JP6340809B2 - Engine cooling structure - Google Patents

Description

  The present invention relates to a cooling structure for an engine provided in a scooter type motorcycle or the like.

Conventionally, in an engine provided in a scooter type motorcycle or the like, a configuration in which a cylinder and a cylinder head are forcibly cooled by a cooling fan is known.
For example, Patent Document 1 discloses a configuration in which a cylinder and a cylinder head are cooled by a cooling fan that rotates integrally with a crankshaft. When such a configuration is adopted, in order to efficiently cool the cylinder and the cylinder head, it is important to smoothly flow the cooling air from the cooling fan toward the cylinder and the cylinder head.

JP 2001-241325 A

  In an engine provided in a scooter type motorcycle or the like, there is a case where the outer side of the crankcase is covered with a case cover, and a cooling fan is further installed on the outer side of the case cover. When adopting such a configuration, if there is a large step between the crankcase and the case cover, the flow of the cooling air from the cooling fan is stagnant at this step, and the cooling air from the cooling fan is sent to the cylinder and It becomes difficult to flow smoothly toward the cylinder head. As a result, the cylinder and the cylinder head cannot be efficiently cooled, and the cooling performance of the engine may be deteriorated.

  In view of the above circumstances, an object of the present invention is to improve the cooling performance of an engine by smoothly flowing cooling air from a cooling fan toward a cylinder and a cylinder head.

  The present invention includes a crankcase that supports a crankshaft, a cylinder that is coupled to the crankcase, a cylinder head that is coupled to the cylinder, a case cover that covers an outer side in the left-right direction of the crankcase, and the case A cooling fan provided outside the cover in the left-right direction; and a fan cowling that covers an outer periphery of the cooling fan and guides cooling air from the cooling fan toward the cylinder and the cylinder head. The cover includes a projecting portion projecting outward in the left-right direction with respect to the side surface of the crankcase, and a guide extending while inclining inward in the left-right direction from the edge of the projecting portion toward the side surface of the crankcase. And a wind plate part.

  By providing the case guide plate with the above structure on the case cover, it is possible to suppress the stagnation of the cooling air from the cooling fan, and the cooling air from the cooling fan is directed toward the cylinder and the cylinder head. Smooth flow is possible. Therefore, the cylinder and the cylinder head can be efficiently cooled, and the cooling performance of the engine can be improved.

  The air guide plate portion may protrude outward from the mating surface of the crankcase and the case cover in a side view.

  By adopting such a configuration, it is not necessary to project a part of the mating surface of the crankcase and the case cover in accordance with the shape of the air guide plate portion. For this reason, it is possible to avoid the case cover from becoming complicated.

  The cooling fan is configured to rotate integrally with the crankshaft about the crankshaft axis, and the air guide plate portion is arranged in a tangential direction of a virtual circle centered on the crankshaft axis. It may extend toward the side close to the cylinder and the cylinder head.

  By adopting such a configuration, it becomes easy to guide the cooling air from the cooling fan to the cylinder and the cylinder head side, and the cylinder and the cylinder head can be cooled more efficiently.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to improve the cooling performance of an engine by flowing the cooling air from a cooling fan smoothly toward the cylinder and cylinder head side.

1 is a right side view showing a motorcycle according to an embodiment of the present invention. 1 is a right side view showing a power unit of a motorcycle according to an embodiment of the present invention. 1 is a perspective view from below showing an engine in a state where a fan cowling and a cylinder cowling are removed in a motorcycle according to an embodiment of the present invention. 1 is a perspective view from below showing an engine in a motorcycle according to an embodiment of the present invention. It is AA sectional drawing of FIG. 1 is a right side view showing a front portion of a power unit in a state where a magnet, a cooling fan, and a fan cowling are removed in a motorcycle according to an embodiment of the present invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the following embodiment, a case where the present invention is applied to a scooter type motorcycle 1 will be described. Hereinafter, words indicating directions such as up and down, left and right, and front and rear are used with reference to the direction viewed from the occupant of the motorcycle 1. Arrows Fr, Rr, L, and R appropriately attached to the drawings respectively indicate the front, rear, left, and right sides of the motorcycle 1. Arrows I and O appropriately attached to the respective drawings indicate inward and outward directions in the left-right direction, respectively.

  First, the overall configuration of the motorcycle 1 will be described.

  As shown in FIG. 1, the motorcycle 1 is provided with an underbone-type vehicle body frame 2 that constitutes a framework of the vehicle body. The vehicle body frame 2 includes a head pipe 3 disposed at the upper end of the front portion, a down tube 4 extending rearward and downward from the head pipe 3, and a seat rail 5 extending rearward and upward from the rear end of the down tube 4. It is equipped with.

  A front fork 6 and a handle bar 7 are supported on the head pipe 3. A front wheel 8 is pivotally supported at the lower end of the front fork 6, and a front fender 9 is provided so as to cover the front wheel 8.

  A front end portion of the power unit 10 is supported on the rear lower portion of the down tube 4, and a rear wheel 11 is pivotally supported on the rear end portion of the power unit 10. The periphery of the head pipe 3 and the down tube 4 is covered with a front cover 12 from the front and covered with a leg shield 13 from the rear.

  The seat rail 5 is covered by a frame cover 14, and a low floor footboard 15 is provided between the frame cover 14 and the leg shield 13 for a driver to place his / her feet when getting on. . A rear fender 16 is provided on the rear end side of the frame cover 14 so as to cover the rear wheel 11. A driver seat 17 is provided on the front upper side of the rear fender 16. A luggage box 18 for accommodating a helmet or the like is provided below the driver seat 17.

  Next, the power unit 10 will be described in more detail.

  As shown in FIG. 2 and the like, the power unit 10 includes an engine 20 and an exhaust device 21 fixed to the engine 20.

  First, the engine 20 of the power unit 10 will be described. The engine 20 is, for example, an SOHC air-cooled single-cylinder engine.

  As shown in FIGS. 3 and 4, the engine 20 covers a crankcase 22, a cylinder 23 connected to the crankcase 22, a cylinder head 24 connected to the cylinder 23, and a front side of the cylinder head 24. A head cover 25, a case cover 26 covering the right side (outward in the left-right direction) of the front portion of the crankcase 22, a magnet 27 and a cooling fan 28 provided on the right side (outward in the left-right direction) of the case cover 26, and magneto 27 and a fan cowling 30 that covers the outer periphery of the cooling fan 28, and a cylinder cowling 31 that covers the outer periphery of the cylinder 23 and the cylinder head 24.

  The crankcase 22 is formed by joining the left case portion 22L and the right case portion 22R. As shown in FIG. 2 and the like, an oil pan 32 is provided below the crankcase 22. At the rear part of the oil pan 32, a boss part 33 projects rearward. The boss portion 33 is formed integrally with the oil pan 32.

  As shown in FIG. 5, a case-side box portion 35 opened toward the right side (outward in the left-right direction) is provided at the right end portion of the crankcase 22. The case side box portion 35 is recessed leftward (inward in the left-right direction) with respect to the right side surface 34 (surface in the left-right direction) of the crankcase 22. The case-side box portion 35 has a bottom wall portion 36 located to the left (inward in the left-right direction) with respect to the right side surface 34 of the crankcase 22, and rightward (outward in the left-right direction) from the outer periphery of the bottom wall portion 36. And a peripheral wall portion 37 protruding toward the front.

  As shown in FIG. 6, a crankshaft 38 is axially supported in the crankcase 22 along the left-right direction (the depth direction in FIG. 6). The crankshaft 38 is provided to be rotatable about the axis X. The crankshaft 38 is connected to the rear wheel 11 (see FIG. 1) via a power transmission mechanism (not shown) including a continuously variable transmission and a centrifugal clutch.

  A piston 40 is accommodated in the cylinder 23 so as to be able to reciprocate. The piston 40 is connected to the crankshaft 38 via a connecting rod 41, and the reciprocating motion of the piston 40 is converted to rotation of the crankshaft 38 via the connecting rod 41.

  As shown in FIG. 3 and the like, the cylinder 23 extends along a predetermined axial direction Y (in this embodiment, a direction inclined slightly upward toward the front). A plurality of stages (five stages in the present embodiment) of fins 42 project from the outer periphery of the cylinder 23 at intervals in the axial direction Y. A raised portion 39 is provided along the axial direction Y at the left end of the lower wall surface of the cylinder 23. The raised portion 39 is provided continuously with the plurality of fins 42. A cam chain (not shown) is accommodated on the inner surface side of the raised portion 39. The cam chain connects a crankshaft 38 with a valve operating mechanism (not shown) for operating an intake valve and an exhaust valve (both not shown).

  The cylinder head 24 extends along the axial direction Y. The cylinder head 24 is disposed on the front side of the cylinder 23 (one side in the axial direction Y). On the outer periphery of the cylinder head 24, a plurality of stages (five stages in the present embodiment) of fins 43 project from the axial direction Y at intervals.

  As shown in FIG. 6 and the like, an intake port 45 is provided on the upper wall surface 44 of the cylinder head 24. The intake port 45 communicates with a combustion chamber 46 provided between the cylinder 23 and the cylinder head 24. An intake pipe 47 is connected to the intake port 45. An air cleaner and a fuel injection device (both not shown) are connected to the intake pipe 47. After the air introduced from the air cleaner and the fuel injected from the fuel injection device are mixed, the intake pipe 47 is connected to the intake pipe 47 via the intake port 45. And is introduced into the combustion chamber 46. An exhaust port 51 is provided on the lower wall surface 50 of the cylinder head 24. The exhaust port 51 is in communication with the combustion chamber 46. The exhaust port 51 is connected to a front end portion of an exhaust pipe 100 described later.

  As shown in FIG. 5 and the like, the case cover 26 is attached to the right end portion of the crankcase 22 (right case portion 22R) so as to close the case side box portion 35, and is disposed between the crankcase 22 and the magnet 27. ing. The case cover 26 is provided with a cover-side box portion 53 that is open toward the left (inward in the left-right direction and on the crankcase 22 side). The cover side box portion 53 bulges rightward (outward in the left-right direction) with respect to the right side surface 34 and the mating surface of the crankcase 22. The cover-side box portion 53 projects to the right (right and left direction outward) with respect to the right side surface 34 of the crankcase 22, and from the outer periphery of the overhang portion 54 to the left (right and left direction inner). And an outer peripheral portion 55 protruding toward the front.

  The outer surface (right side surface) of the overhang portion 54 of the cover side box portion 53 faces the magnet 27. As shown in FIG. 6 and the like, the overhanging portion 54 includes a main body portion 56 and an extending portion 57 extending from the main body portion 56 toward the front lower side. A circular through hole 60 is provided in the left-right direction at the center of the body portion 56 of the overhang portion 54, and the shaft end 38 a of the crankshaft 38 is inserted into the through hole 60. As a result, the shaft end 38a of the crankshaft 38 protrudes to the right (outward in the left-right direction) of the case cover 26. On the outer surface (right side surface) of the main body portion 56 of the overhang portion 54, a plurality of (seven in the present embodiment) ridges 61 project. The ridges 61 are arranged radially about the axis X of the crankshaft 38. On the extended portion 57 of the overhang portion 54, a ridge 62 projects from the extension line of the ridge 61 on the front lower side of the main body portion 56.

  As shown in FIG. 5 and the like, the left edge portion (the inner edge portion in the left-right direction) of the outer peripheral portion 55 of the cover side box portion 53 is the right side of the peripheral wall portion 37 of the case side box portion 35 provided in the crankcase 22. It is joined to the edge (the edge on the outer side in the left-right direction). Thereby, the case side box part 35 and the cover side box part 53 form the closed cross section (box structure). The cover side box portion 53 is provided so as to enlarge the internal space of the case side box portion 35. A recess 63 is formed between the right side surface 34 of the crankcase 22 and the outer peripheral portion 55 of the cover side box portion 53.

  The case cover 26 is provided with a wind guide plate portion 64 on the front upper side of the cover side box portion 53. The air guide plate portion 64 extends from the front end edge 54a of the overhang portion 54 (the end portion on the side close to the cylinder 23 and the cylinder head 24, which is a connection portion with the outer peripheral portion 55) to the right side surface 34 of the crankcase 22. It extends while tilting to the left (inward in the left-right direction). A space corresponding to the concave portion 63 is formed between the air guide plate portion 64 and the outer peripheral portion 55. That is, a space surrounded by the right side surface 34 of the crankcase 22, the outer peripheral portion 55 of the cover side box portion 53, and the air guide plate portion 64 is formed. The front end portion (front end portion) of the air guide plate portion 64 may be in contact with the right side surface 34 of the crankcase 22 or opposed to the right side surface 34 of the crankcase 22 with a slight gap. Also good. The air guide plate portion 64 is curved in a circular arc shape in cross section. The air guide plate portion 64 protrudes in an eaves shape (a bowl shape) from the front end edge 54 a of the overhang portion 54 and covers a part of the recess 63.

  As shown in FIG. 6, the air guide plate portion 64 protrudes outward from the mating surface (see the dotted line B in FIG. 6) of the crankcase 22 and the case cover 26 in a side view. The air guide plate portion 64 extends above the axis X of the crankshaft 38 in a side view and protrudes from the front end edge 54a of the overhang portion 54 to the side where the cylinder 23 is disposed. Specifically, it extends toward the side (front side in the present embodiment) adjacent to the cylinder 23 and the cylinder head 24 along the tangential direction D of the virtual circle C centering on the axis X of the crankshaft 38. The virtual circle C indicates the outer diameter position of the magnet 27. The positional relationship between the outer diameter position and the air guide plate 64 will be described in detail. The position of the air guide plate 64 in the side view is the position of the magnet 27. It extends from the front end edge 54a of the overhanging portion 54 toward the crankcase 22 at the outer diameter position, and the air guide plate portion 64 has an outer portion and an inner portion of the outer diameter position of the magnet 27. .

  As shown in FIG. 3 and the like, a pair of guide plate portions 65 and 66 project from the upper and lower edge portions of the air guide plate portion 64 toward the right side (outward in the left-right direction). The base end side portion of the upper guide plate portion 65 is inclined upward toward the right (outward in the left-right direction). The lower guide plate portion 66 is inclined downward toward the right (outward in the left-right direction). For this reason, the distance between the pair of guide plate portions 65 and 66 gradually increases toward the right (outward in the left-right direction). The protruding length of the upper guide plate portion 65 from the wind guide plate portion 64 is longer than the protruding length of the lower guide plate portion 66 from the wind guide plate portion 64.

  As shown in FIG. 6, the case cover 26 is provided with a fixing portion 68 on the rear upper side of the cover side box portion 53. A fixed boss 69 is provided at the rear portion of the fixed portion 68. The fixed boss 69 protrudes outward from the mating surface (see dotted line B in FIG. 6) of the crankcase 22 and the case cover 26 in a side view.

  The magnet 27 (see FIG. 3 and the like) has an annular shape. The magnet 27 is fixed to the outer periphery of the shaft end 38a of the crankshaft 38 (not shown in FIG. 3), and is configured to rotate integrally with the crankshaft 38 around the axis X of the crankshaft 38. Yes.

  The cooling fan 28 is, for example, a centrifugal fan. The cooling fan 28 is disposed on the right side of the magnet 27 (outward in the left-right direction). The cooling fan 28 is fixed to the right side surface of the magnet 27 or is fixed to the outer periphery of the shaft end 38a of the crankshaft 38 (not shown in FIG. 3), and is centered on the axis X of the crankshaft 38. The crankshaft 38 and the magnet 27 are integrally rotated. The cooling fan 28 has an annular connection that connects a large number of blade portions 73 that are arranged radially about the axis X of the crankshaft 38 and the right end portion (end portion in the left-right direction) of each blade portion 73. Part 74, and rotates clockwise in FIG. Regarding the rotation of the cooling fan 28, the air guide plate portion 64 is disposed above the axis X of the crankshaft 38, and on the tip side of the arrow S (see FIG. 6) indicating the rotation direction of the cooling fan 28. Is provided. The air guide plate portion 64 is disposed at a connection portion between a housing portion 75 of the fan cowling 30 described later and a duct portion 76 extending toward the cylinder 23 side.

  As shown in FIG. 5 and the like, the fan cowling 30 is inclined leftward (inward in the left-right direction) toward the front side (side adjacent to the cylinder 23 and the cylinder head 24) from the storage part 75 and the storage part 75. And a duct portion 76 that extends. A vortex chamber 58 is formed inside the accommodating portion 75. The vortex chamber 58 is located on the right side (outward in the left-right direction) of the overhanging portion 54 of the cover side box portion 53. The accommodating portion 75 covers the outer periphery of the magnet 27 and the cooling fan 28 accommodated in the vortex chamber 58. As shown in FIG. 4 and the like, an opening 77 for introducing outside air is provided on the outer surface (right side surface) of the accommodating portion 75. The duct portion 76 is disposed on the right side (outward in the left-right direction) of the cylinder 23 and the cylinder head 24.

  The cylinder cowling 31 is formed by joining an upper cowling portion 31U and a lower cowling portion 31L. A front end portion of the cylinder cowling 31 is connected to the head cover 25. The rear end portion of the cylinder cowling 31 is connected to the crankcase 22. On the right side surface of the cylinder cowling 31, an introduction port 78 is provided that protrudes to the right (outward in the left-right direction). The introduction port 78 communicates with the duct portion 76 of the fan cowling 30. An exhaust pipe opening 80 and an exhaust port 81 are provided on the lower surface of the cylinder cowling 31. An exhaust pipe 100 to be described later is loosely inserted into the exhaust pipe opening 80.

  Next, the exhaust device 21 of the power unit 10 will be described.

  As shown in FIG. 2, the exhaust device 21 includes an exhaust pipe 100 that extends substantially in the front-rear direction, a muffler 101 that is connected to the rear end of the exhaust pipe 100, and a bracket 102 that is fixed to the front part of the muffler 101. It is equipped with.

  As shown in FIG. 6, the front end portion of the exhaust pipe 100 is connected to an exhaust port 51 provided on the lower wall surface 50 of the cylinder head 24 of the engine 20. Thus, the air-fuel mixture discharged from the combustion chamber 46 of the engine 20 flows into the muffler 101 through the exhaust pipe 100 and is discharged from the muffler 101 to the rear of the vehicle.

  As shown in FIG. 2, a first attachment piece 103 extending toward the front is provided on the upper portion of the bracket 102. A front end portion of the first mounting piece 103 is fixed to a fixing boss 69 provided on a fixing portion 68 of the case cover 26 by a first fixing bolt 104. A second attachment piece 105 extending forward is provided at the lower portion of the bracket 102. A front end portion of the second mounting piece 105 is fixed to a boss portion 33 protruding from the oil pan 32 of the crankcase 22 by a second fixing bolt 106.

  When the motorcycle 1 configured as described above travels, the cooling fan 28 rotates integrally with the crankshaft 38 as the crankshaft 38 rotates. When the cooling fan 28 rotates in this manner, outside air is taken into the housing portion 75 of the fan cowling 30 through the opening 77, and cooling air is generated. The cooling air passes through a space surrounded by the duct portion 76 and the air guide plate portion 64 of the fan cowling 30 as indicated by three thick arrows in FIG. 5, and the cylinder 23 and the cylinder head 24 are passed by the duct portion 76. To the space between the cylinder 23 and the cylinder head 24 and the cylinder cowling 31 via the introduction port 78 of the cylinder cowling 31. Thereafter, the cooling air cools the cylinder 23 and the cylinder head 24 and is discharged from the exhaust pipe opening 80 and the exhaust port 81 to the outside.

  By the way, in the present embodiment, as described above, the projecting portion 54 of the case cover 26 projects rightward (outward in the left-right direction) from the right side surface 34 of the crankcase 22. A step is generated between the surface 34 and the overhanging portion 54 of the case cover 26. If the flow of the cooling air from the cooling fan 28 stagnates in this stepped portion, it becomes difficult to smoothly flow the cooling air from the cooling fan 28 toward the cylinder 23 and the cylinder head 24 side.

  However, in the present embodiment, as described above, the wind guide plate portion 64 that extends while tilting leftward (inward in the left-right direction) toward the right side surface 34 of the crankcase 22 from the front edge 54a of the overhang portion 54 is provided in the case. The cover 26 is provided. For this reason, it is possible to eliminate a part of the step generated between the right side surface 34 of the crankcase 22 and the overhanging portion 54 of the case cover 26. Accordingly, the stagnation of the cooling air from the cooling fan 28 can be suppressed, and the cooling air from the cooling fan 28 can flow smoothly toward the cylinder 23 and the cylinder head 24 side. Therefore, the cylinder 23 and the cylinder head 24 can be efficiently cooled, and the cooling performance of the engine 20 can be improved.

  Further, the air guide plate portion 64 protrudes outward from the mating surface of the crankcase 22 and the case cover 26 (see the dotted line B in FIG. 6) in a side view. Therefore, it is not necessary to project a part of the mating surface of the crankcase 22 and the case cover 26 according to the shape of the air guide plate portion 64, and it is possible to avoid the case cover 26 from becoming complicated. .

  Further, the air guide plate portion 64 is a side close to the cylinder 23 and the cylinder head 24 along the tangential direction D of the virtual circle C centering on the axis X of the crankshaft 38 in a side view (in the present embodiment, the front side). ). By adopting such a configuration, it becomes easy to guide the cooling air from the cooling fan 28 toward the cylinder 23 and the cylinder head 24, and the cylinder 23 and the cylinder head 24 can be cooled more efficiently.

  In addition, a pair of guide plate portions 65 and 66 project from the upper and lower edges of the air guide plate portion 64 toward the right side (outward in the left-right direction). By adopting such a configuration, it becomes easier to guide the cooling air from the cooling fan 28 toward the cylinder 23 and the cylinder head 24, and the cylinder 23 and the cylinder head 24 can be cooled more efficiently. .

  Further, the air guide plate portion 64 is provided so as to cover the concave portion 63 formed between the right side surface 34 of the crankcase 22 and the outer peripheral portion 55 of the cover side box portion 53. Therefore, it is possible to prevent the cooling air from the cooling fan 28 from creating a vortex in the recess 63 and increase the airflow resistance, and the cylinder 23 and the cylinder head 24 can be cooled more efficiently.

  Further, the air guide plate 64 is curved in a circular arc shape in cross section. Therefore, it is possible to make the air guide plate 64 more smoothly continuous with the front end edge 54a of the projecting portion 54 than when the air guide plate 64 has a linear cross section (flat plate), and cooling from the cooling fan 28 is possible. Wind stagnation can be more effectively suppressed.

  In the present embodiment, the case where the air guide plate portion 64 is curved in a cross-sectional arc shape as described above has been described. However, in another different embodiment, the air guide plate portion 64 may be linear in cross section (flat plate shape).

  In the present embodiment, the case where the air guide plate portion 64 extends toward the side close to the cylinder 23 and the cylinder head 24 (the front side in the present embodiment) has been described. On the other hand, in another different embodiment, the air guide plate portion 64 may extend toward the side away from the cylinder 23 and the cylinder head 24. In this case, for example, the air guide plate portion 64 can be provided in the region surrounded by the thick line R in FIG. In still another different embodiment, the air guide plate portion 64 may be provided over the entire outer periphery of the overhang portion 54.

  In the present embodiment, the case where the configuration of the present invention is applied to the scooter type motorcycle 1 has been described. On the other hand, in another different embodiment, the configuration of the present invention may be applied to a motorcycle other than a scooter type such as a sports type or an off-road type. Further, the configuration of the present invention may be applied to vehicles other than motorcycles such as electric wheelchairs and rough terrain vehicles.

20 Engine 22 Crankcase 23 Cylinder 24 Cylinder head 26 Case cover 28 Cooling fan 30 Fan cowling 34 Right side surface (of the crankcase) 38 Crankshaft 54 Overhang portion 64 Wind guide plate portion B (Crankcase and case cover) mating surface C Virtual circle D Tangent direction (of the virtual circle) X Center axis (of the crankshaft)

Claims (3)

A crankcase that supports the crankshaft;
A cylinder coupled to the crankcase;
A cylinder head coupled to the cylinder;
A case cover covering the outside of the crankcase in the left-right direction;
A cooling fan provided outside the case cover in the left-right direction;
A fan cowling that covers the outer periphery of the cooling fan and guides the cooling air generated by the cooling fan toward the cylinder and the cylinder head;
A magnet arranged inward in the left-right direction of the cooling fan , and
The case cover is
An overhanging portion projecting outward in the left-right direction with respect to the side surface of the crankcase;
An air guide plate portion that extends while inclining inward in the left-right direction from the edge of the overhang portion toward the side surface of the crankcase ,
An engine cooling structure, wherein an outer surface of the overhanging portion faces an inner surface of the magneto .   2. The engine cooling structure according to claim 1, wherein the air guide plate portion protrudes outward from a mating surface of the crankcase and the case cover in a side view. 3. The cooling fan is configured to rotate integrally with the crankshaft around the axis of the crankshaft;
The air guide plate portion extends toward a side close to the cylinder and the cylinder head along a tangential direction of an imaginary circle centering on an axis of the crankshaft in a side view. The engine cooling structure according to claim 1 or 2.

Images