Title of Invention

"AIR-COOLED INTERNAL COMBUSTION ENGINE"

Abstract

[OBJECT] The present invention provides an air-cooled internal-combustion engine having a cylinder and a cylinder head provided with cooling fins that enable cooling air blown by a cooling fan directly mounted on the crankshaft to cool the cylinder and the cylinder head uniformly. [CONSTITUTION] A cylinder block 14 and a cylinder head 15 are provided on their outer surface with a plurality of cooling fins 23 and a plurality of cooling fins 24 arranged at predetermined intervals respectively. A centrifugal cooling fan 2 6 is fixedly mounted on the right end of a crankshaft 22 that rotates clockwise as viewed from the right side of the body. The upper portions of the right parts 23b of the cooling fins 23 are declined toward the front of the body at an angle of 45 °0 and the lower portions of the same are curved gently downward so as to extend perpendicularly to the center axis of the cylinder. The left parts 23c on the left side of the cylinder block 14 and the lower parts 23d on the lower side of the cylinder block 14 of the cooling fins 23 extend along a circumferential direction. [SELECTED DRAWING] Fig. 4

Full Text

The present invention relates to an air-cooled internal-combustion engine (or an air-water-cooled internal-combustion engine) having coolxng fins that enable the cylinder and the cylinder head of the air-cooled internal-combustion engine to be cooled uniformly with cooling air blown by a cooling fan directly mounted on the crankshaft. [Related Art] An air-cooled internal-combustion engine disclosed in Japanese Utility Model Publication (Kokoku) No. 63-32903 is provided with a shroud covering the cylinder and the cylinder head that radiate heat, and a cooling fan mounted on the crankshaft to suck cooling air through the cooling air inlet opening of the shroud and to cool the cylinder and the cylinder head by blowing the cooling air against the cooling fins of the cylinder and the cylinder head. [Problem to be Solved by the Invention] In the air-cooled internal-combustion engine disclosed in the cited Japanese utility model publication, the shroud guides the cooling air sucked through the cooling air inlet opening of the shroud toward the cylinder head. Therefore, the flow of the cooling air is blocked by the cooling fin formed perpendicularly to the center axis of the cylinder on the surface of the cylinder and the cooling air is unable to flow smoothly toward the cylinder head and the cylinder cannot uniformly be cooled along the center axis thereof. In a space around the circumference of the cooling fan covered with the shroud, a portion of the surface of the cylinder on one side of a plane including the respective center axes of the crankshaft and the cylinder is exposed satisfactorily to the cooling air blown by the cooling fan, while another portion of the surface of the cylinder on the other side of the plane is not exposed satisfactorily to the cooling air. Consequently, the' cylinder and the cylinder head cannot uniformly be cooled. [Means for Solving the Problem, Function and Effect] The present invention relates to improvements incorporated into an air-cooled internal-combustion engine to overcome those disadvantages and it is therefore an object of the present invention to provide an air-cooled internal-combustion engine comprising: a plurality of cooling fins formed on the cylinder and the cylinder head; a centrifugal cooling fan mounted on one end of the crankshaft; and a shroud covering the cylinder, the cylinder head, and the centrifugal cooling fan; characterized in that one end of each of spaces between the plurality of cooling fins opens toward cooling air blown into a cooling air inlet to a space covered with the shroud by the centrifugal cooling fan, and the lengthwise direction of the spaces between the fins is inclined at an acute angle to the flow direction of the cooling air. In the air-cooled internal-combustion engine thus constructed, the cooling air blown out through the cooling air outlet opening of the centrifugal cooling fan flows smoothly along the inclined cooling fins without being-disturbed and, consequently, the cylinder can efficiently and uniformly be cooled with respect to both the axial direction and the circumferential direction. According to the present invention, the cooling air blown into the space covered with the shroud by the centrifugal cooling fan flows through one end of each of spaces between the plurality of cooling fins into the spaces and flows smoothly along the surface of the cooling fin. Therefore, even if the cooling air contains a large amount of dust, the dust will not adhere to or deposit on the cooling fins and the dust is surely discharged outside the shroud and, therefore, the deterioration of the cooling performance due to dust deposition can be prevented. In the air-cooled internal-combustion engine stated the cooling air sucked from outside the shroud into the space covered with the shroud by the centrifugal cooling fan can be blown so as to flow smoothly along the cooling fins of the cylinder and the cylinder head to cool the cylinder and the cylinder head effectively. In the air-cooled internal-combustion engine stated since the,centrifugal cooling fan can be disposed at a position on the center axis of the crankshaft and separated from the center axis of the cylinder, a one-way clutch included in a starting system, a generator, and the output shaft can be arranged in a space between the cylinder and the centrifugal cooling fan to form the air-cooled internal combustion engine in a compact construction. In the air-cooled internal-combustion engine stated _ -the flow of the cooling air blown through the cooling air outlet opening of the centrifugal cooling fan into each of the spaces between the cooling fins is directed into two directions by the cooling fin bend in a V-form so that the cooling air flows along the spaces between the cooling fins and, consequently, the wide surface of the cylinder can uniformly be cooled. In the air-cooled internal-combustion engine stated ■ —the cooling air blown through the cooling air outlet opening of the centrifugal cooling fan into the spaces between the plurality of cooling fins curved in a helical form flows along the helical cooling fins, so that the cylinder can uniformly be cooled with respect to the axial direction and the circumference direction. In the air-cooled internal-combustion engine stated .—part of the cooling air which has not exchanged heat with the cooling fins to a maximum extent and having a comparatively low temperature flows through the air intake system which is liable to be heated by heat transferred thereto from the combustion chamber of the internal-combustion engine. Therefore, the air intake system can effectively be cooled by the cooling air of a comparatively low temperature to maintain the charging efficiency on a high level. The exhaust system heated to a high temperature can effectively be cooled by the cooling air being discharged outside the shroud through the air outlet opening. -BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS [Fig. 1} Fig. 1 is a left side view of the rear half of a scooter type motorcycle equipped with a swing power unit integrally provided with an air-cooled internal-combustion engine in a preferred embodiment according to the present invention. [Fig. 2] Fig. 2 is an enlarged side view of an essential part of Fig. 1. [Fig. 3] Fig. 3 is a longitudinal sectional view of a cylinder shroud and a fan shroud taken on line III-III in Fig. 1. [Fig. 4] Fig. 4 is an enlarged right side view of an essential part of Fig. 2, in which the fan cover is removed. [Fig. 5] Fig. 5 is a view taken in the direction of the arrows along line V-V in Fig. 3. [Fig. 6] Fig. 6 is a view taken in the direction of the arrows along lines VI-VI in Fig. 3. [Fig. 7] Fig. 7 is a view taken along a plane OY in Fig. 5. [Fig. 8] Fig. 8 is an enlarged right side view, similar to Fig. 4, of another embodiment of the present invention. [Fig. 9] Fig. 9 is a view, similar to Fig. 5, of the embodiment shown in Fig. 8. [Embodiments] A preferred embodiment according to the present invention will be described with reference to Figs. 1 to 7. A scooter type motorcycle 1, which may be a three-wheel vehicle with one front wheel and two rear wheels or a four-wheel vehicle with two front wheels and two rear wheels, has a swing power unit 2. The swing power unit 2 comprises an air-cooled internal-combustion engine 3 having a cylinder block 14 extending forward and inclined slightly upward from a horizontal plane and a cylinder head 15 attached to the front end of the cylinder block 14, and a V belt type continuously variable speed transmission 4 extending rearward on the left side of the air-cooled internal-combustion engine 3 and combined with the air-cooled internal-combustion engine 3. A rear wheel 6 is mounted on the output shaft 5 of the V belt type continuously variable speed transmission 4. A pair of hangers 7 formed on the upper wall of the crankcase of the air-cooled internal-combustion engine 3 and transversely spaced apart from each other are connected pivotally for vertical movement to brackets 9 projecting downward from the rear frame 8 of the scooter type motorcycle 1 by a linkage 10. A shock absorbing device 11 has a lower end joined to the rear part of the swing power unit 2 and an upper end joined to the rear part of the rear frame 8 and enables the swing power unit 2 to swing in a vertical plane according to the undulation of the road while the scooter type motorcycle 1 is traveling. As shown in Fig. 3, the swing power unit 2 comprises a left crankcase 12 serving as the crankcase of the air-cooled internal-combustion engine 3 and the transmission case of the V belt type continuously variable speed transmission 4, a right crankcase 13, a cylinder block 14 joined to the left crankcase 12 and the right crankcase 13, the cylinder head 15 attached to the front end of the cylinder block 14, a transmission cover 16 (Fig. 1) detachably joined to the left side of the left crankcase 12, and a right cover 17 joined to the right crankcase 13. A fan cover 18 covering a centrifugal cooling fan 26, which will be described later, is attached detachably to the right side of the right cover 17. An upper cylinder shroud 19 and a lower cylinder shroud 20 are put on a projection 21 formed on the cylinder head 15 and are detachably attached to the left crankcase 12, the right crankcase 13, the right cover 17 and the fan cover 18 so as to cover the cylinder block 14 and the cylinder head 15. The cylinder block 14 and the cylinder head 15 are provided on their outer surfaces with cooling fins 23 and 24 arranged at predetermined intervals respectively. The rotor 25 of a generator is mounted on the right end of the crankshaft 22 within a space covered with the right cover 17, and a centrifugal cooling fan 26 is combined integrally with the rotor 25 within a space covered with the fan cover 18. As shown in Fig. 4, the crankshaft 22 and the centrifugal fan 26 rotate clockwise as viewed from the right side of the body. The upper half of a cooling air passage 27 defined by the fan cover 18 is formed in a clockwise spiral form continuously receding from the center axis of the crankshaft 22. The right cover 17 is provided intermittently with partition walls 28 arranged along a spiral to form a space 29 of a form similar to that of the cooling air passage 27. The cooling fins 23 of the cylinder block 14 are bent in a V-form as shown in Fig. 7 along a line Z intersecting a plane OY extending upward at an angle of 45 °□ to a horizontal plane from the center axis of the cylinder block 14 on the right side of the body (in Fig. 5, on the left side of the body because Fig. 5 is a front view taken from the front) as shown in Fig. 5. The upper parts 23a of the cooling fins extending above the boundary line Z are inclined at an angle of 45 °□ toward the front of the body and to the left as shown in Fig. 3. The upper portions of the right parts 23b of the cooling fins extending below the boundary line Z are declined toward the front of the body at an angle of 45 °□ and the lower portions of the right parts 23b are bent gradually downward so as to extend along the surface of the cylinder block 14 perpendicularly to the center axis of the cylinder block 14. The left parts 23c and the lower parts 23d of the cooling fins extend along the circumferential direction. Ail the cooling fins 24 of the cylinder head 15 extend around the cylinder head 15 perpendicularly to the center axis. The fan cover 18 is provided with an air inlet opening 3 0 coaxially with the centrifugal cooling fan 26 and is surrounded by a cylindrical wall. A louver 31 is fitted in the air inlet opening 30. The cylinder head 15 is provided in its upper wall with an intake port 32 and in its lower wall with an exhaust port, not shown. An intake pipe 33 is connected to the intake port 32, and an exhaust pipe 34 is connected to the exhaust port. The upper cylinder shroud 19 is provided with an opening 35 at a position corresponding to the intake port 32 (Fig. 3) and a lower cylinder shroud 20 is provided with an opening 36 at a position corresponding to the exhaust port. As shown in Fig. 5, an air outlet opening 37 is formed so as to open to the right at a position on the left side (in Fig. 5, on the right side because Fig. 5 is a front view taken from the front) of the open i ng 3 6. In the embodiment thus constructed as described with reference to Figs. 1 to 7, the centrifugal fan 26 is driven for clockwise rotation, as viewed in Figs. 2 and 4, by thecrankshaft 22, and then the cooling air sucked through the air inlet opening 3 0 of the fan cover 18 on the right side of the body into the space covered with the fan cover 18 flows from the lower section through the rear section into the upper section of the cooling air passage 27 and further through the space covered with the cylinder shrouds 19 and 20 as indicated by the arrows in Figs- 4 and 5. Most part of the cooling air flowing toward the cylinder block 14 flows toward the vicinity of the boundary line Z nearest to the outlet end 27a of the cooling air passage 27. Therefore, most part of the cooling air is directed in the vicinity of the boundary line Z by the cooling fins 23 bent in a V-form toward upper side and the right side of the cylinder block 14 and flows along the upper parts 23a and the right parts 23b of the cooling fins 23 toward the cylinder head 15. Therefore, cooling air is able to flow smoothly without being disturbed. Part of the cooling air that flows near the upper parts 23a of the cooling fins flows along the left parts 23c and the lower parts 23d of the cooling fins and joins with part of the cooling air that flows downward along the right parts 23b of the cooling fins and forward along the lower parts 23d of the cooling fins, and then the cooling air is discharged through the air outlet opening 37. The cooling air flows also along the cylinder shrouds 19 and 20 to the surface of the cylinder head 15, and then flows along the cooling fins 24 extending perpendicularly to the center axis of the cylinder block 14. Then, part of the cooling air makes a detour to avoid the upper surface and the left side surface of the cylinder block 14 and flows along the lower surface of the cylinder block 14, while the rest of the cooling air flows along the right side and the lower side of the cylinder block 14, and then both parts of the cooling air are discharged through the air outlet opening 37. Thus, the cooling air flows smoothly along all the cooling fins 23 and 24 without being disturbed and, consequently, the cylinder block 14 and the cylinder head 15 are cooled entirely, uniformly and effectively through the cooling fins 23 and 24. Since the intake pipe 33 is disposed near the outlet end 27a of the cooling air passage 27, the intake pipe 33 is cooled by the cooling air of a comparatively low temperature which has not yet exchanged heat with the cooling fins 23 and 24, so that the charging efficiency is maintained on a high level. The exhaust pipe 34 of a very high temperature is cooled by the cooling air that has cooled the cylinder block 14 and the cylinder head 15 in the space covered with the cylinder shrouds 19 and 2 0 and has been heated to a comparatively high temperature. In the embodiment shown in Figs. 1 to 7, since the generator is disposed on the side of the centrifugal cooling fan 26, the cooling air passage 27 defined by the fan cover 18 is separated by a comparatively large distance away from the center axis of the cylinder block 14 in the direction of the center axis of the crankshaft. In another embodiment in which a centrifugal cooling fan 26 and a cooling air passage 27 are disposed nearer to a cylinder block 14 as stated in claim 5 and shown in Figs. 8 and 9, the cylinder block 14 is provided with helical cooling fins 23 instead of the cooling fins 23 bent in a V-form and a cylinder head 15 may be provided with helical cooling fins 24 substantially parallel to the helical cooling fins 23 of the cylinder block 14. In this embodiment, the cooling air flows helically around the entire surfaces of the cylinder block 14 and the cylinder head 15 to cool the cylinder block 14 and the cylinder head 15 uniformly. [REFERENCE CHARACTERS] 1 ... Scooter type motorcycle, 2 ... Swing power unit, 3 ... Air-cooled internal-combustion engine, 4 . . . V belt type continuously variable speed transmission, 5 ... Output shaft, 6 ... Rear wheel, 7 ... Hanger, 8 ... Rear frame, 9 ... Bracket, 10 ... Linkage, 11 ... Shock absorbing device, 12 ... Left crankcase, 13 ... Right crankcase, 14 -.. Cylinder block, 15 ... Cylinder head, 16 ... Transmission cover, 17 ... Right cover, 18 ... Fan cover, 19, 20 ... Cylinder shrouds, 21 ... Projection, 22 ... Crankshaft, 23, 24 ... Cooling fins, 25 ... Rotor, 26 ... Centrifugal cooling fan, 27 ... Cooling air passage, 28 ... Partition wall, 29 ... Space, 30 ... Air inlet opening, 31 ... Louver, 32 ... Intake port, 33 ... Intake pipe, 34 ... Exhaust pipe, 35, 36 ... Openings, 37 ... Air outlet opening We Claim: - An air-cooled internal-combustion engine comprising: a plurality of cooling fins formed on the cylinder and the cylinder head; a centrifugal cooling fan mounted on one end of the crankshaft; and a shroud covering the cylinder, the cylinder head, and the centrifugal cooling fan; characterized in that one end of each of spaces between the plurality of cooling fins opens toward cooling air blown into a cooling air inlet to a space covered with the shroud by the centrifugal cooling fan, and the lengthwise direction of the spaces between the fins is inclined at an acute angle to the flow direction of the cooling air. An air cooled internal-combustion engine as claimed in claim 1, wherein the cooling air inlet opening of the centrifugal cooling fan is located outside of the end of said crankshaft and of the cooling fan, the cooling air outlet opening of the centrifugal cooling fan is located radially outside the circumference of the cooling fan, opens toward the cylinder and is directed in a direction parallel to the center axis of the cylinder. An air-cooled internal-combustion engine as claimed in claim 2, wherein the said cooling air outlet opening of the centrifugal cooling fan is separated from the outer surface of the cylinder on the side of the cooling fan toward the extension of the crankshaft. An air-cooled internal-combustion engine as claimed in claim 1, wherein each of said cooling fins extends past a position where most part of the cooling air blown out through the cooling air outlet opening of the centrifugal cooling fan reaches the outer surface of the cylinder, and is bent in a V-shape of which the center is on a line parallel to the center axis of the cylinder and on the cylinder. An air-cooled internal-combustion engine as claimed in claim 1, wherein the cooling fins are curved in a helical form. An air-cooled internal-combustion engine substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

Documents:

381-del-1995-abstract.pdf

381-del-1995-claims.pdf

381-del-1995-correspondence-others.pdf

381-del-1995-correspondence-po.pdf

381-del-1995-description (complete).pdf

381-del-1995-drawings.pdf

381-del-1995-form-1.pdf

381-del-1995-form-13.pdf

381-del-1995-form-2.pdf

381-del-1995-form-3.pdf

381-del-1995-form-4.pdf

381-del-1995-form-9.pdf

381-del-1995-gpa.pdf

381-del-1995-petition-others.pdf

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