Title of Invention

"POWER UNIT FOR SMALL SIZED VEHICLE INCLUDING WATER COOLED INTERNAL COMBUSTION ENGINE"

Abstract

[Object] To provide a power unit for a small-sized vehicle, in which a water-cooled internal combustion engine is integrated with a power transmission, and particularly, a power unit for a small-sized vehicle, which integrally includes a radiator. [Solving Means] In a power unit 1 for a small-sized vehicle, in which a water-cooled internal combustion engine 2 is integrated with a power transmission 3 supporting a rear wheel 19 on its one side, the front portion of the power unit 1 is vertically swingably mounted on a vehicular body 0, and a radiator 39 is integrally provided on the power unit 1 at a position adjacent to a supporting bracket 13 which is swingably mounted in the power unit 1.

Full Text

Trie-present invention relates to a power unit for a small-sized vehicle. The present invention relates to. a power unit for a small-sized vehicle, in which a water-cooled internal combustion engine is integrated with a power transmission, and particularly to a power unit for a small-sized vehicle, which integrally includes a radiator. [0002] [Related Art] A related art power unit mounted on a motorcycle or the like is disclosed, for example, in 'Japanese Patent Publication No. Hei 3-46352. [0003] The above related art power unit, in which a cylinder extends forward substantially in the horizontal direction, is vertically swingably supported by a vehicular frame at the upper portion of a boundary between the cylinder and a crank case; and a radiator is integrally mounted on .a power transmission in such a manner that an air suction plane of the radiator extends along the longitudinal direction of the power transmission. The above document also discloses another embodiment in which a radiator placed at the front of a rear wheel is integrally mounted on a power transmission in such a manner that an air suction plane of the radiator extends along the vehicular width direction. [Problem to ve Solved by the Invention] In the power unit described in the above document, since a radiator is separated from a cooling water jacket for an internal combustion engine, a cooling water passage connecting the radiator to the cooling water jacket is made longer. As a result, there occur inconveniences that a cooling water system is complicated, and the flow resistance of the cooling water passage is increased and thereby a load applied to the cooling water pump is increased. The radiator, separated from a portion for swingably supporting the power unit, is largely affected by a swing motion of the power unit. As a result, the durability of the radiator tends to reduce. The first embodiment of the above document has a problem that since the air suction plane of the radiator extends along the running direction, the cooling performance of the radiator is low because the radiator cannot effectively utilize running wind. The second embodiment of the above document has a problem that since the radiator is disposed at a higher position, the cooling performance of the radiator becomes insufficient because the legs of a rider block a cooling wind suction port which is provided in the rear cover in front of the radiator. "["Means' for Solving the Problem- and JL£j£§_c£] To solve the above-described problems, the present invention has been made. Concretely, according to an invention described in claim 1, there is provided an improved power unit for a small-sized vehicle including a water-cooled internal combustion engine, in which the water-cooled internal combustion engine is integrated with a power transmission supporting a rear wheel on its one side, characterized in that the front portion of the power unit is vertically swingably mounted on a vehicular body, and a radiator is integrally provided on the power unit at a position adjacent to a portion for swingably mounting the power unit. xn the invention described in claim 1 having the above configuration, since the radiator is disposed close to a swing portion of the power unit, an inertia force applied to the radiator due to swing motion of the power unit is reduced, so that it is possible to ensure the durability of the radiator for a long time. According to an invention described in claim 2, since the cooling water jacket in the vicinity of the cylinder head is close to the radiator, a cooling water passage connecting the radiator to the cooling water jacket is shortened, so that a cooling water system is simplified, and the flow resistance of the cooling water passage is reduced and thereby the load applied to a cooling water pump becomes small. This is effective to miniaturize the cooling water pump. According to an invention described in claim 3, since running wind is not obstructed by a front cover or legs of a rider but is sufficiently introduced to the radiator, it is possible to obtain a high cooling performance of the radiator. [0013] Hereinafter, one embodiment of the inventions described in claims 1 to 3 will be described with reference to Figs. 1 to 7. The present invention relates to a power unit for a small-sized vehicle comprising a water-cooled internal combustion engine, in which said water-cooled internal combustion engine is integrated with a power transmission supporting a rear wheel on its one side, characterized in that the front portion of said power unit is vertically swingably mounted on a vehicular body, and a radiator is integrally provided on said power unit at a position adjacent to a portion for swingably mounting said power unit. [Brief Description of the Drawings ] ^•v [Fig. 1] A schematic side view of a scooter on which a power unit according to one embodiment of the present invention is mounted. [Fig. 2] A perspective view of the power unit 1 shown in Fig. 1. [Fig. 3] A side view of the power unit 1 shown in Fig. 1. [Fig. 4] A vertical plan view of Fig. 3. [Fig. 5] A front view seen from the arrow V of Fig. 3. [Fig. 6] A rear view seen from rear to front in Fig. 1. [Fig. 7] An enlarged vertical sectional view of an essential portion of Fig. 6. [Fig. 8] A front view of another embodiment of the present invention. [Fig. 9] A side view of further embodiment of the present invention. [Fig. 10] A vertical plan view taken on line X-X of Fig. 7. A power unit 1 mounted in a scooter-type motorcycle 0 is composed of a push rod/over head valve type four-stroke/one-cycle (generally called four-cycle) single cylinder water-cooled internal combustion engine 2, a V-belt type continuously variable transmission 3, and a gear speed reducer 4. The power unit 1 is divided into right and left crank cases 6 and 5, a cylinder block 7, a cylinder head 8, and a cylinder head cover 9. The cylinder block 7 is overlapped onto the front ends of the crank cases 6 and 5 in such a manner that the axis of a cylinder bore 20 of the cylinder block 7 extends forward substantially in the horizontal direction. The cylinder head 8 and the cylinder head cover 9 are sequentially overlapped onto the front portion of the cylinder block 7. These crank cases 6 and 5, cylinder block 7, cylinder head 8, and cylinder head cover 9 are integrated with each other. As shown in Fig. 1, a rear fork pivot 11 is formed on a main shaft 10 of the scooter type motorcycle Oy/and a supporting bracket 13 integrated with the lower side/of the front portion of the cylinder head 8 is vertically swingably mounted on the rear fork pivot 11 via link 12. A right damper 90 is interposed between a rear frame 14 integrally extending obliquely rearward, upward from the rear end of the main frame 10 and a rear axle pivotably supporting portion 15 rotatably fitted around a rear axle 59 to be described later; .and a left damper 92 is interposed between the rear frame 14 and a bracket 91 of the crank case 6. In this way, the power unit 1 is mounted on the main frame 10 in such a manner as to be vertically swingable with respect to the supporting bracket 13. The left damper 92 is of a usual damper structure, and has a bracket 93 at its upper end. Meanwhile, the right damper 90 has an upper bracket 94 at its upper end; outer and inner covers 95 and 96 in which a coil spring 97 is interposed; a cushion lower bracket 98 integrated with the inner cover 96; a damper rod 99 screwed with the cushion lower bracket 98; a stopper rubber 100 fitted around the lower end portion of the damper rod 99; and a bearing 101 fitted in the rear axle pivotably supporting portion 15 at the lower end of the cushion lower bracket 98. The rear axle 59 is fitted in the bearing 101, and the right end, projecting from the bearing 101, of the rear axle 59 is screwed with a nut 102. In this way, the rear axle 59 is pivotably supported by the rear axle pivotably supporting portion 15 at the lower end of the cushion lower bracket 98 via the bearing 101. A small-diameter cylindrical portion 98a is formed at the upper end of the cushion lower bracket 98, and the lower end of the coil spring 97 is loosely fitted around the small-diameter cylindrical portion 98a of the cushion lower bracket 98. A steering handle 17 is integrally provided on the upper end of a handle shaft 16 which is pivotably supported by the front end of the main frame 10 in such a manner as to be turnable right and left. A front wheel 18 is pivotably supported by the lower end of the handle shaft 16, and a rear wheel 19 is integrally provided on the right end of the rear axle 59 described later. As shown in Figs. 3 and 4, a piston 21 is slidably fitted in the cylinder bore 20, and a crank shaft 22 is pivotably supported by the right and left crank cases 6 and 5. Both the ends of a connecting rod 25 are rotatably supported by the piston 21 and the crank shaft 22 via a piston pin 23 and a crank pin 24, respectively. The reciprocation of the piston 21 rotates the crank shaft 22. An intake port 27 and an exhaust port 28 communicated to a combustion chamber 26 provided at the vertex of the cylinder bore 20 are formed in the cylinder head 8. An intake valve 29 and an exhaust valve 30 are openably/closably provided in the intake port 27 and the exhaust port 28, respectively. A rocker shaft 31 is arranged adjacently to the vertexes of each of the intake valve 29 and the exhaust valve 30. A rocker arm 32 is rockably supported by the rocker shaft 31. One end of the rocker arm 32 is abutted on the vertexes of each of the intake valve 29 and the exhaust valve 30. A cam shaft 33 rotated at a rotational speed being one-half that of the crank shaft 22 is magnetically connected to a rotational shaft 37 (not shown) of a cooling water pump 36 described later. A valve lifter 34 is abutted on the cam shaft 33, and a push rod 35 is interposed between the other end of the rocker arm 32 and the valve lifter 34. In this way, the intake valve 29 and the exhaust valve 30 are opened and closed one time per two turns of the crank shaft 22. A discharge port (not shown) of the cooling water pump 36 is connected to a cooling water jacket 38 provided around the combustion chamber 26 via a cooling water passage (not shown) of the water-cooled type internal combustion engine 2. As shown in Fig.. 5, mounting plates 40 for mounting a radiator 39 are attached to the supporting bracket 13 integrated with the cylinder head 8, and the radiator 39 is integrally mounted on the supporting bracket 13 with bolts 41 which pass through the mounting plates 40 and which are screwed in the supporting bracket 13. Insertion type joints 66 provided at the upper ends of right and left cooling water tanks 45 and 44 are inserted, via 0-rings 67, in cooling water passages 43 and 42 vertically passing through the supporting bracket 13, respectively. The cooling water passages 43 and 42 are respectively communicated to the right and left cooling water tanks 45 and 44 which are connected to each other via cooling water conduits 46 extending right and left in the horizontal direction. A number of radiating fins 47, each standing along a vertical plane, are mounted to the cooling water conduits 46 in such a manner as to be spaced from each other at specific intervals. The upper ends of the cooling water passages 43 and 42 are connected to a suction port (not shown) of the cooling water pump 36 and the cooling water jacket 38 via communicating pipes 49 and 48, respectively. A radiator cap 50 is connected to the left cooling water tank 44, and cooling water is poured in the cooling water tank 44 from the radiator cap 50. A thermostat (not shown) is interposed at a connection portion between the cooling water jacket 38 and the communicating pipe 49. As shown in Fig. 4, a drive V-pulley 52 containing a centrifugal weight 51 is provided at the right end of the crank shaft 22, and a driven V-pulley 54 and a driven shaft 53 are rotatably supported by the rear portions of the right and left crank cases 6 and 5, respectively. An endless V-belt 55 is provided between the drive V-pulley 52 and the driven V-pulley 54, to constitute the V-belt type continuously variable transmission 3. As the rotational speed of the crank shaft 22 is increased, the winding radius of the drive V-pulley 52 is increased by the centrifugal force of the centrifugal weight 51, whereby the speed-change ratio is continuously reduced. A centrifugal clutch 56 is interposed between the driven shaft 53 and the driven V-pulley 54, and a pinion gear 57 formed at the left portion of the driven shaft 53 meshes with an output gear 60 of the rear axle 59 via an internal speed-change gear 58, to constitute the gear speed reducer 4. When the driven V-pulley 54 is rotated at a rotational speed over a specific value, the output of the water-cooled internal combustion engine 2 is transmitted to the rear wheel 19 integrated with the rear axle 59 via the V-belt type continuously variable transmission 3 and the gear speed reducer 4. In addition, as shown in Fig. 4, a generator 61 serving as a starter is provided at the left end of the crank shaft 22, and as shown in Fig. 1, a fuel tank 63 is disposed under a step floor 62. In the scooter-type motorcycle 0 according to the embodiment shown in Figs. 1 to 7 having the above configuration, like a usual scooter including a V-belt type continuously variable transmission, even when the water-cooled type internal combustion engine 2 is started, the output of the water-cooled internal combustion engine 2 is not transmitted to the rear wheel 19; however, as the water-cooled type internal combustion engine 2 is accelerated, the centrifugal clutch 56 is turned into an connected state to thereby move forward the scooter-type motorcycle 0, and as the rotational speed of the water-cooled type internal combustion engine 2 is increased, the speed of the scooter-type motorcycle 0 is increased. If the temperature of cooling water in the cooling water jacket 38 is equal to or less than a specific temperature when the water-cooled type internal combustion engine 2 is started, the thermostat (not shown) is left turned off, the cooling water in the cooling water jacket 38 doesn't flow in the radiator 39 at all. However, as the temperature of the cooling water in the cooling water jacket 38 is raised, the thermostat is turned on, and the cooling water flows from the discharge port of the cooling water pump 36 into the cooling water jacket 38. The cooling water, which is heated at a high temperature in the cooling water jacket 38, is discharged to the cooling water tank 45 via the cooling water passage 43, and during flowing from the cooling water tank 45 to the cooling water tank 44 via the cooling water conduits 46, the cooling water is cooled by heat-radiation via the radiating fins 47 in contact with running wind. The cooling water thus cooled is then returned from the cooling water tank 44 to the suction port of the cooling water pump 36 via the cooling water passage 42 and the communicating pipe 48. In this way, cooling water can be continuously circulated. Since the radiator 39 is disposed on the lower side of the front portion of the cylinder head 8 of the water-cooled type internal combustion engine 2 in such a manner as to project forward therefrom, running wind flowing near the fuel tank 63 under the step floor 62 is not blocked by a rear cover 64 of the scooter type motorcycle 0 but smoothly passes between the radiating fins 47 of the radiator 38. This is effective to enhance the cooling performance of the radiator 39. Even if the power unit 1 is vigorously swung in the vertical direction due to irregularities of a road surface upon running of the scooter-type internal combustion engine 2, the radiator 39 is not applied with a reciprocating inertia force so much because it is disposed close to the supporting bracket 13 functioning as the center of swing motion of the power unit 1. As a result, it is possible to enhance the durability of the radiator 39. Further, since the flow state of running wind to the radiator 39 is substantially kept constant, it is possible to improve the cooling stability of the radiator 39. •me left end of the rear frame 14 is connected to the bracket 91 of the crank case 6 of the power unit 1 via the left damper 92 and the right end of the rear frame 14 is connected to the rear axle 59 via the right damper 90 and the cushion lower bracket 98 and the bearing 101 which are integrated with the inner cover 96 of the right damper 90, and accordingly, the power unit 1 is bilaterally supported, so that the supporting bracket 13 provided on the front portion of the power unit 1 is not applied with an excessive force. As a result, the power unit 1 can be stably swung in the vertical direction. Also the cushion lower bracket 98 is integrally connected to the inner cover 96 of the right damper 90 and the damper rod 99 is integrally screwed in the cushion lower bracket 98 and further the rear axle 59 is rotatably supported by the cushion lower bracket 98 via the bearing 101, and accordingly, the structure of the right damper is simplified. This is effective to make small the size and weight, reduce the number of parts, and improve the assembling process of the right damper, and hence to significantly reduce the manufacturing cost thereof. Further, since the lower end of the coil spring 97 is loosely fitted around the small-diameter cylindrical portion 98a of the cushion lower bracket 98, the coil spring 97 is stably supported by the cushion lower bracket 98. The mounting plates 40 are directly abutted on the supporting bracket 13 in the embodiment shown in Figs. 1 to 7; however, as shown in Fig. 8, relatively soft rubbers 65 may be interposed between the supporting bracket 13 and the mounting plates 40 before the joints 66 provided at the upper ends of the cooling water tanks 45 and 46 are inserted in the cooling water passages 42 and 43 via the 0-rings 67, respectively. With this configuration, since vibration of the water-cooled internal combustion engine 2 at the connecting portions between the cooling water passages 42 and 43 and the cooling water tanks 44 and 45 is cushioned, it is possible to significantly relax stress applied to the connecting portion of the radiator. While the V-belt type continuously variable transmission 3 is used in the embodiment shown in Figs. 1 to 8, it may be replaced with a gear transmission 70 as shown in Figs. 9 and 10. A power unit 1 shown in Figs. 9 and 10 includes a magnetic coupling 71 for magnetically coupling a cam shaft 33 with a rotor 36a of a cooling water pump 36. As shown in Fig. 9, an output gear 72 integrated with the crank shaft 22 is connected to a main shaft 74 of a gear transmission 70 via an intermediate gear 73 including a speed-change clutch (not shown); the main shaft 74 is switchably connected to a counter shaft 76 via a speed-change gear train 75; and the counter shaft 76 is connected to the rear axle 59 via a gear 77. Further, a shift fork 78 is connected to each gear of the speed-change gear train 75 of the counter shaft 76 and the main shaft 74. Such a shift fork 78 is switchably driven by a shift drum 79. The shift drum 79 is connected to a shift motor 81 via a shift mechanism 80 which is shifted up or down one step by one, by intermittently rotation of the shift motor 81. Further, a radiator 82 includes upper and lower cooling water tanks 83 and 84 communicated to each other via cooling water conduits (not shown). A number of radiating fins 85 arranged in the vertical direction are fitted to the cooling water conduits. In the embodiment shown in Figs. 9 and 10 having the above configuration, the gear transmission 70 can be shifted up or down one step by one, by shift-up or shift-down operation. Also, when a thermostat 86 is turned on, the cooling water heated in the cooling water jacket 38 flows in the cooling water tank 83 via the communicating pipe 49, and during flowing downward in the cooling water conduits (not shown) from the cooling water tank 83, the cooling water is cooled via the radiating fins 85 in contact with running wind. Then, the cooling water flows in the cooling water tank 84 and is sucked in the suction port of the cooling water pump 36 through the communicating pipe 48. After being pressurized by the cooling water pump 36, the cooling water is returned again to the cooling water jacket 38. In this way, the cooling water can be circulated in the cooling water system. Even in this embodiment, the radiator 82 arranged in the vicinity of the supporting bracket 13 is not affected by vertical swing, of the power unit 1 so much. The radiator 82 also exhibits a high cooling performance because it sufficiently receives running wind blowing from the front of the vehicle. While the above embodiments have been described using the scooter-type motorcycle as a small-sized vehicle, the present invention can be applied to a saddle type cycle car or a buggy for driving on a rough road. [Explanation of Symbols] 0: scooter type motorcycle, 1: power unit, 2: water-cooled type internal combustion engine, 3: V-belt type continuously variable transmission, 4: gear speed reducer/ 5, 6: crank case, 7: cylinder block, 8: cylinder head, 9: cylinder head cover, 10: main frame, 11: rear fork pivot, 12: link, 13: supporting bracket, 14: rear frame, 15: rear axle pivotably supporting portion, 16: handle shaft, 17: steering handle, 18: front wheel, 19: rear wheel, 20: cylinder bore, 21t piston, 22: crank shaft, 23: piston pin, 24: crank pin, 25: connecting rod, 26: combustion chamber, 27: intake port, 28: exhaust port, 29: intake valve, 30: exhaust valve, 31: rocker shaft, 32: rocker arm, 33: cam shaft, 34: valve lifter, 35: push rod, 36: cooling water pump, 37: rotating shaft, 38: cooling water jacket, 39: radiator, 40: mounting plate, 41: bolt, 42, 43: cooling water passage, 44, 45: cooling water tank, 46: cooling water conduit, 47: radiating fin, 48, 49: communicating pipe, 50: radiator cap, 51: centrifugal weight, 52: drive V-pulley, 53: driven shaft, 54: driven V-pulley, 55: endless V-belt, 56: centrifugal clutch, 57: pinion gear, 58: intermediate speed change gear, 59: rear axle, 60: output gear, 61: generator serving as starter, 62: step floor, 63: fuel tank, 64: rear cover, 65: rubber, 70: gear transmission, 71: magnetic coupling, 72: output gear, 73: intermediate gear, 74: main shaft, 75: speed-change gear train, 76: counter shaft, 77: gear/ 78: shift fork, 79: shift drum, 80: shift mechanism, 81: shift motor, 82: radiator, 83, 84: cooling water tank, 85: radiating fin, 86: thermostat, 90: right damper, 91: bracket, 92: left damper, 93: bracket, 94: upper bracket, 95: outer cover, 96: inner cover, 97: coil spring, 98: cushion lower bracket, 99: daniper rod, 100: stopper rubber, 101: bearing, 102: nut. WE CLAIM: 1. A power unit for a small-sized vehicle comprising a water-cooled internal combustion engine, in which said water-cooled internal combustion engine is integrated with a power transmission supporting a rear wheel on its one side, characterized in that the front portion of said power unit is vertically swingably mounted on a vehicular body, and a radiator is integrally provided on said power unit at a position adjacent to a portion for swingably mounting said power unit. 2. A power unit for a small-sized vehicle comprising a water-cooled internal combustion engine as claimed in claim 1, wherein a cylinder of said water-cooled internal combustion engine extends forward obliquely or horizontally, and a portion in the vicinity of a cylinder head of said internal combustion engine to swingably mounted on the vehicular body. 3. A power unit for a small-sized vehicle comprising a water-cooled internal combustion engine as claimed in claim 2, wherein said radiator is provided on the lower side of said portion, mounted on the vehicular body, in the vicinity of said Cylinder head. 4. A power unit far a small-sized vehicle substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

Documents:

3800-del-1998-abstract.pdf

3800-del-1998-claims.pdf

3800-del-1998-correspondence-others.pdf

3800-del-1998-correspondence-po.pdf

3800-del-1998-description (complete).pdf

3800-del-1998-drawings.pdf

3800-del-1998-form-1.pdf

3800-del-1998-form-13.pdf

3800-del-1998-form-19.pdf

3800-del-1998-form-2.pdf

3800-del-1998-form-3.pdf

3800-del-1998-form-4.pdf

3800-del-1998-form-6.pdf

3800-del-1998-gpa.pdf

3800-del-1998-petition-137.pdf

3800-del-1998-petition-138.pdf

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