Patent Publication Number: US-6699088-B2

Title: Engine mount structure for personal watercraft

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority under 35 U.S.C. 119 of Japanese Patent Application No. 2001-219324 filed on Jul. 19, 2001, the entire contents thereof being hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an engine mount structure for a personal watercraft. More particularly, the present invention relates to an engine mount structure for a personal watercraft wherein an engine for driving a jet propulsion pump is incorporated in a body having a hull and a deck. 
     2. Description of Background Art 
     Conventionally, a two-cycle engine is incorporated in personal watercraft that are in widespread use. The engine is disposed in such a posture that a cylinder thereof stands substantially upright at the center of the body of the watercraft. 
     In recent years, interest in using a four-cycle engine in a personal watercraft has been increasing because of the benefits of reducing exhaust gas pollution and noise. 
     However, since the four-cycle engine has a greater overall engine height when compared with the two-cycle engine, because of the structure of the cylinder head, even if the cylinder capacity is equal, it is difficult to incorporate the four-cycle engine in a small body of a personal watercraft in such a posture that the cylinder thereof stands substantially upright. 
     Thus, a personal watercraft has already been proposed wherein a 4-cycle engine is incorporated in a body in such a state wherein it is inclined to one side around the crankshaft thereof (the official gazette of Japanese Patent Laid-Open No. Hei 10-252440). 
     SUMMARY AND OBJECTS OF THE INVENTION 
     Usually, an engine has an upper case and a lower case joined along a transverse plane parallel to the crankshaft of the engine. However, in a conventional engine, a mount portion thereof is provided, both at the left and the right thereof, on the lower case. 
     Therefore, there is a problem that, if the engine (particularly a four-cycle engine) is installed in the body in a state wherein it is inclined to one side about the crankshaft thereof, then it is difficult to mount the engine in a well-balanced state in the body, or the mount portion (for example, a mount arm portion) must have an increased size, which uses small and precious space in the body and makes it difficult to arrange parts of ancillary mechanisms or parts for the intake and exhaust systems. 
     An object of the present invention resides in solution of such a problem as described above to provide an engine mount structure for a personal watercraft by which an engine can be incorporated in a well-balanced state in a body and the space in the body can be utilized efficiently. 
     In order to attain the object of the invention described above, an engine mount structure for a personal watercraft is provided wherein an engine for driving a jet propulsion pump is incorporated in the inside of a watercraft body having a hull and a deck, and the engine has an upper case and a lower case which are joined along a transverse plane parallel to a crankshaft of the engine. The engine is mounted in a state wherein the engine is inclined to one side about the crankshaft, and mount portions of the engine that attach to the body are provided at the left and the right of the engine on the upper case and the lower case. 
     To attain another object of the invention, the engine mount structure for a personal watercraft allows the engine to be mounted in an inclined relationship such that an intake port side is positioned on the upper side thereof while an exhaust port side is positioned on the lower side thereof, and the mount portions provided on the intake port side are provided on the lower case while the mount portions on the exhaust port side are provided on the upper case. 
     To attain another object of the invention, the engine mount structure for a personal watercraft is used with an engine provided with a supercharger, and an intercooler connected to the supercharger and a surge tank are connected to the intake port. 
     To attain another object of the invention, the engine mount structure for a personal watercraft is used with an engine having a starter motor for starting the engine attached to the upper case, and the mount portions on the side to which the starter motor is attached are provided on the lower case. 
     With the inventive engine mount structure for a personal watercraft, the engine for driving the jet propulsion pump is incorporated in the watercraft body surrounded by the hull and the deck. The engine has the upper case and the lower case joined along a transverse plane parallel to the crankshaft of the engine and is mounted in a state wherein it is inclined to one side about the crankshaft. Mount portions of the engine that attach to the body are provided at the left and right sides of the engine on the upper case and the lower case, whereby the engine can be incorporated in a well-balanced condition in the body in an attitude inclined to one side about the crankshaft thereof. 
     Further, since the mount portions can be made compact, ancillary mechanisms or parts for the intake and exhaust systems can be disposed utilizing the small and precious intra-body space effectively. 
     Also, with the inventive engine mount structure for a personal watercraft, the engine is mounted in an inclined state such that the intake port side thereof is positioned on the upper side and the exhaust port side thereof is positioned on the lower side. The mount portions on the intake port side are provided on the lower case and the mount portions on the exhaust port side are provided on the upper case, whereby the space above the mount portions on the lower case side is wide and equipments for the intake system or a member can be disposed to make effective use of the space. 
     Particularly where the engine is an engine with a supercharger and the intercooler connected to the supercharger and the surge tank are connected to the intake port of the engine, the intercooler and the surge tank can be accommodated in the wide space above the mount portions on the lower case side. Accordingly, such an engine mount structure is particularly effective where the engine is provided with a supercharger. 
     With the inventive engine mount structure for a personal watercraft, the starter motor for starting the engine is provided on the upper case and the mount portions on the side on which the starter motor is mounted are provided on the lower case. Consequently, the starter motor can be disposed near the engine without interfering with the mount portions, and the engine weight including the starter motor can be concentrated in the proximity of a central portion of the watercraft body, and the cornering performance of the boat can be enhanced. 
     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 elevational view showing an example of a personal watercraft which employs an embodiment of an engine mount structure for a personal watercraft according to the present invention; 
     FIG. 2 is a plan view of the personal watercraft in FIG. 1; 
     FIG. 3 is a partial enlarged sectional view (partly omitted sectional view) taken along line III—III of FIG. 1; 
     FIG. 4 is a partial enlarged sectional view (partly omitted sectional view) taken along line IV—IV of FIG. 1; 
     FIG. 5 is a partial enlarged sectional view (partly omitted sectional view) taken along line V—V of FIG. 1; 
     FIG. 6 is a right side elevational view of the engine; 
     FIG. 7 is a left side elevational view (partial sectional view) of the engine; 
     FIG. 8 is a schematic perspective view of the engine as viewed obliquely from the rear; 
     FIG.  9 ( a ) is a front elevational view of the engine block; and 
     FIG.  9 ( b ) is a bottom plan view of the engine block. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is a schematic side elevational view showing an example of a personal watercraft which employs an embodiment of an engine mount structure for a personal watercraft according to the present invention, FIG. 2 is a plan view of the same, and FIG. 3 is a partial enlarged sectional view (partly omitted sectional view) taken along line III—III of FIG.  1 . 
     As shown in the figures (principally in FIG.  1 ), this personal watercraft  10  is a small vessel of the saddle type, and a driver can sit on a seat  12  on a body  11  and grip a steering handle  13  with a throttle lever to steer the personal watercraft  10 . 
     The body  11  has a floating body structure wherein a hull  14  and a deck  15  are joined together such that a space  16  is formed in the inside thereof. In the space  16 , an engine  20  is mounted on the hull  14  such that a crankshaft  21  (refer to FIG. 6) thereof extends in a longitudinal direction of the body  11 , and a jet pump (jet propulsion pump)  30 , as propulsion means which is driven by the engine  20 , is provided at a rear portion of the hull  14 . 
     Intake ducts  18  and  19  for supplying intake air into the body (space  16 ) are provided on the body  11 . 
     The jet pump  30  has a passage  33  extending from an intake  17  open to the bottom to a jet outlet  31  and a nozzle  32  open to the rear end of the body and an impeller  34  disposed in the passage  33 , and a shaft  35  of the impeller  34  is connected to an output power shaft, which is hereinafter described, of the engine  20  through a coupling  80 . Accordingly, if the impeller  34  is driven by the engine  20 , then water taken in from the intake  17  is jetted from the nozzle  32  through the jet outlet  31  so that the body  11  is propelled. The driving speed of the engine  20 , that is, the propelling force by the jet pump  30 , is controlled by a pivoting operation of a throttle lever  13   a  (refer to FIG. 2) of the steering handle  13  described above. The nozzle  32  is operatively associated with the steering handle  13  by an control wire (not shown) such that it is pivoted by an operation of the steering handle  13 , and the advancing direction can be changed thereby. Reference numeral  40  denotes a fuel tank, and  41  an accommodation chamber. 
     FIGS. 4 and 5 are views principally showing the engine  20 , and FIG. 4 is a partial enlarged sectional view (partly omitted sectional view) taken along line IV—IV of FIG.  1  and FIG. 5 is a partial enlarged sectional view (partly omitted sectional view) taken along line V—V of FIG.  1 . FIG. 6 is a right side elevational view of the engine  20 , FIG. 7 is a left side elevational view (partial sectional view) of the engine  20 , and FIG. 8 is a schematic perspective view of the engine  20  as viewed obliquely from the rear. 
     The engine  20  is a DOHC in-line four-cylinder dry sump four-cycle engine and is disposed such that the crankshaft  21  thereof extends in the forward and rearward direction of the body  11  as shown in FIGS. 1 and 6. Further, as shown in FIG. 4, the engine  20  is mounted in a state of inclination wherein a plane O extending between the top and bottom of the engine through the crankshaft is inclined to one side (in this instance, in the counterclockwise direction) about the crankshaft  21 . 
     As shown in FIGS. 4 and 5, an intake opening (intake port)  20   i  is disposed on the left side of the engine  20  with respect to the advancing direction of the body  11 , and an exhaust opening (exhaust port)  20   o  is disposed on the right side of the engine  20 . A throttle body  22  and a surge tank (intake chamber)  23  are connected to the intake port  20   i , and an intercooler  50  is connected to and disposed just below the surge tank  23 . In FIG. 4, reference numerals  52  and  53  denote each a mounting bracket of the intercooler  50  to the engine  20 . 
     The intercooler  50  includes a case  51  having an intake entrance  51   i  connected to and communicated with a compressor section  71  of a supercharger (turbocharger)  70  disposed directly rearwardly of the engine  20  by a pipe  72  and an exit  51   o  connected to the intake entrance  23   a  of the surge tank  23  described above by a tube  51   c , and a cooling unit  60  which is a heat exchanging unit accommodated in the case  51 . Referring to FIG. 8, reference numerals  91  and  92  denote each a cooling water hose connected to the intercooler  50 . 
     An exhaust manifold  25  is provided for the exhaust port  20   o  of the engine  20  as shown in FIGS. 4 and 5, and an exhaust exit  25   o  (refer to FIG. 8) of the exhaust manifold  25  is connected to a turbine section  73  of the turbocharger  70 . Exhaust gas having rotated a turbine in the turbine section  73  passes through the pipe  74 , a backflow preventing chamber  75  for preventing a backflow of water (admission of water into the turbocharger  70  and so forth) upon capsize, a water muffler  76  and an exhaust-drain pipe  77  and is exhausted into a water stream produced by the jet pump  30 . 
     As shown in FIG. 9, the engine  20  has an upper case  20   m  and a lower case  20   n  which are divided along a divisional plane D. A bearing hole  20   q  for the crankshaft  21  and bearing holes  20 L and  20 R for balancers which are hereinafter described are formed by fastening the cases  20   m  and  20   n  to each other using fastening bolts  20   k . A lowermost face  20   p  of the lower case  20   n  is positioned below head portions  20   k   1  of the fastening bolts  20   k  and presents a joining or mounting face  20   p  for oil pan  28  (refer to FIGS.  5  and  6 ). The mounting face  20   p  for the oil pan  28  is formed in an elongated rectangular frame shape as viewed in bottom plan ((b) of FIG. 9) surrounding and near to the fastening bolts  20   k . An upper face of the oil pan  28  is open so as to conform to the joining face  20   p  of the lower case  20   n.    
     As clearly shown in FIG. 9, and as shown also in FIGS. 4 and 5, four mount portions M 1 , M 2 , M 3  and M 4  of the engine  20  on the body  11  are provided on left and right sides of the engine on the upper case  20   m  and the lower case  20   n . In particular, the front and rear mount portions M 1  and M 2  on the left side with respect to the advancing direction of the body are formed integrally on the lower case  20   n , and the mount portions M 3  and M 4  on the right side with respect to the advancing direction of the body are formed integrally on the upper case  20   m.    
     The mount portions M 1 , M 2 , M 3  and M 4  are fastened to mounting surfaces on mount-receiving portions  14   a  provided on the hull  14  by means of bolts  24  (refer to FIG.  8 ), each with a mount rubber member R interposed therebetween, and the engine  20  is installed in the body  11  thereby. 
     As apparent also from FIG. 4, the engine  20  is attached in an inclined relationship such that the intake port  20   i  side thereof is positioned on the side that faces obliquely upwardly, and the exhaust port  20   o  side thereof is positioned on the side that faces obliquely downwardly. The mount portions M 1  and M 2  on the intake port  20   i  side are provided on the lower case  20   n , and the mount portions M 3  and M 4  on the exhaust port  20   o  side are provided on the upper case  20   m . Above the mount portions M 1  and M 2  on the intake port  20   i  side, the intercooler  50  connected to the supercharger  70  and the surge tank  23  are disposed as described above. Further, as shown in FIG. 5, a starter motor  120  for starting the engine is attached to the upper case  20   m , and the mount portions M 1  and M 2  on the side on which the starter motor  120  is attached are provided on the lower case  20   n.    
     As shown in FIG. 5, a pinion gear  121  of the starter motor is held in meshing engagement with a starter gear  123  with a speed reducing gear  122  interposed therebetween. The starter gear  123  is connected to a balancer driving gear  113  through a one-way clutch  124  as shown in FIG.  6 . The balancer driving gear  113  is disposed on an outer periphery of the one-way clutch  124  and is secured to the rear face of an ACG rotor  110 . 
     As shown in FIG. 5, the balancer driving gear  113  is held in meshing engagement through an idle gear  116  with a balancer gear  115  secured to an end of a balancer  114 R (refer to FIG. 7) disposed in parallel to and to the right of the crankshaft  21  (on the left side in FIG. 5) inside of the engine  20  to drive the balancer  114 R. Simultaneously, since the balancer driving gear  113  is held in direct engagement with a gear  117  secured to an end of another balancer  114 L disposed in parallel to and to the left of the crankshaft  21  (on the right side in FIG. 5) inside of the engine  20 , it drives the balancer  114 L to rotate in a direction reverse to that of the rotation of the balancer  114 R. The left and right balancers  114 L and  114 R are disposed on the left and the right of the crankshaft  21  on the transverse plane D at which the upper case  20   m  and the lower case  20   n  are joined, and are supported for rotation in the bearing holes  20 L and  20 R described hereinabove. 
     The axial line of the starter motor  120  and the axial lines of the balancers  114 L and  114 R are disposed in parallel to each other, and the idle gear  116  of the balancer  114 R is disposed on the opposite side to the starter motor  120  with respect to the crankshaft  21  and is disposed on the opposite side to the starter motor  120  with respect to a cylinders  20   s  (refer to FIG.  4  and (a) of FIG.  9 ). 
     As shown in FIGS. 5 to  7 , an oil tank  50 , an oil pump  80  and an oil cooler  90  are provided integrally with each other on an extension line of the crankshaft  21  at a front portion of the engine  20 . The oil pump  80  and the oil cooler  90  are provided in the oil tank  50 . Further, an oil filter  100  is provided at an upper portion of the oil tank  50 . 
     The oil tank  50  is formed from a tank body  60  joined to the front face of the engine  20  and a cover  70  joined to a front face of the tank body  60 . The ACG rotor  110 , a coupling  111  for driving the oil pump  80 , the balancer driving gear  113 , the balancer gear  115 , the idle gear  116 , the balancer gear  117 , the pinion gear  121  of the starter motor  120 , the speed reducing gear  122 , and the starter gear  123  are covered with a rear portion of the tank body  60 . 
     With the engine mount structure for a personal watercraft having such a configuration as described above, the following operation and effects are achieved. 
     (a) The engine  20  for driving the jet propulsion pump  30  is incorporated in the body  11  surrounded by the hull  14  and the deck  15 , and the engine  20  has the upper case  20   m  and the lower case  20   n  which are joined along the transverse plane D parallel to the crankshaft  21  of the engine  20  and is mounted in a state wherein it is inclined to one side around the crankshaft  21 . The mount portions M 1 , M 2 , M 3  and M 4  of the engine  20  on the body  11  are provided at the left and right sides of the engine on the upper case  20   m  and the lower case  20   n . Therefore, the engine  20  can be incorporated in a well-balanced condition in the body  11  in the state wherein it is inclined to one side about the crankshaft  21  thereof. 
     Further, since the mount portions M 1 , M 2 , M 3  and M 4  can be made compact, ancillary mechanisms (for example, the starter motor  120 ) or parts for the intake and exhaust systems (for example, the throttle body  22 , surge tank  23 , exhaust manifold  24  or the like) can be accommodated utilizing the small and precious intra-body space  16  effectively. 
     (b) Since the engine  20  is mounted in an inclined state such that the intake port  20   i  side thereof is positioned on the upper side and the exhaust port  20   o  side is positioned on the lower side and, the mount portions M 1  and M 2  on the intake port  20   i  side are provided on the lower case  20   n  and the mount portions M 3  and M 4  on the exhaust port  20   o  side are provided on the upper case  20   m , the space above the mount portions M 1  and M 2  on the lower case  20   n  side is wide and equipment for the intake system (such as the surge tank  23  or the oil tank  50 ) or a member (for example, the pipe  92 ) can be accommodated effectively making use of the space. 
     Particularly where the engine  20  is an engine with a supercharger and the intercooler  50  connected to the supercharger  70  and the surge tank  23  are connected to the intake port  20   i  of the engine  20 , as in the present embodiment, the intercooler  50  and the surge tank  23  can be readily accommodated making use of the wide space above the mount portions M 1  and M 2  on the lower case  20   n  side. 
     Accordingly, such an engine mount structure as described above is particularly effective where the engine is provided with a supercharger. 
     (c) Since the starter motor  120  for starting the engine  20  is provided on the upper case  20   m  and the mount portions M 1  and M 2  on the side on which the starter motor  120  is mounted are provided on the lower case  20   n , the starter motor  120  can be disposed close to the engine  20  without interfering with the mount portions M 1  and M 2 . 
     Accordingly, the engine weight including the starter motor  120  can be concentrated in the proximity of a central portion of the body  11 , and the cornering performance of the boat  10  can be optimized. 
     (d) Since the mounting face  20   p  for the oil pan  28  surrounds and is near to the fastening bolts  20   k  for fastening the upper case  20   m  and the lower case  20   n  of the engine  20  to each other, the overall height of the engine  20  can be reduced. 
     In particular, if the mounting face  20   p  for the oil pan  28  is provided on the inner side of the fastening bolts  20   k  as viewed in bottom plan, then the capacity of the oil pan  28  becomes small, but if the mounting face  20   p  is provided on the outer side remotely from the fastening bolts  20   k , then the width of the oil pan  28  is increased, which makes it difficult to make the oil pan  28  conform with the shape of the boat. Further, if the mounting face  20   p  for the oil pan is overlapped with the fastening bolts  20   k  as viewed in bottom plan, then the overall height of the engine becomes greater. 
     In contrast, with the present embodiment, since the mounting face  20   p  for the oil pan surrounds and is near to the fastening bolts  20   k , as viewed in bottom plan, the overall height of the engine  20  can be reduced. And, the oil pan  28  can be provided while ensuring an appropriate capacity of the oil pan in conformity with the bottom of the boat and while ensuring an appropriate clearance from the body. 
     (e) Since the balancers  114 L and  114 R are disposed on the left and the right of the crankshaft  21  on the transverse plane D between the upper case  20   m  and the lower case  20   n , with the engine  20 , the overall height can be reduced even though the balancers  114 L and  114 R are employed. 
     Accordingly, the present engine  20  is suitably incorporated in the boat  10  having a small intra-body space  16  surrounded by the hull  14  and the deck  15 , and also the center of gravity of the boat  10  can be set low. 
     Further, since the balancers  114 L and  114 R are disposed on the left and the right of the crankshaft  21  on the transverse plane D between the upper case  20   m  and the lower case  20   n  and parallel to the crankshaft  21 , the position of the crankshaft  21  can be set relatively low, and the shaft  35  of the jet propulsion pump  30  can be connected on an extension line of the crankshaft  21 . 
     Furthermore, since a space is provided on the opposite sides of the cylinders  20   s  as a result of positioning the left and right balancers  114 L and  114 R on the left and the right of the crankshaft  21  on the plane D, the degree of freedom in arrangement of ancillary mechanisms can be ensured. 
     In particular, the engine  20  for a personal watercraft can be suitably incorporated in the personal watercraft  10 , the center of gravity of the boat  10  can be set low and freedom in arrangement of ancillary mechanisms can be achieved. 
     (f) Since the balancer driving gear  113  for the balancers is provided in a closely contacting relationship on the rear face of the ACG rotor  110  provided at an end portion of the crankshaft  21 , the driving system for the balancers  114 L and  114 R can be made compact, and also the overall length of the engine  20  can be made short. 
     (g) Since the one-way clutch  124  of the engine starting system is provided on the rear portion of the ACG rotor  110  and the balancer driving gear  113  for the balancers is provided on an outer periphery of the one-way clutch  124 , the overall length of the engine  20  can be reduced further by an amount by which the one-way clutch  124  of the starting system and the balancer driving gear  113  for the balancers overlap with each other. 
     (h) Since the oil tank  50  covers the ACG rotor  110 , the balancers  114  (L, R) and the driving chamber of the starter motor  120 , the need for provision of a separate cover is eliminated and the overall length of the engine  20  can be further reduced. In addition, noise is reduced by the sound-absorbing effect of the oil in the oil tank  50 . 
     (i) Since the starter motor  120  and the balancers  114 L and  114 R are disposed in parallel to each other and the idle gear  116  of the balancer  114 R is disposed on the opposite side to the starter motor  120  with respect to the crankshaft  21 , the starter motor  120  and the driving system for the balancers can be disposed in a compact arrangement around the crankshaft. As a result, the center of gravity of the engine  20  can be set low, and also the center of gravity of the entire boat  10  can be set low. 
     (j) Since the idle gear  116  of the balancer  114 R is disposed on the opposite side to the starter motor  120  with respect to the cylinders  20   s  of the engine, the starter motor  120  and the driving system for the balancers can be disposed in a compact arrangement near the vertical axis of the engine. 
     Accordingly, the engine weight including the starter motor  120  and the driving system described above can be concentrated in the proximity of a central portion of the body  11 , and the cornering performance of the boat  10  can be enhanced. 
     While an embodiment of the present invention is described above, the present invention is not limited to the embodiment described above but can be carried out suitably in various forms within the scope of the subject matter of the present invention. 
     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.