INTERNAL COMBUSTION ENGINE AND STRADDLED VEHICLE HAVING THE SAME

Abstract

 An internal combustion engine is provided, with which it is possible to desirably supply oil to lubricated members while reducing the machining cost. The engine includes a gasket 50 placed between a crankcase 7 and a cover 22, and gears 28 and 36 placed so that at least a part of the gears 28 and 36 is aligned with the gasket 50, as the vehicle is seen from above. A primary slit 61 and an internal slit 62 connected to the primary slit 61 are formed in the gasket 50, wherein the primary slit 61 is placed between a first mating surface 7A of the crankcase 7 and a second mating surface 22A of the cover 22 and overlaps with an oil supply hole 84, and the internal slit 62 is placed in an internal space 90 defined by the crankcase 7 and the cover 22 and placed upward of the gears 28 and 36. The gasket 50 is closed around the primary slit 61 and the internal slit 62.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

[0001] The present invention relates to an internal combustion engine and a straddled vehicle having the same.

Description of the Related Art

[0002] An internal combustion engine includes lubricated members to be lubricated with oil, such as gears, for example. A configuration has been known in the art, in which an oil passageway and an oil discharge port are formed in a case accommodating lubricated members therein in order to supply oil to the lubricated members, and oil is discharged via the discharge port toward the lubricated members.

[0003] However, this configuration has a problem in that an oil passageway and an oil discharge port need to be formed in the case by machining the case, thereby imposing an increased machining limitation and a high machining cost. Japanese Laid-Open Patent Publication No. 2011-38431 discloses a configuration in which an oil passageway is formed in a metal gasket provided between the cylinder head and the fuel pump housing member. Specifically, in a metal gasket disclosed in Japanese Laid-Open Patent Publication No. 2011-38431, a hole communicating with an oil supply passageway in a cylinder head and a slit, one end of which communicates with the hole and the other end of which is open in the longitudinal direction. Oil that flowed into the hole of the metal gasket via the oil supply passageway in the cylinder head passes through the slit of the metal gasket to be supplied to an internal space of a housing member via the open end of the slit.

SUMMARY OF THE INVENTION

[0004] It is an object of the present invention to provide an internal combustion engine, with which it is possible to desirably supply oil to lubricated members while reducing the machining cost, and to provide a straddled vehicle having the same.

[0005] This obj ect is achieved by an internal combustion engine and by a straddled vehicle as defined in the independent claims.

[0006] It has been found that in the above described conventional approach, when the housing member is fastened to the cylinder head, the gasket receives a substantial pressure from the cylinder head and the housing member. Then, the open end of the slit may be deformed and the passageway of oil may be narrowed, thereby failing to sufficiently supply oil.

[0007] An internal combustion engine of the present invention is an internal combustion engine installed on a vehicle, the internal combustion engine including: a first case including a first mating surface and an oil supply hole formed in the first mating surface; a second case including a second mating surface opposing the first mating surface, and fastened to the first case; a gasket placed between the first case and the second case; and a lubricated member placed in an internal space defined by the first case and the second case and placed so that at least a part the lubricated member is aligned with the gasket, as the vehicle is seen from above, when installed on a vehicle. A primary slit and an internal slit connected to the primary slit are formed in the gasket, wherein the primary slit is placed between the first mating surface and the second mating surface and overlaps with the oil supply hole, and the internal slit isplacedinthe internal space and placed upward of the lubricated member when installed on a vehicle; and the gasket is closed around the primary slit and the internal slit.

[0008] With the internal combustion engine described above, oil, which has been supplied between the first mating surface and the second mating surface via the oil supply hole, is guided into the internal slit through the primary slit of the gasket. Since the internal slit is placed in the internal space defined by the first case and the second case and is placed upward of the lubricated member, oil in the internal slit is supplied to the lubricated member by falling down in the internal space. With the internal combustion engine described above, there is no need to form a discharge port in the first case or the second case for discharging oil toward the lubricated member. Therefore, it is possible to reduce the machining cost. Since the gasket is closed around the primary slit and the internal slit, when the first case and the second case are fastened together, the portion of the gasket around the primary slit and the internal slit is not easily deformed. Therefore, the width of the oil passageway in the gasket, i.e., the width of the primary slit and the internal slit, is maintained, and it is possible to sufficiently supply oil to the lubricated member. Thus, with the internal combustion engine described above, it is possible to desirably supply oil to the lubricated member while reducing the machining cost.

[0009] According to a preferred embodiment of the present invention, the gasket is a paper gasket.

[0010] A paper gasket is less expensive than a metal gasket. On the other hand, a paper gasket is softer than a metal gasket, and has a property that it swells by absorbing oil. Therefore, a paper gasket is more easily deformed than a metal gasket. With the internal combustion engine described above, however, since the gasket is closed around the primary slit and the internal slit, the gasket is not easily deformed despite being a paper gasket. Thus, a paper gasket can be used. According to the above embodiment, it is possible to desirably supply oil to the lubricated member while further reducing the cost.

[0011] According to another preferred embodiment of the present invention, the first mating surface and the secondmating surface are surfaces parallel to a vertical plane when installed on a vehicle.

[0012] According to the above embodiment, oil having passed through the internal slit of the gasket falls down from both sides of the gasket. Therefore, it is possible to supply oil over a wide area from the gasket.

[0013] According to another preferred embodiment of the present invention, the gasket includes a protrusion protruding downward, the protrusion placed in the internal space and located downward of the internal slit when installed on a vehicle.

[0014] Oil, being a liquid, has a property that it easily collects at a protrusion protruding downward. According to the above embodiment, it is possible to collect oil, which has passed through the internal slit of the gasket, at the protrusion. Therefore, it is possible to desirably supply oil from the protrusion.

[0015] According to another preferred embodiment of the present invention, the gasket includes a protrusion protruding downward, the protrusion placed in the internal space and located directly upward of the lubricated member when installed on a vehicle.

[0016] According to the above embodiment, oil having passed through the internal slit of the gasket collects at the protrusion and falls down from the protrusion toward the lubricated member. Therefore, oil can be supplied directly to the lubricated member. Thus, it is possible to desirably supply oil to the lubricated member while reducing the machining cost.

[0017] According to another preferred embodiment of the present invention, the lubricated member includes a first member and a second member. The gasket includes a first protrusion protruding downward, the first protrusion placed in the internal space and located directly upward of the first member when installed on a vehicle, and a second protrusion protruding downward, the second protrusion placed in the internal space and located directly upward of the second member when installed on a vehicle.

[0018] According to the above embodiment, oil having been guided into the internal slit of the gasket can be desirably supplied to the first member and to the second member.

[0019] According to another preferred embodiment of the present invention, the lubricated member includes a gear.

[0020] According to the above embodiment, it is possible to desirably supply oil to the gear of the internal combustion engine while reducing the machining cost.

[0021] According to another preferred embodiment of the present invention, the lubricated member includes an oil pump including an oil pump gear.

[0022] According to the above embodiment, it is possible to desirably supply oil to the oil pump gear while reducing the machining cost.

[0023] According to another preferred embodiment of the present invention, oil is stored at a bottom of the first case and/or the second case when installed on a vehicle; and the oil pump gear is placed upward of a liquid surface of the oil stored at the bottom when the internal combustion engine is inoperative.

[0024] When the oil pump gear is immersed in the oil stored at the bottom of the first case and/or the second case, the oil can be stirred up as the oil pump gear rotates, and the oil pump gear can be lubricated with the stirred-up oil. However, when the oil pump gear is placed upward of the liquid surface of oil, as in the embodiment described above, oil cannot be stirred up by the oil pump gear. Thus, the advantageous effect of supplying oil to the oil pump gear through the primary slit and the internal slit of the gasket is more pronounced.

[0025] According to another preferred embodiment of the present invention, the first case is a crankcase supporting a crankshaft. The internal combustion engine further includes: a cylinder body connected to the crankcase, the cylinder body accommodating therein a piston linked to the crankshaft via a connecting rod; a cylinder head connected to the cylinder body, the cylinder head including an intake valve and an exhaust valve; and a cylinder head cover connected to the cylinder head, the cylinder head cover including a valve operating mechanism configured to operate the intake valve and the exhaust valve. An oil intake hole overlapping with the primary slit of the gasket is formed in the crankcase. An oil passageway connecting between the oil intake hole and an internal space of the cylinder head cover is formed in the crankcase, the cylinder body, the cylinder head and the cylinder head cover.

[0026] According to the above embodiment, it is possible to desirably supply oil to the lubricated member and the valve operating mechanism.

[0027] According to another preferred embodiment of the present invention, the oil intake hole is provided between the oil supply hole and the internal slit along the primary slit of the gasket.

[0028] According to the above embodiment, a part of oil having flowed into the primary slit via the oil supply hole flows into the oil intake hole, and oil not having flowed into the oil intake hole flows into the internal slit. Since oil in the primary slit is preferentially supplied to the oil intake hole, it is possible to supply a sufficient amount of oil to the valve operating mechanism in the cylinder head cover. Therefore, it is possible to desirably supply oil to the lubricated member and the valve operating mechanism.

[0029] According to another preferred embodiment of the present invention, the internal slit of the gasket is formed in a shape extending in a vertically downward direction or a diagonally downward direction when installed on a vehicle.

[0030] According to the above embodiment, since it is more likely that oil flows quickly through the internal slit under the influence of gravity, it is possible to desirably supply oil in the primary slit to the lubricated member through the internal slit.

[0031] According to another preferred embodiment of the present invention, an outline of a distal end of the internal slit of the gasket is formed in an arc shape.

[0032] According to the above embodiment, oil is unlikely to remain in the distal end of the internal slit, and it is possible to quickly supply oil to the lubricated member via the internal slit.

[0033] A straddled vehicle of the present invention includes the internal combustion engine set forth above.

[0034] Thus, it is possible to obtain a straddled vehicle with the advantageous effects set forth above.

Advantageous Effects Of Invention

[0035] According to the present invention, it is possible to provide an internal combustion engine, with which it is possible to desirably supply oil to lubricated members while reducing the machining cost, and to provide a straddled vehicle having the same.

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] 

FIG. 1 is a side view of a motorcycle according to one embodiment of the present invention.

FIG. 2 is a cross-sectional view of a power unit.

FIG. 3 is a side view of the power unit, showing a crankcase with a cover removed and showing a cylinder body, a cylinder head and a cylinder head cover partially cut away.

FIG. 4 is a cross-sectional view of the power unit taken along line IV-IV of FIG. 3.

FIG. 5 is a front view of a gasket.

FIG. 6 is a view showing how a gasket is laid on a first mating surface of the crankcase.

FIG. 7 is an enlarged cross-sectional view of a portion of the power unit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] One embodiment of the present invention will now be described with reference to the drawings. As shown in FIG. 1, a vehicle of the present embodiment is a motorcycle 1, which is an example straddled vehicle to be straddled by a passenger. Note however that the vehicle of the present invention is not limited to the motorcycle 1, but may be any other straddled vehicle to be straddled by a passenger, such as a three-wheeled vehicle, an all terrain vehicle (ATV) and a snowmobile. It may also be a vehicle other than a straddled vehicle.

[0038] The terms front, rear, left, right, up and down, as used in the description below, refer to these directions as seen from a passenger seated in a seat 4 while the motorcycle 1 is stationary in an upright position on a horizontal surface, unless specified otherwise. The designations F, Re, L, R, U and D, as used in the figures, refer to front, rear, left, right, up and down, respectively. The terms forward and rearward refer to these directions in the vehicle front-rear direction, unless specified otherwise. The terms upward and downward refer to these directions in the vehicle up-down direction. The terms leftward and rightward refer to these directions in the vehicle left-right direction. The directions as used in the following description of a power unit 3 and an internal combustion engine 5 refer to these directions with the power unit 3 installed on the motorcycle 1.

[0039] As shown in FIG. 1, the motorcycle 1 includes a vehicle body frame 2 including a head pipe 12, a power unit 3 supported on the vehicle body frame 2, a front wheel 20 and a rear wheel 30. A steering shaft 13 is rotatably supported on the head pipe 12. A handle bar 11 is fixed on an upper portion of the steering shaft 13, and a front fork 14 is fixed on a lower portion of the steering shaft 13. The front wheel 20 is attached to the front fork 14. A fuel tank 10 is placed upward of the power unit 3. The seat 4 is placed rearward of the fuel tank 10. The power unit 3 is linked to the rear wheel 30 via a transmission member such as a chain 26 (not shown in FIG. 1; see FIG. 2).

[0040] Next, a configuration of the power unit 3 will be described. As shown in FIG. 2, the power unit 3 includes an internal combustion engine 5. The power unit 3 drives the rear wheel 30 using the power from the internal combustion engine 5. In the present embodiment, the internal combustion engine 5 is a single-cylinder internal combustion engine including a single cylinder 6. Note however that the internal combustion engine 5 may be a multi-cylinder internal combustion engine including a plurality of cylinders.

[0041] The internal combustion engine 5 includes a crankcase 7, a cylinder body 8 connected to the crankcase 7, a cylinder head 9 connected to the cylinder body 8, and a cylinder head cover 15 connected to the cylinder head 9. The cylinder body 8, the cylinder head 9 and the cylinder head cover 15 extend in a diagonally upward direction from the crankcase 7. The cylinder body 8 is placed upward of the crankcase 7, the cylinder head 9 is placed upward of the cylinder body 8, and the cylinder head cover 15 is placed upward of the cylinder head 9.

[0042] A cover 17 is placed leftward of the crankcase 7, and a cover 22 is placed rightward of the crankcase 7. The cover 17 and the cover 22 are fixed to the crankcase 7. A gasket 49 is placed between the cover 17 and the crankcase 7. A gasket 50 is placed between the cover 22 and the crankcase 7. The gasket 50 is sandwiched between the cover 22 and the crankcase 7. The cover 22 and the crankcase 7 are fastened together by means of fastening members such as bolts 58. Note that the fastening members are not limited to the bolts 58, and may be screws, for example. The crankcase 7 and the cover 22 are examples of the "first case" and the "second case", respectively.

[0043] A crankshaft 18 is placed in an internal space 90 defined by the crankcase 7, the cover 17 and the cover 22. The crankshaft 18 is supported by the crankcase 7 via a bearing 39. The piston 16 is placed inside the cylinder body 8. The crankshaft 18 and the piston 16 are linked together by a connecting rod 19. A generator 21 is attached to the left end of the crankshaft 18. The generator 21 is covered by the cover 17. A gear 28 is placed at the right end of the crankshaft 18.

[0044] A main shaft 23 and a drive shaft 24 are placed in the internal space 90 of the crankcase 7. The main shaft 23 and the drive shaft 24 are placed parallel to the crankshaft 18. A plurality of transmission gears 25A are provided on the main shaft 23. Transmission gears 25B, meshing with the transmission gears 25A, are provided on the drive shaft 24. The main shaft 23, the transmission gears 25A, the transmission gears 25B and the drive shaft 24 together form a transmission 35. The left end 24a of the drive shaft 24 is placed outside the crankcase 7. A sprocket 26A is fixed at the left end 24a of the drive shaft 24, with the chain 26 wrapped around the sprocket 26A.

[0045] A clutch 40 is provided at the right end of the main shaft 40. While the clutch 40 is a wet multiple-disc clutch in the present embodiment, there is no particular limitation on the type of the clutch 40. The clutch 40 includes a clutch housing 41 rotatably supported on the main shaft 23, a clutch boss 42 non-rotatably supported on the main shaft 23, a plurality of plates 27 which are supported on the clutch housing 41 and rotate together with the clutch housing 41, a plurality of plates 29 which are supported on the clutch boss 42 and rotate together with the clutch boss 42, a pressure plate 43 configured to press the plates 27 and 29 against each other, and a spring 45 configured to urge the pressure plate 43 toward the plates 27 and 29. A gear 31, meshing with the gear 28 of the crankshaft 18, is provided in the clutch housing 41. The clutch housing 41 is configured to rotate with the crankshaft 18. The cover 22 is placed rightward of the clutch 40. The clutch 40 is covered by the cover 22.

[0046] FIG. 3 is a view showing the crankcase 7 with the cover 22 removed and showing the cylinder body 8, the cylinder head 9 and the cylinder head cover 15 partially cut away. Note that in FIG. 3, the outline of the gasket 50 is indicated by a phantom line, and the flow of oil is indicated by a one-dot-chain line. As shown in FIG. 3, the bottom of the crankcase 7 and the cover 22 forms an oil pan 32 storing oil therein. Reference sign 33 in FIG. 3 represents the liquid surface of oil when the internal combustion engine 5 is inoperative. An oil pump 34 is placed in the internal space 90 of the crankcase 7. The oil pump 34 is placed upward of the liquid surface 33 of oil when the internal combustion engine 5 is inoperative. The oil pump 34 includes an oil pump gear 36 meshing with the gear 28 provided on the crankshaft 18. The oil pump gear 36 rotates together with the crankshaft 18. The oil pump 34 is configured to be driven by the crankshaft 18. An oil filter 37 is placed in the oil pan 32.

[0047] As shown in FIG. 4, an oil path 81 connecting between the oil pan 32 and an inlet 34i of the oil pump 34, an oil path 82 connected to an outlet 34o of the oil pump 34, and an oil path 83 diverging from the oil path 82 are formed inside the crankcase 7.

[0048] The crankcase 7 has a first mating surface 7A, and the cover 22 has a secondmating surface 22A opposing the first mating surface 7A. The gasket 50 is placed between the first mating surface 7A and the second mating surface 22A. The gasket 50 is in contact with the first mating surface 7A and the second mating surface 22A. The first mating surface 7A and the second mating surface 22A are surfaces parallel to the vertical plane. An oil supply hole 84 connected to the oil path 83 is formed in the first mating surface 7A. The oil supply hole 84 has an opening facing toward the second mating surface 22A.

[0049] FIG. 5 is a front view of the gasket 50, as seen from the right side of the motorcycle 1. The gasket 50 has a slit 60, in addition to holes 51 through which bolts 58 (see FIG. 2) are inserted. The slit 60 is formed in a first surface of the gasket 50 facing the first mating surface 7A. The slit may extend from the first surface into the gasket 50, or the slit 60 may extend from the first surface through the gasket 50 to a second surface of the gasket 50 facing the secondmating surface 22A. The slit 60 is formed in the gasket 50 at a distance from an edge of the surfaces of the gasket 50. The gasket 50 may be a metal gasket, but the gasket 50 is a paper gasket containing fibers therein in the present embodiment.

[0050] FIG. 6 is a view showing how the gasket 50 is laid on the first mating surface 7A of the crankcase 7. In FIG. 6, the gasket 50 is hatched to make it easier to understand the position and the shape of the gasket 50. The hatching of FIG. 6 is not representing a cross section. In FIG. 6, the gear 31 of the clutch housing 41, the gear 28 provided on the crankshaft 18 and the oil pump gear 36 are simplified.

[0051] Reference sign 7B in FIG. 6 refers to an inner wall surface of the crankcase 7. The inner wall surface 7B is a surface that is perpendicular to, or inclined from, the first mating surface 7A. In FIG. 6, the area on the opposite side from the first mating surface 7A with respect to the inner wall surface 7B is the internal space 90 of the crankcase 7. As shown in FIG. 6, the slit 60 includes a primary slit 61 and an internal slit 62. The primary slit 61 is formed in a part of the gasket 50 that is placed between the first mating surface 7A and the second mating surface 22A, and the internal slit 62 is formed in a part of the gasket 50 that is placed in the internal space 90 defined by the crankcase 7 and the cover 22. The primary slit 61 and the internal slit 62 are connected to each other. Along the internal slit 62, both sides of the gasket 50 (the right side and the left side of the internal slit 62 in the present embodiment; the front side and the reverse side of the drawing sheet of FIG. 6) are open into the internal space 90 of the crankcase 7 and the cover 22. On the other hand, the internal slit 62 is not open in the direction perpendicular to the thickness direction of the gasket 50 (the direction perpendicular to the left-right direction in the present embodiment; the direction parallel to the drawing sheet of FIG. 6). The gasket 50 is closed around the primary slit 61 and the internal slit 62. The outline of the primary slit 61 and the internal slit 62 is formed in a closed loop. When the cover 22 is fastened to the crankcase 7 with the gasket 50 therebetween, the gasket 50 receives a substantial pressure from the first mating surface 7A and the second mating surface 22A. However, since it is closed around the primary slit 61 and the internal slit 62, the rigidity of the gasket 50 is ensured, and the gasket 50 is not easily deformed.

[0052] As shown in FIG. 3, an oil passageway 85 is formed in the cylinder body 8, the cylinder head 9 and the cylinder head cover 15. The oil passageway 85 is a passageway for supplying oil to components such as the piston 16, an intake valve 44, an exhaust valve 46, a valve operating mechanism 47 configured to operate the intake valve 44 and the exhaust valve 46, and a cam chain 48 (see FIG. 2) that links together the crankshaft 18 and the valve operating mechanism 47. Also, an oil passageway 86 for supplying oil to the clutch 40 and the transmission 35 is formed in the crankcase 7.

[0053] As shown in FIG. 6, oil intake holes 87 and 88 communicating with the oil passageway 85 and an oil intake hole 89 communicating with the oil passageway 86 are formed in the crankcase 7, in addition to the oil supply hole 84 described above. The primary slit 61 of the gasket 50 includes a portion 61A overlapping with the oil supply hole 84, a portion 61B overlapping with the oil intake hole 87, a portion 61C overlapping with the oil intake hole 88, and a portion 61D overlapping with the oil intake hole 89. Where the downstream side refers to the side toward which oil flows and the upstream side refers to the opposite side, the overlapping portions 61A, 61B, 61C and 61D are placed in this order from the upstream side toward the downstream side.

[0054] The internal slit 62 is provided between the overlapping portion 61C and the overlapping portion 61D along the primary slit 61. Although the internal slit 62 is formed in a linear shape in the present embodiment, there is no particular limitation on the shape. Although the internal slit 62 extends in a diagonally downward direction from the primary slit 61, it may extend in a vertically downward direction. The internal slit 62 may extend in a horizontal direction. Although the outline of the distal end of the internal slit 62 is formed in an arc shape in the present embodiment, the outline shape of the distal end is not limited to an arc shape.

[0055] The internal slit 62 is placed upward of the gear 28 and the oil pump gear 36. Note that the gear 28 and the oil pump gear 36 are examples of the lubricated members to which oil is supplied, and are an example of the first member and an example of the second member, respectively. As shown in FIG. 7, the gasket 50 is placed so as to be aligned with the gear 28 and the oil pump gear 36, as the vehicle is seen from above. As shown in FIG. 6, the internal slit 62 is placed directly upward of the gear 28.

[0056] The gasket 50 includes protrusions 52 and 53 protruding downward in the internal space 90 defined by the crankcase 7 and the cover 22. The protrusion 52 is placed downward of the internal slit 62. The protrusion 52 is placed upward of the gear 28, and is placed directly upward of the gear 28 in the present embodiment. The protrusion 53 is placed upward of the oil pump gear 36, and is placed directly upward of the oil pump gear 36 in the present embodiment. The protrusion 53 is placed downward of the protrusion 52. The protrusion 53 and the protrusion 52 are connected together by a portion 54 of the gasket 50 placed in the internal space 90.

[0057] Next, the oil-supplying operation of the internal combustion engine 5 will be described. As indicated by arrows in FIG. 4, oil in the oil pan 32 is sucked into the oil pump 34 and then discharged from the oil pump 34 to be passed to the oil paths 82 and 83. Oil having been passed to the oil path 83 flows into the inside of the primary slit 61 of the gasket 50 through the oil supply hole 84.

[0058] As shown in FIG. 6, a part of oil flowing through the primary slit 61 flows into the oil passageway 85 through the oil intake holes 87 and 88. Oil having flowed through the oil passageway 85 is supplied to components such as the piston 16, the intake valve 44, the exhaust valve 46, the valve operating mechanism 47 and the cam chain 48, after which the oil falls down to be collected in the oil pan 32.

[0059] Another part of oil flowing through the primary slit 61 diverges into the internal slit 62. Oil having flowed through the internal slit 62 flows out of the internal slit 62 to both sides of the gasket 50 to fall down under the influence of gravity. Since the gasket 50 includes the protrusions 52 and 53, a part of oil collects at the protrusion 52 and another part of oil collects at the protrusion 53. Oil having collected at the protrusion 52 falls down toward the gear 28. Oil having collected at the protrusion 53 falls down toward the oil pump gear 36. Thus, the gear 28 and the oil pump gear 36 are lubricated.

[0060] The remaining oil inside the primary slit 61 flows into the oil passageway 86 via the oil intake hole 89. The oil flows through the oil passageway 86, and is then supplied to the clutch 40 and the transmission 35. Thus, the clutch 40 and the transmission 35 are lubricated.

[0061] As described above, with the internal combustion engine 5 of the present embodiment, oil, which has been supplied between the first mating surface 7A of the crankcase 7 and the second mating surface 22A of the cover 22 via the oil supply hole 84 formed in the crankcase 7, is guided into the internal slit 62 through the primary slit 61 of the gasket 50. Since the internal slit 62 is placed in the internal space 90 defined by the crankcase 7 and the cover 22 and is placed upward of the gear 28 and the oil pump gear 36, oil in the internal slit 62 is supplied to the gear 28 and the oil pump gear 36 by falling down therefrom. With the internal combustion engine 5 of the present embodiment, there is no need to form a discharge port in the crankcase 7 and the cover 22 for discharging oil toward the gear 28 or the oil pump gear 36. Therefore, it is possible to reduce the machining cost. Since the gasket 50 is closed around the primary slit 61 and the internal slit 62, when the cover 22 is fastened to the crankcase 7 by the bolt 58, the portion around the primary slit 61 and the internal slit 62 of the gasket 50 is not easily deformed. Therefore, the width of the oil passageway in the gasket 50, i. e. , the width of the primary slit 61 and the internal slit 62, is maintained, and it is possible to sufficiently supply oil to the gear 28 and the oil pump gear 36. Thus, with the internal combustion engine 5 of the present embodiment, it is possible to desirably supply oil to the gear 28 and the oil pump gear 36 while reducing the machining cost.

[0062] With the internal combustion engine 5 of the present embodiment, the gasket 50 is a paper gasket. A paper gasket is less expensive than a metal gasket. On the other hand, a paper gasket is softer than a metal gasket, and has a property that it swells by absorbing oil. Therefore, a paper gasket is more easily deformed than a metal gasket. With the internal combustion engine 5 of the present embodiment, however, since the gasket 50 is closed around the primary slit 61 and the internal slit 62, the gasket 50 is not easily deformed despite being a paper gasket. Thus, a paper gasket can be used as the gasket 50. According to the present embodiment, it is possible to desirably supply oil to the gear 28 and the oil pump gear 36 while further reducing the cost.

[0063] With the internal combustion engine 5 of the present embodiment, the first mating surface 7A and the second mating surface 22A are surfaces parallel to the vertical plane. The internal slit 62 of the gasket 50 is open on the left side and on the right side in the internal space 90 defined by the crankcase 7 and the cover 22. Therefore, oil having passed through the internal slit 62 of the gasket 50 falls down from both sides of the gasket 50. Therefore, it is possible to supply oil over a wide area from the gasket 50.

[0064] As shown in FIG. 6, the gasket 50 includes the protrusions 52 and 53, which are located downward of the internal slit 62 and protruding downward. Oil, being a liquid, has a property that it easily collects at the protrusions 52 and 53 protruding downward. Therefore, it is possible to allow oil, which has passed through the internal slit 62 of the gasket 50, to collect at the protrusions 52 and 53, and it is possible to desirably supply oil from the protrusions 52 and 53. Particularly, the protrusion 52 is located directly upward of the gear 28, and the protrusion 53 is located directly upward of the oil pump gear 36. Therefore, oil having collected at the protrusion 52 can be supplied directly to the gear 28, and oil having collected at the protrusion 53 can be supplied directly to the oil pump gear 36. According to the present embodiment, it is possible to desirably supply oil to the gear 28 and the oil pump gear 36 while reducing the machining cost.

[0065] As shown in FIG. 6, the oil pump gear 36 is placed upward of the liquid surface 33 of oil stored at the bottom of the crankcase 7 and the cover 22 when the internal combustion engine 5 is inoperative. When the oil pump gear 36 is immersed in the oil stored, the oil can be stirred up as the oil pump gear 36 rotates, and the stirred-up oil can be supplied to the oil pump gear 36 and the gear 28. However, when the oil pump gear 36 is placed upward of the liquid surface 33 of oil, the oil cannot be stirred up by the oil pump gear 36. According to the present embodiment, the advantageous effect of supplying oil to the gear 28 and the oil pump gear 36 through the primary slit 61 and the internal slit 62 of the gasket 50 is more pronounced.

[0066] With the internal combustion engine 5 of the present embodiment, the oil intake holes 87 and 88 communicating with the oil passageway 85 are provided between the oil supply hole 84 and the internal slit 62 along the primary slit 61 of the gasket 50. A part of oil having flowed into the primary slit 61 via the oil supply hole 84 flows into the oil intake holes 87 and 88, and oil not having flowed into the oil intake holes 87 and 88 flows into the internal slit 62. Since oil in the primary slit 61 is preferentially supplied to the oil intake holes 87 and 88, it is possible to supply a sufficient amount of oil to the valve operating mechanism 47, etc., in the cylinder head cover 15. Therefore, it is possible to desirably supply oil to the gear 28 and the oil pump gear 36, and it is also possible to desirably supply oil to the valve operating mechanism 47, etc., in the cylinder head cover 15.

[0067] Although there is no particular limitation on the shape of the internal slit 62 of the gasket 50, if it is shaped so as to extend in a diagonally downward direction or a vertically downward direction as in the present embodiment, it is more likely that oil flows quickly through the internal slit 62 under the influence of gravity. Therefore, it is possible to desirably supply oil in the primary slit 61 to the gear 28 and the oil pump gear 36 through the internal slit 62.

[0068] According to the present embodiment, the outline of the distal end of the internal slit 62 of the gasket 50 is formed in an arc shape. Therefore, oil is unlikely to remain inside the internal slit 62, and it is possible to quickly supply oil to the gear 28 and the oil pump gear 36 via the internal slit 62.

[0069] While one embodiment of the present invention has been described above, it is understood that the present invention is not limited to the embodiment described above. Next, some alternative embodiments will be described briefly.

[0070] As described above, the gasket 50 is not limited to a paper gasket but may be a metal gasket. The gasket 50 may also be a resin gasket. There is no particular limitation on the material of the gasket 50. The gasket 50 may be made of a single material, or may be a plurality of materials combined together.

[0071] The first mating surface 7A and the secondmating surface 22A do not always need to be surfaces parallel to the vertical plane, but may be, for example, surfaces inclined from the vertical plane or surfaces perpendicular to the vertical plane.

[0072] The protrusion 52 of the gasket 50 does not always need to be placed directly upward of the gear 28. Similarly, the protrusion 53 does not always need to be placed directly upward of the oil pump gear 36.

[0073] Although the lubricated members, which receive oil having passed through the internal slit 62 of the gasket 50, are the gear 28 and the oil pump gear 36 in the embodiment described above, there is no particular limitation on the lubricated members. The lubricated members may be other components of the internal combustion engine 5 such as the clutch 40 and the transmission 35, for example.

[0074] The terms and expressions used herein are used for explanation purposes and should not be construed as being restrictive. It should be appreciated that the terms and expressions used herein do not eliminate any equivalents of features illustrated and mentioned herein, but include various modifications falling within the claimed scope of the present invention. The present invention may be embodied in many different forms. The present disclosure is to be considered as providing examples of the principles of the invention. These examples are described herein with the understanding that such examples are not intended to limit the present invention to preferred embodiments described herein and/or illustrated herein. Hence, the present invention is not limited to the preferred embodiments described herein. The present invention includes any and all preferred embodiments including equivalent elements, modifications, omissions, combinations, adaptations and/or alterations as would be appreciated by those skilled in the art on the basis of the present disclosure. The limitations in the claims are to be interpreted broadly based on the language included in the claims and not limited to examples described in the present specification or during the prosecution of the application.

Reference Signs List

[0075] 

1

Motorcycle (straddled vehicle)

7

Crankcase (first case)

7A

First mating surface

8

Cylinder body

9

Cylinder head

15

Cylinder head cover

16

Piston

19

Connecting rod

22

Cover (second case)

22A

Second mating surface

28

Gear (lubricated member, first member)

33

Liquid surface of oil

36

Oil pump gear (lubricated member, second member)

44

Intake valve

46

Exhaust valve

47

Valve operating mechanism

50

Gasket

52

First protrusion

53

Second protrusion

61

Primary slit

62

Internal slit

84

Oil supply hole

85

Oil passageway

87, 88

Oil intake hole

Claims

1. An internal combustion engine (5) for a vehicle (1), the internal combustion engine (5) comprising:

a first case (7) including a first mating surface (7A) and an oil supply hole (84) formed in the first mating surface (7A);

a second case (22) including a second mating surface (22A) opposing the first mating surface (7A), and fastened to the first case (7);

a gasket (50) placed between the first case (7) and the second case (22); and

a lubricated member (28, 36) placed in an internal space (90) defined by the first case (7) and the second case (22) and placed so that, when the internal combustion engine (5) is installed on the vehicle (1), at least a part the lubricated member (28, 36) is aligned with the gasket (50), when the vehicle (1) is seen from above, wherein:

a primary slit (61) and an internal slit (62) connected to the primary slit (61) are formed in a surface of the gasket (50) facing the first mating surface (7A),

the primary slit (61) is formed in a part of the gasket (50) that is placed between the first mating surface (7A) and the second mating surface (22A),

the primary slit (61) overlaps with the oil supply hole (84),

the internal slit (62) is formed in a part of the gasket (50) that is placed in the internal space (90),

the internal slit (62) is placed upward of the lubricated member (28, 36), when the internal combustion engine (5) is installed on the vehicle (1), and

the outline of the primary slit (61) and the internal slit (62) is formed in a closed loop.

2. The internal combustion engine (5) according to claim 1, wherein the gasket (50) is a paper gasket.

3. The internal combustion engine (5) according to claim 1 or 2, wherein, when the internal combustion engine (5) is installed on the vehicle (1), the first mating surface (7A) and the second mating surface (22A) are surfaces parallel to a vertical plane.

4. The internal combustion engine (5) according to any one of claims 1 to 3, wherein the gasket (50) includes a protrusion (52) protruding downward, the protrusion (52) placed in the internal space (90) and, when the internal combustion engine (5) is installed on the vehicle (1), located downward of the internal slit (62).

5. The internal combustion engine (5) according to any one of claims 1 to 3, wherein the gasket (50) includes a protrusion (53) protruding downward, the protrusion (53) placed in the internal space (90) and, when the internal combustion engine (5) is installed on the vehicle (1), located directly upward of the lubricated member (28, 36).

6. The internal combustion engine (5) according to any one of claims 1 to 3, wherein:

the lubricated member comprises a first member (28) and a second member (36); and

the gasket (50) includes a first protrusion (52) protruding downward, the first protrusion (52) placed in the internal space (90) and, when the internal combustion engine (5) is installed on the vehicle (1), located directly upward of the first member (28), and a second protrusion (53) protruding downward, the second protrusion (53) placed in the internal space (90) and, when the internal combustion engine (5) is installed on the vehicle (1), located directly upward of the second member (36).

7. The internal combustion engine (5) according to any one of claims 1 to 6, wherein the lubricated member comprises a gear (28).

8. The internal combustion engine (5) according to any one of claims 1 to 7, wherein the lubricated member comprises an oil pump (34) including an oil pump gear (36).

9. The internal combustion engine (5) according to claim 8, wherein:

oil is stored at a bottom of the first case (7) and/or the second case (22), when the internal combustion engine (5) is installed on the vehicle (1); and

the oil pump gear (36) is placed upward of a liquid surface of the oil stored at the bottom when the internal combustion engine (5) is inoperative.

10. The internal combustion engine (5) according to any one of claims 1 to 9, wherein the first case is a crankcase (7) supporting a crankshaft (18), the internal combustion engine (5) comprising:

a cylinder body (8) connected to the crankcase (7), the cylinder body (8) accommodating therein a piston (16) linked to the crankshaft (18) via a connecting rod (19);

a cylinder head (9) connected to the cylinder body (8), the cylinder head (9) including an intake valve (44) and an exhaust valve (46); and

a cylinder head cover (15) connected to the cylinder head (9), the cylinder head cover (15) including a valve operating mechanism (47) configured to operate the intake valve (44) and the exhaust valve (46), wherein:

an oil intake hole (87, 88) overlapping with the primary slit (61) of the gasket (50) is formed in the crankcase (7); and

an oil passageway (85) connecting between the oil intake hole (87, 88) and an internal space of the cylinder head cover (15) is formed in the crankcase (7), the cylinder body (8), the cylinder head (9) and the cylinder head cover (15).

11. The internal combustion engine (5) according to claim 10, wherein the oil intake hole (87, 88) is provided between the oil supply hole (84) and the internal slit (62) along the primary slit (61) of the gasket (50).

12. The internal combustion engine (5) according to any one of claims 1 to 11, wherein the internal slit (62) of the gasket (50) is formed in a shape extending in a vertically downward direction or a diagonally downward direction, when the internal combustion engine (5) is installed on the vehicle (1).

13. The internal combustion engine (5) according to any one of claims 1 to 12, wherein an outline of a distal end of the internal slit (62) of the gasket (50) is formed in an arc shape.

14. A straddled vehicle (1) comprising the internal combustion engine (5) according to any one of claims 1 to 13.

Drawing