Abstract:
An outboard motor includes an under cover covering a part of an engine, a mount case supporting the engine, and an oil pan provided below the mount case. The under cover has an opening formed at a place opposite to a drain unit provided at a lower portion of the oil pan. The opening can be opened and closed by a drain cover having first and second locks. A release of the first lock is operated to allow the drain cover to be attached and detached to and from the opening with a single motion.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to outboard motors, and more particularly, to outboard motors having a drain cover covering a drain unit provided at a lower portion of an oil pan.  
         BACKGROUND OF THE INVENTION  
         [0002]    An outboard motor with a four-stroke engine generally has an oil pan for retaining lubricating oil. Since lubricating oil in the oil pan needs a periodic change, an oil drain hole is formed in the vicinity of the bottom of the oil pan to allow the lubricating oil to be discharged.  
           [0003]    The oil pan is provided within an extension case located below an engine cover. The drain hole in the oil pan is generally blocked by a drain plug. A change of oil is done with the drain plug removed.  
           [0004]    An outboard drain structure of this kind is disclosed, for example, in Japanese Patent No. 2624636 or in Japanese Patent Laid-Open Publication No. 2001-27110.  
           [0005]    An outboard drain structure disclosed in Japanese Patent No. 2624636 is configured such that a recess is formed in a portion of a metal extension case made from an aluminum alloy, a drain plug faces onto the recess, and a drain cover of C-shaped cross section closes the recess. The drain cover is attached to the extension case with a set screw.  
           [0006]    When draining an oil pan, first, the drain cover is removed from the recess. Then, the drain cover is oriented horizontally, and the proximal portion of the drain cover is hooked on a stopper provided in the recess. At that time, the drain cover opens upward to serve as a gutter. Next, the drain plug is removed from the oil pan to discharge oil outside via the gutter-like drain cover.  
           [0007]    Since the drain structure is configured such that the drain cover is attached to the extension cover with the set screw, it is necessary to screw the drain cover using a tool, resulting in time-taking fastening and removing operations of the drain cover.  
           [0008]    A drain structure disclosed in Japanese Patent Laid-Open Publication No. 2001-27110 is configured such that a drain plug of an oil pan is provided opposite to an opening formed in an engine cover.  
           [0009]    The drain plug in this drain structure is exposed outside and is likely to show a stain of seawater.  
           [0010]    It is thus desired to improve workability when changing oil without exposing a drain plug outside.  
         SUMMARY OF THE INVENTION  
         [0011]    According to the present invention, there is provided an outboard motor, which comprises: an engine supported on a mount case; an oil pan provided below the mount case, having a drain unit at a lower portion thereof, an under cover made from resin, covering a part of the engine, the mount case and the oil pan, the under cover having an opening formed opposite to the drain unit; and a drain cover made from resin for removably covering the opening, the drain cover having two locks to be engaged and disengaged with and from the under cover.  
           [0012]    As described above, the drain cover closes the opening, preventing the drain and the surrounding portion from being exposed. The opening through which the drain unit is exposed is formed in the resin undercover, and the resin drain cover having the locks removably closes the opening. That is, the drain cover can be engaged and disengaged with and from the opening via the locks with a single motion. This eliminates the need for using a set screw or the like to mount the drain cover to the opening of the under cover, enabling single-motion mounting and removal without using an extra tool, and improving workability when changing oil.  
           [0013]    Preferably, the under cover has a side wall and a front wall; and the drain cover comprises a plate member of substantially L-shaped cross section to fit to the opening formed in the side wall and the front wall. When mounting or removing the drain cover to or from the opening, the drain cover which is a plate member of substantially L-shaped cross section can be easily held, facilitating the mounting and removing operations by hand. The two locks are at 90° different locations while the flat drain cover closes the opening, resulting in stable lock.  
           [0014]    The drain cover preferably has a side portion to be substantially flush with the side wall of the under cover and at least two guide plates spaced and set upright on an inner surface of the side portion. The drain cover when covering the drain unit is continuously flush with the under cover, resulting in good appearance. The two guide plates provided on the inner surface of the drain cover serve as a gutter member when draining oil, constituting a guide member when draining oil.  
           [0015]    The drain cover is turned over to turn an inner surface thereof upward, and one of the locks is engaged with the drain unit to hold the drain cover on the drain unit. That is, when discharging oil, all that is needed is to hook a U-shaped lock of the drain cover on the drain unit, so that the drain cover can be used as an oil drain guide member. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    Preferred embodiments of the present invention will be described in detail below, by way of example only, with reference to the accompanying drawings, in which:  
         [0017]    [0017]FIG. 1 is a cutaway view of an outboard motor according to the present invention;  
         [0018]    [0018]FIG. 2 is a perspective view illustrating a state where an opening formed in an under cover is closed by a drain cover;  
         [0019]    [0019]FIG. 3 is a perspective view of the drain cover viewed from the outside;  
         [0020]    [0020]FIG. 4 is a perspective view of the drain cover viewed from the inside;  
         [0021]    [0021]FIG. 5 is a cross-sectional view taken along line  5 - 5  in FIG. 2;  
         [0022]    [0022]FIG. 6 is a cross-sectional view taken along line  6 - 6  in FIG. 2;  
         [0023]    [0023]FIG. 7 is a perspective view illustrating a state where the drain cover is removed from the opening of the under cover;  
         [0024]    [0024]FIG. 8 is a perspective view of the drain cover removed from the opening of the under cover and turned over;  
         [0025]    [0025]FIG. 9 is a perspective view of the drain cover turned over and engaged with a drain unit;  
         [0026]    [0026]FIG. 10 is a cross-sectional view taken along line  10 - 10  in FIG. 9;  
         [0027]    [0027]FIGS. 11A, 11B and  11 C are cross-sectional views illustrating how to remove the drain cover from the opening of the under cover; and  
         [0028]    [0028]FIGS. 12A, 12B and  12 C are cross-sectional views illustrating how to mount the drain cover when discharging oil. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0029]    Referring to FIG. 1, an outboard motor  1  includes a mount case  2  supporting an engine  3 . The engine  3  has a cylinder block  4 , a cylinder head  5  located rearward of the cylinder block  4 , and a cylinder head cover  6  provided rearward of the cylinder head  5 .  
         [0030]    The engine  3  is a multicylinder (four-cylinder in the illustrated example) engine vertically having a plurality of horizontal cylinders  4   a.    
         [0031]    Pistons  4   b  reciprocate within the respective cylinders  4   a.  The cylinder head  5  has combustion chambers  5   a  corresponding to the respective cylinders  4   a.    
         [0032]    Each piston  4   b  is coupled to a crankshaft  7  disposed in a vertical position via a connecting rod  4   c.  A crankcase  14  is provided at the front of the cylinder block  4 . The crankshaft  7  is housed in the crankcase  14  in the vertical position. The crankcase  14  defines a crank chamber  8 .  
         [0033]    The cylinder head  5  and the cylinder head cover  6  form a cam chamber  10  vertically housing a camshaft  9  in parallel with the crankshaft  7 .  
         [0034]    An exhaust manifold  11  communicating with the combustion chambers  5   a  in the cylinder head  5  is connected to an exhaust pipe  12  extending vertically through the mount case  2  in a communicating manner.  
         [0035]    An oil pan  13  is provided below the mount case  2  in a vertically extending manner. A drain unit  30  through which oil is discharged when changing oil is provided at a lower lateral surface of the oil pan  13 .  
         [0036]    The engine  3 , mount case  2  and oil pan  13  are covered by a resin cover. The cover consists of an engine cover  15  covering a main part of the engine  3 , and an under cover  16  covering a lower part of the engine  3  and the oil pan  13 .  
         [0037]    The under cover  16  constitutes a fixed cover body covering the mount case  2  and the oil pan  13 .  
         [0038]    A metal extension case  17  made from an aluminum alloy is connected to the bottom of the under cover  16 . A gear box  18  is provided at the bottom of the extension case  17 .  
         [0039]    An output shaft  7   a  at the lower end of the crankshaft  7  is connected to a drive shaft  19  extending vertically through the under cover  16  and the extension case  17 .  
         [0040]    The drive from the engine  3  rotates a propeller  20  of the outboard motor  1  via the crankshaft  7 , drive shaft  19  and a gear mechanism  18   a  in the gear box  18 .  
         [0041]    An exhaust gas resulting from the operation of the engine  3  is normally discharged into water through the exhaust pipe  12 . However, when the engine  3  has a small exhaust pressure, running at a low speed, an exhaust gas within an exhaust expansion chamber  22  defined by the mount case  2  is discharged through a sub-exhaust pipe  21  to the atmosphere.  
         [0042]    A swivel shaft  23  extends vertically through a swivel case  24  of a stern bracket  25 , supporting the outboard motor  1  in a steerable manner. The stern bracket  25  has a tilt shaft  25   a,  supporting the outboard motor  1  in a tiltable manner with respect to a hull not shown.  
         [0043]    The under cover  16  as a fixed cover body has an opening  27  formed at a position opposite to the drain unit  30  of the oil pan  13 .  
         [0044]    As shown in FIG. 2, the opening  27  has an L-shaped cross section horizontally elongated from a side wall  16   a  to a front wall  16   b  of the under cover  16 , formed by side upper and lower edges  27   a  of the side wall  16   a  and front upper and lower edges  27   b  of the front wall  16   b.  The opening  27  is closed by a drain cover  40  as a cover member. The drain cover  40  is made from synthetic resin, and is removably mounted to the opening  27 .  
         [0045]    In FIG. 2, reference numeral  26  denotes a bracket supporting a lower portion of the swivel case (see FIG. 1) on the extension case  17 .  
         [0046]    The drain cover  40  is shown in detail in FIGS. 3 and 4.  
         [0047]    The drain cover  40  has a cover body  41  of L-shaped cross section for substantially closing the opening  27  shown in FIG. 2. The cover body  41  consists of a side portion  41   a  and a front portion  41   b  bent from the front end. A U-shaped notch  41   c  is formed in a vertically middle and longitudinally rear end portion of the side portion  41   a.  The notch  41   c  is provided with a first lock  42  integrally formed with the side portion  41   a.    
         [0048]    The first lock  42  is made from resin like the drain cover  41 , having elasticity. As shown in FIG. 4, the first lock  42  has a lock release  42   a,  a connected portion  42   b  continuous with the inner end of the U-shaped notch  41   c,  a reinforcing rib  42   e  provided on an inner surface  41   d  of the side portion  41   a  in front of the connected portion  42   b,  and a U-shaped gap  42   c  formed between the lock release  42   a  and the connected portion  42   b.  The lock release  42   a  has an engaging step  42   d  with a clearance therebetween.  
         [0049]    The lock release  42   a  bends toward the connected portion  42   b,  narrowing the gap  42   c,  and elastically deforming toward the front of the opening  27  shown in FIG. 2.  
         [0050]    Two guide plates are provided on the inner surface  41   d  of the side portion  41   a  of the cover body  41 . Specifically, two guide plates  43 ,  43  are provided longitudinally of the side portion  41   a  in such a manner as to be spaced vertically (in the direction of the narrower width of the side portion  41   a ) and set upright in parallel. Front end portions of the two guide plates  43 ,  43  protrude, on the inside of the front portion  41   b,  inward of the opening  27  shown in FIG. 2 to a given height. The amount of protrusion is greater than the height of the front portion  41   b.  The protruding end portions of the guide plates  43 ,  43  are united with a U-shaped second lock  44 . The second lock  44  has a space  44   b.  Proximal portions  44   a,    44   a  of the second lock  44  are integrally connected to the inner surface of the front portion  41   b.    
         [0051]    Now, the mounting of the drain cover  40  to the under cover  16  will be described with reference to FIGS. 5 and 6.  
         [0052]    As shown in FIG. 5, the two guide plates  43 ,  43  set upright on the inner surface of the drain cover  40  and the second lock  44  are housed in the under cover  16  via the opening  27 .  
         [0053]    An edge portion  41   e  of the front portion  41   b  of the cover body  41  engages a ledge  27   c  formed at a front end portion of the opening  27  to be supported thereon. The first lock  42  formed at the rear end of the cover body  41  is located at a rear end portion  27   d  of the opening  27 . The engaging step  42   d  of the lock release  42   a  engages an inner edge portion of the rear end portion  27   d  of the opening  27 . At that time, the lock release  42   a  is elastically deformed in the direction of narrowing the gap  42   c.    
         [0054]    The second lock  44  of the drain cover  40  engages an engaging rib  16   c  formed at the inside of the front wall  16   b  of the under cover  16 .  
         [0055]    As shown in FIG. 6, upper and lower edges  41   f,    41   f  of the cover body  41  engage external surfaces of ledges  27   e,    27   e  formed at the upper and lower edges  27   a,    27   a  of the opening  27  in an abutting manner. The two guide plates  43 ,  43  protrude inward of the opening  27 .  
         [0056]    [0056]FIG. 7 shows the drain cover  40  removed from the opening  27  of the under cover  16 .  
         [0057]    The drain unit  30  provided at a lower side portion of the oil pan  13  consists of a cylindrical outlet pipe  31  of a short length for guiding oil in the oil pan  13  outside when draining it and a drain plug  32  disposed within the outlet pipe  31 . As shown in FIG. 10, the amount of protrusion of the outlet pipe  31  is larger at an upper portion and smaller at a lower portion.  
         [0058]    The opening  27  also has ledges  27   f,    27   f  at rear upper and lower corners of the opening  27  as well as having the ledges  27   c,    27   e,    27   e  at the front portion and the upper and lower portions, respectively.  
         [0059]    [0059]FIG. 8 shows the drain cover  40  turned over after removed from the opening  27  of the under cover  16 .  
         [0060]    The drain cover  40  is removed from the opening  27  as shown by arrow (1) in FIG. 7, and then the drain cover  40  removed is turned over as shown by arrow (2). As a result, as shown in FIG. 8, the inner surface  41   d  of the drain cover  40  is turned upward and the guide plates  43 ,  43  and the U-shaped second lock  44  are turned upward.  
         [0061]    With this state, the drain cover  40  is inserted as shown by arrow (3) such that the second lock  44  surrounds the outlet pipe  31  of the drain unit  30 , thereby to insert the outlet pipe  31  into the space  44   b  in the second lock  44 .  
         [0062]    As shown in FIGS. 9 and 10, the second lock  44  enters the opening  27  and engages the outlet pipe  31  of the drain unit  30 . The drain cover  40  is thus held on the drain unit  30  within the opening  27  with the inner surface  41   d  facing upward. Specifically, as shown in FIG. 10, the second lock  44  is hooked on the top surface of the outlet pipe  31 , and the edge portion  41   e  of the front portion  41   b  of the cover body  41  abuts against the bottom surface of the outlet pipe  31 .  
         [0063]    The side portion  41   a  of the cover body  41  is supported on the lower ledge  27   e  of the opening  27 , and the drain cover  40  is held with the distal end (including the first lock  42 ) of the cover body  41  inclined downward.  
         [0064]    With the drain cover  40  held on the drain unit  30 , the outlet pipe  31  of the drain unit  30  protrudes from the second lock  44  toward the two guide plates  43 ,  43  by a given amount. As shown in FIG. 9, the two guide plates  43 ,  43  are higher at the side of the front portion  41  of the cover body  41  located near the drain unit  30  and lower at the side of the second lock  42 , thereby forming an oil drain guide path  45 .  
         [0065]    As described above, after the drain cover  40  is removed from the opening  27 , the second lock  44  is inserted into the opening  27 , and the second lock  44  is hooked on the outlet pipe  31  of the drain unit  30 , thereby to engage the drain cover  40  with the drain unit  30 . Then, the drain plug  32  is removed to discharge oil in the oil pan  13  through the drain hole for a change.  
         [0066]    The oil discharged through the drain hole runs down the drain guide path  45  of a gutter shape formed by the two guide plates  43 ,  43  of the drain cover  40  to be discharged outside. The discharged oil is thus prevented from spilling laterally by the two guide plates  43 ,  43  and thus prevented from making the area around it dirty. The oil discharged along the drain guide path  45  is received by an oil receiver.  
         [0067]    Now, the method of removing the drain cover  40  mounted to the opening  27  of the under cover  16  will be described with reference to FIGS. 11A, 11B and  11 C.  
         [0068]    As shown in FIG. 11A, first, the lock release  42   a  of the first lock  42  is pressed and deformed toward the gap  42   c  as shown by arrow (4). The deformation causes the engaging step  42   d  to be disengaged from the end portion  27   d  of the opening  27 .  
         [0069]    Next, as shown in FIG. 11B, the first lock  42  is extracted from the opening  27  in the direction of arrow (5) to the outside. At that time, the edge portion  41   e  of the front portion  41   b  of the cover body  41  is disengaged from the ledge  27   c  of the opening  27 . At the same time, the second lock  44  is disengaged from the rib  16   c  of the under cover  16 .  
         [0070]    Finally, as shown in FIG. 11C, the drain cover  40  is detached from the opening  27 .  
         [0071]    The mounting of the drain cover  40  to the opening  27  can be done in the reverse order to that of the above-described operation.  
         [0072]    Now, the method of hooking the drain cover  40  removed from the opening  27  on the drain unit  30  to drain the oil pan  13  will be described with reference to FIGS. 12A, 12B and  12 C.  
         [0073]    First, as shown in FIG. 12A, the drain cover  40  is turned over in position to turn the inner surface  41   d  of the cover body  41  upward, and the second lock  44  is inserted into the opening  27  as shown by arrow (6).  
         [0074]    Then, as shown in FIG. 12B, the space  44   b  in the second lock  44  is opposed to the outlet pipe  31  of the drain unit  30 , and then the side of the first lock  42  of the drain cover  40  is moved downward as shown by arrow (7).  
         [0075]    As a result, as shown in FIG. 12C, the second lock  44  is engaged with the outlet pipe  31  of the drain unit  30 , and the drain cover  40  is hooked and supported on the outlet pipe  31 . Thereafter the drain plug  32  is removed to drain the oil pan  13 .  
         [0076]    Obviously, various minor changes and modifications of the present invention are possible in the light of the above teaching. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.