Patent Publication Number: US-6655307-B2

Title: Personal watercraft on which supercharger is mounted

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2001-216518, filed on Jul. 17, 2001, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a personal watercraft on which an engine with a supercharger is mounted, and particularly to an oil supply passage through which oil is supplied to the supercharger. 
     2. Description of Background Art 
     Two-cycle engines have generally been used to power personal watercraft. However, to meet recent requirements to reduce environmental pollution, increasing use has been made of four-cycle engines. 
     Unfortunately, the output of a four-cycle engine is less than that of a two-cycle engine with the same displacement. To compensate for this insufficient output, consideration has been given to mounting a supercharger on these four-cycle engines. For example, the present applicant has already proposed, in Japanese Patent Laid-Open No. 2001-146197, a personal watercraft on which a four-cycle engine with a supercharger is mounted. 
     In this personal watercraft, as shown in FIGS. 11 and 12, a four-cycle engine  2  with a supercharger  3  is mounted in a watercraft body  1 . The supercharger  3  is disposed on a rear side of the engine  2 , and an oil tank  5  is disposed on a front side of the engine  2 . 
     As shown in FIG. 13, an oil pump  4  is provided on a front portion of the engine  2  at a position under the oil tank  5 . Oil press-fed from the oil pump  4  is supplied to a main gallery  2   a  of the engine  2  via piping  6   d , an oil filter  6 , and piping  6   e , and is then supplied from the main gallery  2   a  to respective components of the engine  2 . 
     Oil is also supplied from the main gallery  2   a  to a bearing portion  3   a  of the supercharger  3  via an oil passage  2   d  formed in a lower bearing portion  2   c  of a crankshaft  2   b , an oil passage  2   f  formed in an upper bearing portion  2   e  of the crankshaft  2   b , and piping  2   g.    
     The oil, which has been used for lubricating the bearing portion  3   a  of the supercharger  3  is recovered, via piping  3   b , to an oil pan  2   i  provided in a lower portion of the engine  2 , and is recovered from piping  6   a  to the oil tank  5  via the oil pump  4 . 
     According to the above-described personal watercraft in which the supercharger  3  is disposed on the rear side of the engine  2  and the oil tank  5  is disposed on the front side of the engine  2 , the problem of having the oil stored in oil tank  5  being heated by the supercharger  3  is eliminated. 
     Another problem occurs however, in the above-described related art personal watercraft. Since oil is supplied from the main gallery  2   a  to the bearing portion  3   a  of the supercharger  3  via the oil passage  2   d  formed in the lower bearing portion  2   c  of the crankshaft  2   b , the oil passage  2   f  formed in the upper bearing portion  2   e  of the crankshaft  2   b , and the piping  2   g , it takes more time than is desirable for oil to be supplied to the supercharger  3  after starting the engine  2 . 
     As a result, it is difficult to ensure a speedy, positive operation of the supercharger. 
     SUMMARY AND OBJECTS OF THE INVENTION 
     An object of the present invention is to solve the above-described problem and to provide a personal watercraft on which an engine with a supercharger is mounted, which is capable of ensuring a speedy, positive operation of the supercharger. 
     To achieve the above object, the present invention provides a personal watercraft on which an engine with a supercharger is mounted, having an engine for driving a jet propelling pump is provided in a watercraft body formed by a hull and a deck in such a manner as to extend in a length direction of the watercraft body, a supercharger is provided in a longitudinal direction of the engine; and an oil supply passage for communicating between the supercharger and an end portion of a main gallery of oil provided in parallel to a crankshaft of the engine. 
     Further, the present invention provides an oil pump on a portion, on a front side of the watercraft body, of the engine and the supercharger is provided on a portion, on a rear side of the watercraft body, of the engine; and the supercharger and a rear end portion of the main gallery are communicated to each other via the oil supply passage. 
     In addition, in the present invention, the oil supplied to the supercharger is used for lubricating a bearing portion of the supercharger, and the oil is supplied to an oil jacket formed in a bearing casing to cool the bearing casing. An oil outlet in the supercharger is disposed at a position higher than an oil level at the time of stoppage of the engine. 
     Moreover, the engine of the present invention is a dry sump engine, an oil tank is provided on an extension of a crankshaft of the engine, and a one-way valve is interposed in an oil return passage communicated to the oil outlet in the supercharger. 
     The present invention as described above provides the following functions and effects. 
     As mentioned, the engine for driving the jet propelling pump is provided in the watercraft body formed by the hull and the deck in such a manner as to extend in a length direction of the watercraft body, and the supercharger is provided in a longitudinal direction of the engine; and the supercharger and an end portion of the main gallery of oil provided in parallel to the crankshaft of the engine communicate with each other via the oil supply passage. As a result, oil is supplied from the end portion of the main gallery to the supercharger directly via the oil supply passage. Accordingly, the time required to supply oil to the supercharger after start of the engine is shortened, and hence, a speedy, positive operation of the supercharger can be ensured. 
     In the related art, one end portion of the main gallery must be closed by a plug (see reference numeral  2   p  in FIG.  13 ). By contrast, with configuration of the engine and supercharger used in the present invention, it is possible to eliminate the need for such a plug. 
     The oil pump of the present invention is provided on a portion, on the front side of the watercraft body, of the engine, and the supercharger is provided on a portion, on the rear side of the watercraft body, of the engine. Further, the supercharger and a rear end portion of the main gallery communicate with each other via the oil supply passage. As a result, it is possible to readily supply oil to the supercharger disposed on the rear side of the engine. 
     With the configuration of the present invention, oil supplied to the supercharger is used for lubricating the bearing portion of the supercharger, and also the oil is supplied to the oil jacket formed in the bearing casing to cool the bearing casing. As a result, it is possible to use the oil supplied to the supercharger not only for lubricating the bearing portion of the supercharger, but also for cooling the bearing casing. 
     In the case of lubricating the bearing portion of the supercharger and cooling the bearing casing by using the oil supplied to the supercharger, to readily supply a large amount of oil is required, as compared with the related art personal watercraft. 
     However, according to the personal watercraft of the present invention, since oil is supplied from the end portion of the main gallery to the supercharger directly via the oil supply passage, a large amount of oil can be readily supplied to the supercharger 
     Further, with in the present invention, the oil outlet in the supercharger is disposed at a position higher than an oil level at the time of stoppage of the engine. As a result, when the operation of the engine is stopped, oil in the supercharger is readily discharged via the oil outlet. 
     If oil remains in the supercharger at a high temperature immediately after the engine is stopped, the remaining oil is likely to be carbonized. If this occurs, the entire oil circulating in the engine is likely to deteriorate. The present invention, however, solves this problem, by providing a means by which oil in the supercharger is readily discharged via the oil outlet when the engine is stopped. Accordingly, the amount of oil remaining in the supercharger after the engine is stopped is made as small as possible, thus reducing the deterioration of the entire oil circulating in the engine. 
     As described earlier, the engine of the present invention is a dry sump engine, and the oil tank is provided on an extension of the crankshaft of the engine. As a result, it is possible to lower an oil level at the time of stoppage of the engine. This, in turn, makes it possible to more readily discharge oil remaining in the supercharger from the oil outlet, and hence to more effectively reduce the deterioration of the entire oil circulating in the engine. 
     Further, a one-way valve is interposed in the oil return passage communicating with the oil outlet in the supercharger. As a result, it is possible to eliminate the problem that when the personal watercraft is turned over, oil counter flows and remains in the supercharger which still has a high temperature. 
     This feature helps further to prevent carbonization of oil, and hence to more certainly reduce the deterioration of the entire oil circulating in the engine. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
     FIG. 1 is a schematic side view showing one example of a personal watercraft on which an engine with a supercharger is mounted according to the present invention; 
     FIG. 2 is a plan view of the personal watercraft shown in FIG. 1; 
     FIG. 3 is a partial, enlarged sectional view taken on line III—III of FIG. 1 (with parts partially omitted); 
     FIG. 4 is a partial, enlarged sectional view taken on line IV—IV of FIG. 1, mainly showing the engine  20 ; 
     FIG. 5 is a right side view of the engine  20 ; 
     FIG. 6 is a left side view of the engine  20 ; 
     FIG. 7 is a schematic perspective view of the engine  20  as seen from an obliquely rear direction; 
     FIG. 8 is an enlarged view of a portion shown in FIG. 5; 
     FIG. 9 is a diagram showing an oil circulation route; 
     FIG. 10 is a sectional view of a turbo charger  140 ; 
     FIG. 11 is a view illustrating a related art personal watercraft; 
     FIG. 12 is a view illustrating the related art personal watercraft shown in FIG. 11; and 
     FIG. 13 is a view illustrating the related art personal watercraft shown in FIG.  11 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 
     FIG. 1 is a schematic side view showing one embodiment of a personal watercraft on which an engine with a supercharger according to the present invention is mounted; FIG. 2 is a plan view of the personal watercraft; and FIG. 3 is a partial, enlarged sectional view taken on line III—III of FIG. 1 (with parts partially omitted). 
     Referring to these figures (particularly, to FIG.  1 ), a personal watercraft  10  is a saddle-type small watercraft, which is operable by a driver sitting on a seat  12  provided on a watercraft body  11  and holding a steering handlebar  13  provided with a throttle lever. 
     The watercraft body  11  has a floating structure that a hull  14  is joined to a deck  15  so as to form a space  16  therein. In the space  16 , an engine  20  is mounted on the hull  14 , and a jet pump or jet propelling pump  30  functioning as propelling means to be driven by the engine  20  is provided on a rear portion of the hull  14 . 
     The jet pump  30  has a flow passage  33  extending from a water inlet  17  opened in a bottom of the hull  14  to both a jet port  31  opened in a rear end portion of the hull  14  and a nozzle  32 , and an impeller  34  disposed in the flow passage  33 . A shaft  35  of the impeller  34  is connected to an output shaft  21   a  of the engine  20 . When the impeller  34  is rotated by the engine  20 , water taken in via the water inlet  17  is jetted from the jet port  31  via the nozzle  32 , to propel the watercraft body  11  in a forward direction. 
     A rotational speed of the engine  20 , that is, a propelling force of the jet pump  30  is controlled by a turning operation of a throttle lever  13   a  (see FIG. 2) of the steering handlebar  13 . The nozzle  32  is coupled to the steering handlebar  13  via a steering wire (not shown), and is turned by operation of the steering handlebar  13 , to change a running course. The figures also show a fuel tank  40  and a storing chamber  41 . 
     FIG. 4 is a view mainly showing the engine  20 , which is a partial, enlarged sectional view taken on line IV—IV of FIG. 1 (with parts partially omitted); FIG. 5 is a right side view of the engine  20 ; FIG. 6 is a left side view of the engine; FIG. 7 is a schematic perspective view of the engine  20  as seen from an obliquely rearward direction, and FIG. 8 is an enlarged view of a portion shown in FIG.  5 . 
     The engine  20  is a DOHC in-line four-cylinder/four-cycle engine, which is particularly of a dry sump according to this embodiment. As shown in FIG. 1, a crankshaft  21  of the engine  20  extends along the longitudinal direction of the watercraft body  11 . 
     As shown in FIGS. 4 and 7, a surge tank (intake chamber)  22  which communicates with an intake port and an intercooler  23  connected to the surge tank  22  are disposed on the left side of the engine  20  as seen in the running direction of the watercraft body  11 . An exhaust manifold  24 , which is connected to and communicates with exhaust ports  20   o , is disposed on the right side of the engine  20 . 
     As shown in FIGS. 6 and 7, a turbo-charger (supercharger)  140  is disposed at the back of the engine  20 . An exhaust outlet  24   o  of the exhaust manifold  24  is connected to a turbine portion  140 T of the turbo-charger  140 , and the intercooler  23  is connected to a compressor portion  140 C of the turbo-charger  140  via piping  26  (see FIG.  7 ). FIG. 7 shows cooling hoses  23   a  and  23   b  connected to the intercooler  23 . 
     After being used for rotating a turbine in the turbine portion  140 T of the turbo-charger  140 , an exhaust gas passes piping  27   a , an anti-counterflow chamber  27   b  for preventing counterflow upon turn-over of the watercraft body  11 , a water muffler  27   c , and an exhaust/drainage pipe  27   d , and lastly, flows into the water stream caused by a jet pump  30 . This is shown in FIGS. 1 and 2. 
     FIG. 1 shows intake ducts  18  and  19  for introducing atmospheric air outside the watercraft body  11  in the space  16  inside the watercraft body  11 . Lower ends  18   a  and  19   a  of the intake ducts  18  and  19  are provided, in the watercraft body  11 , at positions lower than that of the turbo-charger  140 . In other words, the turbo-charger  140  is disposed at a position higher than those of the lower ends  18   a  and  19   a  of the intake ducts  18  and  19 . The turbo-charger  140  is located, in the space  16  in the watercraft body  11 , at an approximately central position in the height direction. 
     As shown in FIGS. 4 to  7 , in a front portion of the engine  20  as seen in the running direction of the watercraft body  11  (equivalent to a left portion in FIGS.  1  and  5 ), an oil tank  50  and an oil pump  80  integrated with the oil tank  50  are provided on an extension of the crankshaft  21 . The oil pump  80  is provided in the oil tank  50 . 
     The oil tank  50  includes a tank main body (one divided case)  60  joined to a front plane of the engine  20 , and a cover (the other divided case)  70  joined to a front plane of the tank main body  60 . 
     Referring to FIGS. 4 and 6, in the oil tank  50 , a water-cooled oil cooler  90  is provided on a front surface of the tank main body  60  and an oil filter  100  is provided on an upper portion of the oil tank  50 . 
     Referring to FIGS. 4,  5  and  8 , the tank main body  60  includes a joint plane  61  joined to the front plane of the engine  20 , a joint plane  62  jointed to the cover  70 , an oil pump  80  mounted on mounting plane  63 , and a water-cooled oil cooler  90  mounted on mounting portion  64 . The tank main body  60  further includes an oil storing portion  65  which is defined by partition walls forming the mounting planes and outer walls, and is formed into a vertically-elongated shape as a whole. Also included are a cover portion  66  for covering drive chambers for an ACG  110 , balancer shafts  114 L and  114 R, and a starter motor  120 . As shown in FIG. 6, the tank main body  60  also includes a mounting portion  68  on which the oil filter  100  is mounted. 
     The joint plane  61  of the tank main body  60  is joined to the front plane of the engine  20  in a state that the above-described components are covered with the cover portion  66  of the tank main body  60 , and the tank main body  60  is integrally fixed to the front plane of the engine  20  with a bolt (not shown). In addition, the tank main body  60  is mounted to the front plane of the engine  20  after the oil pump  80  and the oil cooler  90  are mounted to the tank main body  60 . 
     The cover  70  includes a joint plane  71  joined to the tank main body  60 , an oil supply port  72 , a pressing portion  73  for pressing a relief valve  130 , and an accommodating portion  74  for accommodating the oil cooler  90  (see FIG.  6 ), and an oil storing portion  75  defined by the outer walls and partition walls. 
     The oil pump  80  includes a first case  81  joined to the tank main body  60 , a second case  82  jointed to the first case  81 , a pump shaft  83  provided so as to pass through the first and second cases  81  and  82 , an oil recovering inner/outer rotor  84  connected to the pump shaft  83  in the first case  81 , and an oil supplying inner/outer rotor  85  connected to the pump shaft  83  in the second case  82 . 
     The oil recovering inner/outer rotor  84  forms an oil recover pump in cooperation with the first case  81 , and the oil supplying inner/outer rotor  85  forms an oil supply pump in cooperation with the first and second cases  81  and  82 . 
     A joint plane, to be joined to the tank main body  60 , of the first case  81  is joined to the joint plane  63  which is formed on the front plane of the tank main body  60  and has the same shape as that of the joint plane of the first case  81 . The oil pump  80  is mounted to the front plane of the tank main body  60  with a bolt  88 . 
     After the oil pump  80  is mounted to the tank main body  60 , a coupling  89  is fixed, from the back surface side of the tank main body  60 , to a rear end of the pump shaft  83  with a bolt. 
     After the oil pump  80  and its coupling  89  are mounted to the tank main body  60 , the oil cooler  90  is mounted to the tank main body  60 , and then the tank main body  60  is mounted to the front plane of the engine  20  in such a manner that the coupling  89  is coupled to a coupling  111  provided at the leading end of the ACG shaft. 
     The water-cooled oil cooler  90  is mounted to the front surface side of the oil cooler  90  mounting portion  64  of the tank main body  60 . 
     Referring to FIGS. 4 and 6, the mounting portion  64  of the tank main body  60  has an upper hole  64   a  and a lower hole  64   b  communicating with an oil passage to be described later. 
     On the other hand, the oil cooler  90  has a plurality of heat exchange plates  91  allowing oil to pass therethrough, an oil inlet pipe  92  communicating with the insides of upper portions of the plates  91 , and an oil outlet pipe  93  communicating with the insides of lower portions of the plates  91 . 
     The oil cooler  90  is mounted to the mounting portion  64  of the tank main body  60  in such a manner that the inlet pipe  92  is connected to the upper hole  64   a  of the tank main body  60  and the outlet pipe  93  is connected to the lower hole  64   b  of the tank main body  60 . 
     Referring to FIGS. 4 and 6, a cooling water introducing pipe  97  communicating with a hole  64   c  opened in the mounting portion  64  for introducing cooling water in the mounting portion  64  and the oil cooler accommodating portion  74  of the cover  70  is provided in the tank main body  60 . The cover  70  is provided with a water discharge pipe  78 . A cooling water hose  97   a  from a cooling water takeoff portion  30   a  (see FIG. 7) in the jet pump  30  is connected to the introducing pipe  97  directly, that is, without interposition of any cooling object therebetween, and an drainage pipe  23   c  is, as shown in FIG. 6, connected to the discharge pipe  78 . Water from the drainage pipe  78  is supplied to a water jacket of the exhaust manifold  24  via the drainage pipe  23   c.    
     As can be seen in FIGS. 5 and 8, the tank main body  60 , the oil pump  80 , and the oil cooler  90  are must be first mounted on the front plane of the engine  20  as described above. After that, a rear end  131  of a relief valve  130  is then fitted in a hole  82   a  formed in a front plane of the second case  82  of the oil pump  80  and the cover  70  is joined and bolted to a front plane of the tank main body  60  in such a manner that a leading end  132  of the relief valve  130  is pressed by the above-described pressing portion  73 . The relief valve  130  is thus horizontally disposed. 
     In a state that the cover  70  is joined to the tank main body  60 , a single oil storing portion is formed by both the oil storing portions  65  and  75 . The oil filter  100  is mounted to the oil filter  100  mounting portion  68  of the tank main body  60 . 
     In a state that the engine  20  is mounted on the watercraft body  11 , the engine  20  and the oil filter  100  are aligned with an opening  15   a  of the deck  15  as shown in FIGS. 2 and 4. The opening  15   a  of the deck  15  is opened by removing the seat  12  from the watercraft body  11 . 
     In a state that the oil tank  50  (including the tank main body  60 , the cover  70 , and the oil pump  80 , the oil cooler  90  and the relief valve  130  contained in the cover  70 ) is mounted to the front plane of the engine  20 , and the oil filter  100  is mounted to the mounting portion  68  of the tank main body  60 , the oil passages discussed below are formed. 
     Referring to FIGS. 5 and 8, an oil recovery passage  51  is formed between the front plane of the tank main body  60  and the back surface of the first case  81  of the oil pump  80 . The recovery passage  51  includes an oil passage  51   a  formed on the tank main body  60  side, and an oil passage  51   b  which is formed in a portion, on the first case  81  side, of the oil pump  80  in such a manner as to be opposed to the oil passage  51   a.    
     A lower end  51   c  of the oil recovery passage  51  communicates with an oil pan  28  of the engine  20  via a pipe  52 , and an upper end  51   d  of the oil recovery passage  51  communicates with a recovery oil suction port  81   i  formed in a portion, on the first case  81  side, of the oil pump  80 . 
     Similarly, a recovery oil discharge passage  53  between the front plane of the tank main body  60  and the back surface of the first case  81  of the oil pump  80  is formed. The recovery oil discharge passage  53  includes an oil passage  53   a  formed on the tank main body  60  side, and a recovery oil discharge port  81   o  which is formed in a portion, on the first case  81  side, of the oil pump  80  in such a manner as to be opposed to the oil passage  53   a.    
     An upper end  53   b  of the recovery oil discharge passage  53  is opened in the oil tank  50  (that is, in the oil storing portions). 
     On the other hand, a supplied oil suction passage  54  and a supplied oil discharge passage  55  are formed between the front plane of the first case  81  of the oil pump  80  and the back surface of the second case  82  of the oil pump  80 . 
     A lower end  54   a  of the suction passage  54  is opened in the oil tank  50  (that is, in the oil storing portions), and an upper end  54   b  of the suction passage  54  communicates with a supplied oil suction port  82   i  of an oil supply pump. A screen oil filter  54   c  is provided in the suction passage  54 . 
     A lower end  55   a  of the discharge passage  55  communicates with a supplied oil discharge port  82   o  of the oil supply pump. An upper end  55   b  of the discharge passage  55  passes through an upper portion of the first case  81  in the horizontal direction, to communicate with a horizontal hole  60   a  formed in the tank main body  60 . The horizontal hole  60   a  communicates with a vertical hole  60   b  formed in the tank main body  60 . 
     An upper end  60   c  of the vertical hole  60   b  is opened in the oil filter  100  mounting portion  68  in such a manner as to be formed into a ring-shape in a plan view. An oil flow-in passage  101  of the oil filter  100  communicates with the upper end  60   c  of the vertical hole  60   b.    
     The mounting hole  82   a  of relief valve  130 , described above, is opened in the discharge passage  55 , and the relief valve  130  is mounted in the mounting hole  82   a.    
     A male screw is provided in an oil outlet pipe  102  in the oil filter  100 . The oil filter  100  is mounted to the mounting portion  68  of the tank main body  60  by screwing the male screw portion of the oil outlet pipe  102  in a female thread hole  60   d  formed in the mounting portion  68  of the tank main body  60 . 
     As shown in FIG. 6, in the tank main body  60 , a vertical hole  60   e  and a horizontal hole  60   f  communicating with a lower end of the vertical hole  60   e  are formed in a lower portion of the female thread hole  60   d . In addition, the horizontal hole  60   f  communicates with the inlet pipe  92  of the oil cooler  90  via the upper hole  64   a  formed in the oil cooler  90  mounting portion  64 . 
     On the other hand, as shown in FIGS. 4 to  6 , the outlet pipe  93  of the oil cooler  90  is connected to the lower hole  64   b  of the tank main body  60 . An oil passage  60   g , communicating with the lower hole  64   b , and an oil distribution passage  60   h , communicating with the passage  60   g , are formed in the lower hole  64   b . The oil distribution passage  60   h  communicates with three passages: a main gallery oil supply passage  60   i  for supplying oil to a main gallery  20   a  of the engine  20  (see FIG.  5 ), a left balancer oil supply passage  60   j  for supplying oil to a bearing portion of the left balancer  114 L, and a right balancer oil supply passage  60   k  for supplying oil to a bearing portion of the right balancer  114 R. 
     One end of the oil distribution passage  60   h  is closed with a plug  60   n  (see FIG.  6 ). 
     A route of oil supplied to the main gallery  20   a  of the engine  20  is as shown in FIG. 9 (which is an oil circulation route diagram). 
     The route of oil supplied to the main gallery  20   a  is basically classified into two routes. 
     The first route extends from a route  20   b  (see FIG. 5) to a bearing portion of the crankshaft  21 . Oil is supplied to the bearing portion of the crankshaft  21  via such a first route. 
     The second route extends from a rear end  20   al  of the main gallery  20   a  to a turbine bearing portion of the turbo-charger  140  via a pipe  25   a  (see FIG.  7 ). Oil is supplied to the turbine bearing portion of the turbo-charger  140  via such a second route for cooling and lubricating the turbine bearing portion. The oil, which has been used for cooling and lubricating the turbine bearing portion of the turbo-charger  140 , is recovered to the oil pan  28  via pipes  25   b  and  25   c  (see FIG.  6 ). 
     The oil, which has been supplied to the bearing portion of the crankshaft  21 , is then supplied to a cam journal  20   d  portion and a lifter portion of a cylinder head via a route  20   c  for lubricating the cam journal  20   d  portion and the lifter portion, and is returned to the oil pan  28  via a chain chamber  20   i.    
     The oil, which has been supplied to the bearing portion of the crankshaft  21 , is then supplied to the ACG, a piston back side jetting nozzle, a connecting rod, a cam chain, and a starter needle, and is returned to the oil pan  28  via the corresponding recovery passages. FIG. 5 shows a jet nozzle  20   e  for jetting oil to the back side of the piston, a passage  20   f  for communicating with the connecting rod portion, a cam chain  20   g , and a return passage  20   h  for returning oil from an ACG chamber  110   c.    
     The oil, which has been supplied to the ACG chamber  110   c , is returned to the oil pan  28  via the return passage  20   h . Used oil to be jetted from the jet nozzle  20   e  to the back side of the piston, oil having been supplied to the connecting rod, and oil having been supplied to the starter needle are each returned to the oil pan  28  via a crank chamber  20   j.    
     As is apparent from the above description, referring mainly to FIG. 9, the general flow of oil is as follows: 
     Oil tank  50 →suction passage  54 →screen oil filter  54   c →oil pump (supply pump)  80 →discharge passage  55  (and relief valve  130 , horizontal hole  60   a , vertical hole  60   b , and ring-shaped opening  60   c )→oil filter  100 →vertical hole  60   e  and horizontal hole  60   f →oil cooler  90 →oil passage  60   g  and oil distribution passage  60   h →main gallery oil supply passage  60   i , left balancer oil supply passage  60   j  and right balancer oil supply passage  60   k →main gallery  20   a , left balancer  114 L and right balancer  114 R. 
     The relief oil, denoted by character RO, flowing from the relief valve  130  is directly returned to the inside of the oil tank  50 . 
     The oil, which has been supplied to the left balancer  114 L and the right balancer  114 R, is returned to the oil pan  28  via the crank chamber  20   j.    
     The oil, which has been supplied from the main gallery  20   a  to the above-described respective portions, is returned to the oil pan  28  as described above. 
     The oil thus returned to the oil pan  28  is the recovered to the oil tank  50  via the pipe  52 , the oil recovery passage  51 , the oil pump (recovery pump)  80 , and the recovery oil discharge passage  53 , and is circulated again from the suction passage  54  to the above-described portions by way of the above-described routes. 
     FIG. 10 is a sectional view showing the turbo-charger  140 . 
     As described above, the turbo-charger  140  includes the turbine portion  140 T and the compressor portion  140 C, and also includes a bearing casing  141  for connecting the turbine portion  140 T to the compressor portion  140 C. 
     A bearing portion (chamber for accommodating a bearing member)  142  is provided in the bearing casing  141 , and a turbine shaft  143  is rotatably supported by a bearing member (ceramic ball bearing)  142   a  of the bearing portion  142 . A turbine blade  143 T is fixed to a portion, on the turbine portion  140 T side, of the turbine shaft  143 , and a compressor blade  143 C is fixed to a portion, on the compressor portion  140 C side, of the turbine shaft  143 . 
     Accordingly, the turbine shaft  143  is rotated in the course that exhaust gas from the above-described exhaust manifold  24  is discharged from an exhaust outlet T 2  to the above-described exhaust pipe  27   a  (see FIGS. 1 and 2) via an exhaust passage T 1  in the turbine portion  140 T. As a result, the compressor blade  143 C is rotated, so that air from an air intake port C 1  communicated to an intake box (not shown) is press-fed from the above-described piping  26  (see FIG. 7) to the intercooler  23  via an intake passage C 2  in the compressor portion  140 C. 
     An oil inlet  144  is provided in an upper portion of the bearing casing  141 . The oil inlet  144  communicates with the rear end portion  20   al  of the main gallery  20   a  via the above-described pipe  25   a  (see FIG. 7) functioning as an oil supply passage. The pipe  25   a  is connected to the oil inlet  144  via an orifice bolt  145 . 
     An oil jacket  146  is formed in the bearing casing  141 . The oil inlet  144  communicates with the oil jacket  146  via an oil passage  144   a . The bearing portion  142  communicates with the oil inlet  144  via a narrow oil passage  144   b.    
     Accordingly, the oil having entered from the oil inlet  144  is supplied to the oil jacket  146  via the oil passage  144   a , to cool the bearing casing  141 , the bearing portion  142 , and the turbine shaft  143  and its neighborhood, and is also supplied to the bearing portion  142  via the oil passage  144   b , to lubricate the bearing portion  142 . 
     The oil supplied to the oil jacket  146  is recovered from oil outlets  146   a  and  146   b  of the oil jacket  146  via the above-described pipes  25   b  and  25   c  (see FIG.  6 ). The oil supplied to the bearing portion  142  once enters the oil jacket  146  via an outlet  142   b  of the bearing portion  142 , and is then recovered from the outlets  146   a  and  146   b  of the oil jacket  146  to the oil pan  28  via the above-described pipes  25   b  and  25   c  (see FIG.  6 ). 
     The pipe  25   b  is connected to the oil outlet  146   a , and the pipe  25   c  is connected to the oil outlet  146   b . These oil outlets  146   a  and  146   b  are located at positions higher than an oil level O 1  (see FIG. 6) at the time of stoppage of the engine. 
     A one-way valve  147  is interposed in each of the pipes  25   b  and  25   c  functioning as the oil return passages. 
     Referring to FIG. 10, a water jacket T 3  is formed in a casing of the turbine portion  140 T. A cooling water inlet T 4  of the water jacket T 3  is connected to the cooling water takeoff portion  30   a  (see FIG. 7) of the above-described jet pump  30  via a pipe  148   a  functioning as a supercharger cooling water passage provided independently from the other cooling water passages. A cooling water outlet (not shown) of the water jacket T 3  is connected to the water jacket of the exhaust pipe  27   a  (see FIGS. 1 and 2) via a pipe  148   b  shown in FIG.  7 . 
     Accordingly, cooling water from the jet pump  30  is supplied to the water jacket T 3  of the turbo charger  140  directly not by way of another cooling object, to cool the turbo charger  140 . The water is then used to cool the exhaust pipe  27   a . In addition, the water used for cooling the exhaust pipe  27   a  flows in the water jacket of the anti-counterflow chamber  27   b  to cool the anti-couterflow chamber  27   b , and is jetted in the water muffler  27   c  and is discharged via the exhaust/drainage pipe  27   d , together with exhaust gas, in water stream generated by the jet pump  30 . 
     The personal watercraft on which an engine with a supercharger is mounted, which is configured as described above, has the following functions and effects. 
     (a) The engine  20  for driving the jet propelling pump  30  is provided in the watercraft body  11  formed by the hull  14  and the deck  15  in such a manner as to extend in a length direction of the watercraft body  11 , and the supercharger  140  is provided in a longitudinal direction of the engine  20 , and the supercharger  140  and an end portion of the main gallery  20   a  of oil provided in parallel to the crankshaft  21  of the engine  20  are communicated to each other via the oil supply passage  25   a . As a result, oil is supplied from the end portion of the main gallery  20   a  to the supercharger  140  directly via the oil supply passage  25   a.    
     Accordingly, it is possible to shorten a time required to supply oil to the supercharger  140  after start of the engine, and thus ensure a speedy, positive operation of the supercharger  140 . 
     In the related art, a plug is required to close one end portion of the main gallery (see reference numeral  2   p  in FIG.  13 ). By contrast, according to the personal watercraft on which an engine with a supercharger is mounted according to this embodiment, the plug can be eliminated. 
     (b) The oil pump  80  is provided on a portion, on the front side of the watercraft body  11 , of the engine  20  and the supercharger  140  is provided on a portion, on the rear side of the watercraft body  11 , of the engine  20 , and the supercharger  140  and a rear end portion of the main gallery  20   a  communicate with each other via the oil supply passage  25   a . As a result, it is possible to readily supply oil to the supercharger  140  disposed on the rear side of the engine. 
     (c) Oil supplied to the supercharger  140  is used for lubricating the bearing portion  142  of the supercharger  140 , and also, oil is supplied to the oil jacket  146  formed in the bearing casing  141  for cooling the bearing casing  141 . As a result, it is possible to use the oil supplied to the supercharger  140  not only for lubricating the bearing portion  142  of the supercharger  140 , but also for cooling the bearing casing  141 . 
     In the case of lubricating the bearing portion  142  of the supercharger  140  and cooling the bearing casing  141  by using the oil supplied to the supercharger  140 , a large of oil must be readily supplied, as compared with the related art personal watercraft. However, according to the personal watercraft  10  on which an engine with a supercharger is mounted according to this embodiment, since oil is supplied from the end portion of the main gallery  20   a  to the supercharger  140  directly via the oil supply passage  25   a , the required large amount of oil can be readily supplied. 
     (d) The oil outlets  146   a  and  146   b  in the supercharger  140  are disposed at positions higher than the oil level O 1  at the time of stoppage of the engine. As a result, when the operation of the engine  20  is stopped (the operation of the oil pump  80  is stopped), oil in the supercharger  140  is readily discharged via the oil outlets  146   a  and  146   b.    
     If oil remains in the supercharge  140  at a high temperature immediately after the engine  20  is stopped, then the remaining oil is likely to be carbonized. If this occurs, the entire oil circulating in the engine  20  is likely to deteriorate. However, according to the personal watercraft  10  of the present invention, in which an engine with a supercharger is mounted, since oil in the supercharger  140  is readily discharged via the oil outlets  146   a  and  146   b  when the engine  20  is stopped, the amount of oil remaining in the supercharger  140  after the engine  20  is stopped is made as small as possible. This reduces the deterioration of the entire oil circulating in the engine  20 . 
     (e) The engine  20  is a dry sump engine, and the oil tank  50  is provided on an extension of the crankshaft of the engine  20 . As a result, it is possible to lower the oil level O 1  at the time of stoppage of the engine. 
     Accordingly, it is possible to more readily discharge oil in the supercharger  140  from the oil outlets  146   a  and  146   b , and thus more effectively reduce the deterioration of the entire oil circulating in the engine  20 . 
     (f) The one-way valve  147  is interposed in the oil return passages  25   b  and  25   c  communicated to the oil outlets  146   a  and  146   b  in the supercharger  140 . As a result, it is possible to eliminate the problem, that when the personal watercraft  10  is turned over, oil counter flows, and remains in the supercharger  140  at a high temperature. 
     Accordingly, the carbonization of oil is more likely to be prevented. Hence, the deterioration of the entire oil circulating in the engine  20  can be reduced. 
     (g) In the personal watercraft on which an engine with a supercharger is mounted, cooling water from the pump  30  is supplied to the supercharger  140  via the supercharger cooling water passage  148   a  provided independently from the other cooling water passages. As a result, it is possible to efficiently, sufficiently cool the supercharger  140 . 
     (h) The cooling water from the supercharger cooling water passage  148   a  is first supplied to the supercharger  140  to cool the supercharger  140 , and the cooling water is then supplied to the exhaust system (exhaust pipe  27   a , anti-counterflow chamber  27   b , water muffler  27   c , and exhaust/drainage pipe  27   d ) provided on the downstream from the supercharger  140  via the exhaust system of the engine  20 . As a result, the cooling water used to cool the supercharger  140  is kept at the lowest possible temperature. 
     Thus, cooling of the supercharger  140  is accomplished efficiently and sufficiently. Further, the exhaust system disposed on the downstream side from the supercharger  140  can be cooled also. 
     (k) The cooling water, which has been used for cooling the supercharger  140 , is supplied to the exhaust pipe  27   a  provided on the downstream side from the supercharger  140  in the exhaust system, and is then discharged, together with exhaust gas, outwardly from the watercraft  10 . As a result, it is possible to further cool the exhaust gas, which has been used for driving the supercharger  140 , in the exhaust pipe  27   a.    
     To be more specific, since an exhaust gas is synergistically reduced by cooling the exhaust gas in the supercharger  140  and the exhaust pipe  27   a , it is possible to reduce exhaust noise. 
     (l) Since the oil supplied to the supercharger  140  is used for lubricating the bearing portion  142  of the supercharger  140  and further the oil is supplied to the oil jacket  146  formed in the bearing casing  141  to cool the bearing casing  141 , it is possible to more desirably cool the supercharger  140 . 
     (m) The hull  14  and the deck  15  of the personal watercraft are water-tightly formed and the opening portion  15   a  of the deck  15  is closed with the lid member (seat)  12  to form the space  16  in the watercraft body. The intake ducts  18  and  19  for introducing atmospheric air outside the watercraft body are provided in the space  16 , and the engine  20  and the turbo charger  140  connected to the exhaust manifold  24  of the engine  20  are provided in the space  16 . The turbo charger  140  is located at a position higher than those of the openings  18   a  and  19   a  of the intake ducts  18  and  19 . As a result, in the case of introducing atmospheric air outside the watercraft body in the space  16  via the intake ducts  18  and  19  during running of the personal watercraft, even if water (in the form of splash) permeating the space  16 , it is possible to reduce the likelihood that water will be directly splashed to the turbo charger  140 . 
     Accordingly, it is possible to reduce the likelihood that the casing and the like of the turbo charger  140  kept at a high temperature is rapidly and partially cooled to thereby cause thermal fatigue of the turbo charger  140 . This feature improves the durability of the turbo charger  140 . 
     (n) In the turbo charger  140 , the water jacket T 3  is formed in the casing of the turbine portion  140 T and the oil jacket  146  is formed in the bearing casing  141 , wherein cooling water is supplied to the water jacket T 3  and cooling oil is supplied to the oil jacket  146 . As a result, it is possible to prevent the turbo charger  140  from being excessively heated at a high temperature. 
     Accordingly, even when atmospheric air is introduced from outside the watercraft body into the space  16  via the intake ducts  18  and  19  during running of the personal watercraft, and water (in the form of splash) permeating the space  16  directly reaches the turbo charger  140 , it is possible to reduce temperature change in the casing of the turbo charger  140 . 
     As a result, it is possible to reduce the likelihood that there occurs thermal fatigue of the turbo charger  140 , and hence to certainly improve the durability of the turbo charger  140 . 
     (o) Since cooling water is supplied to the water jacket T 3  via the turbo charger cooling water passage  148   a  provided independently from the other cooling water passages, it is possible to efficiently cool the turbo charge  140 . 
     Accordingly, even atmospheric air is introduced from outside the watercraft body into the space  16  via the intake ducts  18  and  19  during running of the personal watercraft, and water (in the form of splash) permeating the space  16  directly reaches the turbo charger  140 , it is possible to further reduce temperature change in the casing of the turbo charger  140 . 
     As a result, it is possible to further reduce the likelihood that thermal fatigue of the turbo charger  140  will occur, and hence to more certainly improve the durability of the turbo charger  140 . 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.