Patent Publication Number: US-2023151763-A1

Title: Outboard motor, internal combustion engine, and marine vessel

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Japanese Patent Application No. 2021-186428, filed Nov. 16, 2021, which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an outboard motor, an internal combustion engine, and a marine vessel. 
     2. Description of the Related Art 
     Blow-by gas generated in an internal combustion engine of an outboard motor entrains oil mist in a crank chamber of the internal combustion engine. The blow-by gas is once introduced into a breather chamber having a gas-liquid separation function to separate the oil, and then is fed into an intake port of the internal combustion engine to be combusted. Usually, the blow-by gas is introduced into the breather chamber via one blow-by gas flow path provided in a cylinder block (see, e.g., Japanese Patent No. 3537554). 
     In recent years, a marine vessel is required to more quickly reach a destination, and an increase in the output of the outboard motor therefor has been studied. When the output increases, for example, a combustion pressure increases to cause the blow-by gas to increase in the internal combustion engine, such that the amount of the oil taken out from the crank chamber by the blow-by gas also increases. Therefore, the breather chamber for separating the oil from the blow-by gas also needs to be enlarged. 
     However, the entire surface of the internal combustion engine of the outboard motor is covered with a cowl, and there is not much room in the layout thereof, which limits the size of the breather chamber. Therefore, the amount of the oil that can be separated from the blow-by gas in the breather chamber is also limited. Therefore, it is necessary to reduce the amount of the oil contained in the blow-by gas reaching the breather chamber as much as possible. 
     SUMMARY OF THE INVENTION 
     Preferred embodiments of the present invention reduce an amount of oil in blow-by gas reaching a breather chamber. 
     According to a preferred embodiment of the present invention, an outboard motor to be attached to a hull of a marine vessel includes an internal combustion engine including a cylinder block including at least one cylinder, wherein the cylinder block includes two blow-by gas flow paths to guide blow-by gas from a crank chamber to a breather chamber, and the internal combustion engine is oriented such that a crankshaft extends along a direction perpendicular or substantially perpendicular to a bottom of the hull when the marine vessel is sailing. Further, according to another preferred embodiment of the present invention, an internal combustion engine to be attached to a hull of a marine vessel includes a cylinder block including at least one cylinder, wherein the cylinder block includes two blow-by gas flow paths to guide blow-by gas from a crank chamber to a breather chamber. 
     According to the above configuration, the cylinder block includes the two blow-by gas flow paths such that a total cross-sectional area of the blow-by gas flow paths is increased. As a result, a flow velocity of the blow-by gas flowing through each of the blow-by gas flow paths is reduced, and a period of time for the blow-by gas to reach the breather chamber from the crank chamber is increased. That is, a period of time to separate the oil from the blow-by gas in each of the blow-by gas flow paths is sufficiently secured. As a result, an amount of the oil in the blow-by gas reaching the breather chamber is reduced. 
     The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a side view of a marine vessel to which an outboard motor according to a preferred embodiment of the present invention is applied. 
         FIG.  2    is a side view schematically showing a configuration of the outboard motor according to a preferred embodiment of the present invention. 
         FIG.  3    is a side view schematically showing a configuration of an engine. 
         FIG.  4    is a side view of a cylinder block as viewed from an exhaust side. 
         FIG.  5    is a side view of the cylinder block as viewed from an intake side. 
         FIG.  6    is a front view of the cylinder block as viewed from an oil pan side. 
         FIG.  7    is a plan view of the cylinder block as viewed from a cylinder head side. 
         FIG.  8    is a bottom view of the cylinder block as viewed from a crankcase side. 
         FIG.  9    is a horizontal cross-sectional view for explaining an arrangement of blow-by gas flow paths provided on the intake side of the cylinder block. 
         FIG.  10    is a horizontal cross-sectional view for explaining an arrangement of blow-by gas flow paths provided on the exhaust side of the cylinder block. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.  FIG.  1    is a side view of a marine vessel  10  to which an outboard motor  12  according to a preferred embodiment of the present invention is applied, and  FIG.  2    is a side view schematically showing the configuration of the outboard motor  12  according to a preferred embodiment of the present invention. 
     The marine vessel  10  is a planing boat, and includes a hull  11  and at least one, e.g., two outboard motors  12  as a propulsion device attached to the stern of the hull  11 . A cabin  13  also functioning as a cockpit is provided in the hull  11 . The outboard motor  12  includes an internal combustion engine  14 , a propeller  15 , a propeller shaft  16  to rotate the propeller  15 , and a drive shaft  17  to transmit the driving force of the engine  14  to the propeller shaft  16 . The outboard motor  12  applies a thrust to the marine vessel  10  by the propeller  15  being rotated by the driving force of the engine  14 . 
     The outboard motor  12  includes a steering mechanism (not shown). The steering mechanism adjusts the direction of action of the thrust generated by the outboard motor  12  by swinging the outboard motor  12  horizontally or substantially horizontally with respect to the hull  11 . The outboard motor  12  further includes a suspension mechanism  18  to attach the outboard motor  12  to the stern of the hull  11 . The suspension mechanism  18  functions as a lifting mechanism for the outboard motor  12 , and tilts up the outboard motor  12  when the marine vessel  10  is stored. 
     A large amount of water droplets are sprayed on the outboard motor  12 . The outboard motor  12  includes a cowl  19  that covers the entire surface of the engine  14  so that each component of the engine  14  is not corroded by salt water or the like. The cowl  19  covers the propeller shaft  16  and the drive shaft  17  in addition to the engine  14 . 
     In the outboard motor  12 , the engine  14  is oriented such that the axial direction of the drive shaft  17  or a crankshaft  28  to be described below is perpendicular or substantially perpendicular to the bottom of the hull  11  when the marine vessel  10  is sailing. 
       FIG.  3    is a side view schematically showing the configuration of the engine  14 . In  FIG.  3   , the engine  14  includes a cylinder block  20 , a cylinder head  21 , a crankcase  22 , an oil pan  23 , and a breather chamber  24 , as main components. 
     Note that a vertical direction in  FIG.  3    is a direction perpendicular or substantially perpendicular to the bottom of the hull  11  of the marine vessel  10 . The vertical direction is, for example, a direction perpendicular or substantially perpendicular to flat land when the marine vessel  10  is on land, and is also a direction perpendicular or substantially perpendicular to a water surface when the marine vessel  10  is stopped and floating on the water surface. In the drawings of the present preferred embodiment, hereinafter, a direction from the stern of hull  11  toward the bow thereof (that is, the traveling direction of the marine vessel  10 ) is represented by “+X”, a direction from the starboard side of the hull  11  toward the port side thereof is represented by “+Y”, and a direction from the bottom of the hull  11  (outboard motor  12 ) toward the top thereof is represented by “+Z”. The port side (the front side in  FIG.  3   ) (+Y side) of the hull  11  is referred to as an exhaust side, and the starboard side (the side opposite to the front side in  FIG.  3   ) (−Y side) of the hull  11  is referred to as an intake side. 
     The cylinder block  20  includes a plurality of, for example, four cylinders  25  arranged on a straight line, wherein a piston  26  is inserted into each of the cylinders  25 . Each of the pistons  26  is connected to a crankshaft  28  by a connecting rod  27 . The cylinder head  21  includes combustion chambers (not shown) corresponding to each of the cylinders  25  of the cylinder block  20 , and is fastened to the cylinder block  20  such that each of the combustion chambers faces each of the cylinders  25 . The crankcase  22  is fastened to the cylinder block  20  so as to face the cylinder head  21  with the cylinder block  20  interposed therebetween. The crankcase  22  and the cylinder block  20  sandwich the crankshaft  28  therebetween, and further define a crank chamber  29  accommodating the crankshaft  28 . One end of the crankshaft  28  is connected to the drive shaft  17 . The crankshaft  28  is pivotally supported by a journal bearing (not shown) provided in the cylinder block  20  and the crankcase  22  so as to be coaxial with the drive shaft  17 . 
     The oil pan  23  covers the lower surfaces of the cylinder block  20  and the crankcase  22 , and stores lubricating oil therein. The inside of the oil pan  23  communicates with the crank chamber  29 . The oil in the oil pan  23  is pressure-fed to each component of the engine  14  by an oil pump (not shown) via a strainer (not shown), and lubricates mainly sliding components. The oil used to lubricate each of the components is discharged to, for example, the crank chamber  29  and then falls to the oil pan  23 . At this time, a portion of the oil in the oil pan  23  floats in a mist state. The breather chamber  24  is attached to the cylinder block  20 . However, the breather chamber  24  may be integral with the cylinder block  20  instead. 
     The engine  14  causes the crankshaft  28  to convert the moving force of each of the pistons  26  due to the pressure of combustion generated in the combustion chamber of the cylinder head  21  into a rotational force, and transmits the rotational force to the drive shaft  17 . In the engine  14 , as described above, the crank chamber  29  communicates with the inside of the oil pan  23 . Therefore, blow-by gas that has passed through the gap between the piston  26  and the wall surface of the cylinder  25  from the combustion chamber and entered the crank chamber  29  further enters the oil pan  23 . The blow-by gas entrains mist oil floating inside the oil pan  23 . The blow-by gas entraining the oil is introduced into the breather chamber  24  through two blow-by gas flow paths  30  and  31  described below. 
     Next, the two blow-by gas flow paths  30  and  31  included in the cylinder block  20  in the present preferred embodiment will be described. Regarding a viewed angle of the cylinder block  20 , its front view is defined by  FIG.  6   .  FIG.  4    is a side view of the cylinder block  20  as viewed from an exhaust side, and  FIG.  5    is a side view of the cylinder block  20  as viewed from an intake side.  FIG.  6    is a front view of the cylinder block  20  as viewed from an oil pan  23  side,  FIG.  7    is a plan view of the cylinder block  20  as viewed from a cylinder head  21  side, and  FIG.  8    is a bottom view of the cylinder block  20  as viewed from a crankcase  22  side.  FIG.  9    is a horizontal cross-sectional view for explaining the arrangement of the blow-by gas flow path  30  on the intake side of the cylinder block  20 , and  FIG.  10    is a horizontal cross-sectional view for explaining the arrangement of the blow-by gas flow path  31  on the exhaust side of the cylinder block  20 . 
     The cylinder block  20  includes the two blow-by gas flow paths  30  and  31 . The cylinder block  20  is manufactured by a die casting method using aluminum, for example. The shape of each of the blow-by gas flow paths  30  and  31  is mainly formed by a die casting mold. 
     The blow-by gas flow path  30  is on the intake side of the cylinder block  20 , and the blow-by gas flow path  31  is on the exhaust side of the cylinder block  20 . The blow-by gas flow path  30  and the blow-by gas flow path  31  sandwich the plurality of cylinders  25  therebetween. 
     Each of the blow-by gas flow paths  30  and  31  extends along the arrangement direction (hereinafter, referred to as a “cylinder arrangement direction”) of the plurality of cylinders  25  oriented along a single straight line in the cylinder block  20 . The cylinder arrangement direction is parallel or substantially parallel to a Z direction in the drawing. The cylinder arrangement direction is also parallel or substantially parallel to the axial direction of the crankshaft  28 , that is, the blow-by gas flow paths  30  and  31  extend parallel or substantially parallel to the axial direction of the crankshaft  28 . 
     As shown in  FIG.  9   , the length Lo of the blow-by gas flow path  30  along the cylinder arrangement direction is greater than a length L C  of the front end to the rear end of two cylinders  25  in the cylinder arrangement direction. As shown in  FIG.  10   , the blow-by gas flow path  31  penetrates the cylinder block  20  in the Z direction in the drawing. That is, the length Li of the blow-by gas flow path  31  is greater than a length L D  of the front end to the rear end of four cylinders  25  in the cylinder arrangement direction. In other words, the height of the blow-by gas flow path  30  is twice or more than the diameter of a cylinder  25 , and the height of the blow-by gas flow path  31  is four times or more than the diameter of a cylinder  25 . In the present preferred embodiment, the length Lo of the blow-by gas flow path  30  is shorter than the length Li of the blow-by gas flow path  31 . However, the length Lo and the length Li may be equal or substantially equal to each other. The Z direction in the drawing is the vertical direction of the hull  11 , that is, the extending direction of the blow-by gas flow paths  30  and  31  coincides with the direction of gravity. 
     One end of each of the blow-by gas flow paths  30  and  31  is open to the attachment surface for the oil pan  23  in the cylinder block  20  (the front surface of the cylinder block  20 ) ( FIG.  6   ). As a result, the blow-by gas inside the oil pan  23  efficiently flows into the blow-by gas flow paths  30  and  31 . 
     The other end of the blow-by gas flow path  30  is open to the attachment surface (the upper surface of the cylinder block  20 ) for the cylinder head  21  in the cylinder block  20  ( FIG.  7   ). The blow-by gas flowing through the blow-by gas flow path  30  flows into a blow-by gas flow path (not shown) provided in the cylinder block  20  from an opening in the upper surface of the cylinder block  20 , and then flows into the breather chamber  24 . The other end of the blow-by gas flow path  31  is open to the surface of the cylinder block  20  opposite to the attachment surface for the oil pan  23  (the back surface of the cylinder block  20 ). The blow-by gas flowing through the blow-by gas flow path  31  flows into the breather chamber  24  from the opening in the back surface of the cylinder block  20  through a pipe or the like (not shown). 
     It takes a period of time for the blow-by gas which has flowed into the blow-by gas flow paths  30  and  31  to flow into the breather chamber  24 , to some extent. On the other hand, the separation of the oil from the blow-by gas proceeds over a period of time. While the blow-by gas flows through the blow-by gas flow paths  30  and  31 , the separation of the oil from the blow-by gas proceeds. That is, the blow-by gas flow paths  30  and  31  secondarily have a gas-liquid separation function. The oil separated from the blow-by gas in the blow-by gas flow paths  30  and  31  falls toward the oil pan  23  in the blow-by gas flow paths  30  and  31 . 
     In a preferred embodiment of the present invention, the cylinder block  20  of the engine  14  includes the two blow-by gas flow paths  30  and  31  such that the total cross-sectional area of the blow-by gas flow paths is increased. As a result, the flow velocity of the blow-by gas flowing through each of the blow-by gas flow paths  30  and  31  is reduced, and a period of time for the blow-by gas to reach the breather chamber  24  from the oil pan  23  is increased. That is, a period of time to separate the oil from the blow-by gas in each of the blow-by gas flow paths  30  and  31  is sufficiently secured. As a result, the amount of the oil in the blow-by gas reaching the breather chamber  24  is reduced. 
     In a preferred embodiment of the present invention, both the blow-by gas flow paths  30  and  31  are arranged to provide only a necessary minimum wall thickness between each of the blow-by gas flow paths and the cylinders  25 . That is, both the blow-by gas flow paths  30  and  31  are close to the cylinders  25 . As a result, it is possible to reduce a cylindrical thick portion (boss) surrounding the blow-by gas flow paths  30  and  31  from sticking out from the outer surface of the cylinder block  20 . In particular, in a preferred embodiment of the present invention, as a result of the blow-by gas flow path  31  being close to the cylinders  25  as much as possible, a portion of the boss  32  surrounding the blow-by gas flow path  31  protrudes into the crank chamber  29  ( FIG.  8   ). As a result, it is possible to prevent the cylinder block  20  from becoming unnecessarily large, which makes it possible to help miniaturize and reduce the weight of the engine  14 , and thus the outboard motor  12 . 
     Furthermore, in a preferred embodiment of the present invention, in order to increase the cross-sectional area of the blow-by gas flow path, the number of the blow-by gas flow paths is increased instead of increasing the cross-sectional area of each blow-by gas flow path. This not only prevents the boss surrounding the blow-by gas flow paths from unnecessarily sticking out from the surface of the cylinder block  20 , but also eliminates the need to increase the cross-sectional area of each of the blow-by gas flow paths so that the degree of freedom in the arrangement of the blow-by gas flow paths increases. As a result, the influence of the increase in the cross-sectional area of the blow-by gas flow path on the shape of the cylinder block  20  is reduced or minimized. 
     As a result of providing both the blow-by gas flow paths  30  and  31  close to the cylinders  25 , each of the blow-by gas flow paths  30  and  31  is close to a water jacket (not shown) for cooling the cylinder  25 . For example, a portion of the boss surrounding the blow-by gas flow path  30  and/or a portion of the boss  32  surrounding the blow-by gas flow path  31  is exposed to the water jacket. As a result, the blow-by gas flowing through each of the blow-by gas flow paths  30  and  31  is efficiently cooled, and the separation of the oil from the blow-by gas in each of the blow-by gas flow paths  30  and  31  is increased. 
     Furthermore, in a preferred embodiment of the present invention, as described above, the height of the blow-by gas flow path  30  is twice or more than the diameter of a cylinder  25 , and the height of the blow-by gas flow path  31  is four times or more than the diameter of a cylinder  25 . In this manner, a sufficient height of the flow path is provided, which makes it possible to provide an increased period of time during which the blow-by gas stays in each of the blow-by gas flow paths  30  and  31 . This makes it possible to further secure a period of time to separate the oil from the blow-by gas in each of the blow-by gas flow paths  30  and  31 . The extending direction of the blow-by gas flow paths  30  and  31  coincides with the direction of gravity such that the separated oil is actively dropped toward the oil pan  23 . As a result, the separation of the oil from the blow-by gas is increased. 
     Although preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described preferred embodiments, and various modifications and changes can be made within the scope of the gist of the present invention. 
     For example, in the above-described preferred embodiments, the blow-by gas flow path  31  penetrates the cylinder block  20  in a straight line in the Z direction. However, a crank shape may be provided in the middle of the blow-by gas flow path  31 . In this case, it can be expected that the resistance of the flow path increases due to the crank shape, and the flow velocity of the blow-by gas flowing through the blow-by gas flow path  31  decreases such that more oil is separated from the blow-by gas. 
     The height (the length) of the blow-by gas flow path  30  is twice or more than the diameter of a cylinder  25 , and the height of the blow-by gas flow path  31  is four times or more than the diameter of a cylinder  25 . However, it is sufficient that the height (the length) of each of the blow-by gas flow paths  30  and  31  is at least once or more the diameter of a cylinder  25 , that is, it is sufficient that the height (the length) is greater than the diameter of a cylinder  25 . This makes it possible to secure a minimum period of time to separate the oil from the blow-by gas in each of the blow-by gas flow paths  30  and  31 . The height (length) of the blow-by gas flow path  30  and the height (length) of the blow-by gas flow path  31  may be equal or substantially equal to each other. 
     Furthermore, the breather chamber  24  is attached to the cylinder block  20  in the engine  14  described above. However, the breather chamber  24  may be attached to the cylinder head  21 . Alternatively, the breather chamber  24  and the cylinder head  21  may be integral. 
     The cylinder block  20  includes the two blow-by gas flow paths  30  and  31 , but may include three or more blow-by gas flow paths. In this case, at least one blow-by gas flow path is provided on each of the exhaust side and the intake side of the cylinder block  20 . 
     In a preferred embodiment of the present invention, the engine  14  is an inline engine in which all four cylinders  25  are arranged along a single straight line. However, the present invention may also be applied to a V-type engine or a horizontally opposed type engine. In this case, the cylinder block of each bank includes at least two blow-by gas flow paths. Preferred embodiments of the present invention may also be applied to a single-cylinder engine. 
     Furthermore, the engine  14  is mounted on the outboard motor  12  in a preferred embodiment of the present invention. However, the present invention may also be applied to an engine of an inboard motor or an inboard/outboard motor. Regardless of the outboard motor, the inboard motor, or the inboard/outboard motor, the axial direction of the crankshaft of the engine does not need to be perpendicular or substantially perpendicular to the bottom of the hull. For example, the axial direction of the crankshaft of the engine may be horizontal or substantially horizontal to the bottom of the hull. 
     While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.