Patent Publication Number: US-9429068-B2

Title: Engine generator assembly

Description:
TECHNICAL FIELD 
     The present invention relates to an engine generator. 
     BACKGROUND ART 
     Conventionally, in consideration of use of an engine generator in a city area or at night, measures against noise are taken on the engine generator. For example, in an engine generator of the Patent Literature 1, as a measure against noise, an engine and a generator are covered by a cover. Accordingly, sound generated in the cover (for example, engine sound, intake sound of an air cleaner and the like) is interrupted with the cover, whereby noise can be reduced. 
     However, in the engine generator of the Patent Literature 1, though the sound generated in the cover is interrupted with the cover, the cover tends to be filled with heat so as to raise temperature therein. Then, in the engine generator of the Patent Literature 1, as measures against high temperature, a cooling fan is provided with each of the engine and the generator, and a plurality of external openings through which outside air is sucked into the cover are provided in the cover. Accordingly, the outside air is sucked into the cover through the external openings by the suction power of the cooling fans, whereby the engine, the generator and the like can be cooled. The cooling fan at the side of the generator is covered by a bracket having an exhaust port, and the bracket is covered by a generator exhaust duct. Accordingly, air discharged from the bracket runs inside the generator exhaust duct, whereby the generator can be cooled. 
     However, in the engine generator of the Patent Literature 1, while the outside air is sucked into the cover through the external openings, sound generated in the cover leaks through the external openings, whereby noise tends to become large. Then, in the engine generator of the Patent Literature 1, an intake duct is provided for introducing the air, sucked through the external openings, into the cover. Accordingly, attenuation length is enlarged by the intake duct and the sound generated in the cover is attenuated, whereby the noise can be reduced. 
     Now, the cover is constructed by a cover body which is opened at both sides and a pair of side lids covering both of the side openings. Each of the cover body and the side lids is constructed by a platy member, and the cover body and the side lids are attached to each other by so-called flat plate attachment in which the plate surfaces thereof are overlapped and fixed. 
     One of the side lids is fixed thereto with an intake box which introduces the air, sucked through the external openings, into the cooling fan at the side of the engine. In the vicinity of the intake box, an intake chamber is formed, and an air cleaner performs intake via the intake chamber so as to reduce intake sound which causes noise. The other of the side lids is fixed thereto with a muffler box in which a muffler of the engine is housed. 
     Above the generator, an exhaust duct is provided discharging the air in the cover to the outside. The exhaust duct is attached to a stopper formed over the generator. The stopper is fixed to a damper stay, and the engine and the generator are also fixed to the damper stay. 
     PRIOR ART REFERENCE 
     Patent Literature 
     
         
         
           
             Patent Literature 1: the Japanese Patent Laid Open Gazette 2010-222998 
           
         
       
    
     DISCLOSURE OF INVENTION 
     Problems to be Solved by the Invention 
     However, in the engine generator of the Patent Literature 1, when the intake duct is miniaturized for making the engine generator compact, the length of the air passage formed in the intake duct, that is, the attenuation length is shortened. Then, there is a problem in that the sound generated in the cover is not attenuated enough and the noise is increased. 
     There is a problem in that the cover body is vibrated and the noise is increased, because the cover body is constructed by platy members and does not have enough rigidity. Since the space is limited in the vicinity of the intake box inside the casing, there is a problem in that it is difficult to enlarge the capacity of the intake chamber and to reduce the intake sound which causes the noise so as to reduce the noise of the engine generator. 
     Since the stopper to which the exhaust duct is attached is fixed to the damper stay, the attachment span of the stopper is long. Accordingly, there is a problem in that the exhaust duct, the generator and the engine are not integrated enough and these members do not have enough rigidity so that the exhaust duct is vibrated and the noise is increased. 
     The generator exhaust duct only covers the bracket simply and the shape thereof does not consider the position of the exhaust port of the bracket and the like. Accordingly, there is a problem in that the air in the vicinity of the exhaust port cannot flow smoothly easily so that the whole air in the generator exhaust duct cannot flow smoothly, that is, the exhaust efficiency of the generator exhaust duct is worsened, thereby tending to raise the temperature of the generator, in its turn the whole engine generator. When the temperature of the engine generator is raised, the output of the generator may be reduced. 
     The present invention is provided in consideration of the conditions as mentioned above and the purpose of the invention is to provide an engine generator which can reduce noise and performs cooling efficiently. 
     Means for Solving the Problems 
     The problems to be solved by the present invention have been described above, and subsequently, the means of solving the problems will be described below. 
     An engine generator according to the present invention having an engine, a generator driven by the engine, a cover covering the engine and the generator, and a muffler box in which a muffler of the engine is housed, includes a first external opening formed in the cover for sucking outside air into the cover, and an intake duct for introducing the air sucked via the first external opening into the inside of the cover. An opening is formed in the upper side of the intake duct, and the intake duct is arranged along the side surface of the muffler box and below the upper surface of the muffler box for a predetermined distance. A sound absorbing member is provided between the upper side of the intake duct and the side surface of the muffler box so as to cover a part of the opening. An air passage is formed above the intake duet by the side surface of the muffler box and the sound absorbing member. 
     In the engine generator according to the present invention, the cover has a cover body in which both sides thereof are opened and a pair of side lids covering the openings of both sides of the cover body, a rib is formed in each of the openings of both sides of the cover body, and the muffler box is fixed to one of the ribs. 
     The engine generator according to the present invention further includes an engine cooling fan provided to the engine, a second external opening formed in the cover for sucking outside air into the cover, and an intake box for introducing the air sucked via the second external opening into the engine cooling fan. An air cleaner of the engine is communicated through an intake hose to the intake box. 
     In the engine generator according to the present invention, the intake box is fixed to the other one of the ribs. 
     In the engine generator according to the present invention, the inside of the intake box is partitioned by a partition plate, and the partition plate is arranged between the connection part of the intake box and the intake hose and the second external opening. 
     In the engine generator according to the present invention, an exhaust duct for discharging air in the cover to the outside is provided above the generator, and an attachment base to which the exhaust duct is attached is provided on the upper surface of the generator. 
     In the engine generator according to the present invention, a generator cooling fan is provided to the generator, the generator cooling fan is covered by a bracket having an exhaust port, the bracket is covered by a generator exhaust duct, and the generator exhaust duct is provided therein with an expansion part which expands outward along the rotational radial direction of the generator cooling fan and faces the exhaust port. 
     Effect of the Invention 
     The present invention brings the following effects. 
     According to the engine generator of the present invention, the attenuation length is extended by the air passage so that the sound generated in the cover is attenuated enough, thereby reducing the noise. 
     According to the engine generator of the present invention, the rib improves the rigidity of the cover body, and the cover body and the muffler box are constructed integrally so as to improve the rigidity thereof, thereby reducing the vibration of the cover body so as to reduce the noise. 
     According to the engine generator of the present invention, the intake box serves as an intake chamber, whereby it is not necessary to provide any intake chamber of exclusive use. Accordingly, by employing surplus space around the intake box so as to increase the capacity of the intake box, the intake sound which causes the noise can be reduced. By omitting the intake chamber of exclusive use, the weight of the whole engine generator can be reduced and the number of parts thereof can be reduced, whereby the cost can be reduced. 
     Furthermore, according to the engine generator of the present invention, the cover body and the intake box are constructed integrally so as to improve the rigidity thereof, thereby reducing the vibration of the cover body so as to reduce the noise. 
     According to the engine generator of the present invention, the attenuation length is extended by the partition plate so that the intake sound is attenuated enough, thereby reducing the noise. 
     According to the engine generator of the present invention, the exhaust duct is attached to the attachment base. Accordingly, the exhaust duct, the generator and the engine are constructed integrally so as to improve the rigidity thereof, thereby reducing the vibration of the exhaust duct so as to reduce the noise. 
     Furthermore, according to the engine generator of the present invention, the expansion part makes the flowing of air in the vicinity of the exhaust port smooth, thereby making the whole inside of the exhaust duct of the generator smooth so as to cool efficiently the generator, in its turn the whole engine generator. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of an engine generator. 
         FIG. 2( a )  is a front view of the engine generator.  FIG. 2( b )  is a left side view of the engine generator. 
         FIG. 3( a )  is a rear view of the engine generator.  FIG. 3( b )  is a right side view of the engine generator. 
         FIG. 4  is a front view of an inner structure of the engine generator. 
         FIG. 5( a )  is a left side view of the inner structure of the engine generator.  FIG. 5( b )  is a right side view of the inner structure of the engine generator. 
         FIG. 6( a )  is a perspective view of an intake duct and circumference thereof.  FIG. 6( b )  is a perspective view of the intake duct. 
         FIG. 7( a )  is a sectional side view of the intake duct and a muffler box.  FIG. 7( b )  is an arrow sectional view of the line A-A in  FIG. 7( a ) . 
         FIG. 8( a )  is a perspective view of a left side of a cover body.  FIG. 8( b )  is a perspective view of the muffler box. 
         FIG. 9( a )  is a perspective view showing the state in which the muffler box is detached from the cover body.  FIG. 9( b )  is a perspective view of a rib. 
         FIG. 10( a )  is a perspective view showing the state in which the muffler box is attached to the cover body.  FIG. 10( b )  is a perspective view of the inner structure of the muffler box. 
         FIG. 11  is a perspective view of a generator intake duct and circumference thereof. 
         FIG. 12( a )  is a left side view of the muffler box attached to the cover body.  FIG. 12( b )  is an arrow sectional view of the line B-B in  FIG. 12( a ) . 
         FIG. 13  is a perspective view of an intake box attached to the cover body. 
         FIG. 14  is a right side view of the intake box attached to the cover body. 
         FIG. 15( a )  is a perspective view showing the state in which the engine and the generator are fixed to a damper stay.  FIG. 15( b )  is a perspective view of an attachment base. 
         FIG. 16  is a front view of the engine and the generator fixed to the damper stay and an exhaust duct fixed to the attachment base. 
         FIG. 17  is a perspective view of a generator exhaust duct. 
         FIG. 18( a )  is a side view of the generator exhaust duct.  FIG. 18( b )  is a sectional side view of the generator exhaust duct. 
         FIG. 19( a )  is a perspective front view of a generator front bracket. FIG.  19 ( b ) is a perspective rear view of the generator front bracket. 
     
    
    
     DESCRIPTION OF NOTATIONS 
       1  engine generator 
       2  engine 
       3  generator 
       4  cover 
       7  intake duct 
       13  muffler box 
       15  exhaust duct 
       17  sponge (sound absorbing member) 
       18  air passage 
       23  air cleaner 
       25  engine cooling fan 
       27  intake hose 
       28  intake box 
       32  generator rear bracket (bracket) 
       33  generator cooling fan 
       34  generator exhaust duct 
       41  cover body 
       43  left side lid 
       43  right side lid 
       71  opening 
       241  muffler 
       242  muffler 
       286 D outer partition plate 
       321  attachment base 
       342  first expansion cover (expansion part) 
       343  second expansion cover (expansion part) 
       351  first exhaust port (exhaust port) 
       352  second exhaust port (exhaust port) 
       412  external opening (first external opening) 
       413  external opening (second external opening) 
       414  external opening (first external opening) 
       415  external opening (second external opening) 
       416  rib 
     C connection part 
     DETAILED DESCRIPTION OF THE INVENTION 
     An explanation will be given on an embodiment for carrying out the present invention referring to drawings. 
     Firstly, an explanation will be given on entire construction of an engine generator  1  according to an embodiment of the present invention referring to  FIGS. 1 to 5 . A position and direction of each of members described below is explained while a direction shown by an arrow F in  FIG. 1  is regarded as “forward direction”, an arrow U is regarded as “upward direction”, and an arrow L is regarded as “leftward direction”. 
     The engine generator  1  has an engine  2 , a generator  3  driven by the engine  2 , and a cover  4  covering the engine  2  and the generator  3 . 
     As shown in  FIGS. 1 to 3 , the cover  4  has a cover body  41  which is substantially reverse U-like shaped when viewed in side and is opened at left, right and bottom sides, a pair of side lids  42  and  43  covering left and right side openings of the cover body  41 , and a lower casing  44  covering a lower opening of the cover body  41 . At the left and right sides of the cover body  41 , two attachment surfaces  411  are provided to which the side lids  42  and  43  are attached. 
     In the upper right portion of the front surface of the cover body  41 , an operation panel  5  is provided for controlling the engine generator  1 . In the operation panel  5 , two plug sockets  51  having waterproof covers and the like are provided. At the substantially longitudinal center of the cover body  41 , a door  6  is provided. The door  6  can be rotated laterally with its left side as a rotation fulcrum so as to be opened and closed. In the upper surface of the cover body  41 , a hook  10  is provided for pulling up the engine generator  1 . 
     At the front side of the cover body  41 , external openings  412  and  413  are formed for sucking outside air into the cover  4 . The external opening  412  is arranged at the upper left portion of the front side of the cover body  41 , and the external opening  413  is arranged at the lower right portion of the front side of the cover body  41 . Similarly to the front side of the cover body  41 , at the rear side of the cover body  41 , external openings  414  and  415  are formed for sucking outside air into the cover  4 . The external opening  414  is arranged at the upper left portion of the rear side of the cover body  41 , and the external opening  415  is arranged at the lower right portion of the rear side of the cover body  41 . The external opening  412  at the front side of the cover body  41  and the external opening  414  at the rear side of the cover body  41  are arranged symmetrically longitudinally, and the external opening  413  at the front side of the cover body  41  and the external opening  415  at the rear side of the cover body  41  are arranged symmetrically longitudinally. Inside the external openings  412  and  414  at the front and rear sides of the cover body  41 , two intake ducts  7  are provided respectively. The intake ducts  7  will be explained later. 
     In the upper portion of the left side lid  42 , a left handle  8  is provided which is a handle at the time of moving the generator  1 . In the lower portion of the left side lid  42 , an external opening  421  is formed for discharging air in the cover  4  to the outside. The external opening  421  is arranged at the substantially longitudinal center of the left side lid  42 . At the front and rear sides of the left side lid  42  about the external opening  421 , two pressed ribs  422  which are respectively extended vertically are formed. Accordingly, the rigidity of the left side lid  42  is improved. The pressed ribs  422  are formed so as to be recessed toward the inside of the cover  4 . 
     In the upper portion of the right side lid  43 , a right handle  9  is provided which is a handle at the time of moving the engine generator  1 . In the lower portion of the right side lid  43 , an external opening  431  is formed for sucking outside air into the cover  4 . The external opening  431  is arranged at the substantially longitudinal center of the right side lid  43 . At the front and rear sides of the right side lid  43  about the external opening  431 , two pressed ribs  432  which are respectively extended vertically are formed. Accordingly, the rigidity of the right side lid  43  is improved. The pressed ribs  432  are formed so as to be recessed toward the inside of the cover  4 . 
     At the front side of the lower casing  44 , external openings  441  and  442  are formed for sucking outside air into the cover  4 . The external opening  441  is arranged at the left portion of the front side of the lower casing  44 , and the external opening  442  is arranged at a position near the lateral center of the front side of the lower casing  44 . At the rear side of the lower casing  44 , an external opening  443  is formed through which outside air is sucked into the cover  4 . The external opening  443  is arranged at the left side of the rear portion of the lower casing  44 . The external opening  441  at the front side of the lower casing  44  and the external opening  443  at the rear side of the lower casing  44  are arranged symmetrically longitudinally. Two fixed casters  11  and two free casters  12  are attached to the four corners of the lower surface of the lower casing  44 . The fixed casters  11  are arranged at the left side of the lower surface of the lower casing  44 , and the free casters  12  are arranged at the right side of the lower surface of the lower casing  44 . Accordingly, the engine generator  1  can be moved easily and the moving direction of the engine generator  1  can be changed easily. 
     As shown in  FIGS. 4 and 5  in the engine  2 , a cylinder head  22  is attached above a cylinder block  21 . At the right side of the cylinder block  21 , a fan casing  26  is attached in which an engine cooling fan  25  is stored. The engine cooling fan  25  is rotated by power of a crankshaft (not shown). An intake port and an exhaust port (not shown) are formed in the cylinder head  22 . An air cleaner  23  is attached to the intake port, and an exhaust pipe  24  is attached to the exhaust port. 
     The air cleaner  23  is connected to an intake box  28  via an intake hose  27 . At the front and rear sides of the intake box  28 , openings  281 A and  282 A are respectively formed. Each of the openings  281 A and  282 A at the front and rear sides are substantially rectangular and vertically long when viewed in front. 
     The exhaust pipe  24  is provided laterally, and mufflers  241  and  242  are provided at the middle of the exhaust pipe  24 . The mufflers  241  and  242  are housed in a muffler box  13  and aligned above and below. From the upper muffler  241 , a tail pipe  243  of the exhaust pipe  24  is extended upward, and an exhaust port  243 A of the tail pipe  243  is projected upward from the upper surface of the cover body  41 . The exhaust port  243 A is arranged at the substantially center of the engine generator  1  in the longitudinal direction. Accordingly, the exhaust port  243 A is kept away from the side of the operation panel  5  (the front side) of the engine generator  1 , whereby exhaust gas discharged from the exhaust port  243 A is hardly blown to an operator at the side of the operation panel  5  (the front side) of the engine generator  1 . 
     The generator  3  is arranged at the left of the engine  2 . The generator  3  has a generator body  31  constructed by a rotor (not shown) and the like, and at the left and right sides of the generator body  31 , a generator rear bracket  32  and a generator cooling fan  33  are respectively provided. The generator cooling fan  33  is covered by a generator exhaust duct  34 . The rotor of the generator body  31  and the generator cooling fan  33  are rotated by power of the crankshaft of the engine  2 . At the left side of the rear bracket  32 , a generator intake duct  36  is provided which introduces air to the side of the generator cooling fan  33 . The air introduced by the generator intake duct  36  is sucked through the external openings  441  and  442  at the front side of the lower casing  44 , the external opening  443  at the rear side of the lower casing  44  (see  FIG. 3( a ) ) and the like. 
     Before the generator  3 , a battery  14  is provided. By opening and closing the door  6  (see  FIG. 1 ), the maintenance of the battery  14  and the like can be performed easily. Above the generator  3 , an exhaust duct  15  is provided, and above the exhaust duct  15 , a fuel tank  16  is provided in which fuel for the engine  2  is stored. 
     The exhaust duet  15  is provided laterally, and the left and right sides thereof are opened. The left and right ends of the exhaust duct  15  are fixed respectively to the right side surface of the muffler box  13  and the left side surface of the engine  2  (the cylinder block  21  or the like) by bolts (not shown) or the like. The exhaust duct  15  is attached to an attachment base  321  attached to the upper surface of the generator rear bracket  32 . Details of the attachment base  321  will be discussed later. 
     Next, an explanation will be given on the intake ducts  7  referring to  FIGS. 6 and 7 . Herein, as an example, the intake duct  7  at the rear side of the cover body  41  is explained. Thick black arrows in  FIGS. 6 and 7  show air flows. 
     The intake duct  7  has a bottom and an opening  71  is provided in the upper side thereof. The intake duct  7  is arranged below the upper surface of the muffler box  13  for a predetermined distance along the rear surface of the muffler box  13 . Around the intake duct  7 , in the inner surface of the cover body  41 , a sponge member  17  as a sound insulator is stuck. A part of the sponge member  17  (sponge piece  171  shown in  FIG. 6 ) is provided between the upper portion of the intake duct  7  and the rear surface of the muffler box  13  so as to cover only the left half of the opening  71 , that is, so as not to cover the right half of the opening  71 . Above the intake duct  7 , an air passage  18  is formed by the rear surface of the muffler box  13  and the sponge member  17 . 
     According to the construction, air sucked through the external opening  414  runs in the intake duct  7  and flows into the air passage  18  through the opening  71 . Then, air in the air passage  18  runs upward along the muffler box  13 , and flows out from the air passage  18  through the upper end of the air passage  18  and runs near the fuel tank  16 . Accordingly, the air sucked through the external opening  414  is introduced into the cover  4  by the intake duct  7 . Similarly, air sucked through the external opening  412  is introduced into the cover  4  by the intake duct  7 . Subsequently, the air having run near the fuel tank  16  flows into the exhaust duct  15  through the front end opening of the exhaust duct  15 , and runs from the exhaust duct  15  in the muffler box  13  and is discharged outside the cover  4  through the external opening  421 . 
     On the other hand, sound generated in the cover  4  leaks from the external openings  412  and  414  via the air passages  18  and the intake ducts  7  of the front and rear sides. For enlarging attenuation length of the sound generated in the covet  4 , preferably, the intake ducts  7  are arranged below as much as possible from the upper surface of the muffler box  13 . 
     Next, an explanation will be given on the cover body  41 , the muffler box  13  and the intake box  28  referring to  FIGS. 8 to 14 . Thick black arrows in  FIGS. 10( b )  and  14  show an air flow. 
     As shown in  FIGS. 8( a )  and  9 , at the left side of the cover body  41 , a rib  416  is formed. Similarly to the left side of the cover body  41 , a rib  416  is formed at the right side of the cover body  41 . Herein, as an example, only the rib  416  at the left side of the cover body  41  is explained. The rib  416  is constructed by a front rib  416 A formed at the front side of the cover body  41  and a rear rib  416 B formed at the rear side of the cover body  41 . The front and rear ribs  416 A and  416 B are bent toward the inner side of the cover body  41  substantially perpendicularly to the attachment surface  411  at the side of the free end of the attachment surface  411 . 
     As shown in  FIG. 8( b ) , the muffler box  13  is a box-like member constructed by combining a front plate  131 , a rear plate  132 , a top plate  133 , a bottom plate  134  and a right side plate  135  etc., and the left side of the muffler box  13  is opened. The left opening of the muffler box  13  is covered by the left side lid  42 . In the top plate  133 , an insertion hole  133 A is formed into which the tail pipe  243  (the exhaust port  243 A) of the exhaust pipe  24  is inserted. In the right side plate  135 , an opening  135 A is formed which is connected to the left end of the exhaust duct  15 . As shown in  FIG. 10( b ) , air from the left end opening of the exhaust duct  15  flows through the opening  135 A into the muffler box  13 . As shown in  FIGS. 10 and 11 , the rear surface (the right side surface) of the right side plate  135  of the muffler box  13  seals the left end opening of the generator intake duct  36 , whereby air in the generator intake duct  36  does not leak. Accordingly, a duct structure is constructed by the generator intake duct  36  and the rear surface (the right side surface) of the right side plate  135 . A sponge member (not shown) as a seal member is stuck to the rear surface (the right side surface) of the right side plate  135 . As shown in  FIG. 12 , among the front plate  131  and the rear plate  132 , the front plate  131  is fixed to the front rib  416 A by a plurality of bolts (in this embodiment four bolts)  19 , and the rear plate  132  is fixed to the rear rib  416 B by a plurality of bolts (in this embodiment, four bolts)  19 . 
     As shown in  FIGS. 13 and 14 , the intake box  28  is a box-like member constructed by combining a front plate  281 , a rear plate  282 , a top plate  283 , a bottom plate  284  and a left side plate  285 , and the right side of the intake box  28  is opened. The right opening of the intake box  28  is covered by the right side lid  43 . One of the ends of the intake hose  27  is connected to the front side of the top plate  283 . The other end of the intake hose  27  is connected to the air cleaner  23 . The openings  281 A and  282 A mentioned above are formed respectively in the front plate  281  and the rear plate  282 . The opening  281 A of the front side is arranged to face the external opening  413 , and the opening  282 A of the rear side is arranged to face the external opening  415 . Among the front plate  281  and the rear plate  282 , the front plate  281  is fixed to the front rib  416 A by a plurality of bolts (in this embodiment, two bolts)  19 , and the rear plate  282  is fixed to the rear rib  416 B by a plurality of bolts (in this embodiment, two bolts)  19 . 
     In the left side plate  285 , an opening  285 A facing the engine cooling fan  25  is formed. The opening  285 A is substantially circular when viewed in side, and the upper half thereof is covered by a cover  286 A attached to the right side lid  43 . The cover  286 A is substantially rectangular and laterally long when viewed in side. At the front and rear sides of the cover  286 A, inner partition plates  286 B and  286 C are respectively provided. An outer partition plate  286 D is provided between the inner partition plate  286 B of the front side and the front plate  281 , and an outer partition plate  286 E is provided between the partition plate  286 C of the front side and the rear plate  282 . By the inner partition plates  286 B and  286 C and the outer partition plates  286 D and  286 E, the inside of the intake box  28  is partitioned. The inner partition plates  286 B and  286 C are provided upright on the bottom plate  284 , and the outer partition plates  286 D and  286 E are provided to be pendent from the top plate  283 . Namely, the inner partition plates  286 B and  286 C and the outer partition plates  286 D and  286 E are arranged alternately longitudinally. 
     The outer partition plate  286 D of the front side is arranged between the connection part of the right opening of the intake box  28  and the intake hose  27  (connection part C shown in  FIG. 14 ) and the opening  281 A (the external opening  413 ). The outer partition plate  286 D of the front side is constructed by an inclination part  286 Da facing the opening  281 A aslant and a perpendicular part  286 Db which is pendent from the lower end (end opposite to the connection part C) of the inclination part  286 Da and faces the opening  281 A frontally. The inclination part  286 Da is inclined so that the distance to the opening  281 A (distance L 1  shown in  FIG. 14 ) is longer at the lower side. 
     Sponge members  17  are stuck respectively to the surfaces of the outer partition plate  286 D of the front side and the inner partition plate  286 B facing each other, the surfaces of the outer partition plate  286 E of the rear side and the inner partition plate  286 C facing each other, and the upper and lower end surfaces of the cover  286 A. Sponge members (not shown) as sound insulators are also stuck to the inner surfaces of the top plate  283 , the bottom plate  284  and the left side plate  285 . 
     According to the construction, air sucked from the external opening  413  at the front side of the cover body  41  flows into the intake box  28  through the opening  281 A. Air from the opening  281 A is divided into two, and one of the two passes below the outer partition plate  286 D and then is sucked into the air cleaner  23  via the intake hose  27 , and the other of the two runs above the inner partition plate  286 B and is sucked into the engine cooling fan  25  via the opening  285 A. As mentioned above, the inclination part  286 Da is inclined so that the distance L 1  to the front opening  281 A is longer at the lower side, that is, the downstream side of the air flow, whereby the area of the passage through which air flows between the outer partition plate  286 D and the inner surface of the front plate  281 , and the air from the opening  281 A flows smoothly. On the other hand, intake sound of the air cleaner  23  passes below the outer partition plate  286 D and then leaks via the opening  281 A through the external opening  413 . 
     Air sucked from the external opening  415  at the rear side of the cover body  41  flows into the intake box  28  through the opening  282 A. Then, air from the opening  282 A runs below the outer partition plate  286 E and above the inner partition plate  286 C and is sucked into the engine cooling fan  25  via the opening  285 A. Air sucked from the external opening  431  of the side lid  43  also flows into the intake box  28 , and the air is sucked into the engine cooling fan  25  via the opening  285 A. Accordingly, the air sucked from the external openings  413  and  415  is introduced into the engine cooling fan  25  by the intake box  28 . Subsequently, the air sucked into the engine cooling fan  25  flows into the exhaust duct  15  through the right end opening of the exhaust duct  15 , runs from the exhaust duct  15  to the muffler box  13 , and is discharged outside the cover  4  through the external opening  421 . 
     Next, an explanation will be given on the attachment base  321  referring to  FIGS. 15 and 16 . 
     The attachment base  321  is a metal platy member, and front and rear ends thereof are formed substantially crank-like. At the front and rear ends of the attachment base  321 , bolt holes (not shown) are formed through which two bolts  321 A are inserted, and the attachment base  321  is attached to the generator rear bracket  32  by the bolts  321 A. Between the front and rear ends of the attachment base  321 , two bolt holes  321 C are formed through which two bolts  321 B are inserted, and the exhaust duct  15  is fixed to the attachment base  321  by the bolts  321 B. 
     The engine  2  and the generator  3  are fixed on a damper stay  20 . The exhaust duct  15  is fixed via the attachment base  321  to the generator  3  (the generator rear bracket  32 ) and is also fixed to the engine  2 . Accordingly, the exhaust duct  15 , the engine  2 , the generator  3  and the damper stay  20  are constructed integrally so as to improve the rigidity thereof. 
     In this embodiment, the attachment base  321  is provided independently from the generator rear bracket  32  (bracket). However, the attachment base may alternatively be provided integrally with the bracket. 
     Next, an explanation will be given on the generator exhaust duct  34  referring to  FIGS. 17 to 19 . Thick black arrows in  FIG. 18( b )  show an air flow. 
     As shown in  FIGS. 17 and 18 , the generator exhaust duct  34  covers the circular perimeters of the generator cooling fan  33  and a generator front bracket  35 , and air runs in the generator exhaust duct  34 . In this embodiment, the generator cooling fan  33  rotates counterclockwise when viewed in left side (when the side of the engine  2  is seen from the side of the generator  3  in the lateral direction), and rotation direction of air in the generator exhaust duct  34  is counterclockwise. 
     The generator exhaust duct  34  has a duct body  341  which is opened upward so as to be U-like shaped. At the ends of the duct body  341  at the side of upstream of the rotation and the side of downstream of the rotation, attachment parts  341 A and  341 B are respectively provided which are attached to the lower surface of the exhaust duct  15 . At the end of the duct body  341  at the side of downstream of the rotation, an opening  341 C is provided. The opening  341 C is connect to an opening (not shown) formed in the lower surface of the exhaust duct  15 . 
     At the front and rear sides of the duct body  341 , openings  341 D and  341 E are formed. The opening  341 D of the front side is covered by a first expansion cover  342 , and the opening  341 E of the rear side is covered by a second expansion cover  343 . The first and second expansion covers  342  and  343  expand outward in the rotational radial direction of the generator cooling fan  33 . 
     In the generator exhaust duct  34 , the generator cooling fan  33  is covered by the generator front bracket  35  having first and second exhaust ports  351  and  352 . As shown in  FIG. 19 , the generator front bracket  35  is formed substantially scroll-like when viewed in side, and air runs in the generator front bracket  35  and is discharged through the first and second exhaust ports  351  and  352 . The first exhaust port  351  is arranged above the rotation center of the generator cooling fan  33  (rotation center O shown in  FIG. 18 ) at the front side of the generator front bracket  35 , and the second exhaust port  352  is arranged below the rotation center O at the rear side of the generator front bracket  35 . Air flows into the generator front bracket  35  through an opening (not shown) formed in the front side of the generator front bracket  35 . 
     The first expansion cover  342  is bent at its middle portion (bent part  342 A shown in  FIG. 18 ) and is provided so as to face the first exhaust port  351 . The bent part  342 A at the middle portion of the first expansion cover  342  is the most front position of the first expansion cover  342 , and the distance from the front surface of the duct body  341  to the bent part  342 A is referred to as L 2 . The first expansion cover  342  is constructed by an upstream slanting part  342 B arranged upstream the bent part  342 A and a downstream slanting part  342 C arranged downstream the bent part  342 A. The upstream slanting part  342 B is extended aslant toward the bent part  342 A from the upper portion of the front surface of the duct body  341 , and the downstream slanting part  342 C is extended aslant toward the bent part  342 A from the lower portion of the front surface of the duct body  341 . 
     The second expansion cover  343  is bent at its middle portion (bent part  343 A shown in  FIG. 18 ) and is provided so as to face the second exhaust port  352 . The bent part  343 A at the middle portion of the second expansion cover  343  is the most rear position of the second expansion cover  343 , and the distance from the rear surface of the duct body  341  to the bent part  343 A is referred to as L 3 . In this embodiment, the distance L 3  is longer than the distance L 2 . Namely, the second expansion cover  343  is expanded outward in the rotational radial direction of the generator cooling fan  33  more than the first expansion cover  342 . The second expansion cover  343  is constructed by an upstream slanting part  343 B arranged upstream the bent part  343 A and a downstream slanting part  343 C arranged downstream the bent part  343 A. The upstream slanting part  343 B is extended aslant toward the bent part  343 A from the lower portion of the rear surface of the duct body  341 , and the downstream slanting part  343 C is extended aslant toward the bent part  343 A from the upper portion of the rear surface of the duct body  341 . 
     According to the construction, as shown in  FIG. 18( b ) , air discharged from the first exhaust port  351  of the generator front bracket  35  runs smoothly along the upstream slanting part  342 B of the first expansion cover  342 , and the discharged air is changed its direction at the bent part  342 A and runs smoothly along the downstream slanting part  342 C. Air discharged from the second exhaust port  352  of the generator front bracket  35  runs smoothly along the upstream slanting part  343 B of the second expansion cover  343 , and the discharged air is changed its direction at the bent part  343 A and runs smoothly along the downstream slanting part  343 C. Accordingly, the air discharged from the first and second exhaust ports  351  and  352  joins each other and is discharged from the opening  341 C of the generator exhaust duct  34 . Subsequently, the air discharged from the opening  341 C flows into the exhaust duct  15  via the above-mentioned opening in the lower surface of the exhaust duct  15 , runs from the exhaust duct  15  to the muffler box  13 , and is discharged outside the cover  4  through the external opening  421 . 
     In this embodiment, the two first and second expansion covers  342  and  343  (expansion parts) are provided corresponding to the number of the first and second exhaust ports  351  and  352  of the generator front bracket  35  (bracket). However, one or three or more expansion parts may alternatively be provided corresponding to the number of the exhaust ports of the bracket. In this embodiment, the first and second expansion covers  342  and  343  (expansion parts) are provided independently from the duct body  341 . However, the expansion parts alternatively be provided integrally with the duct body. 
     As mentioned above, the engine generator  1  having the engine  2 , the generator  3  driven by the engine  2 , the cover  4  covering the engine  2  and the generator  3 , and the muffler box  13  in which the mufflers  241  and  242  of the engine  2  is housed, includes the external openings  412  and  414  formed in the cover  4  (the cover body  41 ) for sucking outside air into the cover  4 , and intake ducts  7  for introducing the air sucked via the external openings  412  and  414  into the inside of the cover  4 . The opening  71  is formed in the upper side of the intake duct  7 , and the intake duct  7  is arranged along the side surface of the muffler box  13  and below the upper surface of the muffler box  13  for a predetermined distance. The sponge member  17  is provided between the upper side of the intake duct  7  and the side surface of the muffler box  13  so as to cover a part of the opening  71 . The air passage  18  is formed above the intake duct  7  by the side surface of the muffler box  13  and the sponge member  17 . 
     According to the construction, the attenuation length is extended by the air passage  18  so that the sound generated in the cover  4  is attenuated enough, thereby reducing the noise. 
     The cover  4  has the cover body  41  in which both sides thereof are opened and the pair of the side lids  42  and  43  covering the openings of both sides of the cover body  41 . The ribs  416  are formed in the openings of both sides of the cover body  41 . The muffler box  13  is fixed to the left rib  416  among the ribs  416 . 
     According to the construction, the ribs  416  improves the rigidity of the cover body  41 , and the cover body  41  and the muffler box  13  are constructed integrally so as to improve the rigidity thereof, thereby reducing the vibration of the cover body  41  so as to reduce the noise. 
     The engine cooling fan  25  is provided to the engine  2 . The external openings  413  and  415  are provided which are formed in the cover  4  (the cover body  41 ) for sucking outside air into the cover  4 . The intake box  28  is provided for introducing the air sucked via the external openings  413  and  415  into the engine cooling fan  25 . The air cleaner  23  of the engine  2  is communicated through an intake hose  27  to the intake box  28 . 
     According to the construction, the intake box  28  serves as an intake chamber, whereby it is not necessary to provide any intake chamber of exclusive use. Accordingly, by employing surplus space around the intake box  28  so as to increase the capacity of the intake box  28 , the intake sound which causes the noise can be reduced. By omitting the intake chamber of exclusive use, the weight of the whole engine generator  1  can be reduced and the number of parts thereof can be reduced, whereby the cost can be reduced. 
     The intake box  28  is fixed to the left rib  416  among the ribs  416 . 
     According to the construction, the cover body  41  and the intake box  28  are constructed integrally so as to improve the rigidity thereof, thereby reducing the vibration of the cover body  41  so as to reduce the noise. 
     The inside of the intake box  28  is partitioned by the outer partition plate  286 D, and the partition plate  286 D is arranged between the connection part C of the intake box  28  and the intake hose  27  and the external opening  413 . 
     According to the construction, the attenuation length is extended by the outer partition plate  286 D so that the intake sound is attenuated enough, thereby reducing the noise. 
     The exhaust duct  5  for discharging air in the cover  4  to the outside is provided above the generator  3 . The attachment base  321  to which the exhaust duct  15  is attached is provided on the upper surface of the generator  3  (the generator rear bracket  32 ). 
     According to the construction, the exhaust duct  15  is attached to the attachment base  321  on the generator  3  (the generator rear bracket  32 ). Accordingly, the exhaust duct  15 , the generator  3  and the engine  2  are constructed integrally so as to improve the rigidity thereof, thereby reducing the vibration of the exhaust duct  15  so as to reduce the noise. 
     The generator cooling fan  33  is provided to the generator  3 . The generator cooling fan  33  is covered by the generator front bracket  35  having the first and second exhaust ports  351  and  352 . The generator front bracket  35  is covered by the generator exhaust duct  34 . The generator exhaust duct  34  is provided therein with the first and second expansion covers  342  and  343  which expands outward along the rotational radial direction of the generator cooling fan  33  and faces the first and second exhaust ports  351  and  352 . 
     According to the construction, the first and second expansion covers  342  and  343  make the flowing of air in the vicinity of the first and second exhaust ports  351  and  352  smooth, thereby making the whole inside of the generator exhaust duct  34  smooth so as to cool efficiently the generator  3 , in its turn the whole engine generator  1 . 
     INDUSTRIAL APPLICABILITY 
     The present invention can be employed for an engine generator.