Patent Publication Number: US-6702632-B2

Title: Lubrication system for outboard motor shaft coupling

Description:
PRIORITY INFORMATION 
     This application is based on and claims priority to Japanese Patent Application No. 2001-193862, filed on Jun. 27, 2001, the entire contents of which is hereby expressly incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an engine for an outboard motor and more particularly to an improved lubrication system for an outboard motor. 
     2. Description of the Related Art 
     Outboard motors typically have an internal combustion engine that is coupled to a propulsion unit, such as a propeller, for propelling the boat through the water. The internal combustion engine includes one or more pistons reciprocally connected to a crankshaft for rotation during the combustion process. The crankshaft, in turn, is typically spline-coupled to a driveshaft that transmits the engine torque through a bevel-gear transmission and to a propeller shaft which carries the propeller. Thus, the engine output is transmitted from the crankshaft to the driveshaft and ultimately to the propeller. 
     The typical outboard motor utilizes a spline-coupling to connect the male driveshaft spline to the female crankshaft spline. In order to maintain a smooth engagement in the coupling, grease is typically packed into and around the coupling. The coupling is usually re-packed during routine maintenance, which requires the driveshaft to be uncoupled and removed from the crankshaft. Once grease is packed into the coupling, the driveshaft is reconnected to the crankshaft via the spline coupling. During normal use, however, the grease may lose its efficacy and may dry, thus leaving the coupling dry and unlubricated, which can damage the coupling, either because of burning and/or rusting. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention involves an outboard motor comprising an internal combustion engine having a lubrication system for lubricating a coupling between the engine&#39;s crankshaft and a driveshaft of the outboard motor. The engine includes a cylinder bore that defines in part a combustion chamber and a piston that is disposed within the cylinder bore and is connected to the crankshaft. The crankshaft is journaled for rotation at least partially within a crankcase. The driveshaft is coupled to the crankshaft through a spline coupling and is also operatively coupled to a propulsion device. The lubrication system comprises a passageway that extends through the crankshaft and communicates with the crankcase and with an area in which the spline coupling is disposed. Lubricant flows through the passageway from the crankcase to the spline coupling in order to lubricate the coupling. 
     In accordance with another aspect of the present invention, a lubrication system for a coupling between an engine output shaft and a driven shaft is provided. The engine includes a chamber in which at least a portion of the engine output shaft is disposed. The lubrication system comprises a passageway through the output shaft which communicates with the chamber of the engine and with an area in which the coupling is disposed. The passageway is arranged such that lubricant flows through the passageway from the chamber to the coupling. 
     An additional aspect of the present invention involves an outboard motor lubricant delivery system. The lubrication system comprises a passageway that has a first end in fluid communication with a chamber of an engine and a second end in fluid communication with an area to be lubricated. The chamber contains lubricant. The passageway is formed substantially along a longitudinal axis of a crankshaft of the engine. A metering device is provided between the chamber and the area to be lubricated to control the rate of lubricant delivery from the chamber to the area. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features, aspects and advantages of the present invention will now be described with reference to the drawings of preferred embodiments, which embodiments are intended to illustrate and not to limit the present invention. The drawings comprise six figures. 
     FIG. 1 a side sectional elevation view of an outboard motor including a lucubration system constructed in accordance with a preferred embodiment of the invention, showing certain components of the outboard motor broken away and in section. 
     FIG. 2 is a cross-sectional view of an engine of the outboard motor taken along the plane  2 — 2  of FIG.  1 . 
     FIG. 3 is an enlarged side sectional view of the engine of FIG. 1 showing a crankcase chamber of the engine and a spline coupling between a crankshaft of the engine and a driveshaft of the outboard motor. 
     FIG. 4 is an enlarged view of the coupling and the surrounding engine components shown in FIG.  3 . 
     FIG. 5 illustrates a lubricant passageway through the crankshaft with a lubricant flow regulating insert. 
     FIG. 6 is an another lubricant passageway through the crankshaft with a lubricant flow regulating insert in accordance with another preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION 
     With reference to the drawings and initially to FIG. 1, an outboard motor constructed in accordance with an embodiment of the invention is identified generally by the reference numeral  10 . 
     The outboard motor  10  is comprised of a power head, indicated generally by the reference numeral  12 , and a lower unit assembly, indicated generally by the reference numeral  22 . The power head  12  includes an internal combustion engine  14 , which is shown partially in cross-section in FIG.  1 . While embodiments disclosed herein generally reference the use of a four-cycle internal combustion engine, it should be apparent to those of skill in the art that the lubrication system disclosed herein may also be used in engines operating on two-cycle combustion principles. The lubrication system can also be used with engine employed in other applications (e.g., lawn mowers) in which the engine is stood generally upright (i.e., the rotational axis of the engine is upright). 
     The power head  12  is covered primarily by a protective cowling that is comprised of a lower tray portion  16  and an upper main cowling portion  18 . As best seen in FIG. 3, the power head  12  has a lower mating surface  19  configured to seal with an upper mating surface  21  of the lower unit assembly  22 . A sealing member, such as a gasket  23 , may be disposed between the lower mating surface  19  of the power head  12  and the upper mating surface  21  of the lower unit assembly  22 . 
     As illustrated in FIG. 1, the lower unit assembly  22  depends vertically downward from the power head  12  and comprises components for transferring the output of the engine to a propeller  36 . The lower unit assembly  22  includes a driveshaft housing  28  and lower unit housing  30  which may be a unitary construction, or may be separate components as illustrated, and may be formed from lightweight materials, such as an aluminum alloy or the like. The lower unit assembly  22  further includes an upper support plate portion  38  which is integrally connected to a generally tubular portion  40  that depends downwardly from the power head  12  to the lower unit housing  30 . A driveshaft  42 , which is driven by the engine  14 , extends through the tubular portion  40  and has a bevel gear affixed to its lower end which forms a portion of a bevel gear reversing transmission  32 . 
     The outboard motor  10  generates a propulsion thrust which is steerable by the inclusion of a swivel bracket, indicated generally by the reference numeral  20 . This swivel bracket  20  is generally tubular and is affixed to a clamping bracket  26  by a pivot pin  24  for attachment of the outboard motor  10  to a boat transom. The pivot pin permits tilt and trim adjustment of the outboard motor  10  about the pivot pin  24 . The swivel bracket  20  rotatably journals the driveshaft housing  28  for rotation about a generally vertical axis. Once the outboard motor  10  is attached to the boat transom by the clamping bracket  26 , the swivel bracket  20  allows the outboard motor  10  to pivot about a vertically extending axis, and thus, direct the thrust for steering the boat. 
     With continued reference to FIG. 1, and additional reference to FIG. 3, the lower unit assembly  22  includes the driveshaft housing  28  to which is fixed the lower unit housing  30  that contains the bevel gear reversing transmission  32 . The bevel gear transmission  32  can selectively coupled the driveshaft  42  to a propeller shaft  34  that is journaled in the lower unit housing  30 . The control for this bevel gear transmission  32  may be any type of control as is generally known in the art. 
     The lower unit assembly  22  is operatively coupled to the power head  12  through a series of torque-transmitting couplings. The propeller  36  is carried by a propeller shaft  34  that is journaled for rotational movement. The propeller shaft  34  is coupled to the driveshaft  42  by a bevel gear transmission  32 , as previously described. The driveshaft upper end  124  has a male spline coupling  70  that mates with a female spline coupling  66  of the crankshaft lower end  114  (collectively, the spline coupling). This spline coupling facilitates the power transfer from the engine crankshaft  60  to the driveshaft  42 , and eventually, to the propeller  36 . 
     The construction associated with the power head  12  will now be described by particular reference to FIGS. 1 through 3. The power head  12  houses an internal combustion engine  14  comprised of an engine body having three main portions: a cylinder block  46 , a cylinder head  48 , and a crankcase made up of a lower crankcase member  50  and an upper crankcase member  58 . The lower crankcase member  50  and the upper crankcase member  58  join together to define a crankcase chamber  54 . In the illustrated embodiment, the cylinder block  46  and the upper crankcase member  50  are formed as a unitary piece, but they need not be in other embodiments. 
     A crankshaft  60  is rotatably journaled within the crankcase chamber  54  by an upper main bearing  62  that is carried in cooperation by the cylinder block  46  and upper crankcase member  58 . In addition, a lower main bearing  64  is cooperatively carried by the lower crankcase member  50  and journals the lower end of the crankshaft  60 . 
     The cylinder block  46  defines, in the illustrated embodiment, a single horizontally extending cylinder bore  52 . One end of the cylinder bore  52  is open to the crankcase chamber  54 , while the other end is closed by the cylinder head  48 . A piston  72  is supported for reciprocation within the cylinder bore  52 . A sleeve or cylinder liner  44  fits within the cylinder bore  52  to define a cylinder. Rings on the piston  72  act against the cylinder liner  44  to generally seal the spaces on opposite sides of the piston  72  from each other (although some blow-by will occur). A connecting rod  74  connects the piston  72  to a throw of the crankshaft  60  upon which the connecting rod  74  is journaled in a well known manner. The illustrated embodiment shows only a single-cylinder, horizontal engine, but of course, various aspects and features of the lubrication system can be used with engines of various sizes, including a plurality of pistons in various orientations. 
     The cylinder head is formed with a recess proximate the cylinder bore  52  that defines, in part, the combustion chamber  76  of the engine  14 . One or more intake ports and one or more exhaust ports are located at the recess to provide for the ingress of air and the egress of exhaust gases from the combustion chamber  76 . The combustion chamber  76  is further defined by the cylinder and the piston  72 . The combustion chamber  76  thus has a variable volume as the piston  72  reciprocates within the cylinder. 
     Air is delivered to the combustion chamber by an induction system through one or more intake ports, as is generally known in the art. Fuel can be either directly or indirectly delivered to the combustion chamber. In the illustrated embodiment, a carburetor forms the fuel-air charge which is delivered to the combustion chamber through an intake port; however other types of charge formers, such as, for example, fuel injection systems, can also be used. 
     Once the fuel-air charge is delivered to the combustion chamber, a spark plug  68  creates a spark across a spark gap  69 , thus igniting the charge to cause combustion within the combustion chamber  76 . The combustion increases the pressure within the combustion chamber  76  which causes the piston  72  to move away from the cylinder head  48 . The piston  72  is rotatably connected to a crank pin of the crankshaft  60  through a connecting rod  74  and rotates the crankshaft  60  as moves. The momentum of the crankshaft  60  causes the piston to reciprocate in the cylinder between combustions, as well known in the art. 
     The valve operating and lubricating system will now briefly be described by primary reference to FIGS. 1-3. A camshaft  80  is rotatably journaled within the crankcase chamber  54  by suitable bearings formed at its opposite ends. The camshaft  80  is driven at a reduced speed in comparison to that of the crankshaft  60  by a timing mechanism comprising a drive gear  82  that is fixed for rotation with the crankshaft  60  and a driven gear  84  that is fixed for rotation with the camshaft  80 . 
     In the illustrated embodiment, the camshaft  80  is provided with a pair of cam lobes  86 ,  88  for operating an intake valve and an exhaust valve  92 , respectively, through their respective rocker arms  94 . The intake valve is disposed at the intake port on the cylinder head and regulates air flow through the intake port. Similarly, the exhaust valve  92  is disposed at the exhaust port on the cylinder head and regulates gas flow through the exhaust port. 
     A pair of tappets  97  are slidably supported within the cylinder block  46  and follow the cam profile and displace linearly in response to the cam lobes  86 ,  88 . The linear motion of the tappets  97  is communicated through respective push rods  98  to actuate the rocker arms  94 . Each push rod  98  is associated with a respective one of the rocker arms  94  for operating it in a manner well known in the art. Notably, the fuel pump  100  may be driven off of an additional lobe on the camshaft  80 . The camshaft  80  therefore drives both the intake valve  90  and exhaust valve  92  in a well-known manner. 
     After combustion, the exhaust gases are expelled out the exhaust port (with the exhaust valve  92  opened) and through the remainder of the exhaust system to the atmosphere. In the illustrated embodiment, a portion of the exhaust system is formed by the cylinder block  46  and by a portion of the upper support plate portion  38  of the lower unit assembly  22 , as best seen in FIG.  3 . 
     The motion of the power head components such as the piston  72 , connecting rod  74 , crankshaft  60 , camshaft  80 , tappets  96 , and valves  90 ,  92  require a lubricant in order to overcome frictional resistance, thereby maintaining engine efficiency and power output. To this end, small internal combustion engines may rely on an lubricant slinger gear indicated by the reference numeral  102  (FIG.  2 ), which is mounted for rotation proximate to the lubricant level in the lubricant reservoir  56  on a mounting bracket  104 . The lubricant slinger gear  102  meshes with the driven gear  84  and rotates about an axis transverse to the driven gear axis. The lubricant slinger gear is in fluid contact with lubricant in the lubricant reservoir  56  such that as the lubricant slinger gear  102  rotates, the gear  102  throws lubricant around the crankcase chamber  54  such that it contacts the crankshaft  60 , camshaft  80 , and other moving components. With respect to lubricating the crankshaft  60 , the lower crankcase member  50  defines a crankshaft lubrication groove  78  that allows the lubricant to flow therethrough to coat the surface of the crankshaft  60  at this location. 
     With reference to FIGS. 3 and 4, the arrangement of the crankshaft  60 , driveshaft  42 , and their interconnection is illustrated. The crankshaft  60  is journaled for rotation as has been previously described and has a lower end  114  that forms the female spline coupling  66 . The female spline coupling  66  receives the male spline coupling  70  on the driveshaft upper end  124 . As previously described, this coupling is generally packed with grease to maintain adequate lubrication for the interface of the two components. However, during normal use, the grease may dry out, thus leaving the coupling unprotected. To overcome this, a lubricant passageway  126  is provided to deliver crankcase lubricant to the coupling. The lubricant passageway  126  has an upper end opening  128  in communication with the crankcase chamber  54  and a lower end in communication with a space  136  above the spline coupling. Therefore, as the slinger gear  102  splashes lubricant around the crankcase chamber  54 , some lubricant will be deposited within or flow into the lubricant passageway  126 . The lubricant passageway  126  preferably is formed along the axial center of the crankshaft  60  and its opening  128  opens into a space formed between the throws of the crankshaft  60  and adjacent to the crank pin. The lubricant passageway  126 , however, can have other configurations and the opening  128  can be located elsewhere on the crankshaft  60 . The lubricant passageway preferably has a cross-sectional diameter smaller than a cross-sectional diameter of the male spline coupling  70  at the upper end of the driveshaft  42 . 
     In some embodiments, the lubricant is free to flow through the lubricant passageway  126  and directly to the spline coupling; however, in other embodiments it may be preferable to regulate the amount of lubricant delivered to the spline coupling. 
     Ways of regulating the delivery of lubricant include restricting the diameter of the upper end opening  128 , varying the size of the lubricant passageway  126 , or incorporating a flow restrictor. The illustrated embodiment utilizes a lubricant flow restrictor  130  disposed at the end of the lubricant passageway  126 ; however, it could be disposed at other locations, for example, within the passageway  126 . In the illustrated embodiment, the lubricant flow restrictor  130  comprises a porous bronze alloy sintering plug; however, the plug can be made of other materials through which lubricant can drip as well, such as, for example, a synthetic resin. The lubricant flow restrictor  130  can be other types of devices as well that restrict the flow of lubricant to the spline coupling. Such devices include, without limitation, a valve, capillary tube(s), aperture(s), and the like. 
     The lubricant flow restrictor  130  illustrated in FIGS. 3 and 4 is disposed just below the passageway  126  and has a sufficient porosity to permit the lubricant to drip onto the spline coupling. A column of lubricant tends to collect within the passageway  126  above the top surface  132  of the lubricant flow restrictor  130 . The head (pressure) caused by this lubricant column causes the lubricant to drip from a lower surface  134  of the flow restrictor  130  onto the spline coupling. The fluid pressure and permeable flow restrictor  130  thus cooperate to deliver lubricant to the spline coupling in a generally controlled manner. 
     The lower surface  134  of the lubricant flow restrictor  130  is exposed to the open space  136  and the spline coupling. The lubricant will wet both the male spline coupling  70  and the female spline coupling  66  to provide sufficient lubrication. No grease needs to be added. The lubricant will tend to flow downwardly and fill a lubricant collection space  140  that is preferably located below the spline coupling. To ensure a fluid-tight seal around the spline coupling, a first lubricant seal  142  is carried by a seal housing  144  and is disposed above the lubricant collection space  140 . The seal housing  144  further carries a second and third lubricant seal  146 ,  148  to inhibit any lubricant from flowing down the driveshaft  42  and into the lower unit assembly  22 . These additional seals  146 ,  148  are disposed below the lubricant collection space  140 . 
     FIG. 5 shows an enlarged view of the lubricant flow restrictor  130  in which the restrictor  130  is press-fit into the space  136  just below a lower end of the lubricant passageway  126 . The intersection between the lubricant passageway  126  and the space  136  is configured with a sloped sidewall  149  for, among other things, directing the lubricant to contact the entire upper surface  132  of the flow regulator  130 . 
     FIG. 6 illustrates another embodiment of the lubricant flow restrictor  130  and the lubricant passageway  126  wherein a shoulder  150  is formed at the intersection between the lubricant passageway  126  and the lower space  136 . A portion of the top surface  132  of the flow regulator  130  abuts the shoulder  150 . The shoulder  150  provides a positive stop for positioning the flow regulator  130  during insertion into the space  136 . While this illustrated embodiment reduces the effective surface area of the top surface  132  through which lubricant flows, it can be compensated by varying the characteristics of the flow regulator  130 . FIGS. 5 and 6 both illustrate a flow regulator  130  that is frictionally mounted in place within the space  136 ; however, other mounting devices and methods are possible. 
     Thus, a lubrication system delivers sufficient lubricant from the crankcase chamber to the spline coupling between the crankshaft  60  and driveshaft  42 . Accordingly, the driveshaft  42  need not be removed for maintenance purposes in order to repack the spline coupling with grease. In some applications, the spline coupling need not receive grease even when originally assembled. The lubricant system preferably includes the flow restrictor  130  to generally regulate the amount of lubricant delivered to the spline coupling. 
     While the foregoing description has been limited to specific preferred embodiments, it should be appreciated that variations therefrom are anticipated without departing from the full spirit and scope of the present invention. Thus, while the invention has been described herein with reference to certain preferred embodiments, these embodiments have been presented by way of example only, and not to limit the scope of the invention. Other embodiments and changes in form and detail may be made therein by one skilled in the art without departing from the spirit and scope of the invention, including embodiments which do not provide all of the benefits and features set forth herein. Accordingly, the scope of the present invention is intended to be defined only by the claims that follow.