Abstract:
An outboard motor comprises an engine cover having an air intake opening for taking in air, an engine disposed in the engine cover, and an AC generator disposed in the engine cover for generating electricity to drive the engine. A cooling air guide member is disposed in the engine cover for guiding the air taken in by the air intake opening towards the AC generator. The cooling air guide member has a bottom wall, a pair of side walls extending upwardly from opposite side edges of the bottom wall, and an opening extending through the bottom wall so that the air taken in by the intake opening is guided by the side walls and the bottom wall to flow through the opening to cool the AC generator.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an improvement in an outboard motor, and in particular to a structure for cooling an AC generator provided to an engine of the outboard motor. 
     BACKGROUND OF THE INVENTION 
     Outboard motors include engines, auxiliary devices disposed in the vicinity of the engines, and engine covers covering the engines and the auxiliary devices. Within the engine covers, there are also disposed AC generators. 
     The engines have vertically extending crankshafts. Cylinder heads, intake systems, and exhaust systems are disposed in rear parts of space formed within the engine covers. The AC generators are provided in front of the engines. 
     The crankshafts drive the generators by transmitting their motive powers thereto by means of belts and pulleys extending around the belts. 
     The outboard motors discussed above are known from, for example, Japanese Patent Laid-Open Publication No. HEI 6-33790. A generator disclosed in the publication is disposed adjacent a front part of an engine. The generator undesirably emits heat when producing electricity. The generator and its associated electronic devices are adversely affected by the heat produced by the generator. The generator needs to be cooled down. 
     Belts and pulleys extending around the belts to drive the generator are unavoidably positioned above the engine because a crankshaft of the engine is oriented vertically. This requires the generator to be positioned at a high level in front of the engine. An engine cover is disposed to cover upper parts of the engine and the generator. The generator and the engine cover have only a very small space formed therebetween. 
     The generator thus arranged can be cooled down with decreased efficiency. It has been propose to provide a large space between the generator and the engine cover. However, providing such a larger space increases a height of the engine cover. The outboard motor having such an engine cover of increased height is undesirably rendered large in size. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an outboard motor including a generator-cooling structure disposed in a small space formed above a generator of the outboard motor, such that the generator is advantageously cooled down. 
     According to one aspect of the present invention, there is provided an outboard motor comprising: an engine having a vertically extending crankshaft; an AC generator disposed adjacent the engine; a cooling air guide member disposed above the engine, the cooling air guide member having an opening formed at a portion thereof opposed to the AC generator; and an engine cover covering the engine, the AC generator, and the cooling air guide member. 
     The generator-cooling structure is disposed above the generator. The structure has the opening formed at a portion thereof opposed to the generator. Air for cooling the generator flows through the opening to cool the generator. 
     In a preferred form of the present invention, the cooling air guide member is recessed to form a space extending in a front-and-rear direction of the outboard motor, and the cooling air guide member includes a bottom part having the opening formed therein. In a further preferred form of the present invention, the AC generator is disposed adjacent a front part of the engine. Preferably, an outboard motor further comprises an air intake silencer disposed above the engine, the air intake silencer extending in a front-and-rear direction of the engine and having the cooling air guide member attached to a front part thereof. 
     The structure is recessed to form the space extending in the front-and-rear direction of the outboard motor. The structure includes the bottom part having the opening formed therein. 
     The structure of recessed configuration provides the space or a duct-shaped passage way through which the air for cooling the generator flows, even if the former is positioned in a small space between the generator and the engine cover. This arrangement eliminates the need for an engine cover having a height larger than required. It therefore becomes possible to render the outboard motor compact. It also becomes possible to provide an improved freedom to design the outboard motor. 
     Since the structure is attached to the front part of the silencer disposed above the engine, there is no need to provide the engine with particular components such as stays for attaching of the structure to the engine. This facilitates providing the structure to the outboard motor. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A certain preferred embodiment of the present invention will hereinafter be described in detail, by way of example only, with reference to the accompanying drawings, in which: 
     FIG. 1 is a cross-sectional view of an upper part of an outboard motor; 
     FIG. 2 is a perspective view of an air intake silencer of the outboard motor; 
     FIG. 3 is a top plan view of the silencer; 
     FIG. 4 is a cross-sectional view taken along line  4 — 4  of FIG. 3; and 
     FIG. 5 is a top plan view showing, partly in cross-section, the upper part of the outboard motor; 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, an outboard motor  1  includes an engine  6  and auxiliary devices disposed around the engine  6 . The engine  6  and the devices are covered with an engine cover  2 . The engine cover  2  includes a top cover  3  and a front cover  4 . The top cover  3  is a rear part of the engine cover  2 . The front cover  4  extends forwardly from the top cover  3 . The front cover  4  has slits  4   a  formed in a lower part thereof. The slits  4   a  are arranged to take in air from outside the outboard motor  1 . An under cover  5  is mounted under the engine cover  2 . An extension case (not shown) is disposed below the under cover  5 . Mounted below the extension case is a gear case including a screw. 
     The engine  6  includes a cylinder block  7  disposed centrally thereof. The cylinder block  7  includes its skirt portion  7   c  having a crankcase  8  disposed forwardly thereof. Cylinder heads  9 ,  9  are disposed behind the cylinder block  7 . Cylinder head covers  10 ,  10  are positioned behind the cylinder heads  9 ,  9 . The engine  6  further includes a vertically extending crankshaft  11 . Within the cylinder block  7 , there are disposed two sets of three cylinders  7   a  each horizontally oriented. The cylinders  7   a  of each set are vertically juxtaposed. Each cylinder  7   a  has a piston  7   b  disposed therein. The piston  7   b  is connected via a connecting rod to the crank shaft  11 . Formed in the cylinder head  9  are combustion chambers  9   a  provided in correspondence to the number of the cylinders  7   a.    
     The engine  6  is a V-six engine (see FIG.  5 ). More specifically, the cylinder block  7  has the horizontally oriented six cylinders  7   a  three of which are disposed on one of right and left sides thereof. The other three cylinders are disposed on the other side. 
     Behind the cylinder heads  9 ,  9 , there is positioned an intake manifold  12  extending vertically. An outside air intake guide member  13  for taking in air from outside the outboard motor  1  is provided behind the intake manifold  12 . 
     A camshaft pulley  14  is positioned above the cylinder head  9 . A guide pulley  15  is located above a rear part of the cylinder block  7 . Above the skirt portion  7   c , there is disposed a first driving pulley  16  to be driven by the crankshaft  11 . A timing belt  17  extends around the pulleys  14 ,  16 . The crankshaft  11  drives a camshaft via the timing belt  17 . 
     The engine  6  has an AC generator  18  adjacent a front part thereof. In other words, the generator  18  is attached to a front side of an upper portion of the crankcase  8  forming the front part of the engine  6 . The generator  18  includes a vertically extending drive shaft. A body  18   a  of the generator  18  includes an upper part, an intermediate part, and a lower part all of which have vertically elongated slits  19  formed therein. 
     On an upper surface of the generator  18 , there is provided a driven pulley  20  for driving the generator  18 . Provided at an upper part of the crankshaft  11  is a second driving pulley  21 . The second driving pulley  21  is positioned above the first driving pulley  16  in a coaxial relation thereto. A timing belt  22  extends around the pulleys  20 ,  21 . The crankshaft  11  drives the generator  8  by transmitting a motive power thereto via the timing belt  22  and pulleys  20 ,  21 . 
     Above these pulleys and timing belts positioned above the engine  6 , there is disposed an air intake silencer  30  of box-shaped configuration. The silencer  30  extends in a front-and-rear direction of the engine  6 . 
     Referring to FIG. 2 to FIG. 4, the silencer  30  will be described hereinbelow. 
     The silencer  30  includes upper and lower halves  31 ,  32  joined together. The halves  31 , 32  are of small thickness. 
     A throttle valve device  23  is disposed proximate and above the cylinder heads  9 ,  9 . The device  23  has an intake port formed upstream thereof. The intake port is connected through a grommet  24  to a cylindrical intake connecting duct  33 . The duct  33  is positioned centrally of a rear side of the lower half  32 . The port  33  projects backwardly from the rear side of the lower half  32 . 
     Outside air intake ducts  34 ,  34  project backwardly from at right and left ends of a rear part of the silencer  30 , respectively. The ducts  34 ,  34  are slightly inclined outwardly. The respective halves  31 ,  32  have upper and lower recessed portions  31   a ,  32   a  provided in symmetric relation to each other. 
     Joined or attached to a front part  30   a  of the silencer  30  is a cooling air guide member  40  for cooling the generator  18 . The guide member  40  is positioned above the generator  18  and extends in the front-and-rear direction of the engine  6 . 
     The guide member  40  is widened at a rear part  40   a  thereof. A front part of the guide member  40  is reduced in width. The front part of the guide member  40  has a flat projection portion  41  protruding therefrom. 
     The guide member  40  is smaller in width than the silencer  30 . The rear part  40   a  is fixedly attached via screws  35 ,  35  to boss portions  30   b ,  30   b  provided rightwardly and leftwardly of the front part  30   a  of the silencer  30 . 
     At both right and left sides of the guide member  40 , there are provided erected walls  42 ,  42  extending vertically. The erected walls  42 ,  42  are reduced in height towards a front end thereof. A bottom part  43  of the guide member  40  is formed between the walls  42 ,  42 . The bottom part  43  is contiguous with bottoms of the walls  42 ,  42 . The guide member  40  is recessed or U-shaped to form a space extending in a front-and-rear direction of the outboard motor  1 . More specifically, the walls  42 ,  42  and the bottom part  43  cooperate to provide a recess as viewed in front elevation. That is, the guide member  40  is of U-shaped cross-section. Upper parts  40   d ,  40   d  extend outwardly from tops of the walls  42 ,  42 . 
     The upper parts  40   d ,  40   d  have sidewalls  40   b ,  40   b extending downwardly from outer edges thereof. The wall  42 , the upper parts  40   d ,  40   d , and the side wall  40   b  define a space  46  in cooperation with each other. The side walls  40   b ,  40   b  extends further downwardly to terminate at a level below the bottom part  43 . Lower edges  40   c ,  40   c  are formed at such a level. 
     The bottom part  43  has an opening  44  formed in a rear half portion thereof. The opening  44  is elongated transversely of the guide member  40 . The bottom part  43  also has an opening  45  formed at a front half portion thereof. The front half portion of the bottom part  43  is opposed to the generator  18 . The opening  45  is elongated in a front-and-rear direction of the guide member  40 . The aforementioned silencer  30  and guide member  40  are made from synthetic resin. 
     As shown in FIG. 1, the silencer  30  is disposed above the engine  6 , or the timing belts  17 ,  22  and the pulleys  14 ,  15 ,  16 . 
     The guide member  40  extending forwardly from the silencer  30  is positioned above the belt  22  and the pulley  20 . The guide member  40  surrounds the belt  22  and the pulley  20 . A stay  25  extends through the opening  44  formed at the rear half portion of the bottom part  43 , as shown in FIG.  5 . The opening  45  is positioned above the pulley  20 . 
     A control cable  26  is provided for controlling an amount by which a throttle valve of the throttle valve device  23  is opened. The control cable  26  extends along one side of an upper surface of the silencer  30  to the rear part  40   a  of the guide member  40 . The cable  26  then goes downwardly from the rear part  40   a  of the guide member  40  alongside the crankcase  8  to the front side of the outboard motor  1 . Reference numeral  27  denotes an oil filter. An exhaust pipe  28  extends downwardly from the outboard motor  1 . A stern bracket  29  is interposed between the under cover  5  and an extension case (not shown). 
     The duct  33  has a filter  30   c  provided upstream thereof. The filter  30   c  removes a mist from a blow-by gas. 
     The top cover  3  includes a recessed portion  3   a . An operator can cause the outboard motor  1  to pivot upwardly, gripping the recessed portion  3   a . A slit  3   b  for taking in air form outside the outboard motor  1  is formed below the top cover  3 . A cover  60  has its upper half part covering a front part of the generator  18 . The cover  60  includes first and second passageways  61 ,  62  formed at a lower half part thereof. The second passageway  62  is provided behind the first passageway  61 . When flowing these passageways  61 ,  62 , a mixture of water and air is separated into the water and the air. 
     Referring to FIG. 5, the V-six engine  6  includes the cylinder block  7 , the right and left cylinder heads  9 ,  9 , and the right and left cylinder head covers  10 ,  10  to provide the V-shaped configuration as viewed in top plan. Reference numerals  28   a ,  28   a  designate right and left exhaust manifolds. In take pipes  12   a ,  12   a  are connected to intake ports of the individual cylinder heads  9 ,  9 . 
     As is apparent from FIG. 5, the generator  18  is positioned below the longitudinally elongated opening  45  of rectangular contour. 
     Description will be made as to how the guide member  40  is operated, with reference back to FIG.  1 . Air outside the outboard motor  1  passes through the slits  4   a  and an opening  4   b  and flows up through the first passageway  61 , as shown by an arrow {circle around (1)}, into a space S formed between an upper part of the front cover  4  and the cover  60 . Part of the air flows downwardly through the second passageway  62  and then is directed upwardly to cool the generator  18 , as indicated by an arrow {circle around (2)}. 
     The air which has passed through the space S flows towards the guide member  40 . The guide member  40  is opened at its front part. The guide member  40  includes the walls  42 ,  42  formed on the right and left sides thereof, and the bottom part  43  positioned between the bottoms of the walls  42 ,  42  such that the guide member  40  is U-shaped as viewed in cross-section. The walls  42 ,  42  and the bottom part  43  thus jointly define the space elongated longitudinally of the guide member  40 . With this arrangement, the air flows through the thus elongated space towards the rear end  40   a.    
     After passing through the space S, the air is directed over the bottom part  43  into the opening  45  formed at the front half portion of the bottom part  43 , as shown by an arrow {circle around (3)}. The air flowing through the opening  45  cools the generator  18 . 
     Although the bottom part  43  has the openings  44 ,  45  formed therein, the former may have formed therein the opening  45  alone. This is because not the opening  44  but the opening  45  helps cool the generator  18 . 
     The present disclosure relates to the subject matter of Japanese Patent Application No. 2001-037603, filed Feb. 14, 2001, the disclosure of which is expressly incorporated herein by reference in its entirety.