Patent Publication Number: US-2023160335-A1

Title: Utility vehicle

Description:
BACKGROUND OF THE INVENTION 
     Technical Field 
     The present disclosure relates to a utility vehicle. 
     Related Art 
     US 2009/0229582 A1 discloses a straddle type vehicle in which an engine is mounted below a seat. In this vehicle, a supercharger is attached to the rear of the engine. 
     SUMMARY 
     In a utility vehicle in which an engine is mounted rearward of a seat, when a supercharger is attached to the rear portion of the engine, the center of gravity of the utility vehicle tends to be located further rearward in the front-rear direction of the vehicle due to the supercharger which is a heavy object. 
     An object of the present disclosure is to provide a utility vehicle that has an engine mounted rearward of a se at and can suppress the center of gravity of the utility vehicle being located closer to the rear side of the vehicle when a supercharger is attached to the engine. 
     An aspect of the present disclosure provides
         a utility vehicle including   a seat,   an engine disposed rearward of the seat, and   a supercharger disposed between the seat and the engine.       

     According to the present disclosure, since the supercharger is disposed between the seat and the engine, the center of gravity of the utility vehicle is located closer to the center in the front-rear direction than when the supercharger is disposed rearward of the engine. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and the other features of the present invention will become apparent from the following description and drawings of an illustrative embodiment of the invention in which: 
         FIG.  1    is a left side view of a vehicle according to a first embodiment of the present disclosure; 
         FIG.  2    is a plan view illustrating an engine and the periphery thereof in  FIG.  1   ; 
         FIG.  3    is a right side view illustrating the engine and the periphery thereof; 
         FIG.  4    is an exploded perspective view illustrating a supercharger detached from the engine; 
         FIG.  5    is a perspective view schematically illustrating a driving force transmission mechanism; 
         FIG.  6    is a plan view illustrating an engine and the periphery thereof according to a second embodiment; 
         FIG.  7    is a plan view illustrating an engine and the periphery thereof according to a third embodiment; 
         FIG.  8    is a plan view illustrating an engine and the periphery thereof according to a fourth embodiment; and 
         FIG.  9    is a perspective view schematically illustrating a driving force transmission mechanism according to an exemplary modification. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     A vehicle  100  according to a first embodiment of the present disclosure will be described with reference to  FIGS.  1  to  5   . The vehicle  100  according to the present embodiment is a utility vehicle. In the following description, the front-rear direction, the left-right direction, and the up-down direction as viewed from a driver are respectively referred tows the front-rear direction, the left-right direction, and the up-down direction of the vehicle  100  and the components thereof. 
     First Embodiment 
       FIG.  1    is a left side view of the vehicle  100 . As illustrated in  FIG.  1   , the vehicle  100  includes a vehicle body  1 , and a power train mechanism  7  mounted on the vehicle body  1 . In  FIG.  1   , the vehicle body  1  is indicated by two-dot chain lines, and the power train mechanism  7  is indicated by solid lines. 
     The vehicle body  1  includes a vehicle body frame  2  constituting a framework. In the vehicle body  1 , a pair of left and right front wheels  3  is disposed on both sides of the front portion of the vehicle body frame  2 , and a pair of left and right rear wheels  4  is disposed on both sides of the rear portion of the vehicle body frame  2 . A riding space S is located between the front wheels  3  and the rear wheels  4 . The riding space S is surrounded by a rollover protective structure (ROPS)  5 . 
     A seat  6  is disposed in the riding space S.  FIG.  2    is a top view illustrating the power train mechanism  7  and the periphery thereof. In  FIG.  2   , the seat  6  and a cargo bed  8  to be described later are collectively indicated by two-dot chain lines. As illustrated in  FIG.  2   , the seat  6  includes a driver&#39;s seat  6 A located on the left side in the riding space S and a passenger&#39;s seat  6 B located on the right side in the riding space S. As illustrated in  FIG.  1   , the seat  6  includes a seat back  61  that supports the back of a passenger from behind, and a seat cushion  62  on which the passenger seats. 
     The cargo bed  8  is located rearward of the seat  6  of the vehicle body  1 . The power train mechanism  7  is disposed below the cargo bed  8 . The power train mechanism  7  includes an engine  10 , a continuously variable transmission (CVT)  20  disposed on the left side of the engine  10 , and a transmission  30  disposed rearward of the engine  10  and on the right side of the CVT  20 . In the vehicle  100 , the rotational torque output from the engine  10  is transmitted to the front wheels  3  and the rear wheels  4  with the rotational speed changed by the CVT  20  and the transmission  30 . 
     The power train mechanism  7  will now be described. The power train mechanism  7  further includes an intake system  40 , an exhaust system  50 , and a supercharger  70  that supplies supercharged compressed air to the intake system  40 . 
     As illustrated in  FIG.  2   , the engine  10  includes a crankshaft  11  that outputs rotational torque. In the present embodiment, the engine  10  is a 4-cycle straight-four engine in which an axial center O 1  of the crankshaft  11  extends in the vehicle width direction and which has four cylinders  13   a.    
       FIG.  3    is a right side view illustrating the engine  10  and the periphery of the engine  10 . As illustrated in  FIG.  3   , the engine  10  includes an oil pan  17 , a crankcase  12 , a cylinder  13 , a cylinder head  14 , and a cylinder head cover  15  in this order from the bottom. 
     The crankcase  12  is vertically divided into two parts, that is, an upper crankcase  12   a  on the upper side and a lower crankcase  12   b  on the lower side. The crankshaft  11  is rotatably supported between the upper crankcase  12   a  and the lower crankcase  12   b.  The crankcase  12  has a crankcase protrusion  18  protruding in the front side of the cylinder  13 . The supercharger  70  is attached to the upper portion of the crankcase protrusion  18 . 
       FIG.  4    is an exploded perspective view illustrating the supercharger  70  detached from the crankcase protrusion  18 . As illustrated in  FIG.  4   , an upper wall portion  18   a  of the crankcase protrusion  18  is inclined downward toward the front side. The upper wall portion  18   a  is formed on the right side thereof with a supercharger mounting base  18   b  protruding upward in a step manner and to which the supercharger  70  is mounted. The supercharger mounting base  18   b  is formed with an opening  18   c  penetrates the supercharger mounting base  18   b  along the up-down direction. 
     As illustrated in  FIG.  3   , the cylinder  13  is joined to the upper face of the crankcase  12 . The cylinder head  14  is joined to the upper face of the cylinder  13 . The cylinder head cover  15  is fixed to the upper face of the cylinder head  14 . As illustrated in  FIG.  2   , the cylinder  13  includes four cylinders  13   a  extending in the up-down direction of the vehicle. The cylinder head  14  includes four intake ports  14   a  on the front side and four exhaust ports  14   b  on the rear side. 
     As illustrated in  FIG.  2   , the CVT  20  is disposed on the left side of and adjacent to the engine  10 . The CVT  20  includes a CVT housing  21  constituting an outer shell, and a CVT input shaft  22 , a CVT output shaft  23 , a driving pulley  24 , a driven pulley  25 , and an endless belt  26  which are accommodated in the CVT housing  21 . 
     The CVT input shaft  22  extends in the vehicle width direction and is coupled to the crankshaft  11  so as to be able to transmit power. The driving pulley  24  is disposed on the CVT input shaft  22  to rotate integrally with the CVT input shaft  22 . The driven pulley  25  is disposed on the CVT output shaft  23  to rotate integrally with the CVT output shaft  23 . The endless belt  26  is wounded around the driving pulley  24  and the driven pulley  25 . In the CVT  20 , the driving rotation input from the crankshaft  11  is transmitted to the CVT input shaft  22 , then the rotational speed is changed via the driving pulley  24 , the driven pulley  25 , and the endless belt  26 , and then the driving rotation is output from the CVT output shaft 
     As illustrated in  FIG.  1   , the transmission  30  includes a transmission housing  31  forming an outer shell, and a transmission input shaft  32  and a transmission output shaft  33  which are accommodated in the transmission housing  31 . 
     The transmission input shaft  32  extends in the vehicle width direction at the upper front portion of the transmission housing  31  and is coupled to the CVT output shaft  23  so as to be able to transmit power. The transmission output shaft  33  extends in the vehicle width direction at the rear lower portion of the transmission housing  31 . In the transmission  30 , the driving rotation input from the CVT output shaft  23  is transmitted to the transmission input shaft  32 , then the rotational speed is changed, and then the driving rotation is output from the transmission output shaft  33 . 
     As illustrated in  FIG.  1   , the intake system  40  is located on the front side of the engine  10 . The intake system  40  includes an intake pipe  41 , an air cleaner  42 , and an intake duct  43 . The intake pipe  41  includes an intake manifold  44  and a throttle body  45  in this order from the downstream side on an intake path. 
     As illustrated in  FIG.  2   , the intake manifold  44  includes four independent ports  44   a  each connected, at the downstream side, to the corresponding one of the intake ports  14   a  of the cylinder head  14 , and an inlet port  44   b  in which the independent ports  44   a  are integrated, at the upstream side, into a single port. As illustrated in  FIG.  1   , the independent ports  44   a  extend in a direction inclined downward toward the rear side. Referring back to  FIG.  2   , the inlet port  44   b  extends across the upstream ends of the independent ports  44   a,  that is, in the left-right direction at the front ends of the independent ports  44   a  in the drawing. The inlet port  44   b  has an inlet at the left end thereof. 
     The throttle body  45  is connected to the left side of the intake manifold  44 . Specifically, the throttle body  45  is connected to the left end of the inlet port  44   b  of the intake manifold  44 . In the present embodiment, the throttle body  45  includes a single electronically controlled throttle valve  45   a,  and adjusts the amount of air flowing into the engine  10  at the inlet of the intake manifold  44  to control the rotational speed of the engine  10 . 
     The air cleaner  42  is disposed below the seat  6  and in front of the engine  10  with a space therebetween. Specifically, the air cleaner  42  is disposed below the seat cushion  62  of the driver&#39;s seat  6 A. 
     As illustrated in  FIG.  1   , the intake duct  43  has a downstream end connected to the lower rear end of the left side face of the air cleaner  42 . The intake duct  43  extends forward to reach a bonnet space Z. 
     As illustrated in  FIG.  2   , the intake system  40  further includes a compressor inlet pipe  46  and a compressor outlet pipe  47 . The compressor inlet pipe  46  connects the air cleaner  42  to a compressor inlet  71   c , described later, of the supercharger  70 . The compressor outlet pipe  47  connects a compressor outlet  71   d,  described later, of the supercharger  70  to the throttle body  45 . 
     In the intake system  40 , the intake air taken in through the intake duct  43  is filtered by the air cleaner  42  and then sent to the supercharger  70  through the compressor inlet pipe  46 . The intake air is supercharged in the supercharger  70 , discharged as compressed air, and sent to the throttle body  45  through the compressor outlet pipe  47 . In the throttle body  45 , the intake air is adjusted to the flow rate corresponding to the output power required of the engine  10 , and then sent to the intake manifold  44 . In the intake manifold  44 , the intake air is distributed from the inlet port  44   b  to the independent ports  44   a,  and then introduced into the intake ports  14   a.    
     As illustrated in  FIG.  2   , the exhaust system  50  is located on the rear side of the engine  10 . The exhaust system  50  includes an exhaust pipe  51 , an exhaust muffler  52 , and an exhaust gas sensor  53 . The exhaust system  50  further includes a heat cover  56  that covers substantially the entire periphery of the exhaust pipe  51  from above. The exhaust pipe  51  extends rearward from the rear portion of the cylinder head  14 , and includes four independent exhaust pipes  54  connected to the respective exhaust ports  14   b,  and a collecting pipe  55  connected to the downstream ends of the independent exhaust pipes  54  to gather the independent exhaust pipes  54 . The downstream end of the collecting pipe  55  is connected to the exhaust muffler  52 . As illustrated in  FIG.  1   , the exhaust muffler  52  includes a tail pipe  52   a  through which exhaust gas is discharged. 
     In the exhaust system  50 , the exhaust gas discharged from the exhaust ports  14   b  of the cylinder head  14  is discharged into the four independent exhaust pipes  54  and gathered in the collecting pipe  55 , then introduced into the exhaust muffler  52 , purified and silenced in the exhaust muffler  52 , and finally discharged to the atmosphere from the tail pipe  52   a.    
     As illustrated in  FIG.  2   , the supercharger  70  is disposed between the seat  6  and the engine  10  in the front-rear direction. Specifically, the supercharger  70  is located further on the front side than the axial center O 1  of the crankshaft  11 . More specifically, the supercharger  70  is disposed on the front side of the engine  10  and at the side opposite from the side where the CVT  20  is disposed, that is, at the right side of the engine  10 . In other words, the supercharger  70  is close to a second end  11   b  of the crankshaft  11 , the second end being one of axial ends in the direction along the axial center of the crankshaft  11  and not a first end  11   a  coupled to the CVT  20 . 
     As illustrated in  FIG.  4   , the supercharger  70  is attached to the supercharger mounting base  18   b  in a direction inclined from the upper front side to the lower rear side. The supercharger  70  includes a compressor housing  71 , a bearing housing  72 , and a gear housing  73  in this order from the right side. 
     As illustrated in  FIG.  2   , the compressor housing  71  includes the compressor inlet  71   c  at the right end, and the compressor outlet  71   d  protruding upward from the outer circumferential portion. The compressor inlet pipe  46  is connected to the compressor inlet  71   c.  The compressor outlet pipe  47  is connected to the compressor outlet  71   d . An impeller  74  is accommodated in the compressor housing  71 . The supercharger  70  is a centrifugal compressor that compresses the air introduced from the compressor inlet  71   c  with the rotationally driven impeller  74  and discharges the air as compressed air from the compressor outlet  71   d.  The impeller  74  integrally has a rotation shaft  75  extending leftward and penetrating the bearing housing  72  to reach the gear housing  73 . 
     The compressor housing  71  is located further on the right side than the cylinder head  14 . Specifically, a right end  71   a  of the compressor housing  71  is located further on the right side than a right end  14   c  of the cylinder head  14 . As illustrated in  FIG.  3   , a rear end  71   b  of the compressor housing  71  is located further rearward of a front end  14   d  of the cylinder head. The right end  71   a  is a portion in the rightmost of the compressor housing  71  except for the compressor inlet  71   c  and the compressor outlet  71   d.  The rear end  71   b  is a portion in the rearmost of the compressor housing  71  except for the compressor inlet  71   c  and the compressor outlet  71   d.    
     As illustrated in  FIG.  2   , the bearing housing  72  is fixed to the compressor housing  71  from the left side, and includes a bearing  72   a  that rotatably supports the rotation shaft  75 . A left end  72   b  of the bearing housing  72  is further on the left side than the right end  14   c  of the cylinder head. That is, at least a portion of the cylinder head  14  is included in a region where the bearing housing  72  is projected to the rear side of the vehicle. In other words, the bearing housing  72  is located further in the inner side in the vehicle width direction than the compressor housing  71  and the outer end, in the vehicle width direction, of the cylinder head  14 . 
     The gear housing  73  is fixed to the bearing housing  72  from the left side. As illustrated in  FIG.  4   , the supercharger  70  is detachably attached to the supercharger mounting base  18   b  by a plurality of fastening bolts  77  at the lower end of the gear housing  73  with a gasket  76  interposed therebetween. When the supercharger  70  is not attached to the engine  10 , a lid member is attached to the supercharger mounting base  18   b  instead of the supercharger  70  to shut the inside of the crankcase  12  from the outside. Thus, the crankcase  12  can be commonly used regardless of using or not using a supercharger. 
     The gear housing  73  accommodates a supercharger drive mechanism  80  that mechanically and rotationally drives the rotation shaft  75  (see  FIG.  2   ) of the impeller  74  by use of the rotation of the crankshaft  11 . The supercharger drive mechanism  80  extends to the inside of the crankcase  12  through the opening  18   c,  and is coupled to an auxiliary unit drive mechanism  90  (see  FIG.  5   ) disposed inside the crankcase  12  so as to be capable of transmitting power. 
       FIG.  5    is a perspective view schematically illustrating the supercharger drive mechanism  80  and the auxiliary unit drive mechanism  90 . In  FIG.  5   , the crankshaft  11 , pistons  16 , and connecting rods  19  are indicated by two-dot chain lines. As illustrated in FIG.  5 , the auxiliary unit drive mechanism  90  includes a drive gear  91  integrally formed on the crankshaft  11 , an auxiliary unit driving gear  92  meshing with the drive gear  91  from the front upper side, an oil pump driving gear  94  that rotates integrally with the auxiliary unit driving gear  92  via a drive shaft  93  extending from the auxiliary unit driving gear  92  to the right side, and a starter driven gear  96  provided on the left side of the auxiliary unit driving gear  92  with a one-way clutch  95  interposed therebetween. 
     An oil pump gear  97   a  of an oil pump  97  meshes with the oil pump driving gear  94  from below. The oil pump driving gear  94  rotationally drives the oil pump  97  via the oil pump gear  97   a.    
     The starter driven gear  96  meshes with a starter gear  98   a  of a starter  98  from above. The one-way clutch  95  transmits the rotation from the starter  98  to the auxiliary unit driving gear  92 , but does not transmit the rotation from the auxiliary unit driving gear  92  to the starter  98 . That is, when starting the engine  10 , the starter driven gear  96  is rotationally driven by the starter gear  98   a  to rotationally drive the crankshaft  11  via the one-way clutch  95 , the auxiliary unit driving gear  92 , and the drive gear  91 . After the engine  10  has started, the rotation from the crankshaft  11  is cut off by the one-way clutch  95  and is not transmitted to the starter  98 . The oil pump  97  and the starter  98  are examples of engine accessories according to the present disclosure. 
     The supercharger drive mechanism  80  includes, as driving force transmission members, a supercharger driving first gear  81  meshing with the oil pump driving gear  94  from the front upper side, a supercharger driving second gear  82  meshing with the supercharger driving first gear  81  from the upper side, a supercharger driving third gear  83  meshing with the supercharger driving second gear  82  from the upper side, and a planetary gear mechanism  85  coupled to the supercharger driving third gear  83  via a drive shaft  84 . The planetary gear mechanism  85  includes a bottomed cylindrical outer gear  85   a  opened to the right side, three planetary gears  85   b  meshing with the inner wall of the outer gear  85   a,  and a sun gear  85   c  located at the center of the three planetary gears  85   b  and meshing with the planetary gears  85   b.  The sun gear  85   c  is integrally formed on the left end of the rotation shaft  75  of the impeller  74 . In the present embodiment, the rotation of the crankshaft  11  is accelerated by eight times and transmitted to the impeller  74  via the auxiliary unit drive mechanism  90  and the supercharger drive mechanism  80 . That is, the impeller  74  is rotationally driven at a rotational speed higher than the rotational speed of the crankshaft  11 , and compresses the air suctioned from the compressor inlet  71   c  to raise the intake air pressure, and the compressed air is discharged from the compressor outlet  71   d.  The compressed air is supplied to the engine  10  via the compressor outlet pipe  47 , the throttle body  45 , and the intake manifold  44 . The compressed air raises the charging efficiency of the air into the engine  10 , whereby the output power of the engine  10  is increased as compared with an engine without a supercharger. 
     The vehicle  100  according to the embodiment described above has the following effects. 
     (1) Since the supercharger  70  is disposed between the seat  6  and the engine  10  disposed rearward of the seat  6  in the front-rear direction, the center of gravity of the vehicle  100  is located closer to the center in the front-rear direction than when a supercharger is disposed rearward of an engine. This readily improves the handling stability of the vehicle  100 . 
     (2) Since the engine  10  includes the centrifugal supercharger  70  rotationally driven by the supercharger drive mechanism  80 , the supercharging pressure can be readily increased while suppressing an increase in the size of the supercharger as compared with when adopting a displacement type supercharger. Moreover, unlike when adopting an exhaust turbocharger, there is no turbo lag at a low engine rotational speed, and the supercharging pressure can be readily raised with good response to the engine rotational speed. 
     (3) Since the supercharger  70  is attached to the supercharger mounting base  18   b  of the crankcase protrusion  18  from the upper front side, the supercharger  70  can be readily disposed close to the engine  10  and the engine  10  can be readily made small in size in the front-rear direction. Furthermore, since the supercharger drive mechanism  80  includes the supercharger driving first gear  81 , the supercharger driving second gear  82 , the supercharger driving third gear  83 , and the planetary gear mechanism  85  as the driving force transmission members, the speed increase ratio can be readily raised as compared with when transmitting the drive force via a belt. As a result, the rotational speed of the supercharger can be readily increased to be further higher than the engine rotational speed, and the supercharging pressure can be further readily increased. 
     (4) Since the supercharger  70 , the engine  10 , and the exhaust system  50  are disposed in this order from the front side, the supercharger  70  can be readily protected from an affect by heat radiated by the exhaust system  50 . This readily suppresses the rise in the temperature of the compressed air discharged from the supercharger  70 , and the charging efficiency of the intake air into the engine  10  can be readily raised. 
     (5) Since the intake system  40  and the supercharger  70  are located further on the front side than the rotational axial center  01  of the crankshaft  11 , the compressor inlet pipe  46  connecting the supercharger  70  to the intake system  40  and the compressor outlet pipe  47  can be readily made short. As a result, a short intake path readily achieves a good response of the supercharging pressure to the change in the engine rotational speed. 
     (6) In the present embodiment, since the engine  10  is a multi-cylinder engine and the crankshaft  11  extends in the vehicle width direction, the dimension of the engine  10  in the vehicle width direction is large, which may result in small spaces on both sides, in the vehicle width direction, of the engine  10  and thus restrict the arrangement of other components in the spaces. However, since the intake system  40  and the supercharger  70  are disposed on the front side of the rotational axial center O 1  of the crankshaft  11  and the exhaust system  50  is disposed on the rear side of the rotational axial center O 1  of the crankshaft  11 , there is no need to arrange the pipes of the intake system  40  and the exhaust system  50  so as to pass across the engine  10  in the front-rear direction through the spaces. Thus, even a multi-cylinder engine can be readily mounted in a limited mounting space by arranging the pipes in a compact manner. 
     (7) Since the rear end  71   b  of the compressor housing  71  is located further on the rear side than the front end  14   d  of the cylinder head  14 , the supercharger  70  can be mounted with the suppressed amount of the supercharger  70  protruding forward with respect to the cylinder head  14 . 
     (8) The right end  71   a  of the compressor housing  71  is located further on the right side than the right end  14   c  of the cylinder head  14 , and the left end  72   b  of the bearing housing  72  is located further on the left side than the right end  14   c  of the cylinder head  14 . As a result, the supercharger  70  can be readily mounted with the suppressed amount of the supercharger  70  protruding outward in the vehicle width direction with respect to the cylinder head  14 . 
     (9) The CVT  20  is disposed at the first end  11   a  on the left side of the crankshaft  11  in the direction along the axial center of the crankshaft  11 , and the supercharger  70  is disposed close to the second end  11   b  on the right side of the crankshaft  11 . As a result, the supercharger  70  and the CVT  20  are disposed at different sides with respect to the engine  10  in the direction along the axial center of the crankshaft  11 . This enables the supercharger  70  and the CVT  20  to be disposed in a compact manner without interfering with each other. In the present disclosure, described as an example is the case where the CVT  20  is disposed on the left side of the engine  10 . However, the effect described above is similarly exhibited for a case where a transmission is disposed instead of the CVT  20 . 
     (10) The intake system  40  includes the intake manifold  44  having the inlet port  44   b  to which the compressed air discharged from the supercharger  70  is supplied and the plurality of independent ports  44   a,  and the single throttle valve  45   a  disposed on the intake path on the upstream side of the inlet port  33   b.  This configuration in which the amount of suctioned air is controlled via the single throttle valve  45   a  can reduce the number of parts and cost as compared with a case where a throttle valve is provided to each of the plurality of cylinders  13   a.    
     (11) Driving force can be transmitted to the supercharger drive mechanism  80  by use of the auxiliary unit drive mechanism  90  that transmits driving force from the crankshaft  11  to the oil pump  97  and the starter  98 . For a case where the supercharger  70  is not mounted on an engine, the engine and the auxiliary unit drive mechanism  90  can be commonly used, so that variations of parts can be readily reduced. 
     (12) Since the supercharger drive mechanism  80  includes the planetary gear mechanism  85 , the speed increase ratio can be readily increased. This further readily increases the rotational speed of the supercharger  70  with respect to the engine rotational speed, and thereby the supercharging pressure can be further readily increased. 
     Second Embodiment 
     A power train mechanism  207  mounted on a vehicle  200  according to a second embodiment will be described with reference to  FIG.  6   . In the following description, members common to those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.  FIG.  6    is a plan view illustrating an engine  210  and the periphery thereof of the power train mechanism  207 . As illustrated in  FIG.  6   , the engine  210  is different from the engine  10  according to the first embodiment in the configurations of an intake manifold  240 , a throttle body  245 , and a compressor outlet pipe  247 . 
     The intake manifold  240  includes a chamber  241 , and four independent ports  242  branching from the outlet of the chamber  241  and connected to respective intake ports  14   a  of a cylinder head  14 . The chamber  241  has a chamber inlet  241   a  to which the compressor outlet pipe  247  is connected. The chamber inlet  241   a  protrudes downward at the lower portion of the front end of the intake manifold  240 . The compressor outlet pipe  247  connects a compressor outlet  71   d  to the chamber inlet  241   a.  The throttle body  245  is provided adjacent to the four independent ports  242 . The throttle body  245  includes four throttle valves  245   a  that open and close the respective four independent ports  242  by use of electronic control. 
     According to the present embodiment, since each of the plurality of throttle valves  245   a  is provided for the corresponding one of a plurality of cylinders  13   a,  the amount of intake air introduced into each cylinder  13   a  can be readily adjusted optimally. This readily improves the performance of the engine  210 . 
     Third Embodiment 
     A power train mechanism  307  mounted on a vehicle  300  according to a third embodiment will be described with reference to  FIG.  7   . In the following description, members common to those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.  FIG.  7    is a plan view illustrating an engine  310  and the periphery thereof of the power train mechanism  307 . As illustrated in  FIG.  7   , the power train mechanism  307  is different from the power train mechanism  7  according to the first embodiment in that the power train mechanism  307  includes an intercooler  320  as a heat exchanger, and an intercooler inlet pipe  321  and an intercooler outlet pipe  322  instead of the compressor outlet pipe  47 . 
     The intercooler  320  is disposed above the engine and between a seat  6  and a cargo bed  8 . In the present embodiment, the intercooler  320  is of air-cooling type that cools, by exchanging heat with a traveling wind, the compressed air of which temperature has risen by compression in a supercharger  70 . The intercooler  320  has an intercooler inlet  320   a  protruding downward at the left end and an intercooler outlet  320   b  protruding rightward at the right end. The intercooler inlet pipe  321  connects a compressor outlet  71   d  to the intercooler inlet  320   a.  The intercooler outlet pipe  322  connects the intercooler outlet  320   b  to a throttle body  45 . 
     According to the present embodiment, the compressed air of which temperature has risen by compression in the supercharger  70  is cooled by the intercooler  320 , whereby the charging efficiency of the air into the engine  310  can be raised. 
     Fourth Embodiment 
     A power train mechanism  407  mounted on a vehicle  400  according to a fourth embodiment will be described with reference to  FIG.  8   . In the following description, members common to those of the first to third embodiments are denoted by the same reference numerals, and description thereof is omitted.  FIG.  8    is a plan view illustrating an engine  410  and the periphery thereof of the power train mechanism  407 . As illustrated in  FIG.  8   , the power train mechanism  407  is different from the power train mechanism  207  according to the second embodiment in that the power train mechanism  407  includes the intercooler  320  described in the third embodiment, and an intercooler inlet pipe  321  and an intercooler outlet pipe  323  instead of the compressor outlet pipe  247 . The intercooler outlet pipe  323  connects an intercooler outlet  320   b  to a chamber inlet  241   a.    
     According to the present embodiment, the compressed air of which temperature has risen by compression in a supercharger  70  is cooled by the intercooler  320 , whereby the charging efficiency of the air into the engine  410  can be raised. 
     The present disclosure is not limited to the configuration described in the embodiments described above, and various modifications can be made. 
     In the embodiments described above, the supercharger drive mechanism  80  includes a plurality of gears, but the present invention is not limited thereto.  FIG.  9    illustrates a supercharger drive mechanism  180  according to an exemplary modification. As illustrated in  FIG.  9   , the supercharger drive mechanism  180  is different from the supercharger drive mechanism  80  in that the supercharger drive mechanism  180  includes a supercharger driving first sprocket  181 , a supercharger driving second sprocket  182 , a supercharger driving gear  183 , and a chain  184  instead of the supercharger driving first gear  81  and the supercharger driving second gear  82 . 
     The supercharger driving first sprocket  181  is disposed on a drive shaft  93  to rotate integrally with the drive shaft  93 . The supercharger driving second sprocket  182  is disposed above a supercharger driving third gear  83 . The supercharger driving gear  183  is coaxially provided on the supercharger driving second sprocket  182  to rotate integrally with the supercharger driving second sprocket  182 , and meshes with the supercharger driving third gear  83  from above. The chain  184  is wounded around the supercharger driving first sprocket  181  and the supercharger driving second sprocket  182 . 
     In the supercharger drive mechanism  180 , the rotation of a drive shaft  84  is transmitted to the supercharger driving third gear  83  via the supercharger driving first sprocket  181 , the supercharger driving second sprocket  182 , the supercharger driving gear  183 , and the chain  184 . Thus, the rotation of a crankshaft  11  is transmitted to a rotation shaft  75  of the impeller  74  via the supercharger drive mechanism  180 .