted therethrough, 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-hole 48 and the stud bolt 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 makes it possible to suppress the intake temperature and thereby suppress knocking.

[0037] Further, the second oil passage 91B branching off at the branch portion 92 is formed along the concentric circle Y on a side of the mating surfaces 42b, 43b that is 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), and extends leftward, toward the rear of the interior of the cylinder block 42 near the hydraulic tensioner 82 of the cam chain tensioner mechanism 80, and then leads to the hydraulic tensioner 82. Therefore, the oil passing through the second oil passage 91B cools the intake valve port 66 side, suppresses the intake temperature, and prevents knocking. Furthermore, as shown in FIG. 4, in this embodiment, a portion of the second oil passage 91B passes through the concentric circle Y and is provided inside the concentric circle Y, passing through a position close to the intake valve port 66. By locating the second oil passage 91B as close as possible to the intake valve port 66, the temperature rise of the intake air can be further suppressed, and knocking can be suppressed.

[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 supply oil passage 91 in the cylinder block, as shown in FIG. Furthermore, in this embodiment, the front opening 97 is located between the stud bolt 49 and the oil supply passage 91 in the cylinder block.

[0039] Fig. 5 is a rear view of the cylinder block 42 as seen from the arrow VV in Fig. 3. Small black arrows in Fig. 5 schematically show the flow of oil. A cylinder portion 42a opens at approximately the center of a mating surface 42c of the cylinder block 42 that faces the crankcase 40, and four through holes 48 parallel to the cylinder axis X are formed around the cylinder portion 42a on concentric circles about 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 faces the crankcase 40, positioned between the cylinder portion 42a and the supply oil passage 91 in the cylinder block. Furthermore, in this embodiment, the rear opening 96 is located between the stud bolt 49 and the oil supply passage 91 in the cylinder block.

[0040] Therefore, the front opening 97 and the rear opening 96 of the gap 95 are located between the cylinder portion 42a and the cylinder block internal oil supply passage 91, and the gap 95 is provided between the cylinder portion 42a and the cylinder block internal oil supply passage 91 as described above. A gap 95 that serves as an insulating space is provided between the cylinder portion 42a that constitutes the combustion chamber 65 and the cylinder block internal supply oil passage 91, which prevents the oil in the cylinder block internal supply oil passage 91 from rising in temperature. Furthermore, in this embodiment, the front opening 97 and the rear opening 96 of the gap 95 are located between the stud bolt 49 and the cylinder block internal oil supply passage 91, and as described above, the gap 95 is provided between the stud bolt 49 and the cylinder block internal oil supply passage 91. The heat generated in the combustion chamber 65 can be released to the crankcase 40 by the stud bolt 49. Therefore, the oil in the cylinder block oil supply passage 91 is unlikely 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 is in the form of a tapered through-hole in the cylinder block 42, widening from the crankcase 40 side toward the cylinder head 43 side. Therefore, as the cylinder approaches the combustion chamber 65, which has a large amount of heat and is formed on the cylinder head 43 side of the cylinder section 42a, the insulating properties of the gap 95 become greater, resulting in a structure in which the oil in the supply oil passage 91 within the cylinder block does not easily rise in temperature.

[0042] As shown in FIG. 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 at the mating surface 42b, which has a limited area, and therefore has a substantially triangular cross section with three sides that are aligned with 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 internal oil supply passage 91 at the branching portion 92. Therefore, the second oil passage 90B is arranged to extend in an extension direction W away from the branching portion 92 in the crankshaft direction Z or further away from the cylinder axis X near the branching portion 92 so that one side 97a of the front opening 97 along the second oil passage 91B can protrude further 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 to protrude further outward.As a result, the cross-sectional area of ​​the gap 95 at the mating surfaces 42b, 43b of the cylinder block 42 and the cylinder head 43 can be increased, the capacity of the gap 95 can be increased, and the insulating effect can be improved, resulting in a structure in which the oil in the supply oil passage 91 within the cylinder block is less likely to rise in temperature. Furthermore, since the branch portion 92 is disposed above the second oil passage 91B, it is possible to prevent air bubbles in the engine oil generated in the cylinder block supply oil passage 91 from flowing into the second oil passage 91B.

[0044] As shown in FIG. 5, at the mating surface 42c of the cylinder block 42 against the crankcase 40, the upstream end 91a of the cylinder block internal oil supply passage 91 that passes through the cylinder block 42 is connected to a mating surface supply passage 91C that is provided downward along the side of the cylinder portion 42a opposite the cam chain chamber 63. The mating surface supply oil passage 91C is connected at its lower end to an oil passage 90 extending from an oil pump (not shown) provided inside the crankcase 40 (see FIG. 6), and receives a supply of oil from the oil pump. Although 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 by mating.

[0045] As with the above-mentioned front opening 97, the cross-sectional area of ​​the rear opening 96 of the gap 95 can be enlarged, so that the mating surface supply oil passage 91C is arranged to extend from the upstream end 91a of the cylinder block supply oil 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] As shown in FIG. 5, the cylinder block oil supply passage 91 is located above the cylinder section 42a, the mating surface oil supply passage 91C connected to it is arranged facing downward, and the oil supply section 93 is located on the lower side, for the following reasons. In other words, the oil supply destination through the first oil passage 91A, which is connected to the cylinder block oil supply passage 91 at the branching portion 92, is located at the top due to oil dripping, and the intake valve port 66, which is the object to be cooled by the second oil passage 91B, which is connected at the branching portion 92, is located above, so the cylinder block oil supply passage 91 and the branching portion 92 are located above. On the other hand, since 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 at the bottom, the oil supply part 93 is also located at the bottom, and the mating surface supply oil passage 91C extends upward from the oil supply part 93 and connects to the upstream end 91a of the supply oil passage 91 in the cylinder block.

[0047] Fig. 6 is a right side cross-sectional view taken along the line VI-VI in Fig. 3 and Fig. 4, passing through the supply oil passage 91 in the cylinder block of the internal combustion engine 4. Small black arrows in Fig. 6 schematically show 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) inside the crankcase 40 via a mating surface supply oil passage 91C, and a second oil passage 91B branches off at a branch point 92, with the first oil passage 91A being arranged 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 has the following features. That is, in an internal combustion engine 4 in which a crankshaft 41 is rotatably supported in a crankcase 40, a cylinder block 42 forming a cylinder portion 42a is connected to the crankcase 40, a 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 mechanism 60, and a transmission member 62 that links the crankshaft 41 and the valve mechanism 60, a cylinder block 42 is provided with an internal 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 supply oil passage 91. In this way, a gap 95 that serves as an insulating space is provided between the cylinder portion 42a that constitutes the combustion chamber 65 and the cylinder block oil supply passage 91, which makes it possible to prevent the oil in the cylinder block oil supply passage 91 from rising in temperature due to the heat of the combustion chamber 65, thereby contributing to energy efficiency.

[0049] The gap 95 is provided between the 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 within the cylinder block. Therefore, the heat generated in the combustion chamber 65 can be released to the crankcase 40 by the stud bolt 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, which is perpendicular to the cylinder axis X, increases from the crankcase 40 side toward the cylinder head 43 side in the cylinder block . 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 supply oil 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 the supply oil passage 91 within the cylinder block is connected to a branching portion 92 at the mating surfaces 42b, 43b between the cylinder block 42 and the cylinder head 43, which branches into a first oil passage 91A formed in the cylinder head 43 for supplying oil to the valve mechanism 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 in the vicinity of the branch portion 92 and extends from the branch portion in an extending direction W away from the cylinder axis X in the crankshaft direction Z or further away. Therefore, 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 internal supply oil passage 91 is less likely to 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. [Explanation of symbols]

[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 section (42a); an internal combustion engine (4) including a cylinder head (43) connected to the cylinder block (42), having an intake port (45) and an exhaust port (46) formed therein, and having a valve mechanism (60), The cylinder block (43) is provided with an oil supply passage (91) that communicates from the crankcase (40) side to the cylinder head (43) side, The oil supply passage (91) is supplied with oil circulating through the internal combustion engine (4), a gap (95) is provided between a cylinder portion (42 a) 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 (42 a) than the stud bolt (49).

2. (delete)

3. 2. The cylinder block of an internal combustion engine according to claim 1, wherein 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).

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) at a mating surface (42b, 43b) between the cylinder block (42) and the cylinder head (43) that branches into a first oil passage (91A) formed in the cylinder head (43) for supplying oil to the valve mechanism (60) and a second oil passage (91B) formed in the mating surface (42b, 43b) for supplying 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 arranged to extend from the branching portion (92) in the vicinity of the branching portion (92) in an extension direction (W) away from the cylinder axis (X) in the crankshaft direction (Z) or further.

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