Outboard motor

Abstract: An outboard motor according to the present invention has a generator (22). The outboard motor (1) has a first passage (S3, S4) for supplying air from above the generator and a second passage (S7) for supplying air from below the generator, so as to cool the generator. The first and second passages communicate with an air inlet opening (43) provided in a front surface of an engine cover (30) in a position below the generator.

Description: The present invention relates to an outboard motor in which an alternating-current generator or an alternator arranged inside an engine cover can be cooled effectively. Generally, an outboard motor consists of an engine with a crankshaft disposed vertically, auxiliary machinery and equipment for the engine, and an engine cover covering the engine and the auxiliary machinery and equipment for the engine. The engine cover gives the appearance of the outboard motor. To the engine is attached an alternating-current generator or an alternator (hereinafter referred to simply as generator) which is driven by the crankshaft through a belt/pulley mechanism. The generator is one of heat sources, and heat liberated by the generator becomes a cause of increased atmospheric temperature in an engine room defined by the engine cover of the outboard motor. The increased atmospheric temperature in the engine room can lead to increased temperature of intake air, resulting in degradation of engine performance. It is thus preferred to cool the generator. An outboard motor disclosed in, for example, Japanese Patent Laid-Open Publication No. HEI-6-33790, has a generator covered by an engine cover. The generator is, however, provided simply in an engine room and is not cooled. Heat produced by the generator is dissipated in the engine room inside the engine cover, and increases atmospheric temperature in the engine room. Further, in this outboard motor, the generator covered by the cover without being cooled is arranged in the vicinity of a surge tank connected to an intake manifold and a throttle, which may increase temperature of intake air. Furthermore, the generator provided in the outboard motor according to Japanese Patent Laid-Open Publication No. HEI-6-33790 is covered by the cover that is waterproofed. Hot air dissipated by the generator being driven while the engine is driven, is therefore prevented from being released outside even after a stop of the engine, so that atmospheric temperature in the engine room is not decreased. US 5,340,343 A discloses an outboard motor with a flywheel magneto fixed to the upper end of the crankshaft. A rear opening of the casing communicates the atmosphere with the inner side of the casing as an air supply for the engine. The front side of the casing includes an additional opening connected with the carburetor as an auxiliary air intake, but is separated from the magneto by a wall. JP 11-200878 A shows an outboard engine with an air intake opening formed in the rear end of the engine cover distant from the generator which is located adjacent to the front end of the engine. Air flows through the opening, passes the generator from the upper side and is then fed into the engine as combustion air. It is an object of the present invention to provide an outboard motor which can effectively cool a generator attached to an engine. According to an aspect of the present invention, there is provided an outboard motor in accordance with claim 1. The outboard motor comprises: an engine with a crankshaft disposed vertically; a generator disposed on the side of the engine and driven via a belt by the crankshaft, the generator having a plurality of slits in its upper and lower portions for letting cooling air in therethrough; an engine cover defining at least part of an engine room housing the engine, and having a front surface, two side surfaces and a top surface integrated with the two side surfaces; an opening provided in the front surface of the engine cover, positioned below the generator in the engine cover, for establishing communication between the inside of the engine cover and the air outside; a first passage provided in the engine cover, communicating with the opening and extending upwards from the position of the opening, for supplying the air from above the generator; and a second passage extending downwards from the position of an upper portion of the first passage, for supplying the air below the generator. In the outboard motor thus arranged, the first passage for supplying air from above the generator and the second passage for supplying air from below the generator supply cooling air into the upper and lower slits of the generator. The generator being a heat source arranged inside the engine cover of the outboard motor is therefore efficiently cooled. Desirably, a water separation chamber is further formed in a communicating hole between the first passage and the second passage, for making water and drops of water taken in with the air from the opening, fall. In the outboard motor operated on the waves or with water splashes, water and drops of water enter the inside of the engine cover together with air for cooling the generator, taken in through the opening of the front surface of the engine cover. The water and drops of water are separated from the air in the water separation chamber and made to fall, being prevented from reaching the generator with the air. Preferably, the water separation chamber comprises a vertical wall constituting part of a recess having part of the front surface of the engine cover recessed inwards, and a front cover for covering the recess. Since the water separation chamber is formed with the part of the engine cover and the front cover, it can be constructed simply. The front cover is, in an embodiment, for example, screwed to the engine cover in a direction perpendicular to a plane extended between the upper end and the lower end of the front cover. Certain preferred embodiments of the present invention will be described in more detail below, by way of example only, with reference to the accompanying drawings, in which: FIG. 1 is a sectional view illustrating an upper part of an outboard motor according to the present invention; FIG. 2 is an enlarged sectional view illustrating a front part of the outboard motor; FIG. 3 is a sectional view illustrating the flow of air taken in for cooling a generator; and FIG. 4 is a sectional view illustrating the flow of exhaust air heated by the generator after an engine is stopped. In Fig. 1, reference character Fr designates a forward direction of an outboard motor while reference character Rr designates a rearward direction of the motor. As shown in FIG. 1, an outboard motor 1 has in its upper part an engine 2 disposed horizontally. The engine 2 in this embodiment has two cylinder blocks 3 (only one shown in FIG. 1). Each cylinder block 3 has a plurality of cylinders 3a disposed horizontally and arranged vertically. A piston 3b is fitted into each cylinder 3a. A cylinder head 4 is connected to the front end (on the Rr side of the outboard motor 1) of the cylinder block 3. A cylinder head cover 5 is similarly provided at the front end of the cylinder head 4. A crankcase 21 is connected to the rear ends of the cylinder blocks 3 (on the Fr side of the outboard motor 1). The cylinders 3a of the cylinder blocks 3 and the cylinder heads 4 form a plurality of combustion chambers 3c. A skirt 6 housing a crankshaft 6a disposed vertically is integrally formed with rear portions of the cylinder blocks 3. The skirt 6 constitutes generally one-half of a crank room. The crankcase 21 constitutes the other half of the crank room. An oil pan 7 is arranged below the cylinder blocks 3 and skirt 6. In this embodiment, the engine 2 is a V-6 engine with the cylinder blocks 3 arranged in a V configuration in a plan view. The engine 2 is supported on a mounting case 9 provided inside of an under cover 8. An exhaust pipe 4a extends downwards from an exhaust manifold provided on the side of the cylinder head 4. The lower end of the exhaust pipe 4a extends into an extension case (not shown) positioned below the mounting case 9, and discharges exhaust gas. The lower end of the crankshaft 6a is connected to a drive shaft 10 extending vertically. The drive shaft 10 extends through the extension case not shown downwards and is connected to a screw not shown via a gearbox not shown. A stern bracket 11 is provided at a front portion of the mounting case 9. Via the stern bracket 11, the outboard motor 1 is mounted to a stern. An intake manifold 12 is provided rearwards of the cylinder head covers 5 (on the Rr side of the outboard motor 1 in FIG. 1). The intake manifold 12 distributes and supplies fuel to the cylinders of the engine. The intake manifold 12 is connected to a throttle valve device 13 disposed above the cylinder head 4 in the figure. An air intake guide 14 is provided rearwards of the intake manifold 12. The guide 14 is formed independently of the engine cover. An intake silencer 15 is disposed over the top surfaces of the cylinder blocks 3 and the skirt 6 of the engine 2. Above the engine 2, a drive pulley 16 driven by the crankshaft 6a is provided. Above the cylinder heads 4, a camshaft pulley 17 is provided. A timing belt 19 is wound around the pulleys 16 and 17 via a middle pulley 18. On the shaft 16a of the drive pulley 16 driven by the crankshaft 6a, a generator drive pulley 20 is coaxially provided. A belt 24 is wound around the pulley 20 and a driven pulley 23 of the generator 22. At the rear end of the skirt 6 of the engine 2 (on the Fr side of the outboard motor 1), the crankcase 21 is provided. The generator 22 is mounted to an upper part of the crankcase 21 to project forwards in the Fr direction of the outboard motor 1. The surroundings of the engine 2 are covered by the engine cover 30 which defines the engine room ER inside. The engine cover 30 includes a rear surface 30a, two side surfaces not shown (on the right and left sides in the forward direction Fr of the outboard motor 1), a top surface 30b and a front surface 30c, and opens downwards to be joined with the upper end of the under cover 8. In an upper rear surface of the engine cover 30, an air intake opening 31 is provided. The opening 31 is connected to an upper end opening 14a of the air intake guide 14. A lower end opening 14b of the guide 14 faces downwards. A rear part of the top surface 30b including the opening 31 forms a recess 30d set back downwards in a step and is covered with a top cover 32. A space is formed between the top cover 32 and the recess 30d. An air intake slit 33 is formed between a rear end 32a of the top cover 32 and a top part of the rear surface 30a. Air intake slits 34 are formed in a top surface of the top cover 32. An air intake opening and passage for cooling the generator is provided in the front surface 30c of the engine cover 30. In FIG. 2, the generator 22 is fixed between two supporting bosses 21a, 21a in a fork shape extending forwards (to the right in the figure) from an upper part of the crankcase 21, via a stay 22a. The generator 22 has a body 22b which includes, in its upper periphery near the pulley 23 above, a plurality of upper slits 22c for letting cooling air in therethrough, and in its middle periphery a plurality of middle slits 22d for letting cooling air out therethrough, and in its lower periphery a plurality of lower slits 22e for letting cooling air in therethrough. Above the generator 22, is provided a belt cover 25 for covering the driven pulley 23, belt 24 and drive pulley 20. The belt cover 25 has a front part 25a of a semicircular shape in a plan view, which has a first opening 26 in its upper part. The opening 26 is formed with an annular bank 26a standing upright from an upper surface of the belt cover 25. The opening 26 is arranged above the pulley 23 of the generator 22 and inside of the outer periphery of the pulley 23. The generator 22 is placed close to an upper part of the front surface 30c of the engine cover 30. The front surface 30c of the engine cover 30 is formed with a recess 35 set back inwards (in the Rr direction of the outboard engine 1). The recess 35 includes a step 35a lowered in a front part of the top surface 30b of the engine cover 30, a curved part 35b extending forwards from the front part of the step 35 and curving downwards continuously, an upper vertical wall 35c extending downwards from the curved part 35b in the vertical direction, and a lower vertical wall 35d protruding forwards at the vertically middle part of the front surface 30c below the upper vertical wall 35c. A lower end part 35e of the lower vertical wall 35d is bent in an L shape and fitted onto an upper end step 8a of the under cover 8. A mounting wall 35f extends obliquely in a rear upward direction from the rear end of the step 35a as an upper part of the recess 35. The L-shaped lower end part 35e of the lower vertical wall 35d has a mounting wall 35g extending obliquely in a rear upward direction. The step 35a provided in an upper part of the recess 35 has a second opening 36 in a duct shape. The opening 36 is formed with an annular bank 36a serving as a duct, extending upward from a bottom surface 35a' of the step 35a. The opening 36a has a diameter larger than that of the opening 26 directly below provided in a front part of the belt cover 25. The opening 36 and the opening 26 are arranged adjacently to communicate with each other in the vertical direction. An upper vertical wall part 37 constituting the upper vertical wall 35c of the recess 35 is opposed to the front of the generator 22 with a space therebetween. A lower half 37a of the upper vertical wall part 37 extends below the generator 22. A lower vertical wall part 38 constituting the lower vertical wall 35d of the front surface 30c is opposed at its upper part to the front surface of the lower half 37a of the vertical wall part 37 with a space W therebetween. The upper part of the lower vertical wall part 38 opposed to the lower half 37a of the upper vertical wall part 37 is provided with a communicating hole 39 extending therethrough in the cross direction. A gutter 40 in a reverse L shape is projected forwards from the vertically middle part of the upper vertical wall part 37, constituting a ceiling at the upper end of the communicating hole 39. The recess 35 provided in the front surface 30c of the engine cover 30 is covered with a front cover 41. The front cover 41 is L shaped with a curved cross section. At an end part of an upper front part 41a of the front cover 41 extending forwards, is provided a mounting boss 41b slanting rearwards and downwards. The boss 41b is fastened to the upper mounting wall 35f via a screw 42. At a lower end part of a front wall 41d of the front cover 41 extending vertically downwards from a curved part 41c, is provided a mounting boss 41e slanting inwards (rearwards) and downwards. The boss 41e is fastened to the lower mounting wall 35g via a screw 42. As described above, the front cover 41 is mounted on the front surface 30c of the engine cover, to cover the recess 35. The screwed parts of the front cover 41 are substantially perpendicular to a plane extending between the upper end and the lower end of the front cover. A front wall 41d of the front cover 41 has a plurality of openings 43 formed at its lower part 41g. The openings 43 are, in this embodiment, a plurality of slits in a louver shape, arranged in the vertical direction. The upper front part 41a of the front cover 41 covers the upper side of the step 35a including the annular opening 36, to form a space S1 between the upper front part 41a, opening 36 and the surrounding. An uppermost passage S2 made of a space with a narrow width is formed between the inner surface of the curved part 41c of the front cover 41 and the curved part 35b of the engine cover 30. An intermediate passage S3 is formed between an upper half 41f of the front wall 41d and the upper vertical wall 35c (upper vertical wall part 37). The passage S3 is gradually narrowed in the upward direction. A lower passage S4 is formed between a lower part 41g of the front cover 41 and the lower vertical wall 35d (lower vertical wall part 38) spaced rearwards from the lower part 41g. Above the lower passage S4, a communicating passage S5 is formed with the communicating hole 39. The lower half 37a of the upper vertical wall part 37 forming the communicating passage S5 in its set-back position constitutes a bottom wall of the passage S5, serving as a water separation wall. Thus a water separation chamber S6 is formed in front of the lower half 37a, being closed at its upper part with the gutter 40. An inside passage S7 is formed between the front of the generator 22 and the upper vertical wall part 37. As shown in FIG. 1, the cross-sectional area of a passage between the intake opening 31 and the upper opening 14a of the air intake guide 14, corresponding to a substantial intake opening for the engine room, is larger than the cross-sectional area of a passage of the slits 43 formed in the front surface 30c of the engine cover 30, thereby supplying a larger amount of intake air for combustion to the combustion chambers, decreasing the temperature of the intake air. Now the flow of cooling air for the generator caused by air intake is described with reference to FIG. 3. In FIG.3, air is taken from the slits 43 formed in the lower part 41g of the front cover 41 into the lower passage S4 between the lower part 41g of the front wall 41d and the lower vertical wall part 38 of the front surface 30c of the engine cover 30, as shown by arrow 1 ○. The lower passage S4 communicates with the intermediate passage S3 above. The passages S4 and S3 constitute a first passage. The intake air flows upwards in the direction of arrow 2 ○, passes through the uppermost passage S2, and through the opening 36 and the opening 26 as shown by arrow 3 ○, flows downwards from above the pulley 23 of the generator 22. Since the diameter of the opening 26 is smaller than that of the duct-shaped opening 36, the cooling air flows through the gap therebetween into the outside of the front part 25a of the belt cover 25 in a semicircular roof-like shape, as shown by arrow 4 ○. The cooling air is taken from the upper slits 22c for letting cooling air in therethrough, arranged in the upper periphery of the generator 22, into the inside of the generator 22, thereby cooling the generator 22. Exhaust air after cooling is let out from the slits 22d formed in the middle periphery of the generator 22 as shown by arrow 5 ○. Part of air taken into the lower passage S4 in the first passage goes through the passage in front of the lower half 37a of the upper vertical wall part 37 through the communicating passage S5 constituted with the communicating hole 39, turns around a lower part of the lower half 37 as shown by arrow 6 ○, and goes up a second passage constituted with the inside passage S7 along the upper vertical wall part 37 as shown by arrow 7 ○. The cooling air going up as shown by arrow 7 ○ is taken from the lower slits 22e of the generator 22 above, into the inside of the generator 22 as shown by arrow 8 ○. Exhaust air after cooling is let out from the slits 22d in the middle section as shown by arrow 5 ○. Since the outboard motor is used on the sea or water, it may let water or drops of water in while letting air in from the openings 43 because of turbulence or the like. Water and drops of water in air taken into the lower passage S4 are not conveyed upward but are taken from the communicating hole 39 (communicating passage S5) provided in a lower level into the space in front of the lower half 37a of the upper vertical wall part 37. The lower half 37a blocks the flow thereof. The space formed with the lower half 37a serves as the water separation chamber S6 and makes the invading water and drops of water fall as shown by arrow 9 ○, thereby eliminating them from the cooling air. Thus, water and drops of water included in air taken into the outboard motor 1 are removed and do not reach the generator 22 with the cooling air for the generator 22. Now the flow of hot air after the generator 22 stops operating is described with reference to FIG. 4. Hot air produced by the generator 22 in operation is emitted around the generator 22 when the generator 22 stops. Since the belt cover 25 covering the upper side of the pulley 23 of the generator 22 has the opening 26 in a position above the generator 22, hot air emitted by the generator 22 goes up as shown by arrow 1 ○ and is discharged upwards from the annular opening 36 of the engine cover 30 above. Thus, since the upper portion of the generator is not completely covered, unlike a conventional outboard motor, hot air is not stagnated inside the belt cover 25. Hot air discharged upwards from the openings 26, 36 as shown by arrow 1 ○ flows from the space S1 through a thin communicating passage S8 in an upper portion of the uppermost passage S2 into the passage S2, passes the intermediate passage S3, and then flows into the lower passage S4 or flows out inside the engine cover 30 as shown by arrow 3 ○ through the communicating passage S5, thereby cooling the generator speedily after a stop of its operation. In the present invention, since the duct-shaped opening 36 is arranged in a higher position than the bottom surface 35a' of the step 35a, water invasion into the opening 36 is prevented, and water invasion from the opening 26 formed in the belt cover 25 into the inside of the outboard motor 1 is prevented. An outboard motor according to the present invention has a generator (22). The outboard motor (1) has a first passage (S3, S4) for supplying air from above the generator and a second passage (S7) for supplying air from below the generator, so as to cool the generator. The first and second passages communicate with an air inlet opening (43) provided in a front surface of an engine cover (30) in a position below the generator.

Claims: An outboard motor (1) comprising: an engine (2) with a crankshaft (6a) disposed vertically; an alternating-current generator (22) disposed on the side of said engine and driven via a belt by said crankshaft, said generator having a plurality of slits (22c, 22e) in its upper and lower portions for letting cooling air in therethrough; an engine cover (30) defining at least part of an engine room (ER) housing said engine, and having a front surface (30c), two side surfaces and a top surface (30b) integrated with the two side surfaces; characterised by an opening (43) provided in the front surface of said engine cover, positioned below said generator in said engine cover, for establishing communication between the inside of said engine cover and the air outside; a first passage (S3, S4) provided in said engine cover, communicating with said opening and extending upwards from the position of said opening, for supplying the air from above said generator; and a second passage (S7) extending downwards from the position of an upper portion of said first passage, for supplying the air below said generator. An outboard motor as set forth in claim 1, wherein: a water separation chamber (S6) is formed in a communicating hole (S5) between said first passage (S3, S4) and said second passage (S7), for making water and drops of water taken in with the air from said opening (43), fall. An outboard motor as set forth in claim 2, wherein: said water separation chamber (S6) comprises a vertical wall (37) constituting part of a recess (35) having part of said front surface (30c) of said engine cover (30) recessed inwards, and a front cover (41) for covering said recess.

Inventors: NEMOTO HIDEKI, RINZAKI SHOICHI, NEMOTO, HIDEKI, RINZAKI, SHOICHI
Applicants: HONDA MOTOR CO LTD, HONDA GIKEN KOGYO KABUSHIKI KAISHA
Application year: 2001
Main classification: F02B61
IPC codes: F01P1, F02B61, F02B75