Abstract:
A saddle-type vehicle is provided with: a seat on which a driver sits; a fuel tank positioned in front of the seat; an engine positioned below the fuel tank and having a crankcase and a cylinder projecting upward from a front of the crankcase; and a fuel vapor passage that is connected to the fuel tank and emits evaporated fuel in the fuel tank to an outside of the fuel tank. At least a part of the fuel vapor passage passes behind the cylinder. The fuel vapor passage is connected to the crankcase at a portion in a rear side of the cylinder and opens toward oil in the engine.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a saddle-type vehicle. 
       BACKGROUND ART 
       [0002]    In a related art, a saddle-type vehicle equipped with a canister has been known in which evaporated fuel in a fuel tank is temporarily absorbed to the canister from which fuel is supplied to an engine intake system (for example, Patent Document 1). 
         [0003]    Further, a fuel vapor processing apparatus for an internal combustion engine has been known in which evaporated fuel in a fuel tank is temporarily absorbed to oil in an engine from which fuel is supplied to an engine intake system (for example, Patent Document 2). 
       PRIOR ART DOCUMENTS 
     Patent Document 
       [0000]    
       
         Patent Document 1: WO 2009/154120 
         Patent Document 2: JP-U-49-088172 
       
     
       SUMMARY OF INVENTION 
     Problem to be Solved by the Invention 
       [0006]    However, the saddle-type vehicle disclosed in Patent Document 1 has a problem that there is a limitation in a design of a vehicle body in order to ensure a placement location and the vehicle body becomes larger when the canister is provided in the saddle-type vehicle. Further, in the fuel vapor processing apparatus for the internal combustion engine disclosed in Patent Document 2, there are various adaptation problems in layout or usability as a saddle-type vehicle in order to mount the processing apparatus on the saddle-type vehicle. 
         [0007]    The invention has been made to solve the above-described problems and an object of the invention is to provide a saddle-type vehicle which is capable of handling evaporated fuel in a fuel tank without using a canister. 
       Means for Solving the Problem 
       [0008]    In order to achieve the above objects, according to a first aspect, a saddle-type vehicle is provided with a seat on which a driver is seated, a fuel tank disposed in front of the seat, an engine disposed below the fuel tank and including a crankcase and a cylinder protruding upward from a front portion of the crankcase, and a fuel vapor passage connected to the fuel tank and configured to discharge evaporated fuel in the fuel tank to the outside of the fuel tank. At least a part of the fuel vapor passage passes behind the cylinder. The fuel vapor passage is connected to a part of the crankcase placed at a rear of the cylinder and opens toward oil in the engine. 
         [0009]    According to a second aspect, in addition to the configuration of the first aspect, the saddle-type vehicle is provided with an intake device extending rearward from the cylinder and having an inlet pipe, a throttle body, a connecting tube and an air cleaner box, and an air introduction passage connecting part provided in the middle of the fuel vapor passage and connected to an air introduction passage for introducing air into the fuel vapor passage. The air introduction passage connecting part is placed below the fuel tank and also in front of the air cleaner box. 
         [0010]    According to a third aspect, in addition to the configuration of the second aspect, the saddle-type vehicle is provided with a first check valve provided in the middle of the fuel vapor passage and configured to stop the flow from the engine side toward the fuel tank side. The air introduction passage connecting part and the first check valve are arranged in a vertically separated manner while interposing the intake device therebetween, as seen from a side of a vehicle. 
         [0011]    According to a fourth aspect, in addition to the configuration of one of the first to third aspects, the intake device is arranged offset to one side in a vehicle width direction and the fuel vapor passage is arranged to pass through the inside of the intake device in the vehicle width direction. 
         [0012]    According to a fifth aspect, in addition to the configuration of one of the first to third aspects, the intake device is curved to one side in a vehicle width direction and the fuel vapor passage is arranged to pass through the curved inside of the intake device. 
         [0013]    According to a sixth aspect, in addition to the configuration of one of the second to fifth aspects, a part of the fuel vapor passage is supported by the intake device. 
         [0014]    According to a seventh aspect, in addition to the configuration of one of the second to sixth aspects, an upper surface of the air cleaner box is covered with the seat, the air introduction passage extends rearward along the upper surface of the air cleaner box and an open end of the air introduction passage is located in the vicinity of an intake port of the air cleaner box. 
         [0015]    According to an eighth aspect, in addition to the configuration of one the second to seventh aspects, the saddle-type vehicle is provided with a seat frame configured to support the seat and arranged to extend rearward and upward and a second check valve provided in the middle of the air introduction passage and configured to stop the flow from the engine side toward the atmospheric side. At least a part of the air introduction passage located downstream of the second check valve is arranged forward and downward along the seat frame. 
       Advantage of the Invention 
       [0016]    According to the first aspect, since at least a part of the fuel vapor passage passes through the rear of the cylinder, is connected to a portion of the crankcase located on the rear of the cylinder and opens to the oil in the engine, it is possible to handle the fuel in the fuel tank without using a canister. Further, since the fuel vapor passage can be arranged utilizing a relatively empty portion, an external appearance can be improved. Furthermore, since the fuel vapor passage is arranged on the rear of the cylinder, air warmed by the cylinder flows to the rear and therefore the fuel can be easily vaporized, even when the evaporated fuel is liquefied due to condensation or the like in the fuel vapor passage. In this way, it is possible to easily feed the fuel to the crankcase. 
         [0017]    According to the second aspect, since the air introduction passage connecting part is arranged below the fuel tank and in front of the air cleaner box, it is possible to effectively utilize a dead space. 
         [0018]    According to the third aspect, since the air introduction passage connecting part and the first check valve are vertically distributed with the intake device interposed therebetween, as seen from the side of a vehicle, it is possible to effectively utilize a dead space at top and bottom of the intake device. 
         [0019]    According to the fourth aspect, since the intake device is arranged offset to one side in a vehicle width direction and the fuel vapor passage is arranged to pass through the inside of the intake device in the vehicle width direction, the fuel vapor passage can be placed inside a vehicle body and therefore an external appearance can be improved. In addition, it is possible to effectively utilize the dead space. 
         [0020]    According to the fifth aspect, since the intake device is curved to one side in the vehicle width direction and the fuel vapor passage is arranged to pass through the curved inside of the intake device, it is possible to effectively utilize the dead space. 
         [0021]    According to the sixth aspect, since a part of the fuel vapor passage is supported by the intake device, it is not necessary to provide a separate member for supporting the fuel vapor passage and therefore it is possible to reduce the manufacturing cost. 
         [0022]    According to the seventh aspect, since an upper surface of the air cleaner box is covered with the seat, the air introduction passage extends rearward along the upper surface of the air cleaner box and an open end of the air introduction passage is located in the vicinity of an intake port of the air cleaner box, air in the vicinity of the intake port of the air cleaner box in which relatively clean air is collected can be introduced into the air introduction passage. 
         [0023]    According to the eighth aspect, since at least a part of the air introduction passage located downstream of the second check valve is arranged forward and downward along the seat frame, the air introduction passage is inclined downward toward the air introduction passage connecting part. By doing so, the fuel can easily flow into the fuel vapor passage even when the fuel enters the air introduction passage, for example. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0024]      FIG. 1  is a left side view showing a saddle-type vehicle according to an exemplary embodiment of the invention. 
           [0025]      FIG. 2  is a plan view showing the saddle-type vehicle shown in  FIG. 1 . 
           [0026]      FIG. 3  is an enlarged left side view showing the surroundings of a fuel tank, an engine and an intake device shown in  FIG. 1 . 
           [0027]      FIG. 4  is an enlarged plan view showing the surroundings of a connecting tube shown in  FIG. 1 . 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0028]    Hereinafter, a saddle-type vehicle according to an exemplary embodiment of the invention will be described in detail with reference to the drawings. Here, the drawings are viewed in directions of reference numerals, and in the following description, front and rear, left and right, up and down are defined in accordance with the direction as seen from a rider. In the drawings, a front side of a vehicle is designated by reference numeral Fr, a rear side thereof is designated by reference numeral Rr, a left side thereof is designated by reference numeral L, a right side thereof is designated by reference numeral R, an upper side thereof is designated by reference numeral U and a lower side thereof is designated by reference numeral D. 
         [0029]    As shown in  FIG. 1  and  FIG. 2 , a motorcycle (a saddle-type vehicle)  10  of the embodiment includes a vehicle body frame  11  which is configured by a head pipe  12  provided at a front end thereof, a main frame  13  extending rearward and downward from the head pipe  12 , a pair of left and right pivot frames  14  connected to a rear end of the main frame  13  and extending downward therefrom, a pair of left and right seat frames  15  connected to a rear portion of the main frame  13  and extending rearward and upward therefrom, a pair of left and right sub frames  16  connected to an intermediate portion of the pair of left and right pivot frames  14  and extending rearward and upward therefrom and a down frame  17  extending rearward and downward from the head pipe  12 . Rear ends of the sub frame are connected to the pair of left and right seat frames  15 . An engine  50  is mounted to the pivot frames  14  and the down frame  17 . 
         [0030]    The motorcycle  10  includes a front fork  21  steerably supported on the head pipe  12 , a front wheel WF rotatably supported on a lower end of the front fork  21 , a steering handle  22  attached to an upper end of the front fork  21 , a swing arm  23  pivotably supported on the pivot frames  14 , a rear wheel WR rotatably supported on a rear end of the swing arm  23 , a headlight  25  provided in front of the head pipe  12 , a seat  26  which is supported on an upper surface of the seat frames  15  and on which a driver is seated, and a fuel tank  27  disposed in front of the seat  26 . 
         [0031]    As shown in  FIG. 1  and  FIG. 2 , the engine  50  is disposed below the fuel tank  27 . Outer shell of the engine is mainly configured by a crankcase  51 , a cylinder  52  protruding upward from a front portion of the crankcase  51 , an ACG (generator) cover  56  covering an opening on the left side of the crankcase  51  and a clutch cover  57  covering an opening on the right side of the crankcase  51 . The cylinder  52  is configured by a cylinder block  53 , a cylinder head  54  and a cylinder head cover  55 . 
         [0032]    As shown in  FIG. 1 , an intake port (not shown) is formed on a rear portion of the cylinder head  54  and an intake device  60  is connected to the intake port so as to face rearward. The intake device includes an inlet pipe  61 , a throttle body  62 , a connecting tube  63  and an air cleaner box  64 . In addition, the intake device  60  is arranged offset to a left side in a vehicle width direction and curved to an outer side in the vehicle width direction, as seen from a plan view of a vehicle. Further, an exhaust port (not shown) is formed on a front portion of the cylinder head  54  and a muffler  66  is connected to the exhaust port via an exhaust pipe  65 . 
         [0033]    As shown in  FIG. 1  to  FIG. 3 , the motorcycle  10  includes a fuel vapor passage  70  connected to the fuel tank  27  and a blow-by gas reducing device  80 . The fuel vapor passage  70  discharges evaporated fuel in the fuel tank  27  to the outside of the fuel tank  27  and supplies the evaporated fuel into the crankcase  51  of the engine  50 . The blow-by gas reducing device  80  supplies blow-by gas in the engine  50  into a clean room of the air cleaner box  64  of the intake device  60 . 
         [0034]    The fuel vapor passage  70  includes a first pipe  71  made of metal, a second tube  72  made of rubber and connected to a downstream end of the first pipe  71 , a T-shaped three pronged joint (air introduction passage connecting part)  75  connected to a downstream end of the second tube  72 , a third tube  73  made of rubber and connected to an end of the straight side of the three pronged joint  75 , a pipe connecting part  51   a  protruding from an upper surface of a rear portion of the crankcase  51  and connected to a downstream end of the third tube  73  and a fourth pipe  74  made of metal and connected to the pipe connecting part  51   a . An upstream end of the first pipe  71  is connected to a gas-liquid separator  28  provided in the fuel tank  27 . 
         [0035]    The first pipe  71  extends obliquely rearward and downward from the gas-liquid separator  28  disposed on a vehicle left side in the fuel tank  27  and toward a vehicle right side. The first pipe is arranged to intersect with the main frame  13 , as seen from a plan view. A downstream end of the first pipe extends to a vehicle right side of a rear end of the main frame  13  and protrudes from a lower surface of the fuel tank  27  to the outside of the fuel tank  27 . Further, the first pipe  71  is a metallic pipe. 
         [0036]    The second tube  72  extends obliquely downward from a downstream end of the first pipe  71  and toward a vehicle left side. The second tube is arranged to intersect with the main frame  13 . A downstream end of the second tube extends to the inside of the intake device  60  in a vehicle width direction, which is disposed at a vehicle left side. Further, the second tube  72  is a rubber tube. 
         [0037]    The third tube  73  extends downward from an end of the straight side of the three pronged joint  75  and is arranged to pass through the inside of the intake device  60  in a vehicle width direction, which is disposed at a vehicle left side. A downstream end of the third tube is connected to the pipe connecting part  51   a  of the crankcase  51  which is located on the rear of the cylinder  52 . Further, the third tube  73  is arranged to pass through the rear of the cylinder  52  of the engine  50 . In addition, a first check valve  41  is provided in the middle of the third tube  73  and stops the flow from the engine  50  side to the fuel tank  27  side. Further, the third tube  73  is a rubber tube. 
         [0038]    As shown in  FIG. 4 , an upper portion of the third tube  73  is supported by a pipe support part  67  which is provided on the inside of the curved connecting tube  63  of the intake device  60 . The pipe support part  67  includes a plate-shaped portion  67   a  which is formed integrally on the inside of the curved connecting tube  63 , a through hole  67   b  which is formed to penetrate vertically the plate-shaped portion  67   a  and through which the third tube  73  is inserted and a slit  67   c  which is formed in the plate-shaped portion  67   a  and allows the third tube  73  to be inserted into the through hole  67   b . By doing so, the third tube  73  is arranged to pass through the inside of the curved connecting tube  63  of the intake device  60 . 
         [0039]    The fourth pipe  74  extends downward from the pipe connecting part  51   a  of the crankcase  51  and is arranged along an inner surface of the crankcase  51 . A downstream end of the fourth pipe extends to a bottom portion of the crankcase  51 . By doing so, the downstream end of the fourth pipe  74  opens toward oil in the crankcase  51 . Further, the fourth pipe  74  is a metallic pipe. 
         [0040]    The three pronged joint  75  is connected to a downstream end of the second tube  72  and arranged below the fuel tank  27  and in front of the air cleaner box  64 . Further, an air introduction tube (air introduction passage)  76  is connected to an end of the branched side of three pronged joint  75  and adapted to introduce air into the fuel vapor passage  70 . 
         [0041]    The air introduction tube  76  extends rearward along an upper surface of the air cleaner box  64  from the end of the branched side of the three pronged joint  75  and an open end (upstream end) thereof is located near an intake port of an intake pipe  64   a  of the air cleaner box  64 . Further, an upper surface of the air cleaner box  64  is covered with the seat  26 . Further, a second check valve  42  is provided in the middle of the air introduction tube  76  and stops the flow from the engine  50  side (or the fuel tank  27  side) to the atmospheric side. In addition, the air introduction tube  76  is a rubber tube. 
         [0042]    The air introduction tube  76  is arranged forward and downward along the seat frame  15 . Further, in order to arrange the air introduction tube  76  forward and downward, an upper surface of the air cleaner box  64  is formed rearward and upward, similar to the seat frame  15 . 
         [0043]    According to the embodiment, the three pronged joint  75  and the first check valve  41  are vertically distributed with the connecting tube  63  of the intake device  60  interposed therebetween, as seen from the side of a vehicle. 
         [0044]    The blow-by gas reducing device  80  is provided on an upper surface of the cylinder head cover  55 . The blow-by gas reducing device includes a gas extraction part  81  to take out blow-by gas in the engine  50 , a gas supply pipe  82  which has an upstream end connected to the gas extraction part  81  and a downstream end connected to a clean room of the air cleaner box  64  and a purge control valve  83  provided in the middle of the gas supply pipe  82 . Here, the purge control valve  83  is a solenoid valve which is opened/closed by a solenoid. 
         [0045]    In the motorcycle  10  configured as described above, air is introduced through the air introduction tube  72  when the interior of the fuel tank  27  becomes negative pressure relative to atmosphere pressure. The introduced air is supplied to the fuel tank  27  via the air introduction tube  72 , the second check valve  42 , the three pronged joint  75 , the second tube  72  and the first pipe  71 , so that the pressure in the fuel tank  27  becomes equal to the atmospheric pressure. 
         [0046]    Meanwhile, when the interior of the fuel tank  27  becomes positive pressure (for example, when the fuel in the fuel tank  27  is evaporated), air or the evaporated fuel is released into oil in the crankcase  51  through the fuel vapor passage  70  from the interior of the fuel tank  27 . At this time, the evaporated fuel is temporarily dissolved in the oil. At this time, since the second check valve  42  is provided in the air introduction tube  76 , there is no case that the evaporated fuel is released into the atmosphere. 
         [0047]    The fuel dissolved in the oil of the crankcase  51  is evaporated again in the engine  50  during engine drive and thus becomes evaporated fuel. The evaporated fuel is supplied along with the evaporated oil to the air cleaner box  64  through the blow-by gas reducing device  80  and then combusted in a combustion chamber of the engine  50  through the intake device  60 . 
         [0048]    As described above, according to the motorcycle  10  of the embodiment, since the third tube  73  which is a portion of the fuel vapor passage  70  passes through the rear of the cylinder  52 , is connected to a portion of the crankcase  51  located on the rear of the cylinder  52  and opens to the oil in the engine  50 , it is possible to handle the fuel in the fuel tank  27  without using a canister. Further, since the fuel vapor passage  70  can be arranged utilizing a relatively empty portion, an external appearance can be improved. Furthermore, since the third tube  73  is arranged on the rear of the cylinder  52 , air warmed by the cylinder  52  flows to the rear and therefore the fuel can be easily vaporized, even when the evaporated fuel is liquefied due to condensation or the like in the fuel vapor passage  70 . In this way, it is possible to easily feed the fuel to the crankcase  51 . 
         [0049]    Further, according to the motorcycle  10  of the embodiment, since the three pronged joint  75  is arranged below the fuel tank  27  and in front of the air cleaner box  64 , it is possible to effectively utilize a dead space. 
         [0050]    In addition, according to the motorcycle  10  of the embodiment, since the three pronged joint  75  and the first check valve  41  are vertically distributed with the intake device  60  interposed therebetween, as seen from the side of a vehicle, it is possible to effectively utilize a dead space at top and bottom of the intake device  60 . 
         [0051]    Further, according to the motorcycle  10  of the embodiment, since the intake device  60  is arranged offset to a left side in a vehicle width direction and the fuel vapor passage  70  is arranged to pass through the inside of the intake device  60  in the vehicle width direction, the fuel vapor passage  70  can be placed inside a vehicle body and therefore an external appearance can be improved. In addition, it is possible to effectively utilize the dead space. 
         [0052]    Further, according to the motorcycle  10  of the embodiment, since the intake device  60  is curved to a left side in the vehicle width direction and the fuel vapor passage  70  is arranged to pass through the inside of the curved connecting tube  63  of the intake device  60 , it is possible to effectively utilize the dead space. 
         [0053]    Further, according to the motorcycle  10  of the embodiment, since the third tube  73  of the fuel vapor passage  70  is supported by the intake device  60 , it is not necessary to provide a separate member for supporting the fuel vapor passage  70  and therefore it is possible to reduce the manufacturing cost. 
         [0054]    Further, according to the motorcycle  10  of the embodiment, since an upper surface of the air cleaner box  64  is covered with the seat  26 , the air introduction tube  76  extends rearward along the upper surface of the air cleaner box  64  and an open end of the air introduction tube is located in the vicinity of an intake port of the air cleaner box  64 , air in the vicinity of the intake port of the air cleaner box  64  in which relatively clean air is collected can be introduced into the air introduction tube  76 . 
         [0055]    Further, according to the motorcycle  10  of the embodiment, since the air introduction tube  76  is arranged forward and downward along the seat frame  15 , the air introduction tube  76  is inclined downward toward the three pronged joint  75 . By doing so, the fuel can easily flow into the fuel vapor passage  70  even when the fuel enters the air introduction tube  76 , for example. 
         [0056]    Hereinabove, although the invention has been described in detail with reference to particular embodiments, it is apparent to those skilled in the art that the exemplary embodiments can be variously modified without departing a spirit and a scope of the invention. 
         [0057]    This application is based on Japanese Patent Application (Patent Application No. 2010-262499) filed on Nov. 25, 2010 and the contents of which are incorporated herein by reference. 
       DESCRIPTION OF REFERENCE NUMERALS 
       [0000]    
       
         
           
               10 : MOTOR CYCLE (SADDLE-TYPE VEHICLE) 
               15 : SEAT FRAME 
               26 : SEAT 
               27 : FUEL TANK 
               41 : FIRST CHECK VALVE 
               42 : SECOND CHECK VALVE 
               50 : ENGINE 
               51 : CRANKCASE 
               52 : CYLINDER 
               53 : CYLINDER BLOCK 
               54 : CYLINDER HEAD 
               55 : CYLINDER HEAD COVER 
               60 : INTAKE DEVICE 
               61 : INLET PIPE 
               62 : THROTTLE BODY 
               63 : CONNECTING TUBE 
               64 : AIR CLEANER BOX 
               70 : FUEL VAPOR PASSAGE 
               71 : FIRST PIPE 
               72 : SECOND TUBE 
               73 : THIRD TUBE 
               74 : FOURTH PIPE 
               75 : THREE PRONGED JOINT (AIR INTRODUCTION PASSAGE CONNECTING PART) 
               76 : AIR INTRODUCTION TUBE (AIR INTRODUCTION PASSAGE) 
               80 : BLOW-BY GAS REDUCING DEVICE 
               81 : GAS EXTRACTION PART 
               82 : GAS SUPPLY PIPE 
               83 : PURGE CONTROL VALVE