Vehicle power unit

Abstract

The present invention provides a power unit (4) for a vehicle, comprising: a crankshaft; a crankcase (40) supporting the crankshaft; and a fan (60) configured to rotate integrally with the crankshaft and to draw in external gas from the outer side of the crankshaft in an axial direction. The outer portion of the fan (60) in the crankcase (40), viewed axially, forms cooling air passages (P1, P2) through which the air generated by the fan (60) passes.

Description

Technical Field

[0001] This invention relates to a power unit for vehicles. Background Technology

[0002] In existing motorcycle-type vehicles, the power unit is sometimes equipped with a structure that forces air cooling via a cooling fan. For example, Japanese Utility Model Application Publication No. 61-77463 discloses a structure in which a fan is mounted on the crankshaft, and an airflow path toward the fan is provided on the outside of the crankcase via a component separately from the crankcase. Furthermore, Japanese Patent Application Publication No. 2015-155653 discloses a structure in which rib-like protrusions are provided on the cover of the oil pan. Summary of the Invention

[0003] However, in the existing cooling structure, there is room for improvement in the cooling efficiency of the power unit housing itself around the fan.

[0004] The present invention provides a power unit capable of efficiently cooling the periphery of a fan.

[0005] The power unit of the first embodiment of the present invention includes: a rotating shaft; a housing supporting the rotating shaft; and a fan configured to rotate integrally with the rotating shaft and to draw in external gas from the outer side of the rotating shaft in the axial direction, wherein the outer portion of the fan in the housing, as viewed from the axial direction, forms a cooling air passage through which the air generated by the fan passes.

[0006] The power unit of the second embodiment of the present invention is based on the power unit of the first embodiment described above. The power unit may also include a cylinder component, the cylinder component being connected to the housing and housing a piston so as to be able to reciprocate, and the cooling air passage being separately arranged from the air guide passage formed by the cylinder component.

[0007] The power unit of the third embodiment of the present invention, based on the power unit of the first or second embodiment described above, may also include a rib provided in the cooling air passage and extending radially along the rotation axis.

[0008] The power unit of the fourth embodiment of the present invention, based on the power unit of the third embodiment described above, may also have the rib disposed on the housing.

[0009] The power unit of the fifth embodiment of the present invention can also be based on the power unit of any of the first to fourth embodiments described above, wherein the power unit has a cover installed on the housing and covering the fan to divide the cooling air passage, and an exhaust port communicating with the cooling air passage is formed on the cover, wherein the cooling air passage is formed so that the air generated by the fan flows to the exhaust port without turning back to the upstream side.

[0010] The power unit of the sixth embodiment of the present invention can also be based on the power unit of any of the first to fifth embodiments described above, wherein the power unit has a cover installed on the housing and covering the fan to divide the cooling air passage, and an exhaust port communicating with the cooling air passage is formed on the cover, and the exhaust port opens in a direction that is inclined at more than 90 degrees relative to the vertical upward and forward.

[0011] The power unit of the seventh embodiment of the present invention, based on the power unit of the fifth or sixth embodiment described above, may also have a rear exhaust port located behind the central axis of the rotating shaft, the rear exhaust port opening outward in the vehicle width direction and forming a mesh shape.

[0012] The power unit of the eighth embodiment of the present invention can also be based on the power unit of any of the fifth to seventh embodiments described above, wherein the exhaust port has a front exhaust port located in front of the central axis of the rotating shaft, and the front exhaust port exhausts air only to the lower part of the housing.

[0013] The power unit of the ninth embodiment of the present invention can be based on the power unit of any of the first to eighth embodiments described above, and the cooling air passage is provided with multiple outlets that contain lubricating oil.

[0014] The power unit of the tenth embodiment of the present invention can also be based on the power unit of any of the first to ninth embodiments described above, wherein the housing has an oil pan for storing lubricating oil at a position lower than the rotating shaft, and the cooling air passage is disposed on the outside of the oil pan.

[0015] The power unit of the eleventh embodiment of the present invention can be based on the power unit of any of the first to tenth embodiments described above, wherein the cooling air passage is only located at a position lower than the rotating shaft.

[0016] According to the power unit of the first scheme described above, since the part of the housing located on the outer side of the fan when viewed from the axial direction exchanges heat with the air generated by the fan passing through the cooling air passage, the periphery of the fan can be cooled efficiently.

[0017] According to the power unit of the second scheme described above, since the air passing through the airflow path formed by the cylinder components may become high-temperature, it is possible to direct the air that has not exchanged heat with the cylinder components to the cooling airflow path. Therefore, the area around the fan can be cooled efficiently.

[0018] According to the power unit of the third scheme described above, the airflow generated by the fan flowing in the cooling air passage can be rectified. Therefore, turbulence in the airflow in the cooling air passage can be suppressed, thereby promoting heat exchange between the casing and the air generated by the fan.

[0019] According to the power unit of the fourth scheme mentioned above, the surface area of ​​the housing in the cooling air passage is increased by ribs, thus promoting heat exchange between the housing and the air generated by the fan in the cooling air passage.

[0020] According to the power unit of the fifth scheme described above, the increase in air pressure loss in the cooling air passage can be suppressed, thus allowing the air generated by the fan to pass smoothly through the cooling air passage. Therefore, heat exchange between the casing and the air generated by the fan can be promoted.

[0021] According to the power unit of the sixth embodiment described above, by opening the exhaust vent at an angle of 90 degrees or more relative to the front, it is possible to prevent foreign objects flying from the front from entering the cooling air passage through the exhaust vent while the vehicle is in motion. Furthermore, by opening the exhaust vent at an angle of 90 degrees or more relative to vertical upwards, it is possible to prevent foreign objects falling from above from entering the cooling air passage through the exhaust vent, and even if foreign objects do enter the cooling air passage through the exhaust vent, they can be discharged through the exhaust vent under the influence of gravity. Therefore, it is possible to suppress adverse conditions caused by the intrusion of foreign objects into the cooling air passage.

[0022] According to the power unit of the seventh embodiment mentioned above, when the driving air flowing along the outer side of the power unit in the vehicle width direction passes over the rear exhaust vent, foreign objects can easily enter the cooling air passage through the rear exhaust vent. Therefore, by forming the rear exhaust vent into a mesh shape, the intrusion of foreign objects into the cooling air passage can be effectively suppressed. In addition, when the rear end of the underbody is located in front of the power unit, water flowing along the side of the underbody during driving can easily be scattered towards the part of the housing located further forward than the central axis of the rotation axis. Therefore, by configuring the rear exhaust vent to open only at a position further backward than the central axis of the rotation axis, the intrusion of water scattered from the underbody into the cooling air passage through the rear exhaust vent can be suppressed.

[0023] According to the power unit of the eighth embodiment described above, the negative pressure generated at the front exhaust vent by the driving air flowing along the lower surface of the housing promotes the airflow in the cooling air passage connected to the front exhaust vent. Furthermore, with the rear end of the underbody located in front of the power unit, water flowing along the side of the underbody during operation is prone to splashing towards the portion of the housing located further forward than the central axis of the rotation shaft. Therefore, by configuring the front exhaust vent to exhaust only downwards from the housing, it is possible to prevent water splashed from the underbody from entering the cooling air passage through the front exhaust vent.

[0024] According to the power unit of the ninth embodiment mentioned above, the periphery of the outlet in the housing can be effectively cooled, thus cooling the lubricating oil when the oil is discharged through the outlet.

[0025] According to the power unit of the tenth embodiment mentioned above, the oil pan can directly exchange heat with the air generated by the fan passing through the cooling air passage. Therefore, the lubricating oil can be cooled efficiently.

[0026] According to the power unit of the eleventh embodiment described above, it is able to centrally cool the parts of the housing that are easily contacted by heated lubricating oil. Therefore, it can efficiently cool parts of the housing that may become hot. Attached Figure Description

[0027] Figure 1 This is a left-side view of the motorized two-wheeled vehicle according to the implementation method.

[0028] Figure 2 This is a right-side view of the power unit in the implementation method.

[0029] Figure 3 yes Figure 2 A cross-sectional view at line III-III.

[0030] Figure 4 It means from Figure 2 The image shown is an enlarged view of the power unit with the fan cover and shield removed.

[0031] Figure 5 yes Figure 2 A cross-sectional view at the V-V line.

[0032] Figure 6 It means Figure 4 A three-dimensional view of a portion of the power unit shown.

[0033] Figure 7 It means Figure 4 A three-dimensional view of a portion of the power unit shown. Detailed Implementation

[0034] The embodiments of the present invention will now be described based on the accompanying drawings. It should be noted that in the following description, structures with the same or similar functions are labeled with the same symbols. Furthermore, repeated descriptions of these structures may be omitted. Additionally, the directions (front, back, up, down, left, right) in the following description are the same as those in the vehicle described below. That is, the up-down direction is consistent with the vertical direction, and the left-right direction is consistent with the vehicle width direction. Furthermore, in the figures used in the following description, arrow UP indicates upward, arrow FR indicates forward, and arrow LH indicates left.

[0035] <Overall structure of the vehicle>

[0036] Figure 1 This is a left-side view of the motorized two-wheeled vehicle according to the implementation method.

[0037] like Figure 1 As shown, the motorized two-wheeled vehicle 1 of this embodiment is a small motorcycle-type straddle-mounted vehicle with a footrest for a passenger sitting on a seat 7. The motorized two-wheeled vehicle 1 includes a frame 2, a front wheel 3 that is steerably supported on the frame 2, a power unit 4 that is sway-mounted on the frame 2, a rear wheel 5 supported on the power unit 4, and a body cover 6 that forms the outer contour of the vehicle.

[0038] The frame 2 includes a head tube 21, a downframe 22, a lower frame 23, a subframe 24, and a pair of rear frames 25, which are joined together by welding or the like. The head tube 21 is located at the front end of the frame 2. The head tube 21 supports the front wheel 3 for steering via a steering rod passing through it. The downframe 22 branches off from the head tube 21 and extends downwards and rearwards. The lower frame 23 extends rearwards from the lower end of the downframe 22 and then upwards. The subframe 24 connects the lower frame 22 to the rear portion of the lower frame 23. The rear frames 25 are connected to the subframe 24 and extend rearwards and upwards from the connection point with the subframe 24. The rear end of the lower frame 23 is joined to the middle portion of the rear frame 25.

[0039] The power unit 4 is a so-called mono-swing rear suspension. The power unit 4 drives the rear wheel 5, which serves as the drive wheel. The power unit 4 is positioned from in front of the rear wheel 5 to the left side of the rear wheel 5. The power unit 4 is supported on the frame 2 below the rear frame 25 and can swing up and down. The structure of the power unit 4 will be described later.

[0040] The body cover 6 is composed of multiple outer panels. The body cover 6 includes a front cover portion 31 that covers the head tube 21 and forms leg guards, a front side cover portion 32 that covers the descending frame 22, a central channel 33 that covers the sub-frame 24 behind the front side cover portion 32, a lower cover portion 34 that covers the lower frame 23 below the central channel 33 and forms a bottom step and bottom cover, and a rear cover portion 35 that covers the rear frame 25 behind the central channel 33. It should be noted that the multiple outer panels constituting the body cover 6 do not need to be divided according to the aforementioned cover portions; they can also be configured to cross the boundaries of the cover portions, or each cover portion can be composed of multiple outer panels.

[0041] <Power Unit>

[0042] Figure 2 This is a right-side view of the power unit in the implementation method. Figure 3 yes Figure 2 A cross-sectional view at line III-III.

[0043] like Figure 2 and Figure 3 As shown, the power unit 4 integrates an engine 11, an ACG starter motor 13, and a power transmission structure 12. The output of the engine 11 is transmitted from the crankshaft 14 (rotating shaft) to the rear wheel 5 via the power transmission structure 12. The power transmission structure 12 includes a gearbox 15, a centrifugal clutch (not shown), and a reduction mechanism.

[0044] The transmission 15 is a V-belt continuously variable transmission (CVT) connected to the crankshaft 14. The transmission 15 is housed in a transmission case 16. The transmission case 16 is elongated in the vehicle width direction and opens outwards in the vehicle width direction. The transmission case 16 is closed by a transmission case cover 17, forming a transmission chamber inside the transmission case 16 that houses the transmission 15. A rear axle 5a (the axle of the rear wheel 5) protruding towards the vehicle's width center is provided at the rear end of the power unit 4. The vehicle is propelled by transmitting the rotational power of the crankshaft 14 to the rear axle 5a via the power transmission structure 12, thereby driving the rear wheels 5 supported on the rear axle 5a.

[0045] The ACG starter motor 13 functions as both a starter and a generator. The ACG starter motor 13 is connected to a battery (not shown). When the ACG starter motor 13 functions as a starter, the battery supplies power to the ACG starter motor 13. When the ACG starter motor 13 functions as a generator, the battery is charged with regenerative power from the ACG starter motor 13. It should be noted that the engine 11 and the ACG starter motor 13 are controlled by a control unit (not shown).

[0046] Engine 11 is a single-cylinder engine that drives crankshaft 14 along the width of the vehicle.

[0047] The engine 11 includes a cylinder 41 (cylinder assembly), a piston, and a crankcase 40 (house). The cylinder 41 is located at the front of the power unit 4. The cylinder 41 includes a cylinder block 41a, a cylinder head 41b, and a cylinder head cover 41c. The cylinder head 41b is connected to the front end of the cylinder block 41a. The cylinder head cover 41c covers the front end of the cylinder head 41b. A combustion chamber is formed inside the cylinder 41.

[0048] The piston is connected to the crankshaft 14 via connecting rod 42. The piston is housed in cylinder 41 and is capable of reciprocating. The reciprocating movement of the piston is transmitted to the crankshaft 14 via connecting rod 42. That is, the crankshaft 14 is rotated by the reciprocating movement of the piston. Hereinafter, the central axis C of the crankshaft 14 will sometimes be simply referred to as "axis C". In addition, the direction orthogonal to axis C and extending radially from axis C is called radial. It should be noted that in this embodiment, axis C extends along the vehicle width direction.

[0049] like Figure 3 As shown, the crankcase 40 supports the crankshaft 14 so that it can rotate. The crankcase 40 is located in front of the rear wheel 5 and connected to the rear end of the cylinder block 41a. The crankcase 40 is made of metal. The crankcase 40 is formed by fastening the left crankcase 40L and the right crankcase 40R together. The right crankcase 40R forms half of the crankcase 40. The left crankcase 40L forms half of the crankcase 40.

[0050] The crankcase 40 includes a crank arm housing 45 for housing the crank arm 14a of the crankshaft 14, a motor housing 50 for housing the ACG starter motor 13, and an oil pan 55 for storing lubricating oil. The front part of the transmission case 16 is located on the left side of the crank arm housing 45. The left crankcase 40L is integrally formed with the transmission case 16.

[0051] The crankshaft arm receiving portion 45 is formed by a right crankcase 40R and a left crankcase 40L. The crankshaft arm receiving portion 45 forms a receiving chamber A between the right crankcase 40R and the left crankcase 40L, housing the crankshaft arm 14a and crankshaft pin of the crankshaft 14. The crankshaft arm receiving portion 45 supports the crankshaft journal 14c of the crankshaft 14 at the right side wall 45r of the right crankcase 40R via a bearing 46R, enabling rotation. The crankshaft arm receiving portion 45 also supports the crankshaft journal 14c at the left side wall 45l of the left crankcase 40L via a bearing 46L, enabling rotation. The crankshaft arm receiving portion 45 supports the crankshaft 14 in such a way that the end of the crankshaft 14 protrudes outward in the vehicle width direction.

[0052] The motor housing 50 is located on the right side of the crankcase 40. The motor housing 50 is situated to the right of the crankshaft arm housing 45 and is formed solely by the right crankcase 40R. The motor housing 50 opens outwards in the vehicle width direction. The motor housing 50, together with the fan shroud 70 (described later), forms the motor housing chamber B that houses the ACG starter motor 13.

[0053] Figure 4 It means from Figure 2 The image shown is an enlarged view of the power unit with the fan cover and shield removed.

[0054] like Figure 3 and Figure 4 As shown, the motor housing 50 has a peripheral wall 51 that surrounds the ACG starter motor 13 radially outward. A cylinder-side cutout 52 is provided on the peripheral wall 51. The cylinder-side cutout 52 is formed on the cylinder 41 side relative to the axis C when viewed from the vehicle width direction. The cylinder-side cutout 52 is cut in such a way that the inner side of the peripheral wall 51 is opened forward when viewed from the vehicle width direction.

[0055] like Figure 3 As shown, the oil pan 55 is located at the lower part of the crankcase 40.

[0056] The oil pan 55 is located below the crankshaft arm receiving portion 45. The oil pan 55 is formed by the right crankcase 40R and the left crankcase 40L. The oil pan 55 is positioned below the transmission case 16, passing below the motor receiving portion 50 and below the crankshaft arm receiving portion 45. The oil pan 55 forms a storage space for storing lubricating oil at a position lower than the crankshaft 14. The lower surface of the oil pan 55 forms the lower surface of the crankcase 40. An oil drain (not shown) with an opening at the bottom of the storage space is provided in the oil pan 55. This drain is located in the right crankcase 40R and opens outwards (to the right) in the vehicle width direction towards the outside of the oil pan 55. The drain is closed by a vent bolt 56 (see reference). Figure 2 ).

[0057] The ACG starter motor 13 is housed inside the motor housing 50. The ACG starter motor 13 is an external rotor type motor. The ACG starter motor 13 is mounted on the crankshaft journal 14c on the side opposite to the bearing 46R, across the crankshaft arm 14a. The ACG starter motor 13 includes a stator 13a and an external rotor 13b.

[0058] The stator 13a is fixed to the right crankcase 40R. The stator 13a has teeth and coils wound around the teeth. The outer rotor 13b is fixed to the right end of the crankshaft 14 (crankshaft journal 14c). The outer rotor 13b has a cylindrical shape covering the outer periphery of the stator 13a. Magnets are provided on the inner circumferential surface of the outer rotor 13b, which are radially opposed to the stator 13a. The ACG starter motor 13 generates electricity based on the relative rotation of the outer rotor 13b and the stator 13a.

[0059] like Figure 2 and Figure 3As shown, the power unit 4 also has a cooling structure for cooling the engine 11, etc. The cooling structure is mainly formed by the crankcase 40, the fan 60, the fan cover 70 covering the fan 60, and the shield 65 covering the cylinder 41.

[0060] like Figure 3 and Figure 4 As shown, the fan 60 is coaxially arranged with the crankshaft 14 and mounted on the outer rotor 13b. The fan 60 is fixed to the right end of the crankshaft 14 via the outer rotor 13b and can rotate integrally with the crankshaft 14. The fan 60 is a centrifugal fan. The fan 60 has a disc-shaped base 61 coaxially arranged with axis C, blades 62 erected from the base 61 outward in the vehicle width direction, and an annular upper plate 63 formed and joined to each blade 62 on the side opposite to the base 61. The surface of the base 61 facing outward in the vehicle width direction extends inward in the vehicle width direction from the radially inner side to the outer side. The blades 62 extend radially outward from the inner peripheral end on the rotation center side. The outer peripheral portion of the blades 62 protrudes radially outward from the base 61. The upper plate 63 is coaxially arranged with axis C. The upper plate 63 is joined to the outer peripheral portion of the blades 62. The upper plate 63 extends inward in the vehicle width direction from the radially inner side to the outer side. As the crankshaft 14 rotates, the fan 60 draws in air from the outer side in the vehicle width direction through the blades 62 at the center of the fan 60, and generates air radially outward through the space between the base 61 and the upper plate 63.

[0061] A fan side rib 63a is provided on the upper plate 63. The fan side rib 63a is erected on the outer surface of the upper plate 63 facing the vehicle width direction. When viewed from the vehicle width direction, the fan side rib 63a extends in a circular shape with axis C as the center. The fan side rib 63a is arranged radially at intervals relative to the inner and outer peripheral edges of the upper plate 63.

[0062] like Figure 3 As shown, the fan shroud 70 is integrated with the right crankcase 40R. The fan shroud 70, as a whole, has a shape that opens inward in the vehicle width direction. The fan shroud 70 covers the fan 60 from the outside in the vehicle width direction, and a fan housing space D, including the motor housing chamber B, is formed between the fan shroud 70 and the motor housing 50, housing the fan 60 and the ACG starter motor 13. The fan shroud 70 has a cylindrical inlet nozzle 71 that opens toward the center of the fan 60, an outer cylinder 73 that surrounds the inlet nozzle 71 from the outside, and a connecting wall 74 that connects the outer cylinder 73 to the crankcase 40.

[0063] The inlet nozzle 71 guides the external air drawn into the fan 60 towards the fan 60. The inlet nozzle 71 is coaxially configured with the fan 60. The inner edge of the inlet nozzle 71 in the vehicle width direction is located radially inward of the fan side rib 63a of the fan 60, and is opposite to the inner periphery of the upper plate 63 of the fan 60 in the vehicle width direction. The inner edge of the inlet nozzle 71 is located outward of the fan side rib 63a in the vehicle width direction. A shielding part 72 is fixedly provided inside the inlet nozzle 71, which allows air to pass through and restricts the passage of foreign objects. In the illustrated example, the shielding part 72 is honeycomb shaped. However, the structure of the shielding part 72 is not particularly limited; for example, it can be configured as a mesh, or it can be a fixed or movable louver.

[0064] The outer cylinder 73 is cylindrical and coaxially disposed with the inlet nozzle 71. The outer cylinder 73 extends from its outer end edge in the vehicle width direction towards the inner side in the vehicle width direction of the inlet nozzle 71 and has a gap relative to the inlet nozzle 71. The inner end edge in the vehicle width direction of the outer cylinder 73 is located radially outward of the fan side rib 63a of the fan 60 and is opposite to the upper plate 63 of the fan 60 in the vehicle width direction. The inner end edge of the outer cylinder 73 is located inward of the fan side rib 63a in the vehicle width direction.

[0065] Figure 5 yes Figure 2 A cross-sectional view at the V-V line.

[0066] like Figure 3 and Figure 5 As shown, the connecting wall 74 extends radially outward and inward in the vehicle width direction from the outer periphery of the outer cylinder 73 and abuts against the opening edge of the peripheral wall 51 of the motor housing 50.

[0067] The connecting wall 74 extends circumferentially around the outer cylinder 73 when viewed from the vehicle width direction (see reference). Figure 2 ).

[0068] like Figure 2 As shown, the shroud 65 is combined with the fan shroud 70. The shroud 65 is positioned in front of the fan shroud 70. The shroud 65 is formed in a manner connected to the fan shroud 70. The shroud 65 is provided to surround the cylinder block 41a and the cylinder head 41b. The shroud 65 is positioned on the right side of the cylinder 41 with a gap relative to the cylinder block 41a and the cylinder head 41b. The space between the shroud 65 and the cylinder 41 communicates with the fan housing space D through the cylinder side cutout 52 of the peripheral wall 51 of the crankcase 40 (see reference). Figure 4 The space between the shield 65 and the cylinder 41 (cylinder body 41a and cylinder head 41b) is an air duct 66 for cooling the cylinder through which the air generated by the fan 60 passes.

[0069] like Figures 3-5As shown, the portion of the crankcase 40 located outside the fan 60 when viewed axially cooperates with the fan shroud 70 to form a first cooling air passage P1 and a second cooling air passage P2 through which the air generated by the fan 60 passes. The first cooling air passage P1 and the second cooling air passage P2 are formed by a portion extending radially outward from the right side wall 45r of the crankshaft arm housing 45 when viewed axially (the right side wall of the oil pan 55). The first cooling air passage P1 and the second cooling air passage P2 are independent of the air guide 66. The first cooling air passage P1 and the second cooling air passage P2 respectively connect the fan housing space D to the outside of the power unit 4. When viewed from the vehicle width direction, the first cooling air passage P1 and the second cooling air passage P2 are arranged such that they clamp the vent bolt 56 and the oil drain hole (not shown).

[0070] like Figure 3 and Figure 4 As shown, the first cooling air passage P1 is positioned below the air guide passage 66 when viewed from the vehicle width direction. The first cooling air passage P1 is positioned forward and below the axis C when viewed from the vehicle width direction. The first cooling air passage P1 extends forward and downward from the fan housing space D when viewed from the vehicle width direction.

[0071] Figure 6 and Figure 7 It means Figure 4 A three-dimensional view of a portion of the power unit shown.

[0072] like Figure 3 , Figure 6 and Figure 7 As shown, the first cooling air passage P1 communicates with the fan housing space D through a cutout 53 formed on the peripheral wall 51 of the motor housing 50. The first cooling air passage P1 extends along the outer surface of the oil pan 55. The first cooling air passage P1 is divided by the oil pan 55 and a pair of transverse walls 80 provided in the right crankcase 40R, and the extension 83 provided in the fan shroud 70.

[0073] like Figure 6 and Figure 7 As shown, a pair of transverse walls 80 protrude outwards from the right side of the oil pan 55 in the vehicle width direction. The pair of transverse walls 80 extend forward and downward from the two edges of the peripheral wall 51 of the motor housing 50, separated by a cutout 53. The pair of transverse walls 80 extend substantially parallel to each other. A rib 81, extending substantially parallel to the pair of transverse walls 80, is provided between them. The rib 81 protrudes outwards from the right side of the oil pan 55 in the vehicle width direction.

[0074] like Figure 2 and Figure 3As shown, the extension 83 protrudes downward from the outer periphery of the connecting wall 74 of the fan shroud 70 when viewed from the vehicle width direction. The extension 83 has an outer wall 84 that extends from the connecting wall 74 at intervals relative to the oil pan 55, and a pair of side walls 85 that extend from both sides of the outer wall 84 toward the oil pan 55. The extension 83 is formed in a U-shaped cross-section that opens toward the crankcase 40. The outer wall 84 is positioned from a position outside the vehicle width direction relative to the oil pan 55 to a position below the oil pan 55. The outer wall 84 has an upstream portion 84a that overlaps with the pair of side walls 80 from the outer side in the vehicle width direction, and a downstream portion 84b that extends from the upstream portion 84a toward the inner side in the vehicle width direction. An upstream half of the first cooling air passage P1 is formed between the upstream portion 84a and the oil pan 55. The downstream portion 84b extends from the lower edge of the upstream portion 84a toward the inner side in the vehicle width direction to a position below the oil pan 55. A downstream half of a first cooling air passage P1 is formed between the downstream portion 84b and the oil pan 55. The side wall 85 is connected to the portion of the outer wall 84 from the upstream portion 84a to the downstream portion 84b. The side wall 85 is arranged such that the end edge of the oil pan 55 side abuts against the end edge of the transverse wall 80.

[0075] like Figure 3 As shown, a front exhaust port 87 communicating with the first cooling air passage P1 is formed between the extension 83 and the oil pan 55. The front exhaust port 87 is defined by the inner edge in the vehicle width direction of the downstream portion 84b of the outer wall 84, the inner edge in the vehicle width direction of each side wall 85, and the lower surface of the oil pan 55. The front exhaust port 87 is located forward of the axis C. The front exhaust port 87 opens inward in the vehicle width direction. The front exhaust port 87 exhausts air only downwards from the oil pan 55.

[0076] The first cooling air passage P1, as described above, is formed such that after the air generated by the fan 60 flows downward and forward through the cut 53 of the peripheral wall 51 at the upstream end, it changes direction inward in the vehicle width direction and flows to the front exhaust port 87 at the downstream end. Thus, the air generated by the fan 60 flowing in the first cooling air passage P1 flows from the upstream end to the downstream end without turning back upstream.

[0077] like Figure 4 and Figure 5 As shown, the second cooling air passage P2 is located behind the first cooling air passage P1 when viewed from the vehicle width direction. The second cooling air passage P2 is positioned rearward and below the axis C when viewed from the vehicle width direction. The second cooling air passage P2 extends rearward and downward from the fan housing space D when viewed from the vehicle width direction.

[0078] like Figures 5-7As shown, the second cooling air passage P2 communicates with the fan housing space D through a cutout 54 formed on the peripheral wall 51 of the motor housing 50. The second cooling air passage P2 is divided by the oil pan 55 and inner guide wall 90 provided in the right crankcase 40R, and the connecting wall 74 and outer guide wall 92 provided in the fan shroud 70.

[0079] The inner guide wall 90 extends such that it connects the two edges of the peripheral wall 51 of the motor housing 50 across the cutout 54. When viewed from the vehicle width direction, the inner guide wall 90 extends radially outward from the peripheral wall 51 (see reference). Figure 4 The space inside the inner guide wall 90 is divided from the inside in the vehicle width direction by the right side wall of the oil pan 55. The space inside the inner guide wall 90 communicates with the fan housing space D to form the upstream half of the second cooling air passage P2, and opens to the outside in the vehicle width direction. Ribs 91 extending radially when viewed from the vehicle width direction are formed between the inner guide walls 90. In the illustrated example, three ribs 91 are provided. The ribs 91 protrude from the right side of the oil pan 55 to the outside in the vehicle width direction. The radially outer end edge of each rib 91 connects to the inner circumferential surface of the inner guide wall 90.

[0080] like Figure 2 and Figure 5 As shown, the outer guide wall 92 is located radially outside the connecting wall 74 of the fan shroud 70. The outer guide wall 92 is formed by extending the inner guide wall 90 outward in the vehicle width direction. The outer guide wall 92 extends along the inner guide wall 90 when viewed from the vehicle width direction. Both ends of the outer guide wall 92 are connected to the connecting wall 74 of the fan shroud 70. Thus, the outer guide wall 92 and the connecting wall 74 form a closed section. A space is formed between the outer guide wall 92 and the connecting wall 74 that directly communicates with the inner side of the inner guide wall 90 to form the downstream half of the second cooling air passage P2. A rear exhaust vent 94 communicating with the second cooling air passage P2 is formed between the outer guide wall 92 and the connecting wall 74. The rear exhaust vent 94 is divided by the outer edge of the outer guide wall 92 in the vehicle width direction and the outer peripheral surface of the connecting wall 74. The rear exhaust vent 94 is located further rear than the axis C. The rear exhaust vent 94 opens outward in the vehicle width direction and overlaps with the second cooling air passage P2 when viewed axially. The rear exhaust vent 94 is formed in a mesh shape, allowing air to pass through while restricting the passage of foreign objects.

[0081] The second cooling air passage P2, as described above, is formed such that after the air generated by the fan 60 flows downward and backward through the cutout 54 of the peripheral wall 51 at the upstream end, it changes direction outward in the vehicle width direction and flows to the rear exhaust port 94 at the downstream end. Thus, the air generated by the fan 60 flowing in the second cooling air passage P2 flows from the upstream end to the downstream end without turning back upstream.

[0082] As explained above, in this embodiment, the outer portion of the fan 60 in the crankcase 40, viewed axially, forms a first cooling air passage P1 and a second cooling air passage P2 through which the air generated by the fan 60 passes. According to this structure, the portion of the crankcase 40 located axially outside the fan 60 exchanges heat with the air generated by the fan 60 passing through the first cooling air passage P1 and the second cooling air passage P2, thus enabling efficient cooling of the periphery of the fan 60.

[0083] The first cooling air passage P1 and the second cooling air passage P2 are respectively separated from the air guide passage 66 formed by the cylinder 41. According to this structure, since the air passing through the air guide passage 66 formed by the cylinder 41 may become high-temperature, air that has not exchanged heat with the cylinder 41 can flow to the first cooling air passage P1 and the second cooling air passage P2. Therefore, the periphery of the fan 60 can be cooled efficiently.

[0084] The power unit 4 includes a rib 81 disposed in the first cooling air passage P1 and extending radially, and a rib 91 disposed in the second cooling air passage P2 and extending radially. According to this structure, the airflow generated by the fan 60 flowing in the first cooling air passage P1 and the second cooling air passage P2 can be rectified. Therefore, turbulence in the airflow in the first cooling air passage P1 and the second cooling air passage P2 can be suppressed, thereby promoting heat exchange between the crankcase 40 and the air generated by the fan 60.

[0085] Ribs 81 and 91 are respectively disposed in the crankcase 40. According to this structure, the surface area of ​​the crankcase 40 in the first cooling air passage P1 and the second cooling air passage P2 is increased by ribs 81 and 91, thus promoting heat exchange between the crankcase 40 and the air generated by the fan 60 in the first cooling air passage P1 and the second cooling air passage P2.

[0086] The first cooling air passage P1 and the second cooling air passage P2 are configured such that the air generated by the fan 60 flows to the exhaust ports 87 and 94 without being deflected upstream. This structure suppresses the increase in air pressure loss in the cooling air passages P1 and P2, thus allowing the air generated by the fan 60 to flow smoothly through them. Consequently, heat exchange between the crankcase 40 and the air generated by the fan 60 is promoted.

[0087] The front exhaust vent 87 and the rear exhaust vent 94 open in the width direction of the vehicle. According to this structure, by opening the front exhaust vent 87 and the rear exhaust vent 94 at a 90-degree angle relative to the front, it is possible to prevent foreign objects flying from the front from entering the cooling air passages P1 and P2 through the exhaust vents 87 and 94 while the vehicle is moving. Furthermore, by opening the front exhaust vent 87 and the rear exhaust vent 94 at a 90-degree angle relative to vertical upwards, it is possible to prevent foreign objects falling from above from entering the cooling air passages P1 and P2 through the exhaust vents 87 and 94. Even if foreign objects do enter the cooling air passages P1 and P2 through the exhaust vents 87 and 94, they can be discharged through the exhaust vents 87 and 94 under the influence of gravity. Therefore, it is possible to prevent adverse situations caused by foreign objects entering the cooling air passages P1 and P2.

[0088] The rear exhaust vent 94 opens outward in the vehicle width direction and is formed in a mesh shape. According to this structure, when the driving airflow along the outer side of the power unit 4 in the vehicle width direction flows past the rear exhaust vent 94, foreign objects can easily enter the second cooling air passage P2 through the rear exhaust vent 94. Therefore, by forming the rear exhaust vent 94 in a mesh shape, the intrusion of foreign objects into the second cooling air passage P2 can be effectively suppressed. Furthermore, with the rear end of the underbody located in front of the power unit 4, water flowing along the side of the underbody during driving can easily splash into the crankcase 40 located further forward of the axis C. Therefore, by configuring the rear exhaust vent 94 to open only at a position further rear than the axis C, the intrusion of water splashed from the underbody into the second cooling air passage P2 through the rear exhaust vent 94 can be suppressed.

[0089] The front exhaust vent 87 is located forward of the axis C and exhausts air only downwards from the crankcase 40. With this configuration, the driving airflow along the lower surface of the crankcase 40 can create negative pressure in the front exhaust vent 87, thereby promoting airflow in the first cooling air passage P1 connected to the front exhaust vent 87. Furthermore, with the rear end of the underbody cover located in front of the power unit 4, water flowing along the side of the underbody cover during driving can easily splash into the portion of the crankcase 40 located forward of the axis C. Therefore, by configuring the front exhaust vent 87 to exhaust only downwards from the crankcase 40, it is possible to prevent water splashed from the underbody cover from intruding into the first cooling air passage P1 through the front exhaust vent 87.

[0090] The first cooling air passage P1 and the second cooling air passage P2 are arranged such that they sandwich a lubricating oil outlet. According to this structure, the periphery of the outlet in the crankcase 40 can be effectively cooled, thus cooling the lubricating oil when it is discharged through the outlet.

[0091] The first cooling air passage P1 and the second cooling air passage P2 are located on the outside of the oil pan 55. This structure allows the oil pan 55 to directly exchange heat with the airflow generated by the fan 60 passing through the first cooling air passage P1 or the second cooling air passage P2. Therefore, the lubricating oil can be cooled efficiently.

[0092] The first cooling air passage P1 and the second cooling air passage P2 are located only below the crankshaft 14. This structure allows for concentrated cooling of areas in the crankcase 40 that are easily accessible to heated lubricating oil. Therefore, it enables efficient cooling of potentially high-temperature components within the crankcase 40.

[0093] It should be noted that the present invention is not limited to the embodiments described above with reference to the accompanying drawings, and various modifications are possible within its technical scope.

[0094] For example, in the above embodiments, an example of applying the present invention to a power unit for a motorized two-wheeled vehicle is shown, but the scope of application of the present invention is not limited to power units for motorized two-wheeled vehicles. For example, the present invention can be applied to all power units for straddle-type vehicles where the driver rides astride the vehicle. Straddle-type vehicles include not only motorized two-wheeled vehicles, but also motorized tricycles, buggies, ATVs (All Terrain Vehicles), and other motorized four-wheeled vehicles. Furthermore, while the power unit 4 in the above embodiments only has an engine as a power source for vehicle operation, the present invention can also be applied to power units that have a motor as a power source.

[0095] Furthermore, in the above embodiment, the exhaust vents 87 and 94 open in the vehicle width direction, but the opening direction of the exhaust vents is not particularly limited. However, it is preferable that the exhaust vents open in a direction inclined at 90 degrees or more relative to vertical upwards and forwards. By opening the exhaust vents in a direction inclined at 90 degrees or more relative to forwards, it is possible to prevent foreign objects flying from the front from entering the cooling air passage through the exhaust vents while the vehicle is in motion. Moreover, by opening the exhaust vents in a direction inclined at 90 degrees or more relative to vertical upwards, it is possible to prevent foreign objects falling from above from entering the cooling air passage through the exhaust vents, and even if foreign objects do enter the cooling air passage through the exhaust vents, they can be discharged through the exhaust vents under the action of gravity.

[0096] In addition, in the above embodiment, the power unit is provided with multiple cooling air passages (first cooling air passage P1 and second cooling air passage P2), but only one cooling air passage may be provided.

[0097] In addition, in the above embodiment, the ribs 81 and 91 in the cooling air passages P1 and P2 are provided in the oil pan 55, but the ribs can also be provided in the fan shroud. Alternatively, the cooling air passages may not have ribs provided.

[0098] Furthermore, without departing from the spirit of the present invention, the constituent elements in the above embodiments can be appropriately replaced with well-known constituent elements.

Claims

1. A power unit for a vehicle, wherein, The vehicle power unit includes: Rotation axis; Housing that supports the rotating shaft; and A fan is configured to rotate integrally with the rotating shaft and to draw in external air from the outer side of the rotating shaft along its axial direction. A cooling air passage is formed on the side of the oil pan of the outer portion of the fan, as viewed from the axial direction within the housing, for the air generated by the fan to pass through. The vehicle power unit has ribs that protrude outward in the width direction from the cooling air passage of the housing and extend radially along the axis of rotation.

2. The vehicle power unit according to claim 1, wherein, The vehicle power unit includes a cylinder assembly connected to the housing and housing a piston capable of reciprocating movement. The cooling air passage is set separately from the air guide passage formed by the cylinder component.

3. The vehicle power unit according to claim 1 or 2, wherein, The vehicle power unit includes a cover mounted on the housing and covering the fan to divide the cooling air passage. An exhaust vent connected to the cooling air passage is formed on the cover. The cooling air passage is configured such that the air generated by the fan flows to the exhaust port without turning back upstream.

4. The vehicle power unit according to claim 1 or 2, wherein, The vehicle power unit includes a cover mounted on the housing and covering the fan to divide the cooling air passage. An exhaust vent connected to the cooling air passage is formed on the cover. The exhaust vent opens at an angle of more than 90 degrees relative to vertical upwards and forwards.

5. The vehicle power unit according to claim 3, wherein, The exhaust vent has a rear exhaust vent located behind the central axis of the rotating shaft, and the rear exhaust vent opens outward in the vehicle width direction and is formed in a mesh shape.

6. The vehicle power unit according to claim 3, wherein, The exhaust vent has a front exhaust vent located in front of the central axis of the rotating shaft, and the front exhaust vent only exhausts air to the lower part of the housing.

7. The vehicle power unit according to claim 1 or 2, wherein, The cooling air passage is provided with multiple outlets that contain lubricating oil.

8. The vehicle power unit according to claim 1 or 2, wherein, The housing has an oil pan for storing lubricating oil at a position lower than the rotating shaft. The cooling air passage is located on the outside of the oil pan.

9. The vehicle power unit according to claim 1 or 2, wherein, The cooling air passage is located only below the rotating shaft.

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