Patent Publication Number: US-11661164-B2

Title: Outboard motor

Description:
TECHNICAL FIELD 
     The present invention relates to an outboard motor installed in a vessel. 
     BACKGROUND ART 
     An engine of an outboard motor heats up due to running, and attains a high temperature. In order to cool this engine, a water jacket provided to the engine is supplied with cooling water (for example, fresh water of a lake/marsh, river or the like, or sea water of a bay, ocean or the like, where the vessel installed with the outboard motor operates). 
     Moreover, the engine is cooled by outside air too. That is, as described in Japanese Laid-Open Patent Publication No. 2013-024173, a casing in which the engine is housed has formed therein an outside air inlet port and an exhaust port. Outside air that has been introduced into the casing via the outside air inlet port flows through an inside of the casing to cool the engine, after which the outside air is discharged to outside of the casing from the exhaust port. As may be understood from this, the outside air flows through the inside of the casing as cooling air. 
     SUMMARY OF INVENTION 
     The vessel is operated on water. Hence, the outside air flowing through the inside of the casing includes much moisture (humidity). There is concern that if a metal-made component is exposed to such outside air, rust will occur. 
     A main object of the present invention is to provide an outboard motor capable of separating moisture from outside air flowing through an inside of a casing. 
     Another object of the present invention is to provide an outboard motor by which formation of rust on a metal-made component can be avoided. 
     According to an embodiment of the present invention, there is provided an outboard motor housing therein an engine, the outboard motor comprising: 
     an engine cover having formed therein a first outside air inlet port positioned on a front side in an advancing direction of a vessel, an exhaust port positioned rearward of the first outside air inlet port in the advancing direction, and a second outside air inlet port positioned on a side surface of the engine cover, the engine cover being configured to cover the engine; 
     a protective member configured to cover at least a rear side, in the advancing direction, of the engine; 
     a front side guide portion supported by the engine cover and configured to guide, downwardly in a gravity direction, outside air that has been introduced into the engine cover from the first outside air inlet port; 
     a rear side guide portion supported by the engine cover and configured to guide, downwardly in the gravity direction, outside air that has been introduced into the engine cover from the second outside air inlet port; and 
     a lower housing arranged below the engine cover and configured to, together with the engine cover, define an engine chamber, 
     a lower end portion of the rear side guide portion being positioned more upward than a bottom portion of the engine is. 
     Although the outside air that has been taken into the engine cover via the first outside air inlet port and the second outside air inlet port is high-humidity air including much humidity, if the above-described configuration has been adopted, the outside air will undergo gas-liquid separation in a process of being guided into the front side guide portion or the rear side guide portion. As a result, low-humidity cooling air can be brought into contact with the engine. It therefore becomes difficult for rust or corrosion to occur in components configuring the engine or other metal-made components. In other words, in the outboard motor employed on fresh water or sea water, concern that rust will occur can be dispelled. 
     Preferably, the lower housing has a storage portion formed therein, and a lower end portion of the front side guide portion is faced onto this storage portion. As a result, it becomes possible for moisture that has been separated from the outside air to be stored in a place separate from the engine. Note that, in order for the outside air from which humidity (moisture) has been separated to flow through toward the engine chamber easily, preferably, a clearance is pre-formed between the lower end portion of the front side guide portion and a side wall of the storage portion. 
     Preferably, a bottom wall of the storage portion has a drain port formed therein. Due to moisture that has been stored in the storage portion being discharged from the drain port, the moisture can easily be discharged to outside of the lower housing. 
     A configuration may be adopted whereby the drain port is provided with a foreign body intrusion preventing unit. As a result, a foreign body is prevented from intruding into an inside of the lower housing from outside via the drain port. 
     In the case of the lower housing being configured by combining a plurality of members, there is a need for increasing seal performance of the places where the members are combined. Accordingly, it is preferable for the lower housing to comprise a single member. As a result, concern that leakage will occur from the lower housing itself, is dispelled. 
     Typically, the exhaust port opens on an upper surface of the engine cover, and the second outside air inlet port opens on a side portion of the engine cover. As a result, the cooling air will easily flow through an inside of the engine chamber. 
     Between the lower housing and the engine cover, there is provided a seal member for sealing between the two. In this case, it is preferable to adopt the seal member including: a base which seats on the lower housing and on which a lower end surface of the engine cover seats; a fitting portion that is continuous with the base and has formed therein a fitting groove to be fitted on to an edge portion of the lower housing; and a tongue piece portion that projects from the fitting portion and interposes between the fitting portion and the engine cover. 
     As may be understood from the above, the space between the lower housing and the engine cover is doubly sealed by the base and the tongue piece portion. Therefore, the space between the two is favorably sealed. Moreover, since an opening of the fitting groove faces downwards, it is difficult for water or the like to intrude into the fitting groove. Hence, the space between the two is even more favorably sealed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a schematic overall side view of an outboard motor according to an embodiment of the present invention; 
         FIG.  2    is a schematic plan view of a lower housing (an under-case) configuring a casing of the outboard motor; 
         FIG.  3    is a schematic perspective view of an engine cover configuring the casing of the outboard motor; 
         FIG.  4    is a principal-parts enlarged longitudinal cross-sectional view of a vicinity of a coupling place of the lower housing and the engine cover on a front side in an advancing direction of a vessel; 
         FIG.  5    is principal-parts side cross-sectional view taken along a front-rear direction of the outboard motor; 
         FIG.  6    is a principal-parts side exploded view taken along the front-rear direction of the outboard motor; 
         FIG.  7    is a principal-parts exploded perspective view of a rear side of the outboard motor; 
         FIG.  8    is principal-parts assembled perspective view of the rear side of the outboard motor; 
         FIG.  9    is a principal-parts side cross-sectional view showing a flow-through process of outside air that has been introduced into the engine cover from a first outside air inlet port; and 
         FIG.  10    is a principal-parts side cross-sectional view showing a flow-through process of outside air that has been introduced into the engine cover from a second outside air inlet port. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A preferred embodiment of an outboard motor according to the present invention will be presented and described in detail below with reference to the accompanying drawings. Note that “front”, “rear”, “left”, and “right” in the following description and drawings indicate frontward, rearward, leftward, and rightward as observed by a steersman gripping a steering wheel of a vessel. 
       FIG.  1    is a schematic overall side view of an outboard motor  10  according to the present embodiment. This outboard motor  10 , which is employed by being fitted to an unillustrated vessel operated on water W, has a casing  18  which is configured including: a shaft cover  12 ; an under-case  14  being a lower housing; and an engine cover  16 . An inner chamber defined by the under-case  14  and the engine cover  16  serves as an engine chamber  20 . Moreover, the shaft cover  12  is provided with a clamp hook  22  for installing the outboard motor  10  in the vessel. 
     A screw  24  is arranged in a rotatable manner in a lower portion of the shaft cover  12 , and a drive shaft  26  for rotating the screw  24  is housed inside the shaft cover  12 . The drive shaft  26  and the screw  24  are coupled via a gear which is not illustrated and a propeller shaft  28 . As a result, the propeller shaft  28  and the screw  24  rotate following the rotation of the drive shaft  26 . 
     On a side surface and a rear surface of the shaft cover  12 , there respectively open a water intake port  30  and a water discharge port  32 . Moreover, the inside of the shaft cover  12  has formed therein: a water supply channel  34  that extends substantially parallelly to the drive shaft  26  from the water intake port  30  toward an engine  40 ; and a water discharge channel  36  that heads for the water discharge port  32  from the engine  40 . The water supply channel  34  is provided with a water pump  38  in a vicinity of the water intake port  30 . 
     The engine chamber  20  houses the engine  40  and a fuel tank  42 . The fuel tank  42  supplies a fuel to the engine  40 . The fuel combusts within the engine  40  whereby the engine  40  is operated and the drive shaft  26  rotates, and the propeller shaft  28  and the screw  24  rotate following the rotation of the drive shaft  26 . 
     Now, a schematic plan view of the under-case  14  interposing between the shaft cover  12  and the engine cover  16 , is shown in  FIG.  2   . The under-case  14  integrally has: a substantially circular ring-shaped bottom wall portion  52  having formed therein a lower portion opening  50 ; and a side wall portion  54  that rises up from the bottom wall portion  52  to circle the bottom wall portion  52 . Whereas an under-cover in conventional technology is configured by coupling a right-side half body and a left-side half body, in the present embodiment, the under-case  14  is configured from a single member. Above the side wall portion  54 , there is formed an upper portion opening  56  which has a larger area than the lower portion opening  50 . 
     A ring-like partitioning wall portion  58  rises up substantially parallelly to the side wall portion  54  from a vicinity of the lower portion opening  50 , in the bottom wall portion  52 . As a result, a circular ring-shaped main storage portion  60  is formed by the side wall portion  54  and the ring-like partitioning wall portion  58 . A demarcating wall portion  62  rises up from the bottom wall portion  52  at a place thereof close to a forward side of the side wall portion  54 , and a sub storage portion  64  of small capacity is formed by the demarcating wall portion  62  and the forward side of the side wall portion  54 . The bottom wall portion  52  has further formed therein a rearward drain port  66  and a frontward drain port  68  for discharging liquid that has been stored in the main storage portion  60  and the sub storage portion  64 , respectively. 
     Grommets  70 ,  72  as foreign body intrusion preventing units are respectively fitted to the rearward drain port  66  and the frontward drain port  68  (refer to  FIG.  4    in particular). The grommets  70 ,  72  allow moisture of the main storage portion  60  or the sub storage portion  64  (both of which are inside the under-case  14 ) to flow out to outside of the under-case  14  via the rearward drain port  66  and the frontward drain port  68 . On the other hand, the grommets  70 ,  72  prevent a foreign body such as sea water from entering the main storage portion  60  or the sub storage portion  64  via the rearward drain port  66  and the frontward drain port  68  from outside of the under-case  14 . 
       FIG.  3    is a schematic perspective view of the engine cover  16  arranged above the under-case  14 . The engine cover  16  has a first outside air inlet port  80  formed on its front surface side, and has an exhaust port  82  formed on its upper surface at substantially a central portion in a front-rear direction thereof. In addition, the engine cover  16  has a left second outside air inlet port  84  and a right second outside air inlet port  86  respectively formed on its left side surface and its right side surface. In this case, the left second outside air inlet port  84  and the right second outside air inlet port  86  extend in such a manner that their front side end portions are each positioned more to a front side than the exhaust port  82  is, and their rear side end portions are each positioned more to a rear side than the exhaust port  82  is. 
     The space between the under-case  14  and the engine cover  16  is sealed by a ring-like seal member  90  shown in  FIG.  4   . This ring-like seal member  90  has a base  92 , a fitting portion  94 , and a tongue piece portion  96 . First, the base  92  seats on a frontward fin  98  provided integrally with the under-case  14 . A lower end surface of the engine cover  16  seats on this base  92 . In other words, the base  92  is sandwiched by the under-case  14  (the frontward fin  98 ) and the engine cover  16 . 
     Moreover, the fitting portion  94  has a region continuous with the base  92 , and a region continuous with this region in a substantially 360° inverted manner, and, due to this inversion, is shaped such that a fitting groove  100  is formed between the two regions. An upper edge portion of the side wall portion  54  of the under-case  14  is fitted into the fitting groove  100 . Due to this fitting and the previously described sandwiching, it becomes difficult for the ring-like seal member  90  to drop out from between the under-case  14  and the engine cover  16 . Note that due to such fitting being performed, an opening of the fitting groove  100  faces downwards. 
     The tongue piece portion  96  is continuous with the fitting portion  94  so as to project to the engine cover  16  side. Hence, the tongue piece portion  96  is crushed by interposing between the engine cover  16  and the region of the fitting portion  94  that is continuous with the base  92 . In other words, the tongue piece portion  96  is sandwiched by the fitting portion  94  and the engine cover  16 . By the base  92  interposing between the under-case  14  (the frontward fin  98 ) and the engine cover  16  and the tongue piece portion  96  interposing between the fitting portion  94  and the engine cover  16 , the space between the under-case  14  and the engine cover  16  is doubly sealed. Hence, seal performance will be favorable. 
       FIGS.  5  and  6    are a principal-parts side cross-sectional view and a principal-parts side exploded view taken along the front-rear direction of the engine chamber  20 . A front duct  120  being a front side guide portion and a rear duct  122  being a rear side guide portion are provided so as to hanging substantially downward on a front side and a rear side of an inside (the engine chamber  20 ) of the engine cover  16 , respectively. The front duct  120  of these two ducts is coupled via a screw (not illustrated) to an inner surface of a ceiling wall of the engine cover  16 . In other words, the front duct  120  is supported by the engine cover  16 . A frontward lead channel  124  is formed by the front duct  120  and a front surface wall of the engine cover  16 . 
     As shown in  FIG.  4   , a frontward portion of a lower end of the front duct  120  abuts on the front surface wall of the engine cover  16 . Moreover, at the lower end of the front duct  120 , there is formed a discharge opening  126  of the frontward lead channel  124 . The sub storage portion  64  is positioned below the discharge opening  126 . The sub storage portion  64  is of broader width compared to the discharge opening  126 , and, as a result, it becomes possible for an airflow (outside air) led out from the discharge opening  126  to flow out from between the front duct  120  and the demarcating wall portion  62 . 
     The other of the two ducts, that is, the rear duct  122  is coupled via a screw  131  to a rear end portion of an air guide  130  interposing between the engine  40  and the engine cover  16 . Since the air guide  130  is coupled to the engine cover  16  via the screw  131 , the rear duct  122  is indirectly supported by the engine cover  16  via the air guide  130 . The rear duct  122  and a rearward wall portion of the engine cover  16  are separated by a certain interval, whereby a rearward lead channel  132  is formed between the rear duct  122  and the rearward wall portion of the engine cover  16 . A hanging-down length of the rear duct  122 , in other words, a trailing end of the rearward lead channel  132  is set to be more upward than a bottom surface of the engine  40 , typically, more upward than a middle portion in a height direction of the engine  40 . 
     As shown in detail in  FIG.  7    which is a principal-parts exploded perspective view and  FIG.  8    which is a principal-parts assembled perspective view, an outlet communicating port  134  which is substantially long hole-shaped opens on a frontward side of the air guide  130 , and a left inlet communicating port  135   a  and a right inlet communicating port  135   b  which are honeycomb-shaped open on sides of the air guide  130 . Furthermore, on a rear side of the air guide  130 , there is formed a lead port  136  for supplying intake air (outside air) to the rearward lead channel  132 . In peripheries of the outlet communicating port  134  and the lead port  136 , there rise up an outlet side lead wall  138  and an inlet side lead wall  140 . Note that in  FIGS.  7  and  8   , illustration of the rear duct  122  provided in the air guide  130  is omitted. 
     The outlet communicating port  134  is arranged at a position displaced forwardly from the exhaust port  82  (refer to  FIG.  3   ). Note that directly under the exhaust port  82 , there is positioned a guiding portion  144  which is provided with lead fins  142  that extend from a front side toward a rear side. 
     A fan cover  150  (refer to  FIGS.  5  and  6   ) is provided between the air guide  130  and the under-case  14 . As may be understood from  FIG.  6   , the fan cover  150  is configured by three members being coupled. The fan cover  150  covers an unillustrated cooling fan, and thereby protects the cooling fan. 
     As shown in  FIGS.  7  and  8   , on a rearward side of the engine  40 , there is arranged an engine guard  152  (a protective member) that covers and thereby protects the engine  40 . The engine guard  152  interposes between the engine  40  and the engine cover  16  and has a rear surface guard portion  154  that covers the whole of a rear surface of the engine  40 , two side surface guard portions  156  that project from the rear surface guard portion  154  while being bent so as to go round to side surfaces of the engine  40 , and an upper surface guide portion  158  that extends from the rear surface guard portion  154  while being bent so as to go round to an upper surface of the engine  40 . Therefore, the rear duct  122  is positioned in a space formed between the rear surface guard portion  154  of the engine guard  152  and the engine cover  16  (refer to  FIG.  5   ). Moreover, a region of the air guide  130  where the lead port  136  has been formed is positioned above the upper surface guard portion  158  (refer to  FIG.  8   ). 
     The outboard motor  10  according to the present embodiment is basically configured as above, and operational advantages thereof will be described next. 
     When the vessel is operated on the water W such as a lake/marsh, river, bay, or ocean, the engine  40  configuring the outboard motor  10  is energized. Due to this energization, the fuel is supplied to the engine  40  from the fuel tank  42 , and the fuel combusts within the engine  40 . Upon the engine  40  being operated in this way, the drive shaft  26  rotates, whereby the propeller shaft  28  coupled to the drive shaft  26  rotates following the rotation of the drive shaft  26 , and, moreover, the screw  24  rotates. As a result of this rotation, a propulsive force on the vessel is realized. 
     Moreover, the water pump  38  is energized simultaneously to operation start of the engine  40 . As a result, the water W (fresh water when a place of operation is a lake/marsh or river, and sea water when the place of operation is a bay or ocean) is drawn up via the water intake port  30 , and flows through the water supply channel  34  as cooling water. The cooling water is supplied to the engine  40 , and after having cooled the engine  40 , passes along the water discharge channel  36  to be discharged from the water discharge port  32 . 
     Furthermore, outside air is introduced into the engine cover  16  from the first outside air inlet port  80 , the left second outside air inlet port  84 , and the right second outside air inlet port  86  respectively formed on the front surface, the left side surface, and the right side surface of the engine cover  16 . The outside air that has been introduced flows through the inside of the engine cover  16  (the engine chamber  20 ) to become the cooling air that cools the engine  40 , and so on. Since the vessel is operated on the water W, the outside air immediately after having been introduced into the engine cover  16  from the first outside air inlet port  80 , the left second outside air inlet port  84 , and the right second outside air inlet port  86  is a gas-liquid two-phase flow that includes humidity. 
     The outside air that has been introduced from the first outside air inlet port  80  (hereafter, also written as “frontward cooling air”) advances slightly to the rear side to contact the front duct  120 . Since the front duct  120  extends toward the under-case  14  side, that is, downwardly, an advancing direction of the frontward cooling air changes to downwards. In other words, the frontward cooling air flows through to the under-case  14  side along an extension direction of the frontward lead channel  124 . 
     Therefore, the frontward cooling air stays for a comparatively long time within the frontward lead channel  124 . While staying within the frontward lead channel  124  in this way, the frontward cooling air contacts the front duct  120  or the frontward wall portion of the engine cover  16  to undergo gas-liquid separation. That is, it separates into moisture and airflow. The separated moisture falls into the sub storage portion  64  from the discharge opening  126  of the frontward lead channel  124  (refer to  FIG.  4    in particular) under action of gravity. 
     The bottom wall portion  52  forming the sub storage portion  64  has the frontward drain port  68  formed therein as described above. The moisture that has fallen into the sub storage portion  64  is discharged to outside of the engine cover  16  via the grommet  72  provided in the frontward drain port  68 . Note that since the grommet  72  is protecting the frontward drain port  68 , a foreign body such as the water W or dust is prevented from intruding into the sub storage portion  64  from outside of the engine cover  16  via the frontward drain port  68 . 
     Since the sub storage portion  64  is of broader width compared to the discharge opening  126 , a clearance is formed between the discharge opening  126  and an upward opening of the sub storage portion  64 . The frontward cooling air (the airflow) from which the moisture has been removed passes through this clearance and is sucked in by negative pressure air intake action of the cooling fan to thereby rise mainly along frontward side surfaces of the engine  40 . The above flow-through process is shown in  FIG.  9   . 
     On the other hand, the outside air that has been introduced from the left second outside air inlet port  84  and the outside air that has been introduced from the right second outside air inlet port  86  pass through the left inlet communicating port  135   a  and the right inlet communicating port  135   b  of the air guide  130 , and merge in a space between these left inlet communicating port  135   a  and right inlet communicating port  135   b , as shown in  FIG.  10   . Hereafter, the merged outside air will also be written as “rearward cooling air”. The rearward cooling air further passes through the lead port  136 , and then, while being guided by the downwardly extending rear duct  122 , advances descending toward the under-case  14 . That is, the rearward cooling air flows through to the under-case  14  side along an extension direction of the rearward lead channel  132 . 
     While staying within the rearward lead channel  132 , the rearward cooling air contacts a rearward wall portion of the engine cover  16  or the upper surface guard portion  158  or the rear surface guard portion  154  of the engine guard  152  to undergo gas-liquid separation, and separate into moisture and airflow. The separated moisture descends under action of gravity, and falls into the main storage portion  60  (refer to  FIG.  2   ) positioned below the rearward lead channel  132 . 
     The moisture that has fallen into the main storage portion  60  is discharged to outside of the engine cover  16  via the rearward drain port  66  formed in the bottom wall portion  52  forming the main storage portion  60 , and the grommet  70 . Since the grommet  70  is protecting the rearward drain port  66 , a foreign body such as the water W or dust is prevented from intruding into the main storage portion  60  from outside of the engine cover  16  via the rearward drain port  66 , similarly to as described above. 
     The lower end of the rear duct  122 , in other words, the trailing end of the rearward lead channel  132  is set to be more upward than the middle portion in the height direction of the engine  40 . Therefore, the rearward cooling air that has been led out from the rearward lead channel  132  is sucked in by negative pressure air intake action of the cooling fan to rise while going round to the side surface guard portions  156  from the rear surface guard portion  154  of the engine guard  152 . Further, the rearward cooling air further enters the clearance between the upper surface guard portion  158  and the upper surface of the engine  40 . Due to the above flow-through process, the rearward cooling air mainly cools rearward side surfaces and a rearward upper surface of the engine  40 . That flow-through process is shown in  FIGS.  9  and  10   . 
     The frontward cooling air and the rearward cooling air that have finished cooling of the engine  40  are led out to between the air guide  130  and the ceiling wall of the engine cover  16  from the outlet communicating port  134 . The frontward cooling air and the rearward cooling air further flow through to the guiding portion  144  by means of the lead fins  142 , and are then discharged to outside of the engine cover  16  from the exhaust port  82 . By the above flow-through process being continued during operation of the vessel, the inside of the engine chamber  20 , in particular, the engine  40 , is efficiently cooled. 
     Moreover, the frontward cooling air and the rearward cooling air contacting the engine  40  have their moisture removed as described above, and so attain low humidity. That is, due to the front duct  120  and the rear duct  122  being provided, the outside air flowing through the inside of the engine chamber  20  (the frontward cooling air and the rearward cooling air) can undergo dehumidification. As a result, concern that rust or corrosion will occur in components configuring the engine  40  or other metal-made components, is dispelled. 
     Additionally, in the present embodiment, the under-case  14  comprises a single member. Therefore, airtightness or liquid-tightness of the under-case  14  itself will be favorable. That is, occurrence of leakage from the under-case  14  is avoided. 
     Moreover, in the present embodiment, a seal member having the base  92 , the fitting portion  94 , and the tongue piece portion  96  is provided between the under-case  14  and the engine cover  16  (refer to  FIG.  4   ). In this case, double sealing is performed by the base  92  and the tongue piece portion  96 , so the space between the under-case  14  and the engine cover  16  is favorably sealed. That is, it is difficult for leakage to occur from between the two member  14  and  16 . 
     Furthermore, since the upper edge portion of the side wall portion  54  of the under-case  14  is fitted into the fitting groove  100 , the opening of the fitting groove  100  faces the under-case  14  side, that is, downwards. Therefore, it becomes difficult for a foreign body such as the water W to enter the fitting groove  100 . This too contributes to improvement in seal performance between the two members  14  and  16 . 
     The present invention is not specifically limited to the above-described embodiment, and a variety of modifications are possible in a range not departing from the spirit of the present invention. 
     For example, a configuration may be adopted in which a check valve is employed as the foreign body intrusion preventing unit. 
     Moreover, a configuration may be adopted in which an under-cover configured by combining a plurality of members is employed.